Merge pull request #1980 from Skgland/atomtable

make AtomTable consurrency safe

.github/workflows/ci.yml

@@ -20,7 +20,7 @@ jobs:
           - { os: macos-11,       rust-version: stable,  shell: bash, target: 'x86_64-apple-darwin' }
           - { os: ubuntu-20.04,   rust-version: stable,  shell: bash, extra: true, target: 'x86_64-unknown-linux-gnu' }
           - { os: ubuntu-20.04,   rust-version: stable,  shell: bash, target: 'i686-unknown-linux-gnu' }
-          - { os: ubuntu-20.04,   rust-version: 1.65,    shell: bash, target: 'x86_64-unknown-linux-gnu'}
+          - { os: ubuntu-20.04,   rust-version: "1.70",    shell: bash, target: 'x86_64-unknown-linux-gnu'}
           - { os: ubuntu-20.04,   rust-version: beta,    shell: bash, target: 'x86_64-unknown-linux-gnu'}
           - { os: ubuntu-20.04,   rust-version: nightly, shell: bash, target: 'x86_64-unknown-linux-gnu'}
     defaults:

Cargo.toml

@@ -10,7 +10,7 @@ license = "BSD-3-Clause"
 keywords = ["prolog", "prolog-interpreter", "prolog-system"]
 categories = ["command-line-utilities"]
 build = "build/main.rs"
-rust-version = "1.63"
+rust-version = "1.70"
 
 [features]
 default = ["ffi", "repl", "hostname", "tls", "http"]
@@ -19,6 +19,7 @@ repl = ["dep:crossterm", "dep:ctrlc", "dep:rustyline"]
 hostname = ["dep:hostname"]
 tls = ["dep:native-tls"]
 http = ["dep:hyper", "dep:reqwest"]
+rust_beta_channel = []
 
 [build-dependencies]
 indexmap = "1.0.2"

build/instructions_template.rs

@@ -590,7 +590,10 @@ enum SystemClauseType {
     UnattributedVar,
     #[strum_discriminants(strum(props(Arity = "4", Name = "$get_db_refs")))]
     GetDBRefs,
-    #[strum_discriminants(strum(props(Arity = "2", Name = "$keysort_with_constant_var_ordering")))]
+    #[strum_discriminants(strum(props(
+        Arity = "2",
+        Name = "$keysort_with_constant_var_ordering"
+    )))]
     KeySortWithConstantVarOrdering,
     REPL(REPLCodePtr),
 }
@@ -847,7 +850,8 @@ fn add_discriminant_data<DiscriminantT>(
     prefix: &'static str,
     variant_data: &mut Vec<(&'static str, Arity, Variant)>,
 ) -> (&'static str, Arity)
-    where DiscriminantT: FromStr + strum::EnumProperty + std::fmt::Debug
+where
+    DiscriminantT: FromStr + strum::EnumProperty + std::fmt::Debug,
 {
     let name = prop_from_ident::<DiscriminantT>(&variant.ident, "Name");
     let arity = Arity::from(prop_from_ident::<DiscriminantT>(&variant.ident, "Arity"));
@@ -2300,7 +2304,8 @@ pub fn generate_instructions_rs() -> TokenStream {
 
     instr_data.generate_instruction_enum_loop(input);
 
-    let instr_variants: Vec<_> = instr_data.instr_variants
+    let instr_variants: Vec<_> = instr_data
+        .instr_variants
         .iter()
         .cloned()
         .map(|(_, _, _, variant)| variant)
@@ -2339,7 +2344,8 @@ pub fn generate_instructions_rs() -> TokenStream {
     for (name, arity, variant) in instr_data.compare_number_variants {
         let ident = variant.ident.clone();
 
-        let variant_fields: Vec<_> = variant.fields
+        let variant_fields: Vec<_> = variant
+            .fields
             .into_iter()
             .map(|field| {
                 let ty = field.ty;
@@ -2382,25 +2388,19 @@ pub fn generate_instructions_rs() -> TokenStream {
             .map(|n| format_ident!("f_{}", n))
             .collect();
 
-        clause_type_to_instr_arms.push(
+        clause_type_to_instr_arms.push(quote! {
-            quote! {
             ClauseType::Inlined(
                 InlinedClauseType::CompareNumber(CompareNumber::#ident(#(#placeholder_ids),*))
             ) => Instruction::#instr_ident(#(*#placeholder_ids),*)
-            }
+        });
-        );
 
-        is_inbuilt_arms.push(
+        is_inbuilt_arms.push(quote! {
-            quote! {
             (atom!(#name), #arity) => true
-            }
+        });
-        );
 
-        is_inlined_arms.push(
+        is_inlined_arms.push(quote! {
-            quote! {
             (atom!(#name), #arity) => true
-            }
+        });
-        );
     }
 
     for (name, arity, variant) in instr_data.compare_term_variants {
@@ -2412,36 +2412,31 @@ pub fn generate_instructions_rs() -> TokenStream {
             )
         });
 
-        clause_type_name_arms.push(
+        clause_type_name_arms.push(quote! {
-            quote! {
             ClauseType::BuiltIn(
                 BuiltInClauseType::CompareTerm(CompareTerm::#ident)
             ) => atom!(#name)
-            }
+        });
-        );
 
         let ident = variant.ident;
         let instr_ident = format_ident!("Call{}", ident);
 
-        clause_type_to_instr_arms.push(
+        clause_type_to_instr_arms.push(quote! {
-            quote! {
             ClauseType::BuiltIn(
                 BuiltInClauseType::CompareTerm(CompareTerm::#ident)
             ) => Instruction::#instr_ident
-            }
+        });
-        );
 
-        is_inbuilt_arms.push(
+        is_inbuilt_arms.push(quote! {
-            quote! {
             (atom!(#name), #arity) => true
-            }
+        });
-        );
     }
 
     for (name, arity, variant) in instr_data.builtin_type_variants {
         let ident = variant.ident.clone();
 
-        let variant_fields: Vec<_> = variant.fields
+        let variant_fields: Vec<_> = variant
+            .fields
             .into_iter()
             .map(|field| {
                 let ty = field.ty;
@@ -2498,17 +2493,16 @@ pub fn generate_instructions_rs() -> TokenStream {
             }
         });
 
-        is_inbuilt_arms.push(
+        is_inbuilt_arms.push(quote! {
-            quote! {
             (atom!(#name), #arity) => true
-            }
+        });
-        );
     }
 
     for (name, arity, variant) in instr_data.inlined_type_variants {
         let ident = variant.ident.clone();
 
-        let variant_fields: Vec<_> = variant.fields
+        let variant_fields: Vec<_> = variant
+            .fields
             .into_iter()
             .map(|field| {
                 if field.ty.type_id() == TypeId::of::<usize>() {
@@ -2555,31 +2549,26 @@ pub fn generate_instructions_rs() -> TokenStream {
             .map(|n| format_ident!("f_{}", n))
             .collect();
 
-        clause_type_to_instr_arms.push(
+        clause_type_to_instr_arms.push(quote! {
-            quote! {
             ClauseType::Inlined(
                 InlinedClauseType::#ident(#(#placeholder_ids),*)
             ) => Instruction::#instr_ident(*#(#placeholder_ids),*)
-            }
+        });
-        );
 
-        is_inbuilt_arms.push(
+        is_inbuilt_arms.push(quote! {
-            quote! {
             (atom!(#name), #arity) => true
-            }
+        });
-        );
 
-        is_inlined_arms.push(
+        is_inlined_arms.push(quote! {
-            quote! {
             (atom!(#name), #arity) => true
-            }
+        });
-        );
     }
 
     for (name, arity, variant) in instr_data.system_clause_type_variants {
         let ident = variant.ident.clone();
 
-        let variant_fields: Vec<_> = variant.fields
+        let variant_fields: Vec<_> = variant
+            .fields
             .into_iter()
             .map(|field| {
                 if field.ty == parse_quote! { usize } {
@@ -2665,8 +2654,7 @@ pub fn generate_instructions_rs() -> TokenStream {
             }
         });
 
-        is_inbuilt_arms.push(
+        is_inbuilt_arms.push(if let Arity::Ident("arity") = &arity {
-            if let Arity::Ident("arity") = &arity {
             quote! {
                 (atom!(#name), _arity) => true
             }
@@ -2674,14 +2662,14 @@ pub fn generate_instructions_rs() -> TokenStream {
             quote! {
                 (atom!(#name), #arity) => true
             }
-            }
+        });
-        );
     }
 
     for (name, arity, variant) in instr_data.repl_code_ptr_variants {
         let ident = variant.ident.clone();
 
-        let variant_fields: Vec<_> = variant.fields
+        let variant_fields: Vec<_> = variant
+            .fields
             .into_iter()
             .map(|field| {
                 if field.ty.type_id() == TypeId::of::<usize>() {
@@ -2742,11 +2730,9 @@ pub fn generate_instructions_rs() -> TokenStream {
             }
         });
 
-        is_inbuilt_arms.push(
+        is_inbuilt_arms.push(quote! {
-            quote! {
             (atom!(#name), #arity) => true
-            }
+        });
-        );
     }
 
     for (name, arity, variant) in instr_data.clause_type_variants {
@@ -2768,7 +2754,8 @@ pub fn generate_instructions_rs() -> TokenStream {
             continue;
         }
 
-        let variant_fields: Vec<_> = variant.fields
+        let variant_fields: Vec<_> = variant
+            .fields
             .into_iter()
             .map(|field| {
                 if field.ty == parse_quote! { usize } {
@@ -2817,14 +2804,13 @@ pub fn generate_instructions_rs() -> TokenStream {
             }
         });
 
-        is_inbuilt_arms.push(
+        is_inbuilt_arms.push(quote! {
-            quote! {
             (atom!(#name), _arity) => true
-            }
+        });
-        );
     }
 
-    let to_execute_arms: Vec<_> = instr_data.instr_variants
+    let to_execute_arms: Vec<_> = instr_data
+        .instr_variants
         .iter()
         .cloned()
         .filter_map(|(_, _, _, variant)| {
@@ -2837,9 +2823,8 @@ pub fn generate_instructions_rs() -> TokenStream {
                 0
             };
 
-            let placeholder_ids: Vec<_> = (0 .. enum_arity)
+            let placeholder_ids: Vec<_> =
-                .map(|n| format_ident!("f_{}", n))
+                (0..enum_arity).map(|n| format_ident!("f_{}", n)).collect();
-                .collect();
 
             if variant_string.starts_with("Call") {
                 let execute_ident = format_ident!("Execute{}", variant_string["Call".len()..]);
@@ -2876,7 +2861,8 @@ pub fn generate_instructions_rs() -> TokenStream {
         })
         .collect();
 
-    let is_execute_arms: Vec<_> = instr_data.instr_variants
+    let is_execute_arms: Vec<_> = instr_data
+        .instr_variants
         .iter()
         .cloned()
         .filter_map(|(_, _, _, variant)| {
@@ -2919,7 +2905,8 @@ pub fn generate_instructions_rs() -> TokenStream {
         })
         .collect();
 
-    let to_default_arms: Vec<_> = instr_data.instr_variants
+    let to_default_arms: Vec<_> = instr_data
+        .instr_variants
         .iter()
         .cloned()
         .filter_map(|(_, _, countable_inference, variant)| {
@@ -2936,9 +2923,8 @@ pub fn generate_instructions_rs() -> TokenStream {
                     0
                 };
 
-                let placeholder_ids: Vec<_> = (0 .. enum_arity)
+                let placeholder_ids: Vec<_> =
-                    .map(|n| format_ident!("f_{}", n))
+                    (0..enum_arity).map(|n| format_ident!("f_{}", n)).collect();
-                    .collect();
 
                 Some(if enum_arity == 0 {
                     quote! {
@@ -2957,7 +2943,8 @@ pub fn generate_instructions_rs() -> TokenStream {
         })
         .collect();
 
-    let control_flow_arms: Vec<_> = instr_data.instr_variants
+    let control_flow_arms: Vec<_> = instr_data
+        .instr_variants
         .iter()
         .cloned()
         .filter_map(|(_, _, _, variant)| {
@@ -2985,7 +2972,8 @@ pub fn generate_instructions_rs() -> TokenStream {
         })
         .collect();
 
-    let instr_macro_arms: Vec<_> = instr_data.instr_variants
+    let instr_macro_arms: Vec<_> = instr_data
+        .instr_variants
         .iter()
         .rev() // produce default, execute & default & execute cases first.
         .cloned()
@@ -2994,7 +2982,7 @@ pub fn generate_instructions_rs() -> TokenStream {
             let variant_string = variant.ident.to_string();
             let arity = match arity {
                 Arity::Static(arity) => arity,
-                _ => 1
+                _ => 1,
             };
 
             Some(if variant_string.starts_with("Execute") {
@@ -3071,7 +3059,8 @@ pub fn generate_instructions_rs() -> TokenStream {
         })
         .collect();
 
-    let name_and_arity_arms: Vec<_> = instr_data.instr_variants
+    let name_and_arity_arms: Vec<_> = instr_data
+        .instr_variants
         .into_iter()
         .map(|(name, arity, _, variant)| {
             let ident = &variant.ident;
@@ -3303,8 +3292,10 @@ pub fn generate_instructions_rs() -> TokenStream {
 fn is_callable(id: &Ident) -> bool {
     let id = id.to_string();
 
-    id.starts_with("Call") || id.starts_with("Execute") || id.starts_with("DefaultCall") ||
+    id.starts_with("Call")
-        id.starts_with("DefaultExecute")
+        || id.starts_with("Execute")
+        || id.starts_with("DefaultCall")
+        || id.starts_with("DefaultExecute")
 }
 
 fn is_non_default_callable(id: &Ident) -> bool {
@@ -3325,7 +3316,8 @@ fn create_instr_variant(id: Ident, mut variant: Variant) -> Variant {
 }
 
 fn prop_from_ident<DiscriminantT>(id: &Ident, key: &'static str) -> &'static str
-   where DiscriminantT: FromStr + strum::EnumProperty + std::fmt::Debug
+where
+    DiscriminantT: FromStr + strum::EnumProperty + std::fmt::Debug,
 {
     let disc = match DiscriminantT::from_str(id.to_string().as_str()) {
         Ok(disc) => disc,
@@ -3345,7 +3337,7 @@ fn prop_from_ident<DiscriminantT>(id: &Ident, key: &'static str) -> &'static str
 #[derive(Clone, Copy)]
 enum Arity {
     Static(usize),
-    Ident(&'static str)
+    Ident(&'static str),
 }
 
 impl From<&'static str> for Arity {
@@ -3437,9 +3429,13 @@ impl InstructionData {
 
             (name, arity, CountableInference::NotCounted)
         } else if id == "InstructionTemplate" {
-            ( prop_from_ident::<InstructionTemplateDiscriminants>(&variant.ident, "Name"),
+            (
-              Arity::from(prop_from_ident::<InstructionTemplateDiscriminants>(&variant.ident, "Arity")),
+                prop_from_ident::<InstructionTemplateDiscriminants>(&variant.ident, "Name"),
-              CountableInference::NotCounted
+                Arity::from(prop_from_ident::<InstructionTemplateDiscriminants>(
+                    &variant.ident,
+                    "Arity",
+                )),
+                CountableInference::NotCounted,
             )
         } else if id == "ClauseType" {
             let (name, arity) = add_discriminant_data::<ClauseTypeDiscriminants>(
@@ -3461,14 +3457,11 @@ impl InstructionData {
             variant.ident.clone()
         };
 
-        let generated_variant = create_instr_variant(
+        let generated_variant =
-            format_ident!("{}{}", prefix, v_ident),
+            create_instr_variant(format_ident!("{}{}", prefix, v_ident), variant.clone());
-            variant.clone(),
-        );
 
-        self.instr_variants.push(
+        self.instr_variants
-            (name, arity, countable_inference, generated_variant)
+            .push((name, arity, countable_inference, generated_variant));
-        );
     }
 
     fn generate_instruction_enum_loop(&mut self, input: syn::DeriveInput) {
@@ -3490,10 +3483,10 @@ impl InstructionData {
                 self.label_variant(&input.ident, "Call", variant.clone());
                 self.label_variant(&input.ident, "Execute", variant.clone());
 
-                if input.ident == "BuiltInClauseType" ||
+                if input.ident == "BuiltInClauseType"
-                    input.ident == "CompareNumber" ||
+                    || input.ident == "CompareNumber"
-                    input.ident == "CompareTerm" ||
+                    || input.ident == "CompareTerm"
-                    input.ident == "ClauseType"
+                    || input.ident == "ClauseType"
                 {
                     self.label_variant(&input.ident, "DefaultCall", variant.clone());
                     self.label_variant(&input.ident, "DefaultExecute", variant);

build/static_string_indexing.rs

@@ -1,7 +1,7 @@
 use proc_macro2::TokenStream;
-use syn::*;
 use syn::parse::*;
 use syn::visit::*;
+use syn::*;
 
 use indexmap::IndexSet;
 
@@ -11,7 +11,9 @@ struct StaticStrVisitor {
 
 impl StaticStrVisitor {
     fn new() -> Self {
-        Self { static_strs: IndexSet::new() }
+        Self {
+            static_strs: IndexSet::new(),
+        }
     }
 }
 

src/arena.rs

@@ -4,12 +4,16 @@ use crate::machine::loader::LiveLoadState;
 use crate::machine::machine_indices::*;
 use crate::machine::streams::*;
 use crate::raw_block::*;
+use crate::rcu::Rcu;
+use crate::rcu::RcuRef;
 use crate::read::*;
 
-use ordered_float::OrderedFloat;
 use crate::parser::dashu::{Integer, Rational};
+use ordered_float::OrderedFloat;
+use tokio::sync::RwLock;
 
 use std::alloc;
+use std::cell::UnsafeCell;
 use std::fmt;
 use std::hash::{Hash, Hasher};
 use std::mem;
@@ -22,7 +26,9 @@ macro_rules! arena_alloc {
     ($e:expr, $arena:expr) => {{
         let result = $e;
         #[allow(unused_unsafe)]
-        unsafe { ArenaAllocated::alloc($arena, result) }
+        unsafe {
+            ArenaAllocated::alloc($arena, result)
+        }
     }};
 }
 
@@ -31,23 +37,35 @@ macro_rules! float_alloc {
     ($e:expr, $arena:expr) => {{
         let result = $e;
         #[allow(unused_unsafe)]
-        unsafe { $arena.f64_tbl.build_with(result) }
+        unsafe {
+            $arena.f64_tbl.build_with(result).as_ptr()
+        }
     }};
 }
 
-#[cfg(test)]
+use std::sync::Arc;
-use std::cell::RefCell;
+use std::sync::Mutex;
+use std::sync::Weak;
 
 const F64_TABLE_INIT_SIZE: usize = 1 << 16;
 const F64_TABLE_ALIGN: usize = 8;
 
-#[cfg(test)]
+#[inline(always)]
-thread_local! {
+fn global_f64table() -> &'static RwLock<Weak<F64Table>> {
-    static F64_TABLE_BUF_BASE: RefCell<*const u8> = RefCell::new(ptr::null_mut());
+    #[cfg(feature = "rust_beta_channel")]
+    {
+        // const Weak::new will be stabilized in 1.73 which is currently in beta,
+        // till then we need a OnceLock for initialization
+        static GLOBAL_ATOM_TABLE: RwLock<Weak<F64Table>> = RwLock::const_new(Weak::new());
+        &GLOBAL_ATOM_TABLE
+    }
+    #[cfg(not(feature = "rust_beta_channel"))]
+    {
+        use std::sync::OnceLock;
+        static GLOBAL_ATOM_TABLE: OnceLock<RwLock<Weak<F64Table>>> = OnceLock::new();
+        GLOBAL_ATOM_TABLE.get_or_init(|| RwLock::new(Weak::new()))
+    }
 }
-
-#[cfg(not(test))]
-static mut F64_TABLE_BUF_BASE: *const u8 = ptr::null_mut();
 
 impl RawBlockTraits for F64Table {
     #[inline]
@@ -63,69 +81,86 @@ impl RawBlockTraits for F64Table {
 
 #[derive(Debug)]
 pub struct F64Table {
-    block: RawBlock<F64Table>,
+    block: Rcu<RawBlock<F64Table>>,
-}
+    update: Mutex<()>,
-
-impl Drop for F64Table {
-    fn drop(&mut self) {
-        self.block.deallocate();
-    }
-}
-
-#[cfg(test)]
-fn set_f64_tbl_buf_base(ptr: *const u8) {
-    F64_TABLE_BUF_BASE.with(|f64_table_buf_base| {
-        *f64_table_buf_base.borrow_mut() = ptr;
-    });
-}
-
-#[cfg(test)]
-pub(crate) fn get_f64_tbl_buf_base() -> *const u8 {
-    F64_TABLE_BUF_BASE.with(|f64_table_buf_base| *f64_table_buf_base.borrow())
-}
-
-#[cfg(not(test))]
-fn set_f64_tbl_buf_base(ptr: *const u8) {
-    unsafe {
-        F64_TABLE_BUF_BASE = ptr;
-    }
-}
-
-#[cfg(not(test))]
-pub(crate) fn get_f64_tbl_buf_base() -> *const u8 {
-    unsafe { F64_TABLE_BUF_BASE }
 }
 
 #[inline(always)]
-pub fn lookup_float(offset: usize) -> *mut OrderedFloat<f64> {
+pub fn lookup_float(
-    let base = get_f64_tbl_buf_base() as usize;
+    offset: F64Offset,
-    (base + offset) as *mut _
+) -> RcuRef<RawBlock<F64Table>, UnsafeCell<OrderedFloat<f64>>> {
+    let f64table = global_f64table()
+        .blocking_read()
+        .upgrade()
+        .expect("We should only be looking up floats while there is a float table");
+
+    RcuRef::try_map(f64table.block.active_epoch(), |raw_block| unsafe {
+        raw_block
+            .base
+            .offset(offset.0 as isize)
+            .cast_mut()
+            .cast::<UnsafeCell<OrderedFloat<f64>>>()
+            .as_ref()
+    })
+    .expect("The offset should result in a non-null pointer")
 }
 
 impl F64Table {
     #[inline]
-    pub fn new() -> Self {
+    pub fn new() -> Arc<Self> {
-        let table = Self { block: RawBlock::new() };
+        let upgraded = global_f64table().blocking_read().upgrade();
-        set_f64_tbl_buf_base(table.block.base);
+        // don't inline upgraded, otherwise temporary will be dropped too late in case of None
-        table
+        if let Some(atom_table) = upgraded {
+            atom_table
+        } else {
+            let mut guard = global_f64table().blocking_write();
+            // try to upgrade again in case we lost the race on the write lock
+            if let Some(atom_table) = guard.upgrade() {
+                atom_table
+            } else {
+                let atom_table = Arc::new(Self {
+                    block: Rcu::new(RawBlock::new()),
+                    update: Mutex::new(()),
+                });
+                *guard = Arc::downgrade(&atom_table);
+                atom_table
+            }
+        }
     }
 
-    pub unsafe fn build_with(&mut self, value: f64) -> F64Ptr {
+    pub unsafe fn build_with(&self, value: f64) -> F64Offset {
+        let update_guard = self.update.lock();
+
+        // we don't have an index table for lookups as AtomTable does so
+        // just get the epoch after we take the upgrade lock
+        let mut block_epoch = self.block.active_epoch();
+
         let mut ptr;
 
         loop {
-            ptr = self.block.alloc(mem::size_of::<f64>());
+            ptr = block_epoch.alloc(mem::size_of::<f64>());
 
             if ptr.is_null() {
-                self.block.grow();
+                let new_block = block_epoch.grow_new().unwrap();
-                set_f64_tbl_buf_base(self.block.base);
+                self.block.replace(new_block);
+                block_epoch = self.block.active_epoch();
             } else {
                 break;
             }
         }
 
         ptr::write(ptr as *mut OrderedFloat<f64>, OrderedFloat(value));
-        F64Ptr(ptr::NonNull::new_unchecked(ptr as *mut _))
+
+        let float = F64Offset {
+            0: ptr as usize - block_epoch.base as usize,
+        };
+
+        // atometable would have to update the index table at this point
+
+        // expicit drop to ensure we don't accidentally drop it early
+        drop(update_guard);
+
+        float
     }
 }
 
@@ -276,7 +311,9 @@ impl<T: ?Sized + ArenaAllocated> TypedArenaPtr<T> {
 
     #[inline]
     pub fn set_tag(&mut self, tag: ArenaHeaderTag) {
-        unsafe { (*self.header_ptr_mut()).set_tag(tag); }
+        unsafe {
+            (*self.header_ptr_mut()).set_tag(tag);
+        }
     }
 
     #[inline]
@@ -334,12 +371,18 @@ pub trait ArenaAllocated: Sized {
     }
 }
 
-#[derive(Copy, Clone, Debug)]
+#[derive(Debug)]
-pub struct F64Ptr(pub ptr::NonNull<OrderedFloat<f64>>);
+pub struct F64Ptr(RcuRef<RawBlock<F64Table>, UnsafeCell<OrderedFloat<f64>>>);
+
+impl Clone for F64Ptr {
+    fn clone(&self) -> Self {
+        Self(RcuRef::clone(&self.0))
+    }
+}
 
 impl PartialEq for F64Ptr {
     fn eq(&self, other: &F64Ptr) -> bool {
-        self.0 == other.0 || &**self == &**other
+        RcuRef::ptr_eq(&self.0, &other.0) || self.deref() == other.deref()
     }
 }
 
@@ -375,28 +418,26 @@ impl Deref for F64Ptr {
 
     #[inline]
     fn deref(&self) -> &Self::Target {
-        unsafe { &*self.0.as_ptr() }
+        unsafe { &*self.0.get().as_ref().unwrap() }
     }
 }
 
 impl DerefMut for F64Ptr {
     #[inline]
     fn deref_mut(&mut self) -> &mut Self::Target {
-        unsafe { &mut *self.0.as_ptr() }
+        unsafe { &mut *self.0.get().as_mut().unwrap() }
     }
 }
 
 impl F64Ptr {
     #[inline(always)]
-    pub fn from_offset(offset: usize) -> Self {
+    pub fn from_offset(offset: F64Offset) -> Self {
-        unsafe {
+        Self(lookup_float(offset))
-            F64Ptr(ptr::NonNull::new_unchecked(lookup_float(offset)))
-        }
     }
 
     #[inline(always)]
     pub fn as_offset(&self) -> F64Offset {
-        F64Offset(self.0.as_ptr() as usize - get_f64_tbl_buf_base() as usize)
+        F64Offset(self.0.get() as usize - RcuRef::get_root(&self.0).base as usize)
     }
 }
 
@@ -416,7 +457,7 @@ impl F64Offset {
 
     #[inline(always)]
     pub fn as_ptr(self) -> F64Ptr {
-        F64Ptr::from_offset(self.0)
+        F64Ptr::from_offset(self)
     }
 
     #[inline(always)]
@@ -672,7 +713,7 @@ struct AllocSlab {
 #[derive(Debug)]
 pub struct Arena {
     base: *mut AllocSlab,
-    pub f64_tbl: F64Table,
+    pub f64_tbl: Arc<F64Table>,
 }
 
 unsafe impl Send for Arena {}
@@ -681,7 +722,10 @@ unsafe impl Sync for Arena {}
 impl Arena {
     #[inline]
     pub fn new() -> Self {
-        Arena { base: ptr::null_mut(), f64_tbl: F64Table::new() }
+        Arena {
+            base: ptr::null_mut(),
+            f64_tbl: F64Table::new(),
+        }
     }
 }
 
@@ -731,8 +775,7 @@ unsafe fn drop_slab_in_place(value: &mut AllocSlab) {
         ArenaHeaderTag::LiveLoadState | ArenaHeaderTag::InactiveLoadState => {
             ptr::drop_in_place(value.payload_offset::<LiveLoadState>());
         }
-        ArenaHeaderTag::Dropped => {
+        ArenaHeaderTag::Dropped => {}
-        }
         ArenaHeaderTag::TcpListener => {
             ptr::drop_in_place(value.payload_offset::<TcpListener>());
         }
@@ -750,10 +793,11 @@ unsafe fn drop_slab_in_place(value: &mut AllocSlab) {
         ArenaHeaderTag::StandardErrorStream => {
             ptr::drop_in_place(value.payload_offset::<StreamLayout<StandardErrorStream>>());
         }
-        ArenaHeaderTag::NullStream | ArenaHeaderTag::IndexPtrUndefined |
+        ArenaHeaderTag::NullStream
-        ArenaHeaderTag::IndexPtrDynamicUndefined | ArenaHeaderTag::IndexPtrDynamicIndex |
+        | ArenaHeaderTag::IndexPtrUndefined
-        ArenaHeaderTag::IndexPtrIndex => {
+        | ArenaHeaderTag::IndexPtrDynamicUndefined
-        }
+        | ArenaHeaderTag::IndexPtrDynamicIndex
+        | ArenaHeaderTag::IndexPtrIndex => {}
     }
 }
 
@@ -801,23 +845,25 @@ const_assert!(mem::size_of::<OrderedFloat<f64>>() == 8);
 
 #[cfg(test)]
 mod tests {
+    use std::ops::Deref;
+
     use crate::machine::mock_wam::*;
     use crate::machine::partial_string::*;
 
-    use ordered_float::OrderedFloat;
     use crate::parser::dashu::{Integer, Rational};
+    use ordered_float::OrderedFloat;
 
     #[test]
     fn float_ptr_cast() {
-        let mut wam = MockWAM::new();
+        let wam = MockWAM::new();
 
         let f = 0f64;
         let fp = float_alloc!(f, wam.machine_st.arena);
-        let mut cell = HeapCellValue::from(fp);
+        let mut cell = HeapCellValue::from(fp.clone());
 
         assert_eq!(cell.get_tag(), HeapCellValueTag::F64);
         assert_eq!(cell.get_mark_bit(), false);
-        assert_eq!(*fp, OrderedFloat(f));
+        assert_eq!(fp.deref(), &OrderedFloat(f));
 
         cell.set_mark_bit(true);
 
@@ -847,7 +893,10 @@ mod tests {
 
         match const_value.to_untyped_arena_ptr() {
             Some(arena_ptr) => {
-                assert_eq!(arena_ptr.into_bytes(), const_value.to_untyped_arena_ptr_bytes());
+                assert_eq!(
+                    arena_ptr.into_bytes(),
+                    const_value.to_untyped_arena_ptr_bytes()
+                );
             }
             None => {
                 assert!(false);
@@ -860,7 +909,10 @@ mod tests {
 
         match stream_cell.to_untyped_arena_ptr() {
             Some(arena_ptr) => {
-                assert_eq!(arena_ptr.into_bytes(), stream_cell.to_untyped_arena_ptr_bytes());
+                assert_eq!(
+                    arena_ptr.into_bytes(),
+                    stream_cell.to_untyped_arena_ptr_bytes()
+                );
             }
             None => {
                 assert!(false);
@@ -875,8 +927,7 @@ mod tests {
         // integer
 
         let big_int: Integer = 2 * Integer::from(1u64 << 63);
-        let big_int_ptr: TypedArenaPtr<Integer> =
+        let big_int_ptr: TypedArenaPtr<Integer> = arena_alloc!(big_int, &mut wam.machine_st.arena);
-            arena_alloc!(big_int, &mut wam.machine_st.arena);
 
         assert!(!big_int_ptr.as_ptr().is_null());
 
@@ -951,8 +1002,8 @@ mod tests {
         let f_atom = atom!("f");
         let g_atom = atom!("g");
 
-        assert_eq!(f_atom.as_str(), "f");
+        assert_eq!(&*f_atom.as_str(), "f");
-        assert_eq!(g_atom.as_str(), "g");
+        assert_eq!(&*g_atom.as_str(), "g");
 
         let f_atom_cell = atom_as_cell!(f_atom);
         let g_atom_cell = atom_as_cell!(g_atom);
@@ -962,7 +1013,7 @@ mod tests {
         match f_atom_cell.to_atom() {
             Some(atom) => {
                 assert_eq!(f_atom, atom);
-                assert_eq!(atom.as_str(), "f");
+                assert_eq!(&*atom.as_str(), "f");
             }
             None => {
                 assert!(false);
@@ -973,7 +1024,7 @@ mod tests {
             (HeapCellValueTag::Atom, (atom, arity)) => {
                 assert_eq!(f_atom, atom);
                 assert_eq!(arity, 0);
-                assert_eq!(atom.as_str(), "f");
+                assert_eq!(&*atom.as_str(), "f");
             }
             _ => { unreachable!() }
         );
@@ -982,21 +1033,22 @@ mod tests {
             (HeapCellValueTag::Atom, (atom, arity)) => {
                 assert_eq!(g_atom, atom);
                 assert_eq!(arity, 0);
-                assert_eq!(atom.as_str(), "g");
+                assert_eq!(&*atom.as_str(), "g");
             }
             _ => { unreachable!() }
         );
 
         // complete string
 
-        let pstr_var_cell = put_partial_string(&mut wam.machine_st.heap, "ronan", &mut wam.machine_st.atom_tbl);
+        let pstr_var_cell =
+            put_partial_string(&mut wam.machine_st.heap, "ronan", &wam.machine_st.atom_tbl);
         let pstr_cell = wam.machine_st.heap[pstr_var_cell.get_value() as usize];
 
         assert_eq!(pstr_cell.get_tag(), HeapCellValueTag::PStr);
 
         match pstr_cell.to_pstr() {
             Some(pstr) => {
-                assert_eq!(pstr.as_str_from(0), "ronan");
+                assert_eq!(&*pstr.as_str_from(0), "ronan");
             }
             None => {
                 assert!(false);
@@ -1006,7 +1058,7 @@ mod tests {
         read_heap_cell!(pstr_cell,
             (HeapCellValueTag::PStr, pstr_atom) => {
                 let pstr = PartialString::from(pstr_atom);
-                assert_eq!(pstr.as_str_from(0), "ronan");
+                assert_eq!(&*pstr.as_str_from(0), "ronan");
             }
             _ => { unreachable!() }
         );
@@ -1115,7 +1167,7 @@ mod tests {
         read_heap_cell!(cell,
             (HeapCellValueTag::Atom, (el, _arity)) => {
                 assert_eq!(el.flat_index(), empty_list_as_cell!().get_value());
-                assert_eq!(el.as_str(), "[]");
+                assert_eq!(&*el.as_str(), "[]");
             }
             _ => { unreachable!() }
         );

src/arithmetic.rs

@@ -158,13 +158,13 @@ fn push_literal(interm: &mut Vec<ArithmeticTerm>, c: &Literal) -> Result<(), Ari
         Literal::Float(n) => interm.push(ArithmeticTerm::Number(Number::Float(*n.as_ptr()))),
         Literal::Rational(n) => interm.push(ArithmeticTerm::Number(Number::Rational(*n))),
         Literal::Atom(name) if name == &atom!("e") => interm.push(ArithmeticTerm::Number(
-            Number::Float(OrderedFloat(std::f64::consts::E))
+            Number::Float(OrderedFloat(std::f64::consts::E)),
         )),
         Literal::Atom(name) if name == &atom!("pi") => interm.push(ArithmeticTerm::Number(
-            Number::Float(OrderedFloat(std::f64::consts::PI))
+            Number::Float(OrderedFloat(std::f64::consts::PI)),
         )),
         Literal::Atom(name) if name == &atom!("epsilon") => interm.push(ArithmeticTerm::Number(
-            Number::Float(OrderedFloat(std::f64::EPSILON))
+            Number::Float(OrderedFloat(std::f64::EPSILON)),
         )),
         _ => return Err(ArithmeticError::NonEvaluableFunctor(*c, 0)),
     }
@@ -326,23 +326,14 @@ impl<'a> ArithmeticEvaluator<'a> {
                     let var_num = name.to_var_num().unwrap();
 
                     let r = if lvl == Level::Shallow {
-                        self.marker.mark_non_callable(
+                        self.marker
-                            var_num,
+                            .mark_non_callable(var_num, arg, term_loc, cell, &mut code)
-                            arg,
-                            term_loc,
-                            cell,
-                            &mut code,
-                        )
                     } else if term_loc.is_last() || cell.get().norm().reg_num() == 0 {
                         let r = self.marker.get_binding(var_num);
 
                         if r.reg_num() == 0 {
                             self.marker.mark_var::<QueryInstruction>(
-                                var_num,
+                                var_num, lvl, cell, term_loc, &mut code,
-                                lvl,
-                                cell,
-                                term_loc,
-                                &mut code,
                             );
                             cell.get().norm()
                         } else {
@@ -434,7 +425,7 @@ fn classify_float(f: f64) -> Result<f64, EvalError> {
             }
         }
         FpCategory::Nan => Err(EvalError::Undefined),
-        _ => Ok(f)
+        _ => Ok(f),
     }
 }
 
@@ -549,8 +540,12 @@ impl PartialEq for Number {
             (&Number::Fixnum(n1), &Number::Float(n2)) => OrderedFloat(n1.get_num() as f64).eq(&n2),
             (&Number::Float(n1), &Number::Fixnum(n2)) => n1.eq(&OrderedFloat(n2.get_num() as f64)),
             (&Number::Integer(ref n1), &Number::Integer(ref n2)) => n1.eq(n2),
-            (&Number::Integer(ref n1), Number::Float(n2)) => OrderedFloat(n1.to_f64().value()).eq(n2),
+            (&Number::Integer(ref n1), Number::Float(n2)) => {
-            (&Number::Float(n1), &Number::Integer(ref n2)) => n1.eq(&OrderedFloat(n2.to_f64().value())),
+                OrderedFloat(n1.to_f64().value()).eq(n2)
+            }
+            (&Number::Float(n1), &Number::Integer(ref n2)) => {
+                n1.eq(&OrderedFloat(n2.to_f64().value()))
+            }
             (&Number::Integer(ref n1), &Number::Rational(ref n2)) => {
                 #[cfg(feature = "num")]
                 {
@@ -571,8 +566,12 @@ impl PartialEq for Number {
                     &**n1 == &**n2
                 }
             }
-            (&Number::Rational(ref n1), &Number::Float(n2)) => OrderedFloat(n1.to_f64().value()).eq(&n2),
+            (&Number::Rational(ref n1), &Number::Float(n2)) => {
-            (&Number::Float(n1), &Number::Rational(ref n2)) => n1.eq(&OrderedFloat(n2.to_f64().value())),
+                OrderedFloat(n1.to_f64().value()).eq(&n2)
+            }
+            (&Number::Float(n1), &Number::Rational(ref n2)) => {
+                n1.eq(&OrderedFloat(n2.to_f64().value()))
+            }
             (&Number::Float(f1), &Number::Float(f2)) => f1.eq(&f2),
             (&Number::Rational(ref r1), &Number::Rational(ref r2)) => r1.eq(&r2),
         }
@@ -641,7 +640,9 @@ impl Ord for Number {
             (&Number::Float(n1), &Number::Fixnum(n2)) => n1.cmp(&OrderedFloat(n2.get_num() as f64)),
             (&Number::Integer(n1), &Number::Integer(n2)) => (*n1).cmp(&*n2),
             (&Number::Integer(n1), Number::Float(n2)) => OrderedFloat(n1.to_f64().value()).cmp(n2),
-            (&Number::Float(n1), &Number::Integer(ref n2)) => n1.cmp(&OrderedFloat(n2.to_f64().value())),
+            (&Number::Float(n1), &Number::Integer(ref n2)) => {
+                n1.cmp(&OrderedFloat(n2.to_f64().value()))
+            }
             (&Number::Integer(n1), &Number::Rational(n2)) => {
                 #[cfg(feature = "num")]
                 {
@@ -662,8 +663,12 @@ impl Ord for Number {
                     (&*n1).partial_cmp(&*n2).unwrap_or(Ordering::Less)
                 }
             }
-            (&Number::Rational(n1), &Number::Float(n2)) => OrderedFloat(n1.to_f64().value()).cmp(&n2),
+            (&Number::Rational(n1), &Number::Float(n2)) => {
-            (&Number::Float(n1), &Number::Rational(n2)) => n1.cmp(&OrderedFloat(n2.to_f64().value())),
+                OrderedFloat(n1.to_f64().value()).cmp(&n2)
+            }
+            (&Number::Float(n1), &Number::Rational(n2)) => {
+                n1.cmp(&OrderedFloat(n2.to_f64().value()))
+            }
             (&Number::Float(f1), &Number::Float(f2)) => f1.cmp(&f2),
             (&Number::Rational(r1), &Number::Rational(r2)) => (*r1).cmp(&*r2),
         }

src/atom_table.rs

@@ -1,18 +1,23 @@
 use crate::parser::ast::MAX_ARITY;
 use crate::raw_block::*;
+use crate::rcu::{Rcu, RcuRef};
 use crate::types::*;
 
-use std::borrow::Borrow;
 use std::cmp::Ordering;
 use std::hash::{Hash, Hasher};
 use std::mem;
+use std::ops::Deref;
 use std::ptr;
 use std::slice;
 use std::str;
+use std::sync::Arc;
+use std::sync::Mutex;
+use std::sync::Weak;
 
 use indexmap::IndexSet;
 
 use modular_bitfield::prelude::*;
+use tokio::sync::RwLock;
 
 #[derive(Copy, Clone, Debug, PartialEq, Eq)]
 pub struct Atom {
@@ -33,65 +38,43 @@ impl<'a> From<&'a Atom> for Atom {
 impl From<bool> for Atom {
     #[inline]
     fn from(value: bool) -> Self {
-        if value { atom!("true") } else { atom!("false") }
+        if value {
+            atom!("true")
+        } else {
+            atom!("false")
+        }
+    }
+}
+
+impl indexmap::Equivalent<Atom> for str {
+    fn equivalent(&self, key: &Atom) -> bool {
+        &*key.as_str() == self
     }
 }
 
 const ATOM_TABLE_INIT_SIZE: usize = 1 << 16;
 const ATOM_TABLE_ALIGN: usize = 8;
 
-#[cfg(test)]
+#[inline(always)]
-thread_local! {
+fn global_atom_table() -> &'static RwLock<Weak<AtomTable>> {
-   static ATOM_TABLE_BUF_BASE: std::cell::RefCell<*const u8> = std::cell::RefCell::new(ptr::null_mut());
+    #[cfg(feature = "rust_beta_channel")]
-}
-
-#[cfg(not(test))]
-static ATOM_TABLE_BUF_BASE: std::sync::atomic::AtomicPtr<u8> =
-    std::sync::atomic::AtomicPtr::new(ptr::null_mut());
-
-fn set_atom_tbl_buf_base(old_ptr: *const u8, new_ptr: *const u8) -> Result<(), *const u8> {
-#[cfg(test)]
     {
-    ATOM_TABLE_BUF_BASE.with(|atom_table_buf_base| {
+        // const Weak::new will be stabilized in 1.73 which is currently in beta,
-        let mut borrow = atom_table_buf_base.borrow_mut();
+        // till then we need a OnceLock for initialization
-            if *borrow != old_ptr {
+        static GLOBAL_ATOM_TABLE: RwLock<Weak<AtomTable>> = RwLock::const_new(Weak::new());
-                Err(*borrow)
+        &GLOBAL_ATOM_TABLE
-            } else {
-                *borrow = new_ptr;
-                Ok(())
     }
-        })?;
+    #[cfg(not(feature = "rust_beta_channel"))]
-    };
-    #[cfg(not(test))]
     {
-        ATOM_TABLE_BUF_BASE
+        use std::sync::OnceLock;
-            .compare_exchange(
+        static GLOBAL_ATOM_TABLE: OnceLock<RwLock<Weak<AtomTable>>> = OnceLock::new();
-                old_ptr.cast_mut(),
+        GLOBAL_ATOM_TABLE.get_or_init(|| RwLock::new(Weak::new()))
-                new_ptr.cast_mut(),
-                std::sync::atomic::Ordering::Relaxed,
-                std::sync::atomic::Ordering::Relaxed,
-            )
-            .map_err(|ptr| ptr.cast_const())
-    }?;
-    Ok(())
-}
-
-pub(crate) fn get_atom_tbl_buf_base() -> *const u8 {
-    #[cfg(test)]
-    {
-    ATOM_TABLE_BUF_BASE.with(|atom_table_buf_base| *atom_table_buf_base.borrow())
-}
-#[cfg(not(test))]
-    {
-        ATOM_TABLE_BUF_BASE.load(std::sync::atomic::Ordering::Relaxed)
     }
 }
 
-#[test]
+#[inline(always)]
-#[should_panic(expected = "Overwriting atom table base pointer")]
+fn arc_atom_table() -> Option<Arc<AtomTable>> {
-fn atomtable_is_not_concurrency_safe() {
+    global_atom_table().blocking_read().upgrade()
-    let _table_a = AtomTable::new();
-    let _table_b = AtomTable::new();
 }
 
 impl RawBlockTraits for AtomTable {
@@ -109,9 +92,11 @@ impl RawBlockTraits for AtomTable {
 #[bitfield]
 #[derive(Copy, Clone, Debug)]
 struct AtomHeader {
-    #[allow(unused)] m: bool,
+    #[allow(unused)]
+    m: bool,
     len: B50,
-    #[allow(unused)] padding: B13,
+    #[allow(unused)]
+    padding: B13,
 }
 
 impl AtomHeader {
@@ -120,13 +105,6 @@ impl AtomHeader {
     }
 }
 
-impl Borrow<str> for Atom {
-    #[inline]
-    fn borrow(&self) -> &str {
-        self.as_str()
-    }
-}
-
 impl Hash for Atom {
     #[inline]
     fn hash<H: Hasher>(&self, hasher: &mut H) {
@@ -142,29 +120,75 @@ macro_rules! is_char {
     };
 }
 
+pub enum AtomString<'a> {
+    Static(&'a str),
+    Dynamic(AtomTableRef<str>),
+}
+
+impl AtomString<'_> {
+    pub fn map<F>(self, f: F) -> Self
+    where
+        for<'a> F: FnOnce(&'a str) -> &'a str,
+    {
+        match self {
+            Self::Static(reference) => Self::Static(f(reference)),
+            Self::Dynamic(guard) => Self::Dynamic(AtomTableRef::map(guard, f)),
+        }
+    }
+}
+
+impl std::fmt::Debug for AtomString<'_> {
+    fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
+        std::fmt::Debug::fmt(self.deref(), f)
+    }
+}
+
+impl std::fmt::Display for AtomString<'_> {
+    fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
+        std::fmt::Display::fmt(self.deref(), f)
+    }
+}
+
+impl std::ops::Deref for AtomString<'_> {
+    type Target = str;
+    fn deref(&self) -> &Self::Target {
+        match self {
+            Self::Static(reference) => reference,
+            Self::Dynamic(guard) => guard.deref(),
+        }
+    }
+}
+
+impl rustyline::completion::Candidate for AtomString<'_> {
+    fn display(&self) -> &str {
+        self.deref()
+    }
+
+    fn replacement(&self) -> &str {
+        self.deref()
+    }
+}
+
 impl Atom {
-    #[inline]
-    pub fn buf(self) -> *const u8 {
-        let ptr = self.as_ptr();
-
-        if ptr.is_null() {
-            return ptr::null();
-        }
-
-        (ptr as usize + mem::size_of::<AtomHeader>()) as *const u8
-    }
-
     #[inline(always)]
     pub fn is_static(self) -> bool {
         (self.index as usize) < STRINGS.len() << 3
     }
 
     #[inline(always)]
-    pub fn as_ptr(self) -> *const u8 {
+    pub fn as_ptr(self) -> Option<AtomTableRef<u8>> {
         if self.is_static() {
-            ptr::null()
+            None
         } else {
-            (get_atom_tbl_buf_base() as usize + (self.index as usize) - (STRINGS.len() << 3)) as *const u8
+            let atom_table =
+                arc_atom_table().expect("We should only have an Atom while there is an AtomTable");
+            unsafe {
+                AtomTableRef::try_map(atom_table.buf(), |buf| {
+                    (buf as *const u8)
+                        .offset(((self.index as usize) - (STRINGS.len() << 3)) as isize)
+                        .as_ref()
+                })
+            }
         }
     }
 
@@ -178,7 +202,9 @@ impl Atom {
         if self.is_static() {
             STRINGS[(self.index >> 3) as usize].len()
         } else {
-            unsafe { ptr::read(self.as_ptr() as *const AtomHeader).len() as _ }
+            let ptr = self.as_ptr().unwrap();
+            let ptr = ptr.deref() as *const u8 as *const AtomHeader;
+            unsafe { ptr::read(ptr) }.len() as _
         }
     }
 
@@ -194,41 +220,44 @@ impl Atom {
         let c1 = it.next();
         let c2 = it.next();
 
-        if c2.is_none() { c1 } else { None }
+        if c2.is_none() {
+            c1
+        } else {
+            None
+        }
     }
 
     #[inline]
-    pub fn chars(&self) -> str::Chars {
+    pub fn as_str(&self) -> AtomString<'static> {
-        self.as_str().chars()
+        if self.is_static() {
-    }
+            AtomString::Static(STRINGS[(self.index >> 3) as usize])
-
+        } else {
-    #[inline]
+            if let Some(ptr) = self.as_ptr() {
-    pub fn as_str(&self) -> &str {
+                AtomString::Dynamic(AtomTableRef::map(ptr, |ptr| {
-        unsafe {
+                    let header =
-            let ptr = self.as_ptr();
+                        unsafe { ptr::read::<AtomHeader>(ptr as *const u8 as *const AtomHeader) };
-
-            if ptr.is_null() {
-                return STRINGS[(self.index >> 3) as usize];
-            }
-
-            let header = ptr::read::<AtomHeader>(ptr as *const _);
                     let len = header.len() as usize;
-            let buf = (ptr as usize + mem::size_of::<AtomHeader>()) as *mut u8;
+                    let buf =
+                        unsafe { (ptr as *const u8).offset(mem::size_of::<AtomHeader>() as isize) };
 
-            str::from_utf8_unchecked(slice::from_raw_parts(buf, len))
+                    unsafe { str::from_utf8_unchecked(slice::from_raw_parts(buf, len)) }
+                }))
+            } else {
+                AtomString::Static(&STRINGS[(self.index >> 3) as usize])
+            }
         }
     }
 
-    pub fn defrock_brackets(&self, atom_tbl: &mut AtomTable) -> Self {
+    pub fn defrock_brackets(&self, atom_tbl: &AtomTable) -> Self {
         let s = self.as_str();
 
-        let s = if s.starts_with('(') && s.ends_with(')') {
+        let sub_str = if s.starts_with('(') && s.ends_with(')') {
             &s['('.len_utf8()..s.len() - ')'.len_utf8()]
         } else {
             return *self;
         };
 
-        atom_tbl.build_with(s)
+        AtomTable::build_with(&atom_tbl, &sub_str)
     }
 }
 
@@ -248,93 +277,121 @@ impl PartialOrd for Atom {
 impl Ord for Atom {
     #[inline]
     fn cmp(&self, other: &Atom) -> Ordering {
-        self.as_str().cmp(other.as_str())
+        self.as_str().cmp(&*other.as_str())
     }
 }
 
 #[derive(Debug)]
-pub struct AtomTable {
+pub struct InnerAtomTable {
     block: RawBlock<AtomTable>,
-    pub table: IndexSet<Atom>,
+    pub table: Rcu<IndexSet<Atom>>,
 }
 
-#[cold]
+#[derive(Debug)]
-fn atom_table_base_pointer_mismatch(expected: *const u8, got: *const u8) -> ! {
+pub struct AtomTable {
-    assert_eq!(expected, got, "Overwriting atom table base pointer, expected old value to be {expected:p}, but found {got:p}");
+    inner: Rcu<InnerAtomTable>,
-    unreachable!("This should only be called in a case of a mismatch as such the assert_eq should have failed!")
+    // this lock is taking during resizing
+    update: Mutex<()>,
 }
 
-impl Drop for AtomTable {
+pub type AtomTableRef<M> = RcuRef<InnerAtomTable, M>;
-    fn drop(&mut self) {
+
-        if let Err(got) = set_atom_tbl_buf_base(self.block.base, ptr::null()) {
+impl InnerAtomTable {
-            atom_table_base_pointer_mismatch(self.block.base, got);
+    #[inline(always)]
-        }
+    fn lookup_str(self: &InnerAtomTable, string: &str) -> Option<Atom> {
-        self.block.deallocate();
+        STATIC_ATOMS_MAP
+            .get(string)
+            .cloned()
+            .or_else(|| self.table.active_epoch().get(string).cloned())
     }
 }
 
 impl AtomTable {
     #[inline]
-    pub fn new() -> Self {
+    pub fn new() -> Arc<Self> {
-        let mut block = RawBlock::new();
+        let upgraded = global_atom_table().blocking_read().upgrade();
-
+        // don't inline upgraded, otherwise temporary will be dropped too late in case of None
-        if let Err(got) = set_atom_tbl_buf_base(ptr::null(), block.base) {
+        if let Some(atom_table) = upgraded {
-            block.deallocate();
+            atom_table
-            atom_table_base_pointer_mismatch(ptr::null(), got);
+        } else {
+            let mut guard = global_atom_table().blocking_write();
+            // try to upgrade again in case we lost the race on the write lock
+            if let Some(atom_table) = guard.upgrade() {
+                atom_table
+            } else {
+                let atom_table = Arc::new(Self {
+                    inner: Rcu::new(InnerAtomTable {
+                        block: RawBlock::new(),
+                        table: Rcu::new(IndexSet::new()),
+                    }),
+                    update: Mutex::new(()),
+                });
+                *guard = Arc::downgrade(&atom_table);
+                atom_table
             }
-
-        Self {
-            block,
-            table: IndexSet::new(),
         }
     }
 
     #[inline]
-    pub fn buf(&self) -> *const u8 {
+    pub fn buf(&self) -> AtomTableRef<u8> {
-        self.block.base as *const u8
+        AtomTableRef::<InnerAtomTable>::map(self.inner.active_epoch(), |inner| {
+            unsafe { inner.block.base.as_ref() }.unwrap()
+        })
     }
 
-    #[inline]
+    pub fn active_table(&self) -> RcuRef<IndexSet<Atom>, IndexSet<Atom>> {
-    pub fn top(&self) -> *const u8 {
+        self.inner.active_epoch().table.active_epoch()
-        self.block.top
     }
 
-    #[inline(always)]
+    pub fn build_with(atom_table: &AtomTable, string: &str) -> Atom {
-    fn lookup_str(&self, string: &str) -> Option<Atom> {
+        loop {
-        STATIC_ATOMS_MAP.get(string).or_else(|| self.table.get(string)).cloned()
+            let mut block_epoch = atom_table.inner.active_epoch();
-    }
+            let mut table_epoch = block_epoch.table.active_epoch();
 
-    pub fn build_with(&mut self, string: &str) -> Atom {
+            if let Some(atom) = block_epoch.lookup_str(string) {
-        if let Some(atom) = self.lookup_str(string) {
                 return atom;
             }
 
-        unsafe {
+            // take a lock to prevent concurrent updates
+            let update_guard = atom_table.update.lock().unwrap();
+
+            let is_same_allocation =
+                RcuRef::same_epoch(&block_epoch, &atom_table.inner.active_epoch());
+            let is_same_atom_list =
+                RcuRef::same_epoch(&table_epoch, &block_epoch.table.active_epoch());
+
+            if !(is_same_allocation && is_same_atom_list) {
+                // some other thread raced us between our lookup and
+                // us aquring the update lock,
+                // try again
+                continue;
+            }
+
             let size = mem::size_of::<AtomHeader>() + string.len();
             let align_offset = 8 * mem::align_of::<AtomHeader>();
             let size = (size & !(align_offset - 1)) + align_offset;
 
-            let len_ptr = {
+            unsafe {
-                let mut ptr;
+                let len_ptr = loop {
-
+                    let ptr = block_epoch.block.alloc(size);
-                loop {
-                    ptr = self.block.alloc(size);
 
                     if ptr.is_null() {
-                        let old_base = self.block.base;
+                        // garbage collection would go here
-                        self.block.grow();
+                        let new_block = block_epoch.block.grow_new().unwrap();
-                        if let Err(got) = set_atom_tbl_buf_base(old_base, self.block.base) {
+                        let new_table = Rcu::new(table_epoch.clone());
-                            atom_table_base_pointer_mismatch(old_base, got);
+                        let new_alloc = InnerAtomTable {
-                        }
+                            block: new_block,
+                            table: new_table,
+                        };
+                        atom_table.inner.replace(new_alloc);
+                        block_epoch = atom_table.inner.active_epoch();
+                        table_epoch = block_epoch.table.active_epoch();
                     } else {
-                        break;
+                        break ptr;
                     }
-                }
-
-                ptr
                 };
 
-            let ptr_base = self.block.base as usize;
+                let ptr_base = block_epoch.block.base as usize;
 
                 write_to_ptr(string, len_ptr);
 
@@ -342,12 +399,21 @@ impl AtomTable {
                     index: ((STRINGS.len() << 3) + len_ptr as usize - ptr_base) as u64,
                 };
 
-            self.table.insert(atom);
+                let mut table = table_epoch.clone();
+                table.insert(atom);
+                block_epoch.table.replace(table);
 
-            atom
+                // expicit drop to ensure we don't accidentally drop it early
+                drop(update_guard);
+
+                return atom;
             }
         }
     }
+}
+
+unsafe impl Send for AtomTable {}
+unsafe impl Sync for AtomTable {}
 
 #[bitfield]
 #[repr(u64)]
@@ -355,9 +421,12 @@ impl AtomTable {
 pub struct AtomCell {
     name: B46,
     arity: B10,
-    #[allow(unused)] f: bool,
+    #[allow(unused)]
-    #[allow(unused)] m: bool,
+    f: bool,
-    #[allow(unused)] tag: B6,
+    #[allow(unused)]
+    m: bool,
+    #[allow(unused)]
+    tag: B6,
 }
 
 impl AtomCell {

src/bin/scryer-prolog.rs

@@ -1,11 +1,12 @@
 fn main() -> std::process::ExitCode {
-    use std::sync::atomic::Ordering;
     use scryer_prolog::*;
+    use std::sync::atomic::Ordering;
 
     #[cfg(feature = "repl")]
     ctrlc::set_handler(move || {
         scryer_prolog::machine::INTERRUPT.store(true, Ordering::Relaxed);
-    }).unwrap();
+    })
+    .unwrap();
 
     let mut wam = machine::Machine::new();
     wam.run_top_level()

src/codegen.rs

@@ -1,14 +1,14 @@
-use crate::atom_table::*;
-use crate::parser::ast::*;
-use crate::temp_v;
 use crate::allocator::*;
 use crate::arithmetic::*;
+use crate::atom_table::*;
 use crate::debray_allocator::*;
 use crate::forms::*;
 use crate::indexing::*;
 use crate::instructions::*;
 use crate::iterators::*;
+use crate::parser::ast::*;
 use crate::targets::*;
+use crate::temp_v;
 use crate::types::*;
 
 use crate::instr;
@@ -48,12 +48,17 @@ impl BranchCodeStack {
     }
 
     fn code<'a>(&'a mut self, default_code: &'a mut CodeDeque) -> &'a mut CodeDeque {
-        self.stack.last_mut()
+        self.stack
+            .last_mut()
             .and_then(|stack| stack.last_mut())
             .unwrap_or(default_code)
     }
 
-    fn push_missing_vars(&mut self, depth: usize, marker: &mut DebrayAllocator) -> SubsumedBranchHits {
+    fn push_missing_vars(
+        &mut self,
+        depth: usize,
+        marker: &mut DebrayAllocator,
+    ) -> SubsumedBranchHits {
         let mut subsumed_hits = SubsumedBranchHits::with_hasher(FxBuildHasher::default());
 
         for idx in (self.stack.len() - depth..self.stack.len()).rev() {
@@ -119,7 +124,9 @@ impl BranchCodeStack {
 
         for mut branch_arm in self.stack.drain(self.stack.len() - depth..).rev() {
             let num_branch_arms = branch_arm.len();
-            branch_arm.last_mut().map(|code| code.extend(combined_code.drain(..)));
+            branch_arm
+                .last_mut()
+                .map(|code| code.extend(combined_code.drain(..)));
 
             for (idx, code) in branch_arm.into_iter().enumerate() {
                 combined_code.push_back(if idx == 0 {
@@ -255,7 +262,7 @@ impl CodeGenSettings {
 
 #[derive(Debug)]
 pub(crate) struct CodeGenerator<'a> {
-    pub(crate) atom_tbl: &'a mut AtomTable,
+    pub(crate) atom_tbl: &'a AtomTable,
     marker: DebrayAllocator,
     settings: CodeGenSettings,
     pub(crate) skeleton: PredicateSkeleton,
@@ -269,13 +276,7 @@ impl DebrayAllocator {
         vr: &Cell<VarReg>,
         code: &mut CodeDeque,
     ) -> RegType {
-        self.mark_var::<QueryInstruction>(
+        self.mark_var::<QueryInstruction>(var_num, Level::Shallow, vr, term_loc, code);
-            var_num,
-            Level::Shallow,
-            vr,
-            term_loc,
-            code,
-        );
 
         vr.get().norm()
     }
@@ -308,8 +309,8 @@ impl DebrayAllocator {
 // decrement the arity of the PutStructure instruction by 1.
 fn trim_structure_by_last_arg(instr: &mut Instruction, last_arg: &Term) {
     match instr {
-        Instruction::PutStructure(_, ref mut arity, _) |
+        Instruction::PutStructure(_, ref mut arity, _)
-        Instruction::GetStructure(.., ref mut arity, _) => {
+        | Instruction::GetStructure(.., ref mut arity, _) => {
             if let Term::Literal(_, Literal::CodeIndex(_)) = last_arg {
                 // it is acceptable if arity == 0 is the result of
                 // this decrement. call/N will have to read the index
@@ -352,16 +353,16 @@ impl<'a, 'b> AddToFreeList<'a, QueryInstruction> for CodeGenerator<'b> {
 
 fn structure_cell(term: &Term) -> Option<&Cell<RegType>> {
     match term {
-        &Term::Cons(ref cell, ..) |
+        &Term::Cons(ref cell, ..)
-        &Term::Clause(ref cell, ..) |
+        | &Term::Clause(ref cell, ..)
-        Term::PartialString(ref cell, ..) |
+        | Term::PartialString(ref cell, ..)
-        Term::CompleteString(ref cell, ..) => Some(cell),
+        | Term::CompleteString(ref cell, ..) => Some(cell),
         _ => None,
     }
 }
 
 impl<'b> CodeGenerator<'b> {
-    pub(crate) fn new(atom_tbl: &'b mut AtomTable, settings: CodeGenSettings) -> Self {
+    pub(crate) fn new(atom_tbl: &'b AtomTable, settings: CodeGenSettings) -> Self {
         CodeGenerator {
             atom_tbl,
             marker: DebrayAllocator::new(),
@@ -392,7 +393,8 @@ impl<'b> CodeGenerator<'b> {
         target: &mut CodeDeque,
     ) {
         if self.marker.var_data.records[var_num].num_occurrences > 1 {
-            self.marker.mark_var::<Target>(var_num, Level::Deep, cell, term_loc, target);
+            self.marker
+                .mark_var::<Target>(var_num, Level::Deep, cell, term_loc, target);
         } else {
             Self::add_or_increment_void_instr::<Target>(target);
         }
@@ -408,31 +410,33 @@ impl<'b> CodeGenerator<'b> {
             &Term::AnonVar => {
                 Self::add_or_increment_void_instr::<Target>(target);
             }
-            &Term::Cons(ref cell, ..) |
+            &Term::Cons(ref cell, ..)
-            &Term::Clause(ref cell, ..) |
+            | &Term::Clause(ref cell, ..)
-            Term::PartialString(ref cell, ..) |
+            | Term::PartialString(ref cell, ..)
-            Term::CompleteString(ref cell, ..) => {
+            | Term::CompleteString(ref cell, ..) => {
-                self.marker.mark_non_var::<Target>(Level::Deep, term_loc, cell, target);
+                self.marker
+                    .mark_non_var::<Target>(Level::Deep, term_loc, cell, target);
                 target.push_back(Target::clause_arg_to_instr(cell.get()));
             }
             &Term::Literal(_, ref constant) => {
                 target.push_back(Target::constant_subterm(constant.clone()));
             }
             &Term::Var(ref cell, ref var_ptr) => {
-                self.deep_var_instr::<Target>(cell, var_ptr.to_var_num().unwrap(), term_loc, target);
+                self.deep_var_instr::<Target>(
+                    cell,
+                    var_ptr.to_var_num().unwrap(),
+                    term_loc,
+                    target,
+                );
             }
         };
     }
 
