bug fixes on LCO, backtracking.

src/main.rs

@@ -34,7 +34,7 @@ mod tests {
         submit(&mut wam, "p(Z, Z).");
         submit(&mut wam, "clouds(are, nice).");
 
-        // submit returns true on failure, false on success.
+        // submit returns false on failure, true on success.
         assert_eq!(submit(&mut wam, "?- p(Z, Z)."), true);
         assert_eq!(submit(&mut wam, "?- p(Z, z)."), true);
         assert_eq!(submit(&mut wam, "?- p(Z, w)."), true);

src/prolog/ast.rs

@@ -317,7 +317,7 @@ pub enum Term {
 pub enum InlinedQueryTerm {
     CompareNumber(CompareNumberQT, Vec<Box<Term>>),
     IsAtomic(Vec<Box<Term>>),
-    IsVar(Vec<Box<Term>>)
+    IsVar(Vec<Box<Term>>),
 }
 
 impl InlinedQueryTerm {
@@ -325,7 +325,7 @@ impl InlinedQueryTerm {
         match self {
             &InlinedQueryTerm::CompareNumber(_, _) => 2,
             &InlinedQueryTerm::IsAtomic(_) => 1,
-            &InlinedQueryTerm::IsVar(_) => 1                
+            &InlinedQueryTerm::IsVar(_) => 1,
         }
     }
 }
@@ -344,8 +344,8 @@ pub enum QueryTerm {
     CallN(Vec<Box<Term>>),
     Catch(Vec<Box<Term>>),
     Cut,
-    Is(Vec<Box<Term>>),
     Inlined(InlinedQueryTerm),
+    Is(Vec<Box<Term>>),
     Term(Term),
     Throw(Vec<Box<Term>>)
 }
@@ -756,8 +756,6 @@ impl ControlInstruction {
             &ControlInstruction::ThrowExecute => true,
             &ControlInstruction::Goto(_, _) => true,
             &ControlInstruction::Proceed => true,
-            &ControlInstruction::IsCall(_, _) => true,
-            &ControlInstruction::IsExecute(_, _) => true,
             _ => false
         }
     }
@@ -963,10 +961,6 @@ pub struct Heap {
 }
 
 impl Heap {
-    pub fn new() -> Self {
-        Heap { heap: vec![], h : 0 }
-    }
-
     pub fn with_capacity(cap: usize) -> Self {
         Heap { heap: vec![HeapCellValue::Str(0); cap], h: 0 }
     }

src/prolog/codegen.rs

@@ -280,12 +280,12 @@ impl<'a, TermMarker: Allocator<'a>> CodeGenerator<'a, TermMarker>
                     *ctrl = ControlInstruction::Execute(name, arity),
                 ControlInstruction::CallN(arity) =>
                     *ctrl = ControlInstruction::ExecuteN(arity),               
-                ControlInstruction::IsCall(r, at) =>
-                    *ctrl = ControlInstruction::IsExecute(r, at),
                 ControlInstruction::CatchCall =>
                     *ctrl = ControlInstruction::CatchExecute,
                 ControlInstruction::ThrowCall =>
                     *ctrl = ControlInstruction::ThrowExecute,
+                ControlInstruction::IsCall(r, at) =>
+                    *ctrl = ControlInstruction::IsExecute(r, at),
                 ControlInstruction::Proceed => {},
                 _ => dealloc_index += 1 // = code.len()
             }
@@ -376,10 +376,8 @@ impl<'a, TermMarker: Allocator<'a>> CodeGenerator<'a, TermMarker>
                             Line::Cut(CutInstruction::Cut(is_terminal))
                         });
                     },
-                    &QueryTerm::Inlined(ref term) =>
-                        self.compile_inlined(term, term_loc, code)?,
                     &QueryTerm::Is(ref terms) => {
-                        let (mut acode, at) = try!(self.call_arith_eval(terms[1].as_ref(), 1));
+                        let (mut acode, at) = self.call_arith_eval(terms[1].as_ref(), 1)?;
                         code.append(&mut acode);
                         
