use new heap term representation

src/machine/attributed_variables.rs

@@ -1,13 +1,15 @@
 use crate::heap_iter::*;
 use crate::machine::*;
-use prolog_parser::temp_v;
+use crate::parser::ast::*;
+use crate::temp_v;
+use crate::types::*;
 
 use indexmap::IndexSet;
 
 use std::cmp::Ordering;
 use std::vec::IntoIter;
 
-pub(super) type Bindings = Vec<(usize, Addr)>;
+pub(super) type Bindings = Vec<(usize, HeapCellValue)>;
 
 #[derive(Debug)]
 pub(super) struct AttrVarInitializer {
@@ -37,7 +39,7 @@ impl AttrVarInitializer {
 }
 
 impl MachineState {
-    pub(super) fn push_attr_var_binding(&mut self, h: usize, addr: Addr) {
+    pub(super) fn push_attr_var_binding(&mut self, h: usize, addr: HeapCellValue) {
         if self.attr_var_init.bindings.is_empty() {
             self.attr_var_init.instigating_p = self.p.local();
 
@@ -53,28 +55,24 @@ impl MachineState {
         self.attr_var_init.bindings.push((h, addr));
     }
 
-    fn populate_var_and_value_lists(&mut self) -> (Addr, Addr) {
+    fn populate_var_and_value_lists(&mut self) -> (HeapCellValue, HeapCellValue) {
         let iter = self
             .attr_var_init
             .bindings
             .iter()
-            .map(|(ref h, _)| HeapCellValue::Addr(Addr::AttrVar(*h)));
+            .map(|(ref h, _)| attr_var_as_cell!(*h));
 
-        let var_list_addr = Addr::HeapCell(self.heap.to_list(iter));
+        let var_list_addr = heap_loc_as_cell!(iter_to_heap_list(&mut self.heap, iter));
 
-        let iter = self
-            .attr_var_init
-            .bindings
-            .drain(0..)
-            .map(|(_, addr)| HeapCellValue::Addr(addr));
+        let iter = self.attr_var_init.bindings.drain(0..).map(|(_, ref v)| *v);
 
-        let value_list_addr = Addr::HeapCell(self.heap.to_list(iter));
+        let value_list_addr = heap_loc_as_cell!(iter_to_heap_list(&mut self.heap, iter));
         (var_list_addr, value_list_addr)
     }
 
     fn verify_attributes(&mut self) {
         for (h, _) in &self.attr_var_init.bindings {
-            self.heap[*h] = HeapCellValue::Addr(Addr::AttrVar(*h));
+            self.heap[*h] = attr_var_as_cell!(*h);
         }
 
         let (var_list_addr, value_list_addr) = self.populate_var_and_value_lists();
@@ -83,19 +81,26 @@ impl MachineState {
         self[temp_v!(2)] = value_list_addr;
     }
 
-    pub(super) fn gather_attr_vars_created_since(&self, b: usize) -> IntoIter<Addr> {
+    pub(super) fn gather_attr_vars_created_since(&mut self, b: usize) -> IntoIter<HeapCellValue> {
         let mut attr_vars: Vec<_> = self.attr_var_init.attr_var_queue[b..]
             .iter()
-            .filter_map(|h| match self.store(self.deref(Addr::HeapCell(*h))) {
-                Addr::AttrVar(h) => Some(Addr::AttrVar(h)),
-                _ => None,
+            .filter_map(|h| {
+                read_heap_cell!(self.store(self.deref(heap_loc_as_cell!(*h))), //Addr::HeapCell(*h))) {
+                    (HeapCellValueTag::AttrVar, h) => {
+                        Some(attr_var_as_cell!(h))
+                    }
+                    _ => {
+                        None
+                    }
+                )
             })
             .collect();
 
-        attr_vars
-            .sort_unstable_by(|a1, a2| self.compare_term_test(a1, a2).unwrap_or(Ordering::Less));
+        attr_vars.sort_unstable_by(|a1, a2| {
+	    compare_term_test!(self, *a1, *a2).unwrap_or(Ordering::Less)
+	});
 
-        self.term_dedup(&mut attr_vars);
+	attr_vars.dedup();
         attr_vars.into_iter()
     }
 
@@ -109,8 +114,10 @@ impl MachineState {
             self.stack.index_and_frame_mut(e)[i] = self[RegType::Temp(i)];
         }
 
-        self.stack.index_and_frame_mut(e)[self.num_of_args + 1] = Addr::CutPoint(self.b0);
-        self.stack.index_and_frame_mut(e)[self.num_of_args + 2] = Addr::Usize(self.num_of_args);
+        self.stack.index_and_frame_mut(e)[self.num_of_args + 1] =
+            fixnum_as_cell!(Fixnum::build_with(self.b0 as i64));
+        self.stack.index_and_frame_mut(e)[self.num_of_args + 2] =
+            fixnum_as_cell!(Fixnum::build_with(self.num_of_args as i64));
 
         self.verify_attributes();
 
@@ -119,33 +126,51 @@ impl MachineState {
         self.p = CodePtr::Local(LocalCodePtr::DirEntry(p));
     }
 
-    pub(super) fn attr_vars_of_term(&self, addr: Addr) -> Vec<Addr> {
+    pub(super) fn attr_vars_of_term(&mut self, cell: HeapCellValue) -> Vec<HeapCellValue> {
         let mut seen_set = IndexSet::new();
         let mut seen_vars = vec![];
 
-        let mut iter = self.acyclic_pre_order_iter(addr);
+        let mut iter = stackful_preorder_iter(&mut self.heap, cell);
 
-        while let Some(addr) = iter.next() {
-            if let HeapCellValue::Addr(Addr::AttrVar(h)) = self.heap.index_addr(&addr).as_ref() {
-                if seen_set.contains(h) {
-                    continue;
+        while let Some(value) = iter.next() {
+            read_heap_cell!(value,
+                (HeapCellValueTag::AttrVar, h) => {
+                    if seen_set.contains(&h) {
+                        continue;
+                    }
+
+                    seen_vars.push(value);
+                    seen_set.insert(h);
+
+                    let mut l = h + 1;
+                    // let mut list_elements = vec![];
+                    // let iter_stack_len = iter.stack_len();
+
+                    loop {
+                        read_heap_cell!(iter.heap[l],
+                            (HeapCellValueTag::Lis) => {
+                                iter.push_stack(l);
+                                // l = elem + 1;
+                                break;
+                            }
+                            (HeapCellValueTag::Var | HeapCellValueTag::AttrVar, h) => {
+                                if h == l {
+                                    break;
+                                } else {
+                                    l = h;
+                                }
+                            }
+                            _ => {
+                                break;
+                            }
+                        )
+                    }
+
+                    // iter.stack_slice_from(iter_stack_len ..).reverse();
                 }
-
-                seen_vars.push(addr);
-                seen_set.insert(*h);
-
-                let mut l = h + 1;
-                let mut list_elements = vec![];
-
-                while let Addr::Lis(elem) = self.store(self.deref(Addr::HeapCell(l))) {
-                    list_elements.push(self.heap[elem].as_addr(elem));
-                    l = elem + 1;
+                _ => {
                 }
-
-                for element in list_elements.into_iter().rev() {
-                    iter.stack().push(element);
-                }
-            }
+            );
         }
 
         seen_vars

src/machine/code_repo.rs

@@ -3,7 +3,7 @@ use crate::instructions::*;
 use crate::machine::machine_indices::*;
 
 #[derive(Debug)]
-pub(crate) struct CodeRepo {
+pub struct CodeRepo {
     pub(super) code: Code,
 }
 

src/machine/copier.rs

@@ -1,5 +1,6 @@
-use crate::machine::machine_indices::*;
+use crate::atom_table::*;
 use crate::machine::stack::*;
+use crate::types::*;
 
 use std::mem;
 use std::ops::IndexMut;
@@ -7,20 +8,24 @@ use std::ops::IndexMut;
 type Trail = Vec<(Ref, HeapCellValue)>;
 
 #[derive(Debug, Clone, Copy)]
-pub(crate) enum AttrVarPolicy {
+pub enum AttrVarPolicy {
     DeepCopy,
     StripAttributes,
 }
 
-pub(crate) trait CopierTarget: IndexMut<usize, Output = HeapCellValue> {
-    fn deref(&self, val: Addr) -> Addr;
-    fn push(&mut self, val: HeapCellValue);
+pub trait CopierTarget: IndexMut<usize, Output = HeapCellValue> {
+    fn store(&self, value: HeapCellValue) -> HeapCellValue;
+    fn deref(&self, value: HeapCellValue) -> HeapCellValue;
+    fn push(&mut self, value: HeapCellValue);
     fn stack(&mut self) -> &mut Stack;
-    fn store(&self, val: Addr) -> Addr;
     fn threshold(&self) -> usize;
 }
 
-pub(crate) fn copy_term<T: CopierTarget>(target: T, addr: Addr, attr_var_policy: AttrVarPolicy) {
+pub(crate) fn copy_term<T: CopierTarget>(
+    target: T,
+    addr: HeapCellValue,
+    attr_var_policy: AttrVarPolicy,
+) {
     let mut copy_term_state = CopyTermState::new(target, attr_var_policy);
     copy_term_state.copy_term_impl(addr);
 }
@@ -47,50 +52,51 @@ impl<T: CopierTarget> CopyTermState<T> {
 
     #[inline]
     fn value_at_scan(&mut self) -> &mut HeapCellValue {
-        let scan = self.scan;
-        &mut self.target[scan]
+        &mut self.target[self.scan]
     }
 
     fn trail_list_cell(&mut self, addr: usize, threshold: usize) {
-        let trail_item = mem::replace(
-            &mut self.target[addr],
-            HeapCellValue::Addr(Addr::Lis(threshold)),
-        );
-
-        self.trail.push((Ref::HeapCell(addr), trail_item));
+        let trail_item = mem::replace(&mut self.target[addr], list_loc_as_cell!(threshold));
+        self.trail.push((Ref::heap_cell(addr), trail_item));
     }
 
     fn copy_list(&mut self, addr: usize) {
         for offset in 0..2 {
-            if let Addr::Lis(h) = self.target[addr + offset].as_addr(addr + offset) {
-                if h >= self.old_h {
-                    *self.value_at_scan() = HeapCellValue::Addr(Addr::Lis(h));
-                    self.scan += 1;
+            read_heap_cell!(self.target[addr + offset],
+                (HeapCellValueTag::Lis, h) => {
+                    if h >= self.old_h {
+                        *self.value_at_scan() = list_loc_as_cell!(h);
+                        self.scan += 1;
 
-                    return;
+                        return;
+                    }
                 }
-            }
+                _ => {
+                }
+            )
         }
 
         let threshold = self.target.threshold();
 
-        *self.value_at_scan() = HeapCellValue::Addr(Addr::Lis(threshold));
+        *self.value_at_scan() = list_loc_as_cell!(threshold);
 
         for i in 0..2 {
-            let hcv = self.target[addr + i].context_free_clone();
+            let hcv = self.target[addr + i];
             self.target.push(hcv);
         }
 
         let cdr = self
             .target
-            .store(self.target.deref(Addr::HeapCell(addr + 1)));
+            .store(self.target.deref(heap_loc_as_cell!(addr + 1)));
 
-        if !cdr.is_ref() {
+        if !cdr.is_var() {
             self.trail_list_cell(addr + 1, threshold);
         } else {
-            let car = self.target.store(self.target.deref(Addr::HeapCell(addr)));
+            let car = self
+                .target
+                .store(self.target.deref(heap_loc_as_cell!(addr)));
 
-            if !car.is_ref() {
+            if !car.is_var() {
                 self.trail_list_cell(addr, threshold);
             }
         }
@@ -98,187 +104,208 @@ impl<T: CopierTarget> CopyTermState<T> {
         self.scan += 1;
     }
 
-    fn copy_partial_string(&mut self, addr: usize, n: usize) {
-        if let &HeapCellValue::Addr(Addr::PStrLocation(h, _)) = &self.target[addr] {
-            if h >= self.old_h {
-                *self.value_at_scan() = HeapCellValue::Addr(Addr::PStrLocation(h, n));
-                self.scan += 1;
+    fn copy_partial_string(&mut self, scan_tag: HeapCellValueTag, pstr_loc: usize) {
+        read_heap_cell!(self.target[pstr_loc],
+            (HeapCellValueTag::PStrLoc, h) => {
+                if h >= self.old_h {
+                    *self.value_at_scan() = match scan_tag {
+                        HeapCellValueTag::PStrLoc => {
+                            pstr_loc_as_cell!(h)
+                        }
+                        tag => {
+                            debug_assert!(tag == HeapCellValueTag::PStrOffset);
+                            pstr_offset_as_cell!(h)
+                        }
+                    };
 
-                return;
+                    self.scan += 1;
+                    return;
+                }
             }
-        }
+            _ => {}
+        );
 
         let threshold = self.target.threshold();
 
-        *self.value_at_scan() = HeapCellValue::Addr(Addr::PStrLocation(threshold, n));
-
+        *self.value_at_scan() = pstr_loc_as_cell!(threshold);
         self.scan += 1;
 
-        let (pstr, has_tail) = match &self.target[addr] {
-            &HeapCellValue::PartialString(ref pstr, has_tail) => {
-                (pstr.clone_from_offset(0), has_tail)
-            }
-            _ => {
-                unreachable!()
-            }
-        };
+        self.target.push(self.target[pstr_loc]);
 
-        self.target
-            .push(HeapCellValue::PartialString(pstr, has_tail));
+        let replacement = pstr_loc_as_cell!(threshold);
+        let trail_item = mem::replace(&mut self.target[pstr_loc], replacement);
 
-        let replacement = HeapCellValue::Addr(Addr::PStrLocation(threshold, n));
-
-        let trail_item = mem::replace(&mut self.target[addr], replacement);
-
-        self.trail.push((Ref::HeapCell(addr), trail_item));
-
-        if has_tail {
-            let tail_addr = self.target[addr + 1].as_addr(addr + 1);
-            self.target.push(HeapCellValue::Addr(tail_addr));
-        }
+        self.trail.push((Ref::heap_cell(pstr_loc), trail_item));
+        self.target.push(self.target[pstr_loc + 1]);
     }
 
-    fn reinstantiate_var(&mut self, addr: Addr, frontier: usize) {
-        match addr {
-            Addr::HeapCell(h) => {
-                self.target[frontier] = HeapCellValue::Addr(Addr::HeapCell(frontier));
-                self.target[h] = HeapCellValue::Addr(Addr::HeapCell(frontier));
+    fn reinstantiate_var(&mut self, addr: HeapCellValue, frontier: usize) {
+        read_heap_cell!(addr,
+            (HeapCellValueTag::Var, h) => {
+                self.target[frontier] = heap_loc_as_cell!(frontier);
+                self.target[h] = heap_loc_as_cell!(frontier);
 
-                self.trail
-                    .push((Ref::HeapCell(h), HeapCellValue::Addr(Addr::HeapCell(h))));
+                self.trail.push((Ref::heap_cell(h), heap_loc_as_cell!(h)));
             }
-            Addr::StackCell(fr, sc) => {
-                self.target[frontier] = HeapCellValue::Addr(Addr::HeapCell(frontier));
-                self.target.stack().index_and_frame_mut(fr)[sc] = Addr::HeapCell(frontier);
+            (HeapCellValueTag::StackVar, s) => {
+                self.target[frontier] = heap_loc_as_cell!(frontier);
+                self.target.stack()[s] = heap_loc_as_cell!(frontier);
 
-                self.trail.push((
-                    Ref::StackCell(fr, sc),
-                    HeapCellValue::Addr(Addr::StackCell(fr, sc)),
-                ));
+                self.trail.push((Ref::stack_cell(s), stack_loc_as_cell!(s)));
             }
-            Addr::AttrVar(h) => {
+            (HeapCellValueTag::AttrVar, h) => {
                 let threshold = if let AttrVarPolicy::DeepCopy = self.attr_var_policy {
                     self.target.threshold()
                 } else {
                     frontier
                 };
 
-                self.target[frontier] = HeapCellValue::Addr(Addr::HeapCell(threshold));
-                self.target[h] = HeapCellValue::Addr(Addr::HeapCell(threshold));
+                self.target[frontier] = heap_loc_as_cell!(threshold);
+                self.target[h] = heap_loc_as_cell!(threshold);
 
-                self.trail
-                    .push((Ref::AttrVar(h), HeapCellValue::Addr(Addr::AttrVar(h))));
+                self.trail.push((Ref::attr_var(h), attr_var_as_cell!(h)));
 
                 if let AttrVarPolicy::DeepCopy = self.attr_var_policy {
                     self.target
-                        .push(HeapCellValue::Addr(Addr::AttrVar(threshold)));
+                        .push(attr_var_as_cell!(threshold));
 
-                    let list_val = self.target[h + 1].context_free_clone();
+                    let list_val = self.target[h + 1];
                     self.target.push(list_val);
                 }
             }
             _ => {
                 unreachable!()
             }
+        );
+    }
+
+    fn copy_var(&mut self, addr: HeapCellValue) {
+        let rd = self.target.deref(addr);
+        let ra = self.target.store(rd);
+
+        read_heap_cell!(ra,
+            (HeapCellValueTag::AttrVar | HeapCellValueTag::Var, h) => {
+                if h >= self.old_h {
+                    *self.value_at_scan() = rd;
+                    self.scan += 1;
+
+                    return;
+                }
+            }
+            _ => {}
+        );
+
+        if addr == ra {
+            self.reinstantiate_var(addr, self.scan);
+            self.scan += 1;
+        } else {
+            *self.value_at_scan() = ra;
+            // self.copy_compound(rd, ra);
         }
     }
 
-    fn copy_var(&mut self, addr: Addr) {
-        let rd = self.target.store(self.target.deref(addr));
+    /*
+    fn copy_compound(&mut self, rd: HeapCellValue, ra: HeapCellValue) {
+        let h = rd.get_value();
+        let trail_item = self.target[h];
+        let threshold = self.target.threshold();
 
-        match rd {
-            Addr::AttrVar(h) | Addr::HeapCell(h) if h >= self.old_h => {
-                *self.value_at_scan() = HeapCellValue::Addr(rd);
-                self.scan += 1;
+        self.trail.push((Ref::heap_cell(h), trail_item));
+        self.target[self.scan].set_value(threshold);
+
+        read_heap_cell!(ra,
+            (HeapCellValueTag::Atom, (_name, arity)) => {
+                self.target.push(ra);
+
+                for i in 0..arity {
+                    self.target.push(self.target[h + 1 + i]);
+                }
+
+                self.target[h] = str_loc_as_cell!(self.scan + 1);
             }
-            _ if addr == rd => {
-                self.reinstantiate_var(addr, self.scan);
-                self.scan += 1;
+            (HeapCellValueTag::PStr | HeapCellValueTag::PStrOffset) => {
+                self.target.push(ra);
+                self.target.push(self.target[h + 1]);
+
+                self.target[h] = pstr_loc_as_cell!(self.scan + 1);
+            }
+            (HeapCellValueTag::CStr, cstr_atom) => {
+                self.target[h] = atom_as_cstr_cell!(cstr_atom);
+            }
+            (HeapCellValueTag::Str, s) => {
+                self.copy_structure(s);
+                return;
             }
             _ => {
-                *self.value_at_scan() = HeapCellValue::Addr(rd);
+                *self.value_at_scan() = rd;
+                self.trail.pop();
+                return;
             }
-        }
+        );
+
+        self.scan += 1;
     }
+    */
 
     fn copy_structure(&mut self, addr: usize) {
-        match self.target[addr].context_free_clone() {
-            HeapCellValue::NamedStr(arity, name, fixity) => {
+        read_heap_cell!(self.target[addr],
+            (HeapCellValueTag::Atom, (name, arity)) => {
                 let threshold = self.target.threshold();
 
-                *self.value_at_scan() = HeapCellValue::Addr(Addr::Str(threshold));
+                *self.value_at_scan() = str_loc_as_cell!(threshold);
 
                 let trail_item = mem::replace(
                     &mut self.target[addr],
-                    HeapCellValue::Addr(Addr::Str(threshold)),
+                    str_loc_as_cell!(threshold),
                 );
 
-                self.trail.push((Ref::HeapCell(addr), trail_item));
-
-                self.target
-                    .push(HeapCellValue::NamedStr(arity, name, fixity));
+                self.trail.push((Ref::heap_cell(addr), trail_item));
+                self.target.push(atom_as_cell!(name, arity));
 
                 for i in 0..arity {
-                    let hcv = self.target[addr + 1 + i].context_free_clone();
+                    let hcv = self.target[addr + 1 + i];
                     self.target.push(hcv);
                 }
             }
-            HeapCellValue::Addr(Addr::Str(addr)) => {
-                *self.value_at_scan() = HeapCellValue::Addr(Addr::Str(addr))
+            (HeapCellValueTag::Str, h) => {
+                *self.value_at_scan() = str_loc_as_cell!(h);
             }
             _ => {
                 unreachable!()
             }
-        }
+        );
 
         self.scan += 1;
     }
 
-    fn copy_term_impl(&mut self, addr: Addr) {
+    fn copy_term_impl(&mut self, addr: HeapCellValue) {
         self.scan = self.target.threshold();
-        self.target.push(HeapCellValue::Addr(addr));
+        self.target.push(addr);
 
         while self.scan < self.target.threshold() {
-            match self.value_at_scan() {
-                &mut HeapCellValue::Addr(addr) => match addr {
-                    Addr::Con(h) => {
-                        let addr = self.target[h].as_addr(h);
+            let addr = *self.value_at_scan();
 