-    fn compile_target<'a, Target, Iter>(
+    fn compile_target<'a, Target, Iter>(&mut self, iter: Iter, term_loc: GenContext) -> CodeDeque
-        &mut self,
-        iter: Iter,
-        term_loc: GenContext,
-    ) -> CodeDeque
     where
         Target: crate::targets::CompilationTarget<'a>,
         Iter: Iterator<Item = TermRef<'a>>,
-        CodeGenerator<'b>: AddToFreeList<'a, Target>
+        CodeGenerator<'b>: AddToFreeList<'a, Target>,
     {
         let mut target = CodeDeque::new();
 
@@ -442,14 +446,19 @@ impl<'b> CodeGenerator<'b> {
                     if let GenContext::Head = term_loc {
                         self.marker.advance_arg();
                     } else {
-                        self.marker.mark_anon_var::<Target>(lvl, term_loc, &mut target);
+                        self.marker
+                            .mark_anon_var::<Target>(lvl, term_loc, &mut target);
                     }
                 }
                 TermRef::Clause(lvl, cell, name, terms) => {
-                    self.marker.mark_non_var::<Target>(lvl, term_loc, cell, &mut target);
+                    self.marker
+                        .mark_non_var::<Target>(lvl, term_loc, cell, &mut target);
                     target.push_back(Target::to_structure(lvl, name, terms.len(), cell.get()));
 
-                    <CodeGenerator<'b> as AddToFreeList<'a, Target>>::add_term_to_free_list(self, cell.get());
+                    <CodeGenerator<'b> as AddToFreeList<'a, Target>>::add_term_to_free_list(
+                        self,
+                        cell.get(),
+                    );
 
                     if let Some(instr) = target.back_mut() {
                         if let Some(term) = terms.last() {
@@ -462,38 +471,52 @@ impl<'b> CodeGenerator<'b> {
                     }
 
                     for subterm in terms {
-                        <CodeGenerator<'b> as AddToFreeList<'a, Target>>::add_subterm_to_free_list(self, subterm);
+                        <CodeGenerator<'b> as AddToFreeList<'a, Target>>::add_subterm_to_free_list(
+                            self, subterm,
+                        );
                     }
                 }
                 TermRef::Cons(lvl, cell, head, tail) => {
-                    self.marker.mark_non_var::<Target>(lvl, term_loc, cell, &mut target);
+                    self.marker
+                        .mark_non_var::<Target>(lvl, term_loc, cell, &mut target);
                     target.push_back(Target::to_list(lvl, cell.get()));
 
-                    <CodeGenerator<'b> as AddToFreeList<'a, Target>>::add_term_to_free_list(self, cell.get());
+                    <CodeGenerator<'b> as AddToFreeList<'a, Target>>::add_term_to_free_list(
+                        self,
+                        cell.get(),
+                    );
 
                     self.subterm_to_instr::<Target>(head, term_loc, &mut target);
                     self.subterm_to_instr::<Target>(tail, term_loc, &mut target);
 
-                    <CodeGenerator<'b> as AddToFreeList<'a, Target>>::add_subterm_to_free_list(self, head);
+                    <CodeGenerator<'b> as AddToFreeList<'a, Target>>::add_subterm_to_free_list(
-                    <CodeGenerator<'b> as AddToFreeList<'a, Target>>::add_subterm_to_free_list(self, tail);
+                        self, head,
+                    );
+                    <CodeGenerator<'b> as AddToFreeList<'a, Target>>::add_subterm_to_free_list(
+                        self, tail,
+                    );
                 }
                 TermRef::Literal(lvl @ Level::Shallow, cell, Literal::String(ref string)) => {
-                    self.marker.mark_non_var::<Target>(lvl, term_loc, cell, &mut target);
+                    self.marker
+                        .mark_non_var::<Target>(lvl, term_loc, cell, &mut target);
                     target.push_back(Target::to_pstr(lvl, *string, cell.get(), false));
                 }
                 TermRef::Literal(lvl @ Level::Shallow, cell, constant) => {
-                    self.marker.mark_non_var::<Target>(lvl, term_loc, cell, &mut target);
+                    self.marker
+                        .mark_non_var::<Target>(lvl, term_loc, cell, &mut target);
                     target.push_back(Target::to_constant(lvl, *constant, cell.get()));
                 }
                 TermRef::PartialString(lvl, cell, string, tail) => {
-                    self.marker.mark_non_var::<Target>(lvl, term_loc, cell, &mut target);
+                    self.marker
-                    let atom = self.atom_tbl.build_with(&string);
+                        .mark_non_var::<Target>(lvl, term_loc, cell, &mut target);
+                    let atom = AtomTable::build_with(&self.atom_tbl, &string);
 
                     target.push_back(Target::to_pstr(lvl, atom, cell.get(), true));
                     self.subterm_to_instr::<Target>(tail, term_loc, &mut target);
                 }
                 TermRef::CompleteString(lvl, cell, atom) => {
-                    self.marker.mark_non_var::<Target>(lvl, term_loc, cell, &mut target);
+                    self.marker
+                        .mark_non_var::<Target>(lvl, term_loc, cell, &mut target);
                     target.push_back(Target::to_pstr(lvl, atom, cell.get(), false));
                 }
                 TermRef::Var(lvl @ Level::Shallow, cell, var) => {
@@ -563,9 +586,9 @@ impl<'b> CodeGenerator<'b> {
                 compare_number_instr!(cmp, at_1, at_2)
             }
             &InlinedClauseType::IsAtom(..) => match &terms[0] {
-                &Term::Literal(_, Literal::Char(_)) |
+                &Term::Literal(_, Literal::Char(_))
-                &Term::Literal(_, Literal::Atom(atom!("[]"))) |
+                | &Term::Literal(_, Literal::Atom(atom!("[]")))
-                &Term::Literal(_, Literal::Atom(..)) => {
+                | &Term::Literal(_, Literal::Atom(..)) => {
                     instr!("$succeed")
                 }
                 &Term::Var(ref vr, ref name) => {
@@ -586,11 +609,11 @@ impl<'b> CodeGenerator<'b> {
                 }
             },
             &InlinedClauseType::IsAtomic(..) => match &terms[0] {
-                &Term::AnonVar |
+                &Term::AnonVar
-                &Term::Clause(..) |
+                | &Term::Clause(..)
-                &Term::Cons(..) |
+                | &Term::Cons(..)
-                &Term::PartialString(..) |
+                | &Term::PartialString(..)
-                &Term::CompleteString(..) => {
+                | &Term::CompleteString(..) => {
                     instr!("$fail")
                 }
                 &Term::Literal(_, Literal::String(_)) => {
@@ -614,11 +637,11 @@ impl<'b> CodeGenerator<'b> {
                 }
             },
             &InlinedClauseType::IsCompound(..) => match &terms[0] {
-                &Term::Clause(..) |
+                &Term::Clause(..)
-                &Term::Cons(..) |
+                | &Term::Cons(..)
-                &Term::PartialString(..) |
+                | &Term::PartialString(..)
-                &Term::CompleteString(..) |
+                | &Term::CompleteString(..)
-                &Term::Literal(_, Literal::String(..)) => {
+                | &Term::Literal(_, Literal::String(..)) => {
                     instr!("$succeed")
                 }
                 &Term::Var(ref vr, ref name) => {
@@ -644,7 +667,13 @@ impl<'b> CodeGenerator<'b> {
                 }
                 &Term::Var(ref vr, ref name) => {
                     self.marker.reset_arg(1);
-                    let r = self.marker.mark_non_callable(name.to_var_num().unwrap(), 1,  term_loc, vr, code);
+                    let r = self.marker.mark_non_callable(
+                        name.to_var_num().unwrap(),
+                        1,
+                        term_loc,
+                        vr,
+                        code,
+                    );
                     instr!("rational", r)
                 }
                 _ => {
@@ -673,10 +702,10 @@ impl<'b> CodeGenerator<'b> {
                 }
             },
             &InlinedClauseType::IsNumber(..) => match &terms[0] {
-                &Term::Literal(_, Literal::Float(_)) |
+                &Term::Literal(_, Literal::Float(_))
-                &Term::Literal(_, Literal::Rational(_)) |
+                | &Term::Literal(_, Literal::Rational(_))
-                &Term::Literal(_, Literal::Integer(_)) |
+                | &Term::Literal(_, Literal::Integer(_))
-                &Term::Literal(_, Literal::Fixnum(_)) => {
+                | &Term::Literal(_, Literal::Fixnum(_)) => {
                     instr!("$succeed")
                 }
                 &Term::Var(ref vr, ref name) => {
@@ -718,8 +747,7 @@ impl<'b> CodeGenerator<'b> {
                 }
             },
             &InlinedClauseType::IsInteger(..) => match &terms[0] {
-                &Term::Literal(_, Literal::Integer(_)) |
+                &Term::Literal(_, Literal::Integer(_)) | &Term::Literal(_, Literal::Fixnum(_)) => {
-                &Term::Literal(_, Literal::Fixnum(_)) => {
                     instr!("$succeed")
                 }
                 &Term::Var(ref vr, ref name) => {
@@ -740,11 +768,11 @@ impl<'b> CodeGenerator<'b> {
                 }
             },
             &InlinedClauseType::IsVar(..) => match &terms[0] {
-                &Term::Literal(..) |
+                &Term::Literal(..)
-                &Term::Clause(..) |
+                | &Term::Clause(..)
-                &Term::Cons(..) |
+                | &Term::Cons(..)
-                &Term::PartialString(..) |
+                | &Term::PartialString(..)
-                &Term::CompleteString(..) => {
+                | &Term::CompleteString(..) => {
                     instr!("$fail")
                 }
                 &Term::AnonVar => {
@@ -791,11 +819,11 @@ impl<'b> CodeGenerator<'b> {
         call_policy: CallPolicy,
     ) -> Result<(), CompilationError> {
         macro_rules! compile_expr {
-            ($self:expr, $terms:expr, $term_loc:expr, $code:expr) => ({
+            ($self:expr, $terms:expr, $term_loc:expr, $code:expr) => {{
                 let (acode, at) = $self.compile_arith_expr($terms, 1, $term_loc, 2)?;
                 $code.extend(acode.into_iter());
                 at
-            });
+            }};
         }
 
         self.marker.reset_arg(2);
@@ -843,10 +871,13 @@ impl<'b> CodeGenerator<'b> {
                     compile_expr!(self, &terms[1], term_loc, code)
                 }
             }
-            &Term::Literal(_, c @ Literal::Integer(_) |
+            &Term::Literal(
-                              c @ Literal::Float(_) |
+                _,
-                              c @ Literal::Rational(_) |
+                c @ Literal::Integer(_)
-                              c @ Literal::Fixnum(_)) => {
+                | c @ Literal::Float(_)
+                | c @ Literal::Rational(_)
+                | c @ Literal::Fixnum(_),
+            ) => {
                 let v = HeapCellValue::from(c);
                 code.push_back(instr!("put_constant", Level::Shallow, v, temp_v!(1)));
 
@@ -939,15 +970,29 @@ impl<'b> CodeGenerator<'b> {
                                 ClauseType::BuiltIn(BuiltInClauseType::Is(..)),
                                 ref terms,
                                 call_policy,
-                            ) => self.compile_is_call(terms, branch_code_stack.code(code), term_loc, call_policy)?,
+                            ) => self.compile_is_call(
+                                terms,
+                                branch_code_stack.code(code),
+                                term_loc,
+                                call_policy,
+                            )?,
                             &QueryTerm::Clause(_, ClauseType::Inlined(ref ct), ref terms, _) => {
-                                self.compile_inlined(ct, terms, term_loc, branch_code_stack.code(code))?
+                                self.compile_inlined(
+                                    ct,
+                                    terms,
+                                    term_loc,
+                                    branch_code_stack.code(code),
+                                )?
                             }
                             &QueryTerm::Fail => {
                                 branch_code_stack.code(code).push_back(instr!("$fail"));
                             }
                             term @ &QueryTerm::Clause(..) => {
-                                self.compile_query_line(term, term_loc, branch_code_stack.code(code));
+                                self.compile_query_line(
+                                    term,
+                                    term_loc,
+                                    branch_code_stack.code(code),
+                                );
 
                                 if self.marker.max_reg_allocated() > MAX_ARITY {
                                     return Err(CompilationError::ExceededMaxArity);
@@ -975,7 +1020,8 @@ impl<'b> CodeGenerator<'b> {
                 }
                 ClauseItem::BranchEnd(depth) => {
                     if !clause_iter.in_tail_position() {
-                        let subsumed_hits = branch_code_stack.push_missing_vars(depth, &mut self.marker);
+                        let subsumed_hits =
+                            branch_code_stack.push_missing_vars(depth, &mut self.marker);
                         self.marker.pop_branch(depth, subsumed_hits);
                         branch_code_stack.push_jump_instrs(depth);
                     } else {
@@ -1001,8 +1047,15 @@ impl<'b> CodeGenerator<'b> {
         Ok(())
     }
 
-    pub(crate) fn compile_rule(&mut self, rule: &Rule, var_data: VarData) -> Result<Code, CompilationError> {
+    pub(crate) fn compile_rule(
-        let Rule { head: (_, args), clauses } = rule;
+        &mut self,
+        rule: &Rule,
+        var_data: VarData,
+    ) -> Result<Code, CompilationError> {
+        let Rule {
+            head: (_, args),
+            clauses,
+        } = rule;
         self.marker.var_data = var_data;
         let mut code = VecDeque::new();
 
@@ -1023,7 +1076,11 @@ impl<'b> CodeGenerator<'b> {
         Ok(Vec::from(code))
     }
 
-    pub(crate) fn compile_fact(&mut self, fact: &Fact, var_data: VarData) -> Result<Code, CompilationError> {
+    pub(crate) fn compile_fact(
+        &mut self,
+        fact: &Fact,
+        var_data: VarData,
+    ) -> Result<Code, CompilationError> {
         let mut code = Vec::new();
         self.marker.var_data = var_data;
 
@@ -1031,10 +1088,7 @@ impl<'b> CodeGenerator<'b> {
             self.marker.reset_at_head(args);
 
             let iter = FactInstruction::iter(&fact.head);
-            let compiled_fact = self.compile_target::<FactInstruction, _>(
+            let compiled_fact = self.compile_target::<FactInstruction, _>(iter, GenContext::Head);
-                iter,
-                GenContext::Head,
-            );
 
             if self.marker.max_reg_allocated() > MAX_ARITY {
                 return Err(CompilationError::ExceededMaxArity);
@@ -1059,7 +1113,7 @@ impl<'b> CodeGenerator<'b> {
             &QueryTerm::Clause(_, ref ct, _, call_policy) => {
                 self.add_call(code, ct.to_instr(), call_policy);
             }
-            _ => unreachable!()
+            _ => unreachable!(),
         };
     }
 
@@ -1072,8 +1126,7 @@ impl<'b> CodeGenerator<'b> {
             if let Some(args) = clause.args() {
                 for (instantiated_arg_index, arg) in args.iter().enumerate() {
                     match arg {
-                        Term::Var(..) | Term::AnonVar => {
+                        Term::Var(..) | Term::AnonVar => {}
-                        }
                         _ => {
                             if optimal_index != instantiated_arg_index {
                                 if left >= right {
@@ -1098,7 +1151,11 @@ impl<'b> CodeGenerator<'b> {
             }
 
             if left < right {
-                subseqs.push(ClauseSpan { left, right, instantiated_arg_index: optimal_index });
+                subseqs.push(ClauseSpan {
+                    left,
+                    right,
+                    instantiated_arg_index: optimal_index,
+                });
             }
 
             optimal_index = 0;
@@ -1129,11 +1186,8 @@ impl<'b> CodeGenerator<'b> {
         optimal_index: usize,
     ) -> Result<Code, CompilationError> {
         let mut code = VecDeque::new();
-        let mut code_offsets = CodeOffsets::new(
+        let mut code_offsets =
-            I::new(),
+            CodeOffsets::new(I::new(), optimal_index + 1, self.settings.non_counted_bt);
-            optimal_index + 1,
-            self.settings.non_counted_bt,
-        );
 
         let mut skip_stub_try_me_else = false;
         let clauses_len = clauses.len();
@@ -1178,7 +1232,9 @@ impl<'b> CodeGenerator<'b> {
                 skip_stub_try_me_else = !self.settings.is_dynamic();
             }
 
-            let arg = clause.args().and_then(|args| args.iter().nth(optimal_index));
+            let arg = clause
+                .args()
+                .and_then(|args| args.iter().nth(optimal_index));
 
             if let Some(arg) = arg {
                 let index = code.len();
@@ -1221,7 +1277,12 @@ impl<'b> CodeGenerator<'b> {
         let split_pred = Self::split_predicate(&clauses);
         let multi_seq = split_pred.len() > 1;
 
-        for ClauseSpan { left, right, instantiated_arg_index } in split_pred {
+        for ClauseSpan {
+            left,
+            right,
+            instantiated_arg_index,
+        } in split_pred
+        {
             let skel_lower_bound = self.skeleton.clauses.len();
             let code_segment = if self.settings.is_dynamic() {
                 self.compile_pred_subseq::<DynamicCodeIndices>(
@@ -1252,9 +1313,8 @@ impl<'b> CodeGenerator<'b> {
             if self.settings.is_extensible {
                 let segment_is_indexed = code_segment[0].to_indexing_line().is_some();
 
-                for clause_index_info in self.skeleton.clauses
+                for clause_index_info in
-                                             .make_contiguous()[skel_lower_bound..]
+                    self.skeleton.clauses.make_contiguous()[skel_lower_bound..].iter_mut()
-                                             .iter_mut()
                 {
                     clause_index_info.clause_start +=
                         clause_start_offset + 2 * (segment_is_indexed as usize);

src/debray_allocator.rs

@@ -76,11 +76,16 @@ impl BranchStack {
         }
     }
 
-    fn safety_unneeded_in_branch(&self, safety: &VarSafetyStatus, branch: &BranchDesignator) -> bool {
+    fn safety_unneeded_in_branch(
+        &self,
+        safety: &VarSafetyStatus,
+        branch: &BranchDesignator,
+    ) -> bool {
         match safety {
             VarSafetyStatus::Needed => false,
-            VarSafetyStatus::LocallyUnneeded(planter_branch) =>
+            VarSafetyStatus::LocallyUnneeded(planter_branch) => {
-                self.branch_subsumes(planter_branch, branch),
+                self.branch_subsumes(planter_branch, branch)
+            }
             VarSafetyStatus::GloballyUnneeded => true,
         }
     }
@@ -91,7 +96,9 @@ impl BranchStack {
 
             let num_branches = occurrences.num_branches;
 
-            let entry = occurrences.hits.entry(var_num)
+            let entry = occurrences
+                .hits
+                .entry(var_num)
                 .or_insert_with(|| BitVec::repeat(false, num_branches));
 
             entry.set(occurrences.current_branch, true);
@@ -105,11 +112,15 @@ impl BranchStack {
 
     pub(crate) fn current_branch_designator(&self) -> BranchDesignator {
         let branch_stack_num = self.len();
-        let branch_num = self.last()
+        let branch_num = self
+            .last()
             .map(|occurrences| occurrences.current_branch)
             .unwrap_or(0);
 
-        BranchDesignator { branch_stack_num, branch_num }
+        BranchDesignator {
+            branch_stack_num,
+            branch_num,
+        }
     }
 
     #[inline]
@@ -156,13 +167,23 @@ impl DebrayAllocator {
             match &mut self.var_data.records[var_num].allocation {
                 VarAlloc::Perm(_, ref mut allocation) => {
                     match allocation {
-                        PermVarAllocation::Done { shallow_safety, deep_safety, .. } => {
+                        PermVarAllocation::Done {
-                            if !self.branch_stack.safety_unneeded_in_branch(shallow_safety, &branch_designator) {
+                            shallow_safety,
+                            deep_safety,
+                            ..
+                        } => {
+                            if !self
+                                .branch_stack
+                                .safety_unneeded_in_branch(shallow_safety, &branch_designator)
+                            {
                                 let branch_occurrences = self.branch_stack.last_mut().unwrap();
                                 branch_occurrences.shallow_safety.insert(var_num);
                             }
 
-                            if !self.branch_stack.safety_unneeded_in_branch(deep_safety, &branch_designator) {
+                            if !self
+                                .branch_stack
+                                .safety_unneeded_in_branch(deep_safety, &branch_designator)
+                            {
                                 let branch_occurrences = self.branch_stack.last_mut().unwrap();
                                 branch_occurrences.deep_safety.insert(var_num);
                             }
@@ -182,15 +203,15 @@ impl DebrayAllocator {
     pub(crate) fn pop_branch(&mut self, depth: usize, subsumed_hits: SubsumedBranchHits) {
         let removed_branches = self.branch_stack.drain_branches(depth);
 
-        let (deep_safety, shallow_safety) = removed_branches
+        let (deep_safety, shallow_safety) = removed_branches.into_iter().fold(
-            .into_iter()
+            (BitSet::default(), BitSet::default()),
-            .fold((BitSet::default(), BitSet::default()),
             |(mut deep_safety, mut shallow_safety), branch_occurrences| {
                 deep_safety.union_with(&branch_occurrences.deep_safety);
                 shallow_safety.union_with(&branch_occurrences.shallow_safety);
 
                 (deep_safety, shallow_safety)
-                  });
+            },
+        );
 
         let branch_designator = self.branch_stack.current_branch_designator();
 
@@ -201,7 +222,7 @@ impl DebrayAllocator {
 
                 (&latest_branch.deep_safety, &latest_branch.shallow_safety)
             }
-            None => (&deep_safety, &shallow_safety)
+            None => (&deep_safety, &shallow_safety),
         };
 
         for var_num in subsumed_hits.iter().cloned() {
@@ -221,10 +242,13 @@ impl DebrayAllocator {
                     );
 
                     if running_count < num_occurrences {
-                        *allocation = PermVarAllocation::Done { shallow_safety, deep_safety };
+                        *allocation = PermVarAllocation::Done {
+                            shallow_safety,
+                            deep_safety,
+                        };
                     }
                 }
-                _ => unreachable!()
+                _ => unreachable!(),
             }
         }
 
@@ -244,9 +268,11 @@ impl DebrayAllocator {
 
     fn occurs_shallowly_in_head(&self, var_num: usize, r: usize) -> bool {
         match &self.var_data.records[var_num].allocation {
-            VarAlloc::Temp { temp_var_data, term_loc: GenContext::Head, .. } => {
+            VarAlloc::Temp {
-                temp_var_data.use_set.contains(&(GenContext::Head, r))
+                temp_var_data,
-            }
+                term_loc: GenContext::Head,
+                ..
+            } => temp_var_data.use_set.contains(&(GenContext::Head, r)),
             _ => false,
         }
     }
@@ -325,12 +351,14 @@ impl DebrayAllocator {
 
                 match &self.var_data.records[t_var].allocation {
                     VarAlloc::Temp { temp_var_data, .. } => {
-                        if !temp_var_data.use_set.contains(&(GenContext::Last(chunk_num), k)) {
+                        if !temp_var_data
+                            .use_set
+                            .contains(&(GenContext::Last(chunk_num), k))
+                        {
                             return Some((t_var, self.alloc_with_ca(t_var)));
                         }
                     }
-                    _ => {
+                    _ => {}
-                    }
                 }
 
                 None
@@ -356,7 +384,9 @@ impl DebrayAllocator {
                     self.shallow_temp_mappings.swap_remove(&k);
                     self.shallow_temp_mappings.insert(r.reg_num(), var_num);
 
-                    self.var_data.records[var_num].allocation.set_register(r.reg_num());
+                    self.var_data.records[var_num]
+                        .allocation
+                        .set_register(r.reg_num());
                     self.in_use.insert(r.reg_num());
                 }
             }
@@ -417,12 +447,9 @@ impl DebrayAllocator {
     fn in_place(&self, var_num: usize, term_loc: GenContext, r: RegType, k: usize) -> bool {
         match term_loc {
             GenContext::Head if !r.is_perm() => r.reg_num() == k,
-            _ => {
+            _ => match &self.var_data.records[var_num].allocation {
-                match &self.var_data.records[var_num].allocation {
+                &VarAlloc::Temp { temp_reg, .. } if r.reg_num() == k => temp_reg == k,
-                    &VarAlloc::Temp { temp_reg, .. } if r.reg_num() == k =>
-                        temp_reg == k,
                 _ => false,
-                }
             },
         }
     }
@@ -483,8 +510,7 @@ impl DebrayAllocator {
                     VarAlloc::Perm(p, PermVarAllocation::Pending) if *p > 0 => {
                         return Some(std::mem::replace(p, 0));
                     }
-                    _ => {
+                    _ => {}
-                    }
                 }
             } else {
                 return None;
@@ -500,8 +526,7 @@ impl DebrayAllocator {
                 *allocation = PermVarAllocation::Pending;
                 self.add_perm_to_free_list(chunk_num, var_num);
             }
-            _ => {
+            _ => {}
-            }
         }
     }
 
@@ -509,7 +534,14 @@ impl DebrayAllocator {
         let branch_designator = self.branch_stack.current_branch_designator();
 
         match &mut self.var_data.records[var_num].allocation {
-            VarAlloc::Perm(_, PermVarAllocation::Done { deep_safety, shallow_safety, .. }) => {
+            VarAlloc::Perm(
+                _,
+                PermVarAllocation::Done {
+                    deep_safety,
+                    shallow_safety,
+                    ..
+                },
+            ) => {
                 *deep_safety = VarSafetyStatus::unneeded(branch_designator);
                 *shallow_safety = VarSafetyStatus::unneeded(branch_designator);
             }
@@ -524,7 +556,14 @@ impl DebrayAllocator {
         let branch_designator = self.branch_stack.current_branch_designator();
 
         match &mut self.var_data.records[var_num].allocation {
-            VarAlloc::Perm(_, PermVarAllocation::Done { deep_safety, shallow_safety, .. }) => {
+            VarAlloc::Perm(
+                _,
+                PermVarAllocation::Done {
+                    deep_safety,
+                    shallow_safety,
+                    ..
+                },
+            ) => {
                 // GetVariable in head chunk is considered safe.
                 if lvl == Level::Deep {
                     *deep_safety = VarSafetyStatus::unneeded(branch_designator);
@@ -532,12 +571,16 @@ impl DebrayAllocator {
                 } else if term_loc == GenContext::Head {
                     *shallow_safety = VarSafetyStatus::GloballyUnneeded;
                 } else {
-                    if let Some(temp_var_num) = self.shallow_temp_mappings.get(&self.arg_c).cloned() {
+                    if let Some(temp_var_num) = self.shallow_temp_mappings.get(&self.arg_c).cloned()
+                    {
                         match &mut self.var_data.records[temp_var_num].allocation {
-                            VarAlloc::Temp { ref mut to_perm_var_num, .. } => {
+                            VarAlloc::Temp {
+                                ref mut to_perm_var_num,
+                                ..
+                            } => {
                                 *to_perm_var_num = Some(var_num);
                             }
-                            _ => unreachable!()
+                            _ => unreachable!(),
                         }
                     }
                 }
@@ -560,8 +603,18 @@ impl DebrayAllocator {
         let branch_designator = self.branch_stack.current_branch_designator();
 
         match &mut self.var_data.records[var_num].allocation {
-            VarAlloc::Perm(_, PermVarAllocation::Done { ref mut shallow_safety, .. }) => {
+            VarAlloc::Perm(
-                if !self.in_tail_position || self.branch_stack.safety_unneeded_in_branch(shallow_safety, &branch_designator) {
+                _,
+                PermVarAllocation::Done {
+                    ref mut shallow_safety,
+                    ..
+                },
+            ) => {
+                if !self.in_tail_position
+                    || self
+                        .branch_stack
+                        .safety_unneeded_in_branch(shallow_safety, &branch_designator)
+                {
                     Target::argument_to_value(r, arg_c)
                 } else {
                     *shallow_safety = VarSafetyStatus::unneeded(branch_designator);
@@ -569,7 +622,10 @@ impl DebrayAllocator {
                 }
             }
             VarAlloc::Temp { ref mut safety, .. } => {
-                if self.branch_stack.safety_unneeded_in_branch(safety, &branch_designator) {
+                if self
+                    .branch_stack
+                    .safety_unneeded_in_branch(safety, &branch_designator)
+                {
                     Target::argument_to_value(r, arg_c)
                 } else {
                     *safety = VarSafetyStatus::GloballyUnneeded;
@@ -590,8 +646,17 @@ impl DebrayAllocator {
         let branch_designator = self.branch_stack.current_branch_designator();
 
         match &mut self.var_data.records[var_num].allocation {
-            VarAlloc::Perm(_, PermVarAllocation::Done { ref mut deep_safety, .. }) => {
+            VarAlloc::Perm(
-                if self.branch_stack.safety_unneeded_in_branch(deep_safety, &branch_designator) {
+                _,
+                PermVarAllocation::Done {
+                    ref mut deep_safety,
+                    ..
+                },
+            ) => {
+                if self
+                    .branch_stack
+                    .safety_unneeded_in_branch(deep_safety, &branch_designator)
+                {
                     Target::subterm_to_value(r)
                 } else {
                     *deep_safety = VarSafetyStatus::unneeded(branch_designator);
@@ -599,7 +664,10 @@ impl DebrayAllocator {
                 }
             }
             VarAlloc::Temp { ref mut safety, .. } => {
-                if self.branch_stack.safety_unneeded_in_branch(safety, &branch_designator) {
+                if self
+                    .branch_stack
+                    .safety_unneeded_in_branch(safety, &branch_designator)
+                {
                     Target::subterm_to_value(r)
                 } else {
                     *safety = VarSafetyStatus::unneeded(branch_designator);
@@ -626,7 +694,7 @@ impl Allocator for DebrayAllocator {
             in_use: BitSet::default(),
             temp_free_list: vec![],
             perm_free_list: VecDeque::new(),
-            branch_stack: BranchStack { stack: vec![] }
+            branch_stack: BranchStack { stack: vec![] },
         }
     }
 
@@ -705,12 +773,14 @@ impl Allocator for DebrayAllocator {
             }
             r @ RegType::Perm(_) => {
                 let is_new_var = match &mut self.var_data.records[var_num].allocation {
-                    VarAlloc::Perm(_, allocation) => if allocation.pending() {
+                    VarAlloc::Perm(_, allocation) => {
+                        if allocation.pending() {
                             *allocation = PermVarAllocation::done();
                             true
                         } else {
                             false
-                    },
+                        }
+                    }
                     _ => unreachable!(),
                 };
 
@@ -828,7 +898,9 @@ impl Allocator for DebrayAllocator {
                 if !r.is_perm() && r.reg_num() == 0 {
                     self.in_use.insert(idx + 1);
                     self.shallow_temp_mappings.insert(idx + 1, var_num);
-                    self.var_data.records[var_num].allocation.set_register(idx + 1);
+                    self.var_data.records[var_num]
+                        .allocation
+                        .set_register(idx + 1);
                 }
             }
         }

src/ffi.rs

@@ -24,12 +24,12 @@ use crate::atom_table::Atom;
 use std::alloc::{alloc, Layout};
 use std::any::Any;
 use std::collections::HashMap;
-use std::error::Error;
-use std::ffi::{CString, c_void};
 use std::convert::TryFrom;
+use std::error::Error;
+use std::ffi::{c_void, CString};
 
-use libffi::low::{ffi_cif, types, CodePtr, ffi_abi_FFI_DEFAULT_ABI, prep_cif, ffi_type, type_tag};
+use libffi::low::{ffi_abi_FFI_DEFAULT_ABI, ffi_cif, ffi_type, prep_cif, type_tag, types, CodePtr};
-use libloading::{Symbol, Library};
+use libloading::{Library, Symbol};
 
 pub struct FunctionDefinition {
     pub name: String,
@@ -74,7 +74,14 @@ impl ForeignFunctionTable {
         let mut struct_type: ffi_type = Default::default();
         struct_type.type_ = type_tag::STRUCT;
         struct_type.elements = fields.as_mut_ptr();
-	self.structs.insert(name.to_string(), StructImpl { ffi_type: struct_type, fields, atom_fields});
+        self.structs.insert(
+            name.to_string(),
+            StructImpl {
+                ffi_type: struct_type,
+                fields,
+                atom_fields,
+            },
+        );
     }
 
     fn map_type_ffi(&mut self, source: &Atom) -> *mut ffi_type {
@@ -94,47 +101,59 @@ impl ForeignFunctionTable {
                 atom!("ptr") => &mut types::pointer,
                 atom!("f32") => &mut types::float,
                 atom!("f64") => &mut types::double,
-		struct_name => {
+                struct_name => match self.structs.get_mut(&*struct_name.as_str()) {
-		    match self.structs.get_mut(struct_name.as_str()) {
+                    Some(ref mut struct_type) => &mut struct_type.ffi_type,
-			Some(ref mut struct_type) => {
+                    None => unreachable!(),
-			    &mut struct_type.ffi_type
                 },
-			None => unreachable!()
-		    }
-		}
             }
         }
     }
 
-    pub(crate) fn load_library(&mut self, library_name: &str, functions: &Vec<FunctionDefinition>) -> Result<(), Box<dyn Error>> {
+    pub(crate) fn load_library(
+        &mut self,
+        library_name: &str,
+        functions: &Vec<FunctionDefinition>,
+    ) -> Result<(), Box<dyn Error>> {
         let mut ff_table: ForeignFunctionTable = Default::default();
         unsafe {
             let library = Library::new(library_name)?;
             for function in functions {
                 let symbol_name: CString = CString::new(function.name.clone())?;
-		let code_ptr: Symbol<*mut c_void> = library.get(&symbol_name.into_bytes_with_nul())?;
+                let code_ptr: Symbol<*mut c_void> =
-		let mut args: Vec<_> = function.args.iter().map(|x| self.map_type_ffi(&x)).collect();
+                    library.get(&symbol_name.into_bytes_with_nul())?;
+                let mut args: Vec<_> = function
+                    .args
+                    .iter()
+                    .map(|x| self.map_type_ffi(&x))
+                    .collect();
                 let mut cif: ffi_cif = Default::default();
                 prep_cif(
                     &mut cif,
                     ffi_abi_FFI_DEFAULT_ABI,
                     args.len(),
                     self.map_type_ffi(&function.return_value),
-		    args.as_mut_ptr()
+                    args.as_mut_ptr(),
-		).unwrap();
+                )
+                .unwrap();
 
-		let return_struct_name = if (*self.map_type_ffi(&function.return_value)).type_ as u32 == libffi::raw::FFI_TYPE_STRUCT {
+                let return_struct_name = if (*self.map_type_ffi(&function.return_value)).type_
+                    as u32
+                    == libffi::raw::FFI_TYPE_STRUCT
+                {
                     Some(function.return_value.as_str().to_string())
                 } else {
                     None
                 };
 
-		ff_table.table.insert(function.name.clone(), FunctionImpl {
+                ff_table.table.insert(
+                    function.name.clone(),
+                    FunctionImpl {
                         cif,
                         args,
                         code_ptr: CodePtr(code_ptr.into_raw().into_raw() as *mut _),
                         return_struct_name,
-		});
+                    },
+                );
             }
             std::mem::forget(library);
         }
@@ -142,21 +161,24 @@ impl ForeignFunctionTable {
         Ok(())
     }
 
-    fn build_pointer_args(args: &mut Vec<Value>, type_args: &Vec<*mut ffi_type>, structs_table: &mut HashMap<String, StructImpl>) -> Result<PointerArgs, FFIError> {
+    fn build_pointer_args(
+        args: &mut Vec<Value>,
+        type_args: &Vec<*mut ffi_type>,
+        structs_table: &mut HashMap<String, StructImpl>,
+    ) -> Result<PointerArgs, FFIError> {
         let mut pointers = Vec::with_capacity(args.len());
         let mut _memory = Vec::new();
         for i in 0..args.len() {
             let field_type = type_args[i];
             unsafe {
                 macro_rules! push_int {
-		    ($type:ty) => {
+                    ($type:ty) => {{
-			{
+                        let n: $type = <$type>::try_from(args[i].as_int()?)
-			    let n: $type = <$type>::try_from(args[i].as_int()?).map_err(|_| FFIError::ValueDontFit)?;
+                            .map_err(|_| FFIError::ValueDontFit)?;
                         let mut box_value = Box::new(n) as Box<dyn Any>;
                         pointers.push(&mut *box_value as *mut _ as *mut c_void);
                         _memory.push(box_value);
-			}
+                    }};
-		    }
                 }
 
                 match (*field_type).type_ as u32 {
@@ -173,38 +195,43 @@ impl ForeignFunctionTable {
                         let mut box_value = Box::new(n) as Box<dyn Any>;
                         pointers.push(&mut *box_value as *mut _ as *mut c_void);
                         _memory.push(box_value);
-		    },
+                    }
                     libffi::raw::FFI_TYPE_DOUBLE => {
                         let n: f64 = args[i].as_float()?;
                         let mut box_value = Box::new(n) as Box<dyn Any>;
                         pointers.push(&mut *box_value as *mut _ as *mut c_void);
                         _memory.push(box_value);
-		    },
+                    }
                     libffi::raw::FFI_TYPE_POINTER => {
                         let ptr: *mut c_void = args[i].as_ptr()?;
                         pointers.push(ptr);
-		    },
+                    }
                     libffi::raw::FFI_TYPE_STRUCT => {
-			let (mut ptr, _size, _align) = Self::build_struct(&mut args[i], structs_table)?;
+                        let (mut ptr, _size, _align) =
+                            Self::build_struct(&mut args[i], structs_table)?;
                         pointers.push(&mut *ptr as *mut _ as *mut c_void);
                         _memory.push(ptr);
-		    },
+                    }
-		    _ => return Err(FFIError::InvalidFFIType)
+                    _ => return Err(FFIError::InvalidFFIType),
                 }
             }
         }
-	Ok(PointerArgs {
+        Ok(PointerArgs { pointers, _memory })
-	    pointers,
-	    _memory
-	})
     }
 
-    fn build_struct(arg: &mut Value, structs_table: &mut HashMap<String, StructImpl>) -> Result<(Box<dyn Any>, usize, usize), FFIError> {
+    fn build_struct(
+        arg: &mut Value,
+        structs_table: &mut HashMap<String, StructImpl>,
+    ) -> Result<(Box<dyn Any>, usize, usize), FFIError> {
         unsafe {
             match arg {
                 Value::Struct(ref name, ref mut struct_args) => {
                     if let Some(ref mut struct_type) = structs_table.clone().get_mut(name) {
-		    let layout = Layout::from_size_align(struct_type.ffi_type.size, struct_type.ffi_type.alignment.into()).unwrap();
+                        let layout = Layout::from_size_align(
+                            struct_type.ffi_type.size,
+                            struct_type.ffi_type.alignment.into(),
+                        )
+                        .unwrap();
                         let align = struct_type.ffi_type.alignment as usize;
                         let size = struct_type.ffi_type.size;
                         let ptr = alloc(layout) as *mut c_void;
@@ -212,24 +239,22 @@ impl ForeignFunctionTable {
 
                         for i in 0..(struct_type.fields.len() - 1) {
                             macro_rules! try_write_int {
-			    ($type:ty) => {
+                                ($type:ty) => {{
-				{
+                                    field_ptr = field_ptr
-				    field_ptr = field_ptr.add(field_ptr.align_offset(std::mem::align_of::<$type>()));
+                                        .add(field_ptr.align_offset(std::mem::align_of::<$type>()));
-				    let n: $type = <$type>::try_from(struct_args[i].as_int()?).map_err(|_| FFIError::ValueDontFit)?;
+                                    let n: $type = <$type>::try_from(struct_args[i].as_int()?)
+                                        .map_err(|_| FFIError::ValueDontFit)?;
                                     std::ptr::write(field_ptr as *mut $type, n);
                                     field_ptr = field_ptr.add(std::mem::size_of::<$type>());
-				}
+                                }};
-			    }
                             }
 
                             macro_rules! write {
-			    ($type:ty, $value:expr) => {
+                                ($type:ty, $value:expr) => {{
-				{
                                     let data: $type = $value;
                                     std::ptr::write(field_ptr as *mut $type, data);
                                     field_ptr = field_ptr.add(align);
-				}
+                                }};
-			    }
                             }
 
                             let field = struct_type.fields[i];
@@ -242,16 +267,27 @@ impl ForeignFunctionTable {
                                 libffi::raw::FFI_TYPE_SINT32 => try_write_int!(i32),
                                 libffi::raw::FFI_TYPE_UINT64 => try_write_int!(u64),
                                 libffi::raw::FFI_TYPE_SINT64 => try_write_int!(i64),
-			    libffi::raw::FFI_TYPE_POINTER => write!(*mut c_void, struct_args[i].as_ptr()?),
+                                libffi::raw::FFI_TYPE_POINTER => {
-			    libffi::raw::FFI_TYPE_FLOAT => write!(f32, struct_args[i].as_float()? as f32),
+                                    write!(*mut c_void, struct_args[i].as_ptr()?)
-			    libffi::raw::FFI_TYPE_DOUBLE => write!(f64, struct_args[i].as_float()?),
+                                }
+                                libffi::raw::FFI_TYPE_FLOAT => {
+                                    write!(f32, struct_args[i].as_float()? as f32)
+                                }
+                                libffi::raw::FFI_TYPE_DOUBLE => {
+                                    write!(f64, struct_args[i].as_float()?)
+                                }
                                 libffi::raw::FFI_TYPE_STRUCT => {
-				let (struct_ptr, struct_size, struct_align) = Self::build_struct(&mut struct_args[i], structs_table)?;
+                                    let (struct_ptr, struct_size, struct_align) =
+                                        Self::build_struct(&mut struct_args[i], structs_table)?;
                                     field_ptr = field_ptr.add(field_ptr.align_offset(struct_align));
 
-				std::ptr::copy(& *struct_ptr as *const _ as *const c_void, field_ptr as *mut c_void, struct_size);
+                                    std::ptr::copy(
+                                        &*struct_ptr as *const _ as *const c_void,
+                                        field_ptr as *mut c_void,
+                                        struct_size,
+                                    );
                                     field_ptr = field_ptr.add(struct_size);
-			    },
+                                }
                                 _ => {
                                     unreachable!()
                                 }
@@ -262,29 +298,28 @@ impl ForeignFunctionTable {
                         return Err(FFIError::InvalidStructName);
                     }
                 }
-	    _ => return Err(FFIError::ValueCast)
+                _ => return Err(FFIError::ValueCast),
             }
         }
     }
 
     pub fn exec(&mut self, name: &str, mut args: Vec<Value>) -> Result<Value, FFIError> {
         let function_impl = self.table.get_mut(name).ok_or(FFIError::FunctionNotFound)?;
-	let mut pointer_args = Self::build_pointer_args(&mut args, &function_impl.args, &mut self.structs)?;
+        let mut pointer_args =
+            Self::build_pointer_args(&mut args, &function_impl.args, &mut self.structs)?;
 
         return unsafe {
             macro_rules! call_and_return {
-		($type:ty) => {
+                ($type:ty) => {{
-		    {
                     let mut n: Box<u8> = Box::new(0);
                     libffi::raw::ffi_call(
                         &mut function_impl.cif,
                         Some(*function_impl.code_ptr.as_safe_fun()),
                         &mut *n as *mut _ as *mut c_void,
-			    pointer_args.pointers.as_mut_ptr() as *mut *mut c_void
+                        pointer_args.pointers.as_mut_ptr() as *mut *mut c_void,
                     );
                     Ok(Value::Int(i64::from(*n)))
-		    }
+                }};
-		}
             }
 
             match (*function_impl.cif.rtype).type_ as u32 {
@@ -301,10 +336,12 @@ impl ForeignFunctionTable {
                         &mut function_impl.cif,
                         Some(*function_impl.code_ptr.as_safe_fun()),
                         &mut *n as *mut _ as *mut c_void,
-			pointer_args.pointers.as_mut_ptr() as *mut *mut c_void
+                        pointer_args.pointers.as_mut_ptr() as *mut *mut c_void,
                     );
-		    Ok(Value::Int(i64::try_from(*n).map_err(|_| FFIError::ValueDontFit)?))
+                    Ok(Value::Int(
-		},
+                        i64::try_from(*n).map_err(|_| FFIError::ValueDontFit)?,
+                    ))
+                }
                 libffi::raw::FFI_TYPE_SINT64 => call_and_return!(i64),
                 libffi::raw::FFI_TYPE_POINTER => call_and_return!(*mut c_void),
                 libffi::raw::FFI_TYPE_FLOAT => {
@@ -313,42 +350,54 @@ impl ForeignFunctionTable {
                         &mut function_impl.cif,
                         Some(*function_impl.code_ptr.as_safe_fun()),
                         &mut *n as *mut _ as *mut c_void,
-			pointer_args.pointers.as_mut_ptr() as *mut *mut c_void
+                        pointer_args.pointers.as_mut_ptr() as *mut *mut c_void,
                     );
                     Ok(Value::Float((*n).into()))
-		},
+                }
                 libffi::raw::FFI_TYPE_DOUBLE => {
                     let mut n: Box<f64> = Box::new(0.0);
                     libffi::raw::ffi_call(
                         &mut function_impl.cif,
                         Some(*function_impl.code_ptr.as_safe_fun()),
                         &mut *n as *mut _ as *mut c_void,
-			pointer_args.pointers.as_mut_ptr() as *mut *mut c_void
+                        pointer_args.pointers.as_mut_ptr() as *mut *mut c_void,
                     );
                     Ok(Value::Float(*n))
-		},
+                }
                 libffi::raw::FFI_TYPE_STRUCT => {
-		    let name = &function_impl.return_struct_name.clone().ok_or(FFIError::StructNotFound)?;
+                    let name = &function_impl
+                        .return_struct_name
+                        .clone()
+                        .ok_or(FFIError::StructNotFound)?;
                     let struct_type = self.structs.get(name).ok_or(FFIError::StructNotFound)?;
-		    let layout = Layout::from_size_align(struct_type.ffi_type.size, struct_type.ffi_type.alignment.into()).unwrap();
+                    let layout = Layout::from_size_align(
+                        struct_type.ffi_type.size,
+                        struct_type.ffi_type.alignment.into(),
+                    )
+                    .unwrap();
                     let ptr = alloc(layout) as *mut c_void;
 
                     libffi::raw::ffi_call(
                         &mut function_impl.cif,
                         Some(*function_impl.code_ptr.as_safe_fun()),
                         &mut *ptr as *mut _ as *mut c_void,
-			pointer_args.pointers.as_mut_ptr() as *mut *mut c_void
+                        pointer_args.pointers.as_mut_ptr() as *mut *mut c_void,
                     );
                     let struct_val = self.read_struct(ptr, name, struct_type);
                     drop(Box::from_raw(ptr));
                     struct_val
                 }
-	    _ => unreachable!()
+                _ => unreachable!(),
             }
         };
     }
 
-    fn read_struct(&self, ptr: *mut c_void, name: &str, struct_type: &StructImpl) -> Result<Value, FFIError> {
+    fn read_struct(
+        &self,
+        ptr: *mut c_void,
+        name: &str,
+        struct_type: &StructImpl,
+    ) -> Result<Value, FFIError> {
         unsafe {
             let mut returns = Vec::new();
             let mut field_ptr = ptr;
@@ -357,14 +406,13 @@ impl ForeignFunctionTable {
                 let field = struct_type.fields[i];
 
                 macro_rules! read_and_push_int {
-		    ($type:ty) => {
+                    ($type:ty) => {{
-			{
+                        field_ptr =
-			    field_ptr = field_ptr.add(field_ptr.align_offset(std::mem::align_of::<$type>()));
+                            field_ptr.add(field_ptr.align_offset(std::mem::align_of::<$type>()));
                         let n = std::ptr::read(field_ptr as *mut $type);
                         returns.push(Value::Int(i64::from(n)));
                         field_ptr = field_ptr.add(std::mem::size_of::<$type>());
-			}
+                    }};
-		    }
                 }
 
                 match (*field).type_ as u32 {
@@ -375,21 +423,28 @@ impl ForeignFunctionTable {
                     libffi::raw::FFI_TYPE_UINT32 => read_and_push_int!(u32),
                     libffi::raw::FFI_TYPE_SINT32 => read_and_push_int!(i32),
                     libffi::raw::FFI_TYPE_UINT64 => {
-			field_ptr = field_ptr.add(field_ptr.align_offset(std::mem::align_of::<u64>()));
+                        field_ptr =
+                            field_ptr.add(field_ptr.align_offset(std::mem::align_of::<u64>()));
                         let n = std::ptr::read(field_ptr as *mut u64);
-			returns.push(Value::Int(i64::try_from(n).map_err(|_| FFIError::ValueDontFit)?));
+                        returns.push(Value::Int(
+                            i64::try_from(n).map_err(|_| FFIError::ValueDontFit)?,
+                        ));
                         field_ptr = field_ptr.add(std::mem::size_of::<u64>());
-		    },
+                    }
                     libffi::raw::FFI_TYPE_SINT64 => read_and_push_int!(i64),
                     libffi::raw::FFI_TYPE_POINTER => read_and_push_int!(i64),
                     libffi::raw::FFI_TYPE_STRUCT => {
                         let substruct = struct_type.atom_fields[i].as_str();
-			let struct_type = self.structs.get(substruct).ok_or(FFIError::StructNotFound)?;
+                        let struct_type = self
-			field_ptr = field_ptr.add(field_ptr.align_offset(struct_type.ffi_type.alignment as usize));
+                            .structs
-			let struct_val = self.read_struct(field_ptr, substruct, struct_type);
+                            .get(&*substruct)
+                            .ok_or(FFIError::StructNotFound)?;
+                        field_ptr = field_ptr
+                            .add(field_ptr.align_offset(struct_type.ffi_type.alignment as usize));
+                        let struct_val = self.read_struct(field_ptr, &*substruct, struct_type);
                         returns.push(struct_val?);
                         field_ptr = field_ptr.add(struct_type.ffi_type.size);
-		    },
+                    }
                     _ => {
                         unreachable!()
                     }
@@ -428,7 +483,7 @@ impl Value {
         match self {
             Value::CString(ref mut cstr) => Ok(&mut *cstr as *mut _ as *mut c_void),
             Value::Int(n) => Ok(*n as *mut c_void),
-	    _ => Err(FFIError::ValueCast)
+            _ => Err(FFIError::ValueCast),
         }
     }
 }

src/forms.rs

@@ -7,8 +7,8 @@ use crate::machine::loader::PredicateQueue;
 use crate::machine::machine_errors::*;
 use crate::machine::machine_indices::*;
 use crate::parser::ast::*;
-use crate::parser::parser::CompositeOpDesc;
 use crate::parser::dashu::{Integer, Rational};
+use crate::parser::parser::CompositeOpDesc;
 use crate::types::*;
 
 use fxhash::FxBuildHasher;
@@ -58,7 +58,7 @@ impl AppendOrPrepend {
 #[derive(Debug, Clone, Copy)]
 pub enum VarComparison {
     Indistinct,
-    Distinct
+    Distinct,
 }
 
 #[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
@@ -153,11 +153,14 @@ impl DerefMut for ChunkedTermVec {
 impl ChunkedTermVec {
     #[inline]
     pub fn new() -> Self {
-        Self { chunk_vec: VecDeque::new() }
+        Self {
+            chunk_vec: VecDeque::new(),
+        }
     }
 
     pub fn reserve_branch(&mut self, capacity: usize) {
-        self.chunk_vec.push_back(ChunkedTerms::Branch(Vec::with_capacity(capacity)));
+        self.chunk_vec
+            .push_back(ChunkedTerms::Branch(Vec::with_capacity(capacity)));
     }
 
     pub fn push_branch_arm(&mut self, branch: VecDeque<ChunkedTerms>) {
@@ -173,19 +176,22 @@ impl ChunkedTermVec {
 
     #[inline]
     pub fn add_chunk(&mut self) {
-        self.chunk_vec.push_back(ChunkedTerms::Chunk(VecDeque::from(vec![])));
+        self.chunk_vec
+            .push_back(ChunkedTerms::Chunk(VecDeque::from(vec![])));
     }
 
     pub fn push_chunk_term(&mut self, term: QueryTerm) {
         match self.chunk_vec.back_mut() {
             Some(ChunkedTerms::Branch(_)) => {
-                self.chunk_vec.push_back(ChunkedTerms::Chunk(VecDeque::from(vec![term])));
+                self.chunk_vec
+                    .push_back(ChunkedTerms::Chunk(VecDeque::from(vec![term])));
             }
             Some(ChunkedTerms::Chunk(chunk)) => {
                 chunk.push_back(term);
             }
             None => {
-                self.chunk_vec.push_back(ChunkedTerms::Chunk(VecDeque::from(vec![term])));
+                self.chunk_vec
+                    .push_back(ChunkedTerms::Chunk(VecDeque::from(vec![term])));
             }
         }
     }
@@ -266,7 +272,6 @@ impl ClauseInfo for Term {
     fn name(&self) -> Option<Atom> {
         match self {
             Term::Clause(_, name, terms) => {
-
                 match name {
                     atom!(":-") => {
                         match terms.len() {
@@ -285,7 +290,7 @@ impl ClauseInfo for Term {
 
     fn arity(&self) -> usize {
         match self {
-            Term::Clause(_, name, terms) => match name.as_str() {
+            Term::Clause(_, name, terms) => match &*name.as_str() {
                 ":-" => match terms.len() {
                     1 => 0,
                     2 => terms[0].arity(),
@@ -410,7 +415,6 @@ pub(crate) fn fixity(spec: u32) -> Fixity {
     }
 }
 
-
 impl OpDecl {
     #[inline]
     pub(crate) fn new(op_desc: OpDesc, name: Atom) -> Self {
@@ -477,35 +481,27 @@ pub enum AtomOrString {
 
 impl AtomOrString {
     #[inline]
-    pub fn as_atom(&self, atom_tbl: &mut AtomTable) -> Atom {
+    pub fn as_atom(&self, atom_tbl: &AtomTable) -> Atom {
         match self {
-            &AtomOrString::Atom(atom) => {
+            &AtomOrString::Atom(atom) => atom,
-                atom
+            AtomOrString::String(string) => AtomTable::build_with(atom_tbl, &string),
-            }
-            AtomOrString::String(string) => {
-                atom_tbl.build_with(&string)
-            }
         }
     }
 
     #[inline]
-    pub fn as_str(&self) -> &str {
+    pub fn as_str(&self) -> AtomString<'_> {
         match self {
-            AtomOrString::Atom(atom) if atom == &atom!("[]") => "",
+            AtomOrString::Atom(atom) if atom == &atom!("[]") => AtomString::Static(""),
             AtomOrString::Atom(atom) => atom.as_str(),
-            AtomOrString::String(string) => string.as_str(),
+            AtomOrString::String(string) => AtomString::Static(string.as_str()),
         }
     }
 
     #[inline]
     pub fn to_string(self) -> String {
         match self {
-            AtomOrString::Atom(atom) => {
+            AtomOrString::Atom(atom) => atom.as_str().to_owned(),
-                atom.as_str().to_owned()
+            AtomOrString::String(string) => string,
-            }
-            AtomOrString::String(string) => {
-                string
-            }
         }
     }
 }
@@ -561,9 +557,7 @@ pub(crate) fn fetch_op_spec(name: Atom, arity: usize, op_dir: &OpDir) -> Option<
                 }
             })
         }
-        0 => {
+        0 => fetch_atom_op_spec(name, None, op_dir),
-            fetch_atom_op_spec(name, None, op_dir)
-        }
         _ => None,
     }
 }
@@ -595,10 +589,7 @@ pub struct Module {
 
 // Module's and related types are defined in forms.
 impl Module {
-    pub(crate) fn new(
+    pub(crate) fn new(module_decl: ModuleDecl, listing_src: ListingSource) -> Self {
-        module_decl: ModuleDecl,
-        listing_src: ListingSource,
-    ) -> Self {
         Module {
             module_decl,
             code_dir: CodeDir::with_hasher(FxBuildHasher::default()),
@@ -620,7 +611,7 @@ impl Module {
             meta_predicates: MetaPredicateDir::with_hasher(FxBuildHasher::default()),
             extensible_predicates: ExtensiblePredicates::with_hasher(FxBuildHasher::default()),
             local_extensible_predicates: LocalExtensiblePredicates::with_hasher(
-                FxBuildHasher::default()
+                FxBuildHasher::default(),
             ),
             listing_src: ListingSource::DynamicallyGenerated,
         }
@@ -923,8 +914,10 @@ impl PredicateInfo {
 
     #[inline]
     pub(crate) fn must_retract_local_clauses(&self, is_cross_module_clause: bool) -> bool {
-        self.is_extensible && self.has_clauses && !self.is_discontiguous &&
+        self.is_extensible
-            !(self.is_multifile && is_cross_module_clause)
+            && self.has_clauses
+            && !self.is_discontiguous
+            && !(self.is_multifile && is_cross_module_clause)
     }
 }
 
@@ -1013,19 +1006,17 @@ impl PredicateSkeleton {
         &mut self,
         clause_clause_loc: usize,
     ) -> Option<usize> {
-        let search_result = self.core.clause_clause_locs
+        let search_result = self.core.clause_clause_locs.make_contiguous()
-            .make_contiguous()[0..self.core.clause_assert_margin]
+            [0..self.core.clause_assert_margin]
             .binary_search_by(|loc| clause_clause_loc.cmp(&loc));
 
         match search_result {
             Ok(loc) => Some(loc),
-            Err(_) => {
+            Err(_) => self.core.clause_clause_locs.make_contiguous()
-                self.core.clause_clause_locs
+                [self.core.clause_assert_margin..]
-                    .make_contiguous()[self.core.clause_assert_margin..]
                 .binary_search_by(|loc| loc.cmp(&clause_clause_loc))
                 .map(|loc| loc + self.core.clause_assert_margin)
-                    .ok()
+                .ok(),
-            }
         }
     }
 }

src/heap_iter.rs

@@ -73,12 +73,8 @@ impl IterStackLoc {
     #[inline]
     pub fn as_ref(self) -> Ref {
         match self.heap_or_stack() {
-            HeapOrStackTag::Heap => {
+            HeapOrStackTag::Heap => Ref::heap_cell(self.value() as usize),
-                Ref::heap_cell(self.value() as usize)
+            HeapOrStackTag::Stack => Ref::stack_cell(self.value() as usize),
-            }
-            HeapOrStackTag::Stack => {
-                Ref::stack_cell(self.value() as usize)
-            }
         }
     }
 }
@@ -158,24 +154,16 @@ impl<'a> StackfulPreOrderHeapIter<'a> {
     #[inline]
     pub fn read_cell_mut(&mut self, loc: IterStackLoc) -> &mut HeapCellValue {
         match loc.heap_or_stack() {
-            HeapOrStackTag::Heap => {
+            HeapOrStackTag::Heap => &mut self.heap[loc.value() as usize],
-                &mut self.heap[loc.value() as usize]
+            HeapOrStackTag::Stack => &mut self.machine_stack[loc.value() as usize],
-            }
-            HeapOrStackTag::Stack => {
-                &mut self.machine_stack[loc.value() as usize]
-            }
         }
     }
 
     #[inline]
     pub fn read_cell(&self, loc: IterStackLoc) -> HeapCellValue {
         match loc.heap_or_stack() {
-            HeapOrStackTag::Heap => {
+            HeapOrStackTag::Heap => self.heap[loc.value() as usize],
-                self.heap[loc.value() as usize]
+            HeapOrStackTag::Stack => self.machine_stack[loc.value() as usize],
-            }
-            HeapOrStackTag::Stack => {
-                self.machine_stack[loc.value() as usize]
-            }
         }
     }
 
@@ -228,7 +216,10 @@ impl<'a> StackfulPreOrderHeapIter<'a> {
 
         if !cell.get_mark_bit() {
             cell.set_mark_bit(true);
-            self.stack.push(IterStackLoc::iterable_loc(loc.value() as usize, loc.heap_or_stack()));
+            self.stack.push(IterStackLoc::iterable_loc(
+                loc.value() as usize,
+                loc.heap_or_stack(),
+            ));
         }
     }
 
@@ -236,7 +227,10 @@ impl<'a> StackfulPreOrderHeapIter<'a> {
         while let Some(h) = self.stack.pop() {
             if h.is_pending_mark() {
                 self.push_if_unmarked(h);
-                self.stack.push(IterStackLoc::mark_loc(h.value() as usize, h.heap_or_stack()));
+                self.stack.push(IterStackLoc::mark_loc(
+                    h.value() as usize,
+                    h.heap_or_stack(),
+                ));
 
                 self.forward_if_referent_marked(h);
                 continue;
@@ -508,7 +502,6 @@ mod tests {
     use super::*;
     use crate::machine::mock_wam::*;
 
-
     #[test]
     fn heap_stackless_iter_tests() {
         let mut wam = MockWAM::new();
@@ -629,12 +622,12 @@ mod tests {
         {
             wam.machine_st.heap.push(heap_loc_as_cell!(0));
 
-            let mut iter = stackless_preorder_iter(
+            let mut iter = stackless_preorder_iter(&mut wam.machine_st.heap, heap_loc_as_cell!(0));
-                &mut wam.machine_st.heap,
-                heap_loc_as_cell!(0),
-            );
 