                         match terms[0].as_ref() {
@@ -405,11 +403,20 @@ impl<'a, TermMarker: Allocator<'a>> CodeGenerator<'a, TermMarker>
                                                                temp_v!(1))]);
                                 code.push(is_call!(temp_v!(1), at.unwrap_or(interm!(1))));
                             },
+                            &Term::Constant(_, Constant::Rational(ref r)) => {
+                                let r = r.clone();
+                                code.push(query![put_constant!(Level::Shallow,
+                                                               Constant::Rational(r),
+                                                               temp_v!(1))]);
+                                code.push(is_call!(temp_v!(1), at.unwrap_or(interm!(1))));
+                            },
                             _ => {
                                 code.push(fail!());
                             }
                         }
                     },
+                    &QueryTerm::Inlined(ref term) =>
+                        self.compile_inlined(term, term_loc, code)?,
                     _ if chunk_num == 0 => {
                         self.marker.reset_arg(term.arity());
 

src/prolog/fixtures.rs

@@ -279,7 +279,7 @@ impl<'a> VariableFixtures<'a>
     {
         for term_ref in head.breadth_first_iter() {
             match term_ref {
-                TermRef::Var(_, cell, _) => {
+                TermRef::Var(Level::Shallow, cell, _) => {
                     unsafe_vars.remove(&cell.get().norm());
                 },
                 _ => {}

src/prolog/io.rs

@@ -114,16 +114,16 @@ impl fmt::Display for ControlInstruction {
                 write!(f, "execute {}/{}", name, arity),
             &ControlInstruction::Goto(p, arity) =>
                 write!(f, "goto {}/{}", p, arity),
+            &ControlInstruction::IsCall(r, ref at) =>
+                write!(f, "is_call {}, {}", r, at),
+            &ControlInstruction::IsExecute(r, ref at) =>
+                write!(f, "is_execute {}, {}", r, at),
             &ControlInstruction::Proceed =>
                 write!(f, "proceed"),
             &ControlInstruction::ThrowCall =>
                 write!(f, "call_throw"),
             &ControlInstruction::ThrowExecute =>
                 write!(f, "execute_throw"),
-            &ControlInstruction::IsCall(r, ref at) =>
-                write!(f, "is_call {}, {}", r, at),
-            &ControlInstruction::IsExecute(r, ref at) =>
-                write!(f, "is_execute {}, {}", r, at),
         }
     }
 }

src/prolog/machine.rs

@@ -11,6 +11,7 @@ use prolog::or_stack::*;
 use prolog::ordered_float::OrderedFloat;
 use prolog::fixtures::*;
 
+use std::cmp::max;
 use std::collections::HashMap;
 use std::ops::{Index, IndexMut};
 use std::vec::Vec;
@@ -325,6 +326,7 @@ impl Machine {
 
                     self.ms.execute_fact_instr(&fact_instr);
                 }
+                
                 self.ms.p += 1;
             },
             &Line::Indexing(ref indexing_instr) =>
@@ -339,6 +341,7 @@ impl Machine {
 
                     self.ms.execute_query_instr(&query_instr);
                 }
+                
                 self.ms.p += 1;
             }
         }
@@ -398,6 +401,7 @@ impl Machine {
             match var_data {
                 &VarData::Perm(_) => {
                     let e = self.ms.e;
+
                     let r = var_data.as_reg_type().reg_num();
                     let addr = self.ms.and_stack[e][r].clone();
 
@@ -641,8 +645,9 @@ impl MachineState {
         }
     }
 
-    fn num_frames(&self) -> usize {
+    fn next_global_index(&self) -> usize {
-        self.and_stack.len() + self.or_stack.len()
+        max(if self.and_stack.len() > 0 { self.and_stack[self.e].global_index } else { 0 },
+            if self.b > 0 { self.or_stack[self.b - 1].global_index } else { 0 }) + 1
     }
 
     fn store(&self, a: Addr) -> Addr {
@@ -860,7 +865,7 @@ impl MachineState {
         match at {
             &ArithmeticTerm::Reg(r) => {
                 let addr = self[r].clone();
-                let item = self.deref(addr);
+                let item = self.store(self.deref(addr));
 
                 match item {
                     Addr::Con(Constant::Integer(bi)) =>
@@ -1663,6 +1668,7 @@ impl MachineState {
 
                         if nb > 0 && self.or_stack[b].b == nb {
                             self.b = self.or_stack[nb - 1].b;
+                            self.or_stack.truncate(self.b);
                         }
 
                         self.p += 1;
@@ -1691,6 +1697,8 @@ impl MachineState {
             },
             &BuiltInInstruction::UnwindStack => {
                 self.b = self.block;
+                self.or_stack.truncate(self.b);
+
                 self.fail = true;
             },
             &BuiltInInstruction::IsAtomic(r) => {
@@ -1732,35 +1740,33 @@ impl MachineState {
     {
         match instr {
             &ControlInstruction::Allocate(num_cells) => {
-                if let Some(ref or_fr) = self.or_stack.top() {
+                let gi = self.next_global_index();
-                    let and_gi = if self.and_stack.len() > self.e {
-                        self.and_stack[self.e].global_index
-                    } else {
-                        0
-                    };
 