-                        if addr == Addr::Con(h) {
-                            *self.value_at_scan() = self.target[h].context_free_clone();
-                        } else {
-                            *self.value_at_scan() = HeapCellValue::Addr(addr);
-                        }
-                    }
-                    Addr::Lis(h) => {
-                        if h >= self.old_h {
-                            self.scan += 1;
-                        } else {
-                            self.copy_list(h);
-                        }
-                    }
-                    addr @ Addr::AttrVar(_)
-                    | addr @ Addr::HeapCell(_)
-                    | addr @ Addr::StackCell(..) => {
-                        self.copy_var(addr);
-                    }
-                    Addr::Str(addr) => {
-                        self.copy_structure(addr);
-                    }
-                    Addr::PStrLocation(addr, n) => {
-                        self.copy_partial_string(addr, n);
-                    }
-                    Addr::Stream(h) => {
-                        *self.value_at_scan() = self.target[h].context_free_clone();
-                    }
-                    _ => {
+            read_heap_cell!(addr,
+                (HeapCellValueTag::Lis, h) => {
+                    if h >= self.old_h {
                         self.scan += 1;
+                    } else {
+                        self.copy_list(h);
                     }
-                },
+                }
+                (HeapCellValueTag::AttrVar | HeapCellValueTag::Var) => {
+                    self.copy_var(addr);
+                }
+                (HeapCellValueTag::Str, h) => {
+                    self.copy_structure(h);
+                }
+                (HeapCellValueTag::PStrLoc | HeapCellValueTag::PStrOffset, pstr_loc) => {
+                    self.copy_partial_string(addr.get_tag(), pstr_loc);
+                }
                 _ => {
                     self.scan += 1;
                 }
-            }
+            );
         }
 
         self.unwind_trail();
@@ -286,12 +313,117 @@ impl<T: CopierTarget> CopyTermState<T> {
 
     fn unwind_trail(&mut self) {
         for (r, value) in self.trail.drain(0..) {
-            match r {
-                Ref::AttrVar(h) | Ref::HeapCell(h) => self.target[h] = value,
-                Ref::StackCell(fr, sc) => {
-                    self.target.stack().index_and_frame_mut(fr)[sc] = value.as_addr(0)
-                }
+            let index = r.get_value() as usize;
+
+            match r.get_tag() {
+                RefTag::AttrVar | RefTag::HeapCell => self.target[index] = value,
+                RefTag::StackCell => self.target.stack()[index] = value,
             }
         }
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use crate::machine::mock_wam::*;
+
+    #[test]
+    fn copier_tests() {
+        let mut wam = MockWAM::new();
+
+        let f_atom = atom!("f");
+        let a_atom = atom!("a");
+        let b_atom = atom!("b");
+
+        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));
+        assert_eq!(wam.machine_st.heap[1], atom_as_cell!(a_atom));
+        assert_eq!(wam.machine_st.heap[2], atom_as_cell!(b_atom));
+
+        {
+            let wam = TermCopyingMockWAM { wam: &mut wam };
+            copy_term(wam, str_loc_as_cell!(0), AttrVarPolicy::DeepCopy);
+        }
+
+        // check that the original heap state is still intact.
+        assert_eq!(wam.machine_st.heap[0], atom_as_cell!(f_atom, 2));
+        assert_eq!(wam.machine_st.heap[1], atom_as_cell!(a_atom));
+        assert_eq!(wam.machine_st.heap[2], atom_as_cell!(b_atom));
+
+        assert_eq!(wam.machine_st.heap[3], str_loc_as_cell!(4));
+        assert_eq!(wam.machine_st.heap[4], atom_as_cell!(f_atom, 2));
+        assert_eq!(wam.machine_st.heap[5], atom_as_cell!(a_atom));
+        assert_eq!(wam.machine_st.heap[6], atom_as_cell!(b_atom));
+
+        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_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_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_offset_as_cell!(0));
+        wam.machine_st.heap.push(fixnum_as_cell!(Fixnum::build_with(0i64)));
+
+        {
+            let wam = TermCopyingMockWAM { wam: &mut wam };
+            copy_term(wam, pstr_loc_as_cell!(0), AttrVarPolicy::DeepCopy);
+        }
+
+        print_heap_terms(wam.machine_st.heap[6..].iter(), 6);
+
+        assert_eq!(wam.machine_st.heap[0], pstr_cell);
+        assert_eq!(wam.machine_st.heap[1], pstr_loc_as_cell!(2));
+        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[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)));
+
+        wam.machine_st.heap.clear();
+
+        wam.machine_st.heap.extend(functor!(
+            f_atom,
+            [
+                atom(a_atom),
+                atom(b_atom),
+                atom(a_atom),
+                cell(str_loc_as_cell!(0))
+            ]
+        ));
+
+        {
+            let wam = TermCopyingMockWAM { wam: &mut wam };
+            copy_term(wam, str_loc_as_cell!(0), AttrVarPolicy::DeepCopy);
+        }
+
+        assert_eq!(wam.machine_st.heap[0], atom_as_cell!(f_atom, 4));
+        assert_eq!(wam.machine_st.heap[1], atom_as_cell!(a_atom));
+        assert_eq!(wam.machine_st.heap[2], atom_as_cell!(b_atom));
+        assert_eq!(wam.machine_st.heap[3], atom_as_cell!(a_atom));
+        assert_eq!(wam.machine_st.heap[4], str_loc_as_cell!(0));
+
+        assert_eq!(wam.machine_st.heap[5], str_loc_as_cell!(6));
+        assert_eq!(wam.machine_st.heap[6], atom_as_cell!(f_atom, 4));
+        assert_eq!(wam.machine_st.heap[7], atom_as_cell!(a_atom));
+        assert_eq!(wam.machine_st.heap[8], atom_as_cell!(b_atom));
+        assert_eq!(wam.machine_st.heap[9], atom_as_cell!(a_atom));
+        assert_eq!(wam.machine_st.heap[10], str_loc_as_cell!(6));
+    }
+}

src/machine/heap.rs

@@ -1,140 +1,282 @@
-use core::marker::PhantomData;
-
-use prolog_parser::ast::Constant;
-
+use crate::arena::*;
+use crate::atom_table::*;
+use crate::forms::*;
 use crate::machine::machine_indices::*;
 use crate::machine::partial_string::*;
-use crate::machine::raw_block::*;
+use crate::parser::ast::*;
+use crate::types::*;
+
+use ordered_float::OrderedFloat;
+use rug::{Integer, Rational};
 
 use std::convert::TryFrom;
-use std::mem;
-use std::ops::{Index, IndexMut};
-use std::ptr;
 
-#[derive(Debug)]
-pub(crate) struct StandardHeapTraits {}
+pub(crate) type Heap = Vec<HeapCellValue>;
 
-impl RawBlockTraits for StandardHeapTraits {
+impl From<Literal> for HeapCellValue {
     #[inline]
-    fn init_size() -> usize {
-        256 * mem::size_of::<HeapCellValue>()
-    }
-
-    #[inline]
-    fn align() -> usize {
-        mem::align_of::<HeapCellValue>()
-    }
-}
-
-#[derive(Debug)]
-pub(crate) struct HeapTemplate<T: RawBlockTraits> {
-    buf: RawBlock<T>,
-    _marker: PhantomData<HeapCellValue>,
-}
-
-pub(crate) type Heap = HeapTemplate<StandardHeapTraits>;
-
-impl<T: RawBlockTraits> Drop for HeapTemplate<T> {
-    fn drop(&mut self) {
-        self.clear();
-        self.buf.deallocate();
-    }
-}
-
-#[derive(Debug)]
-pub(crate) struct HeapIntoIter<T: RawBlockTraits> {
-    offset: usize,
-    buf: RawBlock<T>,
-}
-
-impl<T: RawBlockTraits> Drop for HeapIntoIter<T> {
-    fn drop(&mut self) {
-        let mut heap = HeapTemplate {
-            buf: self.buf.take(),
-            _marker: PhantomData,
-        };
-
-        heap.truncate(self.offset / mem::size_of::<HeapCellValue>());
-        heap.buf.deallocate();
-    }
-}
-
-impl<T: RawBlockTraits> Iterator for HeapIntoIter<T> {
-    type Item = HeapCellValue;
-
-    fn next(&mut self) -> Option<Self::Item> {
-        let ptr = self.buf.base as usize + self.offset;
-        self.offset += mem::size_of::<HeapCellValue>();
-
-        if ptr < self.buf.top as usize {
-            unsafe { Some(ptr::read(ptr as *const HeapCellValue)) }
-        } else {
-            None
+    fn from(literal: Literal) -> Self {
+        match literal {
+            Literal::Atom(name) => atom_as_cell!(name),
+            Literal::Char(c) => char_as_cell!(c),
+            Literal::Fixnum(n) => fixnum_as_cell!(n),
+            Literal::Integer(bigint_ptr) => {
+                typed_arena_ptr_as_cell!(bigint_ptr)
+            }
+            Literal::Rational(bigint_ptr) => {
+                typed_arena_ptr_as_cell!(bigint_ptr)
+            }
+            Literal::Float(f) => HeapCellValue::from(f),
+            Literal::String(s) => {
+                if s == atom!("") {
+                    empty_list_as_cell!()
+                } else {
+                    string_as_cstr_cell!(s)
+                }
+            }
         }
     }
 }
 
-#[derive(Debug)]
-pub(crate) struct HeapIter<'a, T: RawBlockTraits> {
-    offset: usize,
-    buf: &'a RawBlock<T>,
-}
+impl TryFrom<HeapCellValue> for Literal {
+    type Error = ();
 
-impl<'a, T: RawBlockTraits> HeapIter<'a, T> {
-    pub(crate) fn new(buf: &'a RawBlock<T>, offset: usize) -> Self {
-        HeapIter { buf, offset }
+    fn try_from(value: HeapCellValue) -> Result<Literal, ()> {
+        read_heap_cell!(value,
+            (HeapCellValueTag::Atom, (name, arity)) => {
+                if arity == 0 {
+                    Ok(Literal::Atom(name))
+                } else {
+                    Err(())
+                }
+            }
+            (HeapCellValueTag::Char, c) => {
+                Ok(Literal::Char(c))
+            }
+            (HeapCellValueTag::Fixnum, n) => {
+                Ok(Literal::Fixnum(n))
+            }
+            (HeapCellValueTag::F64, f) => {
+                Ok(Literal::Float(f))
+            }
+            (HeapCellValueTag::Cons, cons_ptr) => {
+                match_untyped_arena_ptr!(cons_ptr,
+                     (ArenaHeaderTag::Integer, n) => {
+                         Ok(Literal::Integer(n))
+                     }
+                     (ArenaHeaderTag::Rational, n) => {
+                         Ok(Literal::Rational(n))
+                     }
+                     _ => {
+                         Err(())
+                     }
+                )
+            }
+            (HeapCellValueTag::CStr, cstr_atom) => {
+                Ok(Literal::String(cstr_atom))
+            }
+            _ => {
+                Err(())
+            }
+        )
     }
 }
 
-impl<'a, T: RawBlockTraits> Iterator for HeapIter<'a, T> {
-    type Item = &'a HeapCellValue;
+// sometimes we need to dereference variables that are found only in
+// the heap without access to the full WAM (e.g., while detecting
+// cycles in terms), and which therefore may only point other cells in
+// the heap (thanks to the design of the WAM).
+pub fn heap_bound_deref(heap: &[HeapCellValue], mut value: HeapCellValue) -> HeapCellValue {
+    loop {
+        let new_value = read_heap_cell!(value,
+            (HeapCellValueTag::AttrVar | HeapCellValueTag::Var, h) => {
+                heap[h]
+            }
+            _ => {
+                value
+            }
+        );
 
-    fn next(&mut self) -> Option<Self::Item> {
-        let ptr = self.buf.base as usize + self.offset;
-        self.offset += mem::size_of::<HeapCellValue>();
-
-        if ptr < self.buf.top as usize {
-            unsafe { Some(&*(ptr as *const _)) }
-        } else {
-            None
+        if new_value != value && new_value.is_var() {
+            value = new_value;
+            continue;
         }
+
+        return value;
     }
 }
 
+pub fn heap_bound_store(heap: &[HeapCellValue], value: HeapCellValue) -> HeapCellValue {
+    read_heap_cell!(value,
+        (HeapCellValueTag::AttrVar | HeapCellValueTag::Var, h) => {
+            heap[h]
+        }
+        _ => {
+            value
+        }
+    )
+}
+
 #[allow(dead_code)]
-pub(crate) fn print_heap_terms<'a, I: Iterator<Item = &'a HeapCellValue>>(heap: I, h: usize) {
+pub fn print_heap_terms<'a, I: Iterator<Item = &'a HeapCellValue>>(heap: I, h: usize) {
     for (index, term) in heap.enumerate() {
-        println!("{} : {}", h + index, term);
+        println!("{} : {:?}", h + index, term);
     }
 }
 
-#[derive(Debug)]
-pub(crate) struct HeapIterMut<'a, T: RawBlockTraits> {
-    offset: usize,
-    buf: &'a mut RawBlock<T>,
-}
+#[inline]
+pub(crate) fn put_complete_string(
+    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.
 
-impl<'a, T: RawBlockTraits> HeapIterMut<'a, T> {
-    pub(crate) fn new(buf: &'a mut RawBlock<T>, offset: usize) -> Self {
-        HeapIterMut { buf, offset }
-    }
-}
-
-impl<'a, T: RawBlockTraits> Iterator for HeapIterMut<'a, T> {
-    type Item = &'a mut HeapCellValue;
-
-    fn next(&mut self) -> Option<Self::Item> {
-        let ptr = self.buf.base as usize + self.offset;
-        self.offset += mem::size_of::<HeapCellValue>();
-
-        if ptr < self.buf.top as usize {
-            unsafe { Some(&mut *(ptr as *mut _)) }
-        } else {
-            None
+            if heap.len() == h + 1 {
+                let pstr_atom = cell_as_atom!(heap[h]);
+                heap[h] = atom_as_cstr_cell!(pstr_atom);
+                heap_loc_as_cell!(h)
+            } else {
+                heap.push(empty_list_as_cell!());
+                pstr_loc_as_cell!(h)
+            }
+        }
+        None => {
+            empty_list_as_cell!()
         }
     }
 }
 
+#[inline]
+pub(crate) fn put_partial_string(
+    heap: &mut Heap,
+    s: &str,
+    atom_tbl: &mut AtomTable,
+) -> HeapCellValue {
+    match allocate_pstr(heap, s, atom_tbl) {
+        Some(h) => {
+            pstr_loc_as_cell!(h)
+        }
+        None => {
+            empty_list_as_cell!()
+        }
+    }
+}
+
+#[inline]
+pub(crate) fn allocate_pstr(
+    heap: &mut Heap,
+    mut src: &str,
+    atom_tbl: &mut AtomTable,
+) -> Option<usize> {
+    let orig_h = heap.len();
+
+    loop {
+        if src == "" {
+            return if orig_h == heap.len() {
+                None
+            } else {
+                let tail_h = heap.len() - 1;
+                heap[tail_h] = heap_loc_as_cell!(tail_h);
+
+                Some(orig_h)
+            };
+        }
+
+        let h = heap.len();
+
+        let (pstr, rest_src) = match PartialString::new(src, atom_tbl) {
+            Some(tuple) => tuple,
+            None => {
+                if src.len() > '\u{0}'.len_utf8() {
+                    src = &src['\u{0}'.len_utf8()..];
+                    continue;
+                } else if orig_h == h {
+                    return None;
+                } else {
+                    heap[h - 1] = heap_loc_as_cell!(h - 1);
+                    return Some(orig_h);
+                }
+            }
+        };
+
+        heap.push(string_as_pstr_cell!(pstr));
+
+        if rest_src != "" {
+            heap.push(pstr_loc_as_cell!(h + 2));
+            src = rest_src;
+        } else {
+            heap.push(heap_loc_as_cell!(h + 1));
+            return Some(orig_h);
+        }
+    }
+}
+
+pub fn filtered_iter_to_heap_list<SrcT: Into<HeapCellValue>>(
+    heap: &mut Heap,
+    values: impl Iterator<Item = SrcT>,
+    filter_fn: impl Fn(&Heap, HeapCellValue) -> bool,
+) -> usize {
+    let head_addr = heap.len();
+    let mut h = head_addr;
+
+    for value in values {
+        let value = value.into();
+
+        if filter_fn(heap, value) {
+            heap.push(list_loc_as_cell!(h + 1));
+            heap.push(value);
+
+            h += 2;
+        }
+    }
+
+    heap.push(empty_list_as_cell!());
+
+    head_addr
+}
+
+#[inline(always)]
+pub fn iter_to_heap_list<Iter, SrcT>(heap: &mut Heap, values: Iter) -> usize
+where
+    Iter: Iterator<Item = SrcT>,
+    SrcT: Into<HeapCellValue>,
+{
+    filtered_iter_to_heap_list(heap, values, |_, _| true)
+}
+
+pub(crate) fn to_local_code_ptr(heap: &Heap, addr: HeapCellValue) -> Option<LocalCodePtr> {
+    let extract_integer = |s: usize| -> Option<usize> {
+        match Number::try_from(heap[s]) {
+            Ok(Number::Fixnum(n)) => usize::try_from(n.get_num()).ok(),
+            Ok(Number::Integer(n)) => n.to_usize(),
+            _ => None,
+        }
+    };
+
+    read_heap_cell!(addr,
+        (HeapCellValueTag::Str, s) => {
+            let (name, arity) = cell_as_atom_cell!(heap[s]).get_name_and_arity();
+
+            if name == atom!("dir_entry") && arity == 1 {
+                extract_integer(s+1).map(LocalCodePtr::DirEntry)
+            } else {
+                panic!(
+                    "to_local_code_ptr crashed with p.i. {}/{}",
+                    name.as_str(),
+                    arity,
+                );
+            }
+        }
+        _ => {
+            None
+        }
+    )
+}
+
+/*
 impl<T: RawBlockTraits> HeapTemplate<T> {
     #[inline]
     pub(crate) fn new() -> Self {
@@ -144,67 +286,40 @@ impl<T: RawBlockTraits> HeapTemplate<T> {
         }
     }
 
-    #[inline]
-    pub(crate) fn clone(&self, h: usize) -> HeapCellValue {
-        match &self[h] {
-            &HeapCellValue::Addr(addr) => HeapCellValue::Addr(addr),
-            &HeapCellValue::Atom(ref name, ref op) => HeapCellValue::Atom(name.clone(), op.clone()),
-            &HeapCellValue::DBRef(ref db_ref) => HeapCellValue::DBRef(db_ref.clone()),
-            &HeapCellValue::Integer(ref n) => HeapCellValue::Integer(n.clone()),
-            &HeapCellValue::LoadStatePayload(_) => HeapCellValue::Addr(Addr::LoadStatePayload(h)),
-            &HeapCellValue::NamedStr(arity, ref name, ref op) => {
-                HeapCellValue::NamedStr(arity, name.clone(), op.clone())
-            }
-            &HeapCellValue::PartialString(..) => HeapCellValue::Addr(Addr::PStrLocation(h, 0)),
-            &HeapCellValue::Rational(ref r) => HeapCellValue::Rational(r.clone()),
-            &HeapCellValue::Stream(_) => HeapCellValue::Addr(Addr::Stream(h)),
-            &HeapCellValue::TcpListener(_) => HeapCellValue::Addr(Addr::TcpListener(h)),
-        }
-    }
-
-    #[inline]
-    pub(crate) fn put_complete_string(&mut self, s: &str) -> Addr {
-        if s.is_empty() {
-            return Addr::EmptyList;
-        }
-
-        let addr = self.allocate_pstr(s);
-        self.pop();
-
-        let h = self.h();
-
-        match &mut self[h - 1] {
-            &mut HeapCellValue::PartialString(_, ref mut has_tail) => {
-                *has_tail = false;
-            }
-            _ => {
-                unreachable!()
-            }
-        }
-
-        addr
-    }
-
-    #[inline]
-    pub(crate) fn put_constant(&mut self, c: Constant) -> Addr {
-        match c {
-            Constant::Atom(name, op) => Addr::Con(self.push(HeapCellValue::Atom(name, op))),
-            Constant::Char(c) => Addr::Char(c),
-            Constant::EmptyList => Addr::EmptyList,
-            Constant::Fixnum(n) => Addr::Fixnum(n),
-            Constant::Integer(n) => Addr::Con(self.push(HeapCellValue::Integer(n))),
-            Constant::Rational(r) => Addr::Con(self.push(HeapCellValue::Rational(r))),
-            Constant::Float(f) => Addr::Float(f),
-            Constant::String(s) => {
-                if s.is_empty() {
-                    Addr::EmptyList
-                } else {
-                    self.put_complete_string(&s)
+    /*
+        // TODO: move this to the WAM, then remove the temporary (and by
+        // then, unnecessary and impossible) "arena" argument. OR, remove
+        // this thing totally!  if we can. by that I mean, just convert a
+        // little to a HeapCellValue. don't bother writing to the
+        // heap at all. Each of these data is either already inlinable in a
+        // HeapCellValue or a pointer to an GC'ed location in memory.
+        #[inline]
+        pub(crate) fn put_literal(&mut self, literal: Literal) -> HeapCellValue {
+            match literal {
+                Literal::Atom(name) => atom_as_cell!(name),
+                Literal::Char(c) => char_as_cell!(c),
+                Literal::EmptyList => empty_list_as_cell!(),
+                Literal::Fixnum(n) => fixnum_as_cell!(n),
+                Literal::Integer(bigint_ptr) => {
+                    let h = self.push(typed_arena_ptr_as_cell!(bigint_ptr));
+                    self[h]
                 }
+                Literal::Rational(bigint_ptr) => {
+                    let h = self.push(typed_arena_ptr_as_cell!(bigint_ptr));
+                    self[h]
+                }
+                Literal::Float(f) => typed_arena_ptr_as_cell!(f),
+                Literal::String(s) => {
+                    if s.as_str().is_empty() {
+                        empty_list_as_cell!()
+                    } else {
+                        // TODO: how do we know where the tail is located?? well, there is no tail. separate tag?
+                        untyped_arena_ptr_as_cell!(s) // self.put_complete_string(arena, &s)
+                    }
+                } // Literal::Usize(n) => Addr::Usize(n),
             }
-            Constant::Usize(n) => Addr::Usize(n),
         }
-    }
+    */
 
     #[inline]
     pub(crate) fn is_empty(&self) -> bool {
@@ -225,14 +340,14 @@ impl<T: RawBlockTraits> HeapTemplate<T> {
         let h = self.h();
 
         unsafe {
-            let new_top = self.buf.new_block(mem::size_of::<HeapCellValue>());
-            ptr::write(self.buf.top as *mut _, val);
-            self.buf.top = new_top;
+            let new_ptr = self.buf.alloc(mem::size_of::<HeapCellValue>());
+            ptr::write(new_ptr as *mut _, val);
         }
 
         h
     }
 
+    /*
     #[inline]
     pub(crate) fn atom_at(&self, h: usize) -> bool {
         if let HeapCellValue::Atom(..) = &self[h] {
@@ -265,76 +380,17 @@ impl<T: RawBlockTraits> HeapTemplate<T> {
             val @ HeapCellValue::TcpListener(..) => Addr::TcpListener(self.push(val)),
         }
     }
-
-    #[inline]
-    pub(crate) fn allocate_pstr(&mut self, src: &str) -> Addr {
-        self.write_pstr(src).unwrap_or_else(|| Addr::EmptyList)
-    }
-
-    #[inline]
-    fn write_pstr(&mut self, mut src: &str) -> Option<Addr> {
-        let orig_h = self.h();
-
-        loop {
-            if src == "" {
-                return if orig_h == self.h() {
-                    None
-                } else {
-                    let tail_h = self.h() - 1;
-                    self[tail_h] = HeapCellValue::Addr(Addr::HeapCell(tail_h));
-
-                    Some(Addr::PStrLocation(orig_h, 0))
-                };
-            }
-
-            let h = self.h();
-
-            let (pstr, rest_src) = match PartialString::new(src) {
-                Some(tuple) => tuple,
-                None => {
-                    if src.len() > '\u{0}'.len_utf8() {
-                        src = &src['\u{0}'.len_utf8()..];
-                        continue;
-                    } else if orig_h == h {
-                        return None;
-                    } else {
-                        self[h - 1] = HeapCellValue::Addr(Addr::HeapCell(h - 1));
-                        return Some(Addr::PStrLocation(orig_h, 0));
-                    }
-                }
-            };
-
-            self.push(HeapCellValue::PartialString(pstr, true));
-
-            if rest_src != "" {
-                self.push(HeapCellValue::Addr(Addr::PStrLocation(h + 2, 0)));
-                src = rest_src;
-            } else {
-                self.push(HeapCellValue::Addr(Addr::HeapCell(h + 1)));
-                return Some(Addr::PStrLocation(orig_h, 0));
-            }
-        }
-    }
+    */
 