-            assert_eq!(unmark_cell_bits!(iter.next().unwrap()), heap_loc_as_cell!(0));
+            assert_eq!(
+                unmark_cell_bits!(iter.next().unwrap()),
+                heap_loc_as_cell!(0)
+            );
             assert_eq!(iter.next(), None);
         }
 
@@ -650,10 +643,7 @@ mod tests {
         wam.machine_st.heap.push(empty_list_as_cell!());
 
         {
-            let mut iter = stackless_preorder_iter(
+            let mut iter = stackless_preorder_iter(&mut wam.machine_st.heap, heap_loc_as_cell!(0));
-                &mut wam.machine_st.heap,
-                heap_loc_as_cell!(0),
-            );
 
             assert_eq!(
                 unmark_cell_bits!(iter.next().unwrap()),
@@ -688,10 +678,7 @@ mod tests {
         wam.machine_st.heap.push(heap_loc_as_cell!(0));
 
         {
-            let mut iter = stackless_preorder_iter(
+            let mut iter = stackless_preorder_iter(&mut wam.machine_st.heap, heap_loc_as_cell!(0));
-                &mut wam.machine_st.heap,
-                heap_loc_as_cell!(0),
-            );
 
             assert_eq!(
                 unmark_cell_bits!(iter.next().unwrap()),
@@ -721,7 +708,8 @@ mod tests {
 
         // first a 'dangling' partial string, later modified to be a two-part complete string,
         // then a three-part cyclic string involving an uncompacted list of chars.
-        let pstr_var_cell = put_partial_string(&mut wam.machine_st.heap, "abc ", &mut wam.machine_st.atom_tbl);
+        let pstr_var_cell =
+            put_partial_string(&mut wam.machine_st.heap, "abc ", &wam.machine_st.atom_tbl);
         let pstr_cell = wam.machine_st.heap[pstr_var_cell.get_value() as usize];
 
         {
@@ -742,11 +730,8 @@ mod tests {
         wam.machine_st.heap.pop();
         wam.machine_st.heap.push(pstr_loc_as_cell!(2));
 
-        let pstr_second_var_cell = put_partial_string(
+        let pstr_second_var_cell =
-            &mut wam.machine_st.heap,
+            put_partial_string(&mut wam.machine_st.heap, "def", &wam.machine_st.atom_tbl);
-            "def",
-            &mut wam.machine_st.atom_tbl,
-        );
 
         let pstr_second_cell = wam.machine_st.heap[pstr_second_var_cell.get_value() as usize];
 
@@ -771,13 +756,12 @@ mod tests {
         wam.machine_st.heap.pop();
         wam.machine_st.heap.push(pstr_loc_as_cell!(4));
         wam.machine_st.heap.push(pstr_offset_as_cell!(0));
-        wam.machine_st.heap.push(fixnum_as_cell!(Fixnum::build_with(2)));
+        wam.machine_st
+            .heap
+            .push(fixnum_as_cell!(Fixnum::build_with(2)));
 
         {
-            let mut iter = stackless_preorder_iter(
+            let mut iter = stackless_preorder_iter(&mut wam.machine_st.heap, pstr_loc_as_cell!(4));
-                &mut wam.machine_st.heap,
-                pstr_loc_as_cell!(4),
-            );
 
             let pstr_offset_cell = pstr_offset_as_cell!(0);
 
@@ -789,19 +773,35 @@ mod tests {
         }
 
         assert_eq!(unmark_cell_bits!(wam.machine_st.heap[0]), pstr_cell);
-        assert_eq!(unmark_cell_bits!(wam.machine_st.heap[1]), pstr_loc_as_cell!(2));
+        assert_eq!(
+            unmark_cell_bits!(wam.machine_st.heap[1]),
+            pstr_loc_as_cell!(2)
+        );
         assert_eq!(unmark_cell_bits!(wam.machine_st.heap[2]), pstr_second_cell);
-        assert_eq!(unmark_cell_bits!(wam.machine_st.heap[3]), pstr_loc_as_cell!(4));
+        assert_eq!(
-        assert_eq!(unmark_cell_bits!(wam.machine_st.heap[4]), pstr_offset_as_cell!(0));
+            unmark_cell_bits!(wam.machine_st.heap[3]),
-        assert_eq!(unmark_cell_bits!(wam.machine_st.heap[5]), fixnum_as_cell!(Fixnum::build_with(2)));
+            pstr_loc_as_cell!(4)
+        );
+        assert_eq!(
+            unmark_cell_bits!(wam.machine_st.heap[4]),
+            pstr_offset_as_cell!(0)
+        );
+        assert_eq!(
+            unmark_cell_bits!(wam.machine_st.heap[5]),
+            fixnum_as_cell!(Fixnum::build_with(2))
+        );
 
         wam.machine_st.heap.truncate(4);
 
         wam.machine_st.heap.pop();
-        wam.machine_st.heap.push(pstr_loc_as_cell!(wam.machine_st.heap.len() + 1));
+        wam.machine_st
+            .heap
+            .push(pstr_loc_as_cell!(wam.machine_st.heap.len() + 1));
 
         wam.machine_st.heap.push(pstr_offset_as_cell!(0));
-        wam.machine_st.heap.push(fixnum_as_cell!(Fixnum::build_with(0i64)));
+        wam.machine_st
+            .heap
+            .push(fixnum_as_cell!(Fixnum::build_with(0i64)));
 
         {
             let mut iter = stackless_preorder_iter(&mut wam.machine_st.heap, pstr_loc_as_cell!(0));
@@ -819,7 +819,9 @@ mod tests {
         all_cells_unmarked(&wam.machine_st.heap);
 
         wam.machine_st.heap.pop();
-        wam.machine_st.heap.push(fixnum_as_cell!(Fixnum::build_with(1i64)));
+        wam.machine_st
+            .heap
+            .push(fixnum_as_cell!(Fixnum::build_with(1i64)));
 
         {
             let mut iter = stackless_preorder_iter(&mut wam.machine_st.heap, pstr_loc_as_cell!(0));
@@ -827,8 +829,14 @@ mod tests {
             assert_eq!(unmark_cell_bits!(iter.next().unwrap()), pstr_cell);
             assert_eq!(unmark_cell_bits!(iter.next().unwrap()), pstr_second_cell);
 
-            assert_eq!(unmark_cell_bits!(iter.next().unwrap()), pstr_offset_as_cell!(0));
+            assert_eq!(
-            assert_eq!(unmark_cell_bits!(iter.next().unwrap()), pstr_offset_as_cell!(0));
+                unmark_cell_bits!(iter.next().unwrap()),
+                pstr_offset_as_cell!(0)
+            );
+            assert_eq!(
+                unmark_cell_bits!(iter.next().unwrap()),
+                pstr_offset_as_cell!(0)
+            );
 
             assert_eq!(iter.next(), None);
 
@@ -1059,10 +1067,22 @@ mod tests {
 
         all_cells_unmarked(&wam.machine_st.heap);
 
-        assert_eq!(unmark_cell_bits!(wam.machine_st.heap[0]), heap_loc_as_cell!(1));
+        assert_eq!(
-        assert_eq!(unmark_cell_bits!(wam.machine_st.heap[1]), heap_loc_as_cell!(2));
+            unmark_cell_bits!(wam.machine_st.heap[0]),
-        assert_eq!(unmark_cell_bits!(wam.machine_st.heap[2]), heap_loc_as_cell!(3));
+            heap_loc_as_cell!(1)
-        assert_eq!(unmark_cell_bits!(wam.machine_st.heap[3]), heap_loc_as_cell!(3));
+        );
+        assert_eq!(
+            unmark_cell_bits!(wam.machine_st.heap[1]),
+            heap_loc_as_cell!(2)
+        );
+        assert_eq!(
+            unmark_cell_bits!(wam.machine_st.heap[2]),
+            heap_loc_as_cell!(3)
+        );
+        assert_eq!(
+            unmark_cell_bits!(wam.machine_st.heap[3]),
+            heap_loc_as_cell!(3)
+        );
 
         wam.machine_st.heap.clear();
 
@@ -1089,9 +1109,18 @@ mod tests {
 
         all_cells_unmarked(&wam.machine_st.heap);
 
-        assert_eq!(unmark_cell_bits!(wam.machine_st.heap[0]), list_loc_as_cell!(1));
+        assert_eq!(
-        assert_eq!(unmark_cell_bits!(wam.machine_st.heap[1]), list_loc_as_cell!(1));
+            unmark_cell_bits!(wam.machine_st.heap[0]),
-        assert_eq!(unmark_cell_bits!(wam.machine_st.heap[2]), list_loc_as_cell!(1));
+            list_loc_as_cell!(1)
+        );
+        assert_eq!(
+            unmark_cell_bits!(wam.machine_st.heap[1]),
+            list_loc_as_cell!(1)
+        );
+        assert_eq!(
+            unmark_cell_bits!(wam.machine_st.heap[2]),
+            list_loc_as_cell!(1)
+        );
 
         wam.machine_st.heap.clear();
 
@@ -1202,37 +1231,109 @@ mod tests {
             assert_eq!(iter.next(), None);
         }
 
-        assert_eq!(unmark_cell_bits!(wam.machine_st.heap[0]), list_loc_as_cell!(1));
+        assert_eq!(
-        assert_eq!(unmark_cell_bits!(wam.machine_st.heap[1]), heap_loc_as_cell!(1));
+            unmark_cell_bits!(wam.machine_st.heap[0]),
-        assert_eq!(unmark_cell_bits!(wam.machine_st.heap[2]), heap_loc_as_cell!(3));
+            list_loc_as_cell!(1)
-        assert_eq!(unmark_cell_bits!(wam.machine_st.heap[3]), list_loc_as_cell!(4));
+        );
-        assert_eq!(unmark_cell_bits!(wam.machine_st.heap[4]), str_loc_as_cell!(6));
+        assert_eq!(
-        assert_eq!(unmark_cell_bits!(wam.machine_st.heap[5]), heap_loc_as_cell!(8));
+            unmark_cell_bits!(wam.machine_st.heap[1]),
-        assert_eq!(unmark_cell_bits!(wam.machine_st.heap[6]), atom_as_cell!(f_atom, 1));
+            heap_loc_as_cell!(1)
-        assert_eq!(unmark_cell_bits!(wam.machine_st.heap[7]), heap_loc_as_cell!(11));
+        );
-        assert_eq!(unmark_cell_bits!(wam.machine_st.heap[8]), list_loc_as_cell!(9));
+        assert_eq!(
-        assert_eq!(unmark_cell_bits!(wam.machine_st.heap[9]), heap_loc_as_cell!(9));
+            unmark_cell_bits!(wam.machine_st.heap[2]),
-        assert_eq!(unmark_cell_bits!(wam.machine_st.heap[10]), empty_list_as_cell!());
+            heap_loc_as_cell!(3)
-        assert_eq!(unmark_cell_bits!(wam.machine_st.heap[11]), attr_var_as_cell!(11));
+        );
-        assert_eq!(unmark_cell_bits!(wam.machine_st.heap[12]), heap_loc_as_cell!(13));
+        assert_eq!(
-        assert_eq!(unmark_cell_bits!(wam.machine_st.heap[13]), list_loc_as_cell!(14));
+            unmark_cell_bits!(wam.machine_st.heap[3]),
-        assert_eq!(unmark_cell_bits!(wam.machine_st.heap[14]), str_loc_as_cell!(16));
+            list_loc_as_cell!(4)
-        assert_eq!(unmark_cell_bits!(wam.machine_st.heap[15]), heap_loc_as_cell!(19));
+        );
-        assert_eq!(unmark_cell_bits!(wam.machine_st.heap[16]), atom_as_cell!(clpz_atom, 2));
+        assert_eq!(
-        assert_eq!(unmark_cell_bits!(wam.machine_st.heap[17]), atom_as_cell!(a_atom));
+            unmark_cell_bits!(wam.machine_st.heap[4]),
-        assert_eq!(unmark_cell_bits!(wam.machine_st.heap[18]), atom_as_cell!(b_atom));
+            str_loc_as_cell!(6)
-        assert_eq!(unmark_cell_bits!(wam.machine_st.heap[19]), list_loc_as_cell!(20));
+        );
-        assert_eq!(unmark_cell_bits!(wam.machine_st.heap[20]), str_loc_as_cell!(22));
+        assert_eq!(
-        assert_eq!(unmark_cell_bits!(wam.machine_st.heap[21]), empty_list_as_cell!());
+            unmark_cell_bits!(wam.machine_st.heap[5]),
-        assert_eq!(unmark_cell_bits!(wam.machine_st.heap[22]), atom_as_cell!(p_atom, 1));
+            heap_loc_as_cell!(8)
-        assert_eq!(unmark_cell_bits!(wam.machine_st.heap[23]), heap_loc_as_cell!(23));
+        );
+        assert_eq!(
+            unmark_cell_bits!(wam.machine_st.heap[6]),
+            atom_as_cell!(f_atom, 1)
+        );
+        assert_eq!(
+            unmark_cell_bits!(wam.machine_st.heap[7]),
+            heap_loc_as_cell!(11)
+        );
+        assert_eq!(
+            unmark_cell_bits!(wam.machine_st.heap[8]),
+            list_loc_as_cell!(9)
+        );
+        assert_eq!(
+            unmark_cell_bits!(wam.machine_st.heap[9]),
+            heap_loc_as_cell!(9)
+        );
+        assert_eq!(
+            unmark_cell_bits!(wam.machine_st.heap[10]),
+            empty_list_as_cell!()
+        );
+        assert_eq!(
+            unmark_cell_bits!(wam.machine_st.heap[11]),
+            attr_var_as_cell!(11)
+        );
+        assert_eq!(
+            unmark_cell_bits!(wam.machine_st.heap[12]),
+            heap_loc_as_cell!(13)
+        );
+        assert_eq!(
+            unmark_cell_bits!(wam.machine_st.heap[13]),
+            list_loc_as_cell!(14)
+        );
+        assert_eq!(
+            unmark_cell_bits!(wam.machine_st.heap[14]),
+            str_loc_as_cell!(16)
+        );
+        assert_eq!(
+            unmark_cell_bits!(wam.machine_st.heap[15]),
+            heap_loc_as_cell!(19)
+        );
+        assert_eq!(
+            unmark_cell_bits!(wam.machine_st.heap[16]),
+            atom_as_cell!(clpz_atom, 2)
+        );
+        assert_eq!(
+            unmark_cell_bits!(wam.machine_st.heap[17]),
+            atom_as_cell!(a_atom)
+        );
+        assert_eq!(
+            unmark_cell_bits!(wam.machine_st.heap[18]),
+            atom_as_cell!(b_atom)
+        );
+        assert_eq!(
+            unmark_cell_bits!(wam.machine_st.heap[19]),
+            list_loc_as_cell!(20)
+        );
+        assert_eq!(
+            unmark_cell_bits!(wam.machine_st.heap[20]),
+            str_loc_as_cell!(22)
+        );
+        assert_eq!(
+            unmark_cell_bits!(wam.machine_st.heap[21]),
+            empty_list_as_cell!()
+        );
+        assert_eq!(
+            unmark_cell_bits!(wam.machine_st.heap[22]),
+            atom_as_cell!(p_atom, 1)
+        );
+        assert_eq!(
+            unmark_cell_bits!(wam.machine_st.heap[23]),
+            heap_loc_as_cell!(23)
+        );
 
         wam.machine_st.heap.clear();
 
         {
             let mut iter = stackless_preorder_iter(
                 &mut wam.machine_st.heap,
-                fixnum_as_cell!(Fixnum::build_with(0))
+                fixnum_as_cell!(Fixnum::build_with(0)),
             );
 
             assert_eq!(
@@ -1256,10 +1357,7 @@ mod tests {
         wam.machine_st.heap.push(atom_as_cell!(atom!("y")));
 
         {
-            let mut iter = stackless_preorder_iter(
+            let mut iter = stackless_preorder_iter(&mut wam.machine_st.heap, str_loc_as_cell!(1));
-                &mut wam.machine_st.heap,
-                str_loc_as_cell!(1),
-            );
 
             assert_eq!(
                 unmark_cell_bits!(iter.next().unwrap()),
@@ -1271,10 +1369,7 @@ mod tests {
                 atom_as_cell!(atom!("y"))
             );
 
-            assert_eq!(
+            assert_eq!(unmark_cell_bits!(iter.next().unwrap()), str_loc_as_cell!(1));
-                unmark_cell_bits!(iter.next().unwrap()),
-                str_loc_as_cell!(1)
-            );
 
             assert!(iter.next().is_none());
         }
@@ -1288,10 +1383,7 @@ mod tests {
         wam.machine_st.heap.push(atom_as_cell!(atom!("y")));
 
         {
-            let mut iter = stackless_preorder_iter(
+            let mut iter = stackless_preorder_iter(&mut wam.machine_st.heap, str_loc_as_cell!(0));
-                &mut wam.machine_st.heap,
-                str_loc_as_cell!(0),
-            );
 
             assert_eq!(
                 unmark_cell_bits!(iter.next().unwrap()),
@@ -1303,10 +1395,7 @@ mod tests {
                 atom_as_cell!(atom!("y"))
             );
 
-            assert_eq!(
+            assert_eq!(unmark_cell_bits!(iter.next().unwrap()), str_loc_as_cell!(0));
-                unmark_cell_bits!(iter.next().unwrap()),
-                str_loc_as_cell!(0)
-            );
 
             assert!(iter.next().is_none());
         }
@@ -1327,10 +1416,7 @@ mod tests {
         wam.machine_st.heap.push(empty_list_as_cell!());
 
         {
-            let mut iter = stackless_preorder_iter(
+            let mut iter = stackless_preorder_iter(&mut wam.machine_st.heap, heap_loc_as_cell!(7));
-                &mut wam.machine_st.heap,
-                heap_loc_as_cell!(7),
-            );
 
             assert_eq!(
                 unmark_cell_bits!(iter.next().unwrap()),
@@ -1390,10 +1476,7 @@ mod tests {
         wam.machine_st.heap.push(heap_loc_as_cell!(1));
 
         {
-            let mut iter = stackless_preorder_iter(
+            let mut iter = stackless_preorder_iter(&mut wam.machine_st.heap, str_loc_as_cell!(0));
-                &mut wam.machine_st.heap,
-                str_loc_as_cell!(0),
-            );
 
             assert_eq!(
                 unmark_cell_bits!(iter.next().unwrap()),
@@ -1462,7 +1545,8 @@ mod tests {
         let a_atom = atom!("a");
         let b_atom = atom!("b");
 
-        wam.machine_st.heap
+        wam.machine_st
+            .heap
             .extend(functor!(f_atom, [atom(a_atom), atom(b_atom)]));
 
         {
@@ -1686,7 +1770,8 @@ mod tests {
         // two-part complete string, then a three-part cyclic string
         // involving an uncompacted list of chars.
 
-        let pstr_var_cell = put_partial_string(&mut wam.machine_st.heap, "abc ", &mut wam.machine_st.atom_tbl);
+        let pstr_var_cell =
+            put_partial_string(&mut wam.machine_st.heap, "abc ", &wam.machine_st.atom_tbl);
         let pstr_cell = wam.machine_st.heap[pstr_var_cell.get_value() as usize];
 
         {
@@ -1710,7 +1795,8 @@ mod tests {
         wam.machine_st.heap.pop();
         wam.machine_st.heap.push(heap_loc_as_cell!(2));
 
-        let pstr_second_var_cell = put_partial_string(&mut wam.machine_st.heap, "def", &mut wam.machine_st.atom_tbl);
+        let pstr_second_var_cell =
+            put_partial_string(&mut wam.machine_st.heap, "def", &wam.machine_st.atom_tbl);
         let pstr_second_cell = wam.machine_st.heap[pstr_second_var_cell.get_value() as usize];
 
         {
@@ -1731,10 +1817,14 @@ mod tests {
         }
 
         wam.machine_st.heap.pop();
-        wam.machine_st.heap.push(pstr_loc_as_cell!(wam.machine_st.heap.len() + 1));
+        wam.machine_st
+            .heap
+            .push(pstr_loc_as_cell!(wam.machine_st.heap.len() + 1));
 
         wam.machine_st.heap.push(pstr_offset_as_cell!(0));
-        wam.machine_st.heap.push(fixnum_as_cell!(Fixnum::build_with(0i64)));
+        wam.machine_st
+            .heap
+            .push(fixnum_as_cell!(Fixnum::build_with(0i64)));
 
         {
             let mut iter = stackful_preorder_iter(
@@ -1750,7 +1840,10 @@ mod tests {
             assert_eq!(unmark_cell_bits!(iter.next().unwrap()), pstr_cell);
             assert_eq!(unmark_cell_bits!(iter.next().unwrap()), pstr_second_cell);
             assert_eq!(unmark_cell_bits!(iter.next().unwrap()), pstr_offset_cell);
-            assert_eq!(iter.next().unwrap(), fixnum_as_cell!(Fixnum::build_with(0i64)));
+            assert_eq!(
+                iter.next().unwrap(),
+                fixnum_as_cell!(Fixnum::build_with(0i64))
+            );
 
             assert_eq!(iter.next(), None);
         }
@@ -1764,7 +1857,9 @@ mod tests {
         */
 
         wam.machine_st.heap.pop();
-        wam.machine_st.heap.push(fixnum_as_cell!(Fixnum::build_with(1i64)));
+        wam.machine_st
+            .heap
+            .push(fixnum_as_cell!(Fixnum::build_with(1i64)));
 
         {
             let mut iter = stackful_preorder_iter(
@@ -1781,13 +1876,19 @@ mod tests {
             assert_eq!(unmark_cell_bits!(iter.next().unwrap()), pstr_second_cell);
 
             assert_eq!(unmark_cell_bits!(iter.next().unwrap()), pstr_offset_cell);
-            assert_eq!(iter.next().unwrap(), fixnum_as_cell!(Fixnum::build_with(1i64)));
+            assert_eq!(
+                iter.next().unwrap(),
+                fixnum_as_cell!(Fixnum::build_with(1i64))
+            );
 
             let h = iter.focus();
 
             assert_eq!(h.value(), 5);
             assert_eq!(unmark_cell_bits!(iter.heap[4]), pstr_offset_as_cell!(0));
-            assert_eq!(unmark_cell_bits!(iter.heap[5]), fixnum_as_cell!(Fixnum::build_with(1i64)));
+            assert_eq!(
+                unmark_cell_bits!(iter.heap[5]),
+                fixnum_as_cell!(Fixnum::build_with(1i64))
+            );
 
             assert_eq!(iter.next(), None);
         }
@@ -1980,10 +2081,7 @@ mod tests {
                 pstr_as_cell!(atom!("a string"))
             );
 
-            assert_eq!(
+            assert_eq!(iter.next().unwrap(), empty_list_as_cell!());
-                iter.next().unwrap(),
-                empty_list_as_cell!()
-            );
 
             assert_eq!(iter.next(), None);
         }
@@ -2037,7 +2135,8 @@ mod tests {
         let a_atom = atom!("a");
         let b_atom = atom!("b");
 
-        wam.machine_st.heap
+        wam.machine_st
+            .heap
             .extend(functor!(f_atom, [atom(a_atom), atom(b_atom)]));
 
         {
@@ -2075,7 +2174,8 @@ mod tests {
             ]
         ));
 
-        for _ in 0..20 { // 0000 {
+        for _ in 0..20 {
+            // 0000 {
             let mut iter = stackful_post_order_iter(
                 &mut wam.machine_st.heap,
                 &mut wam.machine_st.stack,
@@ -2263,7 +2363,8 @@ mod tests {
         // two-part complete string, then a three-part cyclic string
         // involving an uncompacted list of chars.
 
-        let pstr_var_cell = put_partial_string(&mut wam.machine_st.heap, "abc ", &mut wam.machine_st.atom_tbl);
+        let pstr_var_cell =
+            put_partial_string(&mut wam.machine_st.heap, "abc ", &wam.machine_st.atom_tbl);
         let pstr_cell = wam.machine_st.heap[pstr_var_cell.get_value() as usize];
 
         {
@@ -2286,7 +2387,8 @@ mod tests {
         wam.machine_st.heap.pop();
         wam.machine_st.heap.push(pstr_loc_as_cell!(2));
 
-        let pstr_second_var_cell = put_partial_string(&mut wam.machine_st.heap, "def", &mut wam.machine_st.atom_tbl);
+        let pstr_second_var_cell =
+            put_partial_string(&mut wam.machine_st.heap, "def", &wam.machine_st.atom_tbl);
         let pstr_second_cell = wam.machine_st.heap[pstr_second_var_cell.get_value() as usize];
 
         {
@@ -2307,10 +2409,14 @@ mod tests {
         }
 
         wam.machine_st.heap.pop();
-        wam.machine_st.heap.push(pstr_loc_as_cell!(wam.machine_st.heap.len() + 1));
+        wam.machine_st
+            .heap
+            .push(pstr_loc_as_cell!(wam.machine_st.heap.len() + 1));
 
         wam.machine_st.heap.push(pstr_offset_as_cell!(0));
-        wam.machine_st.heap.push(fixnum_as_cell!(Fixnum::build_with(0i64)));
+        wam.machine_st
+            .heap
+            .push(fixnum_as_cell!(Fixnum::build_with(0i64)));
 
         {
             let mut iter = stackful_post_order_iter(
@@ -2319,8 +2425,14 @@ mod tests {
                 pstr_loc_as_cell!(0),
             );
 
-            assert_eq!(iter.next().unwrap(), fixnum_as_cell!(Fixnum::build_with(0i64)));
+            assert_eq!(
-            assert_eq!(unmark_cell_bits!(iter.next().unwrap()), pstr_offset_as_cell!(0));
+                iter.next().unwrap(),
+                fixnum_as_cell!(Fixnum::build_with(0i64))
+            );
+            assert_eq!(
+                unmark_cell_bits!(iter.next().unwrap()),
+                pstr_offset_as_cell!(0)
+            );
 
             assert_eq!(unmark_cell_bits!(iter.next().unwrap()), pstr_second_cell);
             assert_eq!(unmark_cell_bits!(iter.next().unwrap()), pstr_cell);
@@ -2329,7 +2441,9 @@ mod tests {
         }
 
         wam.machine_st.heap.pop();
-        wam.machine_st.heap.push(fixnum_as_cell!(Fixnum::build_with(1i64)));
+        wam.machine_st
+            .heap
+            .push(fixnum_as_cell!(Fixnum::build_with(1i64)));
 
         {
             let mut iter = stackful_post_order_iter(
@@ -2338,8 +2452,14 @@ mod tests {
                 pstr_loc_as_cell!(0),
             );
 
-            assert_eq!(iter.next().unwrap(), fixnum_as_cell!(Fixnum::build_with(1i64)));
+            assert_eq!(
-            assert_eq!(unmark_cell_bits!(iter.next().unwrap()), pstr_offset_as_cell!(0));
+                iter.next().unwrap(),
+                fixnum_as_cell!(Fixnum::build_with(1i64))
+            );
+            assert_eq!(
+                unmark_cell_bits!(iter.next().unwrap()),
+                pstr_offset_as_cell!(0)
+            );
 
             assert_eq!(unmark_cell_bits!(iter.next().unwrap()), pstr_second_cell);
             assert_eq!(unmark_cell_bits!(iter.next().unwrap()), pstr_cell);
@@ -2498,13 +2618,12 @@ mod tests {
         let a_atom = atom!("a");
         let b_atom = atom!("b");
 
-        wam.machine_st.heap.extend(functor!(f_atom, [atom(a_atom), atom(b_atom)]));
+        wam.machine_st
+            .heap
+            .extend(functor!(f_atom, [atom(a_atom), atom(b_atom)]));
 
         {
-            let mut iter = stackless_post_order_iter(
+            let mut iter = stackless_post_order_iter(&mut wam.machine_st.heap, str_loc_as_cell!(0));
-                &mut wam.machine_st.heap,
-                str_loc_as_cell!(0),
-            );
 
             assert_eq!(
                 unmark_cell_bits!(iter.next().unwrap()),
@@ -2535,10 +2654,7 @@ mod tests {
         ));
 
         for _ in 0..20 {
-            let mut iter = stackless_post_order_iter(
+            let mut iter = stackless_post_order_iter(&mut wam.machine_st.heap, str_loc_as_cell!(0));
-                &mut wam.machine_st.heap,
-                str_loc_as_cell!(0),
-            );
 
             assert_eq!(unmark_cell_bits!(iter.next().unwrap()), str_loc_as_cell!(0));
 
@@ -2568,10 +2684,8 @@ mod tests {
         {
             wam.machine_st.heap.push(heap_loc_as_cell!(0));
 
-            let mut iter = stackless_post_order_iter(
+            let mut iter =
-                &mut wam.machine_st.heap,
+                stackless_post_order_iter(&mut wam.machine_st.heap, heap_loc_as_cell!(0));
-                heap_loc_as_cell!(0),
-            );
 
             assert_eq!(
                 unmark_cell_bits!(iter.next().unwrap()),
@@ -2587,10 +2701,8 @@ mod tests {
             wam.machine_st.heap.push(heap_loc_as_cell!(1));
             wam.machine_st.heap.push(heap_loc_as_cell!(0));
 
-            let mut iter = stackless_post_order_iter(
+            let mut iter =
-                &mut wam.machine_st.heap,
+                stackless_post_order_iter(&mut wam.machine_st.heap, heap_loc_as_cell!(0));
-                heap_loc_as_cell!(0),
-            );
 
             assert_eq!(
                 unmark_cell_bits!(iter.next().unwrap()),
@@ -2615,7 +2727,8 @@ mod tests {
         wam.machine_st.heap.push(empty_list_as_cell!());
 
         {
-            let mut iter = stackless_post_order_iter(&mut wam.machine_st.heap, heap_loc_as_cell!(0));
+            let mut iter =
+                stackless_post_order_iter(&mut wam.machine_st.heap, heap_loc_as_cell!(0));
 
             assert_eq!(
                 unmark_cell_bits!(iter.next().unwrap()),
@@ -2647,7 +2760,8 @@ mod tests {
         wam.machine_st.heap.push(heap_loc_as_cell!(0));
 
         {
-            let mut iter = stackless_post_order_iter(&mut wam.machine_st.heap, heap_loc_as_cell!(0));
+            let mut iter =
+                stackless_post_order_iter(&mut wam.machine_st.heap, heap_loc_as_cell!(0));
 
             // the cycle will be iterated twice before being detected.
             assert_eq!(
@@ -2675,7 +2789,8 @@ mod tests {
         }
 
         {
-            let mut iter = stackless_post_order_iter(&mut wam.machine_st.heap, heap_loc_as_cell!(0));
+            let mut iter =
+                stackless_post_order_iter(&mut wam.machine_st.heap, heap_loc_as_cell!(0));
 
             // cut the iteration short to check that all cells are
             // unmarked and unforwarded by the Drop instance of
@@ -2705,11 +2820,13 @@ mod tests {
         // two-part complete string, then a three-part cyclic string
         // involving an uncompacted list of chars.
 
-        let pstr_var_cell = put_partial_string(&mut wam.machine_st.heap, "abc ", &mut wam.machine_st.atom_tbl);
+        let pstr_var_cell =
+            put_partial_string(&mut wam.machine_st.heap, "abc ", &wam.machine_st.atom_tbl);
         let pstr_cell = wam.machine_st.heap[pstr_var_cell.get_value() as usize];
 
         {
-            let mut iter = stackless_post_order_iter(&mut wam.machine_st.heap, pstr_loc_as_cell!(0));
+            let mut iter =
+                stackless_post_order_iter(&mut wam.machine_st.heap, pstr_loc_as_cell!(0));
 
             assert_eq!(
                 unmark_cell_bits!(iter.next().unwrap()),
@@ -2724,16 +2841,14 @@ mod tests {
         wam.machine_st.heap.pop();
         wam.machine_st.heap.push(pstr_loc_as_cell!(2));
 
-        let pstr_second_var_cell = put_partial_string(
+        let pstr_second_var_cell =
-            &mut wam.machine_st.heap,
+            put_partial_string(&mut wam.machine_st.heap, "def", &wam.machine_st.atom_tbl);
-            "def",
-            &mut wam.machine_st.atom_tbl,
-        );
 
         let pstr_second_cell = wam.machine_st.heap[pstr_second_var_cell.get_value() as usize];
 
         {
-            let mut iter = stackless_post_order_iter(&mut wam.machine_st.heap, pstr_loc_as_cell!(0));
+            let mut iter =
+                stackless_post_order_iter(&mut wam.machine_st.heap, pstr_loc_as_cell!(0));
 
             assert_eq!(
                 unmark_cell_bits!(iter.next().unwrap()),
@@ -2749,20 +2864,31 @@ mod tests {
         all_cells_unmarked(&wam.machine_st.heap);
 
         wam.machine_st.heap.pop();
-        wam.machine_st.heap.push(pstr_loc_as_cell!(wam.machine_st.heap.len() + 1));
+        wam.machine_st
+            .heap
+            .push(pstr_loc_as_cell!(wam.machine_st.heap.len() + 1));
 
         wam.machine_st.heap.push(pstr_offset_as_cell!(0));
-        wam.machine_st.heap.push(fixnum_as_cell!(Fixnum::build_with(0)));
+        wam.machine_st
+            .heap
+            .push(fixnum_as_cell!(Fixnum::build_with(0)));
 
         {
-            let mut iter = stackless_post_order_iter(&mut wam.machine_st.heap, pstr_loc_as_cell!(0));
+            let mut iter =
+                stackless_post_order_iter(&mut wam.machine_st.heap, pstr_loc_as_cell!(0));
             let mut pstr_loc_cell = pstr_loc_as_cell!(0);
 
             pstr_loc_cell.set_forwarding_bit(true);
 
             // assert_eq!(iter.next().unwrap(), fixnum_as_cell!(Fixnum::build_with(0i64)));
-            assert_eq!(unmark_cell_bits!(iter.next().unwrap()), pstr_offset_as_cell!(0));
+            assert_eq!(
-            assert_eq!(unmark_cell_bits!(iter.next().unwrap()), pstr_offset_as_cell!(0));
+                unmark_cell_bits!(iter.next().unwrap()),
+                pstr_offset_as_cell!(0)
+            );
+            assert_eq!(
+                unmark_cell_bits!(iter.next().unwrap()),
+                pstr_offset_as_cell!(0)
+            );
 
             assert_eq!(unmark_cell_bits!(iter.next().unwrap()), pstr_second_cell);
             assert_eq!(unmark_cell_bits!(iter.next().unwrap()), pstr_cell);
@@ -2773,14 +2899,23 @@ mod tests {
         all_cells_unmarked(&wam.machine_st.heap);
 
         wam.machine_st.heap.pop();
-        wam.machine_st.heap.push(fixnum_as_cell!(Fixnum::build_with(1)));
+        wam.machine_st
+            .heap
+            .push(fixnum_as_cell!(Fixnum::build_with(1)));
 
         {
-            let mut iter = stackless_post_order_iter(&mut wam.machine_st.heap, pstr_loc_as_cell!(0));
+            let mut iter =
+                stackless_post_order_iter(&mut wam.machine_st.heap, pstr_loc_as_cell!(0));
 
             //assert_eq!(iter.next().unwrap(), fixnum_as_cell!(Fixnum::build_with(1)));
-            assert_eq!(unmark_cell_bits!(iter.next().unwrap()), pstr_offset_as_cell!(0));
+            assert_eq!(
-            assert_eq!(unmark_cell_bits!(iter.next().unwrap()), pstr_offset_as_cell!(0));
+                unmark_cell_bits!(iter.next().unwrap()),
+                pstr_offset_as_cell!(0)
+            );
+            assert_eq!(
+                unmark_cell_bits!(iter.next().unwrap()),
+                pstr_offset_as_cell!(0)
+            );
 
             assert_eq!(unmark_cell_bits!(iter.next().unwrap()), pstr_second_cell);
             assert_eq!(unmark_cell_bits!(iter.next().unwrap()), pstr_cell);
@@ -2801,7 +2936,8 @@ mod tests {
         wam.machine_st.heap.extend(functor);
 
         {
-            let mut iter = stackless_post_order_iter(&mut wam.machine_st.heap, heap_loc_as_cell!(0));
+            let mut iter =
+                stackless_post_order_iter(&mut wam.machine_st.heap, heap_loc_as_cell!(0));
 
             assert_eq!(
                 unmark_cell_bits!(iter.next().unwrap()),
@@ -2861,7 +2997,8 @@ mod tests {
         wam.machine_st.heap[4] = list_loc_as_cell!(1);
 
         {
-            let mut iter = stackless_post_order_iter(&mut wam.machine_st.heap, heap_loc_as_cell!(0));
+            let mut iter =
+                stackless_post_order_iter(&mut wam.machine_st.heap, heap_loc_as_cell!(0));
 
             assert_eq!(
                 unmark_cell_bits!(iter.next().unwrap()),

src/heap_print.rs

@@ -29,6 +29,7 @@ use std::convert::TryFrom;
 use std::iter::once;
 use std::net::{IpAddr, TcpListener};
 use std::rc::Rc;
+use std::sync::Arc;
 
 /* contains the location, name, precision and Specifier of the parent op. */
 #[derive(Debug, Copy, Clone)]
@@ -74,7 +75,7 @@ fn needs_bracketing(child_desc: OpDesc, op: &DirectedOp) -> bool {
         DirectedOp::Left(name, cell) => {
             let (priority, spec) = cell.get();
 
-            if name.as_str() == "-" {
+            if &*name.as_str() == "-" {
                 let child_assoc = child_desc.get_spec();
                 if is_prefix!(spec) && (is_postfix!(child_assoc) || is_infix!(child_assoc)) {
                     return true;
@@ -178,10 +179,9 @@ fn char_to_string(is_quoted: bool, c: char) -> String {
         '\u{08}' if is_quoted => "\\b".to_string(), // UTF-8 backspace
         '\u{07}' if is_quoted => "\\a".to_string(), // UTF-8 alert
         '\\' if is_quoted => "\\\\".to_string(),
-        ' ' | '\'' | '\n' | '\r' | '\t' | '\u{0b}' | '\u{0c}' | '\u{08}' | '\u{07}' | '"' | '\\' => {
+        ' ' | '\'' | '\n' | '\r' | '\t' | '\u{0b}' | '\u{0c}' | '\u{08}' | '\u{07}' | '"'
-            c.to_string()
+        | '\\' => c.to_string(),
-        }
+        _ => {
-        _ =>
             if c.is_whitespace() || c.is_control() {
                 // print all other control and whitespace characters in hex.
                 format!("\\x{:x}\\", c as u32)
@@ -190,6 +190,7 @@ fn char_to_string(is_quoted: bool, c: char) -> String {
             }
         }
     }
+}
 
 #[derive(Clone, Copy, Debug)]
 enum NumberFocus {
@@ -217,7 +218,8 @@ enum TokenOrRedirect {
     CompositeRedirect(usize, DirectedOp),
     CurlyBracketRedirect(usize),
     FunctorRedirect(usize),
-    #[allow(unused)] IpAddr(IpAddr),
+    #[allow(unused)]
+    IpAddr(IpAddr),
     NumberFocus(usize, NumberFocus, Option<DirectedOp>),
     Open,
     Close,
@@ -479,7 +481,7 @@ pub fn fmt_float(mut fl: f64) -> String {
 pub struct HCPrinter<'a, Outputter> {
     outputter: Outputter,
     iter: StackfulPreOrderHeapIter<'a>,
-    atom_tbl: &'a mut AtomTable,
+    atom_tbl: Arc<AtomTable>,
     op_dir: &'a OpDir,
     state_stack: Vec<TokenOrRedirect>,
     toplevel_spec: Option<DirectedOp>,
@@ -548,7 +550,7 @@ pub(crate) fn numbervar(offset: &Integer, addr: HeapCellValue) -> Option<String>
 impl<'a, Outputter: HCValueOutputter> HCPrinter<'a, Outputter> {
     pub fn new(
         heap: &'a mut Heap,
-        atom_tbl: &'a mut AtomTable,
+        atom_tbl: Arc<AtomTable>,
         stack: &'a mut Stack,
         op_dir: &'a OpDir,
         output: Outputter,
@@ -625,11 +627,12 @@ impl<'a, Outputter: HCValueOutputter> HCPrinter<'a, Outputter> {
             } else {
                 let op = DirectedOp::Left(name, spec);
 
-                self.state_stack.push(TokenOrRedirect::CompositeRedirect(max_depth, op));
+                self.state_stack
+                    .push(TokenOrRedirect::CompositeRedirect(max_depth, op));
                 self.state_stack.push(TokenOrRedirect::Op(name, spec));
             }
         } else {
-            match name.as_str() {
+            match &*name.as_str() {
                 "|" => {
                     self.format_bar_separator_op(max_depth, name, spec);
                     return;
@@ -653,9 +656,15 @@ impl<'a, Outputter: HCValueOutputter> HCPrinter<'a, Outputter> {
                 let left_directed_op = DirectedOp::Left(name, spec);
                 let right_directed_op = DirectedOp::Right(name, spec);
 
-                self.state_stack.push(TokenOrRedirect::CompositeRedirect(max_depth, left_directed_op));
+                self.state_stack.push(TokenOrRedirect::CompositeRedirect(
+                    max_depth,
+                    left_directed_op,
+                ));
                 self.state_stack.push(TokenOrRedirect::Op(name, spec));
-                self.state_stack.push(TokenOrRedirect::CompositeRedirect(max_depth, right_directed_op));
+                self.state_stack.push(TokenOrRedirect::CompositeRedirect(
+                    max_depth,
+                    right_directed_op,
+                ));
             }
         }
     }
@@ -681,7 +690,8 @@ impl<'a, Outputter: HCValueOutputter> HCPrinter<'a, Outputter> {
             self.state_stack.push(TokenOrRedirect::Close);
 
             for _ in 0..arity {
-                self.state_stack.push(TokenOrRedirect::FunctorRedirect(max_depth));
+                self.state_stack
+                    .push(TokenOrRedirect::FunctorRedirect(max_depth));
                 self.state_stack.push(TokenOrRedirect::Comma);
             }
 
@@ -738,9 +748,9 @@ impl<'a, Outputter: HCValueOutputter> HCPrinter<'a, Outputter> {
             return false;
         }
 
-
         self.state_stack.push(TokenOrRedirect::RightCurly);
-        self.state_stack.push(TokenOrRedirect::CurlyBracketRedirect(max_depth));
+        self.state_stack
+            .push(TokenOrRedirect::CurlyBracketRedirect(max_depth));
         self.state_stack.push(TokenOrRedirect::LeftCurly);
 
         true
@@ -750,10 +760,7 @@ impl<'a, Outputter: HCValueOutputter> HCPrinter<'a, Outputter> {
         let h = self.iter.stack_last().unwrap();
 
         let cell = self.iter.read_cell(h);
-        let cell = heap_bound_store(
+        let cell = heap_bound_store(&self.iter.heap, heap_bound_deref(&self.iter.heap, cell));
-            &self.iter.heap,
-            heap_bound_deref(&self.iter.heap, cell),
-        );
 
         // 7.10.4
         if let Some(var) = numbervar(&self.numbervars_offset, cell) {
@@ -835,10 +842,7 @@ impl<'a, Outputter: HCValueOutputter> HCPrinter<'a, Outputter> {
         if let Some(cell) = self.iter.next() {
             let is_cyclic = cell.get_forwarding_bit();
 
-            let cell = heap_bound_store(
+            let cell = heap_bound_store(self.iter.heap, heap_bound_deref(self.iter.heap, cell));
-                self.iter.heap,
-                heap_bound_deref(self.iter.heap, cell),
-            );
             let cell = unmark_cell_bits!(cell);
 
             match self.var_names.get(&cell).cloned() {
@@ -891,7 +895,7 @@ impl<'a, Outputter: HCValueOutputter> HCPrinter<'a, Outputter> {
     }
 
     fn print_impromptu_atom(&mut self, atom: Atom) {
-        let result = self.print_op_addendum(atom.as_str());
+        let result = self.print_op_addendum(&*atom.as_str());
 
         push_space_if_amb!(self, result.as_str(), {
             append_str!(self, &result);
@@ -1050,7 +1054,8 @@ impl<'a, Outputter: HCValueOutputter> HCPrinter<'a, Outputter> {
                         NumberFocus::Denominator(r),
                         left_directed_op,
                     ));
-                    self.state_stack.push(TokenOrRedirect::Op(rdiv_ct, *op_desc));
+                    self.state_stack
+                        .push(TokenOrRedirect::Op(rdiv_ct, *op_desc));
                     self.state_stack.push(TokenOrRedirect::NumberFocus(
                         max_depth,
                         NumberFocus::Numerator(r),
@@ -1157,8 +1162,7 @@ impl<'a, Outputter: HCValueOutputter> HCPrinter<'a, Outputter> {
             HeapCellValueTag::PStr | HeapCellValueTag::PStrOffset => {
                 self.iter.pop_stack();
             }
-            HeapCellValueTag::CStr => {
+            HeapCellValueTag::CStr => {}
-            }
             _ => {
                 unreachable!();
             }
@@ -1203,8 +1207,10 @@ impl<'a, Outputter: HCValueOutputter> HCPrinter<'a, Outputter> {
                         append_str!(self, "[]");
                     }
                 } else {
-                    self.state_stack.push(TokenOrRedirect::FunctorRedirect(max_depth));
+                    self.state_stack
-                    self.iter.push_stack(IterStackLoc::iterable_loc(end_h, HeapOrStackTag::Heap));
+                        .push(TokenOrRedirect::FunctorRedirect(max_depth));
+                    self.iter
+                        .push_stack(IterStackLoc::iterable_loc(end_h, HeapOrStackTag::Heap));
                 }
             }
         } else {
@@ -1298,7 +1304,8 @@ impl<'a, Outputter: HCValueOutputter> HCPrinter<'a, Outputter> {
             }
         }
 
-        self.state_stack.push(TokenOrRedirect::CloseList(switch.clone()));
+        self.state_stack
+            .push(TokenOrRedirect::CloseList(switch.clone()));
         Some(switch)
     }
 
@@ -1335,9 +1342,11 @@ impl<'a, Outputter: HCValueOutputter> HCPrinter<'a, Outputter> {
 
         let switch = self.close_list(cell);
 
-        self.state_stack.push(TokenOrRedirect::FunctorRedirect(max_depth));
+        self.state_stack
+            .push(TokenOrRedirect::FunctorRedirect(max_depth));
         self.state_stack.push(TokenOrRedirect::HeadTailSeparator); // bar
-        self.state_stack.push(TokenOrRedirect::FunctorRedirect(max_depth+1));
+        self.state_stack
+            .push(TokenOrRedirect::FunctorRedirect(max_depth + 1));
 
         self.open_list(switch);
     }
@@ -1353,8 +1362,8 @@ impl<'a, Outputter: HCValueOutputter> HCPrinter<'a, Outputter> {
         max_depth: usize,
     ) {
         let add_brackets = if !self.ignore_ops {
-            negated_operand ||
+            negated_operand
-                if let Some(ref op) = op {
+                || if let Some(ref op) = op {
                     if self.numbervars && arity == 1 && name == atom!("$VAR") {
                         !self.iter.immediate_leaf_has_property(|addr| {
                             match Number::try_from(addr) {
@@ -1381,7 +1390,8 @@ impl<'a, Outputter: HCValueOutputter> HCPrinter<'a, Outputter> {
             self.state_stack.push(TokenOrRedirect::Open);
 
             if !self.outputter.ends_with(" ") {
-                let parent_op = self.parent_of_first_op
+                let parent_op = self
+                    .parent_of_first_op
                     .and_then(|(parent_op, last_item_idx)| {
                         // if parent_op isn't printed to the output string
                         // already, then it doesn't border the present op
@@ -1395,7 +1405,9 @@ impl<'a, Outputter: HCValueOutputter> HCPrinter<'a, Outputter> {
 
                 for op in &[op, parent_op] {
                     if let Some(ref op) = &op {
-                        if op.is_left() && (op.is_prefix() || requires_space(op.as_atom().as_str(), "(")) {
+                        if op.is_left()
+                            && (op.is_prefix() || requires_space(&*op.as_atom().as_str(), "("))
+                        {
                             self.state_stack.push(TokenOrRedirect::Space);
                             return;
                         }
@@ -1519,7 +1531,7 @@ impl<'a, Outputter: HCValueOutputter> HCPrinter<'a, Outputter> {
                         max_depth,
                     );
                 } else {
-                    push_space_if_amb!(printer, name.as_str(), {
+                    push_space_if_amb!(printer, &*name.as_str(), {
                         printer.format_clause(max_depth, arity, name, None);
                     });
                 }
@@ -1529,14 +1541,18 @@ impl<'a, Outputter: HCValueOutputter> HCPrinter<'a, Outputter> {
                 if let Some(ref op) = op {
                     let op_is_prefix = op.is_prefix() && op.is_left();
 
-                    if op_is_prefix || printer.outputter.ends_with(&format!(" {}", op.as_atom().as_str())) {
+                    if op_is_prefix
+                        || printer
+                            .outputter
+                            .ends_with(&format!(" {}", op.as_atom().as_str()))
+                    {
                         result.push(' ');
                     }
 
                     result.push('(');
                 }
 
-                result += &printer.print_op_addendum(name.as_str());
+                result += &printer.print_op_addendum(&*name.as_str());
 
                 if op.is_some() {
                     result.push(')');
@@ -1546,7 +1562,7 @@ impl<'a, Outputter: HCValueOutputter> HCPrinter<'a, Outputter> {
                     append_str!(printer, &result);
                 });
             } else {
-                push_space_if_amb!(printer, name.as_str(), {
+                push_space_if_amb!(printer, &*name.as_str(), {
                     printer.print_impromptu_atom(name);
                 });
             }
@@ -1557,7 +1573,10 @@ impl<'a, Outputter: HCValueOutputter> HCPrinter<'a, Outputter> {
             None => return,
         };
 
-        if !addr.is_var() && !addr.is_compound(&self.iter.heap) && self.max_depth_exhausted(max_depth) {
+        if !addr.is_var()
+            && !addr.is_compound(&self.iter.heap)
+            && self.max_depth_exhausted(max_depth)
+        {
             self.state_stack.push(TokenOrRedirect::Atom(atom!("...")));
             return;
         }
@@ -1567,7 +1586,7 @@ impl<'a, Outputter: HCValueOutputter> HCPrinter<'a, Outputter> {
                 print_struct(self, name, arity);
             }
             (HeapCellValueTag::Char, c) => {
-                let name = self.atom_tbl.build_with(&String::from(c));
+                let name = AtomTable::build_with(&self.atom_tbl, &String::from(c));
                 print_struct(self, name, 0);
             }
             (HeapCellValueTag::Str, s) => {
@@ -1585,7 +1604,7 @@ impl<'a, Outputter: HCValueOutputter> HCPrinter<'a, Outputter> {
                         max_depth,
                     );
                 } else {
-                    push_space_if_amb!(self, name.as_str(), {
+                    push_space_if_amb!(self, &*name.as_str(), {
                         self.format_clause(max_depth, arity, name, None);
                     });
                 }
@@ -1668,7 +1687,7 @@ impl<'a, Outputter: HCValueOutputter> HCPrinter<'a, Outputter> {
                 TokenOrRedirect::BarAsOp => append_str!(self, " | "),
                 TokenOrRedirect::Char(c) => print_char!(self, self.quoted, c),
                 TokenOrRedirect::Op(atom, op) => {
-                    self.print_op(atom.as_str());
+                    self.print_op(&*atom.as_str());
 
                     if is_prefix!(op.get_spec()) {
                         self.set_parent_of_first_op(Some(DirectedOp::Left(atom, op)));
@@ -1737,16 +1756,18 @@ mod tests {
         let b_atom = atom!("b");
         let c_atom = atom!("c");
 
-        wam.machine_st.heap.extend(functor!(f_atom, [atom(a_atom), atom(b_atom)]));
+        wam.machine_st
+            .heap
+            .extend(functor!(f_atom, [atom(a_atom), atom(b_atom)]));
 
         {
             let printer = HCPrinter::new(
                 &mut wam.machine_st.heap,
-                &mut wam.machine_st.atom_tbl,
+                Arc::clone(&wam.machine_st.atom_tbl),
                 &mut wam.machine_st.stack,
                 &wam.op_dir,
                 PrinterOutputter::new(),
-                heap_loc_as_cell!(0)
+                heap_loc_as_cell!(0),
             );
 
             let output = printer.print();
@@ -1771,11 +1792,11 @@ mod tests {
         {
             let printer = HCPrinter::new(
                 &mut wam.machine_st.heap,
-                &mut wam.machine_st.atom_tbl,
+                Arc::clone(&wam.machine_st.atom_tbl),
                 &mut wam.machine_st.stack,
                 &wam.op_dir,
                 PrinterOutputter::new(),
-                heap_loc_as_cell!(0)
+                heap_loc_as_cell!(0),
             );
 
             let output = printer.print();
@@ -1795,11 +1816,11 @@ mod tests {
         {
             let printer = HCPrinter::new(
                 &mut wam.machine_st.heap,
-                &mut wam.machine_st.atom_tbl,
+                Arc::clone(&wam.machine_st.atom_tbl),
                 &mut wam.machine_st.stack,
                 &wam.op_dir,
                 PrinterOutputter::new(),
-                heap_loc_as_cell!(0)
+                heap_loc_as_cell!(0),
             );
 
             let output = printer.print();
@@ -1808,14 +1829,16 @@ mod tests {
 
             let mut printer = HCPrinter::new(
                 &mut wam.machine_st.heap,
-                &mut wam.machine_st.atom_tbl,
+                Arc::clone(&wam.machine_st.atom_tbl),
                 &mut wam.machine_st.stack,
                 &wam.op_dir,
                 PrinterOutputter::new(),
-                heap_loc_as_cell!(0)
+                heap_loc_as_cell!(0),
             );
 
-            printer.var_names.insert(list_loc_as_cell!(1), VarPtr::from("L"));
+            printer
+                .var_names
+                .insert(list_loc_as_cell!(1), VarPtr::from("L"));
 
             let output = printer.print();
 
@@ -1839,7 +1862,7 @@ mod tests {
         {
             let printer = HCPrinter::new(
                 &mut wam.machine_st.heap,
-                &mut wam.machine_st.atom_tbl,
+                Arc::clone(&wam.machine_st.atom_tbl),
                 &mut wam.machine_st.stack,
                 &wam.op_dir,
                 PrinterOutputter::new(),
@@ -1858,7 +1881,7 @@ mod tests {
         {
             let printer = HCPrinter::new(
                 &mut wam.machine_st.heap,
-                &mut wam.machine_st.atom_tbl,
+                Arc::clone(&wam.machine_st.atom_tbl),
                 &mut wam.machine_st.stack,
                 &wam.op_dir,
                 PrinterOutputter::new(),
@@ -1875,14 +1898,16 @@ mod tests {
         {
             let mut printer = HCPrinter::new(
                 &mut wam.machine_st.heap,
-                &mut wam.machine_st.atom_tbl,
+                Arc::clone(&wam.machine_st.atom_tbl),
                 &mut wam.machine_st.stack,
                 &wam.op_dir,
                 PrinterOutputter::new(),
-                heap_loc_as_cell!(0)
+                heap_loc_as_cell!(0),
             );
 
-            printer.var_names.insert(list_loc_as_cell!(1), VarPtr::from("L"));
+            printer
+                .var_names
+                .insert(list_loc_as_cell!(1), VarPtr::from("L"));
 
             let output = printer.print();
 
@@ -1905,11 +1930,11 @@ mod tests {
         {
             let mut printer = HCPrinter::new(
                 &mut wam.machine_st.heap,
-                &mut wam.machine_st.atom_tbl,
+                Arc::clone(&wam.machine_st.atom_tbl),
                 &mut wam.machine_st.stack,
                 &wam.op_dir,
                 PrinterOutputter::new(),
-                heap_loc_as_cell!(0)
+                heap_loc_as_cell!(0),
             );
 
             printer.max_depth = 5;
@@ -1923,16 +1948,16 @@ mod tests {
 
         wam.machine_st.heap.clear();
 
-        put_partial_string(&mut wam.machine_st.heap, "abc", &mut wam.machine_st.atom_tbl);
+        put_partial_string(&mut wam.machine_st.heap, "abc", &wam.machine_st.atom_tbl);
 
         {
             let printer = HCPrinter::new(
                 &mut wam.machine_st.heap,
-                &mut wam.machine_st.atom_tbl,
+                Arc::clone(&wam.machine_st.atom_tbl),
                 &mut wam.machine_st.stack,
                 &wam.op_dir,
                 PrinterOutputter::new(),
-                pstr_loc_as_cell!(0)
+                pstr_loc_as_cell!(0),
             );
 
             let output = printer.print();
@@ -1956,7 +1981,7 @@ mod tests {
         {
             let mut printer = HCPrinter::new(
                 &mut wam.machine_st.heap,
-                &mut wam.machine_st.atom_tbl,
+                Arc::clone(&wam.machine_st.atom_tbl),
                 &mut wam.machine_st.stack,
                 &wam.op_dir,
                 PrinterOutputter::new(),
@@ -2000,35 +2025,39 @@ mod tests {
 
         all_cells_unmarked(&wam.machine_st.heap);
 
-        wam.op_dir.insert(
+        wam.op_dir
-            (atom!("+"), Fixity::In),
+            .insert((atom!("+"), Fixity::In), OpDesc::build_with(500, YFX as u8));
-            OpDesc::build_with(500, YFX as u8),
+        wam.op_dir
-        );
+            .insert((atom!("*"), Fixity::In), OpDesc::build_with(400, YFX as u8));
-        wam.op_dir.insert(
-            (atom!("*"), Fixity::In),
-            OpDesc::build_with(400, YFX as u8),
-        );
 
-        assert_eq!(&wam.parse_and_print_term("[a|[] + b].").unwrap(), "[a|[]+b]");
+        assert_eq!(
+            &wam.parse_and_print_term("[a|[] + b].").unwrap(),
+            "[a|[]+b]"
+        );
 
         all_cells_unmarked(&wam.machine_st.heap);
 
-        assert_eq!(&wam.parse_and_print_term("[a|[b|c]*d].").unwrap(), "[a|[b|c]*d]");
+        assert_eq!(
+            &wam.parse_and_print_term("[a|[b|c]*d].").unwrap(),
+            "[a|[b|c]*d]"
+        );
 
         all_cells_unmarked(&wam.machine_st.heap);
 
-        wam.op_dir.insert(
+        wam.op_dir
-            (atom!("fy"), Fixity::Pre),
+            .insert((atom!("fy"), Fixity::Pre), OpDesc::build_with(9, FY as u8));
-            OpDesc::build_with(9, FY as u8),
+
+        wam.op_dir
+            .insert((atom!("yf"), Fixity::Post), OpDesc::build_with(9, YF as u8));
+
+        assert_eq!(
+            &wam.parse_and_print_term("(fy (fy 1)yf)yf.").unwrap(),
+            "(fy (fy 1)yf)yf"
         );
 
-        wam.op_dir.insert(
+        assert_eq!(
-            (atom!("yf"), Fixity::Post),
+            &wam.parse_and_print_term("fy(fy(yf(fy(1)))).").unwrap(),
-            OpDesc::build_with(9, YF as u8),
+            "fy fy (fy 1)yf"
         );
-
-        assert_eq!(&wam.parse_and_print_term("(fy (fy 1)yf)yf.").unwrap(), "(fy (fy 1)yf)yf");
-
-        assert_eq!(&wam.parse_and_print_term("fy(fy(yf(fy(1)))).").unwrap(), "fy fy (fy 1)yf");
     }
 }

src/http.rs

@@ -1,13 +1,13 @@
-use std::sync::{Arc, Mutex, Condvar};
-use std::future::Future;
-use std::pin::Pin;
-use http_body_util::Full;
 use bytes::Bytes;
+use http_body_util::Full;
 use hyper::service::Service;
 use hyper::{body::Incoming as IncomingBody, Request, Response};
+use std::future::Future;
+use std::pin::Pin;
+use std::sync::{Arc, Condvar, Mutex};
 
 pub struct HttpListener {
-    pub incoming: std::sync::mpsc::Receiver<HttpRequest>
+    pub incoming: std::sync::mpsc::Receiver<HttpRequest>,
 }
 
 #[derive(Debug)]
@@ -31,7 +31,10 @@ impl Service<Request<IncomingBody>> for HttpService {
         // new connection!
         // we send the Request info to Prolog
         let response = Arc::new((Mutex::new(false), Mutex::new(None), Condvar::new()));
-	let http_request = HttpRequest { request: req, response: Arc::clone(&response) };
+        let http_request = HttpRequest {
+            request: req,
+            response: Arc::clone(&response),
+        };
         self.tx.send(http_request).unwrap();
 