-                    if and_gi <= or_fr.global_index {
+                self.p += 1;
-                        self.e = or_fr.e;
+                
+                if self.e + 1 < self.and_stack.len() {
+                    let and_gi = self.and_stack[self.e].global_index;
+                    let or_gi = self.or_stack.top()
+                        .map(|or_fr| or_fr.global_index)
+                        .unwrap_or(0);
+
+                    if and_gi > or_gi {
+                        let index = self.e + 1;
+
+                        self.and_stack[index].e  = self.e;
+                        self.and_stack[index].cp = self.cp;
+                        self.and_stack[index].global_index = gi;
+                        
+                        self.and_stack.resize(index, num_cells);
+
+                        self.e = index;
+                        
+                        return;
                     }
                 }
                 
-                if self.e + 1 < self.and_stack.len() {
+                self.and_stack.push(gi, self.e, self.cp, num_cells);
-                    let index = self.e + 1;
+                self.e = self.and_stack.len() - 1;
-
-                    self.and_stack[index].e  = self.e;
-                    self.and_stack[index].cp = self.cp;
-
-                    self.and_stack.resize(index, num_cells);
-
-                    self.e = index;
-                } else {
-                    let num_frames = self.num_frames();
-
-                    self.and_stack.push(num_frames + 1, self.e, self.cp, num_cells);
-                    self.e = self.and_stack.len() - 1;
-                };
-
-                self.p += 1;
             },
             &ControlInstruction::Call(ref name, arity, _) =>
                 self.try_call_predicate(code_dir, name.clone(), arity),
@@ -1798,15 +1804,6 @@ impl MachineState {
                 self.b0 = self.b;
                 self.p  = CodePtr::DirEntry(p);
             },
-            &ControlInstruction::Proceed =>
-                self.p = self.cp,
-            &ControlInstruction::ThrowCall => {
-                self.cp = self.p + 1;
-                self.goto_throw();
-            },
-            &ControlInstruction::ThrowExecute => {
-                self.goto_throw();
-            },            
             &ControlInstruction::IsCall(r, ref at) => {
                 let a1 = self[r].clone();
                 let a2 = try_or_fail!(self, self.get_number(at));
@@ -1820,7 +1817,16 @@ impl MachineState {
 
                 self.unify(a1, Addr::Con(Constant::from(a2)));                
                 self.p = self.cp;
-            }
+            },
+            &ControlInstruction::Proceed =>
+                self.p = self.cp,
+            &ControlInstruction::ThrowCall => {
+                self.cp = self.p + 1;
+                self.goto_throw();
+            },
+            &ControlInstruction::ThrowExecute => {
+                self.goto_throw();
+            },
         };
     }
 
@@ -1829,9 +1835,9 @@ impl MachineState {
         match instr {
             &IndexedChoiceInstruction::Try(l) => {
                 let n = self.num_of_args;
-                let num_frames = self.num_frames();
+                let gi = self.next_global_index();
                 
-                self.or_stack.push(num_frames + 1,
+                self.or_stack.push(gi,
                                    self.e,
                                    self.cp,
                                    self.b,
@@ -1899,7 +1905,7 @@ impl MachineState {
                 self.heap.truncate(self.or_stack[b].h);
                 self.b = self.or_stack[b].b;
 
-                self.or_stack.pop();
+                self.or_stack.truncate(self.b);
 
                 self.hb = self.heap.h;
                 self.p += l;
@@ -1912,9 +1918,9 @@ impl MachineState {
         match instr {
             &ChoiceInstruction::TryMeElse(offset) => {
                 let n = self.num_of_args;
-                let num_frames = self.num_frames();
+                let gi = self.next_global_index();
                 
-                self.or_stack.push(num_frames + 1,
+                self.or_stack.push(gi,
                                    self.e,
                                    self.cp,
                                    self.b,
@@ -1983,7 +1989,7 @@ impl MachineState {
 
                 self.b = self.or_stack[b].b;
 
-                self.or_stack.pop();
+                self.or_stack.truncate(self.b);
 
                 self.hb = self.heap.h;
                 self.p += 1;

src/prolog/macros.rs

@@ -135,14 +135,6 @@ macro_rules! is_var {
     )
 }
 
-/*
-macro_rules! retry_me_else {
-    ($o:expr) => (
-        Line::Choice(ChoiceInstruction::RetryMeElse($o))
-    )
-}
- */
-
 macro_rules! trust_me {
     () => (
         Line::Choice(ChoiceInstruction::TrustMe)

src/prolog/or_stack.rs

@@ -78,8 +78,10 @@ impl OrStack {
         self.0.last()
     }
 
-    pub fn pop(&mut self) {
+    // truncate expects a 1-indexed new_b, ie.
-        self.0.pop();
+    // the value b of MachineState.
+    pub fn truncate(&mut self, new_b: usize) {
+        self.0.truncate(new_b);
     }
     
     pub fn is_empty(&self) -> bool {