     #[inline]
     pub(crate) fn truncate(&mut self, h: usize) {
-        let new_top = h * mem::size_of::<HeapCellValue>() + self.buf.base as usize;
-        let mut h = new_top;
-
-        unsafe {
-            while h as *const _ < self.buf.top {
-                let val = h as *mut HeapCellValue;
-                ptr::drop_in_place(val);
-                h += mem::size_of::<HeapCellValue>();
-            }
-        }
-
-        self.buf.top = new_top as *const _;
+        let new_ptr = self.buf.top as usize - h * mem::size_of::<HeapCellValue>();
+        self.buf.ptr = new_ptr as *mut _;
     }
 
     #[inline]
     pub(crate) fn h(&self) -> usize {
-        (self.buf.top as usize - self.buf.base as usize) / mem::size_of::<HeapCellValue>()
+        (self.buf.top as usize - self.buf.ptr as usize) / mem::size_of::<HeapCellValue>()
     }
 
     pub(crate) fn append(&mut self, vals: Vec<HeapCellValue>) {
@@ -350,84 +406,7 @@ impl<T: RawBlockTraits> HeapTemplate<T> {
         }
     }
 
-    pub(crate) fn to_list<Iter, SrcT>(&mut self, values: Iter) -> usize
-    where
-        Iter: Iterator<Item = SrcT>,
-        SrcT: Into<HeapCellValue>,
-    {
-        let head_addr = self.h();
-        let mut h = head_addr;
-
-        for value in values.map(|v| v.into()) {
-            self.push(HeapCellValue::Addr(Addr::Lis(h + 1)));
-            self.push(value);
-
-            h += 2;
-        }
-
-        self.push(HeapCellValue::Addr(Addr::EmptyList));
-
-        head_addr
-    }
-
-    /* Create an iterator starting from the passed offset. */
-    pub(crate) fn iter_from<'a>(&'a self, offset: usize) -> HeapIter<'a, T> {
-        HeapIter::new(&self.buf, offset * mem::size_of::<HeapCellValue>())
-    }
-
-    pub(crate) fn iter_mut_from<'a>(&'a mut self, offset: usize) -> HeapIterMut<'a, T> {
-        HeapIterMut::new(&mut self.buf, offset * mem::size_of::<HeapCellValue>())
-    }
-
-    pub(crate) fn into_iter(mut self) -> HeapIntoIter<T> {
-        HeapIntoIter {
-            buf: self.buf.take(),
-            offset: 0,
-        }
-    }
-
-    pub(crate) fn extend<Iter: Iterator<Item = HeapCellValue>>(&mut self, iter: Iter) {
-        for hcv in iter {
-            self.push(hcv);
-        }
-    }
-
-    pub(crate) fn to_local_code_ptr(&self, addr: &Addr) -> Option<LocalCodePtr> {
-        let extract_integer = |s: usize| -> Option<usize> {
-            match &self[s] {
-                &HeapCellValue::Addr(Addr::Fixnum(n)) => usize::try_from(n).ok(),
-                &HeapCellValue::Integer(ref n) => n.to_usize(),
-                _ => None,
-            }
-        };
-
-        match addr {
-            Addr::Str(s) => {
-                match &self[*s] {
-                    HeapCellValue::NamedStr(arity, ref name, _) => {
-                        match (name.as_str(), *arity) {
-                            ("dir_entry", 1) => extract_integer(s + 1).map(LocalCodePtr::DirEntry),
-                            /*
-                            ("top_level", 2) => {
-                                if let Some(chunk_num) = extract_integer(s+1) {
-                                    if let Some(p) = extract_integer(s+2) {
-                                        return Some(LocalCodePtr::TopLevel(chunk_num, p));
-                                    }
-                                }
-
-                                None
-                            }
-                            */
-                            _ => None,
-                        }
-                    }
-                    _ => unreachable!(),
-                }
-            }
-            _ => None,
-        }
-    }
-
+    /* TODO: get rid of this!!
     #[inline]
     pub(crate) fn index_addr<'a>(&'a self, addr: &Addr) -> RefOrOwned<'a, HeapCellValue> {
         match addr {
@@ -437,6 +416,20 @@ impl<T: RawBlockTraits> HeapTemplate<T> {
             addr => RefOrOwned::Owned(HeapCellValue::Addr(*addr)),
         }
     }
+    */
+}
+
+impl<T: RawBlockTraits> Index<u64> for HeapTemplate<T> {
+    type Output = HeapCellValue;
+
+    #[inline]
+    fn index(&self, index: u64) -> &Self::Output {
+        unsafe {
+            let ptr =
+                self.buf.top as usize - (index as usize + 1) * mem::size_of::<HeapCellValue>();
+            &*(ptr as *const HeapCellValue)
+        }
+    }
 }
 
 impl<T: RawBlockTraits> Index<usize> for HeapTemplate<T> {
@@ -445,7 +438,7 @@ impl<T: RawBlockTraits> Index<usize> for HeapTemplate<T> {
     #[inline]
     fn index(&self, index: usize) -> &Self::Output {
         unsafe {
-            let ptr = self.buf.base as usize + index * mem::size_of::<HeapCellValue>();
+            let ptr = self.buf.top as usize - (index + 1) * mem::size_of::<HeapCellValue>();
             &*(ptr as *const HeapCellValue)
         }
     }
@@ -455,8 +448,9 @@ impl<T: RawBlockTraits> IndexMut<usize> for HeapTemplate<T> {
     #[inline]
     fn index_mut(&mut self, index: usize) -> &mut Self::Output {
         unsafe {
-            let ptr = self.buf.base as usize + index * mem::size_of::<HeapCellValue>();
+            let ptr = self.buf.top as usize - (index + 1) * mem::size_of::<HeapCellValue>();
             &mut *(ptr as *mut HeapCellValue)
         }
     }
 }
+*/

src/machine/machine_indices.rs

@@ -1,53 +1,43 @@
-use prolog_parser::ast::*;
-use prolog_parser::clause_name;
+use crate::parser::ast::*;
 
+use crate::arena::*;
+use crate::atom_table::*;
 use crate::clause_types::*;
 use crate::fixtures::*;
 use crate::forms::*;
 use crate::instructions::*;
+
 use crate::machine::code_repo::CodeRepo;
 use crate::machine::heap::*;
+use crate::machine::loader::*;
+use crate::machine::machine_errors::MachineStub;
 use crate::machine::machine_state::*;
-use crate::machine::partial_string::*;
-use crate::machine::raw_block::RawBlockTraits;
 use crate::machine::streams::Stream;
-use crate::machine::term_stream::LoadStatePayload;
-use crate::machine::CompilationTarget;
-use crate::rug::{Integer, Rational};
-use ordered_float::OrderedFloat;
 
 use indexmap::IndexMap;
 
 use std::cell::Cell;
 use std::cmp::Ordering;
-use std::collections::{BTreeMap, BTreeSet};
-use std::convert::TryFrom;
+use std::collections::BTreeSet;
 use std::fmt;
-// use std::mem;
-use std::net::TcpListener;
 use std::ops::{Add, AddAssign, Deref, Sub, SubAssign};
 use std::rc::Rc;
 
+use crate::types::*;
 #[derive(Debug, Clone, PartialEq, Eq, PartialOrd, Ord, Hash)]
-pub(crate) struct OrderedOpDirKey(pub(crate) ClauseName, pub(crate) Fixity);
+pub(crate) struct OrderedOpDirKey(pub(crate) Atom, pub(crate) Fixity);
 
-pub(crate) type OssifiedOpDir = BTreeMap<OrderedOpDirKey, (usize, Specifier)>;
+pub(crate) type OssifiedOpDir = IndexMap<(Atom, Fixity), (usize, Specifier)>;
 
-#[derive(Debug, Clone, PartialEq, Eq, Hash)]
-pub(crate) enum DBRef {
-    NamedPred(ClauseName, usize, Option<SharedOpDesc>),
-    Op(
-        usize,
-        Specifier,
-        ClauseName,
-        Rc<OssifiedOpDir>,
-        SharedOpDesc,
-    ),
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub enum DBRef {
+    NamedPred(Atom, usize),
+    Op(Atom, Fixity, TypedArenaPtr<OssifiedOpDir>),
 }
 
 // 7.2
 #[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord)]
-pub(crate) enum TermOrderCategory {
+pub enum TermOrderCategory {
     Variable,
     FloatingPoint,
     Integer,
@@ -55,43 +45,95 @@ pub(crate) enum TermOrderCategory {
     Compound,
 }
 
-#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
-pub(crate) enum Addr {
-    AttrVar(usize),
-    Char(char),
-    Con(usize),
-    CutPoint(usize),
-    EmptyList,
-    Fixnum(isize),
-    Float(OrderedFloat<f64>),
-    Lis(usize),
-    LoadStatePayload(usize),
-    HeapCell(usize),
-    PStrLocation(usize, usize), // location of pstr in heap, offset into string in bytes.
-    StackCell(usize, usize),
-    Str(usize),
-    Stream(usize),
-    TcpListener(usize),
-    Usize(usize),
-}
+// the position-dependent heap template:
 
-#[derive(Debug, Clone, Copy, Hash, Eq, PartialEq, PartialOrd)]
-pub(crate) enum Ref {
-    AttrVar(usize),
-    HeapCell(usize),
-    StackCell(usize, usize),
-}
+/*
+        read_heap_cell!(
+            (HeapCellValueTag::AttrVar, n) => {
+            }
+            (HeapCellValueTag::Lis, n) => {
+            }
+            (HeapCellValueTag::Var, n) => {
+            }
+            (HeapCellValueTag::Str, n) => {
+            }
+            (HeapCellValueTag::PStrOffset, n) => {
+            }
+            _ => {
+            }
+        )
+*/
 
-impl Ref {
-    pub(crate) fn as_addr(self) -> Addr {
-        match self {
-            Ref::AttrVar(h) => Addr::AttrVar(h),
-            Ref::HeapCell(h) => Addr::HeapCell(h),
-            Ref::StackCell(fr, sc) => Addr::StackCell(fr, sc),
-        }
+impl PartialEq<Ref> for HeapCellValue {
+    fn eq(&self, r: &Ref) -> bool {
+        self.as_var() == Some(*r)
     }
 }
 
+impl PartialOrd<Ref> for HeapCellValue {
+    fn partial_cmp(&self, r: &Ref) -> Option<Ordering> {
+        read_heap_cell!(*self,
+            (HeapCellValueTag::StackVar, s1) => {
+                match r.get_tag() {
+                    RefTag::StackCell => {
+                        let s2 = r.get_value() as usize;
+                        s1.partial_cmp(&s2)
+                    }
+                    _ => Some(Ordering::Greater),
+                }
+            }
+            (HeapCellValueTag::Var | HeapCellValueTag::AttrVar, h1) => {
+                match r.get_tag() {
+                    RefTag::StackCell => Some(Ordering::Less),
+                    _ => {
+                        let h2 = r.get_value() as usize;
+                        h1.partial_cmp(&h2)
+                    }
+                }
+            }
+            _ => {
+                None
+            }
+        )
+    }
+}
+/*
+impl HeapCellValue {
+    #[inline]
+    pub fn as_constant_index(self, machine_st: &MachineState) -> Option<Literal> {
+        read_heap_cell!(self,
+            (HeapCellValueTag::Char, c) => Some(Literal::Char(c)),
+            (HeapCellValueTag::Atom, (name, arity)) => {
+                if arity == 0 {
+                    Some(Literal::Atom(name))
+                } else {
+                    None
+                }
+            }
+            (HeapCellValueTag::Fixnum, n) => {
+                Some(Literal::Fixnum(n))
+            }
+            (HeapCellValueTag::F64, f) => {
+                Some(Literal::Float(f))
+            }
+            (HeapCellValueTag::Cons, ptr) => {
+                match_untyped_arena_ptr!(ptr,
+                     (ArenaHeaderTag::Integer, n) => {
+                         Some(Literal::Integer(n))
+                     }
+                     (ArenaHeaderTag::Rational, r) => {
+                         Some(Literal::Rational(r))
+                     }
+                     _ => {
+                         None
+                     }
+                )
+            }
+        )
+    }
+}
+*/
+/*
 impl Ord for Ref {
     fn cmp(&self, other: &Ref) -> Ordering {
         match (self, other) {
@@ -114,31 +156,6 @@ impl PartialEq<Ref> for Addr {
     }
 }
 
-// for use crate::in MachineState::bind.
-impl PartialOrd<Ref> for Addr {
-    fn partial_cmp(&self, r: &Ref) -> Option<Ordering> {
-        match self {
-            &Addr::StackCell(fr, sc) => match *r {
-                Ref::AttrVar(_) | Ref::HeapCell(_) => Some(Ordering::Greater),
-                Ref::StackCell(fr1, sc1) => {
-                    if fr1 < fr || (fr1 == fr && sc1 < sc) {
-                        Some(Ordering::Greater)
-                    } else if fr1 == fr && sc1 == sc {
-                        Some(Ordering::Equal)
-                    } else {
-                        Some(Ordering::Less)
-                    }
-                }
-            },
-            &Addr::HeapCell(h) | &Addr::AttrVar(h) => match r {
-                Ref::StackCell(..) => Some(Ordering::Less),
-                Ref::AttrVar(h1) | Ref::HeapCell(h1) => h.partial_cmp(h1),
-            },
-            _ => None,
-        }
-    }
-}
-
 impl Addr {
     #[inline]
     pub(crate) fn is_heap_bound(&self) -> bool {
@@ -171,57 +188,6 @@ impl Addr {
         }
     }
 
-    pub(super) fn order_category(&self, heap: &Heap) -> Option<TermOrderCategory> {
-        match Number::try_from((*self, heap)) {
-            Ok(Number::Integer(_)) | Ok(Number::Fixnum(_)) | Ok(Number::Rational(_)) => {
-                Some(TermOrderCategory::Integer)
-            }
-            Ok(Number::Float(_)) => Some(TermOrderCategory::FloatingPoint),
-            _ => match self {
-                Addr::HeapCell(_) | Addr::AttrVar(_) | Addr::StackCell(..) => {
-                    Some(TermOrderCategory::Variable)
-                }
-                Addr::Float(_) => Some(TermOrderCategory::FloatingPoint),
-                &Addr::Con(h) => match &heap[h] {
-                    HeapCellValue::Atom(..) => Some(TermOrderCategory::Atom),
-                    HeapCellValue::DBRef(_) => None,
-                    _ => {
-                        unreachable!()
-                    }
-                },
-                Addr::Char(_) | Addr::EmptyList => Some(TermOrderCategory::Atom),
-                Addr::Fixnum(_) | Addr::Usize(_) => Some(TermOrderCategory::Integer),
-                Addr::Lis(_) | Addr::PStrLocation(..) | Addr::Str(_) => {
-                    Some(TermOrderCategory::Compound)
-                }
-                Addr::CutPoint(_)
-                | Addr::LoadStatePayload(_)
-                | Addr::Stream(_)
-                | Addr::TcpListener(_) => None,
-            },
-        }
-    }
-
-    pub(crate) fn as_constant_index(&self, machine_st: &MachineState) -> Option<Constant> {
-        match self {
-            &Addr::Char(c) => Some(Constant::Char(c)),
-            &Addr::Con(h) => match &machine_st.heap[h] {
-                &HeapCellValue::Atom(ref name, _) if name.is_char() => {
-                    Some(Constant::Char(name.as_str().chars().next().unwrap()))
-                }
-                &HeapCellValue::Atom(ref name, _) => Some(Constant::Atom(name.clone(), None)),
-                &HeapCellValue::Integer(ref n) => Some(Constant::Integer(n.clone())),
-                &HeapCellValue::Rational(ref n) => Some(Constant::Rational(n.clone())),
-                _ => None,
-            },
-            &Addr::EmptyList => Some(Constant::EmptyList),
-            &Addr::Fixnum(n) => Some(Constant::Fixnum(n)),
-            &Addr::Float(f) => Some(Constant::Float(f)),
-            &Addr::Usize(n) => Some(Constant::Usize(n)),
-            _ => None,
-        }
-    }
-
     pub(crate) fn is_protected(&self, e: usize) -> bool {
         match self {
             &Addr::StackCell(addr, _) if addr >= e => false,
@@ -230,61 +196,6 @@ impl Addr {
     }
 }
 
-impl Add<usize> for Addr {
-    type Output = Addr;
-
-    fn add(self, rhs: usize) -> Self::Output {
-        match self {
-            Addr::Stream(h) => Addr::Stream(h + rhs),
-            Addr::Con(h) => Addr::Con(h + rhs),
-            Addr::Lis(a) => Addr::Lis(a + rhs),
-            Addr::AttrVar(h) => Addr::AttrVar(h + rhs),
-            Addr::HeapCell(h) => Addr::HeapCell(h + rhs),
-            Addr::Str(s) => Addr::Str(s + rhs),
-            Addr::PStrLocation(h, n) => Addr::PStrLocation(h + rhs, n),
-            _ => self,
-        }
-    }
-}
-
-impl Sub<i64> for Addr {
-    type Output = Addr;
-
-    fn sub(self, rhs: i64) -> Self::Output {
-        if rhs < 0 {
-            match self {
-                Addr::Stream(h) => Addr::Stream(h + rhs.abs() as usize),
-                Addr::Con(h) => Addr::Con(h + rhs.abs() as usize),
-                Addr::Lis(a) => Addr::Lis(a + rhs.abs() as usize),
-                Addr::AttrVar(h) => Addr::AttrVar(h + rhs.abs() as usize),
-                Addr::HeapCell(h) => Addr::HeapCell(h + rhs.abs() as usize),
-                Addr::Str(s) => Addr::Str(s + rhs.abs() as usize),
-                Addr::PStrLocation(h, n) => Addr::PStrLocation(h + rhs.abs() as usize, n),
-                _ => self,
-            }
-        } else {
-            self.sub(rhs as usize)
-        }
-    }
-}
-
-impl Sub<usize> for Addr {
-    type Output = Addr;
-
-    fn sub(self, rhs: usize) -> Self::Output {
-        match self {
-            Addr::Stream(h) => Addr::Stream(h - rhs),
-            Addr::Con(h) => Addr::Con(h - rhs),
-            Addr::Lis(a) => Addr::Lis(a - rhs),
-            Addr::AttrVar(h) => Addr::AttrVar(h - rhs),
-            Addr::HeapCell(h) => Addr::HeapCell(h - rhs),
-            Addr::Str(s) => Addr::Str(s - rhs),
-            Addr::PStrLocation(h, n) => Addr::PStrLocation(h - rhs, n),
-            _ => self,
-        }
-    }
-}
-
 impl SubAssign<usize> for Addr {
     fn sub_assign(&mut self, rhs: usize) {
         *self = self.clone() - rhs;
@@ -305,72 +216,9 @@ impl From<Ref> for TrailRef {
         TrailRef::Ref(r)
     }
 }
-
-#[derive(Debug)]
-pub(crate) enum HeapCellValue {
-    Addr(Addr),
-    Atom(ClauseName, Option<SharedOpDesc>),
-    DBRef(DBRef),
-    Integer(Rc<Integer>),
-    LoadStatePayload(Box<LoadStatePayload>),
-    NamedStr(usize, ClauseName, Option<SharedOpDesc>), // arity, name, precedence/Specifier if it has one.
-    Rational(Rc<Rational>),
-    PartialString(PartialString, bool), // the partial string, a bool indicating whether it came from a Constant.
-    Stream(Stream),
-    TcpListener(TcpListener),
-}
-
-impl HeapCellValue {
-    #[inline]
-    pub(crate) fn as_addr(&self, focus: usize) -> Addr {
-        match self {
-            HeapCellValue::Addr(ref a) => *a,
-            HeapCellValue::Atom(..)
-            | HeapCellValue::DBRef(..)
-            | HeapCellValue::Integer(..)
-            | HeapCellValue::Rational(..) => Addr::Con(focus),
-            HeapCellValue::LoadStatePayload(_) => Addr::LoadStatePayload(focus),
-            HeapCellValue::NamedStr(_, _, _) => Addr::Str(focus),
-            HeapCellValue::PartialString(..) => Addr::PStrLocation(focus, 0),
-            HeapCellValue::Stream(_) => Addr::Stream(focus),
-            HeapCellValue::TcpListener(_) => Addr::TcpListener(focus),
-        }
-    }
-
-    #[inline]
-    pub(crate) fn context_free_clone(&self) -> HeapCellValue {
-        match self {
-            &HeapCellValue::Addr(addr) => HeapCellValue::Addr(addr),
-            &HeapCellValue::Atom(ref name, ref op) => HeapCellValue::Atom(name.clone(), op.clone()),
-            &HeapCellValue::DBRef(ref db_ref) => HeapCellValue::DBRef(db_ref.clone()),
-            &HeapCellValue::Integer(ref n) => HeapCellValue::Integer(n.clone()),
-            &HeapCellValue::LoadStatePayload(_) => {
-                HeapCellValue::Atom(clause_name!("$live_term_stream"), None)
-            }
-            &HeapCellValue::NamedStr(arity, ref name, ref op) => {
-                HeapCellValue::NamedStr(arity, name.clone(), op.clone())
-            }
-            &HeapCellValue::Rational(ref r) => HeapCellValue::Rational(r.clone()),
-            &HeapCellValue::PartialString(ref pstr, has_tail) => {
-                HeapCellValue::PartialString(pstr.clone(), has_tail)
-            }
-            &HeapCellValue::Stream(ref stream) => HeapCellValue::Stream(stream.clone()),
-            &HeapCellValue::TcpListener(_) => {
-                HeapCellValue::Atom(clause_name!("$tcp_listener"), None)
-            }
-        }
-    }
-}
-
-impl From<Addr> for HeapCellValue {
-    #[inline]
-    fn from(value: Addr) -> HeapCellValue {
-        HeapCellValue::Addr(value)
-    }
-}
-
+*/
 #[derive(Debug, Clone, Copy, Eq, Hash, Ord, PartialEq, PartialOrd)]
-pub(crate) enum IndexPtr {
+pub enum IndexPtr {
     DynamicUndefined, // a predicate, declared as dynamic, whose location in code is as yet undefined.
     DynamicIndex(usize),
     Index(usize),
@@ -378,7 +226,7 @@ pub(crate) enum IndexPtr {
 }
 