         // we wait for the Response info from Prolog
@@ -46,9 +49,7 @@ impl Service<Request<IncomingBody>> for HttpService {
             let (_, response, _) = &*response;
             let response = response.lock().unwrap().take();
             let res = response.expect("Data race error in HTTP Server");
-	    Box::pin(async move {
+            Box::pin(async move { Ok(res) })
-		Ok(res)
-	    })
         }
     }
 }

src/indexing.rs

@@ -150,17 +150,20 @@ impl<'a> IndexingCodeMergingPtr<'a> {
         let third_level_index = if self.append_or_prepend.is_append() {
             vec![
                 IndexedChoiceInstruction::Try(external),
-                IndexedChoiceInstruction::Trust(index)
+                IndexedChoiceInstruction::Trust(index),
-            ].into()
+            ]
+            .into()
         } else {
             vec![
                 IndexedChoiceInstruction::Try(index),
-                IndexedChoiceInstruction::Trust(external)
+                IndexedChoiceInstruction::Trust(external),
-            ].into()
+            ]
+            .into()
         };
 
         let indexing_code_len = self.indexing_code.len();
-        self.indexing_code.push(IndexingLine::IndexedChoice(third_level_index));
+        self.indexing_code
+            .push(IndexingLine::IndexedChoice(third_level_index));
 
         match &mut self.indexing_code[self.offset] {
             IndexingLine::Indexing(IndexingInstruction::SwitchOnConstant(ref mut constants)) => {
@@ -188,7 +191,8 @@ impl<'a> IndexingCodeMergingPtr<'a> {
         };
 
         let indexing_code_len = self.indexing_code.len();
-        self.indexing_code.push(IndexingLine::DynamicIndexedChoice(third_level_index));
+        self.indexing_code
+            .push(IndexingLine::DynamicIndexedChoice(third_level_index));
 
         match &mut self.indexing_code[self.offset] {
             IndexingLine::Indexing(IndexingInstruction::SwitchOnConstant(ref mut constants)) => {
@@ -275,10 +279,8 @@ impl<'a> IndexingCodeMergingPtr<'a> {
                             );
                         }
                         None | Some(IndexingCodePtr::Fail) => {
-                            constants.insert(
+                            constants
-                                overlapping_constant,
+                                .insert(overlapping_constant, IndexingCodePtr::External(index));
-                                IndexingCodePtr::External(index),
-                            );
                         }
                         Some(IndexingCodePtr::DynamicExternal(o)) => {
                             self.add_dynamic_indexed_choice_for_constant(
@@ -345,16 +347,10 @@ impl<'a> IndexingCodeMergingPtr<'a> {
                 IndexingLine::Indexing(IndexingInstruction::SwitchOnConstant(constants)) => {
                     match constants.get(&constant).cloned() {
                         None | Some(IndexingCodePtr::Fail) if self.is_dynamic => {
-                            constants.insert(
+                            constants.insert(constant, IndexingCodePtr::DynamicExternal(index));
-                                constant,
-                                IndexingCodePtr::DynamicExternal(index),
-                            );
                         }
                         None | Some(IndexingCodePtr::Fail) => {
-                            constants.insert(
+                            constants.insert(constant, IndexingCodePtr::External(index));
-                                constant,
-                                IndexingCodePtr::External(index),
-                            );
                         }
                         Some(IndexingCodePtr::DynamicExternal(o)) => {
                             self.add_dynamic_indexed_choice_for_constant(o, constant, index);
@@ -432,17 +428,20 @@ impl<'a> IndexingCodeMergingPtr<'a> {
         let third_level_index = if self.append_or_prepend.is_append() {
             vec![
                 IndexedChoiceInstruction::Try(external),
-                IndexedChoiceInstruction::Trust(index)
+                IndexedChoiceInstruction::Trust(index),
-            ].into()
+            ]
+            .into()
         } else {
             vec![
                 IndexedChoiceInstruction::Try(index),
-                IndexedChoiceInstruction::Trust(external)
+                IndexedChoiceInstruction::Trust(external),
-            ].into()
+            ]
+            .into()
         };
 
         let indexing_code_len = self.indexing_code.len();
-        self.indexing_code.push(IndexingLine::IndexedChoice(third_level_index));
+        self.indexing_code
+            .push(IndexingLine::IndexedChoice(third_level_index));
 
         match &mut self.indexing_code[self.offset] {
             IndexingLine::Indexing(IndexingInstruction::SwitchOnStructure(ref mut structures)) => {
@@ -470,7 +469,8 @@ impl<'a> IndexingCodeMergingPtr<'a> {
         };
 
         let indexing_code_len = self.indexing_code.len();
-        self.indexing_code.push(IndexingLine::DynamicIndexedChoice(third_level_index));
+        self.indexing_code
+            .push(IndexingLine::DynamicIndexedChoice(third_level_index));
 
         match &mut self.indexing_code[self.offset] {
             IndexingLine::Indexing(IndexingInstruction::SwitchOnStructure(ref mut structures)) => {
@@ -584,13 +584,15 @@ impl<'a> IndexingCodeMergingPtr<'a> {
                         let third_level_index = if self.append_or_prepend.is_append() {
                             vec![
                                 IndexedChoiceInstruction::Try(o),
-                                IndexedChoiceInstruction::Trust(index)
+                                IndexedChoiceInstruction::Trust(index),
-                            ].into()
+                            ]
+                            .into()
                         } else {
                             vec![
                                 IndexedChoiceInstruction::Try(index),
-                                IndexedChoiceInstruction::Trust(o)
+                                IndexedChoiceInstruction::Trust(o),
-                            ].into()
+                            ]
+                            .into()
                         };
 
                         self.indexing_code
@@ -636,11 +638,7 @@ pub(crate) fn merge_clause_index(
             for overlapping_constant in overlapping_constants {
                 merging_ptr.offset = 0;
 
-                merging_ptr.index_overlapping_constant(
+                merging_ptr.index_overlapping_constant(*constant, *overlapping_constant, offset);
-                    *constant,
-                    *overlapping_constant,
-                    offset,
-                );
             }
         }
         OptArgIndexKey::Structure(_, index_loc, name, arity) => {
@@ -1060,8 +1058,7 @@ fn cap_choice_seq(prelude: &mut [IndexedChoiceInstruction]) {
 
 #[inline]
 fn cap_choice_seq_with_trust(prelude: &mut [IndexedChoiceInstruction]) {
-    prelude.last_mut().map(|instr| {
+    prelude.last_mut().map(|instr| match instr {
-        match instr {
         IndexedChoiceInstruction::Retry(i) => {
             *instr = IndexedChoiceInstruction::Trust(*i);
         }
@@ -1069,14 +1066,12 @@ fn cap_choice_seq_with_trust(prelude: &mut [IndexedChoiceInstruction]) {
             *instr = IndexedChoiceInstruction::DefaultTrust(*i);
         }
         _ => {}
-        }
     });
 }
 
 #[inline]
 fn uncap_choice_seq_with_trust(prelude: &mut [IndexedChoiceInstruction]) {
-    prelude.last_mut().map(|instr| {
+    prelude.last_mut().map(|instr| match instr {
-        match instr {
         IndexedChoiceInstruction::Trust(i) => {
             *instr = IndexedChoiceInstruction::Retry(*i);
         }
@@ -1084,7 +1079,6 @@ fn uncap_choice_seq_with_trust(prelude: &mut [IndexedChoiceInstruction]) {
             *instr = IndexedChoiceInstruction::DefaultRetry(*i);
         }
         _ => {}
-        }
     });
 }
 
@@ -1099,7 +1093,7 @@ fn uncap_choice_seq_with_try(prelude: &mut [IndexedChoiceInstruction]) {
 
 pub(crate) fn constant_key_alternatives(
     constant: Literal,
-    atom_tbl: &mut AtomTable,
+    atom_tbl: &AtomTable,
     // arena: &mut Arena,
 ) -> Vec<Literal> {
     let mut constants = vec![];
@@ -1111,7 +1105,7 @@ pub(crate) fn constant_key_alternatives(
             }
         }
         Literal::Char(c) => {
-            let atom = atom_tbl.build_with(&c.to_string());
+            let atom = AtomTable::build_with(&atom_tbl, &c.to_string());
             constants.push(Literal::Atom(atom));
         }
         /*
@@ -1129,9 +1123,11 @@ pub(crate) fn constant_key_alternatives(
         */
         Literal::Integer(ref n) => {
             if let Some(n) = n.to_isize() {
-                Fixnum::build_with_checked(n as i64).map(|n| {
+                Fixnum::build_with_checked(n as i64)
+                    .map(|n| {
                         constants.push(Literal::Fixnum(n));
-                }).unwrap();
+                    })
+                    .unwrap();
             }
         }
         _ => {}
@@ -1159,11 +1155,19 @@ pub(crate) trait Indexer {
 
     fn new() -> Self;
 
-    fn constants(&mut self) -> &mut IndexMap<Literal, VecDeque<Self::ThirdLevelIndex>, FxBuildHasher>;
+    fn constants(
+        &mut self,
+    ) -> &mut IndexMap<Literal, VecDeque<Self::ThirdLevelIndex>, FxBuildHasher>;
     fn lists(&mut self) -> &mut VecDeque<Self::ThirdLevelIndex>;
-    fn structures(&mut self) -> &mut IndexMap<(Atom, usize), VecDeque<Self::ThirdLevelIndex>, FxBuildHasher>;
+    fn structures(
+        &mut self,
+    ) -> &mut IndexMap<(Atom, usize), VecDeque<Self::ThirdLevelIndex>, FxBuildHasher>;
 
-    fn compute_index(is_initial_index: bool, index: usize, non_counted_bt: bool) -> Self::ThirdLevelIndex;
+    fn compute_index(
+        is_initial_index: bool,
+        index: usize,
+        non_counted_bt: bool,
+    ) -> Self::ThirdLevelIndex;
 
     fn second_level_index<IndexKey: Eq + Hash>(
         indices: IndexMap<IndexKey, VecDeque<Self::ThirdLevelIndex>, FxBuildHasher>,
@@ -1199,7 +1203,9 @@ impl Indexer for StaticCodeIndices {
     }
 
     #[inline]
-    fn constants(&mut self) -> &mut IndexMap<Literal, VecDeque<IndexedChoiceInstruction>, FxBuildHasher> {
+    fn constants(
+        &mut self,
+    ) -> &mut IndexMap<Literal, VecDeque<IndexedChoiceInstruction>, FxBuildHasher> {
         &mut self.constants
     }
 
@@ -1209,11 +1215,17 @@ impl Indexer for StaticCodeIndices {
     }
 
     #[inline]
-    fn structures(&mut self) -> &mut IndexMap<(Atom, usize), VecDeque<IndexedChoiceInstruction>, FxBuildHasher> {
+    fn structures(
+        &mut self,
+    ) -> &mut IndexMap<(Atom, usize), VecDeque<IndexedChoiceInstruction>, FxBuildHasher> {
         &mut self.structures
     }
 
-    fn compute_index(is_initial_index: bool, index: usize, non_counted_bt: bool) -> IndexedChoiceInstruction {
+    fn compute_index(
+        is_initial_index: bool,
+        index: usize,
+        non_counted_bt: bool,
+    ) -> IndexedChoiceInstruction {
         if is_initial_index {
             IndexedChoiceInstruction::Try(index + 1)
         } else if non_counted_bt {
@@ -1245,7 +1257,9 @@ impl Indexer for StaticCodeIndices {
     }
 
     fn switch_on<IndexKey: Eq + Hash>(
-        mut instr_fn: impl FnMut(IndexMap<IndexKey, IndexingCodePtr, FxBuildHasher>) -> IndexingInstruction,
+        mut instr_fn: impl FnMut(
+            IndexMap<IndexKey, IndexingCodePtr, FxBuildHasher>,
+        ) -> IndexingInstruction,
         index: &mut IndexMap<IndexKey, VecDeque<IndexedChoiceInstruction>, FxBuildHasher>,
         prelude: &mut VecDeque<IndexingLine>,
     ) -> IndexingCodePtr {
@@ -1345,7 +1359,9 @@ impl Indexer for DynamicCodeIndices {
         for (key, code) in indices.into_iter() {
             if code.len() > 1 {
                 index_locs.insert(key, IndexingCodePtr::Internal(prelude.len() + 1));
-                prelude.push_back(IndexingLine::DynamicIndexedChoice(code.into_iter().collect()));
+                prelude.push_back(IndexingLine::DynamicIndexedChoice(
+                    code.into_iter().collect(),
+                ));
             } else {
                 code.front().map(|i| {
                     index_locs.insert(key, IndexingCodePtr::DynamicExternal(*i));
@@ -1357,7 +1373,9 @@ impl Indexer for DynamicCodeIndices {
     }
 
     fn switch_on<IndexKey: Eq + Hash>(
-        mut instr_fn: impl FnMut(IndexMap<IndexKey, IndexingCodePtr, FxBuildHasher>) -> IndexingInstruction,
+        mut instr_fn: impl FnMut(
+            IndexMap<IndexKey, IndexingCodePtr, FxBuildHasher>,
+        ) -> IndexingInstruction,
         index: &mut IndexMap<IndexKey, VecDeque<usize>, FxBuildHasher>,
         prelude: &mut VecDeque<IndexingLine>,
     ) -> IndexingCodePtr {
@@ -1384,7 +1402,9 @@ impl Indexer for DynamicCodeIndices {
     ) -> IndexingCodePtr {
         if lists.len() > 1 {
             let lists = mem::replace(lists, VecDeque::new());
-            prelude.push_back(IndexingLine::DynamicIndexedChoice(lists.into_iter().collect()));
+            prelude.push_back(IndexingLine::DynamicIndexedChoice(
+                lists.into_iter().collect(),
+            ));
             IndexingCodePtr::Internal(1)
         } else {
             lists
@@ -1434,15 +1454,23 @@ impl<I: Indexer> CodeOffsets<I> {
 
     fn index_constant(
         &mut self,
-        atom_tbl: &mut AtomTable,
+        atom_tbl: &AtomTable,
         constant: Literal,
         index: usize,
     ) -> Vec<Literal> {
         let overlapping_constants = constant_key_alternatives(constant, atom_tbl);
-        let code = self.indices.constants().entry(constant).or_insert(VecDeque::new());
+        let code = self
+            .indices
+            .constants()
+            .entry(constant)
+            .or_insert(VecDeque::new());
 
         let is_initial_index = code.is_empty();
-        code.push_back(I::compute_index(is_initial_index, index, self.non_counted_bt));
+        code.push_back(I::compute_index(
+            is_initial_index,
+            index,
+            self.non_counted_bt,
+        ));
 
         for constant in &overlapping_constants {
             let code = self
@@ -1470,7 +1498,11 @@ impl<I: Indexer> CodeOffsets<I> {
         let code_len = code.len();
         let is_initial_index = code.is_empty();
 
-        code.push_back(I::compute_index(is_initial_index, index, self.non_counted_bt));
+        code.push_back(I::compute_index(
+            is_initial_index,
+            index,
+            self.non_counted_bt,
+        ));
         code_len
     }
 
@@ -1479,7 +1511,7 @@ impl<I: Indexer> CodeOffsets<I> {
         optimal_arg: &Term,
         index: usize,
         clause_index_info: &mut ClauseIndexInfo,
-        atom_tbl: &mut AtomTable,
+        atom_tbl: &AtomTable,
     ) {
         match optimal_arg {
             &Term::Clause(_, atom!("."), ref terms) if terms.len() == 2 => {

src/iterators.rs

@@ -62,9 +62,7 @@ impl<'a> TermIterState<'a> {
             Term::PartialString(cell, string_buf, tail) => {
                 TermIterState::InitialPartialString(lvl, cell, string_buf, tail)
             }
-            Term::CompleteString(cell, atom) => {
+            Term::CompleteString(cell, atom) => TermIterState::CompleteString(lvl, cell, *atom),
-                TermIterState::CompleteString(lvl, cell, *atom)
-            }
             Term::Var(cell, var_ptr) => TermIterState::Var(lvl, cell, var_ptr.clone()),
         }
     }
@@ -77,7 +75,8 @@ pub(crate) struct QueryIterator<'a> {
 
 impl<'a> QueryIterator<'a> {
     fn push_subterm(&mut self, lvl: Level, term: &'a Term) {
-        self.state_stack.push(TermIterState::subterm_to_state(lvl, term));
+        self.state_stack
+            .push(TermIterState::subterm_to_state(lvl, term));
     }
 
     /*
@@ -94,19 +93,16 @@ impl<'a> QueryIterator<'a> {
 
     fn from_term(term: &'a Term) -> Self {
         let state = match term {
-            Term::AnonVar | Term::Cons(..) | Term::Literal(..) |
+            Term::AnonVar
-            Term::PartialString(..) | Term::CompleteString(..) => {
+            | Term::Cons(..)
+            | Term::Literal(..)
+            | Term::PartialString(..)
+            | Term::CompleteString(..) => {
                 return QueryIterator {
                     state_stack: vec![],
                 }
             }
-            Term::Clause(r, name, terms) => TermIterState::Clause(
+            Term::Clause(r, name, terms) => TermIterState::Clause(Level::Root, 0, r, *name, terms),
-                Level::Root,
-                0,
-                r,
-                *name,
-                terms,
-            ),
             Term::Var(cell, var_ptr) => TermIterState::Var(Level::Root, cell, var_ptr.clone()),
         };
 
@@ -118,18 +114,21 @@ impl<'a> QueryIterator<'a> {
     fn extend_state(&mut self, lvl: Level, term: &'a QueryTerm) {
         match term {
             &QueryTerm::Clause(ref cell, ClauseType::CallN(_), ref terms, _) => {
-                self.state_stack.push(TermIterState::Clause(lvl, 1, cell, atom!("$call"), terms));
+                self.state_stack
+                    .push(TermIterState::Clause(lvl, 1, cell, atom!("$call"), terms));
             }
             &QueryTerm::Clause(ref cell, ref ct, ref terms, _) => {
-                self.state_stack.push(TermIterState::Clause(lvl, 0, cell, ct.name(), terms));
+                self.state_stack
-            }
+                    .push(TermIterState::Clause(lvl, 0, cell, ct.name(), terms));
-            _ => {
             }
+            _ => {}
         }
     }
 
     pub fn new(term: &'a QueryTerm) -> Self {
-        let mut iter = QueryIterator { state_stack: vec![] };
+        let mut iter = QueryIterator {
+            state_stack: vec![],
+        };
         iter.extend_state(Level::Root, term);
         iter
     }
@@ -170,13 +169,15 @@ impl<'a> Iterator for QueryIterator<'a> {
                     }
                 }
                 TermIterState::InitialCons(lvl, cell, head, tail) => {
-                    self.state_stack.push(TermIterState::FinalCons(lvl, cell, head, tail));
+                    self.state_stack
+                        .push(TermIterState::FinalCons(lvl, cell, head, tail));
 
                     self.push_subterm(lvl.child_level(), tail);
                     self.push_subterm(lvl.child_level(), head);
                 }
                 TermIterState::InitialPartialString(lvl, cell, string, tail) => {
-                    self.state_stack.push(TermIterState::FinalPartialString(lvl, cell, string, tail));
+                    self.state_stack
+                        .push(TermIterState::FinalPartialString(lvl, cell, string, tail));
                     self.push_subterm(lvl.child_level(), tail);
                 }
                 TermIterState::FinalPartialString(lvl, cell, atom, tail) => {
@@ -248,11 +249,7 @@ impl<'a> FactIterator<'a> {
                 )]
             }
             Term::CompleteString(cell, atom) => {
-                vec![TermIterState::CompleteString(
+                vec![TermIterState::CompleteString(Level::Root, cell, *atom)]
-                    Level::Root,
-                    cell,
-                    *atom,
-                )]
             }
             Term::Literal(cell, constant) => {
                 vec![TermIterState::Literal(Level::Root, cell, constant)]
@@ -319,7 +316,10 @@ pub(crate) fn post_order_iter<'a>(term: &'a Term) -> QueryIterator<'a> {
     QueryIterator::from_term(term)
 }
 
-pub(crate) fn breadth_first_iter<'a>(term: &'a Term, iterable_root: RootIterationPolicy) -> FactIterator<'a> {
+pub(crate) fn breadth_first_iter<'a>(
+    term: &'a Term,
+    iterable_root: RootIterationPolicy,
+) -> FactIterator<'a> {
     FactIterator::new(term, iterable_root)
 }
 
@@ -356,18 +356,14 @@ fn state_from_chunked_terms<'a>(chunk_vec: &'a VecDeque<ChunkedTerms>) -> Clause
 impl<'a> ClauseIterator<'a> {
     pub fn new(clauses: &'a ChunkedTermVec) -> Self {
         match state_from_chunked_terms(&clauses.chunk_vec) {
-            state @ ClauseIteratorState::RemainingBranches(..) => {
+            state @ ClauseIteratorState::RemainingBranches(..) => Self {
-                Self {
                 state_stack: vec![state],
                 remaining_chunks_on_stack: 0,
-                }
+            },
-            }
+            state @ ClauseIteratorState::RemainingChunks(..) => Self {
-            state @ ClauseIteratorState::RemainingChunks(..) => {
-                Self {
                 state_stack: vec![state],
                 remaining_chunks_on_stack: 1,
-                }
+            },
-            }
         }
     }
 
@@ -403,14 +399,16 @@ impl<'a> Iterator for ClauseIterator<'a> {
             match state {
                 ClauseIteratorState::RemainingChunks(chunks, focus) if focus < chunks.len() => {
                     if focus + 1 < chunks.len() {
-                        self.state_stack.push(ClauseIteratorState::RemainingChunks(chunks, focus + 1));
+                        self.state_stack
+                            .push(ClauseIteratorState::RemainingChunks(chunks, focus + 1));
                     } else {
                         self.remaining_chunks_on_stack -= 1;
                     }
 
                     match &chunks[focus] {
                         ChunkedTerms::Branch(branches) => {
-                            self.state_stack.push(ClauseIteratorState::RemainingBranches(branches, 0));
+                            self.state_stack
+                                .push(ClauseIteratorState::RemainingBranches(branches, 0));
                         }
                         ChunkedTerms::Chunk(chunk) => {
                             return Some(ClauseItem::Chunk(chunk));
@@ -420,8 +418,11 @@ impl<'a> Iterator for ClauseIterator<'a> {
                 ClauseIteratorState::RemainingChunks(chunks, focus) => {
                     debug_assert_eq!(chunks.len(), focus);
                 }
-                ClauseIteratorState::RemainingBranches(branches, focus) if focus < branches.len() => {
+                ClauseIteratorState::RemainingBranches(branches, focus)
-                    self.state_stack.push(ClauseIteratorState::RemainingBranches(&branches, focus + 1));
+                    if focus < branches.len() =>
+                {
+                    self.state_stack
+                        .push(ClauseIteratorState::RemainingBranches(&branches, focus + 1));
                     let state = state_from_chunked_terms(&branches[focus]);
 
                     if let ClauseIteratorState::RemainingChunks(..) = &state {

src/lib.rs

@@ -17,13 +17,13 @@ pub mod codegen;
 mod debray_allocator;
 #[cfg(feature = "ffi")]
 mod ffi;
-mod variable_records;
 mod forms;
 mod heap_iter;
 pub mod heap_print;
 #[cfg(feature = "http")]
 mod http;
 mod indexing;
+mod variable_records;
 #[macro_use]
 pub mod instructions {
     include!(concat!(env!("OUT_DIR"), "/instructions.rs"));
@@ -38,3 +38,5 @@ mod targets;
 pub mod types;
 
 use instructions::instr;
+
+mod rcu;

src/machine/arithmetic_ops.rs

@@ -50,9 +50,7 @@ macro_rules! drop_iter_on_err {
     };
 }
 
-fn zero_divisor_eval_error(
+fn zero_divisor_eval_error(stub_gen: impl Fn() -> FunctorStub + 'static) -> MachineStubGen {
-    stub_gen: impl Fn() -> FunctorStub + 'static,
-) -> MachineStubGen {
     Box::new(move |machine_st| {
         let eval_error = machine_st.evaluation_error(EvalError::ZeroDivisor);
         let stub = stub_gen();
@@ -61,9 +59,7 @@ fn zero_divisor_eval_error(
     })
 }
 
-fn undefined_eval_error(
+fn undefined_eval_error(stub_gen: impl Fn() -> FunctorStub + 'static) -> MachineStubGen {
-    stub_gen: impl Fn() -> FunctorStub + 'static,
-) -> MachineStubGen {
     Box::new(move |machine_st| {
         let eval_error = machine_st.evaluation_error(EvalError::Undefined);
         let stub = stub_gen();
@@ -169,9 +165,7 @@ pub(crate) fn add(lhs: Number, rhs: Number, arena: &mut Arena) -> Result<Number,
             Ok(Number::Float(add_f(float_i_to_f(&n1)?, n2)?))
         }
         (Number::Integer(n1), Number::Rational(n2))
-        | (Number::Rational(n2), Number::Integer(n1)) => {
+        | (Number::Rational(n2), Number::Integer(n1)) => Ok(Number::arena_from(&*n1 + &*n2, arena)),
-            Ok(Number::arena_from(&*n1 + &*n2, arena))
-        }
         (Number::Rational(n1), Number::Float(OrderedFloat(n2)))
         | (Number::Float(OrderedFloat(n2)), Number::Rational(n1)) => {
             Ok(Number::Float(add_f(float_r_to_f(&n1)?, n2)?))
@@ -179,9 +173,7 @@ pub(crate) fn add(lhs: Number, rhs: Number, arena: &mut Arena) -> Result<Number,
         (Number::Float(OrderedFloat(f1)), Number::Float(OrderedFloat(f2))) => {
             Ok(Number::Float(add_f(f1, f2)?))
         }
-        (Number::Rational(r1), Number::Rational(r2)) => {
+        (Number::Rational(r1), Number::Rational(r2)) => Ok(Number::arena_from(&*r1 + &*r2, arena)),
-            Ok(Number::arena_from(&*r1 + &*r2, arena))
-        }
     }
 }
 
@@ -197,12 +189,12 @@ pub(crate) fn neg(n: Number, arena: &mut Arena) -> Number {
         Number::Integer(n) => {
             let n_clone: Integer = (*n).clone();
             Number::arena_from(-Integer::from(n_clone), arena)
-        },
+        }
         Number::Float(OrderedFloat(f)) => Number::Float(OrderedFloat(-f)),
         Number::Rational(r) => {
             let r_clone: Rational = (*r).clone();
             Number::arena_from(-Rational::from(r_clone), arena)
-        },
+        }
     }
 }
 
@@ -219,12 +211,12 @@ pub(crate) fn abs(n: Number, arena: &mut Arena) -> Number {
         Number::Integer(n) => {
             let n_clone: Integer = (*n).clone();
             Number::arena_from(Integer::from(n_clone.abs()), arena)
-        },
+        }
         Number::Float(f) => Number::Float(f.abs()),
         Number::Rational(r) => {
             let r_clone: Rational = (*r).clone();
             Number::arena_from(Rational::from(r_clone.abs()), arena)
-        },
+        }
     }
 }
 
@@ -368,7 +360,11 @@ pub(crate) fn int_pow(n1: Number, n2: Number, arena: &mut Arena) -> Result<Numbe
         (Number::Integer(n1), Number::Fixnum(n2)) => {
             let n2_i = n2.get_num();
 
-            if !(&*n1 == &Integer::from(1) || &*n1 == &Integer::from(0) || &*n1 == &Integer::from(-1)) && n2_i < 0 {
+            if !(&*n1 == &Integer::from(1)
+                || &*n1 == &Integer::from(0)
+                || &*n1 == &Integer::from(-1))
+                && n2_i < 0
+            {
                 let n = Number::Integer(n1);
                 Err(numerical_type_error(ValidType::Float, n, stub_gen))
             } else {
@@ -377,7 +373,11 @@ pub(crate) fn int_pow(n1: Number, n2: Number, arena: &mut Arena) -> Result<Numbe
             }
         }
         (Number::Integer(n1), Number::Integer(n2)) => {
-            if !(&*n1 == &Integer::from(1) || &*n1 == &Integer::from(0) || &*n1 == &Integer::from(-1)) && &*n2 < &Integer::from(0) {
+            if !(&*n1 == &Integer::from(1)
+                || &*n1 == &Integer::from(0)
+                || &*n1 == &Integer::from(-1))
+                && &*n2 < &Integer::from(0)
+            {
                 let n = Number::Integer(n1);
                 Err(numerical_type_error(ValidType::Float, n, stub_gen))
             } else {
@@ -552,7 +552,7 @@ pub fn rational_from_number(
         Number::Integer(n) => {
             let n_clone: Integer = (*n).clone();
             Ok(arena_alloc!(Rational::from(n_clone), arena))
-        },
+        }
     }
 }
 
@@ -668,22 +668,22 @@ pub(crate) fn shr(n1: Number, n2: Number, arena: &mut Arena) -> Result<Number, M
 
             match n2.to_usize() {
                 Some(n2) => Ok(Number::arena_from(n1 >> n2, arena)),
-                _ => {
+                _ => Ok(Number::arena_from(n1 >> usize::max_value(), arena)),
-			        Ok(Number::arena_from(n1 >> usize::max_value(), arena))
-		        },
             }
         }
         (Number::Integer(n1), Number::Fixnum(n2)) => match usize::try_from(n2.get_num()) {
             Ok(n2) => Ok(Number::arena_from(Integer::from(&*n1 >> n2), arena)),
-            _ => {
+            _ => Ok(Number::arena_from(
-		        Ok(Number::arena_from(Integer::from(&*n1 >> usize::max_value()),arena))
+                Integer::from(&*n1 >> usize::max_value()),
-	        },
+                arena,
+            )),
         },
         (Number::Integer(n1), Number::Integer(n2)) => match n2.to_usize() {
             Some(n2) => Ok(Number::arena_from(Integer::from(&*n1 >> n2), arena)),
-            _ => {
+            _ => Ok(Number::arena_from(
-		        Ok(Number::arena_from(Integer::from(&*n1 >> usize::max_value()), arena))
+                Integer::from(&*n1 >> usize::max_value()),
-            },
+                arena,
+            )),
         },
         (Number::Integer(_), n2) => Err(numerical_type_error(ValidType::Integer, n2, stub_gen)),
         (Number::Fixnum(_), n2) => Err(numerical_type_error(ValidType::Integer, n2, stub_gen)),
@@ -719,22 +719,25 @@ pub(crate) fn shl(n1: Number, n2: Number, arena: &mut Arena) -> Result<Number, M
 
             match n2.to_u32() {
                 Some(n2) => Ok(Number::arena_from(n1.to_u64().unwrap() << n2, arena)),
-                _ => {
+                _ => Ok(Number::arena_from(n1 << usize::max_value(), arena)),
-			        Ok(Number::arena_from(n1 << usize::max_value(), arena))
-		        }
             }
         }
         (Number::Integer(n1), Number::Fixnum(n2)) => match usize::try_from(n2.get_num()) {
             Ok(n2) => Ok(Number::arena_from(Integer::from(&*n1 << n2), arena)),
-            _ => {
+            _ => Ok(Number::arena_from(
-		        Ok(Number::arena_from(Integer::from(&*n1 << usize::max_value()),arena))
+                Integer::from(&*n1 << usize::max_value()),
-		    }
+                arena,
+            )),
         },
         (Number::Integer(n1), Number::Integer(n2)) => match n2.to_u32() {
-            Some(n2) => Ok(Number::arena_from(Integer::from(n1.to_u64().unwrap() << n2), arena)),
+            Some(n2) => Ok(Number::arena_from(
-            _ => {
+                Integer::from(n1.to_u64().unwrap() << n2),
-		        Ok(Number::arena_from(Integer::from(&*n1 << usize::max_value()),arena))
+                arena,
-	        }
+            )),
+            _ => Ok(Number::arena_from(
+                Integer::from(&*n1 << usize::max_value()),
+                arena,
+            )),
         },
         (Number::Integer(_), n2) => Err(numerical_type_error(ValidType::Integer, n2, stub_gen)),
         (Number::Fixnum(_), n2) => Err(numerical_type_error(ValidType::Integer, n2, stub_gen)),
@@ -949,10 +952,7 @@ pub(crate) fn gcd(n1: Number, n2: Number, arena: &mut Arena) -> Result<Number, M
                 Ok(Number::arena_from(result, arena))
             } else {
                 let value: IBig = Integer::from(n1_i).gcd(&Integer::from(n2_i)).into();
-                Ok(Number::arena_from(
+                Ok(Number::arena_from(value, arena))
-                    value,
-                    arena,
-                ))
             }
         }
         (Number::Fixnum(n1), Number::Integer(n2)) | (Number::Integer(n2), Number::Fixnum(n1)) => {
@@ -962,7 +962,10 @@ pub(crate) fn gcd(n1: Number, n2: Number, arena: &mut Arena) -> Result<Number, M
         }
         (Number::Integer(n1), Number::Integer(n2)) => {
             let n1_clone: Integer = (*n1).clone();
-            Ok(Number::arena_from(Integer::from(n1_clone.gcd(&Integer::from(n2.to_isize().unwrap()))) as IBig, arena))
+            Ok(Number::arena_from(
+                Integer::from(n1_clone.gcd(&Integer::from(n2.to_isize().unwrap()))) as IBig,
+                arena,
+            ))
         }
         (Number::Float(f), _) | (_, Number::Float(f)) => {
             let n = Number::Float(f);
@@ -1050,12 +1053,14 @@ pub(crate) fn atanh(n1: Number) -> Result<f64, MachineStubGen> {
 
     let f1 = try_numeric_result!(result_f(&n1), stub_gen)?;
 
-    try_numeric_result!(if f1 == 1.0 || f1 == -1.0 {
+    try_numeric_result!(
+        if f1 == 1.0 || f1 == -1.0 {
             Err(EvalError::Undefined)
         } else {
             result_f(&Number::Float(OrderedFloat(f1.atanh())))
         },
-    stub_gen)
+        stub_gen
+    )
 }
 
 #[inline]
@@ -1107,7 +1112,6 @@ pub(crate) fn floor(n1: Number, arena: &mut Arena) -> Number {
     rnd_i(&n1, arena)
 }
 
-
 #[inline]
 pub(crate) fn ceiling(n1: Number, arena: &mut Arena) -> Number {
     let n1 = neg(n1, arena);
@@ -1167,9 +1171,10 @@ impl MachineState {
                     Err(_) => self.arith_eval_by_metacall(value),
                 }
             }
-            &ArithmeticTerm::Interm(i) => {
+            &ArithmeticTerm::Interm(i) => Ok(mem::replace(
-                Ok(mem::replace(&mut self.interms[i - 1], Number::Fixnum(Fixnum::build_with(0))))
+                &mut self.interms[i - 1],
-            }
+                Number::Fixnum(Fixnum::build_with(0)),
+            )),
             &ArithmeticTerm::Number(n) => Ok(n),
         }
     }
@@ -1183,11 +1188,14 @@ impl MachineState {
 
         match rational_from_number(n, caller, &mut self.arena) {
             Ok(r) => Ok(r),
-            Err(e_gen) => Err(e_gen(self))
+            Err(e_gen) => Err(e_gen(self)),
         }
     }
 
-    pub(crate) fn arith_eval_by_metacall(&mut self, value: HeapCellValue) -> Result<Number, MachineStub> {
+    pub(crate) fn arith_eval_by_metacall(
+        &mut self,
+        value: HeapCellValue,
+    ) -> Result<Number, MachineStub> {
         let stub_gen = || functor_stub(atom!("is"), 2);
         let mut iter = stackful_post_order_iter(&mut self.heap, &mut self.stack, value);
 
@@ -1493,26 +1501,11 @@ mod tests {
         let mut wam = MachineState::new();
         let mut op_dir = default_op_dir();
 
-        op_dir.insert(
+        op_dir.insert((atom!("+"), Fixity::In), OpDesc::build_with(500, YFX as u8));
-            (atom!("+"), Fixity::In),
+        op_dir.insert((atom!("-"), Fixity::In), OpDesc::build_with(500, YFX as u8));
-            OpDesc::build_with(500, YFX as u8),
+        op_dir.insert((atom!("-"), Fixity::Pre), OpDesc::build_with(200, FY as u8));
-        );
+        op_dir.insert((atom!("*"), Fixity::In), OpDesc::build_with(400, YFX as u8));
-        op_dir.insert(
+        op_dir.insert((atom!("/"), Fixity::In), OpDesc::build_with(400, YFX as u8));
-            (atom!("-"), Fixity::In),
-            OpDesc::build_with(500, YFX as u8),
-        );
-        op_dir.insert(
-            (atom!("-"), Fixity::Pre),
-            OpDesc::build_with(200, FY as u8),
-        );
-        op_dir.insert(
-            (atom!("*"), Fixity::In),
-            OpDesc::build_with(400, YFX as u8),
-        );
-        op_dir.insert(
-            (atom!("/"), Fixity::In),
-            OpDesc::build_with(400, YFX as u8),
-        );
 
         let term_write_result =
             parse_and_write_parsed_term_to_heap(&mut wam, "3 + 4 - 1 + 2.", &op_dir).unwrap();

src/machine/attributed_variables.rs

@@ -118,12 +118,9 @@ impl MachineState {
             and_frame[i] = self.registers[i];
         }
 
-        and_frame[arity + 1] =
+        and_frame[arity + 1] = fixnum_as_cell!(Fixnum::build_with(self.b0 as i64));
-            fixnum_as_cell!(Fixnum::build_with(self.b0 as i64));
+        and_frame[arity + 2] = fixnum_as_cell!(Fixnum::build_with(self.num_of_args as i64));
-        and_frame[arity + 2] =
+        and_frame[arity + 3] = fixnum_as_cell!(Fixnum::build_with(self.attr_var_init.cp as i64));
-            fixnum_as_cell!(Fixnum::build_with(self.num_of_args as i64));
-        and_frame[arity + 3] =
-            fixnum_as_cell!(Fixnum::build_with(self.attr_var_init.cp as i64));
 
         self.verify_attributes();
 

src/machine/code_walker.rs

@@ -8,7 +8,9 @@ fn capture_offset(line: &Instruction, index: usize, stack: &mut Vec<usize>) -> b
         &Instruction::TryMeElse(offset) if offset > 0 => {
             stack.push(index + offset);
         }
-        &Instruction::DefaultRetryMeElse(offset) | &Instruction::RetryMeElse(offset) if offset > 0 => {
+        &Instruction::DefaultRetryMeElse(offset) | &Instruction::RetryMeElse(offset)
+            if offset > 0 =>
+        {
             stack.push(index + offset);
         }
         &Instruction::DynamicElse(_, _, NextOrFail::Next(offset)) if offset > 0 => {

src/machine/compile.rs

@@ -28,17 +28,15 @@ pub(super) fn bootstrapping_compile(
 ) -> Result<(), SessionError> {
     let (wam_prelude, machine_st) = wam.prelude_view_and_machine_st();
 
-    let term_stream = BootstrappingTermStream::from_char_reader(
+    let term_stream = BootstrappingTermStream::from_char_reader(stream, machine_st, listing_src);
-        stream,
-        machine_st,
-        listing_src,
-    );
 
-    let payload = BootstrappingLoadState(
+    let payload =
-        LoadStatePayload::new(wam_prelude.code.len(), term_stream)
+        BootstrappingLoadState(LoadStatePayload::new(wam_prelude.code.len(), term_stream));
-    );
 
-    let loader: Loader<'_, BootstrappingLoadState> = Loader { payload, wam_prelude };
+    let loader: Loader<'_, BootstrappingLoadState> = Loader {
+        payload,
+        wam_prelude,
+    };
 
     loader.load()?;
     Ok(())
@@ -98,8 +96,8 @@ fn derelictize_try_me_else(
             retraction_info.push_record(RetractionRecord::ReplacedDynamicElseOffset(index, *o));
             Some(mem::replace(o, 0))
         }
-        Instruction::DynamicElse(_, _, NextOrFail::Fail(_)) |
+        Instruction::DynamicElse(_, _, NextOrFail::Fail(_))
-        Instruction::DynamicInternalElse(_, _, NextOrFail::Fail(_)) => None,
+        | Instruction::DynamicInternalElse(_, _, NextOrFail::Fail(_)) => None,
         Instruction::TryMeElse(0) => None,
         Instruction::TryMeElse(ref mut o) => {
             retraction_info.push_record(RetractionRecord::ModifiedTryMeElse(index, *o));
@@ -154,8 +152,8 @@ fn merge_indices(
 fn find_outer_choice_instr(code: &Code, mut index: usize) -> usize {
     loop {
         match &code[index] {
-            Instruction::DynamicElse(_, _, NextOrFail::Next(i)) |
+            Instruction::DynamicElse(_, _, NextOrFail::Next(i))
-            Instruction::DynamicInternalElse(_, _, NextOrFail::Next(i))
+            | Instruction::DynamicInternalElse(_, _, NextOrFail::Next(i))
                 if *i > 0 =>
             {
                 index += i;
@@ -170,16 +168,14 @@ fn find_outer_choice_instr(code: &Code, mut index: usize) -> usize {
 fn find_inner_choice_instr(code: &Code, mut index: usize, index_loc: usize) -> usize {
     loop {
         match &code[index] {
-            Instruction::TryMeElse(o) |
+            Instruction::TryMeElse(o) | Instruction::RetryMeElse(o) => {
-            Instruction::RetryMeElse(o) => {
                 if *o > 0 {
                     return index;
                 } else {
                     index = index_loc;
                 }
             }
-            &Instruction::DynamicElse(_, _, next_or_fail) => {
+            &Instruction::DynamicElse(_, _, next_or_fail) => match next_or_fail {
-                match next_or_fail {
                 NextOrFail::Next(i) => {
                     if i == 0 {
                         index = index_loc;
@@ -190,10 +186,8 @@ fn find_inner_choice_instr(code: &Code, mut index: usize, index_loc: usize) -> u
                 NextOrFail::Fail(_) => {
                     index = index_loc;
                 }
-                }
+            },
-            }
+            &Instruction::DynamicInternalElse(_, _, next_or_fail) => match next_or_fail {
-            &Instruction::DynamicInternalElse(_, _, next_or_fail) => {
-                match next_or_fail {
                 NextOrFail::Next(i) => {
                     if i == 0 {
                         index = index_loc;
@@ -204,8 +198,7 @@ fn find_inner_choice_instr(code: &Code, mut index: usize, index_loc: usize) -> u
                 NextOrFail::Fail(_) => {
                     return index;
                 }
-                }
+            },
-            }
             Instruction::TrustMe(_) => {
                 return index;
             }
@@ -215,11 +208,7 @@ fn find_inner_choice_instr(code: &Code, mut index: usize, index_loc: usize) -> u
                         index += v;
                     }
                     IndexingCodePtr::DynamicExternal(v) => match &code[index + v] {
-                        &Instruction::DynamicInternalElse(
+                        &Instruction::DynamicInternalElse(_, _, NextOrFail::Next(0)) => {
-                            _,
-                            _,
-                            NextOrFail::Next(0),
-                        ) => {
                             return index + v;
                         }
                         _ => {
@@ -309,8 +298,7 @@ fn merge_indexed_subsequences(
                         code[inner_try_me_else_loc] = Instruction::TrustMe(o);
                     }
                     _ => {
-                        code[inner_try_me_else_loc] =
+                        code[inner_try_me_else_loc] = Instruction::RetryMeElse(o);
-                            Instruction::RetryMeElse(o);
                     }
                 },
             }
@@ -376,7 +364,9 @@ fn delete_from_skeleton(
     }
 
     if skeleton.core.is_dynamic {
-        skeleton.core.add_retracted_dynamic_clause_info(clause_index_info);
+        skeleton
+            .core
+            .add_retracted_dynamic_clause_info(clause_index_info);
 
         retraction_info.push_record(RetractionRecord::RemovedDynamicSkeletonClause(
             compilation_target,
@@ -409,8 +399,8 @@ fn blunt_leading_choice_instr(
                 code[instr_loc] = Instruction::TryMeElse(*o);
                 return instr_loc;
             }
-            Instruction::DynamicElse(_, _, NextOrFail::Next(_)) |
+            Instruction::DynamicElse(_, _, NextOrFail::Next(_))
-            Instruction::DynamicInternalElse(_, _, NextOrFail::Next(_)) => {
+            | Instruction::DynamicInternalElse(_, _, NextOrFail::Next(_)) => {
                 return instr_loc;
             }
             &mut Instruction::DynamicElse(b, d, NextOrFail::Fail(o)) => {
@@ -422,26 +412,19 @@ fn blunt_leading_choice_instr(
                 code[instr_loc] = Instruction::DynamicElse(b, d, NextOrFail::Next(0));
                 return instr_loc;
             }
-            &mut Instruction::DynamicInternalElse(
+            &mut Instruction::DynamicInternalElse(b, d, NextOrFail::Fail(o)) => {
-                b,
-                d,
-                NextOrFail::Fail(o),
-            ) => {
                 retraction_info.push_record(RetractionRecord::AppendedNextOrFail(
                     instr_loc,
                     NextOrFail::Fail(o),
                 ));
 
-                code[instr_loc] = Instruction::DynamicInternalElse(
+                code[instr_loc] = Instruction::DynamicInternalElse(b, d, NextOrFail::Next(0));
-                    b,
-                    d,
-                    NextOrFail::Next(0),
-                );
 
                 return instr_loc;
             }
             Instruction::TrustMe(o) => {
-                retraction_info.push_record(RetractionRecord::AppendedTrustMe(instr_loc, *o, false));
+                retraction_info
+                    .push_record(RetractionRecord::AppendedTrustMe(instr_loc, *o, false));
 
                 code[instr_loc] = Instruction::TryMeElse(0);
                 return instr_loc + 1;
@@ -481,9 +464,9 @@ fn set_switch_var_offset_to_choice_instr(
     };
 
     match &code[index_loc + v] {
-        Instruction::TryMeElse(_) |
+        Instruction::TryMeElse(_)
-        Instruction::DynamicElse(..) |
+        | Instruction::DynamicElse(..)
-        Instruction::DynamicInternalElse(..) => {}
+        | Instruction::DynamicInternalElse(..) => {}
         _ => {
             set_switch_var_offset(code, index_loc, offset, retraction_info);
         }
@@ -523,9 +506,8 @@ fn internalize_choice_instr_at(
     retraction_info: &mut RetractionInfo,
 ) {
     match &mut code[instr_loc] {
-        Instruction::DynamicElse(_, _, NextOrFail::Fail(_)) |
+        Instruction::DynamicElse(_, _, NextOrFail::Fail(_))
-        Instruction::DynamicInternalElse(_, _, NextOrFail::Fail(_)) => {
+        | Instruction::DynamicInternalElse(_, _, NextOrFail::Fail(_)) => {}
-        }
         Instruction::DynamicElse(_, _, ref mut o @ NextOrFail::Next(0)) => {
             retraction_info.push_record(RetractionRecord::ReplacedDynamicElseOffset(instr_loc, 0));
             *o = NextOrFail::Fail(0);
@@ -554,18 +536,10 @@ fn internalize_choice_instr_at(
 
             match &mut code[instr_loc + o] {
                 Instruction::RevJmpBy(p) if *p == 0 => {
-                    code[instr_loc] = Instruction::DynamicInternalElse(
+                    code[instr_loc] = Instruction::DynamicInternalElse(b, d, NextOrFail::Fail(o));
-                        b,
-                        d,
-                        NextOrFail::Fail(o),
-                    );
                 }
                 _ => {
-                    code[instr_loc] = Instruction::DynamicInternalElse(
+                    code[instr_loc] = Instruction::DynamicInternalElse(b, d, NextOrFail::Next(o));
-                        b,
-                        d,
-                        NextOrFail::Next(o),
-                    );
                 }
             }
         }
@@ -609,23 +583,20 @@ fn thread_choice_instr_at_to(
                 *o = target_loc - instr_loc;
                 return;
             }
-            Instruction::DynamicElse(_, _, NextOrFail::Next(ref mut o)) |
+            Instruction::DynamicElse(_, _, NextOrFail::Next(ref mut o))
-            Instruction::DynamicInternalElse(
+            | Instruction::DynamicInternalElse(_, _, NextOrFail::Next(ref mut o))
-                _,
+                if target_loc >= instr_loc =>
-                _,
+            {
-                NextOrFail::Next(ref mut o),
-            ) if target_loc >= instr_loc => {
                 retraction_info
                     .push_record(RetractionRecord::ReplacedDynamicElseOffset(instr_loc, *o));
                 *o = target_loc - instr_loc;
                 return;
             }
-            Instruction::DynamicElse(_, _, NextOrFail::Next(o)) |
+            Instruction::DynamicElse(_, _, NextOrFail::Next(o))
-            Instruction::DynamicInternalElse(_, _, NextOrFail::Next(o)) => {
+            | Instruction::DynamicInternalElse(_, _, NextOrFail::Next(o)) => {
                 instr_loc += *o;
             }
-            Instruction::TryMeElse(o)
+            Instruction::TryMeElse(o) | Instruction::RetryMeElse(o) => {
-            | Instruction::RetryMeElse(o) => {
                 instr_loc += *o;
             }
             Instruction::RevJmpBy(ref mut o) if instr_loc >= target_loc => {
@@ -642,7 +613,8 @@ fn thread_choice_instr_at_to(
             {
                 retraction_info.push_record(RetractionRecord::AppendedNextOrFail(instr_loc, *fail));
 
-                code[instr_loc] = instr!("dynamic_else",
+                code[instr_loc] = instr!(
+                    "dynamic_else",
                     birth,
                     death,
                     NextOrFail::Next(target_loc - instr_loc)
@@ -653,14 +625,13 @@ fn thread_choice_instr_at_to(
             Instruction::DynamicElse(_, _, NextOrFail::Fail(o)) if *o > 0 => {
                 instr_loc += *o;
             }
-            &mut Instruction::DynamicInternalElse(
+            &mut Instruction::DynamicInternalElse(birth, death, ref mut fail)
-                birth,
+                if target_loc >= instr_loc =>
-                death,
+            {
-                ref mut fail,
-            ) if target_loc >= instr_loc => {
                 retraction_info.push_record(RetractionRecord::AppendedNextOrFail(instr_loc, *fail));
 
-                code[instr_loc] = instr!("dynamic_internal_else",
+                code[instr_loc] = instr!(
+                    "dynamic_internal_else",
                     birth,
                     death,
                     NextOrFail::Next(target_loc - instr_loc)
@@ -668,9 +639,7 @@ fn thread_choice_instr_at_to(
 
                 return;
             }
-            Instruction::DynamicInternalElse(_, _, NextOrFail::Fail(o))
+            Instruction::DynamicInternalElse(_, _, NextOrFail::Fail(o)) if *o > 0 => {
-                if *o > 0 =>
-            {
                 instr_loc += *o;
             }
             Instruction::TrustMe(ref mut o) if target_loc >= instr_loc => {
@@ -711,8 +680,7 @@ fn remove_non_leading_clause(
 
             None
         }
-        Instruction::TrustMe(_) => {
+        Instruction::TrustMe(_) => match &mut code[preceding_choice_instr_loc] {
-            match &mut code[preceding_choice_instr_loc] {
             Instruction::RetryMeElse(o) => {
                 retraction_info.push_record(RetractionRecord::ModifiedRetryMeElse(
                     preceding_choice_instr_loc,
@@ -736,8 +704,7 @@ fn remove_non_leading_clause(
             _ => {
                 unreachable!();
             }
-            }
+        },
-        }
         _ => {
             unreachable!();
         }
@@ -988,11 +955,7 @@ fn prepend_compiled_clause(
                     Instruction::TryMeElse(ref mut o) if *o == 0 => {
                         *o = prepend_queue_len - 2;
                     }
-                    Instruction::DynamicInternalElse(
+                    Instruction::DynamicInternalElse(_, _, ref mut o @ NextOrFail::Next(0)) => {
-                        _,
-                        _,
-                        ref mut o @ NextOrFail::Next(0),
-                    ) => {
                         *o = NextOrFail::Fail(prepend_queue_len - 2);
                     }
                     _ => {
@@ -1258,7 +1221,11 @@ fn print_overwrite_warning(
         _ => {}
     }
 
-    println!("Warning: overwriting {}/{} because the clauses are discontiguous", key.0.as_str(), key.1);
+    println!(
+        "Warning: overwriting {}/{} because the clauses are discontiguous",
+        key.0.as_str(),
+        key.1
+    );
 }
 
 impl<'a, LS: LoadState<'a>> Loader<'a, LS> {
@@ -1270,8 +1237,9 @@ impl<'a, LS: LoadState<'a>> Loader<'a, LS> {
 
             if let Some(path_str) = load_context.path.to_str() {
                 if !path_str.is_empty() {
-                    return Some(LS::machine_st(&mut self.payload).atom_tbl.build_with(
+                    return Some(AtomTable::build_with(
-                        path_str
+                        &LS::machine_st(&mut self.payload).atom_tbl,
+                        path_str,
                     ));
                 }
             }
@@ -1290,10 +1258,7 @@ impl<'a, LS: LoadState<'a>> Loader<'a, LS> {
         let clause = self.try_term_to_tl(term, &mut preprocessor)?;
         // let queue = preprocessor.parse_queue(self)?;
 
-        let mut cg = CodeGenerator::new(
+        let mut cg = CodeGenerator::new(&LS::machine_st(&mut self.payload).atom_tbl, settings);
-            &mut LS::machine_st(&mut self.payload).atom_tbl,
-            settings,
-        );
 
         let clause_code = cg.compile_predicate(vec![clause])?;
 
@@ -1323,10 +1288,7 @@ impl<'a, LS: LoadState<'a>> Loader<'a, LS> {
             clauses.push(self.try_term_to_tl(term, &mut preprocessor)?);
         }
 
-        let mut cg = CodeGenerator::new(
+        let mut cg = CodeGenerator::new(&LS::machine_st(&mut self.payload).atom_tbl, settings);
-            &mut LS::machine_st(&mut self.payload).atom_tbl,
-            settings,
-        );
 
         let mut code = cg.compile_predicate(clauses)?;
 
@@ -1361,12 +1323,13 @@ impl<'a, LS: LoadState<'a>> Loader<'a, LS> {
                         .clause_clause_locs
                         .extend(&clause_clause_locs.make_contiguous()[0..]);
 
-                    self.payload.retraction_info
+                    self.payload.retraction_info.push_record(
-                        .push_record(RetractionRecord::SkeletonClauseTruncateBack(
+                        RetractionRecord::SkeletonClauseTruncateBack(
                             predicates.compilation_target,
                             key,
                             skeleton_clause_len,
-                        ));
+                        ),
+                    );
                 }
                 None => {
                     cg.skeleton
@@ -1376,11 +1339,7 @@ impl<'a, LS: LoadState<'a>> Loader<'a, LS> {
 
                     let skeleton = cg.skeleton;
 
-                    self.add_extensible_predicate(
+                    self.add_extensible_predicate(key, skeleton, predicates.compilation_target);
-                        key,
-                        skeleton,
-                        predicates.compilation_target,
-                    );
                 }
             };
 
@@ -1450,11 +1409,7 @@ impl<'a, LS: LoadState<'a>> Loader<'a, LS> {
                 let mut skeleton = LocalPredicateSkeleton::new();
                 skeleton.clause_clause_locs = clause_clause_locs;
 
-                self.add_local_extensible_predicate(
+                self.add_local_extensible_predicate(*compilation_target, *key, skeleton);
-                    *compilation_target,
-                    *key,
-                    skeleton,
-                );
             }
         }
     }
@@ -1490,11 +1445,7 @@ impl<'a, LS: LoadState<'a>> Loader<'a, LS> {
                 let mut skeleton = LocalPredicateSkeleton::new();
                 skeleton.clause_clause_locs.push_front(code_len);
 
-                self.add_local_extensible_predicate(
+                self.add_local_extensible_predicate(*compilation_target, *key, skeleton);
-                    *compilation_target,
-                    *key,
-                    skeleton,
-                );
             }
         }
     }
@@ -1530,11 +1481,7 @@ impl<'a, LS: LoadState<'a>> Loader<'a, LS> {
                 let mut skeleton = LocalPredicateSkeleton::new();
                 skeleton.clause_clause_locs.push_back(code_len);
 
-                self.add_local_extensible_predicate(
+                self.add_local_extensible_predicate(*compilation_target, *key, skeleton);
-                    *compilation_target,
-                    *key,
-                    skeleton,
-                );
             }
         }
     }
@@ -1606,7 +1553,8 @@ impl<'a, LS: LoadState<'a>> Loader<'a, LS> {
 
                 skeleton.core.clause_clause_locs.push_back(code_len);
 
-                self.payload.retraction_info
+                self.payload
+                    .retraction_info
                     .push_record(RetractionRecord::SkeletonClausePopBack(
                         compilation_target,
                         key,
@@ -1624,8 +1572,7 @@ impl<'a, LS: LoadState<'a>> Loader<'a, LS> {
 
                 self.push_back_to_local_predicate_skeleton(&compilation_target, &key, code_len);
 
-                let code_index =
+                let code_index = self.get_or_insert_code_index(key, compilation_target);
-                    self.get_or_insert_code_index(key, compilation_target);
 
                 if let Some(new_code_ptr) = result {
                     set_code_index(
@@ -1646,7 +1593,8 @@ impl<'a, LS: LoadState<'a>> Loader<'a, LS> {
                 skeleton.core.clause_clause_locs.push_front(code_len);
                 skeleton.core.clause_assert_margin += 1;
 
-                self.payload.retraction_info
+                self.payload
+                    .retraction_info
                     .push_record(RetractionRecord::SkeletonClausePopFront(
                         compilation_target,
                         key,
@@ -1666,8 +1614,7 @@ impl<'a, LS: LoadState<'a>> Loader<'a, LS> {
 
                 self.push_front_to_local_predicate_skeleton(&compilation_target, &key, code_len);
 
-                let code_index =
+                let code_index = self.get_or_insert_code_index(key, compilation_target);
-                    self.get_or_insert_code_index(key, compilation_target);
 
                 set_code_index(
                     &mut self.payload.retraction_info,
@@ -1698,19 +1645,17 @@ impl<'a, LS: LoadState<'a>> Loader<'a, LS> {
             .opt_arg_index_key
             .switch_on_term_loc()
         {
-            Some(index_loc) => {
+            Some(index_loc) => find_inner_choice_instr(
-                find_inner_choice_instr(
                 &self.wam_prelude.code,
                 skeleton.clauses[target_pos].clause_start,
                 index_loc,
-                )
+            ),
-            }
             None => skeleton.clauses[target_pos].clause_start,
         };
 
         match &mut self.wam_prelude.code[clause_loc] {
-            Instruction::DynamicElse(_, ref mut d, _) |
+            Instruction::DynamicElse(_, ref mut d, _)
-            Instruction::DynamicInternalElse(_, ref mut d, _) => {
+            | Instruction::DynamicInternalElse(_, ref mut d, _) => {
                 *d = Death::Finite(LS::machine_st(&mut self.payload).global_clock);
             }
             _ => unreachable!(),
@@ -1797,8 +1742,8 @@ impl<'a, LS: LoadState<'a>> Loader<'a, LS> {
                             skeleton.clauses[target_pos + 1].clause_start =
                                 skeleton.clauses[target_pos].clause_start;
 
-                            let update_code_index = target_pos == 0 &&
+                            let update_code_index = target_pos == 0
-                                skeleton.clauses[target_pos + 1]
+                                && skeleton.clauses[target_pos + 1]
                                     .opt_arg_index_key
                                     .switch_on_term_loc()
                                     .is_none();
@@ -1964,7 +1909,8 @@ impl<'a, LS: LoadState<'a>> Loader<'a, LS> {
                                 index_loc,
                             );
 
-                            let lower_bound_clause_start = skeleton.clauses[lower_bound].clause_start;
+                            let lower_bound_clause_start =
+                                skeleton.clauses[lower_bound].clause_start;
                             let preceding_choice_instr_loc;
 
                             match &mut code[clause_start] {
@@ -2093,13 +2039,8 @@ impl<'a, LS: LoadState<'a>> Loader<'a, LS> {
         clause_clauses: ClauseIter,
         append_or_prepend: AppendOrPrepend,
     ) -> Result<(), SessionError> {
-        let clause_predicates = clause_clauses.map(|(head, body)| {
+        let clause_predicates = clause_clauses
-            Term::Clause(
+            .map(|(head, body)| Term::Clause(Cell::default(), atom!("$clause"), vec![head, body]));
-                Cell::default(),
-                atom!("$clause"),
-                vec![head, body],
-            )
-        });
 
         let clause_clause_compilation_target = match compilation_target {
             CompilationTarget::User => CompilationTarget::Module(atom!("builtins")),
@@ -2132,21 +2073,21 @@ impl<'a, LS: LoadState<'a>> Loader<'a, LS> {
                     .cloned()
                     .collect()
             }
-            Some(skeleton) => {
+            Some(skeleton) => skeleton.core.clause_clause_locs.make_contiguous()
-                skeleton.core.clause_clause_locs.make_contiguous()[0..num_clause_predicates]
+                [0..num_clause_predicates]
                 .iter()
                 .cloned()
-                    .collect()
+                .collect(),
-            }
             None => {
                 unreachable!()
             }
         };
 
-        match self.wam_prelude.indices.get_predicate_skeleton_mut(
+        match self
-            &clause_clause_compilation_target,
+            .wam_prelude
-            &(atom!("$clause"), 2),
+            .indices
-        ) {
+            .get_predicate_skeleton_mut(&clause_clause_compilation_target, &(atom!("$clause"), 2))
+        {
             Some(skeleton) if append_or_prepend.is_append() => {
                 for _ in 0..num_clause_predicates {
                     skeleton.core.clause_clause_locs.pop_back();
@@ -2270,20 +2211,20 @@ impl<'a, LS: LoadState<'a>> Loader<'a, LS> {
                         println!(
                             "Warning: overwriting multifile predicate {}:{}/{} because \
                                   it was not locally declared multifile.",
-                            self.payload.predicates.compilation_target, key.0.as_str(), key.1
+                            self.payload.predicates.compilation_target,
+                            key.0.as_str(),
+                            key.1
                         );
                     }
 
-                    if let Some(skeleton) = self
+                    if let Some(skeleton) = self.wam_prelude.indices.remove_predicate_skeleton(
-                        .wam_prelude
+                        &self.payload.predicates.compilation_target,
-                        .indices
+                        &key,
-                        .remove_predicate_skeleton(&self.payload.predicates.compilation_target, &key)
+                    ) {
-                    {
                         let compilation_target = self.payload.predicates.compilation_target;
 
                         if predicate_info.is_dynamic {
-                            let clause_clause_compilation_target =
+                            let clause_clause_compilation_target = match compilation_target {
-                                match compilation_target {
                                 CompilationTarget::User => {
                                     CompilationTarget::Module(atom!("builtins"))
                                 }
@@ -2301,11 +2242,7 @@ impl<'a, LS: LoadState<'a>> Loader<'a, LS> {
                         }
 
                         self.payload.retraction_info.push_record(
-                            RetractionRecord::RemovedSkeleton(
+                            RetractionRecord::RemovedSkeleton(compilation_target, key, skeleton),
-                                compilation_target,
-                                key,
-                                skeleton,
-                            ),
                         );
                     }
                 }
@@ -2328,9 +2265,7 @@ impl<'a, LS: LoadState<'a>> Loader<'a, LS> {
                 match self.wam_prelude.indices.modules.get_mut(&filename) {
                     Some(ref mut module) => {
                         let index_ptr = code_index.get();
-                        let code_index = module.code_dir.entry(key)
+                        let code_index = module.code_dir.entry(key).or_insert(code_index).clone();
-                            .or_insert(code_index)
-                            .clone();
 
                         set_code_index(
                             &mut self.payload.retraction_info,
@@ -2349,8 +2284,10 @@ impl<'a, LS: LoadState<'a>> Loader<'a, LS> {
             LS::machine_st(&mut self.payload).global_clock += 1;
 
             let clause_clauses_len = self.payload.clause_clauses.len();
-            let clauses_vec: Vec<_> = self.payload
+            let clauses_vec: Vec<_> = self
-                .clause_clauses.drain(0..std::cmp::min(predicates_len, clause_clauses_len))
+                .payload
+                .clause_clauses
+                .drain(0..std::cmp::min(predicates_len, clause_clauses_len))
                 .collect();
 
             let compilation_target = self.payload.predicates.compilation_target;
@@ -2374,10 +2311,7 @@ impl Machine {
         module_name: HeapCellValue,
         key: PredicateKey,
     ) -> CodeIndex {
-        let mut loader: Loader<'_, InlineLoadState<'_>> = Loader::new(
+        let mut loader: Loader<'_, InlineLoadState<'_>> = Loader::new(self, InlineTermStream {});
-            self,
-            InlineTermStream {},
-        );
 
         let module_name = if module_name.get_tag() == HeapCellValueTag::Atom {
             cell_as_atom!(module_name)
@@ -2394,10 +2328,8 @@ impl Machine {
         vars: &[Term],
     ) -> Result<(), SessionError> {
         let mut compile = || {
-            let mut loader: Loader<'_, InlineLoadState<'_>> = Loader::new(
+            let mut loader: Loader<'_, InlineLoadState<'_>> =
-                self,
+                Loader::new(self, InlineTermStream {});
-                InlineTermStream {},
-            );
 
             let term = loader.read_term_from_heap(term_loc)?;
             let clause = build_rule_body(vars, term);

src/machine/copier.rs

@@ -91,12 +91,16 @@ impl<T: CopierTarget> CopyTermState<T> {
             self.target.push(hcv);
         }
 
-        let cdr = self.target.store(self.target.deref(heap_loc_as_cell!(addr + 1)));
+        let cdr = self
+            .target
+            .store(self.target.deref(heap_loc_as_cell!(addr + 1)));
 
         if !cdr.is_var() {
             self.trail_list_cell(addr + 1, threshold);
         } else {
-            let car = self.target.store(self.target.deref(heap_loc_as_cell!(addr)));
+            let car = self
+                .target
+                .store(self.target.deref(heap_loc_as_cell!(addr)));
 
             if !car.is_var() {
                 self.trail_list_cell(addr, threshold);
@@ -377,7 +381,8 @@ mod tests {
         let a_atom = atom!("a");
         let b_atom = atom!("b");
 
-        wam.machine_st.heap
+        wam.machine_st
+            .heap
             .extend(functor!(f_atom, [atom(a_atom), atom(b_atom)]));
 
         assert_eq!(wam.machine_st.heap[0], atom_as_cell!(f_atom, 2));
@@ -401,20 +406,26 @@ mod tests {
 
         wam.machine_st.heap.clear();
 
-        let pstr_var_cell = put_partial_string(&mut wam.machine_st.heap, "abc ", &mut wam.machine_st.atom_tbl);
+        let pstr_var_cell =
+            put_partial_string(&mut wam.machine_st.heap, "abc ", &wam.machine_st.atom_tbl);
         let pstr_cell = wam.machine_st.heap[pstr_var_cell.get_value() as usize];
 
         wam.machine_st.heap.pop();
         wam.machine_st.heap.push(pstr_loc_as_cell!(2));
 
-        let pstr_second_var_cell = put_partial_string(&mut wam.machine_st.heap, "def", &mut wam.machine_st.atom_tbl);
+        let pstr_second_var_cell =
+            put_partial_string(&mut wam.machine_st.heap, "def", &wam.machine_st.atom_tbl);
         let pstr_second_cell = wam.machine_st.heap[pstr_second_var_cell.get_value() as usize];
 
         wam.machine_st.heap.pop();
-        wam.machine_st.heap.push(pstr_loc_as_cell!(wam.machine_st.heap.len() + 1));
+        wam.machine_st
+            .heap
+            .push(pstr_loc_as_cell!(wam.machine_st.heap.len() + 1));
 
         wam.machine_st.heap.push(pstr_offset_as_cell!(0));
-        wam.machine_st.heap.push(fixnum_as_cell!(Fixnum::build_with(0i64)));
+        wam.machine_st
+            .heap
+            .push(fixnum_as_cell!(Fixnum::build_with(0i64)));
 
         {
             let wam = TermCopyingMockWAM { wam: &mut wam };
@@ -428,14 +439,20 @@ mod tests {
         assert_eq!(wam.machine_st.heap[2], pstr_second_cell);
         assert_eq!(wam.machine_st.heap[3], pstr_loc_as_cell!(4));
         assert_eq!(wam.machine_st.heap[4], pstr_offset_as_cell!(0));
-        assert_eq!(wam.machine_st.heap[5], fixnum_as_cell!(Fixnum::build_with(0i64)));
+        assert_eq!(
+            wam.machine_st.heap[5],
+            fixnum_as_cell!(Fixnum::build_with(0i64))
+        );
 
         assert_eq!(wam.machine_st.heap[7], pstr_cell);
         assert_eq!(wam.machine_st.heap[8], pstr_loc_as_cell!(9));
         assert_eq!(wam.machine_st.heap[9], pstr_second_cell);
         assert_eq!(wam.machine_st.heap[10], pstr_loc_as_cell!(11));
         assert_eq!(wam.machine_st.heap[11], pstr_offset_as_cell!(7));
-        assert_eq!(wam.machine_st.heap[12], fixnum_as_cell!(Fixnum::build_with(0i64)));
+        assert_eq!(
+            wam.machine_st.heap[12],
+            fixnum_as_cell!(Fixnum::build_with(0i64))
+        );
 
         wam.machine_st.heap.clear();
 

src/machine/disjuncts.rs

@@ -108,7 +108,10 @@ pub struct BranchInfo {
 
 impl BranchInfo {
     fn new(branch_num: BranchNumber) -> Self {
-        Self { branch_num, chunks: vec![] }
+        Self {
+            branch_num,
+            chunks: vec![],
+        }
     }
 }
 
@@ -179,14 +182,13 @@ pub struct VarData {
 
 impl VarData {
     fn emit_initial_get_level(&mut self, build_stack: &mut ChunkedTermVec) {
-        let global_cut_var_num =
+        let global_cut_var_num = if let &Some(global_cut_var_num) = &self.global_cut_var_num {
-            if let &Some(global_cut_var_num) = &self.global_cut_var_num {
             match &self.records[global_cut_var_num].allocation {
                 VarAlloc::Perm(..) => Some(global_cut_var_num),
                 VarAlloc::Temp { term_loc, .. } if term_loc.chunk_num() > 0 => {
                     Some(global_cut_var_num)
                 }
-                    _ => None
+                _ => None,
             }
         } else {
             None
@@ -194,7 +196,8 @@ impl VarData {
 
         if let Some(global_cut_var_num) = global_cut_var_num {
             let term = QueryTerm::GetLevel(global_cut_var_num);
-            self.records[global_cut_var_num].allocation = VarAlloc::Perm(0, PermVarAllocation::Pending);
+            self.records[global_cut_var_num].allocation =
+                VarAlloc::Perm(0, PermVarAllocation::Pending);
 
             match build_stack.front_mut() {
                 Some(ChunkedTerms::Branch(_)) => {
@@ -254,11 +257,14 @@ impl VariableClassifier {
 
     pub fn classify_fact(mut self, term: Term) -> Result<ClassifyFactResult, CompilationError> {
         self.classify_head_variables(&term)?;
-        Ok((term, self.branch_map.separate_and_classify_variables(
+        Ok((
+            term,
+            self.branch_map.separate_and_classify_variables(
                 self.var_num,
                 self.global_cut_var_num,
                 self.current_chunk_num,
-        )))
+            ),
+        ))
     }
 
     pub fn classify_rule<'a, LS: LoadState<'a>>(
@@ -346,9 +352,13 @@ impl VariableClassifier {
     }
 
     fn probe_body_var(&mut self, var_info: VarInfo) {
-        let term_loc = self.current_chunk_type.to_gen_context(self.current_chunk_num);
+        let term_loc = self
+            .current_chunk_type
+            .to_gen_context(self.current_chunk_num);
 
-        let branch_info_v = self.branch_map.entry(var_info.var_ptr.clone())
+        let branch_info_v = self
+            .branch_map
+            .entry(var_info.var_ptr.clone())
             .or_insert_with(|| vec![]);
 
         let needs_new_branch = if let Some(last_bi) = branch_info_v.last() {
@@ -396,12 +406,14 @@ impl VariableClassifier {
 
     fn classify_head_variables(&mut self, term: &Term) -> Result<(), CompilationError> {
         match term {
-            Term::Clause(..) | Term::Literal(_, Literal::Atom(_)) => {
+            Term::Clause(..) | Term::Literal(_, Literal::Atom(_)) => {}
-            }
             _ => return Err(CompilationError::InvalidRuleHead),
         }
 
-        let mut classify_info = ClassifyInfo { arg_c: 1, arity: term.arity() };
+        let mut classify_info = ClassifyInfo {
+            arg_c: 1,
+            arity: term.arity(),
+        };
 
         match term {
             Term::Clause(_, _, terms) => {
@@ -414,13 +426,16 @@ impl VariableClassifier {
                             // the body of the if let here is an inlined
                             // "probe_head_var". note the difference between it
                             // and "probe_body_var".
-                            let branch_info_v = self.branch_map.entry(var_ptr.clone())
+                            let branch_info_v = self
+                                .branch_map
+                                .entry(var_ptr.clone())
                                 .or_insert_with(|| vec![]);
 
                             let needs_new_branch = branch_info_v.is_empty();
 
                             if needs_new_branch {
-                                branch_info_v.push(BranchInfo::new(self.current_branch_num.clone()));
+                                branch_info_v
+                                    .push(BranchInfo::new(self.current_branch_num.clone()));
                             }
 
                             let branch_info = branch_info_v.last_mut().unwrap();
@@ -509,13 +524,11 @@ impl VariableClassifier {
 
                     self.probe_in_situ_var(var_num);
 
-                    build_stack.push_chunk_term(
+                    build_stack.push_chunk_term(if is_global {
-                        if is_global {
                         QueryTerm::GlobalCut(var_num)
                     } else {
                         QueryTerm::LocalCut(var_num)
-                        }
+                    });
-                    );
                 }
                 TraversalState::Fail => {
                     build_stack.push_chunk_term(QueryTerm::Fail);
@@ -539,22 +552,28 @@ impl VariableClassifier {
                             classifier.probe_body_term(arg_c + 1, terms.len(), term);
                         }
 
-                        build_stack.push_chunk_term(
+                        build_stack.push_chunk_term(clause_to_query_term(
-                            clause_to_query_term(
                             loader,
                             name,
                             terms,
                             classifier.call_policy,
-                            ),
+                        ));
-                        );
                     };
 
                     match term {
-                        Term::Clause(_, name @ (atom!("->") | atom!(";") | atom!(",")), mut terms) if terms.len() == 3 => {
+                        Term::Clause(
+                            _,
+                            name @ (atom!("->") | atom!(";") | atom!(",")),
+                            mut terms,
+                        ) if terms.len() == 3 => {
                             if let Some(last_arg) = terms.last() {
                                 if let Term::Literal(_, Literal::CodeIndex(_)) = last_arg {
                                     terms.pop();
-                                    state_stack.push(TraversalState::Term(Term::Clause(Cell::default(), name, terms)));
+                                    state_stack.push(TraversalState::Term(Term::Clause(
+                                        Cell::default(),
+                                        name,
+                                        terms,
+                                    )));
                                 } else {
                                     add_chunk(self, name, terms);
                                 }
@@ -610,8 +629,11 @@ impl VariableClassifier {
                                 state_stack.push(TraversalState::AddBranchNum(branch_num));
                             }
 
-                            if let TraversalState::BuildDisjunct(build_stack_len) = state_stack[final_disjunct_loc] {
+                            if let TraversalState::BuildDisjunct(build_stack_len) =
-                                state_stack[final_disjunct_loc] = TraversalState::BuildFinalDisjunct(build_stack_len);
+                                state_stack[final_disjunct_loc]
+                            {
+                                state_stack[final_disjunct_loc] =
+                                    TraversalState::BuildFinalDisjunct(build_stack_len);
                             }
 
                             self.current_chunk_type = ChunkType::Mid;
@@ -621,18 +643,30 @@ impl VariableClassifier {
                             let then_term = terms.pop().unwrap();
                             let if_term = terms.pop().unwrap();
 
-                            let prev_b = if matches!(state_stack.last(), Some(TraversalState::RemoveBranchNum)) {
+                            let prev_b = if matches!(
+                                state_stack.last(),
+                                Some(TraversalState::RemoveBranchNum)
+                            ) {
                                 // check if the second-to-last element is a regular BuildDisjunct, as we don't
                                 // want to add GetPrevLevel in case of a TrustMe.
-                                matches!(state_stack.iter().rev().nth(1), Some(TraversalState::BuildDisjunct(..)))
+                                matches!(
+                                    state_stack.iter().rev().nth(1),
+                                    Some(TraversalState::BuildDisjunct(..))
+                                )
                             } else {
                                 false
                             };
 
                             state_stack.push(TraversalState::Term(then_term));
-                            state_stack.push(TraversalState::Cut { var_num: self.var_num, is_global: false });
+                            state_stack.push(TraversalState::Cut {
+                                var_num: self.var_num,
+                                is_global: false,
+                            });
                             state_stack.push(TraversalState::Term(if_term));
-                            state_stack.push(TraversalState::GetCutPoint { var_num: self.var_num, prev_b });
+                            state_stack.push(TraversalState::GetCutPoint {
+                                var_num: self.var_num,
+                                prev_b,
+                            });
 
                             self.var_num += 1;
                         }
@@ -643,12 +677,22 @@ impl VariableClassifier {
                             build_stack.reserve_branch(2);
 
                             state_stack.push(TraversalState::BuildFinalDisjunct(build_stack_len));
-                            state_stack.push(TraversalState::Term(Term::Clause(Cell::default(), atom!("$succeed"), vec![])));
+                            state_stack.push(TraversalState::Term(Term::Clause(
+                                Cell::default(),
+                                atom!("$succeed"),
+                                vec![],
+                            )));
                             state_stack.push(TraversalState::BuildDisjunct(build_stack_len));
                             state_stack.push(TraversalState::Fail);
-                            state_stack.push(TraversalState::Cut { var_num: self.var_num, is_global: false });
+                            state_stack.push(TraversalState::Cut {
+                                var_num: self.var_num,
+                                is_global: false,
+                            });
                             state_stack.push(TraversalState::Term(not_term));
-                            state_stack.push(TraversalState::GetCutPoint { var_num: self.var_num, prev_b: true });
+                            state_stack.push(TraversalState::GetCutPoint {
+                                var_num: self.var_num,
+                                prev_b: true,
+                            });
 
                             self.current_chunk_type = ChunkType::Mid;
                             self.current_chunk_num += 1;
@@ -668,15 +712,13 @@ impl VariableClassifier {
                                         build_stack.add_chunk();
                                     }
 
-                                    build_stack.push_chunk_term(
+                                    build_stack.push_chunk_term(qualified_clause_to_query_term(
-                                        qualified_clause_to_query_term(
                                         loader,
                                         module_name,
                                         predicate_name,
                                         vec![],
                                         self.call_policy,
-                                        ),
+                                    ));
-                                    );
                                 }
                                 (
                                     Term::Literal(_, Literal::Atom(module_name)),
@@ -690,15 +732,13 @@ impl VariableClassifier {
                                         self.probe_body_term(arg_c + 1, terms.len(), term);
                                     }
 
-                                    build_stack.push_chunk_term(
+                                    build_stack.push_chunk_term(qualified_clause_to_query_term(
-                                        qualified_clause_to_query_term(
                                         loader,
                                         module_name,
                                         name,
                                         terms,
                                         self.call_policy,
-                                        ),
+                                    ));
-                                    );
                                 }
                                 (module_name, predicate_name) => {
                                     if update_chunk_data(self, atom!("call"), 2) {
@@ -711,18 +751,18 @@ impl VariableClassifier {
                                     terms.push(module_name);
                                     terms.push(predicate_name);
 
-                                    build_stack.push_chunk_term(
+                                    build_stack.push_chunk_term(clause_to_query_term(
-                                        clause_to_query_term(
                                         loader,
                                         atom!("call"),
                                         vec![Term::Clause(Cell::default(), atom!(":"), terms)],
                                         self.call_policy,
-                                        ),
+                                    ));
-                                    );
                                 }
                             }
                         }
-                        Term::Clause(_, atom!("$call_with_inference_counting"), mut terms) if terms.len() == 1 => {
+                        Term::Clause(_, atom!("$call_with_inference_counting"), mut terms)
+                            if terms.len() == 1 =>
+                        {
                             state_stack.push(TraversalState::ResetCallPolicy(self.call_policy));
                             state_stack.push(TraversalState::Term(terms.pop().unwrap()));
 
@@ -738,14 +778,12 @@ impl VariableClassifier {
 
                             self.probe_body_term(1, 1, &var);
 
-                            build_stack.push_chunk_term(
+                            build_stack.push_chunk_term(clause_to_query_term(
-                                clause_to_query_term(
                                 loader,
                                 atom!("call"),
                                 vec![var],
                                 self.call_policy,
-                                ),
+                            ));
-                            );
                         }
                         Term::Literal(_, Literal::Atom(atom!("!")) | Literal::Char('!')) => {
                             if self.global_cut_var_num.is_none() {
@@ -765,14 +803,12 @@ impl VariableClassifier {
                                 build_stack.add_chunk();
                             }
 
-                            build_stack.push_chunk_term(
+                            build_stack.push_chunk_term(clause_to_query_term(
-                                clause_to_query_term(
                                 loader,
                                 name,
                                 vec![],
                                 self.call_policy,
-                                ),
+                            ));
-                            );
                         }
                         _ => {
                             return Err(CompilationError::InadmissibleQueryTerm);
@@ -800,8 +836,7 @@ impl BranchMap {
         };
 
         for (var, branches) in self.iter_mut() {
-            let (mut var_num, var_num_incr) =
+            let (mut var_num, var_num_incr) = if let Var::InSitu(var_num) = *var.borrow() {
-                if let Var::InSitu(var_num) = *var.borrow() {
                 (var_num, false)
             } else {
                 (var_data.records.len(), true)
@@ -813,7 +848,8 @@ impl BranchMap {
                     var_data.records.push(VariableRecord::default());
                 }
 
-                if branch.chunks.len() <= 1 { // true iff var is a temporary variable.
+                if branch.chunks.len() <= 1 {
+                    // true iff var is a temporary variable.
                     debug_assert_eq!(branch.chunks.len(), 1);
 
                     let chunk = &mut branch.chunks[0];
@@ -822,7 +858,9 @@ impl BranchMap {
                     for var_info in chunk.vars.iter_mut() {
                         if var_info.lvl == Level::Shallow {
                             let term_loc = var_info.chunk_type.to_gen_context(chunk.chunk_num);
-                            temp_var_data.use_set.insert((term_loc, var_info.classify_info.arg_c));
+                            temp_var_data
+                                .use_set
+                                .insert((term_loc, var_info.classify_info.arg_c));
                         }
                     }
 

src/machine/heap.rs

@@ -130,11 +130,7 @@ pub fn print_heap_terms<'a, I: Iterator<Item = &'a HeapCellValue>>(heap: I, h: u
 }
 
 #[inline]
-pub(crate) fn put_complete_string(
+pub(crate) fn put_complete_string(heap: &mut Heap, s: &str, atom_tbl: &AtomTable) -> HeapCellValue {
-    heap: &mut Heap,
-    s: &str,
-    atom_tbl: &mut AtomTable,
-) -> HeapCellValue {
     match allocate_pstr(heap, s, atom_tbl) {
         Some(h) => {
             heap.pop(); // pop the trailing variable cell from the heap planted by allocate_pstr.
@@ -157,11 +153,7 @@ pub(crate) fn put_complete_string(
 }
 
 #[inline]
-pub(crate) fn put_partial_string(
+pub(crate) fn put_partial_string(heap: &mut Heap, s: &str, atom_tbl: &AtomTable) -> HeapCellValue {
-    heap: &mut Heap,
-    s: &str,
-    atom_tbl: &mut AtomTable,
-) -> HeapCellValue {
     match allocate_pstr(heap, s, atom_tbl) {
         Some(h) => {
             pstr_loc_as_cell!(h)
@@ -173,11 +165,7 @@ pub(crate) fn put_partial_string(
 }
 
 #[inline]
-pub(crate) fn allocate_pstr(
+pub(crate) fn allocate_pstr(heap: &mut Heap, mut src: &str, atom_tbl: &AtomTable) -> Option<usize> {
-    heap: &mut Heap,
-    mut src: &str,
-    atom_tbl: &mut AtomTable,
-) -> Option<usize> {
     let orig_h = heap.len();
 
     loop {

src/machine/load_state.rs

@@ -63,21 +63,27 @@ fn add_op_decl_as_module_export<'a, LS: LoadState<'a>>(
 
     match op_decl.insert_into_op_dir(wam_op_dir) {
         Some(op_desc) => {
-            payload.retraction_info.push_record(RetractionRecord::ReplacedUserOp(
+            payload
-                *op_decl,
+                .retraction_info
-                op_desc,
+                .push_record(RetractionRecord::ReplacedUserOp(*op_decl, op_desc));
-            ));
 
             payload.module_op_exports.push((*op_decl, Some(op_desc)));
         }
         None => {
-            payload.retraction_info.push_record(RetractionRecord::AddedUserOp(*op_decl));
+            payload
+                .retraction_info
+                .push_record(RetractionRecord::AddedUserOp(*op_decl));
             payload.module_op_exports.push((*op_decl, None));
         }
     }
 
     let compilation_target = payload.compilation_target;
-    add_op_decl(&mut payload.retraction_info, &compilation_target, module_op_dir, op_decl);
+    add_op_decl(
+        &mut payload.retraction_info,
+        &compilation_target,
+        module_op_dir,
+        op_decl,
+    );
 }
 
 pub(super) fn add_op_decl(
@@ -89,10 +95,7 @@ pub(super) fn add_op_decl(
     match op_decl.insert_into_op_dir(op_dir) {
         Some(op_desc) => match &compilation_target {
             CompilationTarget::User => {
-                retraction_info.push_record(RetractionRecord::ReplacedUserOp(
+                retraction_info.push_record(RetractionRecord::ReplacedUserOp(*op_decl, op_desc));
-                    *op_decl,
-                    op_desc,
-                ));
             }
             CompilationTarget::Module(ref module_name) => {
                 retraction_info.push_record(RetractionRecord::ReplacedModuleOp(
@@ -107,10 +110,8 @@ pub(super) fn add_op_decl(
                 retraction_info.push_record(RetractionRecord::AddedUserOp(*op_decl));
             }
             CompilationTarget::Module(ref module_name) => {
-                retraction_info.push_record(RetractionRecord::AddedModuleOp(
+                retraction_info
-                    *module_name,
+                    .push_record(RetractionRecord::AddedModuleOp(*module_name, *op_decl));
-                    *op_decl,
-                ));
             }
         },
     }
@@ -160,7 +161,12 @@ pub(super) fn import_module_exports<'a, LS: LoadState<'a>>(
                 }
             }
             ModuleExport::OpDecl(ref op_decl) => {
-                add_op_decl(&mut payload.retraction_info, compilation_target, op_dir, op_decl);
+                add_op_decl(
+                    &mut payload.retraction_info,
+                    compilation_target,
+                    op_dir,
+                    op_decl,
+                );
             }
         }
     }
@@ -209,12 +215,7 @@ fn import_module_exports_into_module<'a, LS: LoadState<'a>>(
                 }
             }
             ModuleExport::OpDecl(ref op_decl) => {
-                add_op_decl_as_module_export::<LS>(
+                add_op_decl_as_module_export::<LS>(payload, op_dir, wam_op_dir, op_decl);
-                    payload,
-                    op_dir,
-                    wam_op_dir,
-                    op_decl,
-                );
             }
         }
     }
@@ -239,13 +240,18 @@ fn import_qualified_module_exports<'a, LS: LoadState<'a>>(
                 let key = (*name, *arity);
 
                 if let Some(meta_specs) = imported_module.meta_predicates.get(&key) {
-                    wam_prelude.indices.meta_predicates.insert(key.clone(), meta_specs.clone());
+                    wam_prelude
+                        .indices
+                        .meta_predicates
+                        .insert(key.clone(), meta_specs.clone());
                 }
 
                 if let Some(src_code_index) = imported_module.code_dir.get(&key) {
                     let arena = &mut LS::machine_st(payload).arena;
 
-                    let target_code_index = wam_prelude.indices.code_dir
+                    let target_code_index = wam_prelude
+                        .indices
+                        .code_dir
                         .entry(key.clone())
                         .or_insert_with(|| CodeIndex::new(IndexPtr::undefined(), arena))
                         .clone();
@@ -325,12 +331,7 @@ fn import_qualified_module_exports_into_module<'a, LS: LoadState<'a>>(
                 }
             }
             ModuleExport::OpDecl(ref op_decl) => {
-                add_op_decl_as_module_export::<LS>(
+                add_op_decl_as_module_export::<LS>(payload, op_dir, wam_op_dir, op_decl);
-                    payload,
-                    op_dir,
-                    wam_op_dir,
-                    op_decl,
-                );
             }
         }
     }
@@ -378,10 +379,8 @@ impl<'a, LS: LoadState<'a>> Loader<'a, LS> {
         mut clause_target_poses: Vec<Option<usize>>,
         is_dynamic: bool,
     ) {
-        let old_compilation_target = mem::replace(
+        let old_compilation_target =
-            &mut self.payload.compilation_target,
+            mem::replace(&mut self.payload.compilation_target, compilation_target);
-            compilation_target,
-        );
 
         while let Some(target_pos_opt) = clause_target_poses.pop() {
             match target_pos_opt {
@@ -482,7 +481,8 @@ impl<'a, LS: LoadState<'a>> Loader<'a, LS> {
 
             let old_index_ptr = code_index.replace(IndexPtr::undefined());
 
-            self.payload.retraction_info
+            self.payload
+                .retraction_info
                 .push_record(RetractionRecord::ReplacedModulePredicate(
                     module_name,
                     *key,
@@ -491,7 +491,8 @@ impl<'a, LS: LoadState<'a>> Loader<'a, LS> {
         }
 
         for (key, skeleton) in removed_module.extensible_predicates.drain(..) {
-            self.payload.retraction_info
+            self.payload
+                .retraction_info
                 .push_record(RetractionRecord::RemovedSkeleton(
                     CompilationTarget::Module(module_name),
                     key,
@@ -499,7 +500,10 @@ impl<'a, LS: LoadState<'a>> Loader<'a, LS> {
                 ));
         }
 
-        self.wam_prelude.indices.modules.insert(module_name, removed_module);
+        self.wam_prelude
+            .indices
+            .modules
+            .insert(module_name, removed_module);
     }
 
     pub(super) fn remove_module_exports(&mut self, module_name: Atom) {
@@ -523,15 +527,17 @@ impl<'a, LS: LoadState<'a>> Loader<'a, LS> {
                             (Some(module_code_index), Some(target_code_index))
                                 if module_code_index.get() == target_code_index.get() =>
                             {
-                                let old_index_ptr = target_code_index.replace(IndexPtr::undefined());
+                                let old_index_ptr =
-                                retraction_info.push_record(predicate_retractor(*key, old_index_ptr));
+                                    target_code_index.replace(IndexPtr::undefined());
+                                retraction_info
+                                    .push_record(predicate_retractor(*key, old_index_ptr));
                             }
                             _ => {}
                         }
                     }
                     ModuleExport::OpDecl(op_decl) => {
-                        let op_dir_value_opt =
+                        let op_dir_value_opt = op_dir
-                            op_dir.remove(&(op_decl.name, fixity(op_decl.op_desc.get_spec() as u32)));
+                            .remove(&(op_decl.name, fixity(op_decl.op_desc.get_spec() as u32)));
 
                         if let Some(op_desc) = op_dir_value_opt {
                             retraction_info.push_record(op_retractor(*op_decl, op_desc));
@@ -552,9 +558,7 @@ impl<'a, LS: LoadState<'a>> Loader<'a, LS> {
                     RetractionRecord::ReplacedUserOp,
                 );
             }
-            CompilationTarget::Module(target_module_name)
+            CompilationTarget::Module(target_module_name) if target_module_name != module_name => {
-                if target_module_name != module_name =>
-            {
                 let predicate_retractor = |key, index_ptr| {
                     RetractionRecord::ReplacedModulePredicate(module_name, key, index_ptr)
                 };
@@ -563,7 +567,12 @@ impl<'a, LS: LoadState<'a>> Loader<'a, LS> {
                     RetractionRecord::ReplacedModuleOp(module_name, op_decl, op_desc)
                 };
 
-                if let Some(module) = self.wam_prelude.indices.modules.get_mut(&target_module_name) {
+                if let Some(module) = self
+                    .wam_prelude
+                    .indices
+                    .modules
+                    .get_mut(&target_module_name)
+                {
                     remove_module_exports(
                         &removed_module,
                         &mut module.code_dir,
@@ -579,7 +588,10 @@ impl<'a, LS: LoadState<'a>> Loader<'a, LS> {
             CompilationTarget::Module(_) => {}
         };
 
-        self.wam_prelude.indices.modules.insert(module_name, removed_module);
+        self.wam_prelude
+            .indices
+            .modules
+            .insert(module_name, removed_module);
     }
 
     fn get_or_insert_local_code_index(
@@ -591,10 +603,12 @@ impl<'a, LS: LoadState<'a>> Loader<'a, LS> {
             Some(ref mut module) => module
                 .code_dir
                 .entry(key)
-                .or_insert_with(|| CodeIndex::new(
+                .or_insert_with(|| {
+                    CodeIndex::new(
                         IndexPtr::undefined(),
                         &mut LS::machine_st(&mut self.payload).arena,
-                ))
+                    )
+                })
                 .clone(),
             None => {
                 self.add_dynamically_generated_module(module_name);
@@ -603,10 +617,12 @@ impl<'a, LS: LoadState<'a>> Loader<'a, LS> {
                     Some(ref mut module) => module
                         .code_dir
                         .entry(key)
-                        .or_insert_with(|| CodeIndex::new(
+                        .or_insert_with(|| {
+                            CodeIndex::new(
                                 IndexPtr::undefined(),
                                 &mut LS::machine_st(&mut self.payload).arena,
-                        ))
+                            )
+                        })
                         .clone(),
                     None => {
                         unreachable!()
@@ -771,10 +787,7 @@ impl<'a, LS: LoadState<'a>> Loader<'a, LS> {
             ClauseType::Named(arity, name, _) => {
                 let payload_compilation_target = self.payload.compilation_target;
 
-                let idx = self.get_or_insert_code_index(
+                let idx = self.get_or_insert_code_index((name, arity), payload_compilation_target);
-                    (name, arity),
-                    payload_compilation_target,
-                );
 
                 ClauseType::Named(arity, name, idx)
             }
@@ -802,9 +815,7 @@ impl<'a, LS: LoadState<'a>> Loader<'a, LS> {
     }
 
     pub(super) fn get_meta_specs(&self, name: Atom, arity: usize) -> Option<&Vec<MetaSpec>> {
-        self.wam_prelude
+        self.wam_prelude.indices.get_meta_predicate_spec(
-            .indices
-            .get_meta_predicate_spec(
             name,
             arity,
             &self.payload.compilation_target,
@@ -829,19 +840,18 @@ impl<'a, LS: LoadState<'a>> Loader<'a, LS> {
                     .insert(key, meta_specs)
                 {
                     Some(old_meta_specs) => {
-                        self.payload.retraction_info
+                        self.payload.retraction_info.push_record(
-                            .push_record(RetractionRecord::ReplacedMetaPredicate(
+                            RetractionRecord::ReplacedMetaPredicate(
                                 module_name,
                                 key.0,
                                 old_meta_specs,
-                            ));
+                            ),
+                        );
                     }
                     None => {
-                        self.payload.retraction_info
+                        self.payload
-                            .push_record(RetractionRecord::AddedMetaPredicate(
+                            .retraction_info
-                                module_name,
+                            .push_record(RetractionRecord::AddedMetaPredicate(module_name, key));
-                                key,
-                            ));
                     }
                 }
             }
@@ -868,17 +878,16 @@ impl<'a, LS: LoadState<'a>> Loader<'a, LS> {
                     None => {
                         self.add_dynamically_generated_module(module_name);
 
-                        if let Some(module) = self.wam_prelude.indices.modules.get_mut(&module_name) {
+                        if let Some(module) = self.wam_prelude.indices.modules.get_mut(&module_name)
+                        {
                             module.meta_predicates.insert(key.clone(), meta_specs);
                         } else {
                             unreachable!()
                         }
 
-                        self.payload.retraction_info
+                        self.payload.retraction_info.push_record(
-                            .push_record(RetractionRecord::AddedMetaPredicate(
+                            RetractionRecord::AddedMetaPredicate(module_name.clone(), key),
-                                module_name.clone(),
+                        );
-                                key,
-                            ));
                     }
                 }
             }
@@ -901,10 +910,14 @@ impl<'a, LS: LoadState<'a>> Loader<'a, LS> {
             &mut module.meta_predicates,
         );
 
-        self.payload.retraction_info
+        self.payload
+            .retraction_info
             .push_record(RetractionRecord::AddedModule(module_name.clone()));
 
-        self.wam_prelude.indices.modules.insert(module_name.clone(), module);
+        self.wam_prelude
+            .indices
+            .modules
+            .insert(module_name.clone(), module);
     }
 
     fn import_builtins_in_module(
@@ -968,9 +981,7 @@ impl<'a, LS: LoadState<'a>> Loader<'a, LS> {
 
                     if is_dynamic {
                         let clause_clause_compilation_target = match compilation_target {
-                            CompilationTarget::User => {
+                            CompilationTarget::User => CompilationTarget::Module(atom!("builtins")),
-                                CompilationTarget::Module(atom!("builtins"))
-                            }
                             module => module.clone(),
                         };
 
@@ -981,7 +992,8 @@ impl<'a, LS: LoadState<'a>> Loader<'a, LS> {
                     }
                 }
 
-                self.payload.retraction_info
+                self.payload
+                    .retraction_info
                     .push_record(RetractionRecord::ReplacedModule(
                         old_module_decl,
                         listing_src.clone(),
@@ -1051,7 +1063,12 @@ impl<'a, LS: LoadState<'a>> Loader<'a, LS> {
                     )?;
                 }
                 CompilationTarget::Module(ref defining_module_name) => {
-                    match self.wam_prelude.indices.modules.get_mut(defining_module_name) {
+                    match self
+                        .wam_prelude
+                        .indices
+                        .modules
+                        .get_mut(defining_module_name)
+                    {
                         Some(ref mut target_module) => {
                             import_module_exports_into_module::<LS>(
                                 &mut self.payload,
@@ -1091,17 +1108,20 @@ impl<'a, LS: LoadState<'a>> Loader<'a, LS> {
             let payload_compilation_target = self.payload.compilation_target;
 
             let result = match &payload_compilation_target {
-                CompilationTarget::User => {
+                CompilationTarget::User => import_qualified_module_exports::<LS>(
-                    import_qualified_module_exports::<LS>(
                     &mut self.payload,
                     &payload_compilation_target,
                     &module,
                     &exports,
                     &mut self.wam_prelude,
-                    )
+                ),
-                }
                 CompilationTarget::Module(ref defining_module_name) => {
-                    match self.wam_prelude.indices.modules.get_mut(defining_module_name) {
+                    match self
+                        .wam_prelude
+                        .indices
+                        .modules
+                        .get_mut(defining_module_name)
+                    {
                         Some(ref mut target_module) => {
                             import_qualified_module_exports_into_module::<LS>(
                                 &mut self.payload,
@@ -1113,9 +1133,7 @@ impl<'a, LS: LoadState<'a>> Loader<'a, LS> {
                                 &mut self.wam_prelude.indices.op_dir,
                             )
                         }
-                        None => {
+                        None => Err(SessionError::ModuleCannotImportSelf(module_name)),
-                            Err(SessionError::ModuleCannotImportSelf(module_name))
-                        }
                     }
                 }
             };
@@ -1123,29 +1141,38 @@ impl<'a, LS: LoadState<'a>> Loader<'a, LS> {
             self.wam_prelude.indices.modules.insert(module_name, module);
             result
         } else {
-            Err(SessionError::ExistenceError(ExistenceError::Module(module_name)))
+            Err(SessionError::ExistenceError(ExistenceError::Module(
+                module_name,
+            )))
         }
     }
 
     pub(crate) fn use_module(&mut self, module_src: ModuleSource) -> Result<(), SessionError> {
         let (stream, listing_src) = match module_src {
             ModuleSource::File(filename) => {
-                let mut path_buf = PathBuf::from(filename.as_str());
+                let mut path_buf = PathBuf::from(&*filename.as_str());
                 path_buf.set_extension("pl");
 
                 let file = File::open(&path_buf)?;
 
                 (
-                    Stream::from_file_as_input(filename, file, &mut LS::machine_st(&mut self.payload).arena),
+                    Stream::from_file_as_input(
+                        filename,
+                        file,
+                        &mut LS::machine_st(&mut self.payload).arena,
+                    ),
                     ListingSource::File(filename, path_buf),
                 )
             }
-            ModuleSource::Library(library) => match LIBRARIES.borrow().get(library.as_str()) {
+            ModuleSource::Library(library) => match LIBRARIES.borrow().get(&*library.as_str()) {
                 Some(code) => {
                     if let Some(ref module) = self.wam_prelude.indices.modules.get(&library) {
                         if let ListingSource::DynamicallyGenerated = &module.listing_src {
                             (
-                                Stream::from_static_string(*code, &mut LS::machine_st(&mut self.payload).arena),
+                                Stream::from_static_string(
+                                    *code,
+                                    &mut LS::machine_st(&mut self.payload).arena,
+                                ),
                                 ListingSource::User,
                             )
                         } else {
@@ -1153,7 +1180,10 @@ impl<'a, LS: LoadState<'a>> Loader<'a, LS> {
                         }
                     } else {
                         (
-                            Stream::from_static_string(*code, &mut LS::machine_st(&mut self.payload).arena),
+                            Stream::from_static_string(
+                                *code,
+                                &mut LS::machine_st(&mut self.payload).arena,
+                            ),
                             ListingSource::User,
                         )
                     }
@@ -1172,9 +1202,10 @@ impl<'a, LS: LoadState<'a>> Loader<'a, LS> {
             );
 
             let subloader: Loader<'_, BootstrappingLoadState> = Loader {
-                payload: BootstrappingLoadState(
+                payload: BootstrappingLoadState(LoadStatePayload::new(
-                    LoadStatePayload::new(self.wam_prelude.code.len(), term_stream)
+                    self.wam_prelude.code.len(),
-                ),
+                    term_stream,
+                )),
                 wam_prelude: MachinePreludeView {
                     indices: self.wam_prelude.indices,
                     code: self.wam_prelude.code,
@@ -1201,22 +1232,29 @@ impl<'a, LS: LoadState<'a>> Loader<'a, LS> {
     ) -> Result<(), SessionError> {
         let (stream, listing_src) = match module_src {
             ModuleSource::File(filename) => {
-                let mut path_buf = PathBuf::from(filename.as_str());
+                let mut path_buf = PathBuf::from(&*filename.as_str());
                 path_buf.set_extension("pl");
                 let file = File::open(&path_buf)?;
 
                 (
-                    Stream::from_file_as_input(filename, file, &mut LS::machine_st(&mut self.payload).arena),
+                    Stream::from_file_as_input(
+                        filename,
+                        file,
+                        &mut LS::machine_st(&mut self.payload).arena,
+                    ),
                     ListingSource::File(filename, path_buf),
                 )
             }
-            ModuleSource::Library(library) => match LIBRARIES.borrow().get(library.as_str()) {
+            ModuleSource::Library(library) => match LIBRARIES.borrow().get(&*library.as_str()) {
                 Some(code) => {
                     if self.wam_prelude.indices.modules.contains_key(&library) {
                         return self.import_qualified_module(library, exports);
                     } else {
                         (
-                            Stream::from_static_string(*code, &mut LS::machine_st(&mut self.payload).arena),
+                            Stream::from_static_string(
+                                *code,
+                                &mut LS::machine_st(&mut self.payload).arena,
+                            ),
                             ListingSource::User,
                         )
                     }
@@ -1235,9 +1273,10 @@ impl<'a, LS: LoadState<'a>> Loader<'a, LS> {
             );
 
             let subloader: Loader<'_, BootstrappingLoadState> = Loader {
-                payload: BootstrappingLoadState(
+                payload: BootstrappingLoadState(LoadStatePayload::new(
-                    LoadStatePayload::new(self.wam_prelude.code.len(), term_stream),
+                    self.wam_prelude.code.len(),
-                ),
+                    term_stream,
+                )),
                 wam_prelude: MachinePreludeView {
                     indices: self.wam_prelude.indices,
                     code: self.wam_prelude.code,

src/machine/loader.rs

@@ -230,9 +230,7 @@ macro_rules! predicate_queue {
 
 pub type LiveLoadState = LoadStatePayload<LiveTermStream>;
 
-pub struct BootstrappingLoadState<'a>(
+pub struct BootstrappingLoadState<'a>(pub LoadStatePayload<BootstrappingTermStream<'a>>);
-    pub LoadStatePayload<BootstrappingTermStream<'a>>
-);
 
 impl<'a> Deref for BootstrappingLoadState<'a> {
     type Target = LoadStatePayload<BootstrappingTermStream<'a>>;
@@ -255,7 +253,10 @@ pub trait LoadState<'a>: Sized {
     type TS: TermStream;
     type LoaderFieldType: DerefMut<Target = LoadStatePayload<Self::TS>>;
 
-    fn new(machine_st: &'a mut MachineState, payload: LoadStatePayload<Self::TS>) -> Self::LoaderFieldType;
+    fn new(
+        machine_st: &'a mut MachineState,
+        payload: LoadStatePayload<Self::TS>,
+    ) -> Self::LoaderFieldType;
     fn evacuate(loader: Loader<'a, Self>) -> Result<Self::Evacuable, SessionError>;
     fn should_drop_load_state(loader: &Loader<'a, Self>) -> bool;
     fn reset_machine(loader: &mut Loader<'a, Self>);
@@ -293,14 +294,23 @@ impl<'a> LoadState<'a> for LiveLoadAndMachineState<'a> {
     type Evacuable = TypedArenaPtr<LiveLoadState>;
 
     #[inline(always)]
-    fn new(machine_st: &'a mut MachineState, payload: LoadStatePayload<Self::TS>) -> Self::LoaderFieldType {
+    fn new(
+        machine_st: &'a mut MachineState,
+        payload: LoadStatePayload<Self::TS>,
+    ) -> Self::LoaderFieldType {
         let load_state = arena_alloc!(payload, &mut machine_st.arena);
-        LiveLoadAndMachineState { load_state, machine_st }
+        LiveLoadAndMachineState {
+            load_state,
+            machine_st,
+        }
     }
 
     #[inline(always)]
     fn evacuate(mut loader: Loader<'a, Self>) -> Result<Self::Evacuable, SessionError> {
-        loader.payload.load_state.set_tag(ArenaHeaderTag::InactiveLoadState);
+        loader
+            .payload
+            .load_state
+            .set_tag(ArenaHeaderTag::InactiveLoadState);
         Ok(loader.payload.load_state)
     }
 
@@ -332,7 +342,11 @@ impl<'a> LoadState<'a> for LiveLoadAndMachineState<'a> {
         }
 
         if let Some(builtins) = loader.wam_prelude.indices.modules.get(&atom!("builtins")) {
-            if builtins.module_decl.exports.contains(&ModuleExport::PredicateKey(key)) {
+            if builtins
+                .module_decl
+                .exports
+                .contains(&ModuleExport::PredicateKey(key))
+            {
                 return Err(SessionError::CannotOverwriteBuiltIn(key));
             }
         }
@@ -358,10 +372,7 @@ impl<'a> LoadState<'a> for BootstrappingLoadState<'a> {
 
         let repo_len = loader.wam_prelude.code.len();
 
-        loader
+        loader.payload.retraction_info.reset(repo_len);
-            .payload
-            .retraction_info
-            .reset(repo_len);
 
         loader.remove_module_op_exports();
 
@@ -419,8 +430,14 @@ impl<'a> LoadState<'a> for InlineLoadState<'a> {
     type Evacuable = ();
 
     #[inline(always)]
-    fn new(machine_st: &'a mut MachineState, payload: LoadStatePayload<Self::TS>) -> Self::LoaderFieldType {
+    fn new(
-	InlineLoadState { machine_st, payload }
+        machine_st: &'a mut MachineState,
+        payload: LoadStatePayload<Self::TS>,
+    ) -> Self::LoaderFieldType {
+        InlineLoadState {
+            machine_st,
+            payload,
+        }
     }
 
     fn evacuate(_loader: Loader<'a, Self>) -> Result<Self::Evacuable, SessionError> {
@@ -433,8 +450,7 @@ impl<'a> LoadState<'a> for InlineLoadState<'a> {
     }
 
     #[inline(always)]
-    fn reset_machine(_loader: &mut Loader<'a, Self>) {
+    fn reset_machine(_loader: &mut Loader<'a, Self>) {}
-    }
 
     #[inline(always)]
     fn machine_st(load_state: &mut Self::LoaderFieldType) -> &mut MachineState {
@@ -548,7 +564,12 @@ impl<'a, LS: LoadState<'a>> Loader<'a, LS> {
                         atom!("user") => {
                             self.wam_prelude.indices.meta_predicates.remove(&key);
                         }
-                        _ => match self.wam_prelude.indices.modules.get_mut(&target_module_name) {
+                        _ => match self
+                            .wam_prelude
+                            .indices
+                            .modules
+                            .get_mut(&target_module_name)
+                        {
                             Some(ref mut module) => {
                                 module.meta_predicates.remove(&key);
                             }
@@ -566,7 +587,12 @@ impl<'a, LS: LoadState<'a>> Loader<'a, LS> {
                                 .meta_predicates
                                 .insert((name, meta_specs.len()), meta_specs);
                         }
-                        _ => match self.wam_prelude.indices.modules.get_mut(&target_module_name) {
+                        _ => match self
+                            .wam_prelude
+                            .indices
+                            .modules
+                            .get_mut(&target_module_name)
+                        {
                             Some(ref mut module) => {
                                 module
                                     .meta_predicates
@@ -773,9 +799,9 @@ impl<'a, LS: LoadState<'a>> Loader<'a, LS> {
                 }
                 RetractionRecord::ReplacedChoiceOffset(instr_loc, offset) => {
                     match self.wam_prelude.code[instr_loc] {
-                        Instruction::TryMeElse(ref mut o) |
+                        Instruction::TryMeElse(ref mut o)
-                        Instruction::RetryMeElse(ref mut o) |
+                        | Instruction::RetryMeElse(ref mut o)
-                        Instruction::DefaultRetryMeElse(ref mut o) => {
+                        | Instruction::DefaultRetryMeElse(ref mut o) => {
                             *o = offset;
                         }
                         _ => {
@@ -792,7 +818,8 @@ impl<'a, LS: LoadState<'a>> Loader<'a, LS> {
                 }
                 RetractionRecord::ReplacedSwitchOnTermVarIndex(index_loc, old_v) => {
                     match self.wam_prelude.code[index_loc] {
-                        Instruction::IndexingCode(ref mut indexing_code) => match &mut indexing_code[0] {
+                        Instruction::IndexingCode(ref mut indexing_code) => {
+                            match &mut indexing_code[0] {
                                 IndexingLine::Indexing(IndexingInstruction::SwitchOnTerm(
                                     _,
                                     ref mut v,
@@ -801,7 +828,8 @@ impl<'a, LS: LoadState<'a>> Loader<'a, LS> {
                                     *v = old_v;
                                 }
                                 _ => {}
-                        },
+                            }
+                        }
                         _ => {}
                     }
                 }
@@ -941,7 +969,9 @@ impl<'a, LS: LoadState<'a>> Loader<'a, LS> {
                         .get_predicate_skeleton_mut(&compilation_target, &key)
                     {
                         Some(skeleton) => {
-                            if let Some(removed_clauses) = &mut skeleton.core.retracted_dynamic_clauses {
+                            if let Some(removed_clauses) =
+                                &mut skeleton.core.retracted_dynamic_clauses
+                            {
                                 let clause_index_info = removed_clauses.pop().unwrap();
 
                                 skeleton
@@ -1001,10 +1031,15 @@ impl<'a, LS: LoadState<'a>> Loader<'a, LS> {
                 RetractionRecord::RemovedSkeleton(compilation_target, key, skeleton) => {
                     match compilation_target {
                         CompilationTarget::User => {
-                            self.wam_prelude.indices.extensible_predicates.insert(key, skeleton);
+                            self.wam_prelude
+                                .indices
+                                .extensible_predicates
+                                .insert(key, skeleton);
                         }
                         CompilationTarget::Module(module_name) => {
-                            if let Some(module) = self.wam_prelude.indices.modules.get_mut(&module_name) {
+                            if let Some(module) =
+                                self.wam_prelude.indices.modules.get_mut(&module_name)
+                            {
                                 module.extensible_predicates.insert(key, skeleton);
                             }
                         }
@@ -1012,16 +1047,8 @@ impl<'a, LS: LoadState<'a>> Loader<'a, LS> {
                 }
                 RetractionRecord::ReplacedDynamicElseOffset(instr_loc, next) => {
                     match self.wam_prelude.code[instr_loc] {
-                        Instruction::DynamicElse(
+                        Instruction::DynamicElse(_, _, NextOrFail::Next(ref mut o))
-                            _,
+                        | Instruction::DynamicInternalElse(_, _, NextOrFail::Next(ref mut o)) => {
-                            _,
-                            NextOrFail::Next(ref mut o),
-                        )
-                        | Instruction::DynamicInternalElse(
-                            _,
-                            _,
-                            NextOrFail::Next(ref mut o),
-                        ) => {
                             *o = next;
                         }
                         _ => {}
@@ -1029,16 +1056,8 @@ impl<'a, LS: LoadState<'a>> Loader<'a, LS> {
                 }
                 RetractionRecord::AppendedNextOrFail(instr_loc, fail) => {
                     match self.wam_prelude.code[instr_loc] {
-                        Instruction::DynamicElse(
+                        Instruction::DynamicElse(_, _, ref mut next_or_fail)
-                            _,
+                        | Instruction::DynamicInternalElse(_, _, ref mut next_or_fail) => {
-                            _,
-                            ref mut next_or_fail,
-                        )
-                        | Instruction::DynamicInternalElse(
-                            _,
-                            _,
-                            ref mut next_or_fail,
-                        ) => {
                             *next_or_fail = fail;
                         }
                         _ => {}
@@ -1057,15 +1076,14 @@ impl<'a, LS: LoadState<'a>> Loader<'a, LS> {
 
         let export_list = machine_st.read_term_from_heap(cell)?;
         let atom_tbl = &mut LS::machine_st(&mut self.payload).atom_tbl;
-        let export_list = setup_module_export_list(export_list, atom_tbl)?;
+        let export_list = setup_module_export_list(export_list, &atom_tbl)?;
 
         Ok(export_list.into_iter().collect())
     }
 
     fn add_clause_clause(&mut self, term: Term) -> Result<(), CompilationError> {
         match term {
-            Term::Clause(_, atom!(":-"), mut terms) if terms.len() == 2 =>
+            Term::Clause(_, atom!(":-"), mut terms) if terms.len() == 2 => {
-            {
                 let body = terms.pop().unwrap();
                 let head = terms.pop().unwrap();
 
@@ -1096,20 +1114,14 @@ impl<'a, LS: LoadState<'a>> Loader<'a, LS> {
 
         match &compilation_target {
             CompilationTarget::User => {
-                match self
+                match self.wam_prelude.indices.extensible_predicates.get_mut(&key) {
-                    .wam_prelude
-                    .indices
-                    .extensible_predicates
-                    .get_mut(&key)
-                {
                     Some(skeleton) => {
                         if !*flag_accessor(&mut skeleton.core) {
                             *flag_accessor(&mut skeleton.core) = true;
 
-                            self.payload.retraction_info.push_record(retraction_fn(
+                            self.payload
-                                compilation_target,
+                                .retraction_info
-                                key,
+                                .push_record(retraction_fn(compilation_target, key));
-                            ));
                         }
                     }
                     None => {
@@ -1117,11 +1129,7 @@ impl<'a, LS: LoadState<'a>> Loader<'a, LS> {
                             let mut skeleton = PredicateSkeleton::new();
                             *flag_accessor(&mut skeleton.core) = true;
 
-                            self.add_extensible_predicate(
+                            self.add_extensible_predicate(key, skeleton, CompilationTarget::User);
-                                key,
-                                skeleton,
-                                CompilationTarget::User,
-                            );
                         } else {
                             throw_permission_error = true;
                         }
@@ -1135,10 +1143,9 @@ impl<'a, LS: LoadState<'a>> Loader<'a, LS> {
                             if !*flag_accessor(&mut skeleton.core) {
                                 *flag_accessor(&mut skeleton.core) = true;
 
-                                self.payload.retraction_info.push_record(retraction_fn(
+                                self.payload
-                                    compilation_target,
+                                    .retraction_info
-                                    key,
+                                    .push_record(retraction_fn(compilation_target, key));
-                                ));
                             }
                         }
                         None => {
@@ -1146,11 +1153,7 @@ impl<'a, LS: LoadState<'a>> Loader<'a, LS> {
                                 let mut skeleton = PredicateSkeleton::new();
                                 *flag_accessor(&mut skeleton.core) = true;
 
-                                self.add_extensible_predicate(
+                                self.add_extensible_predicate(key, skeleton, compilation_target);
-                                    key,
-                                    skeleton,
-                                    compilation_target,
-                                );
                             } else {
                                 throw_permission_error = true;
                             }
@@ -1162,11 +1165,7 @@ impl<'a, LS: LoadState<'a>> Loader<'a, LS> {
                         let mut skeleton = PredicateSkeleton::new();
                         *flag_accessor(&mut skeleton.core) = true;
 
-                        self.add_extensible_predicate(
+                        self.add_extensible_predicate(key, skeleton, compilation_target);
-                            key,
-                            skeleton,
-                            compilation_target,
-                        );
                     }
                 }
             }
@@ -1178,10 +1177,7 @@ impl<'a, LS: LoadState<'a>> Loader<'a, LS> {
 
             match payload_compilation_target {
                 CompilationTarget::User => {
-                    match self
+                    match self.wam_prelude.indices.get_local_predicate_skeleton_mut(
-                        .wam_prelude
-                        .indices
-                        .get_local_predicate_skeleton_mut(
                         payload_compilation_target,
                         compilation_target,
                         listing_src_file_name,
@@ -1196,11 +1192,7 @@ impl<'a, LS: LoadState<'a>> Loader<'a, LS> {
                             let mut skeleton = LocalPredicateSkeleton::new();
                             *flag_accessor(&mut skeleton) = true;
 
-                            self.add_local_extensible_predicate(
+                            self.add_local_extensible_predicate(compilation_target, key, skeleton);
-                                compilation_target,
-                                key,
-                                skeleton,
-                            );
                         }
                     }
                 }
@@ -1232,11 +1224,7 @@ impl<'a, LS: LoadState<'a>> Loader<'a, LS> {
                             let mut skeleton = LocalPredicateSkeleton::new();
                             *flag_accessor(&mut skeleton) = true;
 
-                            self.add_local_extensible_predicate(
+                            self.add_local_extensible_predicate(compilation_target, key, skeleton);
-                                compilation_target,
-                                key,
-                                skeleton,
-                            );
                         }
                     }
                 }
@@ -1336,10 +1324,7 @@ impl<'a, LS: LoadState<'a>> Loader<'a, LS> {
             let is_dynamic = self
                 .wam_prelude
                 .indices
-                .get_predicate_skeleton(
+                .get_predicate_skeleton(&predicates_compilation_target, &(predicate_name, arity))
-                    &predicates_compilation_target,
-                    &(predicate_name, arity),
-                )
                 .map(|skeleton| skeleton.core.is_dynamic)
                 .unwrap_or(false);
 
@@ -1356,10 +1341,7 @@ impl<'a, LS: LoadState<'a>> Loader<'a, LS> {
         let predicates_compilation_target = self.payload.predicates.compilation_target;
         let listing_src_file_name = self.listing_src_file_name();
 
-        let clause_locs = match self
+        let clause_locs = match self.wam_prelude.indices.get_local_predicate_skeleton_mut(
-            .wam_prelude
-            .indices
-            .get_local_predicate_skeleton_mut(
             payload_compilation_target,
             predicates_compilation_target,
             listing_src_file_name,
@@ -1380,11 +1362,7 @@ impl<'a, LS: LoadState<'a>> Loader<'a, LS> {
             ),
         );
 
-        self.retract_local_clauses_impl(
+        self.retract_local_clauses_impl(predicates_compilation_target, *key, &clause_locs);
-            predicates_compilation_target,
-            *key,
-            &clause_locs,
-        );
 
         if is_dynamic {
             let clause_clause_compilation_target = match predicates_compilation_target {
@@ -1399,7 +1377,10 @@ impl<'a, LS: LoadState<'a>> Loader<'a, LS> {
 
 impl<'a> MachinePreludeView<'a> {
     #[inline]
-    pub(super) fn composite_op_dir(&self, compilation_target: &CompilationTarget) -> CompositeOpDir {
+    pub(super) fn composite_op_dir(
+        &self,
+        compilation_target: &CompilationTarget,
+    ) -> CompositeOpDir {
         match compilation_target {
             CompilationTarget::User => CompositeOpDir::new(&self.indices.op_dir, None),
             CompilationTarget::Module(ref module_name) => {
@@ -1417,7 +1398,10 @@ impl<'a> MachinePreludeView<'a> {
 }
 
 impl MachineState {
-    pub(super) fn read_term_from_heap(&mut self, term_addr: HeapCellValue) -> Result<Term, SessionError> {
+    pub(super) fn read_term_from_heap(
+        &mut self,
+        term_addr: HeapCellValue,
+    ) -> Result<Term, SessionError> {
         let mut term_stack = vec![];
         let mut iter = stackful_post_order_iter(&mut self.heap, &mut self.stack, term_addr);
 
@@ -1436,7 +1420,7 @@ impl MachineState {
                             term_stack.push(Term::PartialString(Cell::default(), string, tail));
                         }
                         Ok((string, None)) => {
-                            let atom = self.atom_tbl.build_with(&string);
+                            let atom = AtomTable::build_with(&self.atom_tbl, &string);
                             term_stack.push(Term::CompleteString(Cell::default(), atom));
                         }
                         Err(cons_term) => term_stack.push(cons_term),
@@ -1550,9 +1534,9 @@ impl Machine {
     }
 
     pub(crate) fn load_compiled_library(&mut self) -> CallResult {
-        let library = cell_as_atom!(
+        let library = cell_as_atom!(self
-            self.machine_st.store(self.machine_st.deref(self.machine_st.registers[1]))
+            .machine_st
-        );
+            .store(self.machine_st.deref(self.machine_st.registers[1])));
 
         if let Some(module) = self.indices.modules.get(&library) {
             if let ListingSource::DynamicallyGenerated = module.listing_src {
@@ -1583,9 +1567,9 @@ impl Machine {
     }
 
     pub(crate) fn declare_module(&mut self) -> CallResult {
-        let module_name = cell_as_atom!(
+        let module_name = cell_as_atom!(self
-            self.machine_st.store(self.machine_st.deref(self.machine_st.registers[1]))
+            .machine_st
-        );
+            .store(self.machine_st.deref(self.machine_st.registers[1])));
 
         let mut loader = self.loader_from_heap_evacuable(temp_v!(3));
 
@@ -1652,7 +1636,11 @@ impl Machine {
 
         let arity = self.deref_register(3);
         let arity = match Number::try_from(arity) {
-            Ok(Number::Integer(n)) if &*n >= &Integer::from(0) && &*n <= &Integer::from(MAX_ARITY) => Ok(n.to_usize().unwrap()),
+            Ok(Number::Integer(n))
+                if &*n >= &Integer::from(0) && &*n <= &Integer::from(MAX_ARITY) =>
+            {
+                Ok(n.to_usize().unwrap())
+            }
             Ok(Number::Fixnum(n)) if n.get_num() >= 0 && n.get_num() <= MAX_ARITY as i64 => {
                 Ok(usize::try_from(n.get_num()).unwrap())
             }
@@ -1692,9 +1680,9 @@ impl Machine {
     }
 
     pub(crate) fn add_goal_expansion_clause(&mut self) -> CallResult {
-        let target_module_name = cell_as_atom!(
+        let target_module_name = cell_as_atom!(self
-            self.machine_st.store(self.machine_st.deref(self.machine_st.registers[1]))
+            .machine_st
-        );
+            .store(self.machine_st.deref(self.machine_st.registers[1])));
 
         let mut loader = self.loader_from_heap_evacuable(temp_v!(3));
 
@@ -1714,7 +1702,8 @@ impl Machine {
 
             if let Some(indexing_term) = indexing_arg {
                 if let Some(indexing_name) = indexing_term.name() {
-                    loader.wam_prelude
+                    loader
+                        .wam_prelude
                         .indices
                         .goal_expansion_indices
                         .insert((indexing_name, indexing_term.arity()));
@@ -1789,16 +1778,19 @@ impl Machine {
         &'a mut self,
         r: RegType,
     ) -> Loader<'a, LiveLoadAndMachineState<'a>> {
-        let mut load_state = cell_as_load_state_payload!(
+        let mut load_state = cell_as_load_state_payload!(self
-            self.machine_st.store(self.machine_st.deref(self.machine_st[r]))
+            .machine_st
-        );
+            .store(self.machine_st.deref(self.machine_st[r])));
 
         load_state.set_tag(ArenaHeaderTag::LiveLoadState);
 
         let (wam_prelude, machine_st) = self.prelude_view_and_machine_st();
 
         Loader {
-            payload: LiveLoadAndMachineState { load_state, machine_st },
+            payload: LiveLoadAndMachineState {
+                load_state,
+                machine_st,
+            },
             wam_prelude,
         }
     }
@@ -1806,26 +1798,21 @@ impl Machine {
     #[inline]
     pub(crate) fn push_load_state_payload(&mut self) {
         let payload = arena_alloc!(
-            LoadStatePayload::new(
+            LoadStatePayload::new(self.code.len(), LiveTermStream::new(ListingSource::User),),
-                self.code.len(),
-                LiveTermStream::new(ListingSource::User),
-            ),
             &mut self.machine_st.arena
         );
 
         let var = self.machine_st.deref(self.machine_st.registers[1]);
 
-        self.machine_st.bind(
+        self.machine_st
-            var.as_var().unwrap(),
+            .bind(var.as_var().unwrap(), typed_arena_ptr_as_cell!(payload));
-            typed_arena_ptr_as_cell!(payload),
-        );
     }
 
     #[inline]
     pub(crate) fn pop_load_state_payload(&mut self) {
-        let load_state_payload = self.machine_st.store(
+        let load_state_payload = self
-            self.machine_st.deref(self.machine_st.registers[1])
+            .machine_st
-        );
+            .store(self.machine_st.deref(self.machine_st.registers[1]));
 
         // unlike in loader_from_heap_evacuable,
         // pop_load_state_payload is allowed to fail to find a
@@ -1863,11 +1850,12 @@ impl Machine {
             2,
         )?;
 
-        let path = cell_as_atom!(
+        let path = cell_as_atom!(self
-            self.machine_st.store(self.machine_st.deref(self.machine_st.registers[2]))
+            .machine_st
-        );
+            .store(self.machine_st.deref(self.machine_st.registers[2])));
 
-        self.load_contexts.push(LoadContext::new(path.as_str(), stream));
+        self.load_contexts
+            .push(LoadContext::new(&*path.as_str(), stream));
         Ok(())
     }
 