 #[derive(Debug, Clone, Ord, PartialOrd, Eq, PartialEq)]
-pub(crate) struct CodeIndex(pub(crate) Rc<Cell<IndexPtr>>);
+pub struct CodeIndex(pub(crate) Rc<Cell<IndexPtr>>);
 
 impl Deref for CodeIndex {
     type Target = Cell<IndexPtr>;
@@ -419,7 +267,7 @@ impl Default for CodeIndex {
 }
 
 #[derive(Debug, Clone, Copy, PartialOrd, Ord, PartialEq, Eq)]
-pub(crate) enum REPLCodePtr {
+pub enum REPLCodePtr {
     AddDiscontiguousPredicate,
     AddDynamicPredicate,
     AddMultifilePredicate,
@@ -456,12 +304,11 @@ pub(crate) enum REPLCodePtr {
     AddNonCountedBacktracking,
 }
 
-#[derive(Debug, Clone, PartialEq)]
-pub(crate) enum CodePtr {
+#[derive(Debug, Clone, Copy, PartialEq)]
+pub enum CodePtr {
     BuiltInClause(BuiltInClauseType, LocalCodePtr), // local is the successor call.
     CallN(usize, LocalCodePtr, bool),               // arity, local, last call.
     Local(LocalCodePtr),
-    // DynamicTransaction(DynamicTransactionType, LocalCodePtr), // the type of transaction, the return pointer.
     REPL(REPLCodePtr, LocalCodePtr), // the REPL code, the return pointer.
     VerifyAttrInterrupt(usize), // location of the verify attribute interrupt code in the CodeDir.
 }
@@ -488,7 +335,7 @@ impl CodePtr {
 }
 
 #[derive(Copy, Clone, Debug, PartialEq)]
-pub(crate) enum LocalCodePtr {
+pub enum LocalCodePtr {
     DirEntry(usize), // offset
     Halt,
     IndexingBuf(usize, usize, usize), // DirEntry offset, first internal offset, second internal offset
@@ -496,7 +343,7 @@ pub(crate) enum LocalCodePtr {
 }
 
 impl LocalCodePtr {
-    pub(crate) fn assign_if_local(&mut self, cp: CodePtr) {
+    pub fn assign_if_local(&mut self, cp: CodePtr) {
         match cp {
             CodePtr::Local(local) => *self = local,
             _ => {}
@@ -504,7 +351,7 @@ impl LocalCodePtr {
     }
 
     #[inline]
-    pub(crate) fn abs_loc(&self) -> usize {
+    pub fn abs_loc(&self) -> usize {
         match self {
             LocalCodePtr::DirEntry(ref p) => *p,
             LocalCodePtr::IndexingBuf(ref p, ..) => *p,
@@ -528,33 +375,21 @@ impl LocalCodePtr {
         false
     }
 
-    pub(crate) fn as_functor<T: RawBlockTraits>(&self, heap: &mut HeapTemplate<T>) -> Addr {
-        let addr = Addr::HeapCell(heap.h());
-
+    pub(crate) fn as_functor(&self) -> MachineStub {
         match self {
             LocalCodePtr::DirEntry(p) => {
-                heap.append(functor!("dir_entry", [integer(*p)]));
+                functor!(atom!("dir_entry"), [fixnum(*p)])
             }
             LocalCodePtr::Halt => {
-                heap.append(functor!("halt"));
+                functor!(atom!("halt"))
             }
-            /*
-            LocalCodePtr::TopLevel(chunk_num, offset) => {
-                heap.append(functor!(
-                    "top_level",
-                    [integer(*chunk_num), integer(*offset)]
-                ));
-            }
-            */
             LocalCodePtr::IndexingBuf(p, o, i) => {
-                heap.append(functor!(
-                    "indexed_buf",
-                    [integer(*p), integer(*o), integer(*i)]
-                ));
+                functor!(
+                    atom!("indexed_buf"),
+                    [fixnum(*p), fixnum(*o), fixnum(*i)]
+                )
             }
         }
-
-        addr
     }
 }
 
@@ -614,9 +449,8 @@ impl AddAssign<usize> for LocalCodePtr {
     #[inline]
     fn add_assign(&mut self, rhs: usize) {
         match self {
-            &mut LocalCodePtr::DirEntry(ref mut p) /* |
-            &mut LocalCodePtr::TopLevel(_, ref mut p) */    => *p += rhs,
-            &mut LocalCodePtr::IndexingBuf(_, _, ref mut i) => *i += rhs,
+            &mut LocalCodePtr::DirEntry(ref mut i)
+            | &mut LocalCodePtr::IndexingBuf(_, _, ref mut i) => *i += rhs,
             &mut LocalCodePtr::Halt => unreachable!(),
         }
     }
@@ -627,11 +461,7 @@ impl Add<usize> for CodePtr {
 
     fn add(self, rhs: usize) -> Self::Output {
         match self {
-            p @ CodePtr::REPL(..) | p @ CodePtr::VerifyAttrInterrupt(_) => {
-                // |
-                // p @ CodePtr::DynamicTransaction(..) => {
-                p
-            }
+            p @ CodePtr::REPL(..) | p @ CodePtr::VerifyAttrInterrupt(_) => p,
             CodePtr::Local(local) => CodePtr::Local(local + rhs),
             CodePtr::BuiltInClause(_, local) | CodePtr::CallN(_, local, _) => {
                 CodePtr::Local(local + rhs)
@@ -660,12 +490,12 @@ impl SubAssign<usize> for CodePtr {
     }
 }
 
-pub(crate) type HeapVarDict = IndexMap<Rc<Var>, Addr>;
-pub(crate) type AllocVarDict = IndexMap<Rc<Var>, VarData>;
+pub(crate) type HeapVarDict = IndexMap<Rc<String>, HeapCellValue>;
+pub(crate) type AllocVarDict = IndexMap<Rc<String>, VarData>;
 
-pub(crate) type GlobalVarDir = IndexMap<ClauseName, (Ball, Option<Addr>)>;
+pub(crate) type GlobalVarDir = IndexMap<Atom, (Ball, Option<HeapCellValue>)>;
 
-pub(crate) type StreamAliasDir = IndexMap<ClauseName, Stream>;
+pub(crate) type StreamAliasDir = IndexMap<Atom, Stream>;
 pub(crate) type StreamDir = BTreeSet<Stream>;
 
 pub(crate) type MetaPredicateDir = IndexMap<PredicateKey, Vec<MetaSpec>>;
@@ -676,7 +506,7 @@ pub(crate) type LocalExtensiblePredicates =
     IndexMap<(CompilationTarget, PredicateKey), LocalPredicateSkeleton>;
 
 #[derive(Debug)]
-pub(crate) struct IndexStore {
+pub struct IndexStore {
     pub(super) code_dir: CodeDir,
     pub(super) extensible_predicates: ExtensiblePredicates,
     pub(super) local_extensible_predicates: LocalExtensiblePredicates,
@@ -688,31 +518,21 @@ pub(crate) struct IndexStore {
     pub(super) stream_aliases: StreamAliasDir,
 }
 
-impl Default for IndexStore {
-    #[inline]
-    fn default() -> Self {
-        index_store!(CodeDir::new(), default_op_dir(), ModuleDir::new())
-    }
-}
-
 impl IndexStore {
     pub(crate) fn get_predicate_skeleton_mut(
         &mut self,
         compilation_target: &CompilationTarget,
         key: &PredicateKey,
     ) -> Option<&mut PredicateSkeleton> {
-        match (key.0.as_str(), key.1) {
-            //            ("term_expansion", 2) => self.extensible_predicates.get_mut(key),
-            _ => match compilation_target {
-                CompilationTarget::User => self.extensible_predicates.get_mut(key),
-                CompilationTarget::Module(ref module_name) => {
-                    if let Some(module) = self.modules.get_mut(module_name) {
-                        module.extensible_predicates.get_mut(key)
-                    } else {
-                        None
-                    }
+        match compilation_target {
+            CompilationTarget::User => self.extensible_predicates.get_mut(key),
+            CompilationTarget::Module(ref module_name) => {
+                if let Some(module) = self.modules.get_mut(module_name) {
+                    module.extensible_predicates.get_mut(key)
+                } else {
+                    None
                 }
-            },
+            }
         }
     }
 
@@ -737,7 +557,7 @@ impl IndexStore {
         &mut self,
         mut src_compilation_target: CompilationTarget,
         local_compilation_target: CompilationTarget,
-        listing_src_file_name: Option<ClauseName>,
+        listing_src_file_name: Option<Atom>,
         key: PredicateKey,
     ) -> Option<&mut LocalPredicateSkeleton> {
         if let Some(filename) = listing_src_file_name {
@@ -748,8 +568,8 @@ impl IndexStore {
             CompilationTarget::User => self
                 .local_extensible_predicates
                 .get_mut(&(local_compilation_target, key)),
-            CompilationTarget::Module(ref module_name) => {
-                if let Some(module) = self.modules.get_mut(module_name) {
+            CompilationTarget::Module(module_name) => {
+                if let Some(module) = self.modules.get_mut(&module_name) {
                     module
                         .local_extensible_predicates
                         .get_mut(&(local_compilation_target, key))
@@ -764,7 +584,7 @@ impl IndexStore {
         &self,
         mut src_compilation_target: CompilationTarget,
         local_compilation_target: CompilationTarget,
-        listing_src_file_name: Option<ClauseName>,
+        listing_src_file_name: Option<Atom>,
         key: PredicateKey,
     ) -> Option<&LocalPredicateSkeleton> {
         if let Some(filename) = listing_src_file_name {
@@ -775,8 +595,8 @@ impl IndexStore {
             CompilationTarget::User => self
                 .local_extensible_predicates
                 .get(&(local_compilation_target, key)),
-            CompilationTarget::Module(ref module_name) => {
-                if let Some(module) = self.modules.get(module_name) {
+            CompilationTarget::Module(module_name) => {
+                if let Some(module) = self.modules.get(&module_name) {
                     module
                         .local_extensible_predicates
                         .get(&(local_compilation_target, key))
@@ -806,35 +626,30 @@ impl IndexStore {
 
     pub(crate) fn get_predicate_code_index(
         &self,
-        name: ClauseName,
+        name: Atom,
         arity: usize,
-        module: ClauseName,
-        op_spec: Option<SharedOpDesc>,
+        module: Atom,
     ) -> Option<CodeIndex> {
-        if module.as_str() == "user" {
-            match ClauseType::from(name, arity, op_spec) {
+        if module == atom!("user") {
+            match ClauseType::from(name, arity) {
                 ClauseType::Named(name, arity, _) => self.code_dir.get(&(name, arity)).cloned(),
-                ClauseType::Op(name, spec, ..) => self.code_dir.get(&(name, spec.arity())).cloned(),
                 _ => None,
             }
         } else {
-            self.modules.get(&module).and_then(|module| {
-                match ClauseType::from(name, arity, op_spec) {
+            self.modules
+                .get(&module)
+                .and_then(|module| match ClauseType::from(name, arity) {
                     ClauseType::Named(name, arity, _) => {
                         module.code_dir.get(&(name, arity)).cloned()
                     }
-                    ClauseType::Op(name, spec, ..) => {
-                        module.code_dir.get(&(name, spec.arity())).cloned()
-                    }
                     _ => None,
-                }
-            })
+                })
         }
     }
 
     pub(crate) fn get_meta_predicate_spec(
         &self,
-        name: ClauseName,
+        name: Atom,
         arity: usize,
         compilation_target: &CompilationTarget,
     ) -> Option<&Vec<MetaSpec>> {
@@ -850,9 +665,13 @@ impl IndexStore {
         }
     }
 
-    pub(crate) fn is_dynamic_predicate(&self, module_name: ClauseName, key: PredicateKey) -> bool {
-        match module_name.as_str() {
-            "user" => self
+    pub(crate) fn is_dynamic_predicate(
+        &self,
+        module_name: Atom,
+        key: PredicateKey,
+    ) -> bool {
+        match module_name {
+            atom!("user") => self
                 .extensible_predicates
                 .get(&key)
                 .map(|skeleton| skeleton.core.is_dynamic)
@@ -870,19 +689,19 @@ impl IndexStore {
 
     #[inline]
     pub(super) fn new() -> Self {
-        IndexStore::default()
+        index_store!(CodeDir::new(), default_op_dir(), ModuleDir::new())
     }
 
     pub(super) fn get_cleaner_sites(&self) -> (usize, usize) {
-        let r_w_h = clause_name!("run_cleaners_with_handling");
-        let r_wo_h = clause_name!("run_cleaners_without_handling");
-        let iso_ext = clause_name!("iso_ext");
+        let r_w_h = atom!("run_cleaners_with_handling");
+        let r_wo_h = atom!("run_cleaners_without_handling");
+        let iso_ext = atom!("iso_ext");
 
         let r_w_h = self
-            .get_predicate_code_index(r_w_h, 0, iso_ext.clone(), None)
+            .get_predicate_code_index(r_w_h, 0, iso_ext)
             .and_then(|item| item.local());
         let r_wo_h = self
-            .get_predicate_code_index(r_wo_h, 1, iso_ext, None)
+            .get_predicate_code_index(r_wo_h, 1, iso_ext)
             .and_then(|item| item.local());
 
         if let Some(r_w_h) = r_w_h {
@@ -895,7 +714,7 @@ impl IndexStore {
     }
 }
 
-pub(crate) type CodeDir = BTreeMap<PredicateKey, CodeIndex>;
+pub(crate) type CodeDir = IndexMap<PredicateKey, CodeIndex>;
 
 pub(crate) enum RefOrOwned<'a, T: 'a> {
     Borrowed(&'a T),
@@ -918,14 +737,4 @@ impl<'a, T> RefOrOwned<'a, T> {
             &RefOrOwned::Owned(ref r) => r,
         }
     }
-
-    pub(crate) fn to_owned(self) -> T
-    where
-        T: Clone,
-    {
-        match self {
-            RefOrOwned::Borrowed(item) => item.clone(),
-            RefOrOwned::Owned(item) => item,
-        }
-    }
 }