@@ -1876,9 +1864,7 @@ impl Machine {
         result: Result<TypedArenaPtr<LiveLoadState>, SessionError>,
     ) -> CallResult {
         match result {
-            Ok(_payload) => {
+            Ok(_payload) => Ok(()),
-                Ok(())
-            }
             Err(e) => {
                 let err = self.machine_st.session_error(e);
                 let stub = functor_stub(atom!("load"), 1);
@@ -1889,9 +1875,9 @@ impl Machine {
     }
 
     pub(crate) fn scoped_clause_to_evacuable(&mut self) -> CallResult {
-        let module_name = cell_as_atom!(
+        let module_name = cell_as_atom!(self
-            self.machine_st.store(self.machine_st.deref(self.machine_st.registers[1]))
+            .machine_st
-        );
+            .store(self.machine_st.deref(self.machine_st.registers[1])));
 
         let loader = self.loader_from_heap_evacuable(temp_v!(3));
 
@@ -1931,9 +1917,10 @@ impl Machine {
     pub(crate) fn load_context_source(&mut self) {
         if let Some(load_context) = self.load_contexts.last() {
             let path_str = load_context.path.to_str().unwrap();
-            let path_atom = self.machine_st.atom_tbl.build_with(path_str);
+            let path_atom = AtomTable::build_with(&self.machine_st.atom_tbl, path_str);
 
-            self.machine_st.unify_atom(path_atom, self.machine_st.registers[1]);
+            self.machine_st
+                .unify_atom(path_atom, self.machine_st.registers[1]);
         } else {
             self.machine_st.fail = true;
         }
@@ -1944,9 +1931,11 @@ impl Machine {
             match load_context.path.file_name() {
                 Some(file_name) if load_context.path.is_file() => {
                     let file_name_str = file_name.to_str().unwrap();
-                    let file_name_atom = self.machine_st.atom_tbl.build_with(file_name_str);
+                    let file_name_atom =
+                        AtomTable::build_with(&self.machine_st.atom_tbl, file_name_str);
 
-                    self.machine_st.unify_atom(file_name_atom, self.machine_st.registers[1]);
+                    self.machine_st
+                        .unify_atom(file_name_atom, self.machine_st.registers[1]);
                     return;
                 }
                 _ => {
@@ -1962,9 +1951,11 @@ impl Machine {
         if let Some(load_context) = self.load_contexts.last() {
             if let Some(directory) = load_context.path.parent() {
                 let directory_str = directory.to_str().unwrap();
-                let directory_atom = self.machine_st.atom_tbl.build_with(directory_str);
+                let directory_atom =
+                    AtomTable::build_with(&self.machine_st.atom_tbl, directory_str);
 
-                self.machine_st.unify_atom(directory_atom, self.machine_st.registers[1]);
+                self.machine_st
+                    .unify_atom(directory_atom, self.machine_st.registers[1]);
                 return;
             }
         }
@@ -1999,11 +1990,9 @@ impl Machine {
             _ => CompilationTarget::Module(module_name),
         };
 
-        let stub_gen = || {
+        let stub_gen = || match append_or_prepend {
-            match append_or_prepend {
             AppendOrPrepend::Append => functor_stub(atom!("assertz"), 1),
             AppendOrPrepend::Prepend => functor_stub(atom!("asserta"), 1),
-            }
         };
 
         let head = self.deref_register(2);
@@ -2019,7 +2008,8 @@ impl Machine {
 
             loader.payload.compilation_target = compilation_target;
 
-            let head = LiveLoadAndMachineState::machine_st(&mut loader.payload).read_term_from_heap(head)?;
+            let head = LiveLoadAndMachineState::machine_st(&mut loader.payload)
+                .read_term_from_heap(head)?;
 
             let name = if let Some(name) = head.name() {
                 name
@@ -2033,21 +2023,13 @@ impl Machine {
             let is_dynamic_predicate = loader
                 .wam_prelude
                 .indices
-                  .is_dynamic_predicate(
+                .is_dynamic_predicate(module_name, (name, arity));
-                      module_name,
-                      (name, arity),
-                  );
 
-            let no_such_predicate =
+            let no_such_predicate = if !is_dynamic_predicate && !is_builtin {
-                if !is_dynamic_predicate && !is_builtin {
                 let idx_tag = loader
                     .wam_prelude
                     .indices
-                        .get_predicate_code_index(
+                    .get_predicate_code_index(name, arity, module_name)
-                            name,
-                            arity,
-                            module_name,
-                        )
                     .map(|code_idx| code_idx.get_tag())
                     .unwrap_or(IndexPtrTag::DynamicUndefined);
 
@@ -2098,23 +2080,18 @@ impl Machine {
         match compile_assert() {
             Ok(_) => Ok(()),
             Err(SessionError::CompilationError(
-                CompilationError::InvalidRuleHead |
+                CompilationError::InvalidRuleHead | CompilationError::InadmissibleFact,
-                CompilationError::InadmissibleFact
             )) => {
-                let err = self.machine_st.type_error(
+                let err = self
-                    ValidType::Callable,
+                    .machine_st
-                    self.machine_st.registers[2],
+                    .type_error(ValidType::Callable, self.machine_st.registers[2]);
-                );
 
                 Err(self.machine_st.error_form(err, stub_gen()))
             }
-            Err(SessionError::CompilationError(
+            Err(SessionError::CompilationError(CompilationError::InadmissibleQueryTerm)) => {
-                CompilationError::InadmissibleQueryTerm
+                let err = self
-            )) => {
+                    .machine_st
-                let err = self.machine_st.type_error(
+                    .type_error(ValidType::Callable, self.machine_st.registers[3]);
-                    ValidType::Callable,
-                    self.machine_st.registers[3],
-                );
 
                 Err(self.machine_st.error_form(err, stub_gen()))
             }
@@ -2126,9 +2103,9 @@ impl Machine {
     }
 
     pub(crate) fn abolish_clause(&mut self) -> CallResult {
-        let module_name = cell_as_atom!(
+        let module_name = cell_as_atom!(self
-            self.machine_st.store(self.machine_st.deref(self.machine_st.registers[1]))
+            .machine_st
-        );
+            .store(self.machine_st.deref(self.machine_st.registers[1])));
 
         let key = self
             .machine_st
@@ -2140,8 +2117,8 @@ impl Machine {
         };
 
         let mut abolish_clause = || {
-            let mut loader: Loader<'_, LiveLoadAndMachineState<'_>>
+            let mut loader: Loader<'_, LiveLoadAndMachineState<'_>> =
-                = Loader::new(self, LiveTermStream::new(ListingSource::User));
+                Loader::new(self, LiveTermStream::new(ListingSource::User));
 
             loader.payload.compilation_target = compilation_target;
 
@@ -2161,9 +2138,11 @@ impl Machine {
                         .remove_predicate_skeleton(
                             &clause_clause_compilation_target,
                             &(atom!("$clause"), 2),
-                        ).unwrap();
+                        )
+                        .unwrap();
 
-                    let result = skeleton.core
+                    let result = skeleton
+                        .core
                         .clause_clause_locs
                         .iter()
                         .map(|clause_clause_loc| {
@@ -2173,11 +2152,7 @@ impl Machine {
                         })
                         .collect();
 
-                    loader.add_extensible_predicate(
+                    loader.add_extensible_predicate(key, skeleton, compilation_target);
-                        key,
-                        skeleton,
-                        compilation_target,
-                    );
 
                     loader.add_extensible_predicate(
                         (atom!("$clause"), 2),
@@ -2186,14 +2161,15 @@ impl Machine {
                     );
 
                     result
-                }).unwrap();
+                })
+                .unwrap();
 
-            loader.wam_prelude
+            loader
+                .wam_prelude
                 .indices
                 .remove_predicate_skeleton(&compilation_target, &key);
 
-            let mut code_index = loader
+            let mut code_index = loader.get_or_insert_code_index(key, compilation_target);
-                .get_or_insert_code_index(key, compilation_target);
 
             code_index.set(IndexPtr::undefined());
 
@@ -2231,9 +2207,9 @@ impl Machine {
             _ => unreachable!(),
         };
 
-        let module_name = cell_as_atom!(
+        let module_name = cell_as_atom!(self
-            self.machine_st.store(self.machine_st.deref(self.machine_st.registers[4]))
+            .machine_st
-        );
+            .store(self.machine_st.deref(self.machine_st.registers[4])));
 
         let compilation_target = match module_name {
             atom!("user") => CompilationTarget::User,
@@ -2286,9 +2262,9 @@ impl Machine {
     }
 
     pub(crate) fn is_consistent_with_term_queue(&mut self) -> CallResult {
-        let module_name = cell_as_atom!(
+        let module_name = cell_as_atom!(self
-            self.machine_st.store(self.machine_st.deref(self.machine_st.registers[1]))
+            .machine_st
-        );
+            .store(self.machine_st.deref(self.machine_st.registers[1])));
 
         let key = self
             .machine_st
@@ -2326,9 +2302,9 @@ impl Machine {
     }
 
     pub(crate) fn remove_module_exports(&mut self) -> CallResult {
-        let module_name = cell_as_atom!(
+        let module_name = cell_as_atom!(self
-            self.machine_st.store(self.machine_st.deref(self.machine_st.registers[1]))
+            .machine_st
-        );
+            .store(self.machine_st.deref(self.machine_st.registers[1])));
 
         let mut loader = self.loader_from_heap_evacuable(temp_v!(2));
 
@@ -2354,9 +2330,9 @@ impl Machine {
     }
 
     pub(crate) fn meta_predicate_property(&mut self) {
-        let module_name = cell_as_atom!(
+        let module_name = cell_as_atom!(self
-            self.machine_st.store(self.machine_st.deref(self.machine_st.registers[1]))
+            .machine_st
-        );
+            .store(self.machine_st.deref(self.machine_st.registers[1])));
 
         let (predicate_name, arity) = self
             .machine_st
@@ -2374,9 +2350,12 @@ impl Machine {
             Some(meta_specs) => {
                 let term_loc = self.machine_st.heap.len();
 
-                self.machine_st.heap.push(atom_as_cell!(predicate_name, arity));
+                self.machine_st
-                self.machine_st.heap.extend(
+                    .heap
-                    meta_specs.iter().map(|meta_spec| match meta_spec {
+                    .push(atom_as_cell!(predicate_name, arity));
+                self.machine_st
+                    .heap
+                    .extend(meta_specs.iter().map(|meta_spec| match meta_spec {
                         MetaSpec::Minus => atom_as_cell!(atom!("+")),
                         MetaSpec::Plus => atom_as_cell!(atom!("-")),
                         MetaSpec::Either => atom_as_cell!(atom!("?")),
@@ -2384,15 +2363,20 @@ impl Machine {
                         MetaSpec::RequiresExpansionWithArgument(ref arg_num) => {
                             fixnum_as_cell!(Fixnum::build_with(*arg_num as i64))
                         }
-                    })
+                    }));
-                );
 
                 let heap_loc = self.machine_st.heap.len();
 
-                self.machine_st.heap.push(atom_as_cell!(atom!("meta_predicate"), 1));
+                self.machine_st
+                    .heap
+                    .push(atom_as_cell!(atom!("meta_predicate"), 1));
                 self.machine_st.heap.push(str_loc_as_cell!(term_loc));
 
-                unify!(self.machine_st, str_loc_as_cell!(heap_loc), self.machine_st.registers[4]);
+                unify!(
+                    self.machine_st,
+                    str_loc_as_cell!(heap_loc),
+                    self.machine_st.registers[4]
+                );
             }
             None => {
                 self.machine_st.fail = true;
@@ -2401,9 +2385,9 @@ impl Machine {
     }
 
     pub(crate) fn dynamic_property(&mut self) {
-        let module_name = cell_as_atom!(
+        let module_name = cell_as_atom!(self
-            self.machine_st.store(self.machine_st.deref(self.machine_st.registers[1]))
+            .machine_st
-        );
+            .store(self.machine_st.deref(self.machine_st.registers[1])));
 
         let key = self
             .machine_st
@@ -2428,9 +2412,9 @@ impl Machine {
     }
 
     pub(crate) fn multifile_property(&mut self) {
-        let module_name = cell_as_atom!(
+        let module_name = cell_as_atom!(self
-            self.machine_st.store(self.machine_st.deref(self.machine_st.registers[1]))
+            .machine_st
-        );
+            .store(self.machine_st.deref(self.machine_st.registers[1])));
 
         let key = self
             .machine_st
@@ -2455,9 +2439,9 @@ impl Machine {
     }
 
     pub(crate) fn discontiguous_property(&mut self) {
-        let module_name = cell_as_atom!(
+        let module_name = cell_as_atom!(self
-            self.machine_st.store(self.machine_st.deref(self.machine_st.registers[1]))
+            .machine_st
-        );
+            .store(self.machine_st.deref(self.machine_st.registers[1])));
 
         let key = self
             .machine_st

src/machine/machine_errors.rs

@@ -44,7 +44,8 @@ pub(crate) enum ValidType {
     InCharacter,
     Integer,
     List,
-    #[allow(unused)] Number,
+    #[allow(unused)]
+    Number,
     Pair,
     //    PredicateIndicator,
     //    Variable
@@ -254,9 +255,11 @@ pub(super) type FunctorStub = [HeapCellValue; 3];
 
 #[inline(always)]
 pub(super) fn functor_stub(name: Atom, arity: usize) -> FunctorStub {
-    [atom_as_cell!(atom!("/"), 2),
+    [
+        atom_as_cell!(atom!("/"), 2),
         atom_as_cell!(name),
-     fixnum_as_cell!(Fixnum::build_with(arity as i64))]
+        fixnum_as_cell!(Fixnum::build_with(arity as i64)),
+    ]
 }
 
 impl MachineState {
@@ -444,7 +447,9 @@ impl MachineState {
                 self.permission_error(
                     Permission::Modify,
                     atom!("static_procedure"),
-                    functor_stub(key.0, key.1).into_iter().collect::<MachineStub>(),
+                    functor_stub(key.0, key.1)
+                        .into_iter()
+                        .collect::<MachineStub>(),
                 )
             }
             SessionError::ExistenceError(err) => self.existence_error(err),
@@ -471,7 +476,11 @@ impl MachineState {
             }
             SessionError::NamelessEntry => {
                 let error_atom = atom!("nameless_procedure");
-                self.permission_error(Permission::Create, atom!("static_procedure"), functor!(error_atom))
+                self.permission_error(
+                    Permission::Create,
+                    atom!("static_procedure"),
+                    functor!(error_atom),
+                )
             }
             SessionError::OpIsInfixAndPostFix(op) => {
                 self.permission_error(Permission::Create, atom!("operator"), functor!(op))
@@ -682,10 +691,12 @@ impl CompilationError {
             &CompilationError::ExpectedRel => {
                 functor!(atom!("expected_relation"))
             }
-            &CompilationError::InadmissibleFact => { // TODO: type_error(callable, _).
+            &CompilationError::InadmissibleFact => {
+                // TODO: type_error(callable, _).
                 functor!(atom!("inadmissible_fact"))
             }
-            &CompilationError::InadmissibleQueryTerm => { // TODO: type_error(callable, _).
+            &CompilationError::InadmissibleQueryTerm => {
+                // TODO: type_error(callable, _).
                 functor!(atom!("inadmissible_query_term"))
             }
             &CompilationError::InconsistentEntry => {
@@ -838,7 +849,7 @@ impl MachineState {
         match BrentAlgState::detect_cycles(&self.heap, list) {
             CycleSearchResult::PartialList(..) => {
                 let err = self.instantiation_error();
-                return Err(self.error_form(err, stub_gen()))
+                return Err(self.error_form(err, stub_gen()));
             }
             CycleSearchResult::NotList(..) | CycleSearchResult::Cyclic(_) => {
                 let err = self.type_error(ValidType::List, list);

src/machine/machine_indices.rs

@@ -3,15 +3,15 @@ use crate::parser::ast::*;
 use crate::arena::*;
 use crate::atom_table::*;
 use crate::forms::*;
-use crate::machine::ClauseType;
 use crate::machine::loader::*;
 use crate::machine::machine_state::*;
 use crate::machine::streams::Stream;
+use crate::machine::ClauseType;
 
 use fxhash::FxBuildHasher;
 use indexmap::{IndexMap, IndexSet};
-use modular_bitfield::{BitfieldSpecifier, bitfield};
 use modular_bitfield::specifiers::*;
+use modular_bitfield::{bitfield, BitfieldSpecifier};
 
 use std::cmp::Ordering;
 use std::collections::BTreeSet;
@@ -86,7 +86,8 @@ pub enum IndexPtrTag {
 #[derive(Debug, Clone, Copy, Eq, Hash, Ord, PartialEq, PartialOrd)]
 pub struct IndexPtr {
     pub p: B56,
-    #[allow(unused)] m: bool,
+    #[allow(unused)]
+    m: bool,
     pub tag: IndexPtrTag,
 }
 
@@ -293,7 +294,8 @@ impl IndexStore {
         let (name, arity) = key;
 
         if !ClauseType::is_inbuilt(name, arity) {
-            self.modules.get(&(atom!("builtins")))
+            self.modules
+                .get(&(atom!("builtins")))
                 .map(|module| module.code_dir.contains_key(&(name, arity)))
                 .unwrap_or(false)
         } else {
@@ -444,11 +446,7 @@ impl IndexStore {
         }
     }
 
-    pub(crate) fn is_dynamic_predicate(
+    pub(crate) fn is_dynamic_predicate(&self, module_name: Atom, key: PredicateKey) -> bool {
-        &self,
-        module_name: Atom,
-        key: PredicateKey,
-    ) -> bool {
         match module_name {
             atom!("user") => self
                 .extensible_predicates

src/machine/machine_state.rs

@@ -3,7 +3,6 @@ use crate::atom_table::*;
 use crate::forms::*;
 use crate::heap_iter::*;
 use crate::heap_print::*;
-use crate::machine::Machine;
 use crate::machine::attributed_variables::*;
 use crate::machine::copier::*;
 use crate::machine::heap::*;
@@ -11,6 +10,7 @@ use crate::machine::machine_errors::*;
 use crate::machine::machine_indices::*;
 use crate::machine::stack::*;
 use crate::machine::streams::*;
+use crate::machine::Machine;
 use crate::parser::ast::*;
 use crate::read::TermWriteResult;
 use crate::types::*;
@@ -22,6 +22,7 @@ use indexmap::IndexMap;
 use std::convert::TryFrom;
 use std::fmt;
 use std::ops::{Index, IndexMut};
+use std::sync::Arc;
 
 pub(crate) type Registers = [HeapCellValue; MAX_ARITY + 1];
 
@@ -57,7 +58,7 @@ pub enum OnEOF {
 }
 
 pub struct MachineState {
-    pub atom_tbl: AtomTable,
+    pub atom_tbl: Arc<AtomTable>,
     pub arena: Arena,
     pub(super) pdl: Vec<HeapCellValue>,
     pub(super) s: HeapPtr,
@@ -203,12 +204,12 @@ pub fn pstr_loc_and_offset(heap: &[HeapCellValue], index: usize) -> (usize, Fixn
 fn push_var_eq_functors<'a>(
     heap: &mut Heap,
     iter: impl Iterator<Item = (&'a VarKey, &'a HeapCellValue)>,
-    atom_tbl: &mut AtomTable,
+    atom_tbl: &AtomTable,
 ) -> Vec<HeapCellValue> {
     let mut list_of_var_eqs = vec![];
 
     for (var, binding) in iter {
-        let var_atom = atom_tbl.build_with(&var.to_string());
+        let var_atom = AtomTable::build_with(atom_tbl, &var.to_string());
         let h = heap.len();
 
         heap.push(atom_as_cell!(atom!("="), 2));
@@ -243,9 +244,11 @@ impl Ball {
     pub(super) fn copy_and_align(&self, h: usize) -> Heap {
         let diff = self.boundary as i64 - h as i64;
 
-        self.stub.iter().cloned().map(|heap_value| {
+        self.stub
-            heap_value - diff
+            .iter()
-        }).collect()
+            .cloned()
+            .map(|heap_value| heap_value - diff)
+            .collect()
     }
 }
 
@@ -418,9 +421,7 @@ impl MachineState {
             if self.cwil.count == *limit {
                 self.cwil.inference_limit_exceeded = true;
 
-                return Err(
+                return Err(functor!(atom!("inference_limit_exceeded"), [fixnum(bp)]));
-                    functor!(atom!("inference_limit_exceeded"), [fixnum(bp)])
-                );
             } else {
                 self.cwil.count += 1;
             }
@@ -430,7 +431,10 @@ impl MachineState {
     }
 
     #[allow(dead_code)]
-    pub(super) fn try_char_list(&mut self, addrs: Vec<HeapCellValue>) -> Result<String, MachineError> {
+    pub(super) fn try_char_list(
+        &mut self,
+        addrs: Vec<HeapCellValue>,
+    ) -> Result<String, MachineError> {
         let mut chars = String::new();
 
         for addr in addrs {
@@ -519,14 +523,21 @@ impl MachineState {
 
         let list_of_var_eqs = push_var_eq_functors(
             &mut self.heap,
-            var_list.iter().filter_map(|(var_name, var,_)| if var_name.is_anon() { None } else { Some((var_name,var)) }),
+            var_list.iter().filter_map(|(var_name, var, _)| {
-            &mut self.atom_tbl,
+                if var_name.is_anon() {
+                    None
+                } else {
+                    Some((var_name, var))
+                }
+            }),
+            &self.atom_tbl,
         );
 
         let singleton_addr = self.registers[3];
-        let singletons_offset = heap_loc_as_cell!(
+        let singletons_offset = heap_loc_as_cell!(iter_to_heap_list(
-            iter_to_heap_list(&mut self.heap, singleton_var_list.into_iter())
+            &mut self.heap,
-        );
+            singleton_var_list.into_iter()
+        ));
 
         unify_fn!(*self, singletons_offset, singleton_addr);
 
@@ -535,9 +546,10 @@ impl MachineState {
         }
 
         let vars_addr = self.registers[4];
-        let vars_offset = heap_loc_as_cell!(
+        let vars_offset = heap_loc_as_cell!(iter_to_heap_list(
-            iter_to_heap_list(&mut self.heap, var_list.into_iter().map(|(_,cell,_)| cell))
+            &mut self.heap,
-        );
+            var_list.into_iter().map(|(_, cell, _)| cell)
+        ));
 
         unify_fn!(*self, vars_offset, vars_addr);
 
@@ -546,9 +558,10 @@ impl MachineState {
         }
 
         let var_names_addr = self.registers[5];
-        let var_names_offset = heap_loc_as_cell!(
+        let var_names_offset = heap_loc_as_cell!(iter_to_heap_list(
-            iter_to_heap_list(&mut self.heap, list_of_var_eqs.into_iter())
+            &mut self.heap,
-        );
+            list_of_var_eqs.into_iter()
+        ));
 
         Ok(unify_fn!(*self, var_names_offset, var_names_addr))
     }
@@ -589,7 +602,10 @@ impl MachineState {
 
         let singleton_var_list = push_var_eq_functors(
             &mut self.heap,
-            term_write_result.var_dict.iter().filter(|(var_name, binding)| {
+            term_write_result
+                .var_dict
+                .iter()
+                .filter(|(var_name, binding)| {
                     if var_name.is_anon() {
                         return false;
                     }
@@ -600,7 +616,7 @@ impl MachineState {
                         false
                     }
                 }),
-            &mut self.atom_tbl,
+            &self.atom_tbl,
         );
 
         for var in term_write_result.var_dict.values_mut() {
@@ -620,13 +636,11 @@ impl MachineState {
         self.write_read_term_options(var_list, singleton_var_list)
     }
 
-    pub fn read_term_from_user_input_eof_handler(&mut self, stream: Stream) -> Result<OnEOF, MachineStub> {
+    pub fn read_term_from_user_input_eof_handler(
-        self.eof_action(
+        &mut self,
-            self.registers[2],
+        stream: Stream,
-            stream,
+    ) -> Result<OnEOF, MachineStub> {
-            atom!("read_term"),
+        self.eof_action(self.registers[2], stream, atom!("read_term"), 3)?;
-            3,
-        )?;
 
         if stream.options().eof_action() == EOFAction::Reset {
             if self.fail == false {
@@ -639,13 +653,15 @@ impl MachineState {
 
     // Safety: the atom_tbl lives for the lifetime of the machine, as does the helper, so the ptr
     // will always be valid.
-    pub fn read_term_from_user_input(&mut self, stream: Stream, indices: &mut IndexStore) -> CallResult {
+    pub fn read_term_from_user_input(
-        let atoms_ptr = (&self.atom_tbl.table) as *const indexmap::IndexSet<Atom>;
+        &mut self,
-
+        stream: Stream,
+        indices: &mut IndexStore,
+    ) -> CallResult {
         if let Stream::Readline(ptr) = stream {
             unsafe {
                 let readline = ptr.as_ptr().as_mut().unwrap();
-                readline.set_atoms_for_completion(atoms_ptr);
+                readline.set_atoms_for_completion(&self.atom_tbl);
                 return self.read_term(
                     stream,
                     indices,
@@ -663,12 +679,7 @@ impl MachineState {
             stream.set_past_end_of_stream(true);
             return Ok(OnEOF::Return);
         } else if stream.past_end_of_stream() {
-            self.eof_action(
+            self.eof_action(self.registers[2], stream, atom!("read_term"), 3)?;
-                self.registers[2],
-                stream,
-                atom!("read_term"),
-                3,
-            )?;
 
             if stream.options().eof_action() == EOFAction::Reset {
                 if self.fail == false {
@@ -709,7 +720,9 @@ impl MachineState {
                     match &err {
                         CompilationError::ParserError(e) if e.is_unexpected_eof() => {
                             match eof_handler(self, stream)? {
-                                OnEOF::Return => return self.write_read_term_options(vec![], vec![]),
+                                OnEOF::Return => {
+                                    return self.write_read_term_options(vec![], vec![])
+                                }
                                 OnEOF::Continue => continue,
                             }
                         }
@@ -762,14 +775,14 @@ impl MachineState {
                                     }
                                     (HeapCellValueTag::Atom, (name, _arity)) => {
                                         debug_assert_eq!(_arity, 0);
-                                        var_names.insert(var, VarPtr::from(name.as_str()));
+                                        var_names.insert(var, VarPtr::from(&*name.as_str()));
                                     }
                                     (HeapCellValueTag::Str, s) => {
                                         let (name, arity) = cell_as_atom_cell!(self.heap[s])
                                             .get_name_and_arity();
 
                                         debug_assert_eq!(arity, 0);
-                                        var_names.insert(var, VarPtr::from(name.as_str()));
+                                        var_names.insert(var, VarPtr::from(&*name.as_str()));
                                     }
                                     _ => {
                                         unreachable!();
@@ -850,7 +863,7 @@ impl MachineState {
 
                 let mut printer = HCPrinter::new(
                     &mut self.heap,
-                    &mut self.atom_tbl,
+                    Arc::clone(&self.atom_tbl),
                     &mut self.stack,
                     op_dir,
                     PrinterOutputter::new(),
@@ -896,7 +909,11 @@ impl MachineState {
         Ok(Some(printer))
     }
 
-    pub(super) fn read_predicate_key(&self, name: HeapCellValue, arity: HeapCellValue) -> (Atom, usize) {
+    pub(super) fn read_predicate_key(
+        &self,
+        name: HeapCellValue,
+        arity: HeapCellValue,
+    ) -> (Atom, usize) {
         let name = cell_as_atom!(self.store(self.deref(name)));
         let arity = cell_as_fixnum!(self.store(self.deref(arity)));
 

src/machine/machine_state_impl.rs

@@ -1,6 +1,5 @@
 use crate::arena::*;
 use crate::atom_table::*;
-use crate::types::*;
 use crate::forms::*;
 use crate::heap_iter::*;
 use crate::machine::attributed_variables::*;
@@ -14,6 +13,7 @@ use crate::machine::stack::*;
 use crate::machine::unify::*;
 use crate::parser::ast::*;
 use crate::parser::dashu::{Integer, Rational};
+use crate::types::*;
 
 use indexmap::IndexSet;
 
@@ -59,8 +59,8 @@ impl MachineState {
             dynamic_mode: FirstOrNext::First,
             unify_fn: MachineState::unify,
             bind_fn: MachineState::bind,
-            run_cleaners_fn: |_| { false },
+            run_cleaners_fn: |_| false,
-            increment_call_count_fn: |_| { Ok(()) },
+            increment_call_count_fn: |_| Ok(()),
         }
     }
 
@@ -160,9 +160,8 @@ impl MachineState {
                     key_atom.index as u64,
                 ));
 
-                self.trail.push(TrailEntry::from_bytes(
+                self.trail
-                    value_cell.into_bytes(),
+                    .push(TrailEntry::from_bytes(value_cell.into_bytes()));
-                ));
 
                 self.tr += 2;
             }
@@ -248,9 +247,7 @@ impl MachineState {
         r: Ref,
         value: HeapCellValue,
     ) {
-        let mut unifier = CompositeUnifierForOccursCheckWithError::from(
+        let mut unifier = CompositeUnifierForOccursCheckWithError::from(DefaultUnifier::from(self));
-            DefaultUnifier::from(self),
-        );
 
         unifier.bind(r, value);
     }
@@ -316,9 +313,7 @@ impl MachineState {
     }
 
     pub(super) fn unify_with_occurs_check_with_error(&mut self) {
-        let mut unifier = CompositeUnifierForOccursCheckWithError::from(
+        let mut unifier = CompositeUnifierForOccursCheckWithError::from(DefaultUnifier::from(self));
-            DefaultUnifier::from(self),
-        );
 
         unifier.unify_internal();
     }
@@ -380,8 +375,7 @@ impl MachineState {
                     }
                 )
             }
-            &mut HeapPtr::PStrChar(h, ref mut n) |
+            &mut HeapPtr::PStrChar(h, ref mut n) | &mut HeapPtr::PStrLocation(h, ref mut n) => {
-            &mut HeapPtr::PStrLocation(h, ref mut n) => {
                 read_heap_cell!(self.heap[h],
                     (HeapCellValueTag::PStr, pstr_atom) => {
                         let pstr = PartialString::from(pstr_atom);
@@ -509,7 +503,7 @@ impl MachineState {
                                     } else {
                                         self.pdl.clear();
                                         return Some(
-                                            n1.chars().next().cmp(&Some(c2))
+                                            n1.as_str().chars().next().cmp(&Some(c2))
                                               .then(Ordering::Greater)
                                         );
                                     }
@@ -539,7 +533,7 @@ impl MachineState {
                                     } else {
                                         self.pdl.clear();
                                         return Some(
-                                            Some(c1).cmp(&n2.chars().next())
+                                            Some(c1).cmp(&n2.as_str().chars().next())
                                                     .then(Ordering::Less)
                                         );
                                     }
@@ -562,7 +556,7 @@ impl MachineState {
                                     } else {
                                         self.pdl.clear();
                                         return Some(
-                                            Some(c1).cmp(&n2.chars().next())
+                                            Some(c1).cmp(&n2.as_str().chars().next())
                                                     .then(Ordering::Less)
                                         );
                                     }
@@ -592,7 +586,7 @@ impl MachineState {
                                     } else {
                                         self.pdl.clear();
                                         return Some(
-                                            n1.chars().next().cmp(&Some(c2))
+                                            n1.as_str().chars().next().cmp(&Some(c2))
                                               .then(Ordering::Greater)
                                         );
                                     }
@@ -902,8 +896,12 @@ impl MachineState {
 
         let s = string.as_str();
 
-        match heap_pstr_iter.compare_pstr_to_string(s) {
+        match heap_pstr_iter.compare_pstr_to_string(&*s) {
-            Some(PStrPrefixCmpResult { focus, offset, prefix_len }) if prefix_len == s.len() => {
+            Some(PStrPrefixCmpResult {
+                focus,
+                offset,
+                prefix_len,
+            }) if prefix_len == s.len() => {
                 let focus_addr = self.heap[focus];
 
                 read_heap_cell!(focus_addr,
@@ -950,7 +948,10 @@ impl MachineState {
 
                 return;
             }
-            Some(PStrPrefixCmpResult { prefix_len: inner_prefix_len, .. }) => {
+            Some(PStrPrefixCmpResult {
+                prefix_len: inner_prefix_len,
+                ..
+            }) => {
                 prefix_len = inner_prefix_len;
             }
             None => {
@@ -1002,9 +1003,9 @@ impl MachineState {
             self.s_offset = 0;
             self.mode = MachineMode::Read;
 
-            put_partial_string(&mut self.heap, pstr, &mut self.atom_tbl)
+            put_partial_string(&mut self.heap, pstr, &self.atom_tbl)
         } else {
-            put_complete_string(&mut self.heap, pstr, &mut self.atom_tbl)
+            put_complete_string(&mut self.heap, pstr, &self.atom_tbl)
         }
     }
 
@@ -1096,7 +1097,7 @@ impl MachineState {
                 (name, 0, 0)
             }
             (HeapCellValueTag::Char, c) => {
-                (self.atom_tbl.build_with(&c.to_string()), 0, 0)
+                (AtomTable::build_with(&self.atom_tbl, &c.to_string()), 0, 0)
             }
             (HeapCellValueTag::Var | HeapCellValueTag::AttrVar | HeapCellValueTag::StackVar) => {
                 let stub = functor_stub(atom!("call"), arity + 1);
@@ -1435,7 +1436,7 @@ impl MachineState {
                         }
                     }
                     (HeapCellValueTag::Char, c) => {
-                        let c = self.atom_tbl.build_with(&c.to_string());
+                        let c = AtomTable::build_with(&self.atom_tbl, &c.to_string());
 
                         self.try_functor_fabricate_struct(
                             c,
@@ -1571,8 +1572,7 @@ impl MachineState {
 
         while let Some(iteratee) = heap_pstr_iter.next() {
             match iteratee {
-                PStrIteratee::Char(_, c) =>
+                PStrIteratee::Char(_, c) => chars.push(char_as_cell!(c)),
-                    chars.push(char_as_cell!(c)),
                 PStrIteratee::PStrSegment(_, pstr_atom, n) => {
                     let pstr = PartialString::from(pstr_atom);
                     chars.extend(pstr.as_str_from(n).chars().map(|c| char_as_cell!(c)));
@@ -1634,10 +1634,7 @@ impl MachineState {
             let mut value = unmark_cell_bits!(value);
 
             if value.is_var() {
-                value = heap_bound_store(
+                value = heap_bound_store(iter.heap, heap_bound_deref(iter.heap, value));
-                    iter.heap,
-                    heap_bound_deref(iter.heap, value),
-                );
 
                 if value.is_var() {
                     return true;

src/machine/mock_wam.rs

@@ -2,15 +2,17 @@ pub use crate::arena::*;
 pub use crate::atom_table::*;
 use crate::heap_print::*;
 pub use crate::machine::heap::*;
-pub use crate::machine::*;
 pub use crate::machine::machine_state::*;
 pub use crate::machine::stack::*;
 pub use crate::machine::streams::*;
+pub use crate::machine::*;
 pub use crate::macros::*;
 pub use crate::parser::ast::*;
 use crate::read::*;
 pub use crate::types::*;
 
+use std::sync::Arc;
+
 #[cfg(test)]
 use crate::machine::copier::CopierTarget;
 
@@ -61,7 +63,7 @@ impl MockWAM {
 
         let mut printer = HCPrinter::new(
             &mut self.machine_st.heap,
-            &mut self.machine_st.atom_tbl,
+            Arc::clone(&self.machine_st.atom_tbl),
             &mut self.machine_st.stack,
             &self.op_dir,
             PrinterOutputter::new(),
@@ -71,11 +73,9 @@ impl MockWAM {
         printer.var_names = term_write_result
             .var_dict
             .into_iter()
-            .map(|(var, cell)| {
+            .map(|(var, cell)| match var {
-                match var {
                 VarKey::VarPtr(var) => (cell, var.clone()),
-                    VarKey::AnonVar(_) => (cell, VarPtr::from(var.to_string()))
+                VarKey::AnonVar(_) => (cell, VarPtr::from(var.to_string())),
-                }
             })
             .collect();
 
@@ -269,10 +269,7 @@ impl Machine {
         .unwrap();
 
         bootstrapping_compile(
-            Stream::from_static_string(
+            Stream::from_static_string(LIBRARIES.borrow()["builtins"], &mut wam.machine_st.arena),
-                LIBRARIES.borrow()["builtins"],
-                &mut wam.machine_st.arena,
-            ),
             &mut wam,
             ListingSource::from_file_and_path(atom!("builtins.pl"), lib_path.clone()),
         )
@@ -346,26 +343,11 @@ mod tests {
         let mut wam = MachineState::new();
         let mut op_dir = default_op_dir();
 
-        op_dir.insert(
+        op_dir.insert((atom!("+"), Fixity::In), OpDesc::build_with(500, YFX as u8));
-            (atom!("+"), Fixity::In),
+        op_dir.insert((atom!("-"), Fixity::In), OpDesc::build_with(500, YFX as u8));
-            OpDesc::build_with(500, YFX as u8),
+        op_dir.insert((atom!("*"), Fixity::In), OpDesc::build_with(500, YFX as u8));
-        );
+        op_dir.insert((atom!("/"), Fixity::In), OpDesc::build_with(400, YFX as u8));
-        op_dir.insert(
+        op_dir.insert((atom!("="), Fixity::In), OpDesc::build_with(700, XFX as u8));
-            (atom!("-"), Fixity::In),
-            OpDesc::build_with(500, YFX as u8),
-        );
-        op_dir.insert(
-            (atom!("*"), Fixity::In),
-            OpDesc::build_with(500, YFX as u8),
-        );
-        op_dir.insert(
-            (atom!("/"), Fixity::In),
-            OpDesc::build_with(400, YFX as u8),
-        );
-        op_dir.insert(
-            (atom!("="), Fixity::In),
-            OpDesc::build_with(700, XFX as u8),
-        );
 
         {
             parse_and_write_parsed_term_to_heap(&mut wam, "f(X,X).", &op_dir).unwrap();
@@ -582,22 +564,10 @@ mod tests {
         let mut wam = MachineState::new();
         let mut op_dir = default_op_dir();
 
-        op_dir.insert(
+        op_dir.insert((atom!("+"), Fixity::In), OpDesc::build_with(500, YFX as u8));
-            (atom!("+"), Fixity::In),
+        op_dir.insert((atom!("-"), Fixity::In), OpDesc::build_with(500, YFX as u8));
-            OpDesc::build_with(500, YFX as u8),
+        op_dir.insert((atom!("*"), Fixity::In), OpDesc::build_with(400, YFX as u8));
-        );
+        op_dir.insert((atom!("/"), Fixity::In), OpDesc::build_with(400, YFX as u8));
-        op_dir.insert(
-            (atom!("-"), Fixity::In),
-            OpDesc::build_with(500, YFX as u8),
-        );
-        op_dir.insert(
-            (atom!("*"), Fixity::In),
-            OpDesc::build_with(400, YFX as u8),
-        );
-        op_dir.insert(
-            (atom!("/"), Fixity::In),
-            OpDesc::build_with(400, YFX as u8),
-        );
 
         {
             parse_and_write_parsed_term_to_heap(&mut wam, "f(X,X).", &op_dir).unwrap();
@@ -688,20 +658,12 @@ mod tests {
         wam.heap.push(heap_loc_as_cell!(1));
 
         assert_eq!(
-            compare_term_test!(
+            compare_term_test!(wam, heap_loc_as_cell!(0), heap_loc_as_cell!(0)),
-                wam,
-                heap_loc_as_cell!(0),
-                heap_loc_as_cell!(0)
-            ),
             Some(Ordering::Equal)
         );
 
         assert_eq!(
-            compare_term_test!(
+            compare_term_test!(wam, heap_loc_as_cell!(0), atom_as_cell!(atom!("a"))),
-                wam,
-                heap_loc_as_cell!(0),
-                atom_as_cell!(atom!("a"))
-            ),
             Some(Ordering::Greater)
         );
 
@@ -724,29 +686,17 @@ mod tests {
         wam.heap.push(empty_list_as_cell!());
 
         assert_eq!(
-            compare_term_test!(
+            compare_term_test!(wam, heap_loc_as_cell!(7), heap_loc_as_cell!(7)),
-                wam,
-                heap_loc_as_cell!(7),
-                heap_loc_as_cell!(7)
-            ),
             Some(Ordering::Equal)
         );
 
         assert_eq!(
-            compare_term_test!(
+            compare_term_test!(wam, heap_loc_as_cell!(0), heap_loc_as_cell!(7)),
-                wam,
-                heap_loc_as_cell!(0),
-                heap_loc_as_cell!(7)
-            ),
             Some(Ordering::Greater)
         );
 
         assert_eq!(
-            compare_term_test!(
+            compare_term_test!(wam, empty_list_as_cell!(), heap_loc_as_cell!(7)),
-                wam,
-                empty_list_as_cell!(),
-                heap_loc_as_cell!(7)
-            ),
             Some(Ordering::Less)
         );
 
@@ -769,40 +719,24 @@ mod tests {
         );
 
         assert_eq!(
-            compare_term_test!(
+            compare_term_test!(wam, empty_list_as_cell!(), atom_as_cell!(atom!("atom"))),
-                wam,
-                empty_list_as_cell!(),
-                atom_as_cell!(atom!("atom"))
-            ),
             Some(Ordering::Less)
         );
 
         assert_eq!(
-            compare_term_test!(
+            compare_term_test!(wam, atom_as_cell!(atom!("atom")), empty_list_as_cell!()),
-                wam,
-                atom_as_cell!(atom!("atom")),
-                empty_list_as_cell!()
-            ),
             Some(Ordering::Greater)
         );
 
         let one_p_one = HeapCellValue::from(float_alloc!(1.1, &mut wam.arena));
 
         assert_eq!(
-            compare_term_test!(
+            compare_term_test!(wam, one_p_one, fixnum_as_cell!(Fixnum::build_with(1))),
-                wam,
-                one_p_one,
-                fixnum_as_cell!(Fixnum::build_with(1))
-            ),
             Some(Ordering::Less)
         );
 
         assert_eq!(
-            compare_term_test!(
+            compare_term_test!(wam, fixnum_as_cell!(Fixnum::build_with(1)), one_p_one),
-                wam,
-                fixnum_as_cell!(Fixnum::build_with(1)),
-                one_p_one
-            ),
             Some(Ordering::Greater)
         );
     }
@@ -821,7 +755,8 @@ mod tests {
         all_cells_unmarked(&wam.heap);
         wam.heap.clear();
 
-        wam.heap.extend(functor!(atom!("f"), [atom(atom!("a")), atom(atom!("b"))]));
+        wam.heap
+            .extend(functor!(atom!("f"), [atom(atom!("a")), atom(atom!("b"))]));
 
         assert!(!wam.is_cyclic_term(str_loc_as_cell!(0)));
 

src/machine/mod.rs

@@ -6,6 +6,7 @@ pub mod code_walker;
 pub mod loader;
 pub mod compile;
 pub mod copier;
+pub mod disjuncts;
 pub mod dispatch;
 pub mod gc;
 pub mod heap;
@@ -16,7 +17,6 @@ pub mod machine_state;
 pub mod machine_state_impl;
 pub mod mock_wam;
 pub mod partial_string;
-pub mod disjuncts;
 pub mod preprocessor;
 pub mod stack;
 pub mod streams;
@@ -27,9 +27,9 @@ pub mod unify;
 use crate::arena::*;
 use crate::arithmetic::*;
 use crate::atom_table::*;
-use crate::forms::*;
 #[cfg(feature = "ffi")]
 use crate::ffi::ForeignFunctionTable;
+use crate::forms::*;
 use crate::instructions::*;
 use crate::machine::args::*;
 use crate::machine::compile::*;
@@ -163,7 +163,10 @@ pub(crate) fn import_builtin_impls(code_dir: &CodeDir, builtins: &mut Module) {
     for key in keys {
         let idx = code_dir.get(&key).unwrap();
         builtins.code_dir.insert(key, idx.clone());
-        builtins.module_decl.exports.push(ModuleExport::PredicateKey(key));
+        builtins
+            .module_decl
+            .exports
+            .push(ModuleExport::PredicateKey(key));
     }
 }
 
@@ -194,7 +197,7 @@ impl Machine {
                 code: &mut self.code,
                 load_contexts: &mut self.load_contexts,
             },
-            &mut self.machine_st
+            &mut self.machine_st,
         )
     }
 
@@ -206,7 +209,11 @@ impl Machine {
         self.machine_st.throw_exception(err);
     }
 
-    fn run_module_predicate(&mut self, module_name: Atom, key: PredicateKey) -> std::process::ExitCode {
+    fn run_module_predicate(
+        &mut self,
+        module_name: Atom,
+        key: PredicateKey,
+    ) -> std::process::ExitCode {
         if let Some(module) = self.indices.modules.get(&module_name) {
             if let Some(ref code_index) = module.code_dir.get(&key) {
                 let p = code_index.local().unwrap();
@@ -223,9 +230,8 @@ impl Machine {
 
     pub fn load_file(&mut self, path: &str, stream: Stream) {
         self.machine_st.registers[1] = stream_as_cell!(stream);
-        self.machine_st.registers[2] = atom_as_cell!(
+        self.machine_st.registers[2] =
-            self.machine_st.atom_tbl.build_with(path)
+            atom_as_cell!(AtomTable::build_with(&self.machine_st.atom_tbl, path));
-        );
 
         self.run_module_predicate(atom!("loader"), (atom!("file_load"), 2));
     }
@@ -236,10 +242,8 @@ impl Machine {
         path_buf.push("src/toplevel.pl");
 
         let path = path_buf.to_str().unwrap();
-        let toplevel_stream = Stream::from_static_string(
+        let toplevel_stream =
-            include_str!("../toplevel.pl"),
+            Stream::from_static_string(include_str!("../toplevel.pl"), &mut self.machine_st.arena);
-            &mut self.machine_st.arena,
-        );
 
         self.load_file(path, toplevel_stream);
 
@@ -292,19 +296,24 @@ impl Machine {
             arg_pstrs.push(put_complete_string(
                 &mut self.machine_st.heap,
                 &arg,
-                &mut self.machine_st.atom_tbl,
+                &self.machine_st.atom_tbl,
             ));
         }
 
-        self.machine_st.registers[1] = heap_loc_as_cell!(
+        self.machine_st.registers[1] = heap_loc_as_cell!(iter_to_heap_list(
-            iter_to_heap_list(&mut self.machine_st.heap, arg_pstrs.into_iter())
+            &mut self.machine_st.heap,
-        );
+            arg_pstrs.into_iter()
+        ));
 
         self.run_module_predicate(atom!("$toplevel"), (atom!("$repl"), 1))
     }
 
     pub(crate) fn configure_modules(&mut self) {
-        fn update_call_n_indices(loader: &Module, target_code_dir: &mut CodeDir, arena: &mut Arena) {
+        fn update_call_n_indices(
+            loader: &Module,
+            target_code_dir: &mut CodeDir,
+            arena: &mut Arena,
+        ) {
             for arity in 1..66 {
                 let key = (atom!("call"), arity);
 
@@ -349,10 +358,18 @@ impl Machine {
             }
 
             for (_, target_module) in self.indices.modules.iter_mut() {
-                update_call_n_indices(&loader, &mut target_module.code_dir, &mut self.machine_st.arena);
+                update_call_n_indices(
+                    &loader,
+                    &mut target_module.code_dir,
+                    &mut self.machine_st.arena,
+                );
             }
 
-            update_call_n_indices(&loader, &mut self.indices.code_dir, &mut self.machine_st.arena);
+            update_call_n_indices(
+                &loader,
+                &mut self.indices.code_dir,
+                &mut self.machine_st.arena,
+            );
 
             self.indices.modules.insert(atom!("loader"), loader);
         } else {
@@ -363,7 +380,8 @@ impl Machine {
     pub(crate) fn add_impls_to_indices(&mut self) {
         let impls_offset = self.code.len() + 3;
 
-        self.code.extend(vec![
+        self.code.extend(
+            vec![
                 Instruction::BreakFromDispatchLoop,
                 Instruction::InstallVerifyAttr,
                 Instruction::VerifyAttrInterrupt,
@@ -375,7 +393,10 @@ impl Machine {
                 Instruction::ExecuteTermNotEqual,
                 Instruction::ExecuteNumberGreaterThan(ar_reg!(temp_v!(1)), ar_reg!(temp_v!(2))),
                 Instruction::ExecuteNumberLessThan(ar_reg!(temp_v!(1)), ar_reg!(temp_v!(2))),
-            Instruction::ExecuteNumberGreaterThanOrEqual(ar_reg!(temp_v!(1)), ar_reg!(temp_v!(2))),
+                Instruction::ExecuteNumberGreaterThanOrEqual(
+                    ar_reg!(temp_v!(1)),
+                    ar_reg!(temp_v!(2)),
+                ),
                 Instruction::ExecuteNumberLessThanOrEqual(ar_reg!(temp_v!(1)), ar_reg!(temp_v!(2))),
                 Instruction::ExecuteNumberEqual(ar_reg!(temp_v!(1)), ar_reg!(temp_v!(2))),
                 Instruction::ExecuteNumberNotEqual(ar_reg!(temp_v!(1)), ar_reg!(temp_v!(2))),
@@ -405,14 +426,19 @@ impl Machine {
                 Instruction::ExecuteIsRational(temp_v!(1)),
                 Instruction::ExecuteIsFloat(temp_v!(1)),
                 Instruction::ExecuteIsNonVar(temp_v!(1)),
-            Instruction::ExecuteIsVar(temp_v!(1))
+                Instruction::ExecuteIsVar(temp_v!(1)),
-        ].into_iter());
+            ]
+            .into_iter(),
+        );
 
         for (p, instr) in self.code[impls_offset..].iter().enumerate() {
             let key = instr.to_name_and_arity();
             self.indices.code_dir.insert(
                 key,
-                CodeIndex::new(IndexPtr::index(p + impls_offset), &mut self.machine_st.arena),
+                CodeIndex::new(
+                    IndexPtr::index(p + impls_offset),
+                    &mut self.machine_st.arena,
+                ),
             );
         }
     }
@@ -428,8 +454,7 @@ impl Machine {
         let user_error = Stream::stderr(&mut machine_st.arena);
 
         #[cfg(not(target_os = "wasi"))]
-        let runtime = tokio::runtime::Runtime::new()
+        let runtime = tokio::runtime::Runtime::new().unwrap();
-            .unwrap();
         #[cfg(target_os = "wasi")]
         let runtime = tokio::runtime::Builder::new_current_thread()
             .enable_all()
@@ -470,10 +495,7 @@ impl Machine {
         .unwrap();
 
         bootstrapping_compile(
-            Stream::from_static_string(
+            Stream::from_static_string(LIBRARIES.borrow()["builtins"], &mut wam.machine_st.arena),
-                LIBRARIES.borrow()["builtins"],
-                &mut wam.machine_st.arena,
-            ),
             &mut wam,
             ListingSource::from_file_and_path(atom!("builtins.pl"), lib_path.clone()),
         )
@@ -526,7 +548,9 @@ impl Machine {
     }
 
     pub(crate) fn configure_streams(&mut self) {
-        self.user_input.options_mut().set_alias_to_atom_opt(Some(atom!("user_input")));
+        self.user_input
+            .options_mut()
+            .set_alias_to_atom_opt(Some(atom!("user_input")));
 
         self.indices
             .stream_aliases
@@ -534,7 +558,9 @@ impl Machine {
 
         self.indices.streams.insert(self.user_input);
 
-        self.user_output.options_mut().set_alias_to_atom_opt(Some(atom!("user_output")));
+        self.user_output
+            .options_mut()
+            .set_alias_to_atom_opt(Some(atom!("user_output")));
 
         self.indices
             .stream_aliases
@@ -564,9 +590,16 @@ impl Machine {
 
                     loop {
                         let indexing_code_ptr = match &indexing_lines[oip] {
-                            &IndexingLine::Indexing(IndexingInstruction::SwitchOnTerm(arg, v, c, l, s)) => {
+                            &IndexingLine::Indexing(IndexingInstruction::SwitchOnTerm(
+                                arg,
+                                v,
+                                c,
+                                l,
+                                s,
+                            )) => {
                                 cell = self.deref_register(arg);
-                                self.machine_st.select_switch_on_term_index(cell, v, c, l, s)
+                                self.machine_st
+                                    .select_switch_on_term_index(cell, v, c, l, s)
                             }
                             IndexingLine::Indexing(IndexingInstruction::SwitchOnConstant(hm)) => {
                                 let lit = self.machine_st.constant_to_literal(cell);
@@ -676,7 +709,12 @@ impl Machine {
                         }
                     );
                 }
-                &Instruction::GetPartialString(Level::Shallow, string, RegType::Temp(t), has_tail) => {
+                &Instruction::GetPartialString(
+                    Level::Shallow,
+                    string,
+                    RegType::Temp(t),
+                    has_tail,
+                ) => {
                     let cell = self.deref_register(t);
 
                     read_heap_cell!(cell,
@@ -707,17 +745,17 @@ impl Machine {
                         }
                     );
                 }
-                Instruction::GetConstant(..) |
+                Instruction::GetConstant(..)
-                Instruction::GetList(..) |
+                | Instruction::GetList(..)
-                Instruction::GetStructure(..) |
+                | Instruction::GetStructure(..)
-                Instruction::GetPartialString(..) |
+                | Instruction::GetPartialString(..)
-                &Instruction::UnifyVoid(..) |
+                | &Instruction::UnifyVoid(..)
-                &Instruction::UnifyConstant(..) |
+                | &Instruction::UnifyConstant(..)
-                &Instruction::GetVariable(..) |
+                | &Instruction::GetVariable(..)
-                &Instruction::GetValue(..) |
+                | &Instruction::GetValue(..)
-                &Instruction::UnifyVariable(..) |
+                | &Instruction::UnifyVariable(..)
-                &Instruction::UnifyValue(..) |
+                | &Instruction::UnifyValue(..)
-                &Instruction::UnifyLocalValue(..)  => {
+                | &Instruction::UnifyLocalValue(..) => {
                     offset += 1;
                 }
                 _ => {
@@ -732,9 +770,10 @@ impl Machine {
     fn next_applicable_clause(&mut self, mut offset: usize) -> Option<usize> {
         while !self.next_clause_applicable(self.machine_st.p + offset + 1) {
             match &self.code[self.machine_st.p + offset] {
-                &Instruction::DefaultRetryMeElse(o) | &Instruction::RetryMeElse(o) |
+                &Instruction::DefaultRetryMeElse(o)
-                &Instruction::DynamicElse(.., NextOrFail::Next(o)) |
+                | &Instruction::RetryMeElse(o)
-                &Instruction::DynamicInternalElse(.., NextOrFail::Next(o)) => offset += o,
+                | &Instruction::DynamicElse(.., NextOrFail::Next(o))
+                | &Instruction::DynamicInternalElse(.., NextOrFail::Next(o)) => offset += o,
                 _ => {
                     return None;
                 }
@@ -753,16 +792,16 @@ impl Machine {
                     match &indexing_lines[self.machine_st.oip as usize] {
                         IndexingLine::IndexedChoice(indexed_choice) => {
                             match &indexed_choice[(self.machine_st.iip + inner_offset) as usize] {
-                                &IndexedChoiceInstruction::Retry(o) |
+                                &IndexedChoiceInstruction::Retry(o)
-                                &IndexedChoiceInstruction::DefaultRetry(o) => {
+                                | &IndexedChoiceInstruction::DefaultRetry(o) => {
                                     if self.next_clause_applicable(self.machine_st.p + o) {
                                         return Some(inner_offset);
                                     }
 
                                     inner_offset += 1;
                                 }
-                                &IndexedChoiceInstruction::Trust(o) |
+                                &IndexedChoiceInstruction::Trust(o)
-                                &IndexedChoiceInstruction::DefaultTrust(o) => {
+                                | &IndexedChoiceInstruction::DefaultTrust(o) => {
                                     return if self.next_clause_applicable(self.machine_st.p + o) {
                                         Some(inner_offset)
                                     } else {
@@ -815,7 +854,8 @@ impl Machine {
             or_frame.prelude.tr = self.machine_st.tr;
             or_frame.prelude.h = self.machine_st.heap.len();
             or_frame.prelude.b0 = self.machine_st.b0;
-            or_frame.prelude.attr_var_queue_len = self.machine_st.attr_var_init.attr_var_queue.len();
+            or_frame.prelude.attr_var_queue_len =
+                self.machine_st.attr_var_init.attr_var_queue.len();
 
             self.machine_st.b = b;
 
@@ -846,7 +886,8 @@ impl Machine {
             or_frame.prelude.tr = self.machine_st.tr;
             or_frame.prelude.h = self.machine_st.heap.len();
             or_frame.prelude.b0 = self.machine_st.b0;
-            or_frame.prelude.attr_var_queue_len = self.machine_st.attr_var_init.attr_var_queue.len();
+            or_frame.prelude.attr_var_queue_len =
+                self.machine_st.attr_var_init.attr_var_queue.len();
 
             self.machine_st.b = b;
 
@@ -1040,15 +1081,17 @@ impl Machine {
     #[inline(always)]
     fn undefined_procedure(&mut self, name: Atom, arity: usize) -> CallResult {
         match self.machine_st.flags.unknown {
-            Unknown::Error => {
+            Unknown::Error => Err(self.machine_st.throw_undefined_error(name, arity)),
-                Err(self.machine_st.throw_undefined_error(name, arity))
-            }
             Unknown::Fail => {
                 self.machine_st.fail = true;
                 Ok(())
             }
             Unknown::Warn => {
-                println!("warning: predicate {}/{} is undefined", name.as_str(), arity);
+                println!(
+                    "warning: predicate {}/{} is undefined",
+                    name.as_str(),
+                    arity
+                );
                 self.machine_st.fail = true;
                 Ok(())
             }
@@ -1093,9 +1136,7 @@ impl Machine {
                 self.machine_st.dynamic_mode = FirstOrNext::First;
                 self.machine_st.execute_at_index(arity, compiled_tl_index);
             }
-            IndexPtrTag::Index => {
+            IndexPtrTag::Index => self.machine_st.execute_at_index(arity, compiled_tl_index),
-                self.machine_st.execute_at_index(arity, compiled_tl_index)
-            }
         }
 
         Ok(())
@@ -1120,7 +1161,9 @@ impl Machine {
                 }
             } else {
                 let stub = functor_stub(name, arity);
-                let err = self.machine_st.module_resolution_error(module_name, name, arity);
+                let err = self
+                    .machine_st
+                    .module_resolution_error(module_name, name, arity);
 
                 Err(self.machine_st.error_form(err, stub))
             }
@@ -1146,7 +1189,9 @@ impl Machine {
                 }
             } else {
                 let stub = functor_stub(name, arity);
-                let err = self.machine_st.module_resolution_error(module_name, name, arity);
+                let err = self
+                    .machine_st
+                    .module_resolution_error(module_name, name, arity);
 
                 Err(self.machine_st.error_form(err, stub))
             }
@@ -1180,10 +1225,14 @@ impl Machine {
                 let r_c_wo_h_atom = atom!("run_cleaners_without_handling");
                 let iso_ext = atom!("iso_ext");
 
-                RCWH = self.indices.get_predicate_code_index(r_c_w_h_atom, 0, iso_ext)
+                RCWH = self
+                    .indices
+                    .get_predicate_code_index(r_c_w_h_atom, 0, iso_ext)
                     .and_then(|item| item.local())
                     .unwrap();
-                RCWOH = self.indices.get_predicate_code_index(r_c_wo_h_atom, 1, iso_ext)
+                RCWOH = self
+                    .indices
+                    .get_predicate_code_index(r_c_wo_h_atom, 1, iso_ext)
                     .and_then(|item| item.local())
                     .unwrap();
             });
@@ -1196,9 +1245,8 @@ impl Machine {
                 let (idx, arity) = if self.machine_st.effective_block() > prev_block {
                     (r_c_w_h, 0)
                 } else {
-                    self.machine_st.registers[1] = fixnum_as_cell!(
+                    self.machine_st.registers[1] =
-                        Fixnum::build_with(b_cutoff as i64)
+                        fixnum_as_cell!(Fixnum::build_with(b_cutoff as i64));
-                    );
 
                     (r_c_wo_h, 1)
                 };
@@ -1265,8 +1313,7 @@ impl Machine {
                         None => unreachable!(),
                     }
                 }
-                TrailEntryTag::TrailedAttachedValue => {
+                TrailEntryTag::TrailedAttachedValue => {}
-                }
             }
         }
     }

src/machine/partial_string.rs

@@ -43,10 +43,9 @@ impl Into<Atom> for PartialString {
 
 impl PartialString {
     #[inline]
-    pub(super) fn new<'a>(src: &'a str, atom_tbl: &mut AtomTable) -> Option<(Self, &'a str)> {
+    pub(super) fn new<'a>(src: &'a str, atom_tbl: &AtomTable) -> Option<(Self, &'a str)> {
         let terminator_idx = scan_for_terminator(src.chars());
-        let pstr = PartialString(atom_tbl.build_with(&src[.. terminator_idx]));
+        let pstr = PartialString(AtomTable::build_with(&atom_tbl, &src[..terminator_idx]));
-
         Some(if terminator_idx < src.as_bytes().len() {
             (pstr, &src[terminator_idx + 1..])
         } else {
@@ -55,8 +54,8 @@ impl PartialString {
     }
 
     #[inline(always)]
-    pub(crate) fn as_str_from(&self, n: usize) -> &str {
+    pub(crate) fn as_str_from(&self, n: usize) -> AtomString {
-        &self.0.as_str()[n..]
+        self.0.as_str().map(|str| &str[n..])
     }
 }
 
@@ -124,7 +123,11 @@ impl<'a> HeapPStrIter<'a> {
 
         let mut final_result = None;
 
-        while let Some(PStrIterStep { iteratee, next_hare }) = self.step(self.brent_st.hare) {
+        while let Some(PStrIterStep {
+            iteratee,
+            next_hare,
+        }) = self.step(self.brent_st.hare)
+        {
             self.brent_st.hare = next_hare;
             self.focus = self.heap[iteratee.focus()];
 
@@ -151,7 +154,7 @@ impl<'a> HeapPStrIter<'a> {
                     let s = &s[result.prefix_len..];
 
                     if s.len() >= t.len() {
-                        if s.starts_with(t) {
+                        if (&*s).starts_with(&*t) {
                             result.prefix_len += t.len();
                             result.offset += t.len();
                         } else {
@@ -225,7 +228,7 @@ impl<'a> HeapPStrIter<'a> {
                 }
                 PStrIteratee::PStrSegment(_, pstr_atom, n) => {
                     let pstr = PartialString::from(pstr_atom);
-                    buf += pstr.as_str_from(n);
+                    buf += &*pstr.as_str_from(n);
                 }
             }
         }
@@ -381,8 +384,10 @@ impl<'a> HeapPStrIter<'a> {
     }
 
     fn pre_cycle_discovery_stepper(&mut self) -> Option<PStrIteratee> {
-        let PStrIterStep { iteratee, next_hare } =
+        let PStrIterStep {
-            match self.step(self.brent_st.hare) {
+            iteratee,
+            next_hare,
+        } = match self.step(self.brent_st.hare) {
             Some(results) => results,
             None => {
                 return None;
@@ -421,8 +426,10 @@ impl<'a> HeapPStrIter<'a> {
             return None;
         }
 
-        let PStrIterStep { iteratee, next_hare } =
+        let PStrIterStep {
-            match self.step(self.brent_st.hare) {
+            iteratee,
+            next_hare,
+        } = match self.step(self.brent_st.hare) {
             Some(results) => results,
             None => {
                 return None;
@@ -515,11 +522,8 @@ impl<'a> Iterator for PStrCharsIter<'a> {
 
                     match pstr.as_str_from(n).chars().next() {
                         Some(c) => {
-                            self.item = Some(PStrIteratee::PStrSegment(
+                            self.item =
-                                f1,
+                                Some(PStrIteratee::PStrSegment(f1, pstr_atom, n + c.len_utf8()));
-                                pstr_atom,
-                                n + c.len_utf8(),
-                            ));
 
                             return Some(c);
                         }
@@ -684,8 +688,10 @@ pub fn compare_pstr_prefixes<'a>(
                             }
                         }
                     }
-                    (PStrIteratee::PStrSegment(f1, pstr1_atom, n1),
+                    (
-                     PStrIteratee::PStrSegment(f2, pstr2_atom, n2)) => {
+                        PStrIteratee::PStrSegment(f1, pstr1_atom, n1),
+                        PStrIteratee::PStrSegment(f2, pstr2_atom, n2),
+                    ) => {
                         if pstr1_atom == pstr2_atom && n1 == n2 {
                             cycle_detection_step(i1, i2, &step_1);
                             let both_cyclic = cycle_detection_step(i2, i1, &step_2);
@@ -707,7 +713,7 @@ pub fn compare_pstr_prefixes<'a>(
                         let str2 = pstr2.as_str_from(n2);
 
                         match str1.len().cmp(&str2.len()) {
-                            Ordering::Equal if str1 == str2 => {
+                            Ordering::Equal if &*str1 == &*str2 => {
                                 cycle_detection_step(i1, i2, &step_1);
                                 let both_cyclic = cycle_detection_step(i2, i1, &step_2);
 
@@ -718,8 +724,9 @@ pub fn compare_pstr_prefixes<'a>(
                                     continue;
                                 }
                             }
-                            Ordering::Less if str2.starts_with(str1) => {
+                            Ordering::Less if str2.starts_with(&*str1) => {
-                                step_2.iteratee = PStrIteratee::PStrSegment(f2, pstr2_atom, n2 + str1.len());
+                                step_2.iteratee =
+                                    PStrIteratee::PStrSegment(f2, pstr2_atom, n2 + str1.len());
                                 let c1_result = cycle_detection_step(i1, i2, &step_1);
                                 r1 = step(i1, i1.brent_st.hare);
 
@@ -727,8 +734,9 @@ pub fn compare_pstr_prefixes<'a>(
                                     continue;
                                 }
                             }
-                            Ordering::Greater if str1.starts_with(str2) => {
+                            Ordering::Greater if str1.starts_with(&*str2) => {
-                                step_1.iteratee = PStrIteratee::PStrSegment(f1, pstr1_atom, n1 + str2.len());
+                                step_1.iteratee =
+                                    PStrIteratee::PStrSegment(f1, pstr1_atom, n1 + str2.len());
                                 let c2_result = cycle_detection_step(i2, i1, &step_2);
                                 r2 = step(i2, i2.brent_st.hare);
 
@@ -737,7 +745,7 @@ pub fn compare_pstr_prefixes<'a>(
                                 }
                             }
                             _ => {
-                                return PStrCmpResult::Ordered(str1.cmp(str2));
+                                return PStrCmpResult::Ordered(str1.cmp(&*str2));
                             }
                         }
                     }
@@ -796,11 +804,8 @@ mod test {
     fn pstr_iter_tests() {
         let mut wam = MockWAM::new();
 
-        let pstr_var_cell = put_partial_string(
+        let pstr_var_cell =
-            &mut wam.machine_st.heap,
+            put_partial_string(&mut wam.machine_st.heap, "abc ", &wam.machine_st.atom_tbl);
-            "abc ",
-            &mut wam.machine_st.atom_tbl,
-        );
 
         let pstr_cell = wam.machine_st.heap[pstr_var_cell.get_value() as usize];
 
@@ -819,11 +824,8 @@ mod test {
         wam.machine_st.heap.pop();
         wam.machine_st.heap.push(pstr_loc_as_cell!(2));
 
-        let pstr_second_var_cell = put_partial_string(
+        let pstr_second_var_cell =
-            &mut wam.machine_st.heap,
+            put_partial_string(&mut wam.machine_st.heap, "def", &wam.machine_st.atom_tbl);
-            "def",
-            &mut wam.machine_st.atom_tbl,
-        );
 
         let pstr_second_cell = wam.machine_st.heap[pstr_second_var_cell.get_value() as usize];
 
@@ -836,7 +838,11 @@ mod test {
             );
             assert_eq!(
                 iter.next(),
-                Some(PStrIteratee::PStrSegment(2, cell_as_atom!(pstr_second_cell), 0))
+                Some(PStrIteratee::PStrSegment(
+                    2,
+                    cell_as_atom!(pstr_second_cell),
+                    0
+                ))
             );
 
             assert_eq!(iter.next(), None);
@@ -855,7 +861,11 @@ mod test {
             );
             assert_eq!(
                 iter.next(),
-                Some(PStrIteratee::PStrSegment(2, cell_as_atom!(pstr_second_cell), 0))
+                Some(PStrIteratee::PStrSegment(
+                    2,
+                    cell_as_atom!(pstr_second_cell),
+                    0
+                ))
             );
 
             assert_eq!(iter.next(), None);
@@ -863,10 +873,14 @@ mod test {
         }
 
         wam.machine_st.heap.pop();
-        wam.machine_st.heap.push(pstr_loc_as_cell!(wam.machine_st.heap.len() + 1));
+        wam.machine_st
+            .heap
+            .push(pstr_loc_as_cell!(wam.machine_st.heap.len() + 1));
 
         wam.machine_st.heap.push(pstr_offset_as_cell!(0));
-        wam.machine_st.heap.push(fixnum_as_cell!(Fixnum::build_with(0)));
+        wam.machine_st
+            .heap
+            .push(fixnum_as_cell!(Fixnum::build_with(0)));
 
         {
             let mut iter = HeapPStrIter::new(&wam.machine_st.heap, 0);
@@ -892,21 +906,13 @@ mod test {
             // construct a structurally similar but different cyclic partial string
             // matching the one beginning at wam.machine_st.heap[0].
 