src/machine/mock_wam.rs

@@ -0,0 +1,766 @@
+pub use crate::arena::*;
+pub use crate::atom_table::*;
+use crate::heap_print::*;
+pub use crate::machine::heap::*;
+pub use crate::machine::Machine;
+pub use crate::machine::machine_state::*;
+pub use crate::machine::stack::*;
+pub use crate::machine::streams::*;
+pub use crate::macros::*;
+pub use crate::parser::ast::*;
+use crate::read::*;
+pub use crate::types::*;
+
+#[cfg(test)]
+use crate::machine::copier::CopierTarget;
+
+#[cfg(test)]
+use std::ops::{Deref, DerefMut, Index, IndexMut};
+
+// a mini-WAM for test purposes.
+
+pub struct MockWAM {
+    pub machine_st: MachineState,
+    pub op_dir: OpDir,
+    pub flags: MachineFlags,
+}
+
+impl MockWAM {
+    pub fn new() -> Self {
+        let op_dir = default_op_dir();
+
+        Self {
+            machine_st: MachineState::new(),
+            op_dir,
+            flags: MachineFlags::default(),
+        }
+    }
+
+    pub fn write_parsed_term_to_heap(
+        &mut self,
+        input_stream: Stream,
+    ) -> Result<TermWriteResult, ParserError> {
+        self.machine_st.read(input_stream, &self.op_dir)
+    }
+
+    pub fn parse_and_write_parsed_term_to_heap(
+        &mut self,
+        term_string: &'static str,
+    ) -> Result<TermWriteResult, ParserError> {
+        let stream = Stream::from_static_string(term_string, &mut self.machine_st.arena);
+        self.write_parsed_term_to_heap(stream)
+    }
+
+    pub fn parse_and_print_term(
+        &mut self,
+        term_string: &'static str,
+    ) -> Result<String, ParserError> {
+        let term_write_result = self.parse_and_write_parsed_term_to_heap(term_string)?;
+
+        print_heap_terms(self.machine_st.heap.iter(), term_write_result.heap_loc);
+
+        let mut printer = HCPrinter::new(
+            &mut self.machine_st.heap,
+            &mut self.machine_st.arena,
+            &self.op_dir,
+            PrinterOutputter::new(),
+            heap_loc_as_cell!(term_write_result.heap_loc),
+        );
+
+        printer.var_names = term_write_result
+            .var_dict
+            .into_iter()
+            .map(|(var, cell)| (cell, var))
+            .collect();
+
+        Ok(printer.print().result())
+    }
+}
+
+#[cfg(test)]
+pub struct TermCopyingMockWAM<'a> {
+    pub wam: &'a mut MockWAM,
+}
+
+#[cfg(test)]
+impl<'a> Index<usize> for TermCopyingMockWAM<'a> {
+    type Output = HeapCellValue;
+
+    fn index(&self, index: usize) -> &HeapCellValue {
+        &self.wam.machine_st.heap[index]
+    }
+}
+
+#[cfg(test)]
+impl<'a> IndexMut<usize> for TermCopyingMockWAM<'a> {
+    #[inline]
+    fn index_mut(&mut self, index: usize) -> &mut HeapCellValue {
+        &mut self.wam.machine_st.heap[index]
+    }
+}
+
+#[cfg(test)]
+impl<'a> Deref for TermCopyingMockWAM<'a> {
+    type Target = MockWAM;
+
+    fn deref(&self) -> &Self::Target {
+        &self.wam
+    }
+}
+
+#[cfg(test)]
+impl<'a> DerefMut for TermCopyingMockWAM<'a> {
+    fn deref_mut(&mut self) -> &mut Self::Target {
+        &mut self.wam
+    }
+}
+
+#[cfg(test)]
+impl<'a> CopierTarget for TermCopyingMockWAM<'a> {
+    fn store(&self, val: HeapCellValue) -> HeapCellValue {
+        read_heap_cell!(val,
+            (HeapCellValueTag::AttrVar | HeapCellValueTag::Var, h) => {
+                self.wam.machine_st.heap[h]
+            }
+            (HeapCellValueTag::StackVar, s) => {
+                self.wam.machine_st.stack[s]
+            }
+            _ => {
+                val
+            }
+        )
+    }
+
+    fn deref(&self, mut val: HeapCellValue) -> HeapCellValue {
+        loop {
+            let value = self.store(val);
+
+            if value.is_var() && value != val {
+                val = value;
+                continue;
+            }
+
+            return val;
+        }
+    }
+
+    fn push(&mut self, val: HeapCellValue) {
+        self.wam.machine_st.heap.push(val);
+    }
+
+    fn stack(&mut self) -> &mut Stack {
+        &mut self.wam.machine_st.stack
+    }
+
+    fn threshold(&self) -> usize {
+        self.wam.machine_st.heap.len()
+    }
+}
+
+#[cfg(test)]
+pub fn all_cells_marked_and_unforwarded(heap: &[HeapCellValue]) {
+    for (idx, cell) in heap.iter().enumerate() {
+        assert_eq!(
+            cell.get_mark_bit(),
+            true,
+            "cell {:?} at index {} is not marked",
+            cell,
+            idx
+        );
+        assert!(
+            cell.get_forwarding_bit() != Some(true),
+            "cell {:?} at index {} is forwarded",
+            cell,
+            idx
+        );
+    }
+}
+
+#[cfg(test)]
+pub fn all_cells_unmarked(heap: &Heap) {
+    for (idx, cell) in heap.iter().enumerate() {
+        assert!(
+            !cell.get_mark_bit(),
+            "cell {:?} at index {} is still marked",
+            cell,
+            idx
+        );
+
+        assert!(
+            cell.get_forwarding_bit() != Some(true),
+            "cell {:?} at index {} is still forwarded",
+            cell,
+            idx
+        );
+    }
+}
+
+#[cfg(test)]
+pub(crate) fn write_parsed_term_to_heap(
+    machine_st: &mut MachineState,
+    input_stream: Stream,
+    op_dir: &OpDir,
+) -> Result<TermWriteResult, ParserError> {
+    machine_st.read(input_stream, op_dir)
+}
+
+#[cfg(test)]
+pub(crate) fn parse_and_write_parsed_term_to_heap(
+    machine_st: &mut MachineState,
+    term_string: &'static str,
+    op_dir: &OpDir,
+) -> Result<TermWriteResult, ParserError> {
+    let stream = Stream::from_static_string(term_string, &mut machine_st.arena);
+    write_parsed_term_to_heap(machine_st, stream, op_dir)
+}
+
+impl Machine {
+    pub fn test_load_file(&mut self, file: &str) -> Vec<u8> {
+        use std::io::Read;
+
+        let old_output = std::mem::replace(
+            &mut self.user_output,
+            Stream::from_owned_string("".to_owned(), &mut self.machine_st.arena),
+        );
+
+        let stream = Stream::from_owned_string(
+            std::fs::read_to_string(AsRef::<std::path::Path>::as_ref(file)).unwrap(),
+            &mut self.machine_st.arena,
+        );
+
+        self.load_file(file.into(), stream);
+
+        let output = self.user_output.bytes().map(|b| b.unwrap()).collect();
+        self.user_output = old_output;
+        output
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn unify_tests() {
+        let mut wam = MachineState::new();
+        let mut op_dir = default_op_dir();
+
+        op_dir.insert(
+            (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(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();
+
+            let term_write_result_2 =
+                parse_and_write_parsed_term_to_heap(&mut wam, "f(b,a).", &op_dir).unwrap();
+
+            unify!(
+                wam,
+                str_loc_as_cell!(0),
+                str_loc_as_cell!(term_write_result_2.heap_loc)
+            );
+
+            assert!(wam.fail);
+        }
+
+        all_cells_unmarked(&wam.heap);
+
+        wam.fail = false;
+        wam.heap.clear();
+
+        {
+            parse_and_write_parsed_term_to_heap(&mut wam, "f(X,X).", &op_dir).unwrap();
+
+            let term_write_result_2 =
+                parse_and_write_parsed_term_to_heap(&mut wam, "f(b,b).", &op_dir).unwrap();
+
+            unify!(
+                wam,
+                str_loc_as_cell!(1),
+                heap_loc_as_cell!(term_write_result_2.heap_loc)
+            );
+
+            assert!(!wam.fail);
+        }
+
+        all_cells_unmarked(&wam.heap);
+
+        wam.fail = false;
+        wam.heap.clear();
+
+        {
+            parse_and_write_parsed_term_to_heap(&mut wam, "f(X,X).", &op_dir).unwrap();
+
+            let term_write_result_2 =
+                parse_and_write_parsed_term_to_heap(&mut wam, "f(f(A),Y).", &op_dir).unwrap();
+
+            unify!(
+                wam,
+                heap_loc_as_cell!(0),
+                heap_loc_as_cell!(term_write_result_2.heap_loc)
+            );
+
+            assert!(!wam.fail);
+        }
+
+        all_cells_unmarked(&wam.heap);
+
+        wam.fail = false;
+        wam.heap.clear();
+
+        {
+            parse_and_write_parsed_term_to_heap(&mut wam, "f(X,X).", &op_dir).unwrap();
+
+            let term_write_result_2 =
+                parse_and_write_parsed_term_to_heap(&mut wam, "f(f(A),Y).", &op_dir).unwrap();
+
+            unify!(
+                wam,
+                heap_loc_as_cell!(0),
+                heap_loc_as_cell!(term_write_result_2.heap_loc)
+            );
+
+            assert!(!wam.fail);
+        }
+
+        all_cells_unmarked(&wam.heap);
+
+        wam.fail = false;
+        wam.heap.clear();
+
+        {
+            parse_and_write_parsed_term_to_heap(&mut wam, "f(X,X).", &op_dir).unwrap();
+
+            let term_write_result_2 =
+                parse_and_write_parsed_term_to_heap(&mut wam, "f(f(A),A).", &op_dir).unwrap();
+
+            unify!(
+                wam,
+                heap_loc_as_cell!(0),
+                heap_loc_as_cell!(term_write_result_2.heap_loc)
+            );
+
+            assert!(!wam.fail);
+        }
+
+        all_cells_unmarked(&wam.heap);
+
+        wam.fail = false;
+        wam.heap.clear();
+
+        {
+            parse_and_write_parsed_term_to_heap(&mut wam, "f(X,X).", &op_dir).unwrap();
+
+            let term_write_result_2 =
+                parse_and_write_parsed_term_to_heap(&mut wam, "f(A,f(A)).", &op_dir).unwrap();
+
+            all_cells_unmarked(&wam.heap);
+
+            unify!(
+                wam,
+                heap_loc_as_cell!(0),
+                heap_loc_as_cell!(term_write_result_2.heap_loc)
+            );
+
+            assert!(!wam.fail);
+        }
+
+        all_cells_unmarked(&wam.heap);
+
+        wam.heap.clear();
+
+        wam.heap.push(pstr_as_cell!(atom!("this is a string")));
+        wam.heap.push(heap_loc_as_cell!(1));
+
+        wam.heap.push(pstr_as_cell!(atom!("this is a string")));
+        wam.heap.push(pstr_loc_as_cell!(4));
+
+        wam.heap.push(pstr_offset_as_cell!(0));
+        wam.heap.push(fixnum_as_cell!(Fixnum::build_with(6)));
+
+        unify!(wam, pstr_loc_as_cell!(0), pstr_loc_as_cell!(2));
+
+        assert!(!wam.fail);
+
+        assert_eq!(wam.heap[1], pstr_loc_as_cell!(4));
+
+        all_cells_unmarked(&wam.heap);
+
+        wam.heap.clear();
+
+        wam.heap.push(list_loc_as_cell!(1));
+        wam.heap.push(atom_as_cell!(atom!("a")));
+        wam.heap.push(list_loc_as_cell!(3));
+        wam.heap.push(atom_as_cell!(atom!("b")));
+        wam.heap.push(heap_loc_as_cell!(0));
+
+        wam.heap.push(list_loc_as_cell!(6));
+        wam.heap.push(atom_as_cell!(atom!("a")));
+        wam.heap.push(list_loc_as_cell!(8));
+        wam.heap.push(atom_as_cell!(atom!("b")));
+        wam.heap.push(heap_loc_as_cell!(5));
+
+        unify!(wam, heap_loc_as_cell!(0), heap_loc_as_cell!(5));
+
+        assert!(!wam.fail);
+
+        all_cells_unmarked(&wam.heap);
+
+        wam.heap.clear();
+
+        wam.heap.push(list_loc_as_cell!(1));
+        wam.heap.push(atom_as_cell!(atom!("a")));
+        wam.heap.push(list_loc_as_cell!(3));
+        wam.heap.push(atom_as_cell!(atom!("b")));
+        wam.heap.push(heap_loc_as_cell!(0));
+
+        wam.heap.push(list_loc_as_cell!(6));
+        wam.heap.push(atom_as_cell!(atom!("a")));
+        wam.heap.push(list_loc_as_cell!(8));
+        wam.heap.push(atom_as_cell!(atom!("c")));
+        wam.heap.push(heap_loc_as_cell!(5));
+
+        unify!(wam, heap_loc_as_cell!(0), heap_loc_as_cell!(5));
+
+        assert!(wam.fail);
+
+        wam.fail = false;
+        all_cells_unmarked(&wam.heap);
+        wam.heap.clear();
+
+        wam.heap.push(list_loc_as_cell!(1));
+        wam.heap.push(atom_as_cell!(atom!("a")));
+        wam.heap.push(list_loc_as_cell!(3));
+        wam.heap.push(atom_as_cell!(atom!("b")));
+        wam.heap.push(heap_loc_as_cell!(5));
+
+        wam.heap.push(list_loc_as_cell!(6));
+        wam.heap.push(atom_as_cell!(atom!("a")));
+        wam.heap.push(list_loc_as_cell!(8));
+        wam.heap.push(atom_as_cell!(atom!("b")));
+        wam.heap.push(heap_loc_as_cell!(0));
+
+        unify!(wam, heap_loc_as_cell!(0), heap_loc_as_cell!(5));
+
+        assert!(!wam.fail);
+        all_cells_unmarked(&wam.heap);
+        wam.heap.clear();
+
+        {
+            let term_write_result_1 =
+                parse_and_write_parsed_term_to_heap(&mut wam, "X = g(X,y).", &op_dir).unwrap();
+
+            print_heap_terms(wam.heap.iter(), term_write_result_1.heap_loc);
+
+            unify!(wam, heap_loc_as_cell!(2), str_loc_as_cell!(4));
+
+            assert_eq!(wam.heap[2], str_loc_as_cell!(4));
+        }
+    }
+
+    #[test]
+    fn test_unify_with_occurs_check() {
+        let mut wam = MachineState::new();
+        let mut op_dir = default_op_dir();
+
+        op_dir.insert(
+            (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(400, YFX as u8),
+        );
+
+        {
+            parse_and_write_parsed_term_to_heap(&mut wam, "f(X,X).", &op_dir).unwrap();
+
+            let term_write_result_2 =
+                parse_and_write_parsed_term_to_heap(&mut wam, "f(A,f(A)).", &op_dir).unwrap();
+
+            all_cells_unmarked(&wam.heap);
+
+            unify_with_occurs_check!(
+                wam,
+                str_loc_as_cell!(0),
+                str_loc_as_cell!(term_write_result_2.heap_loc)
+            );
+
+            assert!(wam.fail);
+        }
+    }
+
+    #[test]
+    fn test_term_compare() {
+        use ordered_float::OrderedFloat;
+        use std::cmp::Ordering;
+
+        let mut wam = MachineState::new();
+
+        wam.heap.push(heap_loc_as_cell!(0));
+        wam.heap.push(heap_loc_as_cell!(1));
+
+        assert_eq!(
+            compare_term_test!(wam, wam.heap[0], wam.heap[1]),
+            Some(Ordering::Less)
+        );
+
+        assert_eq!(
+            compare_term_test!(wam, wam.heap[1], wam.heap[0]),
+            Some(Ordering::Greater)
+        );
+
+        assert_eq!(
+            compare_term_test!(wam, wam.heap[0], wam.heap[0]),
+            Some(Ordering::Equal)
+        );
+
+        assert_eq!(
+            compare_term_test!(wam, wam.heap[1], wam.heap[1]),
+            Some(Ordering::Equal)
+        );
+
+        assert_eq!(
+            compare_term_test!(
+                wam,
+                atom_as_cell!(atom!("atom")),
+                atom_as_cstr_cell!(atom!("string"))
+            ),
+            Some(Ordering::Less)
+        );
+
+        assert_eq!(
+            compare_term_test!(
+                wam,
+                atom_as_cell!(atom!("atom")),
+                atom_as_cell!(atom!("atom"))
+            ),
+            Some(Ordering::Equal)
+        );
+
+        assert_eq!(
+            compare_term_test!(
+                wam,
+                atom_as_cell!(atom!("atom")),
+                atom_as_cell!(atom!("aaa"))
+            ),
+            Some(Ordering::Greater)
+        );
+
+        assert_eq!(
+            compare_term_test!(
+                wam,
+                fixnum_as_cell!(Fixnum::build_with(6)),
+                heap_loc_as_cell!(1)
+            ),
+            Some(Ordering::Greater)
+        );
+
+        wam.heap.clear();
+
+        wam.heap.push(atom_as_cell!(atom!("f"), 1));
+        wam.heap.push(heap_loc_as_cell!(1));
+
+        assert_eq!(
+            compare_term_test!(
+                wam,
+                heap_loc_as_cell!(0),
+                heap_loc_as_cell!(0)
+            ),
+            Some(Ordering::Equal)
+        );
+
+        assert_eq!(
+            compare_term_test!(
+                wam,
+                heap_loc_as_cell!(0),
+                atom_as_cell!(atom!("a"))
+            ),
+            Some(Ordering::Greater)
+        );
+
+        wam.heap.clear();
+
+        // [1,2,3]
+        wam.heap.push(list_loc_as_cell!(1));
+        wam.heap.push(fixnum_as_cell!(Fixnum::build_with(1)));
+        wam.heap.push(list_loc_as_cell!(3));
+        wam.heap.push(fixnum_as_cell!(Fixnum::build_with(2)));
+        wam.heap.push(list_loc_as_cell!(5));
+        wam.heap.push(fixnum_as_cell!(Fixnum::build_with(3)));
+        wam.heap.push(empty_list_as_cell!());
+
+        // [1,2]
+        wam.heap.push(list_loc_as_cell!(8));
+        wam.heap.push(fixnum_as_cell!(Fixnum::build_with(1)));
+        wam.heap.push(list_loc_as_cell!(10));
+        wam.heap.push(fixnum_as_cell!(Fixnum::build_with(2)));
+        wam.heap.push(empty_list_as_cell!());
+
+        assert_eq!(
+            compare_term_test!(
+                wam,
+                heap_loc_as_cell!(7),
+                heap_loc_as_cell!(7)
+            ),
+            Some(Ordering::Equal)
+        );
+
+        assert_eq!(
+            compare_term_test!(
+                wam,
+                heap_loc_as_cell!(0),
+                heap_loc_as_cell!(7)
+            ),
+            Some(Ordering::Greater)
+        );
+
+        assert_eq!(
+            compare_term_test!(
+                wam,
+                empty_list_as_cell!(),
+                heap_loc_as_cell!(7)
+            ),
+            Some(Ordering::Less)
+        );
+
+        assert_eq!(
+            compare_term_test!(
+                wam,
+                empty_list_as_cell!(),
+                fixnum_as_cell!(Fixnum::build_with(1))
+            ),
+            Some(Ordering::Greater)
+        );
+
+        assert_eq!(
+            compare_term_test!(
+                wam,
+                empty_list_as_cell!(),
+                atom_as_cstr_cell!(atom!("string"))
+            ),
+            Some(Ordering::Less)
+        );
+
+        assert_eq!(
+            compare_term_test!(
+                wam,
+                empty_list_as_cell!(),
+                atom_as_cell!(atom!("atom"))
+            ),
+            Some(Ordering::Less)
+        );
+
+        assert_eq!(
+            compare_term_test!(
+                wam,
+                atom_as_cell!(atom!("atom")),
+                empty_list_as_cell!()
+            ),
+            Some(Ordering::Greater)
+        );
+
+        let one_p_one = typed_arena_ptr_as_cell!(
+            arena_alloc!(OrderedFloat(1.1), &mut wam.arena)
+        );
+
+        assert_eq!(
+            compare_term_test!(
+                wam,
+                one_p_one,
+                fixnum_as_cell!(Fixnum::build_with(1))
+            ),
+            Some(Ordering::Less)
+        );
+
+        assert_eq!(
+            compare_term_test!(
+                wam,
+                fixnum_as_cell!(Fixnum::build_with(1)),
+                one_p_one
+            ),
+            Some(Ordering::Greater)
+        );
+    }
+
+    #[test]
+    fn is_cyclic_term_tests() {
+        let mut wam = MachineState::new();
+
+        assert!(!wam.is_cyclic_term(atom_as_cell!(atom!("f"))));
+        assert!(!wam.is_cyclic_term(fixnum_as_cell!(Fixnum::build_with(555))));
+
+        wam.heap.push(heap_loc_as_cell!(0));
+
+        assert!(!wam.is_cyclic_term(heap_loc_as_cell!(0)));
+
+        all_cells_unmarked(&wam.heap);
+        wam.heap.clear();
+
+        wam.heap.extend(functor!(atom!("f"), [atom(atom!("a")), atom(atom!("b"))]));
+
+        assert!(!wam.is_cyclic_term(str_loc_as_cell!(0)));
+
+        all_cells_unmarked(&wam.heap);
+
+        assert!(!wam.is_cyclic_term(heap_loc_as_cell!(1)));
+
+        all_cells_unmarked(&wam.heap);
+
+        assert!(!wam.is_cyclic_term(heap_loc_as_cell!(2)));
+
+        all_cells_unmarked(&wam.heap);
+
+        wam.heap[2] = str_loc_as_cell!(0);
+
+        print_heap_terms(wam.heap.iter(), 0);
+
+        assert!(wam.is_cyclic_term(str_loc_as_cell!(0)));
+
+        all_cells_unmarked(&wam.heap);
+
+        wam.heap[2] = atom_as_cell!(atom!("b"));
+        wam.heap[1] = str_loc_as_cell!(0);
+
+        assert!(wam.is_cyclic_term(str_loc_as_cell!(0)));
+
+        all_cells_unmarked(&wam.heap);
+
+        assert!(wam.is_cyclic_term(heap_loc_as_cell!(1)));
+
+        all_cells_unmarked(&wam.heap);
+
+        wam.heap.clear();
+
+        wam.heap.push(pstr_as_cell!(atom!("a string")));
+        wam.heap.push(empty_list_as_cell!());
+
+        assert!(!wam.is_cyclic_term(heap_loc_as_cell!(0)));
+    }
+}

src/machine/mod.rs

@@ -1,67 +1,70 @@
-use prolog_parser::ast::*;
-use prolog_parser::tabled_rc::*;
-use prolog_parser::{clause_name, temp_v};
+pub mod arithmetic_ops;
+pub mod attributed_variables;
+pub mod code_repo;
+pub mod code_walker;
+#[macro_use]
+pub mod loader;
+pub mod compile;
+pub mod copier;
+pub mod gc;
+pub mod heap;
+pub mod load_state;
+pub mod machine_errors;
+pub mod machine_indices;
+pub mod machine_state;
+pub mod machine_state_impl;
+pub mod mock_wam;
+pub mod partial_string;
+pub mod preprocessor;
+pub mod stack;
+pub mod streams;
+pub mod system_calls;
+pub mod term_stream;
 
-use lazy_static::lazy_static;
-
-use crate::clause_types::*;
+use crate::atom_table::*;
 use crate::forms::*;
 use crate::instructions::*;
-use crate::machine::loader::*;
-use crate::machine::term_stream::{LiveTermStream, LoadStatePayload, TermStream};
-use crate::read::*;
-
-mod attributed_variables;
-pub(super) mod code_repo;
-pub(crate) mod code_walker;
-#[macro_use]
-pub(crate) mod loader;
-mod compile;
-mod copier;
-pub(crate) mod heap;
-mod load_state;
-pub(crate) mod machine_errors;
-pub(crate) mod machine_indices;
-pub(super) mod machine_state;
-pub(crate) mod partial_string;
-mod preprocessor;
-mod raw_block;
-mod stack;
-pub(crate) mod streams;
-mod term_stream;
-
-#[macro_use]
-mod arithmetic_ops;
-#[macro_use]
-mod machine_state_impl;
-mod system_calls;
-
 use crate::machine::code_repo::*;
 use crate::machine::compile::*;
+use crate::machine::heap::*;
+use crate::machine::loader::*;
 use crate::machine::machine_errors::*;
 use crate::machine::machine_indices::*;
 use crate::machine::machine_state::*;
-pub use crate::machine::streams::Stream;
+use crate::machine::streams::*;
+use crate::types::*;
 
 use indexmap::IndexMap;
 
-//use std::convert::TryFrom;
-use prolog_parser::ast::ClauseName;
-use std::fs::File;
-use std::mem;
+use lazy_static::lazy_static;
+
+use std::env;
 use std::path::PathBuf;
 use std::sync::atomic::AtomicBool;
 
+lazy_static! {
+    pub static ref INTERRUPT: AtomicBool = AtomicBool::new(false);
+}
+
+#[derive(Debug)]
+pub struct Machine {
+    pub(super) machine_st: MachineState,
+    pub(super) inner_heap: Heap,
+    pub(super) policies: MachinePolicies,
+    pub(super) indices: IndexStore,
+    pub(super) code_repo: CodeRepo,
+    pub(super) user_input: Stream,
+    pub(super) user_output: Stream,
+    pub(super) user_error: Stream,
+    pub(super) load_contexts: Vec<LoadContext>,
+}
+
 #[derive(Debug)]
 pub(crate) struct MachinePolicies {
     call_policy: Box<dyn CallPolicy>,
     cut_policy: Box<dyn CutPolicy>,
 }
 
-lazy_static! {
-    pub static ref INTERRUPT: AtomicBool = AtomicBool::new(false);
-}
-
 impl MachinePolicies {
     #[inline]
     fn new() -> Self {
@@ -80,10 +83,10 @@ impl Default for MachinePolicies {
 }
 
 #[derive(Debug)]
-pub(super) struct LoadContext {
+pub struct LoadContext {
     pub(super) path: PathBuf,
     pub(super) stream: Stream,
-    pub(super) module: ClauseName,
+    pub(super) module: Atom,
 }
 
 impl LoadContext {
@@ -100,32 +103,49 @@ impl LoadContext {
         LoadContext {
             path: path_buf,
             stream,
-            module: clause_name!("user"),
+            module: atom!("user"),
         }
     }
 }
 
-#[derive(Debug)]
-pub struct Machine {
-    pub(super) machine_st: MachineState,
-    pub(super) policies: MachinePolicies,
-    pub(super) indices: IndexStore,
-    pub(super) code_repo: CodeRepo,
-    pub(super) user_input: Stream,
-    pub(super) user_output: Stream,
-    pub(super) user_error: Stream,
-    pub(super) load_contexts: Vec<LoadContext>,
-}
-
 #[inline]
 fn current_dir() -> PathBuf {
-    std::env::current_dir().unwrap_or(PathBuf::from("./"))
+    env::current_dir().unwrap_or(PathBuf::from("./"))
 }
 
 include!(concat!(env!("OUT_DIR"), "/libraries.rs"));
 
+pub struct MachinePreludeView<'a> {
+    pub indices: &'a mut IndexStore,
+    pub code_repo: &'a mut CodeRepo,
+    pub load_contexts: &'a mut Vec<LoadContext>,
+}
+
 impl Machine {
-    fn run_module_predicate(&mut self, module_name: ClauseName, key: PredicateKey) {
+    #[inline]
+    pub fn prelude_view_and_machine_st(&mut self) -> (MachinePreludeView, &mut MachineState) {
+        (
+            MachinePreludeView {
+                indices: &mut self.indices,
+                code_repo: &mut self.code_repo,
+                load_contexts: &mut self.load_contexts,
+            },
+            &mut self.machine_st
+        )
+    }
+
+    pub fn throw_session_error(&mut self, err: SessionError, key: PredicateKey) {
+        let err = self.machine_st.session_error(err);
+        let stub = functor_stub(key.0, key.1);
+        let err = self.machine_st.error_form(err, stub);
+
+        self.machine_st.throw_exception(err);
+        return;
+    }
+}
+
+impl Machine {
+    fn run_module_predicate(&mut self, module_name: Atom, key: PredicateKey) {
         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();
@@ -140,27 +160,29 @@ impl Machine {
         unreachable!();
     }
 
-    pub fn load_file(&mut self, path: String, stream: Stream) {
-        self.machine_st[temp_v!(1)] =
-            Addr::Stream(self.machine_st.heap.push(HeapCellValue::Stream(stream)));
+    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.atom_tbl.build_with(path)
+        );
 
-        self.machine_st[temp_v!(2)] = Addr::Con(self.machine_st.heap.push(HeapCellValue::Atom(
-            clause_name!(path, self.machine_st.atom_tbl),
-            None,
-        )));
-
-        self.run_module_predicate(clause_name!("loader"), (clause_name!("file_load"), 2));
+        self.run_module_predicate(atom!("loader"), (atom!("file_load"), 2));
     }
 
     fn load_top_level(&mut self) {
         let mut path_buf = current_dir();
-        path_buf.push("toplevel.pl");
 
-        let path = path_buf.to_str().unwrap().to_string();
+        path_buf.push("src/toplevel.pl");
 
-        self.load_file(path, Stream::from(include_str!("../toplevel.pl")));
+        let path = path_buf.to_str().unwrap();
+        let toplevel_stream = Stream::from_static_string(
+            include_str!("../toplevel.pl"),
+            &mut self.machine_st.arena,
+        );
 
-        if let Some(toplevel) = self.indices.modules.get(&clause_name!("$toplevel")) {
+        self.load_file(path, toplevel_stream);
+
+        if let Some(toplevel) = self.indices.modules.get(&atom!("$toplevel")) {
             load_module(
                 &mut self.indices.code_dir,
                 &mut self.indices.op_dir,
@@ -178,9 +200,15 @@ impl Machine {
         path_buf.push("machine/attributed_variables.pl");
 
         bootstrapping_compile(
-            Stream::from(include_str!("attributed_variables.pl")),
+            Stream::from_static_string(
+                include_str!("attributed_variables.pl"),
+                &mut self.machine_st.arena,
+            ),
             self,
-            ListingSource::from_file_and_path(clause_name!("attributed_variables"), path_buf),
+            ListingSource::from_file_and_path(
+                atom!("attributed_variables"),
+                path_buf,
+            ),
         )
         .unwrap();
 
@@ -188,44 +216,49 @@ impl Machine {
         path_buf.push("machine/project_attributes.pl");
 
         bootstrapping_compile(
-            Stream::from(include_str!("project_attributes.pl")),
+            Stream::from_static_string(
+                include_str!("project_attributes.pl"),
+                &mut self.machine_st.arena,
+            ),
             self,
-            ListingSource::from_file_and_path(clause_name!("project_attributes"), path_buf),
+            ListingSource::from_file_and_path(atom!("project_attributes"), path_buf),
         )
         .unwrap();
 
-        if let Some(module) = self.indices.modules.get(&clause_name!("$atts")) {
-            if let Some(code_index) = module.code_dir.get(&(clause_name!("driver"), 2)) {
+        if let Some(module) = self.indices.modules.get(&atom!("$atts")) {
+            if let Some(code_index) = module.code_dir.get(&(atom!("driver"), 2)) {
                 self.machine_st.attr_var_init.verify_attrs_loc = code_index.local().unwrap();
             }
         }
     }
 
     pub fn run_top_level(&mut self) {
-        use std::env;
-
         let mut arg_pstrs = vec![];
 
         for arg in env::args() {
-            arg_pstrs.push(self.machine_st.heap.put_complete_string(&arg));
+            arg_pstrs.push(put_complete_string(
+                &mut self.machine_st.heap,
+                &arg,
+                &mut self.machine_st.atom_tbl,
+            ));
         }
 
-        let list_addr = Addr::HeapCell(self.machine_st.heap.to_list(arg_pstrs.into_iter()));
+        self.machine_st.registers[1] = heap_loc_as_cell!(
+            iter_to_heap_list(&mut self.machine_st.heap, arg_pstrs.into_iter())
+        );
 
-        self.machine_st[temp_v!(1)] = list_addr;
-
-        self.run_module_predicate(clause_name!("$toplevel"), (clause_name!("$repl"), 1));
+        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) {
             for arity in 1..66 {
-                let key = (clause_name!("call"), arity);
+                let key = (atom!("call"), arity);
 
                 match loader.code_dir.get(&key) {
                     Some(src_code_index) => {
                         let target_code_index = target_code_dir
-                            .entry(key.clone())
+                            .entry(key)
                             .or_insert_with(|| CodeIndex::new(IndexPtr::Undefined));
 
                         target_code_index.set(src_code_index.get());
@@ -237,15 +270,15 @@ impl Machine {
             }
         }
 
-        if let Some(loader) = self.indices.modules.swap_remove(&clause_name!("loader")) {
-            if let Some(builtins) = self.indices.modules.get_mut(&clause_name!("builtins")) {
+        if let Some(loader) = self.indices.modules.swap_remove(&atom!("loader")) {
+            if let Some(builtins) = self.indices.modules.get_mut(&atom!("builtins")) {
                 // Import loader's exports into the builtins module so they will be
                 // implicitly included in every further module.
                 load_module(
                     &mut builtins.code_dir,
                     &mut builtins.op_dir,
                     &mut builtins.meta_predicates,
-                    &CompilationTarget::Module(clause_name!("builtins")),
+                    &CompilationTarget::Module(atom!("builtins")),
                     &loader,
                 );
 
@@ -257,7 +290,7 @@ impl Machine {
                     builtins
                         .module_decl
                         .exports
-                        .push(ModuleExport::PredicateKey((clause_name!("call"), arity)));
+                        .push(ModuleExport::PredicateKey((atom!("call"), arity)));
                 }
             }
 
@@ -267,17 +300,24 @@ impl Machine {
 
             update_call_n_indices(&loader, &mut self.indices.code_dir);
 
-            self.indices.modules.insert(clause_name!("loader"), loader);
+            self.indices.modules.insert(atom!("loader"), loader);
         } else {
             unreachable!()
         }
     }
 
-    pub fn new(user_input: Stream, user_output: Stream, user_error: Stream) -> Self {
+    pub fn new() -> Self {
         use ref_thread_local::RefThreadLocal;
 
+        let mut machine_st = MachineState::new();
+
+        let user_input = Stream::stdin(&mut machine_st.arena);
+        let user_output = Stream::stdout(&mut machine_st.arena);
+        let user_error = Stream::stderr(&mut machine_st.arena);
+
         let mut wam = Machine {
-            machine_st: MachineState::new(),
+            machine_st,
+            inner_heap: Heap::new(),
             policies: MachinePolicies::new(),
             indices: IndexStore::new(),
             code_repo: CodeRepo::new(),
@@ -293,23 +333,29 @@ impl Machine {
         lib_path.push("lib");
 
         bootstrapping_compile(
-            Stream::from(LIBRARIES.borrow()["ops_and_meta_predicates"]),
+            Stream::from_static_string(
+                LIBRARIES.borrow()["ops_and_meta_predicates"],
+                &mut wam.machine_st.arena,
+            ),
             &mut wam,
             ListingSource::from_file_and_path(
-                clause_name!("ops_and_meta_predicates.pl"),
+                atom!("ops_and_meta_predicates.pl"),
                 lib_path.clone(),
             ),
         )
         .unwrap();
 
         bootstrapping_compile(
-            Stream::from(LIBRARIES.borrow()["builtins"]),
+            Stream::from_static_string(
+                LIBRARIES.borrow()["builtins"],
+                &mut wam.machine_st.arena,
+            ),
             &mut wam,
-            ListingSource::from_file_and_path(clause_name!("builtins.pl"), lib_path.clone()),
+            ListingSource::from_file_and_path(atom!("builtins.pl"), lib_path.clone()),
         )
         .unwrap();
 
-        if let Some(builtins) = wam.indices.modules.get(&clause_name!("builtins")) {
+        if let Some(builtins) = wam.indices.modules.get(&atom!("builtins")) {
             load_module(
                 &mut wam.indices.code_dir,
                 &mut wam.indices.op_dir,
@@ -324,15 +370,15 @@ impl Machine {
         lib_path.pop(); // remove the "lib" at the end
 
         bootstrapping_compile(
-            Stream::from(include_str!("../loader.pl")),
+            Stream::from_static_string(include_str!("../loader.pl"), &mut wam.machine_st.arena),
             &mut wam,
-            ListingSource::from_file_and_path(clause_name!("loader.pl"), lib_path.clone()),
+            ListingSource::from_file_and_path(atom!("loader.pl"), lib_path.clone()),
         )
         .unwrap();
 
         wam.configure_modules();
 
-        if let Some(loader) = wam.indices.modules.get(&clause_name!("loader")) {
+        if let Some(loader) = wam.indices.modules.get(&atom!("loader")) {
             load_module(
                 &mut wam.indices.code_dir,
                 &mut wam.indices.op_dir,
@@ -352,38 +398,21 @@ impl Machine {
     }
 
     pub(crate) fn configure_streams(&mut self) {
-        self.user_input.options_mut().alias = Some(clause_name!("user_input"));
+        self.user_input.options_mut().set_alias_to_atom_opt(Some(atom!("user_input")));
 
         self.indices
             .stream_aliases
-            .insert(clause_name!("user_input"), self.user_input.clone());
+            .insert(atom!("user_input"), self.user_input);
 
-        self.indices.streams.insert(self.user_input.clone());
+        self.indices.streams.insert(self.user_input);
 
-        self.user_output.options_mut().alias = Some(clause_name!("user_output"));
+        self.user_output.options_mut().set_alias_to_atom_opt(Some(atom!("user_output")));
 
         self.indices
             .stream_aliases
-            .insert(clause_name!("user_output"), self.user_output.clone());
+            .insert(atom!("user_output"), self.user_output);
 
-        self.user_error.options_mut().alias = Some(clause_name!("user_error"));
-
-        self.indices
-            .stream_aliases
-            .insert(clause_name!("user_error"), self.user_error.clone());
-
-        self.indices.streams.insert(self.user_output.clone());
-    }
-
-    fn throw_session_error(&mut self, err: SessionError, key: PredicateKey) {
-        let h = self.machine_st.heap.h();
-
-        let err = MachineError::session_error(h, err);
-        let stub = MachineError::functor_stub(key.0, key.1);
-        let err = self.machine_st.error_form(err, stub);
-
-        self.machine_st.throw_exception(err);
-        return;
+        self.indices.streams.insert(self.user_output);
     }
 
     fn handle_toplevel_command(&mut self, code_ptr: REPLCodePtr, p: LocalCodePtr) {
@@ -604,13 +633,14 @@ impl MachineState {
         self.b0 = self.stack.index_or_frame(b).prelude.b0;
         self.p = CodePtr::Local(self.stack.index_or_frame(b).prelude.bp);
 
+        self.pdl.clear();
         self.fail = false;
     }
 
     fn check_machine_index(&mut self, code_repo: &CodeRepo) -> bool {
         match self.p {
-            CodePtr::Local(LocalCodePtr::DirEntry(p))
-            | CodePtr::Local(LocalCodePtr::IndexingBuf(p, ..))
+            CodePtr::Local(LocalCodePtr::DirEntry(p)) |
+            CodePtr::Local(LocalCodePtr::IndexingBuf(p, ..))
                 if p < code_repo.code.len() => {}
             CodePtr::Local(LocalCodePtr::Halt) | CodePtr::REPL(..) => {
                 return false;
@@ -690,7 +720,9 @@ impl MachineState {
                     self.p = CodePtr::Local(self.attr_var_init.cp);
 
                     let instigating_p = CodePtr::Local(self.attr_var_init.instigating_p);
-                    let instigating_instr = code_repo.lookup_instr(false, &instigating_p).unwrap();
+                    let instigating_instr = code_repo
+                        .lookup_instr(false, &instigating_p)
+                        .unwrap();
 
                     if !instigating_instr.as_ref().is_head_instr() {
                         let cp = self.p.local();

src/machine/preprocessor.rs

@@ -1,12 +1,10 @@
-use prolog_parser::ast::*;
-use prolog_parser::tabled_rc::*;
-use prolog_parser::{atom, clause_name, rc_atom};
-
+use crate::atom_table::*;
+use crate::clause_types::*;
 use crate::forms::*;
 use crate::iterators::*;
-use crate::machine::load_state::*;
+use crate::machine::loader::*;
 use crate::machine::machine_errors::*;
-use crate::machine::*;
+use crate::parser::ast::*;
 
 use indexmap::IndexSet;
 
@@ -30,89 +28,81 @@ pub(crate) enum CutContext {
     HasCutVariable,
 }
 
-pub(crate) fn fold_by_str<I>(terms: I, mut term: Term, sym: ClauseName) -> Term
+pub(crate) fn fold_by_str<I>(terms: I, mut term: Term, sym: Atom) -> Term
 where
     I: DoubleEndedIterator<Item = Term>,
 {
     for prec in terms.rev() {
-        term = Term::Clause(
-            Cell::default(),
-            sym.clone(),
-            vec![Box::new(prec), Box::new(term)],
-            None,
-        );
+        term = Term::Clause(Cell::default(), sym, vec![prec, term]);
     }
 
     term
 }
 
 pub(crate) fn to_op_decl(
-    prec: usize,
-    spec: &str,
-    name: ClauseName,
+    prec: u16,
+    spec: Atom,
+    name: Atom,
 ) -> Result<OpDecl, CompilationError> {
     match spec {
-        "xfx" => Ok(OpDecl::new(prec, XFX, name)),
-        "xfy" => Ok(OpDecl::new(prec, XFY, name)),
-        "yfx" => Ok(OpDecl::new(prec, YFX, name)),
-        "fx" => Ok(OpDecl::new(prec, FX, name)),
-        "fy" => Ok(OpDecl::new(prec, FY, name)),
-        "xf" => Ok(OpDecl::new(prec, XF, name)),
-        "yf" => Ok(OpDecl::new(prec, YF, name)),
+        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)),
+        atom!("yfx") => Ok(OpDecl::new(OpDesc::build_with(prec, YFX as u8), name)),
+        atom!("fx") => Ok(OpDecl::new(OpDesc::build_with(prec, FX as u8), name)),
+        atom!("fy") => Ok(OpDecl::new(OpDesc::build_with(prec, FY as u8), name)),
+        atom!("xf") => Ok(OpDecl::new(OpDesc::build_with(prec, XF as u8), name)),
+        atom!("yf") => Ok(OpDecl::new(OpDesc::build_with(prec, YF as u8), name)),
         _ => Err(CompilationError::InconsistentEntry),
     }
 }
 
 fn setup_op_decl(
-    mut terms: Vec<Box<Term>>,
-    atom_tbl: TabledData<Atom>,
+    mut terms: Vec<Term>,
+    atom_tbl: &mut AtomTable,
 ) -> Result<OpDecl, CompilationError> {
-    let name = match *terms.pop().unwrap() {
-        Term::Constant(_, Constant::Atom(name, _)) => name,
-        Term::Constant(_, Constant::Char(c)) => clause_name!(c.to_string(), atom_tbl),
+    let name = match terms.pop().unwrap() {
+        Term::Literal(_, Literal::Atom(name)) => name,
+        Term::Literal(_, Literal::Char(c)) => atom_tbl.build_with(&c.to_string()),
         _ => return Err(CompilationError::InconsistentEntry),
     };
 
-    let spec = match *terms.pop().unwrap() {
-        Term::Constant(_, Constant::Atom(name, _)) => name,
-        Term::Constant(_, Constant::Char(c)) => clause_name!(c.to_string(), atom_tbl),
+    let spec = match terms.pop().unwrap() {
+        Term::Literal(_, Literal::Atom(name)) => name,
+        Term::Literal(_, Literal::Char(c)) => atom_tbl.build_with(&c.to_string()),
         _ => return Err(CompilationError::InconsistentEntry),
     };
 
-    let prec = match *terms.pop().unwrap() {
-        Term::Constant(_, Constant::Fixnum(bi)) => match usize::try_from(bi) {
+    let prec = match terms.pop().unwrap() {
+        Term::Literal(_, Literal::Fixnum(bi)) => match u16::try_from(bi.get_num()) {
             Ok(n) if n <= 1200 => n,
             _ => return Err(CompilationError::InconsistentEntry),
         },
         _ => return Err(CompilationError::InconsistentEntry),
     };
 
-    to_op_decl(prec, spec.as_str(), name)
+    to_op_decl(prec, spec, name)
 }
 
 fn setup_predicate_indicator(term: &mut Term) -> Result<PredicateKey, CompilationError> {
     match term {
-        Term::Clause(_, ref slash, ref mut terms, Some(_))
-            if (slash.as_str() == "/" || slash.as_str() == "//") && terms.len() == 2 =>
+        Term::Clause(_, slash, ref mut terms)
+            if (*slash == atom!("/") || *slash == atom!("//")) && terms.len() == 2 =>
         {
-            let arity = *terms.pop().unwrap();
-            let name = *terms.pop().unwrap();
+            let arity = terms.pop().unwrap();
+            let name = terms.pop().unwrap();
 
-            let arity = arity
-                .into_constant()
-                .and_then(|c| match c {
-                    Constant::Integer(n) => n.to_usize(),
-                    Constant::Fixnum(n) => usize::try_from(n).ok(),
-                    _ => None,
-                })
-                .ok_or(CompilationError::InvalidModuleExport)?;
+            let arity = match arity {
+                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)?;
 
-            let name = name
-                .into_constant()
-                .and_then(|c| c.to_atom())
-                .ok_or(CompilationError::InvalidModuleExport)?;
+            let name = match name {
+                Term::Literal(_, Literal::Atom(name)) => Some(name),
+                _ => None,
+            }.ok_or(CompilationError::InvalidModuleExport)?;
 
-            if slash.as_str() == "/" {
+            if *slash == atom!("/") {
                 Ok((name, arity))
             } else {
                 Ok((name, arity + 2))
@@ -148,13 +138,13 @@ fn setup_scoped_predicate_indicator(term: &mut Term) -> Result<ScopedPredicateKe
 
 fn setup_module_export(
     mut term: Term,
-    atom_tbl: TabledData<Atom>,
+    atom_tbl: &mut AtomTable,
 ) -> Result<ModuleExport, CompilationError> {
     setup_predicate_indicator(&mut term)
         .map(ModuleExport::PredicateKey)
         .or_else(|_| {
-            if let Term::Clause(_, name, terms, _) = term {
-                if terms.len() == 3 && name.as_str() == "op" {
+            if let Term::Clause(_, name, terms) = term {
+                if terms.len() == 3 && name == atom!("op") {
                     Ok(ModuleExport::OpDecl(setup_op_decl(terms, atom_tbl)?))
                 } else {
                     Err(CompilationError::InvalidModuleDecl)
@@ -167,18 +157,18 @@ fn setup_module_export(
 
 pub(super) fn setup_module_export_list(
     mut export_list: Term,
-    atom_tbl: TabledData<Atom>,
+    atom_tbl: &mut AtomTable,
 ) -> Result<Vec<ModuleExport>, CompilationError> {
     let mut exports = vec![];
 
     while let Term::Cons(_, t1, t2) = export_list {
-        let module_export = setup_module_export(*t1, atom_tbl.clone())?;
+        let module_export = setup_module_export(*t1, atom_tbl)?;
 
         exports.push(module_export);
         export_list = *t2;
     }
 
-    if let Term::Constant(_, Constant::EmptyList) = export_list {
+    if let Term::Literal(_, Literal::Atom(atom!("[]"))) = export_list {
         Ok(exports)
     } else {
         Err(CompilationError::InvalidModuleDecl)
@@ -186,35 +176,33 @@ pub(super) fn setup_module_export_list(
 }
 
 fn setup_module_decl(
-    mut terms: Vec<Box<Term>>,
-    atom_tbl: TabledData<Atom>,
+    mut terms: Vec<Term>,
+    atom_tbl: &mut AtomTable,
 ) -> Result<ModuleDecl, CompilationError> {
-    let export_list = *terms.pop().unwrap();
-    let name = terms
-        .pop()
-        .unwrap()
-        .into_constant()
-        .and_then(|c| c.to_atom())
-        .ok_or(CompilationError::InvalidModuleDecl)?;
+    let export_list = terms.pop().unwrap();
+    let name = terms.pop().unwrap();
+
+    let name = match name {
+        Term::Literal(_, Literal::Atom(name)) => Some(name),
+        _ => None,
+    }.ok_or(CompilationError::InvalidModuleDecl)?;
 
     let exports = setup_module_export_list(export_list, atom_tbl)?;
+
     Ok(ModuleDecl { name, exports })
 }
 
-fn setup_use_module_decl(mut terms: Vec<Box<Term>>) -> Result<ModuleSource, CompilationError> {
-    match *terms.pop().unwrap() {
-        Term::Clause(_, ref name, ref mut terms, None)
-            if name.as_str() == "library" && terms.len() == 1 =>
+fn setup_use_module_decl(mut terms: Vec<Term>) -> Result<ModuleSource, CompilationError> {
+    match terms.pop().unwrap() {
+        Term::Clause(_, name, mut terms)
+            if name == atom!("library") && terms.len() == 1 =>
         {
-            terms
-                .pop()
-                .unwrap()
-                .into_constant()
-                .and_then(|c| c.to_atom())
-                .map(|c| ModuleSource::Library(c))
-                .ok_or(CompilationError::InvalidUseModuleDecl)
+            match terms.pop().unwrap() {
+                Term::Literal(_, Literal::Atom(name)) => Ok(ModuleSource::Library(name)),
+                _ => Err(CompilationError::InvalidModuleDecl),
+            }
         }
-        Term::Constant(_, Constant::Atom(ref name, _)) => Ok(ModuleSource::File(name.clone())),
+        Term::Literal(_, Literal::Atom(name)) => Ok(ModuleSource::File(name)),
         _ => Err(CompilationError::InvalidUseModuleDecl),
     }
 }
@@ -224,10 +212,10 @@ fn setup_double_quotes(mut terms: Vec<Box<Term>>) -> Result<DoubleQuotes, Compil
     let dbl_quotes = *terms.pop().unwrap();
 
     match terms[0].as_ref() {
-        Term::Constant(_, Constant::Atom(ref name, _))
+        Term::Literal(_, Literal::Atom(ref name, _))
             if name.as_str() == "double_quotes" => {
                 match dbl_quotes {
-                    Term::Constant(_, Constant::Atom(name, _)) => {
+                    Term::Literal(_, Literal::Atom(name, _)) => {
                         match name.as_str() {
                             "atom"  => Ok(DoubleQuotes::Atom),
                             "chars" => Ok(DoubleQuotes::Chars),
@@ -250,34 +238,31 @@ fn setup_double_quotes(mut terms: Vec<Box<Term>>) -> Result<DoubleQuotes, Compil
 type UseModuleExport = (ModuleSource, IndexSet<ModuleExport>);
 
 fn setup_qualified_import(
-    mut terms: Vec<Box<Term>>,
-    atom_tbl: TabledData<Atom>,
+    mut terms: Vec<Term>,
+    atom_tbl: &mut AtomTable,
 ) -> Result<UseModuleExport, CompilationError> {
-    let mut export_list = *terms.pop().unwrap();
-    let module_src = match *terms.pop().unwrap() {
-        Term::Clause(_, ref name, ref mut terms, None)
-            if name.as_str() == "library" && terms.len() == 1 =>
+    let mut export_list = terms.pop().unwrap();
+    let module_src = match terms.pop().unwrap() {
+        Term::Clause(_, name, mut terms)
+            if name == atom!("library") && terms.len() == 1 =>
         {
-            terms
-                .pop()
-                .unwrap()
-                .into_constant()
-                .and_then(|c| c.to_atom())
-                .map(|c| ModuleSource::Library(c))
-                .ok_or(CompilationError::InvalidUseModuleDecl)
+            match terms.pop().unwrap() {
+                Term::Literal(_, Literal::Atom(name)) => Ok(ModuleSource::Library(name)),
+                _ => Err(CompilationError::InvalidModuleDecl),
+            }
         }
-        Term::Constant(_, Constant::Atom(ref name, _)) => Ok(ModuleSource::File(name.clone())),
+        Term::Literal(_, Literal::Atom(name)) => Ok(ModuleSource::File(name)),
         _ => Err(CompilationError::InvalidUseModuleDecl),
     }?;
 
     let mut exports = IndexSet::new();
 
     while let Term::Cons(_, t1, t2) = export_list {
-        exports.insert(setup_module_export(*t1, atom_tbl.clone())?);
+        exports.insert(setup_module_export(*t1, atom_tbl)?);
         export_list = *t2;
     }
 