-            put_partial_string(
+            put_partial_string(&mut wam.machine_st.heap, "ab", &wam.machine_st.atom_tbl);
-                &mut wam.machine_st.heap,
-                "ab",
-                &mut wam.machine_st.atom_tbl,
-            );
 
             wam.machine_st.heap.pop();
 
             wam.machine_st.heap.push(pstr_loc_as_cell!(second_h + 2));
 
-            put_partial_string(
+            put_partial_string(&mut wam.machine_st.heap, "c ", &wam.machine_st.atom_tbl);
-                &mut wam.machine_st.heap,
-                "c ",
-                &mut wam.machine_st.atom_tbl,
-            );
 
             wam.machine_st.heap.pop();
 
@@ -916,7 +922,9 @@ mod test {
             wam.machine_st.heap.push(pstr_loc_as_cell!(second_h + 6));
 
             wam.machine_st.heap.push(pstr_offset_as_cell!(second_h));
-            wam.machine_st.heap.push(fixnum_as_cell!(Fixnum::build_with(0)));
+            wam.machine_st
+                .heap
+                .push(fixnum_as_cell!(Fixnum::build_with(0)));
 
             let mut iter1 = HeapPStrIter::new(&wam.machine_st.heap, 0);
             let mut iter2 = HeapPStrIter::new(&wam.machine_st.heap, second_h);
@@ -929,11 +937,7 @@ mod test {
 
         wam.machine_st.heap.clear();
 
-        put_partial_string(
+        put_partial_string(&mut wam.machine_st.heap, "abc ", &wam.machine_st.atom_tbl);
-            &mut wam.machine_st.heap,
-            "abc ",
-            &mut wam.machine_st.atom_tbl,
-        );
 
         let pstr_cell = wam.machine_st.heap[0];
 
@@ -963,11 +967,8 @@ mod test {
 
         wam.machine_st.heap.clear();
 
-        let cstr_var_cell = put_complete_string(
+        let cstr_var_cell =
-            &mut wam.machine_st.heap,
+            put_complete_string(&mut wam.machine_st.heap, "abc", &wam.machine_st.atom_tbl);
-            "abc",
-            &mut wam.machine_st.atom_tbl,
-        );
 
         wam.machine_st.heap.push(list_loc_as_cell!(2));
         wam.machine_st.heap.push(heap_loc_as_cell!(2));
@@ -982,30 +983,18 @@ mod test {
 
         unify!(wam.machine_st, cstr_var_cell, heap_loc_as_cell!(1));
 
-        assert_eq!(
+        assert_eq!(wam.machine_st.heap[2], char_as_cell!('a'),);
-            wam.machine_st.heap[2],
-            char_as_cell!('a'),
-        );
 
-        assert_eq!(
+        assert_eq!(wam.machine_st.heap[4], char_as_cell!('b'),);
-            wam.machine_st.heap[4],
-            char_as_cell!('b'),
-        );
 
-        assert_eq!(
+        assert_eq!(wam.machine_st.heap[6], char_as_cell!('c'),);
-            wam.machine_st.heap[6],
-            char_as_cell!('c'),
-        );
 
         // test "abc" = [X,Y,Z|D].
 
         wam.machine_st.heap.clear();
 
-        let cstr_var_cell = put_complete_string(
+        let cstr_var_cell =
-            &mut wam.machine_st.heap,
+            put_complete_string(&mut wam.machine_st.heap, "abc", &wam.machine_st.atom_tbl);
-            "abc",
-            &mut wam.machine_st.atom_tbl,
-        );
 
         wam.machine_st.heap.push(list_loc_as_cell!(2));
         wam.machine_st.heap.push(heap_loc_as_cell!(2)); // X
@@ -1022,35 +1011,20 @@ mod test {
 
         assert_eq!(wam.machine_st.fail, false);
 
-        assert_eq!(
+        assert_eq!(wam.machine_st.heap[2], char_as_cell!('a'),);
-            wam.machine_st.heap[2],
-            char_as_cell!('a'),
-        );
 
-        assert_eq!(
+        assert_eq!(wam.machine_st.heap[4], char_as_cell!('b'),);
-            wam.machine_st.heap[4],
-            char_as_cell!('b'),
-        );
 
-        assert_eq!(
+        assert_eq!(wam.machine_st.heap[6], char_as_cell!('c'),);
-            wam.machine_st.heap[6],
-            char_as_cell!('c'),
-        );
 
-        assert_eq!(
+        assert_eq!(wam.machine_st.heap[7], empty_list_as_cell!(),);
-            wam.machine_st.heap[7],
-            empty_list_as_cell!(),
-        );
 
         // test "d" = [d].
 
         wam.machine_st.heap.clear();
 
-        let cstr_var_cell = put_complete_string(
+        let cstr_var_cell =
-            &mut wam.machine_st.heap,
+            put_complete_string(&mut wam.machine_st.heap, "d", &wam.machine_st.atom_tbl);
-            "d",
-            &mut wam.machine_st.atom_tbl,
-        );
 
         wam.machine_st.heap.push(list_loc_as_cell!(2));
         wam.machine_st.heap.push(char_as_cell!('d'));
@@ -1064,11 +1038,8 @@ mod test {
 
         wam.machine_st.heap.clear();
 
-        let cstr_var_cell = put_complete_string(
+        let cstr_var_cell =
-            &mut wam.machine_st.heap,
+            put_complete_string(&mut wam.machine_st.heap, "abc", &wam.machine_st.atom_tbl);
-            "abc",
-            &mut wam.machine_st.atom_tbl,
-        );
 
         wam.machine_st.heap.push(list_loc_as_cell!(2));
         wam.machine_st.heap.push(heap_loc_as_cell!(2));
@@ -1085,30 +1056,17 @@ mod test {
 
         assert_eq!(wam.machine_st.fail, false);
 
-        assert_eq!(
+        assert_eq!(wam.machine_st.heap[2], char_as_cell!('a'),);
-            wam.machine_st.heap[2],
-            char_as_cell!('a'),
-        );
 
-        assert_eq!(
+        assert_eq!(wam.machine_st.heap[4], char_as_cell!('b'),);
-            wam.machine_st.heap[4],
-            char_as_cell!('b'),
-        );
 
-        assert_eq!(
+        assert_eq!(wam.machine_st.heap[6], char_as_cell!('c'),);
-            wam.machine_st.heap[6],
-            char_as_cell!('c'),
-        );
 
         // test "abcdef" = [a,b,c|X].
 
         wam.machine_st.heap.clear();
 
-        put_complete_string(
+        put_complete_string(&mut wam.machine_st.heap, "abcdef", &wam.machine_st.atom_tbl);
-            &mut wam.machine_st.heap,
-            "abcdef",
-            &mut wam.machine_st.atom_tbl,
-        );
 
         wam.machine_st.heap.push(pstr_as_cell!(atom!("abc")));
         wam.machine_st.heap.push(heap_loc_as_cell!(2));
@@ -1123,7 +1081,10 @@ mod test {
         assert_eq!(wam.machine_st.heap[3], pstr_loc_as_cell!(1));
         assert_eq!(wam.machine_st.heap[4], atom_as_cstr_cell!(atom!("abcdef")));
         assert_eq!(wam.machine_st.heap[5], pstr_offset_as_cell!(4));
-        assert_eq!(wam.machine_st.heap[6], fixnum_as_cell!(Fixnum::build_with("abc".len() as i64)));
+        assert_eq!(
+            wam.machine_st.heap[6],
+            fixnum_as_cell!(Fixnum::build_with("abc".len() as i64))
+        );
 
         // test iteration on X = [b,c,b,c,b,c,b,c|...] as an offset.
 
@@ -1132,7 +1093,9 @@ mod test {
         wam.machine_st.heap.push(pstr_as_cell!(atom!("abc")));
         wam.machine_st.heap.push(pstr_loc_as_cell!(2));
         wam.machine_st.heap.push(pstr_offset_as_cell!(0));
-        wam.machine_st.heap.push(fixnum_as_cell!(Fixnum::build_with(1)));
+        wam.machine_st
+            .heap
+            .push(fixnum_as_cell!(Fixnum::build_with(1)));
 
         {
             let mut iter = HeapPStrIter::new(&wam.machine_st.heap, 2);

src/machine/preprocessor.rs

@@ -12,11 +12,7 @@ use indexmap::IndexSet;
 use std::cell::Cell;
 use std::convert::TryFrom;
 
-pub(crate) fn to_op_decl(
+pub(crate) fn to_op_decl(prec: u16, spec: Atom, name: Atom) -> Result<OpDecl, CompilationError> {
-    prec: u16,
-    spec: Atom,
-    name: Atom,
-) -> Result<OpDecl, CompilationError> {
     match spec {
         atom!("xfx") => Ok(OpDecl::new(OpDesc::build_with(prec, XFX as u8), name)),
         atom!("xfy") => Ok(OpDecl::new(OpDesc::build_with(prec, XFY as u8), name)),
@@ -29,19 +25,16 @@ pub(crate) fn to_op_decl(
     }
 }
 
-fn setup_op_decl(
+fn setup_op_decl(mut terms: Vec<Term>, atom_tbl: &AtomTable) -> Result<OpDecl, CompilationError> {
-    mut terms: Vec<Term>,
-    atom_tbl: &mut AtomTable,
-) -> Result<OpDecl, CompilationError> {
     let name = match terms.pop().unwrap() {
         Term::Literal(_, Literal::Atom(name)) => name,
-        Term::Literal(_, Literal::Char(c)) => atom_tbl.build_with(&c.to_string()),
+        Term::Literal(_, Literal::Char(c)) => AtomTable::build_with(atom_tbl, &c.to_string()),
         _ => return Err(CompilationError::InconsistentEntry),
     };
 
     let spec = match terms.pop().unwrap() {
         Term::Literal(_, Literal::Atom(name)) => name,
-        Term::Literal(_, Literal::Char(c)) => atom_tbl.build_with(&c.to_string()),
+        Term::Literal(_, Literal::Char(c)) => AtomTable::build_with(atom_tbl, &c.to_string()),
         _ => return Err(CompilationError::InconsistentEntry),
     };
 
@@ -68,12 +61,14 @@ fn setup_predicate_indicator(term: &mut Term) -> Result<PredicateKey, Compilatio
                 Term::Literal(_, Literal::Integer(n)) => n.to_usize(),
                 Term::Literal(_, Literal::Fixnum(n)) => usize::try_from(n.get_num()).ok(),
                 _ => None,
-            }.ok_or(CompilationError::InvalidModuleExport)?;
+            }
+            .ok_or(CompilationError::InvalidModuleExport)?;
 
             let name = match name {
                 Term::Literal(_, Literal::Atom(name)) => Some(name),
                 _ => None,
-            }.ok_or(CompilationError::InvalidModuleExport)?;
+            }
+            .ok_or(CompilationError::InvalidModuleExport)?;
 
             if *slash == atom!("/") {
                 Ok((name, arity))
@@ -87,7 +82,7 @@ fn setup_predicate_indicator(term: &mut Term) -> Result<PredicateKey, Compilatio
 
 fn setup_module_export(
     mut term: Term,
-    atom_tbl: &mut AtomTable,
+    atom_tbl: &AtomTable,
 ) -> Result<ModuleExport, CompilationError> {
     setup_predicate_indicator(&mut term)
         .map(ModuleExport::PredicateKey)
@@ -113,7 +108,7 @@ pub(crate) fn build_rule_body(vars: &[Term], body_term: Term) -> Term {
 
 pub(super) fn setup_module_export_list(
     mut export_list: Term,
-    atom_tbl: &mut AtomTable,
+    atom_tbl: &AtomTable,
 ) -> Result<Vec<ModuleExport>, CompilationError> {
     let mut exports = vec![];
 
@@ -133,7 +128,7 @@ pub(super) fn setup_module_export_list(
 
 fn setup_module_decl(
     mut terms: Vec<Term>,
-    atom_tbl: &mut AtomTable,
+    atom_tbl: &AtomTable,
 ) -> Result<ModuleDecl, CompilationError> {
     let export_list = terms.pop().unwrap();
     let name = terms.pop().unwrap();
@@ -141,7 +136,8 @@ fn setup_module_decl(
     let name = match name {
         Term::Literal(_, Literal::Atom(name)) => Some(name),
         _ => None,
-    }.ok_or(CompilationError::InvalidModuleDecl)?;
+    }
+    .ok_or(CompilationError::InvalidModuleDecl)?;
 
     let exports = setup_module_export_list(export_list, atom_tbl)?;
 
@@ -150,9 +146,7 @@ fn setup_module_decl(
 
 fn setup_use_module_decl(mut terms: Vec<Term>) -> Result<ModuleSource, CompilationError> {
     match terms.pop().unwrap() {
-        Term::Clause(_, name, mut terms)
+        Term::Clause(_, name, mut terms) if name == atom!("library") && terms.len() == 1 => {
-            if name == atom!("library") && terms.len() == 1 =>
-        {
             match terms.pop().unwrap() {
                 Term::Literal(_, Literal::Atom(name)) => Ok(ModuleSource::Library(name)),
                 _ => Err(CompilationError::InvalidModuleDecl),
@@ -167,13 +161,11 @@ type UseModuleExport = (ModuleSource, IndexSet<ModuleExport>);
 
 fn setup_qualified_import(
     mut terms: Vec<Term>,
-    atom_tbl: &mut AtomTable,
+    atom_tbl: &AtomTable,
 ) -> Result<UseModuleExport, CompilationError> {
     let mut export_list = terms.pop().unwrap();
     let module_src = match terms.pop().unwrap() {
-        Term::Clause(_, name, mut terms)
+        Term::Clause(_, name, mut terms) if name == atom!("library") && terms.len() == 1 => {
-            if name == atom!("library") && terms.len() == 1 =>
-        {
             match terms.pop().unwrap() {
                 Term::Literal(_, Literal::Atom(name)) => Ok(ModuleSource::Library(name)),
                 _ => Err(CompilationError::InvalidModuleDecl),
@@ -318,11 +310,11 @@ pub(super) fn setup_declaration<'a, LS: LoadState<'a>>(
             }
             (atom!("module"), 2) => {
                 let atom_tbl = &mut LS::machine_st(&mut loader.payload).atom_tbl;
-                Ok(Declaration::Module(setup_module_decl(terms, atom_tbl)?))
+                Ok(Declaration::Module(setup_module_decl(terms, &atom_tbl)?))
             }
             (atom!("op"), 3) => {
                 let atom_tbl = &mut LS::machine_st(&mut loader.payload).atom_tbl;
-                Ok(Declaration::Op(setup_op_decl(terms, atom_tbl)?))
+                Ok(Declaration::Op(setup_op_decl(terms, &atom_tbl)?))
             }
             (atom!("non_counted_backtracking"), 1) => {
                 let (name, arity) = setup_predicate_indicator(&mut terms.pop().unwrap())?;
@@ -331,7 +323,7 @@ pub(super) fn setup_declaration<'a, LS: LoadState<'a>>(
             (atom!("use_module"), 1) => Ok(Declaration::UseModule(setup_use_module_decl(terms)?)),
             (atom!("use_module"), 2) => {
                 let atom_tbl = &mut LS::machine_st(&mut loader.payload).atom_tbl;
-                let (name, exports) = setup_qualified_import(terms, atom_tbl)?;
+                let (name, exports) = setup_qualified_import(terms, &atom_tbl)?;
 
                 Ok(Declaration::UseQualifiedModule(name, exports))
             }
@@ -381,19 +373,28 @@ fn build_meta_predicate_clause<'a, LS: LoadState<'a>>(
                 }
 
                 fn tag_with_module_name(module_name: Atom, term: Term) -> Term {
-                    Term::Clause(Cell::default(), atom!(":"), vec![
+                    Term::Clause(
+                        Cell::default(),
+                        atom!(":"),
+                        vec![
                             Term::Literal(Cell::default(), Literal::Atom(module_name)),
-                        term
+                            term,
-                    ])
+                        ],
+                    )
                 }
 
                 let process_term: fn(Atom, Term) -> Term;
 
                 let (module_name, key, term) = match term {
                     Term::Clause(cell, atom!(":"), mut terms) if terms.len() == 2 => {
-                        if let Some((module_name, name)) = get_qualified_name(&terms[0], &terms[1]) {
+                        if let Some((module_name, name)) = get_qualified_name(&terms[0], &terms[1])
+                        {
                             process_term = tag_with_module_name;
-                            (module_name, (name, terms[1].arity() + supp_args), terms.pop().unwrap())
+                            (
+                                module_name,
+                                (name, terms[1].arity() + supp_args),
+                                terms.pop().unwrap(),
+                            )
                         } else {
                             arg_terms.push(Term::Clause(cell, atom!(":"), terms));
                             continue;
@@ -408,10 +409,8 @@ fn build_meta_predicate_clause<'a, LS: LoadState<'a>>(
                 let term = match term {
                     Term::Clause(cell, name, mut terms) => {
                         if let Some(Term::Literal(_, Literal::CodeIndex(_))) = terms.last() {
-                            arg_terms.push(process_term(
+                            arg_terms
-                                module_name,
+                                .push(process_term(module_name, Term::Clause(cell, name, terms)));
-                                Term::Clause(cell, name, terms),
-                            ));
 
                             continue;
                         }
@@ -424,11 +423,14 @@ fn build_meta_predicate_clause<'a, LS: LoadState<'a>>(
                     Term::Literal(cell, Literal::Atom(name)) => {
                         let idx = loader.get_or_insert_qualified_code_index(module_name, key);
 
-                        process_term(module_name, Term::Clause(
+                        process_term(
+                            module_name,
+                            Term::Clause(
                                 cell,
                                 name,
                                 vec![Term::Literal(Cell::default(), Literal::CodeIndex(idx))],
-                        ))
+                            ),
+                        )
                     }
                     term => term,
                 };
@@ -462,12 +464,7 @@ pub(super) fn clause_to_query_term<'a, LS: LoadState<'a>>(
     if let ClauseType::Named(arity, name, idx) = ct {
         if let Some(meta_specs) = loader.get_meta_specs(name, arity).cloned() {
             let module_name = loader.payload.compilation_target.module_name();
-            let terms = build_meta_predicate_clause(
+            let terms = build_meta_predicate_clause(loader, module_name, terms, meta_specs);
-                loader,
-                module_name,
-                terms,
-                meta_specs,
-            );
 
             return QueryTerm::Clause(
                 Cell::default(),
@@ -501,12 +498,7 @@ pub(super) fn qualified_clause_to_query_term<'a, LS: LoadState<'a>>(
 
     if let ClauseType::Named(arity, name, idx) = ct {
         if let Some(meta_specs) = loader.get_meta_specs(name, arity).cloned() {
-            let terms = build_meta_predicate_clause(
+            let terms = build_meta_predicate_clause(loader, module_name, terms, meta_specs);
-                loader,
-                module_name,
-                terms,
-                meta_specs,
-            );
 
             return QueryTerm::Clause(
                 Cell::default(),
@@ -529,17 +521,13 @@ pub(crate) struct Preprocessor {
 
 impl Preprocessor {
     pub(super) fn new(settings: CodeGenSettings) -> Self {
-        Preprocessor {
+        Preprocessor { settings }
-            settings,
-        }
     }
 
     fn setup_fact(&mut self, term: Term) -> Result<(Fact, VarData), CompilationError> {
         match term {
             Term::Clause(..) | Term::Literal(_, Literal::Atom(..)) => {
-                let classifier = VariableClassifier::new(
+                let classifier = VariableClassifier::new(self.settings.default_call_policy());
-                    self.settings.default_call_policy(),
-                );
 
                 let (head, var_data) = classifier.classify_fact(term)?;
                 Ok((Fact { head }, var_data))
@@ -554,21 +542,25 @@ impl Preprocessor {
         head: Term,
         body: Term,
     ) -> Result<(Rule, VarData), CompilationError> {
-        let classifier = VariableClassifier::new(
+        let classifier = VariableClassifier::new(self.settings.default_call_policy());
-            self.settings.default_call_policy(),
-        );
 
         let (head, clauses, var_data) = classifier.classify_rule(loader, head, body)?;
 
         match head {
-            Term::Clause(_, name, terms) => Ok((Rule {
+            Term::Clause(_, name, terms) => Ok((
+                Rule {
                     head: (name, terms),
                     clauses,
-            }, var_data)),
+                },
-            Term::Literal(_, Literal::Atom(name)) => Ok((Rule {
+                var_data,
+            )),
+            Term::Literal(_, Literal::Atom(name)) => Ok((
+                Rule {
                     head: (name, vec![]),
                     clauses,
-            }, var_data)),
+                },
+                var_data,
+            )),
             _ => Err(CompilationError::InvalidRuleHead),
         }
     }

src/machine/stack.rs

@@ -30,12 +30,6 @@ pub struct Stack {
     _marker: PhantomData<HeapCellValue>,
 }
 
-impl Drop for Stack {
-    fn drop(&mut self) {
-        self.buf.deallocate();
-    }
-}
-
 #[derive(Debug)]
 pub(crate) struct AndFramePrelude {
     pub(crate) num_cells: usize,
@@ -189,7 +183,7 @@ impl Stack {
         let frame_size = AndFrame::size_of(num_cells);
 
         unsafe {
-            let e = self.buf.ptr as usize - self.buf.base as usize;
+            let e = (*self.buf.ptr.get_mut()) as usize - self.buf.base as usize;
             let new_ptr = self.alloc(frame_size);
             let mut offset = prelude_size::<AndFramePrelude>();
 
@@ -213,7 +207,7 @@ impl Stack {
         let frame_size = OrFrame::size_of(num_cells);
 
         unsafe {
-            let b = self.buf.ptr as usize - self.buf.base as usize;
+            let b = (*self.buf.ptr.get_mut()) as usize - self.buf.base as usize;
             let new_ptr = self.alloc(frame_size);
             let mut offset = prelude_size::<OrFramePrelude>();
 
@@ -269,8 +263,8 @@ impl Stack {
     pub(crate) fn truncate(&mut self, b: usize) {
         let base = self.buf.base as usize + b;
 
-        if base < self.buf.ptr as usize {
+        if base < (*self.buf.ptr.get_mut()) as usize {
-            self.buf.ptr = base as *mut _;
+            *self.buf.ptr.get_mut() = base as *mut _;
         }
     }
 }
@@ -315,7 +309,10 @@ mod tests {
         let and_frame = wam.machine_st.stack.index_and_frame_mut(next_e);
 
         for idx in 0..9 {
-            assert_eq!(and_frame[idx + 1], stack_loc_as_cell!(AndFrame, next_e, idx + 1));
+            assert_eq!(
+                and_frame[idx + 1],
+                stack_loc_as_cell!(AndFrame, next_e, idx + 1)
+            );
         }
 
         let and_frame = wam.machine_st.stack.index_and_frame(e);

src/machine/streams.rs

@@ -4,13 +4,13 @@ use crate::parser::ast::*;
 use crate::parser::char_reader::*;
 use crate::read::*;
 
+#[cfg(feature = "http")]
+use crate::http::HttpResponse;
 use crate::machine::heap::*;
 use crate::machine::machine_errors::*;
 use crate::machine::machine_indices::*;
 use crate::machine::machine_state::*;
 use crate::types::*;
-#[cfg(feature = "http")]
-use crate::http::HttpResponse;
 
 pub use modular_bitfield::prelude::*;
 
@@ -19,11 +19,11 @@ use std::error::Error;
 use std::fmt;
 use std::fmt::Debug;
 use std::fs::{File, OpenOptions};
-use std::hash::{Hash};
+use std::hash::Hash;
 use std::io;
 use std::io::{BufRead, Cursor, ErrorKind, Read, Seek, SeekFrom, Write};
 use std::mem;
-use std::net::{TcpStream, Shutdown};
+use std::net::{Shutdown, TcpStream};
 use std::ops::{Deref, DerefMut};
 use std::ptr;
 
@@ -154,7 +154,9 @@ impl StreamLayout<CharReader<InputFileStream>> {
     fn position(&mut self) -> Option<u64> {
         // stream is the internal CharReader. subtract
         // its pending buffer length from position.
-        self.get_mut().file.seek(SeekFrom::Current(0))
+        self.get_mut()
+            .file
+            .seek(SeekFrom::Current(0))
             .map(|pos| pos - self.stream.rem_buf_len() as u64)
             .ok()
     }
@@ -205,7 +207,9 @@ impl CharRead for StaticStringStream {
 
     #[inline(always)]
     fn put_back_char(&mut self, c: char) {
-        self.stream.seek(SeekFrom::Current(- (c.len_utf8() as i64))).unwrap();
+        self.stream
+            .seek(SeekFrom::Current(-(c.len_utf8() as i64)))
+            .unwrap();
     }
 }
 
@@ -315,8 +319,7 @@ impl Write for HttpWriteStream {
             let mut response = response.lock().unwrap();
 
             let bytes = bytes::Bytes::copy_from_slice(&self.buffer);
-	    let mut response_ = hyper::Response::builder()
+            let mut response_ = hyper::Response::builder().status(self.status_code);
-	        .status(self.status_code);
             *response_.headers_mut().unwrap() = self.headers.clone();
             *response = Some(response_.body(http_body_util::Full::new(bytes)).unwrap());
         }
@@ -510,7 +513,9 @@ impl Stream {
     #[inline]
     pub fn from_owned_string(string: String, arena: &mut Arena) -> Stream {
         Stream::Byte(arena_alloc!(
-            StreamLayout::new(CharReader::new(ByteStream(Cursor::new(string.into_bytes())))),
+            StreamLayout::new(CharReader::new(ByteStream(Cursor::new(
+                string.into_bytes()
+            )))),
             arena
         ))
     }
@@ -732,10 +737,10 @@ impl CharRead for Stream {
                 ErrorKind::PermissionDenied,
                 StreamError::ReadFromOutputStream,
             ))),
-            Stream::OutputFile(_) |
+            Stream::OutputFile(_)
-            Stream::StandardError(_) |
+            | Stream::StandardError(_)
-            Stream::StandardOutput(_) |
+            | Stream::StandardOutput(_)
-            Stream::Null(_) => Some(Err(std::io::Error::new(
+            | Stream::Null(_) => Some(Err(std::io::Error::new(
                 ErrorKind::PermissionDenied,
                 StreamError::ReadFromOutputStream,
             ))),
@@ -758,10 +763,10 @@ impl CharRead for Stream {
                 ErrorKind::PermissionDenied,
                 StreamError::ReadFromOutputStream,
             ))),
-            Stream::OutputFile(_) |
+            Stream::OutputFile(_)
-            Stream::StandardError(_) |
+            | Stream::StandardError(_)
-            Stream::StandardOutput(_) |
+            | Stream::StandardOutput(_)
-            Stream::Null(_) => Some(Err(std::io::Error::new(
+            | Stream::Null(_) => Some(Err(std::io::Error::new(
                 ErrorKind::PermissionDenied,
                 StreamError::ReadFromOutputStream,
             ))),
@@ -781,10 +786,10 @@ impl CharRead for Stream {
             Stream::Byte(cursor) => cursor.put_back_char(c),
             #[cfg(feature = "http")]
             Stream::HttpWrite(_) => {}
-            Stream::OutputFile(_) |
+            Stream::OutputFile(_)
-            Stream::StandardError(_) |
+            | Stream::StandardError(_)
-            Stream::StandardOutput(_) |
+            | Stream::StandardOutput(_)
-            Stream::Null(_) => {}
+            | Stream::Null(_) => {}
         }
     }
 
@@ -801,10 +806,10 @@ impl CharRead for Stream {
             Stream::Byte(ref mut cursor) => cursor.consume(nread),
             #[cfg(feature = "http")]
             Stream::HttpWrite(_) => {}
-            Stream::OutputFile(_) |
+            Stream::OutputFile(_)
-            Stream::StandardError(_) |
+            | Stream::StandardError(_)
-            Stream::StandardOutput(_) |
+            | Stream::StandardOutput(_)
-            Stream::Null(_) => {}
+            | Stream::Null(_) => {}
         }
     }
 }
@@ -857,10 +862,10 @@ impl Write for Stream {
                 ErrorKind::PermissionDenied,
                 StreamError::WriteToInputStream,
             )),
-            Stream::StaticString(_) |
+            Stream::StaticString(_)
-            Stream::Readline(_) |
+            | Stream::Readline(_)
-            Stream::InputFile(..) |
+            | Stream::InputFile(..)
-            Stream::Null(_) => Err(std::io::Error::new(
+            | Stream::Null(_) => Err(std::io::Error::new(
                 ErrorKind::PermissionDenied,
                 StreamError::WriteToInputStream,
             )),
@@ -883,10 +888,10 @@ impl Write for Stream {
                 ErrorKind::PermissionDenied,
                 StreamError::FlushToInputStream,
             )),
-            Stream::StaticString(_) |
+            Stream::StaticString(_)
-            Stream::Readline(_) |
+            | Stream::Readline(_)
-            Stream::InputFile(_) |
+            | Stream::InputFile(_)
-            Stream::Null(_) => Err(std::io::Error::new(
+            | Stream::Null(_) => Err(std::io::Error::new(
                 ErrorKind::PermissionDenied,
                 StreamError::FlushToInputStream,
             )),
@@ -898,8 +903,10 @@ impl Write for Stream {
 enum StreamError {
     PeekByteFailed,
     PeekByteFromNonPeekableStream,
-    #[allow(unused)] PeekCharFailed,
+    #[allow(unused)]
-    #[allow(unused)] PeekCharFromNonPeekableStream,
+    PeekCharFailed,
+    #[allow(unused)]
+    PeekCharFromNonPeekableStream,
     ReadFromOutputStream,
     WriteToInputStream,
     FlushToInputStream,
@@ -958,7 +965,11 @@ impl PartialEq for Stream {
 
 impl Eq for Stream {}
 
-fn cursor_position<T>(past_end_of_stream: &mut bool, cursor: &Cursor<T>, cursor_len: u64) -> AtEndOfStream {
+fn cursor_position<T>(
+    past_end_of_stream: &mut bool,
+    cursor: &Cursor<T>,
+    cursor_len: u64,
+) -> AtEndOfStream {
     let position = cursor.position();
 
     let at_end_of_stream = match position.cmp(&cursor_len) {
@@ -984,17 +995,10 @@ impl Stream {
             Stream::StaticString(string_stream_layout) => {
                 Some(string_stream_layout.stream.stream.position())
             }
-            Stream::InputFile(file_stream) => {
+            Stream::InputFile(file_stream) => file_stream.position(),
-                file_stream.position()
-            }
             #[cfg(feature = "tls")]
-            Stream::NamedTls(..) => {
+            Stream::NamedTls(..) => Some(0),
-                Some(0)
+            Stream::NamedTcp(..) | Stream::Readline(..) => Some(0),
-            }
-            Stream::NamedTcp(..) 
-            | Stream::Readline(..) => {
-                Some(0)
-            }
             _ => None,
         };
 
@@ -1011,7 +1015,11 @@ impl Stream {
                     ..
                 } = &mut **stream_layout;
 
-                stream.get_mut().file.seek(SeekFrom::Start(position)).unwrap();
+                stream
+                    .get_mut()
+                    .file
+                    .seek(SeekFrom::Start(position))
+                    .unwrap();
                 stream.reset_buffer(); // flush the internal buffer.
 
                 if let Ok(metadata) = stream.get_ref().file.metadata() {
@@ -1127,9 +1135,7 @@ impl Stream {
                     }
                 }
             }
-            _ => {
+            _ => AtEndOfStream::Not,
-                AtEndOfStream::Not
-            }
         }
     }
 
@@ -1160,7 +1166,9 @@ impl Stream {
             Stream::OutputFile(file) if file.is_append => atom!("append"),
             #[cfg(feature = "http")]
             Stream::HttpWrite(_) => atom!("write"),
-            Stream::OutputFile(_) | Stream::StandardError(_) | Stream::StandardOutput(_) => atom!("write"),
+            Stream::OutputFile(_) | Stream::StandardError(_) | Stream::StandardOutput(_) => {
+                atom!("write")
+            }
             Stream::Null(_) => atom!(""),
         }
     }
@@ -1182,11 +1190,7 @@ impl Stream {
     }
 
     #[inline]
-    pub(crate) fn from_tcp_stream(
+    pub(crate) fn from_tcp_stream(address: Atom, tcp_stream: TcpStream, arena: &mut Arena) -> Self {
-        address: Atom,
-        tcp_stream: TcpStream,
-        arena: &mut Arena,
-    ) -> Self {
         tcp_stream.set_read_timeout(None).unwrap();
         tcp_stream.set_write_timeout(None).unwrap();
 
@@ -1282,11 +1286,9 @@ impl Stream {
         match stream {
             Stream::NamedTcp(ref mut tcp_stream) => {
                 tcp_stream.inner_mut().tcp_stream.shutdown(Shutdown::Both)
-            },
-            #[cfg(feature = "tls")]
-            Stream::NamedTls(ref mut tls_stream) => {
-                tls_stream.inner_mut().tls_stream.shutdown()
             }
+            #[cfg(feature = "tls")]
+            Stream::NamedTls(ref mut tls_stream) => tls_stream.inner_mut().tls_stream.shutdown(),
             #[cfg(feature = "http")]
             Stream::HttpRead(ref mut http_stream) => {
                 unsafe {
@@ -1323,7 +1325,7 @@ impl Stream {
 
                 Ok(())
             }
-            _ => Ok(())
+            _ => Ok(()),
         }
     }
 
@@ -1381,7 +1383,12 @@ impl Stream {
                     return true;
                 }
                 Stream::InputFile(ref mut file_stream) => {
-                    file_stream.stream.get_mut().file.seek(SeekFrom::Start(0)).unwrap();
+                    file_stream
+                        .stream
+                        .get_mut()
+                        .file
+                        .seek(SeekFrom::Start(0))
+                        .unwrap();
                     return true;
                 }
                 Stream::Readline(ref mut readline_stream) => {
@@ -1410,17 +1417,13 @@ impl Stream {
                     _ => Err(std::io::Error::new(ErrorKind::UnexpectedEof, "end of file")),
                 }
             }
-            Stream::InputFile(ref mut file) => {
+            Stream::InputFile(ref mut file) => match file.peek_byte() {
-                match file.peek_byte() {
+                Some(result) => Ok(result?),
-                    Some(result) => {
-                        Ok(result?)
-                    }
                 _ => Err(std::io::Error::new(
                     ErrorKind::UnexpectedEof,
                     StreamError::PeekByteFailed,
                 )),
-                }
+            },
-            }
             Stream::Readline(ref mut stream) => stream.stream.peek_byte(),
             Stream::NamedTcp(ref mut stream) => {
                 let mut b = [0u8; 1];
@@ -1663,7 +1666,10 @@ impl MachineState {
         }
     }
 
-    pub(crate) fn open_parsing_stream(&mut self, mut stream: Stream) -> Result<Stream, ParserError> {
+    pub(crate) fn open_parsing_stream(
+        &mut self,
+        mut stream: Stream,
+    ) -> Result<Stream, ParserError> {
         match stream.peek_char() {
             None => Ok(stream), // empty stream is handled gracefully by Lexer::eof
             Some(Err(e)) => Err(ParserError::IO(e)),
@@ -1847,7 +1853,7 @@ impl MachineState {
             }
         };
 
-        let file = match open_options.open(file_spec.as_str()) {
+        let file = match open_options.open(&*file_spec.as_str()) {
             Ok(file) => file,
             Err(err) => {
                 match err.kind() {
@@ -1855,15 +1861,18 @@ impl MachineState {
                         // 8.11.5.3j)
                         let stub = functor_stub(atom!("open"), 4);
 
-                        let err = self.existence_error(
+                        let err =
-                            ExistenceError::SourceSink(self[temp_v!(1)]),
+                            self.existence_error(ExistenceError::SourceSink(self[temp_v!(1)]));
-                        );
 
                         return Err(self.error_form(err, stub));
                     }
                     ErrorKind::PermissionDenied => {
                         // 8.11.5.3k)
-                        return Err(self.open_permission_error(self.registers[1], atom!("open"), 4));
+                        return Err(self.open_permission_error(
+                            self.registers[1],
+                            atom!("open"),
+                            4,
+                        ));
                     }
                     _ => {
                         let stub = functor_stub(atom!("open"), 4);

src/machine/term_stream.rs

@@ -1,8 +1,8 @@
 use crate::forms::*;
-use crate::machine::*;
 use crate::machine::load_state::*;
 use crate::machine::loader::*;
 use crate::machine::machine_errors::*;
+use crate::machine::*;
 use crate::parser::ast::*;
 use crate::parser::parser::*;
 use crate::read::devour_whitespace;
@@ -45,7 +45,10 @@ impl<'a> BootstrappingTermStream<'a> {
         listing_src: ListingSource,
     ) -> Self {
         let parser = Parser::new(stream, machine_st);
-        Self { parser, listing_src }
+        Self {
+            parser,
+            listing_src,
+        }
     }
 }
 
@@ -122,8 +125,7 @@ impl TermStream for LiveTermStream {
     }
 }
 
-pub struct InlineTermStream {
+pub struct InlineTermStream {}
-}
 
 impl TermStream for InlineTermStream {
     fn next(&mut self, _: &CompositeOpDir) -> Result<Term, CompilationError> {
@@ -138,4 +140,3 @@ impl TermStream for InlineTermStream {
         &ListingSource::User
     }
 }
-

src/machine/unify.rs

@@ -1,9 +1,9 @@
 use crate::arena::*;
 use crate::forms::*;
 use crate::heap_iter::stackful_preorder_iter;
-use crate::machine::*;
 use crate::machine::machine_state::*;
 use crate::machine::partial_string::*;
+use crate::machine::*;
 use crate::types::*;
 
 use std::cmp::Ordering;
@@ -190,8 +190,8 @@ pub(crate) trait Unifier: DerefMut<Target = MachineState> {
                     machine_st.pdl.push(pstr_iter1.focus);
                 }
             }
-            continuable @ PStrCmpResult::FirstIterContinuable(iteratee) |
+            continuable @ PStrCmpResult::FirstIterContinuable(iteratee)
-            continuable @ PStrCmpResult::SecondIterContinuable(iteratee) => {
+            | continuable @ PStrCmpResult::SecondIterContinuable(iteratee) => {
                 if continuable.is_second_iter() {
                     std::mem::swap(&mut pstr_iter1, &mut pstr_iter2);
                 }
@@ -439,10 +439,8 @@ pub(crate) trait Unifier: DerefMut<Target = MachineState> {
     }
 
     fn unify_big_num<N>(&mut self, n1: TypedArenaPtr<N>, value: HeapCellValue)
-        where N: PartialEq<Rational>
+    where
-               + PartialEq<Integer>
+        N: PartialEq<Rational> + PartialEq<Integer> + PartialEq<i64> + ArenaAllocated,
-               + PartialEq<i64>
-               + ArenaAllocated
     {
         if let Some(r) = value.as_var() {
             Self::bind(self, r, typed_arena_ptr_as_cell!(n1));

src/macros.rs

@@ -88,7 +88,7 @@ macro_rules! cell_as_atom_cell {
 macro_rules! cell_as_f64_ptr {
     ($cell:expr) => {{
         let offset = $cell.get_value() as usize;
-        F64Ptr::from_offset(offset)
+        F64Ptr::from_offset(F64Offset::new(offset))
     }};
 }
 
@@ -236,12 +236,14 @@ macro_rules! cell_as_stream {
 }
 
 macro_rules! cell_as_load_state_payload {
-    ($cell:expr) => { unsafe {
+    ($cell:expr) => {
+        unsafe {
             let ptr = cell_as_untyped_arena_ptr!($cell);
             let ptr = std::mem::transmute::<_, *mut LiveLoadState>(ptr.payload_offset());
 
             TypedArenaPtr::new(ptr)
-    }};
+        }
+    };
 }
 
 macro_rules! match_untyped_arena_ptr_pat_body {
@@ -258,13 +260,15 @@ macro_rules! match_untyped_arena_ptr_pat_body {
         $code
     }};
     ($ptr:ident, OssifiedOpDir, $n:ident, $code:expr) => {{
-        let payload_ptr = unsafe { std::mem::transmute::<_, *mut OssifiedOpDir>($ptr.payload_offset()) };
+        let payload_ptr =
+            unsafe { std::mem::transmute::<_, *mut OssifiedOpDir>($ptr.payload_offset()) };
         let $n = TypedArenaPtr::new(payload_ptr);
         #[allow(unused_braces)]
         $code
     }};
     ($ptr:ident, LiveLoadState, $n:ident, $code:expr) => {{
-        let payload_ptr = unsafe { std::mem::transmute::<_, *mut LiveLoadState>($ptr.payload_offset()) };
+        let payload_ptr =
+            unsafe { std::mem::transmute::<_, *mut LiveLoadState>($ptr.payload_offset()) };
         let $n = TypedArenaPtr::new(payload_ptr);
         #[allow(unused_braces)]
         $code
@@ -275,21 +279,24 @@ macro_rules! match_untyped_arena_ptr_pat_body {
         $code
     }};
     ($ptr:ident, TcpListener, $listener:ident, $code:expr) => {{
-        let payload_ptr = unsafe { std::mem::transmute::<_, *mut TcpListener>($ptr.payload_offset()) };
+        let payload_ptr =
+            unsafe { std::mem::transmute::<_, *mut TcpListener>($ptr.payload_offset()) };
         #[allow(unused_mut)]
         let mut $listener = TypedArenaPtr::new(payload_ptr);
         #[allow(unused_braces)]
         $code
     }};
     ($ptr:ident, HttpListener, $listener:ident, $code:expr) => {{
-        let payload_ptr = unsafe { std::mem::transmute::<_, *mut HttpListener>($ptr.payload_offset()) };
+        let payload_ptr =
+            unsafe { std::mem::transmute::<_, *mut HttpListener>($ptr.payload_offset()) };
         #[allow(unused_mut)]
         let mut $listener = TypedArenaPtr::new(payload_ptr);
         #[allow(unused_braces)]
         $code
     }};
     ($ptr:ident, HttpResponse, $listener:ident, $code:expr) => {{
-        let payload_ptr = unsafe { std::mem::transmute::<_, *mut HttpResponse>($ptr.payload_offset()) };
+        let payload_ptr =
+            unsafe { std::mem::transmute::<_, *mut HttpResponse>($ptr.payload_offset()) };
         #[allow(unused_mut)]
         let mut $listener = TypedArenaPtr::new(payload_ptr);
         #[allow(unused_braces)]
@@ -297,7 +304,8 @@ macro_rules! match_untyped_arena_ptr_pat_body {
     }};
     ($ptr:ident, IndexPtr, $ip:ident, $code:expr) => {{
         #[allow(unused_mut)]
-        let mut $ip = TypedArenaPtr::new(unsafe { std::mem::transmute::<_, *mut IndexPtr>($ptr.get_ptr()) });
+        let mut $ip =
+            TypedArenaPtr::new(unsafe { std::mem::transmute::<_, *mut IndexPtr>($ptr.get_ptr()) });
         #[allow(unused_braces)]
         $code
     }};
@@ -323,10 +331,10 @@ macro_rules! match_untyped_arena_ptr_pat {
             | ArenaHeaderTag::StandardErrorStream
     };
     (IndexPtr) => {
-        ArenaHeaderTag::IndexPtrUndefined |
+        ArenaHeaderTag::IndexPtrUndefined
-        ArenaHeaderTag::IndexPtrDynamicUndefined |
+            | ArenaHeaderTag::IndexPtrDynamicUndefined
-        ArenaHeaderTag::IndexPtrDynamicIndex |
+            | ArenaHeaderTag::IndexPtrDynamicIndex
-        ArenaHeaderTag::IndexPtrIndex
+            | ArenaHeaderTag::IndexPtrIndex
     };
     ($tag:ident) => {
         ArenaHeaderTag::$tag
@@ -347,71 +355,71 @@ macro_rules! match_untyped_arena_ptr {
 }
 
 macro_rules! read_heap_cell_pat_body {
-    ($cell:ident, Cons, $n:ident, $code:expr) => ({
+    ($cell:ident, Cons, $n:ident, $code:expr) => {{
         let $n = cell_as_untyped_arena_ptr!($cell);
         #[allow(unused_braces)]
         $code
-    });
+    }};
-    ($cell:ident, F64, $n:ident, $code:expr) => ({
+    ($cell:ident, F64, $n:ident, $code:expr) => {{
         let $n = cell_as_f64_ptr!($cell);
         #[allow(unused_braces)]
         $code
-    });
+    }};
-    ($cell:ident, Atom, ($name:ident, $arity:ident), $code:expr) => ({
+    ($cell:ident, Atom, ($name:ident, $arity:ident), $code:expr) => {{
         let ($name, $arity) = cell_as_atom_cell!($cell).get_name_and_arity();
         #[allow(unused_braces)]
         $code
-    });
+    }};
-    ($cell:ident, PStr, $atom:ident, $code:expr) => ({
+    ($cell:ident, PStr, $atom:ident, $code:expr) => {{
         let $atom = cell_as_atom!($cell);
         #[allow(unused_braces)]
         $code
-    });
+    }};
-    ($cell:ident, CStr, $atom:ident, $code:expr) => ({
+    ($cell:ident, CStr, $atom:ident, $code:expr) => {{
         let $atom = cell_as_atom!($cell);
         #[allow(unused_braces)]
         $code
-    });
+    }};
-    ($cell:ident, CStr | PStr, $atom:ident, $code:expr) => ({
+    ($cell:ident, CStr | PStr, $atom:ident, $code:expr) => {{
         let $atom = cell_as_atom!($cell);
         #[allow(unused_braces)]
         $code
-    });
+    }};
-    ($cell:ident, PStr | CStr, $atom:ident, $code:expr) => ({
+    ($cell:ident, PStr | CStr, $atom:ident, $code:expr) => {{
         let $atom = cell_as_atom!($cell);
         #[allow(unused_braces)]
         $code
-    });
+    }};
-    ($cell:ident, Fixnum, $value:ident, $code:expr) => ({
+    ($cell:ident, Fixnum, $value:ident, $code:expr) => {{
         let $value = Fixnum::from_bytes($cell.into_bytes());
         #[allow(unused_braces)]
         $code
-    });
+    }};
-    ($cell:ident, CutPoint, $value:ident, $code:expr) => ({
+    ($cell:ident, CutPoint, $value:ident, $code:expr) => {{
         let $value = Fixnum::from_bytes($cell.into_bytes());
         #[allow(unused_braces)]
         $code
-    });
+    }};
-    ($cell:ident, Fixnum | CutPoint, $value:ident, $code:expr) => ({
+    ($cell:ident, Fixnum | CutPoint, $value:ident, $code:expr) => {{
         let $value = Fixnum::from_bytes($cell.into_bytes());
         #[allow(unused_braces)]
         $code
-    });
+    }};
-    ($cell:ident, CutPoint | Fixnum, $value:ident, $code:expr) => ({
+    ($cell:ident, CutPoint | Fixnum, $value:ident, $code:expr) => {{
         let $value = Fixnum::from_bytes($cell.into_bytes());
         #[allow(unused_braces)]
         $code
-    });
+    }};
-    ($cell:ident, Char, $value:ident, $code:expr) => ({
+    ($cell:ident, Char, $value:ident, $code:expr) => {{
         let $value = unsafe { char::from_u32_unchecked($cell.get_value() as u32) };
         #[allow(unused_braces)]
         $code
-    });
+    }};
-    ($cell:ident, $($tags:tt)|+, $value:ident, $code:expr) => ({
+    ($cell:ident, $($tags:tt)|+, $value:ident, $code:expr) => {{
         let $value = $cell.get_value() as usize;
         #[allow(unused_braces)]
         $code
-    });
+    }};
 }
 
 macro_rules! read_heap_cell_pat {
@@ -596,7 +604,9 @@ macro_rules! index_store {
         IndexStore {
             code_dir: $code_dir,
             extensible_predicates: ExtensiblePredicates::with_hasher(FxBuildHasher::default()),
-            local_extensible_predicates: LocalExtensiblePredicates::with_hasher(FxBuildHasher::default()),
+            local_extensible_predicates: LocalExtensiblePredicates::with_hasher(
+                FxBuildHasher::default(),
+            ),
             global_variables: GlobalVarDir::with_hasher(FxBuildHasher::default()),
             goal_expansion_indices: GoalExpansionIndices::with_hasher(FxBuildHasher::default()),
             meta_predicates: MetaPredicateDir::with_hasher(FxBuildHasher::default()),

src/parser/ast.rs

@@ -10,6 +10,7 @@ use std::hash::{Hash, Hasher};
 use std::io::{Error as IOError, ErrorKind};
 use std::ops::{Deref, Neg};
 use std::rc::Rc;
+use std::sync::Arc;
 use std::vec::Vec;
 
 use crate::parser::dashu::{Integer, Rational};
@@ -258,7 +259,8 @@ impl GenContext {
 pub struct OpDesc {
     prec: B11,
     spec: B8,
-    #[allow(unused)] padding: B13,
+    #[allow(unused)]
+    padding: B13,
 }
 
 impl OpDesc {
@@ -417,13 +419,13 @@ pub enum ParserError {
 impl ParserError {
     pub fn line_and_col_num(&self) -> Option<(usize, usize)> {
         match self {
-            &ParserError::BackQuotedString(line_num, col_num) |
+            &ParserError::BackQuotedString(line_num, col_num)
-            &ParserError::IncompleteReduction(line_num, col_num) |
+            | &ParserError::IncompleteReduction(line_num, col_num)
-            &ParserError::MissingQuote(line_num, col_num) |
+            | &ParserError::MissingQuote(line_num, col_num)
-            &ParserError::NonPrologChar(line_num, col_num) |
+            | &ParserError::NonPrologChar(line_num, col_num)
-            &ParserError::ParseBigInt(line_num, col_num) |
+            | &ParserError::ParseBigInt(line_num, col_num)
-            &ParserError::UnexpectedChar(_, line_num, col_num) |
+            | &ParserError::UnexpectedChar(_, line_num, col_num)
-            &ParserError::Utf8Error(line_num, col_num) => Some((line_num, col_num)),
+            | &ParserError::Utf8Error(line_num, col_num) => Some((line_num, col_num)),
             _ => None,
         }
     }
@@ -432,8 +434,12 @@ impl ParserError {
         match self {
             ParserError::BackQuotedString(..) => atom!("back_quoted_string"),
             ParserError::IncompleteReduction(..) => atom!("incomplete_reduction"),
-            ParserError::InvalidSingleQuotedCharacter(..) => atom!("invalid_single_quoted_character"),
+            ParserError::InvalidSingleQuotedCharacter(..) => {
-            ParserError::IO(e) if e.kind() == ErrorKind::UnexpectedEof => atom!("unexpected_end_of_file"),
+                atom!("invalid_single_quoted_character")
+            }
+            ParserError::IO(e) if e.kind() == ErrorKind::UnexpectedEof => {
+                atom!("unexpected_end_of_file")
+            }
             ParserError::IO(_) => atom!("input_output_error"),
             ParserError::LexicalError(_) => atom!("lexical_error"),
             ParserError::MissingQuote(..) => atom!("missing_quote"),
@@ -522,9 +528,12 @@ pub enum Fixity {
 #[derive(Copy, Clone, Debug, Hash, PartialEq, Eq)]
 pub struct Fixnum {
     num: B56,
-    #[allow(unused)] f: bool,
+    #[allow(unused)]
-    #[allow(unused)] m: bool,
+    f: bool,
-    #[allow(unused)] tag: B6,
+    #[allow(unused)]
+    m: bool,
+    #[allow(unused)]
+    tag: B6,
 }
 
 impl Fixnum {
@@ -623,7 +632,7 @@ impl fmt::Display for Literal {
 }
 
 impl Literal {
-    pub fn to_atom(&self, atom_tbl: &mut AtomTable) -> Option<Atom> {
+    pub fn to_atom(&self, atom_tbl: &Arc<AtomTable>) -> Option<Atom> {
         match self {
             Literal::Atom(atom) => Some(atom.defrock_brackets(atom_tbl)),
             _ => None,
@@ -631,7 +640,6 @@ impl Literal {
     }
 }
 
-
 #[derive(Debug, Clone, PartialEq, Eq)]
 pub struct VarPtr(Rc<RefCell<Var>>);
 

src/parser/char_reader.rs

@@ -78,7 +78,7 @@ pub trait CharRead {
                 self.consume(c.len_utf8());
                 Some(Ok(c))
             }
-            result => result
+            result => result,
         }
     }
 
@@ -161,9 +161,7 @@ impl<R: Read> CharRead for CharReader<R> {
 
                         return Some(Ok(c));
                     }
-                    Err(e) => {
+                    Err(e) => e,
-                        e
-                    }
                 };
 
                 if buf.len() - e.valid_up_to() >= 4 {
@@ -192,8 +190,10 @@ impl<R: Read> CharRead for CharReader<R> {
                     // the buffer, it will be returned on the next
                     // loop.
 