-    if let Term::Constant(_, Constant::EmptyList) = export_list {
+    if let Term::Literal(_, Literal::Atom(atom!("[]"))) = export_list {
         Ok((module_src, exports))
     } else {
         Err(CompilationError::InvalidModuleDecl)
@@ -322,29 +307,29 @@ fn setup_qualified_import(
  * -
  * ?
  */
-fn setup_meta_predicate<'a>(
-    mut terms: Vec<Box<Term>>,
-    load_state: &LoadState<'a>,
-) -> Result<(ClauseName, ClauseName, Vec<MetaSpec>), CompilationError> {
+fn setup_meta_predicate<'a, LS: LoadState<'a>>(
+    mut terms: Vec<Term>,
+    loader: &mut Loader<'a, LS>,
+) -> Result<(Atom, Atom, Vec<MetaSpec>), CompilationError> {
     fn get_name_and_meta_specs(
-        name: ClauseName,
-        terms: &mut [Box<Term>],
-    ) -> Result<(ClauseName, Vec<MetaSpec>), CompilationError> {
+        name: Atom,
+        terms: &mut [Term],
+    ) -> Result<(Atom, Vec<MetaSpec>), CompilationError> {
         let mut meta_specs = vec![];
 
         for meta_spec in terms.into_iter() {
-            match &**meta_spec {
-                Term::Constant(_, Constant::Atom(meta_spec, _)) => {
-                    let meta_spec = match meta_spec.as_str() {
-                        "+" => MetaSpec::Plus,
-                        "-" => MetaSpec::Minus,
-                        "?" => MetaSpec::Either,
+            match meta_spec {
+                Term::Literal(_, Literal::Atom(meta_spec)) => {
+                    let meta_spec = match meta_spec {
+                        atom!("+") => MetaSpec::Plus,
+                        atom!("-") => MetaSpec::Minus,
+                        atom!("?") => MetaSpec::Either,
                         _ => return Err(CompilationError::InvalidMetaPredicateDecl),
                     };
 
                     meta_specs.push(meta_spec);
                 }
-                Term::Constant(_, Constant::Fixnum(n)) => match usize::try_from(*n) {
+                Term::Literal(_, Literal::Fixnum(n)) => match usize::try_from(n.get_num()) {
                     Ok(n) if n <= MAX_ARITY => {
                         meta_specs.push(MetaSpec::RequiresExpansionWithArgument(n));
                     }
@@ -361,16 +346,15 @@ fn setup_meta_predicate<'a>(
         Ok((name, meta_specs))
     }
 
-    match *terms.pop().unwrap() {
-        Term::Clause(_, name, mut terms, _) if name.as_str() == ":" && terms.len() == 2 => {
-            let spec = *terms.pop().unwrap();
-            let module_name = *terms.pop().unwrap();
+    match terms.pop().unwrap() {
+        Term::Clause(_, name, mut terms) if name == atom!(":") && terms.len() == 2 => {
+            let spec = terms.pop().unwrap();
+            let module_name = terms.pop().unwrap();
 
             match module_name {
-                Term::Constant(_, Constant::Atom(module_name, _)) => match spec {
-                    Term::Clause(_, name, mut terms, _) => {
+                Term::Literal(_, Literal::Atom(module_name)) => match spec {
+                    Term::Clause(_, name, mut terms) => {
                         let (name, meta_specs) = get_name_and_meta_specs(name, &mut terms)?;
-
                         Ok((module_name, name, meta_specs))
                     }
                     _ => Err(CompilationError::InvalidMetaPredicateDecl),
@@ -378,10 +362,10 @@ fn setup_meta_predicate<'a>(
                 _ => Err(CompilationError::InvalidMetaPredicateDecl),
             }
         }
-        Term::Clause(_, name, mut terms, _) => {
+        Term::Clause(_, name, mut terms) => {
             let (name, meta_specs) = get_name_and_meta_specs(name, &mut terms)?;
             Ok((
-                load_state.compilation_target.module_name(),
+                loader.payload.compilation_target.module_name(),
                 name,
                 meta_specs,
             ))
@@ -420,11 +404,11 @@ fn merge_clauses(tls: &mut VecDeque<TopLevel>) -> Result<TopLevel, CompilationEr
     }
 }
 
-fn mark_cut_variables_as(terms: &mut Vec<Term>, name: ClauseName) {
+fn mark_cut_variables_as(terms: &mut Vec<Term>, name: Atom) {
     for term in terms.iter_mut() {
         match term {
-            &mut Term::Constant(_, Constant::Atom(ref mut var, _)) if var.as_str() == "!" => {
-                *var = name.clone()
+            &mut Term::Literal(_, Literal::Atom(ref mut var)) if *var == atom!("!") => {
+                *var = name;
             }
             _ => {}
         }
@@ -433,12 +417,12 @@ fn mark_cut_variables_as(terms: &mut Vec<Term>, name: ClauseName) {
 
 fn mark_cut_variable(term: &mut Term) -> bool {
     let cut_var_found = match term {
-        &mut Term::Constant(_, Constant::Atom(ref var, _)) if var.as_str() == "!" => true,
+        &mut Term::Literal(_, Literal::Atom(ref var)) if *var == atom!("!") => true,
         _ => false,
     };
 
     if cut_var_found {
-        *term = Term::Var(Cell::default(), rc_atom!("!"));
+        *term = Term::Var(Cell::default(), Rc::new(String::from("!")));
         true
     } else {
         false
@@ -463,21 +447,21 @@ fn check_for_internal_if_then(terms: &mut Vec<Term>) {
         return;
     }
 
-    if let Some(Term::Clause(_, ref name, ref subterms, _)) = terms.last() {
-        if name.as_str() != "->" || subterms.len() != 2 {
+    if let Some(Term::Clause(_, name, ref subterms)) = terms.last() {
+        if *name != atom!("->") || subterms.len() != 2 {
             return;
         }
     } else {
         return;
     }
 
-    if let Some(Term::Clause(_, _, mut subterms, _)) = terms.pop() {
-        let mut conq_terms = VecDeque::from(unfold_by_str(*subterms.pop().unwrap(), ","));
-        let mut pre_cut_terms = VecDeque::from(unfold_by_str(*subterms.pop().unwrap(), ","));
+    if let Some(Term::Clause(_, _, mut subterms)) = terms.pop() {
+        let mut conq_terms = VecDeque::from(unfold_by_str(subterms.pop().unwrap(), atom!(",")));
+        let mut pre_cut_terms = VecDeque::from(unfold_by_str(subterms.pop().unwrap(), atom!(",")));
 
-        conq_terms.push_front(Term::Constant(
+        conq_terms.push_front(Term::Literal(
             Cell::default(),
-            Constant::Atom(clause_name!("blocked_!"), None),
+            Literal::Atom(atom!("blocked_!")),
         ));
 
         while let Some(term) = pre_cut_terms.pop_back() {
@@ -489,37 +473,44 @@ fn check_for_internal_if_then(terms: &mut Vec<Term>) {
         terms.push(fold_by_str(
             conq_terms.into_iter(),
             tail_term,
-            clause_name!(","),
+            atom!(","),
         ));
     }
 }
 
-pub(super) fn setup_declaration<'a>(
-    load_state: &LoadState<'a>,
-    mut terms: Vec<Box<Term>>,
+pub(super) fn setup_declaration<'a, LS: LoadState<'a>>(
+    loader: &mut Loader<'a, LS>,
+    mut terms: Vec<Term>,
 ) -> Result<Declaration, CompilationError> {
-    let term = *terms.pop().unwrap();
-    let atom_tbl = load_state.wam.machine_st.atom_tbl.clone();
+    let term = terms.pop().unwrap();
 
     match term {
-        Term::Clause(_, name, mut terms, _) => match (name.as_str(), terms.len()) {
-            ("dynamic", 1) => {
-                let (name, arity) = setup_predicate_indicator(&mut *terms.pop().unwrap())?;
+        Term::Clause(_, name, mut terms) => match (name, terms.len()) {
+            (atom!("dynamic"), 1) => {
+                let (name, arity) = setup_predicate_indicator(&mut terms.pop().unwrap())?;
                 Ok(Declaration::Dynamic(name, arity))
             }
-            ("module", 2) => Ok(Declaration::Module(setup_module_decl(terms, atom_tbl)?)),
-            ("op", 3) => Ok(Declaration::Op(setup_op_decl(terms, atom_tbl)?)),
-            ("non_counted_backtracking", 1) => {
-                let (name, arity) = setup_predicate_indicator(&mut *terms.pop().unwrap())?;
+            (atom!("module"), 2) => {
+                let atom_tbl = &mut LS::machine_st(&mut loader.payload).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)?))
+            }
+            (atom!("non_counted_backtracking"), 1) => {
+                let (name, arity) = setup_predicate_indicator(&mut terms.pop().unwrap())?;
                 Ok(Declaration::NonCountedBacktracking(name, arity))
             }
-            ("use_module", 1) => Ok(Declaration::UseModule(setup_use_module_decl(terms)?)),
-            ("use_module", 2) => {
+            (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)?;
+
                 Ok(Declaration::UseQualifiedModule(name, exports))
             }
-            ("meta_predicate", 1) => {
-                let (module_name, name, meta_specs) = setup_meta_predicate(terms, load_state)?;
+            (atom!("meta_predicate"), 1) => {
+                let (module_name, name, meta_specs) = setup_meta_predicate(terms, loader)?;
                 Ok(Declaration::MetaPredicate(module_name, name, meta_specs))
             }
             _ => Err(CompilationError::InconsistentEntry),
@@ -529,43 +520,43 @@ pub(super) fn setup_declaration<'a>(
 }
 
 #[inline]
-fn clause_to_query_term<'a>(
-    load_state: &mut LoadState<'a>,
-    name: ClauseName,
-    terms: Vec<Box<Term>>,
-    fixity: Option<SharedOpDesc>,
+fn clause_to_query_term<'a, LS: LoadState<'a>>(
+    loader: &mut Loader<'a, LS>,
+    name: Atom,
+    terms: Vec<Term>,
 ) -> QueryTerm {
-    let ct = load_state.get_clause_type(name, terms.len(), fixity);
+    let ct = loader.get_clause_type(name, terms.len());
     QueryTerm::Clause(Cell::default(), ct, terms, false)
 }
 
 #[inline]
-fn qualified_clause_to_query_term<'a>(
-    load_state: &mut LoadState<'a>,
-    module_name: ClauseName,
-    name: ClauseName,
-    terms: Vec<Box<Term>>,
-    fixity: Option<SharedOpDesc>,
+fn qualified_clause_to_query_term<'a, LS: LoadState<'a>>(
+    loader: &mut Loader<'a, LS>,
+    module_name: Atom,
+    name: Atom,
+    terms: Vec<Term>,
 ) -> QueryTerm {
-    let ct = load_state.get_qualified_clause_type(module_name, name, terms.len(), fixity);
+    let ct = loader.get_qualified_clause_type(module_name, name, terms.len());
     QueryTerm::Clause(Cell::default(), ct, terms, false)
 }
 
 #[derive(Debug)]
 pub(crate) struct Preprocessor {
+    flags: MachineFlags,
     queue: VecDeque<VecDeque<Term>>,
 }
 
 impl Preprocessor {
-    pub(super) fn new() -> Self {
+    pub(super) fn new(flags: MachineFlags) -> Self {
         Preprocessor {
+            flags,
             queue: VecDeque::new(),
         }
     }
 
     fn setup_fact(&mut self, term: Term) -> Result<Term, CompilationError> {
         match term {
-            Term::Clause(..) | Term::Constant(_, Constant::Atom(..)) => Ok(term),
+            Term::Clause(..) | Term::Literal(_, Literal::Atom(..)) => Ok(term),
             _ => Err(CompilationError::InadmissibleFact),
         }
     }
@@ -579,20 +570,17 @@ impl Preprocessor {
             }
         }
 
-        vars.insert(rc_atom!("!"));
+        vars.insert(Rc::new(String::from("!")));
         vars.into_iter()
             .map(|v| Term::Var(Cell::default(), v))
             .collect()
     }
 
     fn fabricate_rule_body(&self, vars: &Vec<Term>, body_term: Term) -> Term {
-        let vars_of_head = vars.iter().cloned().map(Box::new).collect();
-        let head_term = Term::Clause(Cell::default(), clause_name!(""), vars_of_head, None);
+        let head_term = Term::Clause(Cell::default(), atom!(""), vars.clone());
+        let rule = vec![head_term, body_term];
 
-        let rule = vec![Box::new(head_term), Box::new(body_term)];
-        let turnstile = clause_name!(":-");
-
-        Term::Clause(Cell::default(), turnstile, rule, None)
+        Term::Clause(Cell::default(), atom!(":-"), rule)
     }
 
     // the terms form the body of the rule. We create a head, by
@@ -609,16 +597,16 @@ impl Preprocessor {
 
     fn fabricate_disjunct(&self, body_term: Term) -> (JumpStub, VecDeque<Term>) {
         let vars = self.compute_head(&body_term);
-        let results = unfold_by_str(body_term, ";")
+        let results = unfold_by_str(body_term, atom!(";"))
             .into_iter()
             .map(|term| {
-                let mut subterms = unfold_by_str(term, ",");
+                let mut subterms = unfold_by_str(term, atom!(","));
                 mark_cut_variables(&mut subterms);
 
                 check_for_internal_if_then(&mut subterms);
 
                 let term = subterms.pop().unwrap();
-                let clause = fold_by_str(subterms.into_iter(), term, clause_name!(","));
+                let clause = fold_by_str(subterms.into_iter(), term, atom!(","));
 
                 self.fabricate_rule_body(&vars, clause)
             })
@@ -628,80 +616,78 @@ impl Preprocessor {
     }
 
     fn fabricate_if_then(&self, prec: Term, conq: Term) -> (JumpStub, VecDeque<Term>) {
-        let mut prec_seq = unfold_by_str(prec, ",");
-        let comma_sym = clause_name!(",");
-        let cut_sym = atom!("!");
+        let mut prec_seq = unfold_by_str(prec, atom!(","));
+        let comma_sym = atom!(",");
+        let cut_sym = Literal::Atom(atom!("!"));
 
-        prec_seq.push(Term::Constant(Cell::default(), cut_sym));
+        prec_seq.push(Term::Literal(Cell::default(), cut_sym));
 
-        mark_cut_variables_as(&mut prec_seq, clause_name!("blocked_!"));
+        mark_cut_variables_as(&mut prec_seq, atom!("blocked_!"));
 
-        let mut conq_seq = unfold_by_str(conq, ",");
+        let mut conq_seq = unfold_by_str(conq, atom!(","));
 
         mark_cut_variables(&mut conq_seq);
         prec_seq.extend(conq_seq.into_iter());
 
-        let back_term = Box::new(prec_seq.pop().unwrap());
-        let front_term = Box::new(prec_seq.pop().unwrap());
+        let back_term = prec_seq.pop().unwrap();
+        let front_term = prec_seq.pop().unwrap();
 
         let body_term = Term::Clause(
             Cell::default(),
-            comma_sym.clone(),
+            comma_sym,
             vec![front_term, back_term],
-            None,
         );
 
         self.fabricate_rule(fold_by_str(prec_seq.into_iter(), body_term, comma_sym))
     }
 
-    fn to_query_term<'a>(
+    fn to_query_term<'a, LS: LoadState<'a>>(
         &mut self,
-        load_state: &mut LoadState<'a>,
+        loader: &mut Loader<'a, LS>,
         term: Term,
     ) -> Result<QueryTerm, CompilationError> {
         match term {
-            Term::Constant(_, Constant::Atom(name, fixity)) => {
-                if name.as_str() == "!" || name.as_str() == "blocked_!" {
+            Term::Literal(_, Literal::Atom(name)) => {
+                if name == atom!("!") || name == atom!("blocked_!") {
                     Ok(QueryTerm::BlockedCut)
                 } else {
-                    Ok(clause_to_query_term(load_state, name, vec![], fixity))
+                    Ok(clause_to_query_term(loader, name, vec![]))
                 }
             }
-            Term::Constant(_, Constant::Char('!')) => Ok(QueryTerm::BlockedCut),
+            Term::Literal(_, Literal::Char('!')) => Ok(QueryTerm::BlockedCut),
             Term::Var(_, ref v) if v.as_str() == "!" => {
                 Ok(QueryTerm::UnblockedCut(Cell::default()))
             }
-            Term::Clause(r, name, mut terms, fixity) => match (name.as_str(), terms.len()) {
-                (";", 2) => {
-                    let term = Term::Clause(r, name.clone(), terms, fixity);
+            Term::Clause(r, name, mut terms) => match (name, terms.len()) {
+                (atom!(";"), 2) => {
+                    let term = Term::Clause(r, name, terms);
 
                     let (stub, clauses) = self.fabricate_disjunct(term);
                     self.queue.push_back(clauses);
 
                     Ok(QueryTerm::Jump(stub))
                 }
-                ("->", 2) => {
-                    let conq = *terms.pop().unwrap();
-                    let prec = *terms.pop().unwrap();
+                (atom!("->"), 2) => {
+                    let conq = terms.pop().unwrap();
+                    let prec = terms.pop().unwrap();
 
                     let (stub, clauses) = self.fabricate_if_then(prec, conq);
                     self.queue.push_back(clauses);
 
                     Ok(QueryTerm::Jump(stub))
                 }
-                ("\\+", 1) => {
-                    terms.push(Box::new(Term::Constant(
+                (atom!("\\+"), 1) => {
+                    terms.push(Term::Literal(
                         Cell::default(),
-                        Constant::Atom(clause_name!("$fail"), None),
-                    )));
+                        Literal::Atom(atom!("$fail")),
+                    ));
 
-                    let conq =
-                        Term::Constant(Cell::default(), Constant::Atom(clause_name!("true"), None));
+                    let conq = Term::Literal(Cell::default(), Literal::Atom(atom!("true")));
 
-                    let prec = Term::Clause(Cell::default(), clause_name!("->"), terms, None);
-                    let terms = vec![Box::new(prec), Box::new(conq)];
+                    let prec = Term::Clause(Cell::default(), atom!("->"), terms);
+                    let terms = vec![prec, conq];
 
-                    let term = Term::Clause(Cell::default(), clause_name!(";"), terms, None);
+                    let term = Term::Clause(Cell::default(), atom!(";"), terms);
                     let (stub, clauses) = self.fabricate_disjunct(term);
 
                     debug_assert!(clauses.len() > 0);
@@ -709,104 +695,102 @@ impl Preprocessor {
 
                     Ok(QueryTerm::Jump(stub))
                 }
-                ("$get_level", 1) => {
-                    if let Term::Var(_, ref var) = *terms[0] {
+                (atom!("$get_level"), 1) => {
+                    if let Term::Var(_, ref var) = &terms[0] {
                         Ok(QueryTerm::GetLevelAndUnify(Cell::default(), var.clone()))
                     } else {
                         Err(CompilationError::InadmissibleQueryTerm)
                     }
                 }
-                (":", 2) => {
-                    let predicate_name = *terms.pop().unwrap();
-                    let module_name = *terms.pop().unwrap();
+                (atom!(":"), 2) => {
+                    let predicate_name = terms.pop().unwrap();
+                    let module_name = terms.pop().unwrap();
 
                     match (module_name, predicate_name) {
                         (
-                            Term::Constant(_, Constant::Atom(module_name, _)),
-                            Term::Constant(_, Constant::Atom(predicate_name, fixity)),
+                            Term::Literal(_, Literal::Atom(module_name)),
+                            Term::Literal(_, Literal::Atom(predicate_name)),
                         ) => Ok(qualified_clause_to_query_term(
-                            load_state,
+                            loader,
                             module_name,
                             predicate_name,
                             vec![],
-                            fixity,
                         )),
                         (
-                            Term::Constant(_, Constant::Atom(module_name, _)),
-                            Term::Clause(_, name, terms, fixity),
+                            Term::Literal(_, Literal::Atom(module_name)),
+                            Term::Clause(_, name, terms),
                         ) => Ok(qualified_clause_to_query_term(
-                            load_state,
+                            loader,
                             module_name,
                             name,
                             terms,
-                            fixity,
                         )),
                         (module_name, predicate_name) => {
-                            terms.push(Box::new(module_name));
-                            terms.push(Box::new(predicate_name));
+                            terms.push(module_name);
+                            terms.push(predicate_name);
 
-                            Ok(clause_to_query_term(load_state, name, terms, fixity))
+                            Ok(clause_to_query_term(loader, name, terms))
                         }
                     }
                 }
-                _ => Ok(clause_to_query_term(load_state, name, terms, fixity)),
+                _ => Ok(clause_to_query_term(loader, name, terms)),
             },
             Term::Var(..) => Ok(QueryTerm::Clause(
                 Cell::default(),
                 ClauseType::CallN,
-                vec![Box::new(term)],
+                vec![term],
                 false,
             )),
             _ => Err(CompilationError::InadmissibleQueryTerm),
         }
     }
 
-    fn pre_query_term<'a>(
+    fn pre_query_term<'a, LS: LoadState<'a>>(
         &mut self,
-        load_state: &mut LoadState<'a>,
+        loader: &mut Loader<'a, LS>,
         term: Term,
     ) -> Result<QueryTerm, CompilationError> {
         match term {
-            Term::Clause(r, name, mut subterms, fixity) => {
-                if subterms.len() == 1 && name.as_str() == "$call_with_default_policy" {
-                    self.to_query_term(load_state, *subterms.pop().unwrap())
+            Term::Clause(r, name, mut subterms) => {
+                if subterms.len() == 1 && name == atom!("$call_with_default_policy") {
+                    self.to_query_term(loader, subterms.pop().unwrap())
                         .map(|mut query_term| {
                             query_term.set_default_caller();
                             query_term
                         })
                 } else {
-                    let clause = Term::Clause(r, name, subterms, fixity);
-                    self.to_query_term(load_state, clause)
+                    let clause = Term::Clause(r, name, subterms);
+                    self.to_query_term(loader, clause)
                 }
             }
-            _ => self.to_query_term(load_state, term),
+            _ => self.to_query_term(loader, term),
         }
     }
 
-    fn setup_query<'a>(
+    fn setup_query<'a, LS: LoadState<'a>>(
         &mut self,
-        load_state: &mut LoadState<'a>,
-        terms: Vec<Box<Term>>,
+        loader: &mut Loader<'a, LS>,
+        terms: Vec<Term>,
         cut_context: CutContext,
     ) -> Result<Vec<QueryTerm>, CompilationError> {
         let mut query_terms = vec![];
         let mut work_queue = VecDeque::from(terms);
 
         while let Some(term) = work_queue.pop_front() {
-            let mut term = *term;
+            let mut term = term;
 
-            if let Term::Clause(cell, name, terms, op_spec) = term {
-                if name.as_str() == "," && terms.len() == 2 {
-                    let term = Term::Clause(cell, name, terms, op_spec);
-                    let mut subterms = unfold_by_str(term, ",");
+            if let Term::Clause(cell, name, terms) = term {
+                if name == atom!(",") && terms.len() == 2 {
+                    let term = Term::Clause(cell, name, terms);
+                    let mut subterms = unfold_by_str(term, atom!(","));
 
                     while let Some(subterm) = subterms.pop() {
-                        work_queue.push_front(Box::new(subterm));
+                        work_queue.push_front(subterm);
                     }
 
                     continue;
                 } else {
-                    term = Term::Clause(cell, name, terms, op_spec);
+                    term = Term::Clause(cell, name, terms);
                 }
             }
 
@@ -814,30 +798,30 @@ impl Preprocessor {
                 mark_cut_variable(&mut term);
             }
 
-            query_terms.push(self.pre_query_term(load_state, term)?);
+            query_terms.push(self.pre_query_term(loader, term)?);
         }
 
         Ok(query_terms)
     }
 
-    fn setup_rule<'a>(
+    fn setup_rule<'a, LS: LoadState<'a>>(
         &mut self,
-        load_state: &mut LoadState<'a>,
-        mut terms: Vec<Box<Term>>,
+        loader: &mut Loader<'a, LS>,
+        mut terms: Vec<Term>,
         cut_context: CutContext,
     ) -> Result<Rule, CompilationError> {
         let post_head_terms: Vec<_> = terms.drain(1..).collect();
-        let mut query_terms = self.setup_query(load_state, post_head_terms, cut_context)?;
+        let mut query_terms = self.setup_query(loader, post_head_terms, cut_context)?;
 
         let clauses = query_terms.drain(1..).collect();
         let qt = query_terms.pop().unwrap();
 
-        match *terms.pop().unwrap() {
-            Term::Clause(_, name, terms, _) => Ok(Rule {
+        match terms.pop().unwrap() {
+            Term::Clause(_, name, terms) => Ok(Rule {
                 head: (name, terms, qt),
                 clauses,
             }),
-            Term::Constant(_, Constant::Atom(name, _)) => Ok(Rule {
+            Term::Literal(_, Literal::Atom(name)) => Ok(Rule {
                 head: (name, vec![], qt),
                 clauses,
             }),
@@ -845,37 +829,37 @@ impl Preprocessor {
         }
     }
 
-    fn try_term_to_query<'a>(
+    fn try_term_to_query<'a, LS: LoadState<'a>>(
         &mut self,
-        load_state: &mut LoadState<'a>,
-        terms: Vec<Box<Term>>,
+        loader: &mut Loader<'a, LS>,
+        terms: Vec<Term>,
         cut_context: CutContext,
     ) -> Result<TopLevel, CompilationError> {
         Ok(TopLevel::Query(self.setup_query(
-            load_state,
+            loader,
             terms,
             cut_context,
         )?))
     }
 
-    pub(super) fn try_term_to_tl<'a>(
+    pub(super) fn try_term_to_tl<'a, LS: LoadState<'a>>(
         &mut self,
-        load_state: &mut LoadState<'a>,
+        loader: &mut Loader<'a, LS>,
         term: Term,
         cut_context: CutContext,
     ) -> Result<TopLevel, CompilationError> {
         match term {
-            Term::Clause(r, name, terms, fixity) => {
-                if name.as_str() == "?-" {
-                    self.try_term_to_query(load_state, terms, cut_context)
-                } else if name.as_str() == ":-" && terms.len() == 2 {
+            Term::Clause(r, name, terms) => {
+                if name == atom!("?-") {
+                    self.try_term_to_query(loader, terms, cut_context)
+                } else if name == atom!(":-") && terms.len() == 2 {
                     Ok(TopLevel::Rule(self.setup_rule(
-                        load_state,
+                        loader,
                         terms,
                         cut_context,
                     )?))
                 } else {
-                    let term = Term::Clause(r, name, terms, fixity);
+                    let term = Term::Clause(r, name, terms);
                     Ok(TopLevel::Fact(self.setup_fact(term)?))
                 }
             }
@@ -883,30 +867,30 @@ impl Preprocessor {
         }
     }
 
-    fn try_terms_to_tls<'a, I: IntoIterator<Item = Term>>(
+    fn try_terms_to_tls<'a, I: IntoIterator<Item = Term>, LS: LoadState<'a>>(
         &mut self,
-        load_state: &mut LoadState<'a>,
+        loader: &mut Loader<'a, LS>,
         terms: I,
         cut_context: CutContext,
     ) -> Result<VecDeque<TopLevel>, CompilationError> {
         let mut results = VecDeque::new();
 
         for term in terms.into_iter() {
-            results.push_back(self.try_term_to_tl(load_state, term, cut_context)?);
+            results.push_back(self.try_term_to_tl(loader, term, cut_context)?);
         }
 
         Ok(results)
     }
 
-    pub(super) fn parse_queue<'a>(
+    pub(super) fn parse_queue<'a, LS: LoadState<'a>>(
         &mut self,
-        load_state: &mut LoadState<'a>,
+        loader: &mut Loader<'a, LS>,
     ) -> Result<VecDeque<TopLevel>, CompilationError> {
         let mut queue = VecDeque::new();
 
         while let Some(terms) = self.queue.pop_front() {
             let clauses = merge_clauses(&mut self.try_terms_to_tls(
-                load_state,
+                loader,
                 terms,
                 CutContext::HasCutVariable,
             )?)?;

src/machine/stack.rs

@@ -1,16 +1,15 @@
 use core::marker::PhantomData;
 
+use crate::types::*;
+
 use crate::machine::machine_indices::*;
-use crate::machine::raw_block::*;
+use crate::raw_block::*;
 
 use std::mem;
 use std::ops::{Index, IndexMut};
 use std::ptr;
 
-#[derive(Debug)]
-struct StackTraits {}
-
-impl RawBlockTraits for StackTraits {
+impl RawBlockTraits for Stack {
     #[inline]
     fn init_size() -> usize {
         10 * 1024 * 1024
@@ -18,31 +17,23 @@ impl RawBlockTraits for StackTraits {
 
     #[inline]
     fn align() -> usize {
-        mem::align_of::<Addr>()
-    }
-
-    #[inline]
-    fn base_offset(base: *const u8) -> *const u8 {
-        unsafe { base.offset(Self::align() as isize) }
+        mem::align_of::<HeapCellValue>()
     }
 }
 
-const fn prelude_size<Prelude>() -> usize {
-    let size = mem::size_of::<Prelude>();
-    let align = mem::align_of::<Addr>();
-
-    (size & !(align - 1)) + align
+#[inline(always)]
+pub const fn prelude_size<Prelude>() -> usize {
+    mem::size_of::<Prelude>()
 }
 
 #[derive(Debug)]
-pub(crate) struct Stack {
-    buf: RawBlock<StackTraits>,
-    _marker: PhantomData<Addr>,
+pub struct Stack {
+    buf: RawBlock<Stack>,
+    _marker: PhantomData<HeapCellValue>,
 }
 
 impl Drop for Stack {
     fn drop(&mut self) {
-        self.drop_in_place();
         self.buf.deallocate();
     }
 }
@@ -57,7 +48,7 @@ pub(crate) struct AndFramePrelude {
     pub(crate) univ_prelude: FramePrelude,
     pub(crate) e: usize,
     pub(crate) cp: LocalCodePtr,
-    pub(crate) interrupt_cp: LocalCodePtr,
+    pub(crate) interrupt_cp: LocalCodePtr, // TODO: get rid of it!
 }
 
 #[derive(Debug)]
@@ -67,22 +58,22 @@ pub(crate) struct AndFrame {
 
 impl AndFrame {
     pub(crate) fn size_of(num_cells: usize) -> usize {
-        prelude_size::<AndFramePrelude>() + num_cells * mem::size_of::<Addr>()
+        prelude_size::<AndFramePrelude>() + num_cells * mem::size_of::<HeapCellValue>()
     }
 }
 
 impl Index<usize> for AndFrame {
-    type Output = Addr;
+    type Output = HeapCellValue;
 
     fn index(&self, index: usize) -> &Self::Output {
         let prelude_offset = prelude_size::<AndFramePrelude>();
-        let index_offset = (index - 1) * mem::size_of::<Addr>();
+        let index_offset = (index - 1) * mem::size_of::<HeapCellValue>();
 
         unsafe {
             let ptr = mem::transmute::<&AndFrame, *const u8>(self);
             let ptr = ptr as usize + prelude_offset + index_offset;
 
-            &*(ptr as *const Addr)
+            &*(ptr as *const HeapCellValue)
         }
     }
 }
@@ -90,13 +81,35 @@ impl Index<usize> for AndFrame {
 impl IndexMut<usize> for AndFrame {
     fn index_mut(&mut self, index: usize) -> &mut Self::Output {
         let prelude_offset = prelude_size::<AndFramePrelude>();
-        let index_offset = (index - 1) * mem::size_of::<Addr>();
+        let index_offset = (index - 1) * mem::size_of::<HeapCellValue>();
 
         unsafe {
             let ptr = mem::transmute::<&mut AndFrame, *const u8>(self);
             let ptr = ptr as usize + prelude_offset + index_offset;
 
-            &mut *(ptr as *mut Addr)
+            &mut *(ptr as *mut HeapCellValue)
+        }
+    }
+}
+
+impl Index<usize> for Stack {
+    type Output = HeapCellValue;
+
+    #[inline]
+    fn index(&self, index: usize) -> &Self::Output {
+        unsafe {
+            let ptr = self.buf.base as usize + index;
+            &*(ptr as *const HeapCellValue)
+        }
+    }
+}
+
+impl IndexMut<usize> for Stack {
+    #[inline]
+    fn index_mut(&mut self, index: usize) -> &mut Self::Output {
+        unsafe {
+            let ptr = self.buf.base as usize + index;
+            &mut *(ptr as *mut HeapCellValue)
         }
     }
 }
@@ -119,18 +132,18 @@ pub(crate) struct OrFrame {
 }
 
 impl Index<usize> for OrFrame {
-    type Output = Addr;
+    type Output = HeapCellValue;
 
     #[inline]
     fn index(&self, index: usize) -> &Self::Output {
         let prelude_offset = prelude_size::<OrFramePrelude>();
-        let index_offset = index * mem::size_of::<Addr>();
+        let index_offset = index * mem::size_of::<HeapCellValue>();
 
         unsafe {
             let ptr = mem::transmute::<&OrFrame, *const u8>(self);
             let ptr = ptr as usize + prelude_offset + index_offset;
 
-            &*(ptr as *const Addr)
+            &*(ptr as *const HeapCellValue)
         }
     }
 }
@@ -139,20 +152,20 @@ impl IndexMut<usize> for OrFrame {
     #[inline]
     fn index_mut(&mut self, index: usize) -> &mut Self::Output {
         let prelude_offset = prelude_size::<OrFramePrelude>();
-        let index_offset = index * mem::size_of::<Addr>();
+        let index_offset = index * mem::size_of::<HeapCellValue>();
 
         unsafe {
             let ptr = mem::transmute::<&mut OrFrame, *const u8>(self);
             let ptr = ptr as usize + prelude_offset + index_offset;
 
-            &mut *(ptr as *mut Addr)
+            &mut *(ptr as *mut HeapCellValue)
         }
     }
 }
 
 impl OrFrame {
     pub(crate) fn size_of(num_cells: usize) -> usize {
-        prelude_size::<OrFramePrelude>() + num_cells * mem::size_of::<Addr>()
+        prelude_size::<OrFramePrelude>() + num_cells * mem::size_of::<HeapCellValue>()
     }
 }
 
@@ -164,26 +177,39 @@ impl Stack {
         }
     }
 
+    #[inline(always)]
+    unsafe fn alloc(&mut self, frame_size: usize) -> *mut u8 {
+        loop {
+            let ptr = self.buf.alloc(frame_size);
+
+            if ptr.is_null() {
+                self.buf.grow();
+            } else {
+                return ptr;
+            }
+        }
+    }
+
     pub(crate) fn allocate_and_frame(&mut self, num_cells: usize) -> usize {
         let frame_size = AndFrame::size_of(num_cells);
 
         unsafe {
-            let new_top = self.buf.new_block(frame_size);
-            let e = self.buf.top as usize - self.buf.base as usize;
+            let e = self.buf.ptr as usize - self.buf.base as usize;
+            let new_ptr = self.alloc(frame_size);
+            let mut offset = prelude_size::<AndFramePrelude>();
 
             for idx in 0..num_cells {
-                let offset = prelude_size::<AndFramePrelude>() + idx * mem::size_of::<Addr>();
                 ptr::write(
-                    (self.buf.top as usize + offset) as *mut Addr,
-                    Addr::StackCell(e, idx + 1),
+                    (new_ptr as usize + offset) as *mut HeapCellValue,
+                    stack_loc_as_cell!(AndFrame, e, idx + 1),
                 );
+
+                offset += mem::size_of::<HeapCellValue>();
             }
 
-            let and_frame = &mut *(self.buf.top as *mut AndFrame);
+            let and_frame = &mut *(new_ptr as *mut AndFrame);
             and_frame.prelude.univ_prelude.num_cells = num_cells;
 
-            self.buf.top = new_top;
-
             e
         }
     }
@@ -192,27 +218,27 @@ impl Stack {
         let frame_size = OrFrame::size_of(num_cells);
 
         unsafe {
-            let new_top = self.buf.new_block(frame_size);
-            let b = self.buf.top as usize - self.buf.base as usize;
+            let b = self.buf.ptr as usize - self.buf.base as usize;
+            let new_ptr = self.alloc(frame_size);
+            let mut offset = prelude_size::<OrFramePrelude>();
 
             for idx in 0..num_cells {
-                let offset = prelude_size::<OrFramePrelude>() + idx * mem::size_of::<Addr>();
                 ptr::write(
-                    (self.buf.top as usize + offset) as *mut Addr,
-                    Addr::StackCell(b, idx),
+                    (new_ptr as usize + offset) as *mut HeapCellValue,
+                    stack_loc_as_cell!(OrFrame, b, idx),
                 );
+
+                offset += mem::size_of::<HeapCellValue>();
             }
 
-            let or_frame = &mut *(self.buf.top as *mut OrFrame);
+            let or_frame = &mut *(new_ptr as *mut OrFrame);
             or_frame.prelude.univ_prelude.num_cells = num_cells;
 
-            self.buf.top = new_top;
-
             b
         }
     }
 
-    #[inline]
+    #[inline(always)]
     pub(crate) fn index_and_frame(&self, e: usize) -> &AndFrame {
         unsafe {
             let ptr = self.buf.base as usize + e;
@@ -220,7 +246,7 @@ impl Stack {
         }
     }
 
-    #[inline]
+    #[inline(always)]
     pub(crate) fn index_and_frame_mut(&mut self, e: usize) -> &mut AndFrame {
         unsafe {
             let ptr = self.buf.base as usize + e;
@@ -228,7 +254,7 @@ impl Stack {
         }
     }
 
-    #[inline]
+    #[inline(always)]
     pub(crate) fn index_or_frame(&self, b: usize) -> &OrFrame {
         unsafe {
             let ptr = self.buf.base as usize + b;
@@ -236,7 +262,7 @@ impl Stack {
         }
     }
 
-    #[inline]
+    #[inline(always)]
     pub(crate) fn index_or_frame_mut(&mut self, b: usize) -> &mut OrFrame {
         unsafe {
             let ptr = self.buf.base as usize + b;
@@ -244,31 +270,65 @@ impl Stack {
         }
     }
 
-    #[inline]
+    #[inline(always)]
     pub(crate) fn truncate(&mut self, b: usize) {
-        if b == 0 {
-            self.inner_truncate(mem::align_of::<Addr>());
-        } else {
-            self.inner_truncate(b);
+        let base = self.buf.base as usize + b;
+
+        if base < self.buf.ptr as usize {
+            self.buf.ptr = base as *mut _;
         }
     }
-
-    #[inline]
-    fn inner_truncate(&mut self, b: usize) {
-        let base = b + self.buf.base as usize;
-
-        if base < self.buf.top as usize {
-            self.buf.top = base as *const _;
-        }
-    }
-
-    pub(crate) fn drop_in_place(&mut self) {
-        self.truncate(mem::align_of::<Addr>());
-
-        debug_assert!(if self.buf.top.is_null() {
-            self.buf.top == self.buf.base
-        } else {
-            self.buf.top as usize == self.buf.base as usize + mem::align_of::<Addr>()
-        });
-    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    use crate::machine::mock_wam::*;
+
+    #[test]
+    fn stack_tests() {
+        let mut wam = MockWAM::new();
+
+        let e = wam.machine_st.stack.allocate_and_frame(10); // create an AND frame!
+        let and_frame = wam.machine_st.stack.index_and_frame_mut(e);
+
+        assert_eq!(
+            e,
+            0// 10 * mem::size_of::<HeapCellValue>() + prelude_size::<AndFrame>()
+        );
+
+        assert_eq!(and_frame.prelude.univ_prelude.num_cells, 10);
+
+        for idx in 0..10 {
+            assert_eq!(and_frame[idx + 1], stack_loc_as_cell!(AndFrame, e, idx + 1));
+        }
+
+        and_frame[5] = empty_list_as_cell!();
+
+        assert_eq!(and_frame[5], empty_list_as_cell!());
+
+        let b = wam.machine_st.stack.allocate_or_frame(5);
+
+        let or_frame = wam.machine_st.stack.index_or_frame_mut(b);
+
+        for idx in 0..5 {
+            assert_eq!(or_frame[idx], stack_loc_as_cell!(OrFrame, b, idx));
+        }
+
+        let next_e = wam.machine_st.stack.allocate_and_frame(9); // create an AND frame!
+        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));
+        }
+
+        let and_frame = wam.machine_st.stack.index_and_frame(e);
+        assert_eq!(and_frame[5], empty_list_as_cell!());
+
+        assert_eq!(
+            wam.machine_st.stack[stack_loc!(AndFrame, e, 5)],
+            empty_list_as_cell!()
+        );
+    }
 }

src/machine/term_stream.rs

@@ -1,48 +1,53 @@
-use prolog_parser::ast::*;
-use prolog_parser::parser::*;
-
-use crate::machine::machine_errors::CompilationError;
+use crate::forms::*;
 use crate::machine::*;
+use crate::machine::load_state::*;
+use crate::machine::loader::*;
+use crate::machine::machine_errors::*;
+use crate::parser::ast::*;
+use crate::parser::parser::*;
+
+use crate::predicate_queue;
 
 use indexmap::IndexSet;
 
 use std::collections::VecDeque;
 use std::fmt;
 
-pub(crate) trait TermStream: Sized {
-    type Evacuable;
+pub struct LoadStatePayload<TS> {
+    pub term_stream: TS,
+    pub(super) compilation_target: CompilationTarget,
+    pub(super) retraction_info: RetractionInfo,
+    pub(super) module_op_exports: ModuleOpExports,
+    pub(super) non_counted_bt_preds: IndexSet<PredicateKey>,
+    pub(super) predicates: PredicateQueue,
+    pub(super) clause_clauses: Vec<(Term, Term)>,
+}
 
+pub trait TermStream: Sized {
     fn next(&mut self, op_dir: &CompositeOpDir) -> Result<Term, CompilationError>;
     fn eof(&mut self) -> Result<bool, CompilationError>;
     fn listing_src(&self) -> &ListingSource;
-    fn evacuate<'a>(loader: Loader<'a, Self>) -> Result<Self::Evacuable, SessionError>;
 }
 
 #[derive(Debug)]
-pub(super) struct BootstrappingTermStream<'a> {
+pub struct BootstrappingTermStream<'a> {
     listing_src: ListingSource,
-    parser: Parser<'a, Stream>,
+    pub(super) parser: Parser<'a, Stream>,
 }
 
 impl<'a> BootstrappingTermStream<'a> {
     #[inline]
-    pub(super) fn from_prolog_stream(
-        stream: &'a mut PrologStream,
-        atom_tbl: TabledData<Atom>,
-        flags: MachineFlags,
+    pub(super) fn from_char_reader(
+        stream: Stream,
+        machine_st: &'a mut MachineState,
         listing_src: ListingSource,
     ) -> Self {
-        let parser = Parser::new(stream, atom_tbl, flags);
-        Self {
-            parser,
-            listing_src,
-        }
+        let parser = Parser::new(stream, machine_st);
+        Self { parser, listing_src }
     }
 }
 
 impl<'a> TermStream for BootstrappingTermStream<'a> {
-    type Evacuable = CompilationTarget;
-
     #[inline]
     fn next(&mut self, op_dir: &CompositeOpDir) -> Result<Term, CompilationError> {
         self.parser.reset();
@@ -61,24 +66,9 @@ impl<'a> TermStream for BootstrappingTermStream<'a> {
     fn listing_src(&self) -> &ListingSource {
         &self.listing_src
     }
-
-    fn evacuate(mut loader: Loader<Self>) -> Result<Self::Evacuable, SessionError> {
-        if !loader.predicates.is_empty() {
-            loader.compile_and_submit()?;
-        }
-
-        loader
-            .load_state
-            .retraction_info
-            .reset(loader.load_state.wam.code_repo.code.len());
-
-        loader.load_state.remove_module_op_exports();
-
-        Ok(loader.load_state.compilation_target.take())
-    }
 }
 
-pub(crate) struct LiveTermStream {
+pub struct LiveTermStream {
     pub(super) term_queue: VecDeque<Term>,
     pub(super) listing_src: ListingSource,
 }
@@ -93,28 +83,18 @@ impl LiveTermStream {
     }
 }
 
-pub(crate) struct LoadStatePayload {
-    pub(super) term_stream: LiveTermStream,
-    pub(super) compilation_target: CompilationTarget,
-    pub(super) retraction_info: RetractionInfo,
-    pub(super) module_op_exports: Vec<(OpDecl, Option<(usize, Specifier)>)>,
-    pub(super) non_counted_bt_preds: IndexSet<PredicateKey>,
-    pub(super) predicates: PredicateQueue,
-    pub(super) clause_clauses: Vec<(Term, Term)>,
-}
-
-impl fmt::Debug for LoadStatePayload {
+impl<TS> fmt::Debug for LoadStatePayload<TS> {
     fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
         write!(fmt, "LoadStatePayload")
     }
 }
 
-impl LoadStatePayload {
-    pub(super) fn new(wam: &Machine) -> Self {
+impl<TS> LoadStatePayload<TS> {
+    pub(super) fn new(code_repo_len: usize, term_stream: TS) -> Self {
         Self {
-            term_stream: LiveTermStream::new(ListingSource::User),
+            term_stream,
             compilation_target: CompilationTarget::default(),
-            retraction_info: RetractionInfo::new(wam.code_repo.code.len()),
+            retraction_info: RetractionInfo::new(code_repo_len),
             module_op_exports: vec![],
             non_counted_bt_preds: IndexSet::new(),
             predicates: predicate_queue![],
@@ -124,8 +104,6 @@ impl LoadStatePayload {
 }
 
 impl TermStream for LiveTermStream {
-    type Evacuable = LoadStatePayload;
-
     #[inline]
     fn next(&mut self, _: &CompositeOpDir) -> Result<Term, CompilationError> {
         Ok(self.term_queue.pop_front().unwrap())
@@ -140,9 +118,4 @@ impl TermStream for LiveTermStream {
     fn listing_src(&self) -> &ListingSource {
         &self.listing_src
     }
-
-    #[inline]
-    fn evacuate(loader: Loader<Self>) -> Result<LoadStatePayload, SessionError> {
-        Ok(loader.to_load_state_payload())
-    }
 }