-                    return Some(Err(io::Error::new(io::ErrorKind::InvalidData,
+                    return Some(Err(io::Error::new(
-                                                   BadUtf8Error { bytes: badbytes })));
+                        io::ErrorKind::InvalidData,
+                        BadUtf8Error { bytes: badbytes },
+                    )));
                 } else {
                     if self.pos >= self.buf.len() {
                         return None;
@@ -208,8 +208,10 @@ impl<R: Read> CharRead for CharReader<R> {
                             Err(e) => {
                                 let badbytes = self.buf[self.pos..e.valid_up_to()].to_vec();
 
-                                Some(Err(io::Error::new(io::ErrorKind::InvalidData,
+                                Some(Err(io::Error::new(
-                                                        BadUtf8Error { bytes: badbytes })))
+                                    io::ErrorKind::InvalidData,
+                                    BadUtf8Error { bytes: badbytes },
+                                )))
                             }
                         };
                     } else {
@@ -311,7 +313,10 @@ impl<R: Read> Read for CharReader<R> {
         }
 
         if !buf.is_empty() {
-            Err(io::Error::new(ErrorKind::UnexpectedEof, "failed to fill whole buffer"))
+            Err(io::Error::new(
+                ErrorKind::UnexpectedEof,
+                "failed to fill whole buffer",
+            ))
         } else {
             Ok(())
         }
@@ -364,12 +369,14 @@ where
     fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
         fmt.debug_struct("CharReader")
             .field("reader", &self.inner)
-            .field("buf", &format_args!("{}/{}", self.buf.capacity() - self.pos, self.buf.len()))
+            .field(
+                "buf",
+                &format_args!("{}/{}", self.buf.capacity() - self.pos, self.buf.len()),
+            )
             .finish()
     }
 }
 
-
 #[cfg(test)]
 mod tests {
     use crate::parser::char_reader::*;

src/parser/lexer.rs

@@ -86,14 +86,14 @@ impl<'a, R: CharRead> Lexer<'a, R> {
     pub fn lookahead_char(&mut self) -> Result<char, ParserError> {
         match self.reader.peek_char() {
             Some(Ok(c)) => Ok(c),
-            _ => Err(ParserError::unexpected_eof())
+            _ => Err(ParserError::unexpected_eof()),
         }
     }
 
     pub fn read_char(&mut self) -> Result<char, ParserError> {
         match self.reader.read_char() {
             Some(Ok(c)) => Ok(c),
-            _ => Err(ParserError::unexpected_eof())
+            _ => Err(ParserError::unexpected_eof()),
         }
     }
 
@@ -168,13 +168,15 @@ impl<'a, R: CharRead> Lexer<'a, R> {
 
             match comment_loop() {
                 Err(e) if e.is_unexpected_eof() => {
-                    return Err(ParserError::IncompleteReduction(self.line_num, self.col_num));
+                    return Err(ParserError::IncompleteReduction(
+                        self.line_num,
+                        self.col_num,
+                    ));
                 }
                 Err(e) => {
                     return Err(e);
                 }
-                Ok(_) => {
+                Ok(_) => {}
-                }
             }
 
             if prolog_char!(c) {
@@ -362,7 +364,10 @@ impl<'a, R: CharRead> Lexer<'a, R> {
         if hexadecimal_digit_char!(c) {
             self.escape_sequence_to_char(|c| hexadecimal_digit_char!(c), 16)
         } else {
-            Err(ParserError::IncompleteReduction(self.line_num, self.col_num))
+            Err(ParserError::IncompleteReduction(
+                self.line_num,
+                self.col_num,
+            ))
         }
     }
 
@@ -395,7 +400,10 @@ impl<'a, R: CharRead> Lexer<'a, R> {
                 },
             )
         } else {
-            Err(ParserError::IncompleteReduction(self.line_num, self.col_num))
+            Err(ParserError::IncompleteReduction(
+                self.line_num,
+                self.col_num,
+            ))
         }
     }
 
@@ -463,9 +471,12 @@ impl<'a, R: CharRead> Lexer<'a, R> {
                 .map(|n| Token::Literal(fixnum!(Literal, n, &mut self.machine_st.arena)))
                 .or_else(|_| {
                     Integer::from_str_radix(&token, 16)
-                        .map(|n| Token::Literal(Literal::Integer(
+                        .map(|n| {
-                            arena_alloc!(n, &mut self.machine_st.arena)
+                            Token::Literal(Literal::Integer(arena_alloc!(
+                                n,
+                                &mut self.machine_st.arena
                             )))
+                        })
                         .map_err(|_| ParserError::ParseBigInt(self.line_num, self.col_num))
                 })
         } else {
@@ -495,9 +506,12 @@ impl<'a, R: CharRead> Lexer<'a, R> {
                 .map(|n| Token::Literal(fixnum!(Literal, n, &mut self.machine_st.arena)))
                 .or_else(|_| {
                     Integer::from_str_radix(&token, 8)
-                        .map(|n| Token::Literal(Literal::Integer(
+                        .map(|n| {
-                            arena_alloc!(n, &mut self.machine_st.arena)
+                            Token::Literal(Literal::Integer(arena_alloc!(
+                                n,
+                                &mut self.machine_st.arena
                             )))
+                        })
                         .map_err(|_| ParserError::ParseBigInt(self.line_num, self.col_num))
                 })
         } else {
@@ -527,9 +541,12 @@ impl<'a, R: CharRead> Lexer<'a, R> {
                 .map(|n| Token::Literal(fixnum!(Literal, n, &mut self.machine_st.arena)))
                 .or_else(|_| {
                     Integer::from_str_radix(&token, 2)
-                        .map(|n| Token::Literal(Literal::Integer(
+                        .map(|n| {
-                            arena_alloc!(n, &mut self.machine_st.arena)
+                            Token::Literal(Literal::Integer(arena_alloc!(
+                                n,
+                                &mut self.machine_st.arena
                             )))
+                        })
                         .map_err(|_| ParserError::ParseBigInt(self.line_num, self.col_num))
                 })
         } else {
@@ -620,16 +637,20 @@ impl<'a, R: CharRead> Lexer<'a, R> {
         if token.as_str() == "[]" {
             Ok(Token::Literal(Literal::Atom(atom!("[]"))))
         } else {
-            Ok(Token::Literal(Literal::Atom(
+            Ok(Token::Literal(Literal::Atom(AtomTable::build_with(
-                self.machine_st.atom_tbl.build_with(&token),
+                &self.machine_st.atom_tbl,
-            )))
+                &token,
+            ))))
         }
     }
 
     fn vacate_with_float(&mut self, mut token: String) -> Result<Token, ParserError> {
         self.return_char(token.pop().unwrap());
         let n = parse_lossy::<f64, _>(token.as_bytes())?;
-        Ok(Token::Literal(Literal::from(float_alloc!(n, self.machine_st.arena))))
+        Ok(Token::Literal(Literal::from(float_alloc!(
+            n,
+            self.machine_st.arena
+        ))))
     }
 
     fn skip_underscore_in_number(&mut self) -> Result<char, ParserError> {
@@ -675,7 +696,10 @@ impl<'a, R: CharRead> Lexer<'a, R> {
                         token
                             .parse::<Integer>()
                             .map(|n| {
-                                Token::Literal(Literal::Integer(arena_alloc!(n, &mut self.machine_st.arena)))
+                                Token::Literal(Literal::Integer(arena_alloc!(
+                                    n,
+                                    &mut self.machine_st.arena
+                                )))
                             })
                             .map_err(|_| ParserError::ParseBigInt(self.line_num, self.col_num))
                     })
@@ -740,17 +764,19 @@ impl<'a, R: CharRead> Lexer<'a, R> {
                         }
 
                         let n = parse_lossy::<f64, _>(token.as_bytes())?;
-                        Ok(Token::Literal(Literal::from(
+                        Ok(Token::Literal(Literal::from(float_alloc!(
-                            float_alloc!(n, self.machine_st.arena)
+                            n,
-                        )))
+                            self.machine_st.arena
+                        ))))
                     } else {
                         return Ok(self.vacate_with_float(token)?);
                     }
                 } else {
                     let n = parse_lossy::<f64, _>(token.as_bytes())?;
-                    Ok(Token::Literal(Literal::from(
+                    Ok(Token::Literal(Literal::from(float_alloc!(
-                        float_alloc!(n, self.machine_st.arena)
+                        n,
-                    )))
+                        self.machine_st.arena
+                    ))))
                 }
             } else {
                 self.return_char('.');
@@ -761,7 +787,10 @@ impl<'a, R: CharRead> Lexer<'a, R> {
                         token
                             .parse::<Integer>()
                             .map(|n| {
-                                Token::Literal(Literal::Integer(arena_alloc!(n, &mut self.machine_st.arena)))
+                                Token::Literal(Literal::Integer(arena_alloc!(
+                                    n,
+                                    &mut self.machine_st.arena
+                                )))
                             })
                             .map_err(|_| ParserError::ParseBigInt(self.line_num, self.col_num))
                     })
@@ -772,7 +801,9 @@ impl<'a, R: CharRead> Lexer<'a, R> {
                     self.hexadecimal_constant(c).or_else(|e| {
                         if let ParserError::ParseBigInt(..) = e {
                             i64::from_str_radix(&token, 10)
-                                .map(|n| Token::Literal(fixnum!(Literal, n, &mut self.machine_st.arena)))
+                                .map(|n| {
+                                    Token::Literal(fixnum!(Literal, n, &mut self.machine_st.arena))
+                                })
                                 .or_else(|_| {
                                     token
                                         .parse::<Integer>()
@@ -794,7 +825,9 @@ impl<'a, R: CharRead> Lexer<'a, R> {
                     self.octal_constant(c).or_else(|e| {
                         if let ParserError::ParseBigInt(..) = e {
                             i64::from_str_radix(&token, 10)
-                                .map(|n| Token::Literal(fixnum!(Literal, n, &mut self.machine_st.arena)))
+                                .map(|n| {
+                                    Token::Literal(fixnum!(Literal, n, &mut self.machine_st.arena))
+                                })
                                 .or_else(|_| {
                                     token
                                         .parse::<Integer>()
@@ -816,7 +849,9 @@ impl<'a, R: CharRead> Lexer<'a, R> {
                     self.binary_constant(c).or_else(|e| {
                         if let ParserError::ParseBigInt(..) = e {
                             i64::from_str_radix(&token, 10)
-                                .map(|n| Token::Literal(fixnum!(Literal, n, &mut self.machine_st.arena)))
+                                .map(|n| {
+                                    Token::Literal(fixnum!(Literal, n, &mut self.machine_st.arena))
+                                })
                                 .or_else(|_| {
                                     token
                                         .parse::<Integer>()
@@ -856,15 +891,16 @@ impl<'a, R: CharRead> Lexer<'a, R> {
                         .map(|c| Token::Literal(Literal::Fixnum(Fixnum::build_with(c as i64))))
                         .or_else(|err| {
                             match err {
-                                ParserError::UnexpectedChar('\'', ..) => {
+                                ParserError::UnexpectedChar('\'', ..) => {}
-                                }
                                 err => return Err(err),
                             }
 
                             self.return_char(c);
 
                             i64::from_str_radix(&token, 10)
-                                .map(|n| Token::Literal(fixnum!(Literal, n, &mut self.machine_st.arena)))
+                                .map(|n| {
+                                    Token::Literal(fixnum!(Literal, n, &mut self.machine_st.arena))
+                                })
                                 .or_else(|_| {
                                     token
                                         .parse::<Integer>()
@@ -901,7 +937,10 @@ impl<'a, R: CharRead> Lexer<'a, R> {
                         token
                             .parse::<Integer>()
                             .map(|n| {
-                                Token::Literal(Literal::Integer(arena_alloc!(n, &mut self.machine_st.arena)))
+                                Token::Literal(Literal::Integer(arena_alloc!(
+                                    n,
+                                    &mut self.machine_st.arena
+                                )))
                             })
                             .map_err(|_| ParserError::ParseBigInt(self.line_num, self.col_num))
                     })
@@ -940,11 +979,12 @@ impl<'a, R: CharRead> Lexer<'a, R> {
 
     pub fn scan_for_layout(&mut self) -> Result<bool, ParserError> {
         match self.lookahead_char() {
-            Err(e) => {
+            Err(e) => Err(e),
-                Err(e)
-            }
             Ok(c) => {
-                let mut layout_info = LayoutInfo { inserted: false, more: true };
+                let mut layout_info = LayoutInfo {
+                    inserted: false,
+                    more: true,
+                };
                 let mut cr = Some(c);
 
                 loop {
@@ -1044,7 +1084,7 @@ impl<'a, R: CharRead> Lexer<'a, R> {
 
                 if c == '"' {
                     let s = self.char_code_list_token(c)?;
-                    let atom = self.machine_st.atom_tbl.build_with(&s);
+                    let atom = AtomTable::build_with(&self.machine_st.atom_tbl, &s);
 
                     return if let DoubleQuotes::Atom = self.machine_st.flags.double_quotes {
                         Ok(Token::Literal(Literal::Atom(atom)))
@@ -1054,7 +1094,7 @@ impl<'a, R: CharRead> Lexer<'a, R> {
                 }
 
                 if c == '\u{0}' {
-                    return Err(ParserError::unexpected_eof())
+                    return Err(ParserError::unexpected_eof());
                 }
 
                 self.name_token(c)

src/parser/macros.rs

@@ -7,13 +7,14 @@ macro_rules! char_class {
 #[macro_export]
 macro_rules! alpha_char {
     ($c: expr) => {
-        (!$c.is_numeric() &&
+        (!$c.is_numeric()
-         !$c.is_whitespace() &&
+            && !$c.is_whitespace()
-         !$c.is_control() &&
+            && !$c.is_control()
-         !$crate::graphic_token_char!($c) &&
+            && !$crate::graphic_token_char!($c)
-         !$crate::layout_char!($c) &&
+            && !$crate::layout_char!($c)
-         !$crate::meta_char!($c) &&
+            && !$crate::meta_char!($c)
-         !$crate::solo_char!($c)) || $c == '_'
+            && !$crate::solo_char!($c))
+            || $c == '_'
     };
 }
 

src/parser/parser.rs

@@ -7,7 +7,6 @@ use crate::parser::ast::*;
 use crate::parser::char_reader::*;
 use crate::parser::lexer::*;
 
-
 use std::cell::Cell;
 use std::mem;
 use std::ops::Neg;
@@ -108,7 +107,7 @@ pub(crate) fn as_partial_string(
                 tail_ref = tail;
             }
             Term::CompleteString(_, cstr) => {
-                string += cstr.as_str();
+                string += &*cstr.as_str();
                 tail = Term::Literal(Cell::default(), Literal::Atom(atom!("[]")));
                 break;
             }
@@ -120,26 +119,17 @@ pub(crate) fn as_partial_string(
     }
 
     match &tail {
-        Term::AnonVar | Term::Var(..) => {
+        Term::AnonVar | Term::Var(..) => Ok((string, Some(Box::new(tail)))),
-            Ok((string, Some(Box::new(tail))))
+        Term::Literal(_, Literal::Atom(atom!("[]"))) => Ok((string, None)),
-        }
-        Term::Literal(_, Literal::Atom(atom!("[]"))) => {
-            Ok((string, None))
-        }
         Term::Literal(_, Literal::String(tail)) => {
-            string += tail.as_str();
+            string += &*tail.as_str();
             Ok((string, None))
         }
-        _ => {
+        _ => Ok((string, Some(Box::new(tail)))),
-            Ok((string, Some(Box::new(tail))))
-        }
     }
 }
 
-pub fn get_op_desc(
+pub fn get_op_desc(name: Atom, op_dir: &CompositeOpDir) -> Option<CompositeOpDesc> {
-    name: Atom,
-    op_dir: &CompositeOpDir,
-) -> Option<CompositeOpDesc> {
     let mut op_desc = CompositeOpDesc {
         pre: 0,
         inf: 0,
@@ -295,17 +285,17 @@ fn read_tokens<R: CharRead>(lexer: &mut Lexer<R>) -> Result<Vec<Token>, ParserEr
     Ok(tokens)
 }
 
-fn atomize_term(atom_tbl: &mut AtomTable, term: &Term) -> Option<Atom> {
+fn atomize_term(atom_tbl: &AtomTable, term: &Term) -> Option<Atom> {
     match term {
         Term::Literal(_, ref c) => atomize_constant(atom_tbl, *c),
         _ => None,
     }
 }
 
-fn atomize_constant(atom_tbl: &mut AtomTable, c: Literal) -> Option<Atom> {
+fn atomize_constant(atom_tbl: &AtomTable, c: Literal) -> Option<Atom> {
     match c {
         Literal::Atom(ref name) => Some(*name),
-        Literal::Char(c) => Some(atom_tbl.build_with(&c.to_string())),
+        Literal::Char(c) => Some(AtomTable::build_with(atom_tbl, &c.to_string())),
         _ => None,
     }
 }
@@ -409,7 +399,8 @@ impl<'a, R: CharRead> Parser<'a, R> {
     }
 
     fn promote_atom_op(&mut self, atom: Atom, priority: usize, assoc: u32) {
-        self.terms.push(Term::Literal(Cell::default(), Literal::Atom(atom)));
+        self.terms
+            .push(Term::Literal(Cell::default(), Literal::Atom(atom)));
         self.stack.push(TokenDesc {
             tt: TokenType::Term,
             priority,
@@ -419,7 +410,9 @@ impl<'a, R: CharRead> Parser<'a, R> {
 
     fn shift(&mut self, token: Token, priority: usize, spec: Specifier) {
         let tt = match token {
-            Token::Literal(Literal::String(s)) if self.lexer.machine_st.flags.double_quotes.is_codes() => {
+            Token::Literal(Literal::String(s))
+                if self.lexer.machine_st.flags.double_quotes.is_codes() =>
+            {
                 let mut list = Term::Literal(Cell::default(), Literal::Atom(atom!("[]")));
 
                 for c in s.as_str().chars().rev() {
@@ -436,7 +429,9 @@ impl<'a, R: CharRead> Parser<'a, R> {
                 self.terms.push(list);
                 TokenType::Term
             }
-            Token::Literal(Literal::String(s)) if self.lexer.machine_st.flags.double_quotes.is_chars() => {
+            Token::Literal(Literal::String(s))
+                if self.lexer.machine_st.flags.double_quotes.is_chars() =>
+            {
                 self.terms.push(Term::CompleteString(Cell::default(), s));
                 TokenType::Term
             }
@@ -573,7 +568,7 @@ impl<'a, R: CharRead> Parser<'a, R> {
         let idx = self.terms.len() - arity;
 
         if TokenType::Term == self.stack[stack_len].tt {
-            if atomize_term(&mut self.lexer.machine_st.atom_tbl, &self.terms[idx - 1]).is_some() {
+            if atomize_term(&self.lexer.machine_st.atom_tbl, &self.terms[idx - 1]).is_some() {
                 self.stack.truncate(stack_len + 1);
 
                 let mut subterms: Vec<_> = self.terms.drain(idx..).collect();
@@ -581,27 +576,29 @@ impl<'a, R: CharRead> Parser<'a, R> {
                 if let Some(name) = self
                     .terms
                     .pop()
-                    .and_then(|t| atomize_term(&mut self.lexer.machine_st.atom_tbl, &t))
+                    .and_then(|t| atomize_term(&self.lexer.machine_st.atom_tbl, &t))
                 {
                     // reduce the '.' functor to a cons cell if it applies.
                     if name == atom!(".") && subterms.len() == 2 {
                         let tail = subterms.pop().unwrap();
                         let head = subterms.pop().unwrap();
 
-                        self.terms.push(
+                        self.terms.push(match as_partial_string(head, tail) {
-                            match as_partial_string(head, tail) {
                             Ok((string_buf, Some(tail))) => {
                                 Term::PartialString(Cell::default(), string_buf, tail)
                             }
                             Ok((string_buf, None)) => {
-                                    let atom = self.lexer.machine_st.atom_tbl.build_with(&string_buf);
+                                let atom = AtomTable::build_with(
+                                    &self.lexer.machine_st.atom_tbl,
+                                    &string_buf,
+                                );
                                 Term::CompleteString(Cell::default(), atom)
                             }
                             Err(term) => term,
-                            },
+                        });
-                        );
                     } else {
-                        self.terms.push(Term::Clause(Cell::default(), name, subterms));
+                        self.terms
+                            .push(Term::Clause(Cell::default(), name, subterms));
                     }
 
                     if let Some(&mut TokenDesc {
@@ -695,7 +692,8 @@ impl<'a, R: CharRead> Parser<'a, R> {
                 td.tt = TokenType::Term;
                 td.priority = 0;
 
-                self.terms.push(Term::Literal(Cell::default(), Literal::Atom(atom!("[]"))));
+                self.terms
+                    .push(Term::Literal(Cell::default(), Literal::Atom(atom!("[]"))));
                 return Ok(true);
             }
         }
@@ -736,8 +734,8 @@ impl<'a, R: CharRead> Parser<'a, R> {
         if arity > self.terms.len() {
             return Err(ParserError::IncompleteReduction(
                 self.lexer.line_num,
-                self.lexer.col_num
+                self.lexer.col_num,
-            ))
+            ));
         }
 
         let idx = self.terms.len() - arity;
@@ -755,18 +753,16 @@ impl<'a, R: CharRead> Parser<'a, R> {
         });
 
         self.terms.push(match list {
-            Term::Cons(_, head, tail) => {
+            Term::Cons(_, head, tail) => match as_partial_string(*head, *tail) {
-                match as_partial_string(*head, *tail) {
                 Ok((string_buf, Some(tail))) => {
                     Term::PartialString(Cell::default(), string_buf, tail)
                 }
                 Ok((string_buf, None)) => {
-                        let atom = self.lexer.machine_st.atom_tbl.build_with(&string_buf);
+                    let atom = AtomTable::build_with(&self.lexer.machine_st.atom_tbl, &string_buf);
                     Term::CompleteString(Cell::default(), atom)
                 }
                 Err(term) => term,
-                }
+            },
-            }
             term => term,
         });
 
@@ -784,10 +780,7 @@ impl<'a, R: CharRead> Parser<'a, R> {
                 td.priority = 0;
                 td.spec = TERM;
 
-                let term = Term::Literal(
+                let term = Term::Literal(Cell::default(), Literal::Atom(atom!("{}")));
-                    Cell::default(),
-                    Literal::Atom(atom!("{}")),
-                );
 
                 self.terms.push(term);
                 return Ok(true);
@@ -818,11 +811,8 @@ impl<'a, R: CharRead> Parser<'a, R> {
                             }
                         };
 
-                        self.terms.push(Term::Clause(
+                        self.terms
-                            Cell::default(),
+                            .push(Term::Clause(Cell::default(), atom!("{}"), vec![term]));
-                            atom!("{}"),
-                            vec![term],
-                        ));
 
                         return Ok(true);
                     }
@@ -933,7 +923,8 @@ impl<'a, R: CharRead> Parser<'a, R> {
             if let Some(term) = self.terms.last().cloned() {
                 match term {
                     Term::Literal(_, Literal::Atom(name))
-                        if name == atom!("-") && (is_prefix!(desc.spec) || is_negate!(desc.spec)) =>
+                        if name == atom!("-")
+                            && (is_prefix!(desc.spec) || is_negate!(desc.spec)) =>
                     {
                         self.stack.pop();
                         self.terms.pop();
@@ -983,7 +974,8 @@ impl<'a, R: CharRead> Parser<'a, R> {
                 |n, arena| Literal::from(float_alloc!(n, arena)),
             ),
             Token::Literal(c) => {
-                if let Some(name) = atomize_constant(&mut self.lexer.machine_st.atom_tbl, c) {
+                let atomized = atomize_constant(&self.lexer.machine_st.atom_tbl, c);
+                if let Some(name) = atomized {
                     if !self.shift_op(name, op_dir)? {
                         self.shift(Token::Literal(c), 0, TERM);
                     }
@@ -1069,7 +1061,11 @@ impl<'a, R: CharRead> Parser<'a, R> {
     }
 
     // on success, returns the parsed term and the number of lines read.
-    pub fn read_term(&mut self, op_dir: &CompositeOpDir, tokens: Tokens) -> Result<Term, ParserError> {
+    pub fn read_term(
+        &mut self,
+        op_dir: &CompositeOpDir,
+        tokens: Tokens,
+    ) -> Result<Term, ParserError> {
         self.tokens = match tokens {
             Tokens::Default => read_tokens(&mut self.lexer)?,
             Tokens::Provided(tokens) => tokens,

src/raw_block.rs

@@ -1,6 +1,7 @@
 use core::marker::PhantomData;
 
 use std::alloc;
+use std::cell::UnsafeCell;
 use std::ptr;
 
 pub trait RawBlockTraits {
@@ -12,7 +13,7 @@ pub trait RawBlockTraits {
 pub struct RawBlock<T: RawBlockTraits> {
     pub base: *const u8,
     pub top: *const u8,
-    pub ptr: *mut u8,
+    pub ptr: UnsafeCell<*mut u8>,
     _marker: PhantomData<T>,
 }
 
@@ -22,7 +23,7 @@ impl<T: RawBlockTraits> RawBlock<T> {
         RawBlock {
             base: ptr::null(),
             top: ptr::null(),
-            ptr: ptr::null_mut(),
+            ptr: UnsafeCell::new(ptr::null_mut()),
             _marker: PhantomData,
         }
     }
@@ -42,7 +43,7 @@ impl<T: RawBlockTraits> RawBlock<T> {
 
         self.base = alloc::alloc(layout) as *const _;
         self.top = (self.base as usize + cap) as *const _;
-        self.ptr = self.base as *mut _;
+        *self.ptr.get_mut() = self.base as *mut _;
     }
 
     pub unsafe fn grow(&mut self) {
@@ -54,7 +55,25 @@ impl<T: RawBlockTraits> RawBlock<T> {
 
             self.base = alloc::realloc(self.base as *mut _, layout, size * 2) as *const _;
             self.top = (self.base as usize + size * 2) as *const _;
-            self.ptr = (self.base as usize + size) as *mut _;
+            *self.ptr.get_mut() = (self.base as usize + size) as *mut _;
+        }
+    }
+
+    pub unsafe fn grow_new(&self) -> Option<Self> {
+        if self.base.is_null() {
+            Some(Self::new())
+        } else {
+            let mut new_block = Self::empty_block();
+            new_block.init_at_size(self.size() * 2);
+            if new_block.base.is_null() {
+                // allocation failed
+                None
+            } else {
+                let allocated = (*self.ptr.get()) as usize - self.base as usize;
+                self.base.copy_to(new_block.base.cast_mut(), allocated);
+                *new_block.ptr.get_mut() = new_block.base.offset(allocated as isize).cast_mut();
+                Some(new_block)
+            }
         }
     }
 
@@ -64,35 +83,39 @@ impl<T: RawBlockTraits> RawBlock<T> {
     }
 
     #[inline(always)]
-    fn free_space(&self) -> usize {
+    unsafe fn free_space(&self) -> usize {
         debug_assert!(
-            self.ptr as *const _ >= self.base,
+            *self.ptr.get() as *const _ >= self.base,
             "self.ptr = {:?} < {:?} = self.base",
-            self.ptr,
+            *self.ptr.get(),
             self.base
         );
 
-        self.top as usize - self.ptr as usize
+        self.top as usize - (*self.ptr.get()) as usize
     }
 
-    pub unsafe fn alloc(&mut self, size: usize) -> *mut u8 {
+    pub unsafe fn alloc(&self, size: usize) -> *mut u8 {
         if self.free_space() >= size {
-            let ptr = self.ptr;
+            let ptr = *self.ptr.get();
-            self.ptr = (self.ptr as usize + size) as *mut _;
+            *self.ptr.get() = (ptr as usize + size) as *mut _;
             ptr
         } else {
             ptr::null_mut()
         }
     }
+}
 
-    pub fn deallocate(&mut self) {
+impl<T: RawBlockTraits> Drop for RawBlock<T> {
+    fn drop(&mut self) {
+        if !self.base.is_null() {
             unsafe {
                 let layout = alloc::Layout::from_size_align_unchecked(self.size(), T::align());
                 alloc::dealloc(self.base as *mut _, layout);
+            }
 
             self.top = ptr::null();
             self.base = ptr::null();
-            self.ptr = ptr::null_mut();
+            *self.ptr.get_mut() = ptr::null_mut();
         }
     }
 }

src/rcu.rs

@@ -0,0 +1,221 @@
+use std::{
+    cell::OnceCell,
+    fmt::Debug,
+    mem::ManuallyDrop,
+    ops::Deref,
+    ptr::NonNull,
+    sync::{
+        atomic::{AtomicPtr, AtomicU8},
+        Arc, Weak,
+    },
+};
+
+use tokio::sync::RwLock;
+
+// the epoch counters of all threads that have ever accessed an Rcu
+// threads that have finished will have a dangling Weak reference and can be cleand up
+// having this be shared between all Rcu's is a tradeof,
+// writes will be slower as more epoch counters need to be waited for
+// reads should be faster as a thread only needs to register itself once on the first read
+//
+static EPOCH_COUNTERS: RwLock<Vec<Weak<AtomicU8>>> = RwLock::const_new(Vec::new());
+
+thread_local! {
+    // odd value means the current thread is about to access the active_epoch of an Rcu
+    // a thread has a single epoch counter for all Rcu it accesses,
+    // as a thread can only access one Rcu at a time
+    static THREAD_EPOCH_COUNTER: OnceCell<Arc<AtomicU8>> = OnceCell::new();
+}
+
+pub struct Rcu<T> {
+    active_value: AtomicPtr<T>,
+}
+
+impl<T: std::fmt::Debug> std::fmt::Debug for Rcu<T> {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        let active_epoch = self.active_epoch();
+        f.debug_struct("Rcu")
+            .field("active_value", &active_epoch)
+            .finish()
+    }
+}
+
+impl<T> Rcu<T> {
+    pub fn new(initial_value: T) -> Self {
+        Rcu {
+            active_value: AtomicPtr::new(Arc::into_raw(Arc::new(initial_value)).cast_mut()),
+        }
+    }
+
+    pub fn active_epoch(&self) -> RcuRef<T, T> {
+        THREAD_EPOCH_COUNTER.with(|epoch_counter| {
+            let epoch_counter = epoch_counter.get_or_init(|| {
+                let epoch_counter = Arc::new(AtomicU8::new(0));
+                // register the current threads epoch counter on init
+                EPOCH_COUNTERS
+                    .blocking_write()
+                    .push(Arc::downgrade(&epoch_counter));
+                epoch_counter
+            });
+
+            let old = epoch_counter.fetch_add(1, std::sync::atomic::Ordering::AcqRel);
+            assert!(old % 2 == 0, "Old Epoch counter value should be even!");
+        });
+
+        let arc_ptr = self.active_value.load(std::sync::atomic::Ordering::Acquire);
+
+        let arc = unsafe {
+            // Safety:
+            // - the ptr was created in Rcu::new or Rcu::replace with Arc::into_raw
+            // - the Rcu is responsible for of the arc's strong refrences
+            // - the Rcu is alive as this function takes a reference to the Rcu
+            // - replace will wait with decrementing the old values strong count until our epoich counter is even again
+            Arc::increment_strong_count(arc_ptr);
+            // Safety:
+            // - the ptr was created in Rcu::new or Rcu::replace with Arc::into_raw
+            // - we have just ensured an additional strong count by incrementing the count
+            Arc::from_raw(arc_ptr)
+        };
+
+        THREAD_EPOCH_COUNTER.with(|epoch_counter| {
+            let old = epoch_counter
+                .get().expect("we initialized the OnceCell when we incremented the epoch counter the fist time")
+                .fetch_add(1, std::sync::atomic::Ordering::AcqRel);
+            assert!(old % 2 != 0, "Old Epoch counter value should be odd!");
+        });
+
+        RcuRef {
+            data: arc.deref().into(),
+            arc,
+        }
+    }
+
+    /*
+     *  replace the Rcu'S content with a new value
+     *
+     *  This does not syncronize write and last to update the active_value pointer wins,
+     *  all writes that do not win will be lost, though not leaked.
+     *  This will block untill the old value can be reclaimed,
+     *  i.e. all threads whitnest to be in the read critical sections
+     *       have been witnest to have left the critical section at least once
+     */
+    pub fn replace(&self, new_value: T) {
+        let arc_ptr = self.active_value.swap(
+            Arc::into_raw(Arc::new(new_value)).cast_mut(),
+            std::sync::atomic::Ordering::AcqRel,
+        );
+
+        // maually drop as we need to ensure not to drop the arc while
+        // we have not witnest all threads to be or have been outside the read critical section
+        // i.e. even epoch counter or different odd epoch counter
+        // Safety:
+        // - the ptr was created in Rcu::new or Rcu::replace with Arc::into_raw
+        // - the Rcu itself holds one strong count
+        let arc = unsafe { ManuallyDrop::new(Arc::from_raw(arc_ptr)) };
+
+        let epochs = EPOCH_COUNTERS.blocking_read().clone();
+        let mut epochs = epochs
+            .into_iter()
+            .flat_map(|elem| {
+                let arc = elem.upgrade()?;
+                let init_val = arc.load(std::sync::atomic::Ordering::Acquire);
+                if init_val % 2 == 0 {
+                    // already even can be ignored
+                    return None;
+                }
+                // odd initial value thread is in read critical section
+                // need to wait for the value to change before we can drop the arc
+                Some((init_val, elem))
+            })
+            .collect::<Vec<_>>();
+
+        while !epochs.is_empty() {
+            epochs.retain(|elem| {
+                let Some(arc) = elem.1.upgrade() else {
+                    // as the thread is dead it can't have a ref to old arc
+                    return false;
+                };
+                // the epoch counter has not changed so the thread is still in the same instance of the critical section
+                // any different value is ok as
+                // - even values indicate the thread is outside the critical section
+                // - a diffrent odd value indicates the thread has left the critical section and can subsequently only read the new active_value
+                arc.load(std::sync::atomic::Ordering::Acquire) == elem.0
+            })
+        }
+
+        // Safety:
+        // - we have not dropped the arc another way
+        // - we witnessed all threads either with an even epoch count or with a new odd count
+        //   as such they must have left the critical section at some point
+        ManuallyDrop::into_inner(arc);
+    }
+}
+
+pub struct RcuRef<T, M>
+where
+    T: ?Sized,
+    M: ?Sized,
+{
+    arc: Arc<T>,
+    data: NonNull<M>,
+}
+
+impl<T: ?Sized, M: ?Sized + Debug> Debug for RcuRef<T, M> {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        f.debug_struct("RcuRef")
+            .field("data", &self.deref())
+            .finish()
+    }
+}
+
+// use assoiated functions rather than methods so that we don't overlap
+// with functions of the Deref Target type
+impl<T: ?Sized, M: ?Sized> RcuRef<T, M> {
+    pub fn map<N: ?Sized, F: for<'a> FnOnce(&'a M) -> &'a N>(referece: Self, f: F) -> RcuRef<T, N> {
+        RcuRef {
+            arc: referece.arc,
+            data: f(unsafe { referece.data.as_ref() }).into(),
+        }
+    }
+
+    pub fn try_map<N: ?Sized, F: for<'a> FnOnce(&'a M) -> Option<&'a N>>(
+        referece: Self,
+        f: F,
+    ) -> Option<RcuRef<T, N>> {
+        let val = f(unsafe { referece.data.as_ref() })?;
+        Some(RcuRef {
+            arc: Arc::clone(&referece.arc),
+            data: val.into(),
+        })
+    }
+
+    pub fn same_epoch<M2>(this: &Self, other: &RcuRef<T, M2>) -> bool {
+        Arc::ptr_eq(&this.arc, &other.arc)
+    }
+
+    pub fn ptr_eq(this: &Self, other: &Self) -> bool {
+        this.data == other.data
+    }
+
+    pub fn clone(this: &Self) -> Self {
+        Self {
+            arc: Arc::clone(&this.arc),
+            data: this.data,
+        }
+    }
+
+    pub fn get_root(this: &Self) -> &T {
+        &this.arc
+    }
+}
+
+impl<T: ?Sized, M: ?Sized> Deref for RcuRef<T, M> {
+    type Target = M;
+
+    fn deref(&self) -> &Self::Target {
+        // Safety: The pointer points into the arc we are holding
+        // while we are alive so is the target
+        // as the content is in an Rcu no mutable acess is given out
+        unsafe { self.data.as_ref() }
+    }
+}

src/read.rs

@@ -16,8 +16,6 @@ use crate::types::*;
 
 use fxhash::FxBuildHasher;
 
-use indexmap::IndexSet;
-
 #[cfg(feature = "repl")]
 use rustyline::error::ReadlineError;
 #[cfg(feature = "repl")]
@@ -27,18 +25,17 @@ use rustyline::{Config, Editor};
 
 use std::collections::VecDeque;
 use std::io::{Cursor, Error, ErrorKind, Read};
+use std::sync::Arc;
 
 type SubtermDeque = VecDeque<(usize, usize)>;
 
-pub(crate) fn devour_whitespace<'a, R: CharRead>(parser: &mut Parser<'a, R>) -> Result<bool, ParserError> {
+pub(crate) fn devour_whitespace<'a, R: CharRead>(
+    parser: &mut Parser<'a, R>,
+) -> Result<bool, ParserError> {
     match parser.lexer.scan_for_layout() {
-        Err(e) if e.is_unexpected_eof() => {
+        Err(e) if e.is_unexpected_eof() => Ok(true),
-            Ok(true)
-        }
         Err(e) => Err(e),
-        Ok(_) => {
+        Ok(_) => Ok(false),
-            Ok(false)
-        }
     }
 }
 
@@ -60,7 +57,6 @@ pub(crate) fn error_after_read_term<R>(
     CompilationError::from(err)
 }
 
-
 impl MachineState {
     pub(crate) fn read(
         &mut self,
@@ -74,14 +70,15 @@ impl MachineState {
 
             parser.add_lines_read(prior_num_lines_read);
 
-            let term = parser.read_term(&op_dir, Tokens::Default)
+            let term = parser
+                .read_term(&op_dir, Tokens::Default)
                 .map_err(|err| error_after_read_term(err, prior_num_lines_read, &parser))?; // CompilationError::from
 
             (term, parser.lines_read() - prior_num_lines_read)
         };
 
         inner.add_lines_read(num_lines_read);
-        write_term_to_heap(&term, &mut self.heap, &mut self.atom_tbl)
+        write_term_to_heap(&term, &mut self.heap, &self.atom_tbl)
     }
 }
 
@@ -114,12 +111,11 @@ pub struct ReadlineStream {
 }
 
 impl ReadlineStream {
-    #[cfg(feature = "repl")]
     #[inline]
     pub fn new(pending_input: &str, add_history: bool) -> Self {
-        let config = Config::builder()
+        #[cfg(feature = "repl")]
-            .check_cursor_position(true)
+        {
-            .build();
+            let config = Config::builder().check_cursor_position(true).build();
 
             let helper = Helper::new();
 
@@ -141,22 +137,20 @@ impl ReadlineStream {
         }
 
         #[cfg(not(feature = "repl"))]
-    #[inline]
+        {
-    pub fn new(pending_input: &str, add_history: bool) -> Self {
             ReadlineStream {
                 pending_input: CharReader::new(Cursor::new(pending_input.to_owned())),
                 add_history: add_history,
             }
         }
-
-    #[cfg(feature = "repl")]
-    pub fn set_atoms_for_completion(&mut self, atoms: *const IndexSet<Atom>) {
-        let helper = self.rl.helper_mut().unwrap();
-        helper.atoms = atoms;
     }
 
-    #[cfg(not(feature = "repl"))]
+    pub fn set_atoms_for_completion(&mut self, atoms: &Arc<AtomTable>) {
-    pub fn set_atoms_for_completion(&mut self, atoms: *const IndexSet<Atom>) {
+        #[cfg(feature = "repl")]
+        {
+            let helper = self.rl.helper_mut().unwrap();
+            helper.atoms = Arc::downgrade(atoms);
+        }
     }
 
     #[inline]
@@ -180,7 +174,9 @@ impl ReadlineStream {
 
                 unsafe {
                     if PROMPT {
-                        self.rl.add_history_entry(self.pending_input.get_ref().get_ref()).unwrap();
+                        self.rl
+                            .add_history_entry(self.pending_input.get_ref().get_ref())
+                            .unwrap();
                         self.save_history();
                         PROMPT = false;
                     }
@@ -220,8 +216,7 @@ impl ReadlineStream {
     }
 
     #[cfg(not(feature = "repl"))]
-    fn save_history(&mut self) {
+    fn save_history(&mut self) {}
-    }
 
     #[inline]
     pub(crate) fn peek_byte(&mut self) -> std::io::Result<u8> {
@@ -253,7 +248,7 @@ impl Read for ReadlineStream {
                 self.call_readline()?;
                 self.pending_input.read(buf)
             }
-            result => result
+            result => result,
         }
     }
 }
@@ -266,16 +261,14 @@ impl CharRead for ReadlineStream {
                 Some(Ok(c)) => {
                     return Some(Ok(c));
                 }
-                _ => {
+                _ => match self.call_readline() {
-                    match self.call_readline() {
                     Err(e) => {
                         return Some(Err(e));
                     }
                     _ => {
                         set_prompt(false);
                     }
-                    }
+                },
-                }
             }
         }
     }
@@ -295,7 +288,7 @@ impl CharRead for ReadlineStream {
 pub(crate) fn write_term_to_heap<'a, 'b>(
     term: &'a Term,
     heap: &'b mut Heap,
-    atom_tbl: &mut AtomTable,
+    atom_tbl: &AtomTable,
 ) -> Result<TermWriteResult, CompilationError> {
     let term_writer = TermWriter::new(heap, atom_tbl);
     term_writer.write_term_to_heap(term)
@@ -304,7 +297,7 @@ pub(crate) fn write_term_to_heap<'a, 'b>(
 #[derive(Debug)]
 struct TermWriter<'a, 'b> {
     heap: &'a mut Heap,
-    atom_tbl: &'b mut AtomTable,
+    atom_tbl: &'b AtomTable,
     queue: SubtermDeque,
     var_dict: HeapVarDict,
 }
@@ -317,7 +310,7 @@ pub struct TermWriteResult {
 
 impl<'a, 'b> TermWriter<'a, 'b> {
     #[inline]
-    fn new(heap: &'a mut Heap, atom_tbl: &'b mut AtomTable) -> Self {
+    fn new(heap: &'a mut Heap, atom_tbl: &'b AtomTable) -> Self {
         TermWriter {
             heap,
             atom_tbl,
@@ -347,14 +340,15 @@ impl<'a, 'b> TermWriter<'a, 'b> {
         match term {
             &TermRef::Cons(..) => list_loc_as_cell!(h),
             &TermRef::AnonVar(_) | &TermRef::Var(..) => heap_loc_as_cell!(h),
-            &TermRef::CompleteString(_, _, ref src) =>
+            &TermRef::CompleteString(_, _, ref src) => {
                 if src.as_str().is_empty() {
                     empty_list_as_cell!()
                 } else if self.heap[h].get_tag() == HeapCellValueTag::CStr {
                     heap_loc_as_cell!(h)
                 } else {
                     pstr_loc_as_cell!(h)
-                },
+                }
+            }
             &TermRef::PartialString(..) => pstr_loc_as_cell!(h),
             &TermRef::Literal(_, _, literal) => HeapCellValue::from(*literal),
             &TermRef::Clause(_, _, _, subterms) if subterms.len() == 0 => heap_loc_as_cell!(h),
@@ -427,7 +421,8 @@ impl<'a, 'b> TermWriter<'a, 'b> {
                 }
                 &TermRef::AnonVar(_) => {
                     if let Some((arity, site_h)) = self.queue.pop_front() {
-                        self.var_dict.insert(VarKey::AnonVar(h), heap_loc_as_cell!(site_h));
+                        self.var_dict
+                            .insert(VarKey::AnonVar(h), heap_loc_as_cell!(site_h));
 
                         if arity > 1 {
                             self.queue.push_front((arity - 1, site_h + 1));
@@ -437,7 +432,8 @@ impl<'a, 'b> TermWriter<'a, 'b> {
                     continue;
                 }
                 &TermRef::CompleteString(_, _, ref src) => {
-                    put_complete_string(self.heap, src.as_str(), self.atom_tbl);
+                    let src = src.as_str().to_owned();
+                    put_complete_string(self.heap, &src, self.atom_tbl);
                 }
                 &TermRef::PartialString(lvl, _, ref src, _) => {
                     if let Level::Root = lvl {

src/repl_helper.rs

@@ -1,23 +1,24 @@
-use indexmap::IndexSet;
+use rustyline::completion::Completer;
-use rustyline::completion::{Completer, Candidate};
+use rustyline::highlight::{Highlighter, MatchingBracketHighlighter};
 use rustyline::hint::Hinter;
 use rustyline::validate::Validator;
-use rustyline::highlight::{MatchingBracketHighlighter, Highlighter};
+use rustyline::{Context, Helper as RlHelper, Result};
-use rustyline::{Helper as RlHelper, Result, Context};
 
-use crate::atom_table::{Atom, STATIC_ATOMS_MAP};
+use std::sync::Weak;
+
+use crate::atom_table::{AtomString, AtomTable, STATIC_ATOMS_MAP};
 
 // TODO: Maybe add validation to the helper
 pub struct Helper {
     highligher: MatchingBracketHighlighter,
-    pub atoms: *const IndexSet<Atom>,
+    pub atoms: Weak<AtomTable>,
 }
 
 impl Helper {
     pub fn new() -> Self {
         Self {
             highligher: MatchingBracketHighlighter::new(),
-            atoms: std::ptr::null(),
+            atoms: Weak::new(),
         }
     }
 }
@@ -43,7 +44,7 @@ fn get_prefix(line: &str, pos: usize) -> Option<usize> {
         }
 
         if i == pos {
-            break
+            break;
         }
     }
 
@@ -54,39 +55,33 @@ fn get_prefix(line: &str, pos: usize) -> Option<usize> {
     start_of_atom
 }
 
-pub struct StrPtr(*const str);
-
-impl Candidate for StrPtr {
-    fn display(&self) -> &str {
-        unsafe {
-            self.0.as_ref().unwrap()
-        }
-    }
-
-    fn replacement(&self) -> &str {
-        unsafe {
-            self.0.as_ref().unwrap()
-        }
-    }
-}
-
 impl Completer for Helper {
-    type Candidate = StrPtr;
+    type Candidate = AtomString<'static>;
 
-    fn complete(&self, line: &str, pos: usize, _ctx: &Context<'_>) -> Result<(usize, Vec<Self::Candidate>)> {
+    fn complete(
+        &self,
+        line: &str,
+        pos: usize,
+        _ctx: &Context<'_>,
+    ) -> Result<(usize, Vec<Self::Candidate>)> {
         let start_of_prefix = get_prefix(line, pos);
         if let Some(idx) = start_of_prefix {
             let sub_str = line.get(idx..pos).unwrap();
-            Ok((idx, unsafe {
+
-                let mut matching = (*self.atoms).iter()
+            let atom_table = self.atoms.upgrade().unwrap();
+
+            let index_set = atom_table.active_table();
+
+            let mut matching = index_set
+                .iter()
                 .chain(STATIC_ATOMS_MAP.values())
-                    .filter(|a| a.as_str().starts_with(sub_str))
+                .map(|a| a.as_str())
-                    .map(|s| StrPtr(s.as_str()))
+                .filter(|a| a.starts_with(sub_str))
                 .collect::<Vec<_>>();
 
-                matching.sort_unstable_by(|a, b| Ord::cmp(&(*a.0).len(), &(*b.0).len()));
+            matching.sort_unstable_by(|a, b| Ord::cmp(&a.len(), &b.len()));
-                matching
+
-            }))
+            Ok((idx, matching))
         } else {
             Ok((0, vec![]))
         }

src/types.rs

@@ -121,28 +121,24 @@ pub(crate) enum RefTag {
 #[derive(Copy, Clone, Debug, Hash, PartialEq, Eq)]
 pub struct Ref {
     val: B56,
-    #[allow(unused)] m: bool,
+    #[allow(unused)]
-    #[allow(unused)] f: bool,
+    m: bool,
+    #[allow(unused)]
+    f: bool,
     tag: RefTag,
 }
 
 impl Ord for Ref {
     fn cmp(&self, rhs: &Ref) -> Ordering {
         match self.get_tag() {
-            RefTag::HeapCell | RefTag::AttrVar => {
+            RefTag::HeapCell | RefTag::AttrVar => match rhs.get_tag() {
-                match rhs.get_tag() {
                 RefTag::StackCell => Ordering::Less,
                 _ => self.get_value().cmp(&rhs.get_value()),
-                }
+            },
-            }
+            RefTag::StackCell => match rhs.get_tag() {
-            RefTag::StackCell => {
+                RefTag::StackCell => self.get_value().cmp(&rhs.get_value()),
-                match rhs.get_tag() {
+                _ => Ordering::Greater,
-                    RefTag::StackCell =>
+            },
-                        self.get_value().cmp(&rhs.get_value()),
-                    _ =>
-                        Ordering::Greater,
-                }
-            }
         }
     }
 }
@@ -215,9 +211,12 @@ pub(crate) enum TrailEntryTag {
 #[repr(u64)]
 pub(crate) struct TrailEntry {
     val: B56,
-    #[allow(unused)] f: bool,
+    #[allow(unused)]
-    #[allow(unused)] m: bool,
+    f: bool,
-    #[allow(unused)] tag: TrailEntryTag,
+    #[allow(unused)]
+    m: bool,
+    #[allow(unused)]
+    tag: TrailEntryTag,
 }
 
 impl TrailEntry {
@@ -257,14 +256,13 @@ pub struct HeapCellValue {
 impl fmt::Debug for HeapCellValue {
     fn fmt(&self, f: &mut std::fmt::Formatter) -> fmt::Result {
         match self.get_tag() {
-            HeapCellValueTag::F64 => {
+            HeapCellValueTag::F64 => f
-                f.debug_struct("HeapCellValue")
+                .debug_struct("HeapCellValue")
                 .field("tag", &HeapCellValueTag::F64)
                 .field("offset", &self.get_value())
                 .field("m", &self.m())
                 .field("f", &self.f())
-                    .finish()
+                .finish(),
-            }
             HeapCellValueTag::Cons => {
                 let cons_ptr = ConsPtr::from_bytes(self.into_bytes());
 
@@ -276,8 +274,7 @@ impl fmt::Debug for HeapCellValue {
                     .finish()
             }
             HeapCellValueTag::Atom => {
-                let (name, arity) = cell_as_atom_cell!(self)
+                let (name, arity) = cell_as_atom_cell!(self).get_name_and_arity();
-                     .get_name_and_arity();
 
                 f.debug_struct("HeapCellValue")
                     .field("tag", &HeapCellValueTag::Atom)
@@ -288,8 +285,7 @@ impl fmt::Debug for HeapCellValue {
                     .finish()
             }
             HeapCellValueTag::PStr => {
-                let (name, _) = cell_as_atom_cell!(self)
+                let (name, _) = cell_as_atom_cell!(self).get_name_and_arity();
-                     .get_name_and_arity();
 
                 f.debug_struct("HeapCellValue")
                     .field("tag", &HeapCellValueTag::PStr)
@@ -298,14 +294,13 @@ impl fmt::Debug for HeapCellValue {
                     .field("f", &self.f())
                     .finish()
             }
-            tag => {
+            tag => f
-                f.debug_struct("HeapCellValue")
+                .debug_struct("HeapCellValue")
                 .field("tag", &tag)
                 .field("value", &self.get_value())
                 .field("m", &self.get_mark_bit())
                 .field("f", &self.get_forwarding_bit())
-                    .finish()
+                .finish(),
-            }
         }
     }
 }
@@ -320,10 +315,7 @@ impl<T: ArenaAllocated> From<TypedArenaPtr<T>> for HeapCellValue {
 impl From<F64Ptr> for HeapCellValue {
     #[inline]
     fn from(f64_ptr: F64Ptr) -> HeapCellValue {
-        HeapCellValue::build_with(
+        HeapCellValue::build_with(HeapCellValueTag::F64, f64_ptr.as_offset().to_u64())
-            HeapCellValueTag::F64,
-            f64_ptr.as_offset().to_u64(),
-        )
     }
 }
 
@@ -402,9 +394,13 @@ impl HeapCellValue {
     #[inline]
     pub fn is_ref(self) -> bool {
         match self.get_tag() {
-            HeapCellValueTag::Str | HeapCellValueTag::Lis | HeapCellValueTag::Var |
+            HeapCellValueTag::Str
-            HeapCellValueTag::StackVar | HeapCellValueTag::AttrVar | HeapCellValueTag::PStrLoc |
+            | HeapCellValueTag::Lis
-            HeapCellValueTag::PStrOffset => true,
+            | HeapCellValueTag::Var
+            | HeapCellValueTag::StackVar
+            | HeapCellValueTag::AttrVar
+            | HeapCellValueTag::PStrLoc
+            | HeapCellValueTag::PStrOffset => true,
             _ => false,
         }
     }
@@ -431,16 +427,13 @@ impl HeapCellValue {
     #[inline]
     pub fn is_constant(self) -> bool {
         match self.get_tag() {
-            HeapCellValueTag::Cons | HeapCellValueTag::F64 | HeapCellValueTag::Fixnum |
+            HeapCellValueTag::Cons
-            HeapCellValueTag::Char | HeapCellValueTag::CStr => {
+            | HeapCellValueTag::F64
-                true
+            | HeapCellValueTag::Fixnum
-            }
+            | HeapCellValueTag::Char
-            HeapCellValueTag::Atom => {
+            | HeapCellValueTag::CStr => true,
-                cell_as_atom_cell!(self).get_arity() == 0
+            HeapCellValueTag::Atom => cell_as_atom_cell!(self).get_arity() == 0,
-            }
+            _ => false,
-            _ => {
-                false
-            }
         }
     }
 
@@ -455,17 +448,13 @@ impl HeapCellValue {
             HeapCellValueTag::Str => {
                 cell_as_atom_cell!(heap[self.get_value() as usize]).get_arity() > 0
             }
-            HeapCellValueTag::Lis |
+            HeapCellValueTag::Lis
-            HeapCellValueTag::CStr |
+            | HeapCellValueTag::CStr
-            HeapCellValueTag::PStr |
+            | HeapCellValueTag::PStr
-            HeapCellValueTag::PStrLoc |
+            | HeapCellValueTag::PStrLoc
-            HeapCellValueTag::PStrOffset => {
+            | HeapCellValueTag::PStrOffset => true,
-               true
+            HeapCellValueTag::Atom => cell_as_atom_cell!(self).get_arity() > 0,
-            }
+            _ => false,
-            HeapCellValueTag::Atom => {
-                cell_as_atom_cell!(self).get_arity() > 0
-            }
-            _ => { false }
         }
     }
 
@@ -530,9 +519,7 @@ impl HeapCellValue {
     #[inline]
     pub fn to_pstr(self) -> Option<PartialString> {
         match self.tag() {
-            HeapCellValueTag::PStr => {
+            HeapCellValueTag::PStr => Some(PartialString::from(Atom::from(self.val() << 3))),
-                Some(PartialString::from(Atom::from(self.val() << 3)))
-            }
             _ => None,
         }
     }
@@ -548,7 +535,16 @@ impl HeapCellValue {
     #[cfg(target_pointer_width = "32")]
     #[inline]
     pub fn from_raw_ptr_bytes(ptr_bytes: [u8; 4]) -> Self {
-        HeapCellValue::from_bytes([ptr_bytes[0], ptr_bytes[1], ptr_bytes[2], ptr_bytes[3], 0, 0, 0, 0])
+        HeapCellValue::from_bytes([
+            ptr_bytes[0],
+            ptr_bytes[1],
+            ptr_bytes[2],
+            ptr_bytes[3],
+            0,
+            0,
+            0,
+            0,
+        ])
     }
     #[cfg(target_pointer_width = "64")]
     #[inline]
@@ -577,7 +573,9 @@ impl HeapCellValue {
     #[inline]
     pub fn to_untyped_arena_ptr(self) -> Option<UntypedArenaPtr> {
         match self.get_tag() {
-            HeapCellValueTag::Cons => Some(UntypedArenaPtr::from_bytes(self.to_untyped_arena_ptr_bytes())),
+            HeapCellValueTag::Cons => Some(UntypedArenaPtr::from_bytes(
+                self.to_untyped_arena_ptr_bytes(),
+            )),
             _ => None,
         }
     }
@@ -586,7 +584,7 @@ impl HeapCellValue {
     pub fn get_forwarding_bit(self) -> bool {
         match self.get_tag() {
             HeapCellValueTag::Cons => ConsPtr::from_bytes(self.into_bytes()).f(),
-            _ => self.f()
+            _ => self.f(),
         }
     }
 
@@ -604,9 +602,7 @@ impl HeapCellValue {
     #[inline(always)]
     pub fn get_mark_bit(self) -> bool {
         match self.get_tag() {
-            HeapCellValueTag::Cons => {
+            HeapCellValueTag::Cons => ConsPtr::from_bytes(self.into_bytes()).m(),
-                ConsPtr::from_bytes(self.into_bytes()).m()
-            }
             _ => self.m(),
         }
     }
@@ -633,15 +629,12 @@ impl HeapCellValue {
                     Some(TermOrderCategory::Variable)
                 }
                 HeapCellValueTag::Char => Some(TermOrderCategory::Atom),
-                HeapCellValueTag::Atom => {
+                HeapCellValueTag::Atom => Some(if cell_as_atom_cell!(self).get_arity() > 0 {
-                    Some(if cell_as_atom_cell!(self).get_arity() > 0 {
                     TermOrderCategory::Compound
                 } else {
                     TermOrderCategory::Atom
-                    })
+                }),
-                }
+                HeapCellValueTag::Lis | HeapCellValueTag::PStrLoc | HeapCellValueTag::CStr => {
-                HeapCellValueTag::Lis | HeapCellValueTag::PStrLoc |
-                HeapCellValueTag::CStr => {
                     Some(TermOrderCategory::Compound)
                 }
                 HeapCellValueTag::Str => {
@@ -654,9 +647,7 @@ impl HeapCellValue {
                         Some(TermOrderCategory::Compound)
                     }
                 }
-                _ => {
+                _ => None,
-                    None
-                }
             },
         }
     }
@@ -680,16 +671,17 @@ const_assert!(mem::size_of::<HeapCellValue>() == 8);
 #[repr(u64)]
 #[derive(Copy, Clone, Debug, Hash, PartialEq, Eq)]
 pub struct UntypedArenaPtr {
-    #[allow(unused)] ptr: B61,
+    #[allow(unused)]
+    ptr: B61,
     m: bool,
-    #[allow(unused)] padding: B2,
+    #[allow(unused)]
+    padding: B2,
 }
 
 impl UntypedArenaPtr {
     #[inline(always)]
     pub fn build_with(ptr: usize) -> Self {
-        UntypedArenaPtr::new()
+        UntypedArenaPtr::new().with_ptr(ptr as u64)
-            .with_ptr(ptr as u64)
     }
 }
 
@@ -763,17 +755,15 @@ impl Add<usize> for HeapCellValue {
 
     fn add(self, rhs: usize) -> Self::Output {
         match self.get_tag() {
-            tag @ HeapCellValueTag::Str |
+            tag @ HeapCellValueTag::Str
-            tag @ HeapCellValueTag::Lis |
+            | tag @ HeapCellValueTag::Lis
-            tag @ HeapCellValueTag::PStrOffset |
+            | tag @ HeapCellValueTag::PStrOffset
-            tag @ HeapCellValueTag::PStrLoc |
+            | tag @ HeapCellValueTag::PStrLoc
-            tag @ HeapCellValueTag::Var |
+            | tag @ HeapCellValueTag::Var
-            tag @ HeapCellValueTag::AttrVar => {
+            | tag @ HeapCellValueTag::AttrVar => {
                 HeapCellValue::build_with(tag, (self.get_value() as usize + rhs) as u64)
             }
-            _ => {
+            _ => self,
-                self
-            }
         }
     }
 }
@@ -783,17 +773,15 @@ impl Sub<usize> for HeapCellValue {
 
     fn sub(self, rhs: usize) -> Self::Output {
         match self.get_tag() {
-            tag @ HeapCellValueTag::Str |
+            tag @ HeapCellValueTag::Str
-            tag @ HeapCellValueTag::Lis |
+            | tag @ HeapCellValueTag::Lis
-            tag @ HeapCellValueTag::PStrOffset |
+            | tag @ HeapCellValueTag::PStrOffset
-            tag @ HeapCellValueTag::PStrLoc |
+            | tag @ HeapCellValueTag::PStrLoc
-            tag @ HeapCellValueTag::Var |
+            | tag @ HeapCellValueTag::Var
-            tag @ HeapCellValueTag::AttrVar => {
+            | tag @ HeapCellValueTag::AttrVar => {
                 HeapCellValue::build_with(tag, (self.get_value() as usize - rhs) as u64)
             }
-            _ => {
+            _ => self,
-                self
-            }
         }
     }
 }
@@ -811,21 +799,18 @@ impl Sub<i64> for HeapCellValue {
     fn sub(self, rhs: i64) -> Self::Output {
         if rhs < 0 {
             match self.get_tag() {
-                tag @ HeapCellValueTag::Str |
+                tag @ HeapCellValueTag::Str
-                tag @ HeapCellValueTag::Lis |
+                | tag @ HeapCellValueTag::Lis
-                tag @ HeapCellValueTag::PStrOffset |
+                | tag @ HeapCellValueTag::PStrOffset
-                tag @ HeapCellValueTag::PStrLoc |
+                | tag @ HeapCellValueTag::PStrLoc
-                tag @ HeapCellValueTag::Var |
+                | tag @ HeapCellValueTag::Var
-                tag @ HeapCellValueTag::AttrVar => {
+                | tag @ HeapCellValueTag::AttrVar => {
                     HeapCellValue::build_with(tag, self.get_value() + rhs.abs() as u64)
                 }
-                _ => {
+                _ => self,
-                    self
-                }
             }
         } else {
             self.sub(rhs as usize)
         }
     }
 }
-

src/variable_records.rs

@@ -56,8 +56,10 @@ impl VarSafetyStatus {
 
 #[derive(Debug, Clone, Copy)]
 pub enum PermVarAllocation {
-    Done { shallow_safety: VarSafetyStatus,
+    Done {
-           deep_safety: VarSafetyStatus },
+        shallow_safety: VarSafetyStatus,
+        deep_safety: VarSafetyStatus,
+    },
     Pending,
 }
 
@@ -81,11 +83,13 @@ impl PermVarAllocation {
 
 #[derive(Debug, Clone)]
 pub enum VarAlloc {
-    Temp { term_loc: GenContext,
+    Temp {
+        term_loc: GenContext,
         temp_reg: usize,
         temp_var_data: TempVarData,
         safety: VarSafetyStatus,
-           to_perm_var_num: Option<usize> },
+        to_perm_var_num: Option<usize>,
+    },
     Perm(usize, PermVarAllocation), // stack offset, allocation info
 }
 
@@ -102,7 +106,9 @@ impl VarAlloc {
     pub(crate) fn set_register(&mut self, reg_num: usize) {
         match self {
             VarAlloc::Perm(ref mut p, _) => *p = reg_num,
-            VarAlloc::Temp { ref mut temp_reg, .. } => *temp_reg = reg_num,
+            VarAlloc::Temp {
+                ref mut temp_reg, ..
+            } => *temp_reg = reg_num,
         };
     }
 }
@@ -191,7 +197,8 @@ impl VariableRecords {
         // Compute the conflict set of u.
 
         // 1.
-        let mut use_sets: IndexMap<usize, IndexSet<(GenContext, usize), FxBuildHasher>> = IndexMap::new();
+        let mut use_sets: IndexMap<usize, IndexSet<(GenContext, usize), FxBuildHasher>> =
+            IndexMap::new();
 
         for (var_gen_index, record) in self.0.iter_mut().enumerate() {
             match &mut record.allocation {
@@ -203,8 +210,7 @@ impl VariableRecords {
 
                     use_sets.insert(var_gen_index, use_set);
                 }
-                _ => {
+                _ => {}
-                }
             }
         }
 
@@ -214,7 +220,11 @@ impl VariableRecords {
                 if let GenContext::Last(cn_u) = term_loc {
                     for (var_gen_index, record) in self.0.iter_mut().enumerate() {
                         match &mut record.allocation {
-                            VarAlloc::Temp { term_loc, temp_var_data, .. } => {
+                            VarAlloc::Temp {
+                                term_loc,
+                                temp_var_data,
+                                ..
+                            } => {
                                 if cn_u == term_loc.chunk_num() && u != var_gen_index {
                                     if !temp_var_data.uses_reg(reg) {
                                         temp_var_data.no_use_set.insert(reg);

tests/scryer/issues.rs

@@ -1,5 +1,4 @@
 use crate::helper::{load_module_test, run_top_level_test_no_args, run_top_level_test_with_args};
-use scryer_prolog::machine::Machine;
 use serial_test::serial;
 
 // issue #857
@@ -171,16 +170,3 @@ fn call_0() {
         "   error(existence_error(procedure,call/0),call/0).\n",
     );
 }
-
-// issue #1206
-#[serial]
-#[test]
-#[should_panic(expected = "Overwriting atom table base pointer")]
-fn atomtable_is_not_concurrency_safe() {
-    // this is basically the same test as scryer_prolog::atom_table::atomtable_is_not_concurrency_safe
-    // but for this integration test scryer_prolog is compiled with cfg!(not(test))  while for the unit test it is compiled with cfg!(test)
-    // as the atom table implementation differ between cfg!(test) and cfg!(not(test)) both test serve a pourpose
-    // Note: this integration test itself is compiled with cfg!(test) independent of scryer_prolog itself
-    let _machine_a = Machine::with_test_streams();
-    let _machine_b = Machine::with_test_streams();
-}

tests/scryer/src_tests.rs

@@ -73,8 +73,5 @@ fn clpz_load() {
 #[serial]
 #[test]
 fn iso_conformity_tests() {
-    load_module_test(
+    load_module_test("tests-pl/iso-conformity-tests.pl", "All tests passed");
-        "tests-pl/iso-conformity-tests.pl",
-        "All tests passed",
-    );
 }