correct ',', backtrack bugs

src/prolog/ast.rs

@@ -724,8 +724,7 @@ pub enum BuiltInInstruction {
     IsVar(RegType),
     ResetBlock,
     SetBall,
-    SetNeckCutPoint(RegType),
+    SetCutPoint(RegType),
-    SetNonNeckCutPoint(RegType),
     Succeed,
     Unify,
     UnwindStack

src/prolog/builtins.rs

@@ -122,36 +122,40 @@ fn get_builtins() -> Code {
                get_structure!(String::from(","), 2, temp_v!(2)),
                unify_variable!(temp_v!(1)),
                unify_variable!(temp_v!(2))],
-         set_neck_cut!(temp_v!(3)),
+         set_cp!(temp_v!(3)),
          goto!(83, 3),
          retry_me_else!(4),
          fact![get_constant!(Constant::from("!"), temp_v!(1)),
                get_constant!(Constant::from("!"), temp_v!(2))],
-         set_neck_cut!(temp_v!(3)),
+         set_cp!(temp_v!(3)),
          proceed!(),
          trust_me!(),
          fact![get_constant!(Constant::from("!"), temp_v!(1))],
-         set_neck_cut!(temp_v!(3)),
+         set_cp!(temp_v!(3)),
          query![put_value!(temp_v!(2), 1)],
          execute_n!(1),
          retry_me_else!(8),
-         allocate!(2),
+         allocate!(3),
          fact![get_structure!(String::from(","), 2, temp_v!(2)),
                unify_variable!(perm_v!(2)),
-               unify_variable!(perm_v!(1))],
+               unify_variable!(perm_v!(1)),
+               get_var_in_fact!(perm_v!(3), 3)],
          neck_cut!(),
          call_n!(1),
          query![put_unsafe_value!(2, 1),
-                put_unsafe_value!(1, 2)],
+                put_unsafe_value!(1, 2),
+                put_value!(perm_v!(3), 3)],
          deallocate!(),
          goto!(83, 3),
-         retry_me_else!(9),
+         retry_me_else!(10),
          allocate!(1),
          get_level!(),
-         fact![get_constant!(Constant::from("!"), temp_v!(2))],
+         fact![get_constant!(Constant::from("!"), temp_v!(2)),
+               get_var_in_fact!(perm_v!(1), 3)],
          neck_cut!(),
          call_n!(1),
-         set_non_neck_cut!(temp_v!(3)),
+         query![put_value!(perm_v!(1), 1)],
+         set_cp!(temp_v!(1)),
          deallocate!(),
          proceed!(),
          trust_me!(),
@@ -161,7 +165,7 @@ fn get_builtins() -> Code {
          query![put_value!(perm_v!(1), 1)],
          deallocate!(),
          execute_n!(1),
-         allocate!(2), // (->)/2, 125.
+         allocate!(2), // (->)/2, 126.
          get_level!(),
          fact![get_var_in_fact!(perm_v!(2), 2)],
          call_n!(1),
@@ -235,7 +239,7 @@ pub fn build_code_dir() -> (Code, CodeDir, OpDir)
 
     code_dir.insert((String::from(";"), 2), (PredicateKeyType::BuiltIn, 76));
     code_dir.insert((String::from(","), 2), (PredicateKeyType::BuiltIn, 81));
-    code_dir.insert((String::from("->"), 2), (PredicateKeyType::BuiltIn, 125));
+    code_dir.insert((String::from("->"), 2), (PredicateKeyType::BuiltIn, 126));
 
     (builtin_code, code_dir, op_dir)
 }

src/prolog/io.rs

@@ -172,10 +172,8 @@ impl fmt::Display for BuiltInInstruction {
                 write!(f, "reset_block"),
             &BuiltInInstruction::SetBall =>
                 write!(f, "set_ball"),
-            &BuiltInInstruction::SetNeckCutPoint(r) =>
+            &BuiltInInstruction::SetCutPoint(r) =>
-                write!(f, "set_neck_cp {}", r),
+                write!(f, "set_cp {}", r),
-            &BuiltInInstruction::SetNonNeckCutPoint(r) =>
-                write!(f, "set_non_neck_cp {}", r),
             &BuiltInInstruction::Succeed =>
                 write!(f, "true"),
             &BuiltInInstruction::UnwindStack =>

src/prolog/machine.rs

@@ -349,29 +349,19 @@ impl Machine {
 
     fn backtrack(&mut self)
     {
-        let b0 = self.ms
+        if self.ms.b > 0 {
-            .or_stack
-            .top()
-            .map(|fr| fr.b0)
-            .unwrap_or(0);
-
-        let p = if self.ms.b > 0 {
             let b = self.ms.b - 1;
-            self.ms.or_stack[b].bp
+            
+            self.ms.b0 = self.ms.or_stack[b].b0;
+            self.ms.p  = self.ms.or_stack[b].bp;
+
+            if let CodePtr::TopLevel(_, p) = self.ms.p {
+                self.ms.fail = p == 0;
+            } else {
+                self.ms.fail = false;
+            }
         } else {
             self.ms.p = CodePtr::TopLevel(0, 0);            
-            return;
-        };
-
-        self.ms.p = p;
-
-        if let CodePtr::TopLevel(_, p) = p {
-            self.ms.fail = p == 0;
-            self.ms.b0 = b0;
-
-            return;
-        } else {
-            self.ms.fail = false;
         }
     }
 
@@ -1665,24 +1655,19 @@ impl MachineState {
 
                 self.p += 1;
             },
-            &BuiltInInstruction::SetNeckCutPoint(r) => {
+            &BuiltInInstruction::SetCutPoint(r) => {
                 let addr = self.store(self.deref(self[r].clone()));
 
                 match addr {
                     Addr::Con(Constant::Usize(nb)) => {
-                        self.b = nb;
+                        self.b0 = nb;
-                        self.neck_cut();
-                    },
-                    _ => self.fail = true
-                };
-            },
-            &BuiltInInstruction::SetNonNeckCutPoint(r) => {
-                let addr = self.store(self.deref(self[r].clone()));
 
-                match addr {
+                        if self.b > nb {
-                    Addr::Con(Constant::Usize(nb)) => {
+                            self.b = nb;
-                        self.b = nb;
+                            self.tidy_trail();
-                        self.non_neck_cut();
+                        }
+
+                        self.p += 1;
                     },
                     _ => self.fail = true
                 };
@@ -2025,37 +2010,19 @@ impl MachineState {
         }
     }
 
-    fn neck_cut(&mut self)
-    {
-        let b = self.b;
-        let b0 = self.b0;
-
-        if b > b0 {
-            self.b = b0;
-            self.tidy_trail();
-        }
-
-        self.p += 1;                
-    }
-
-    fn non_neck_cut(&mut self)
-    {
-        let b = self.b;
-        let e = self.e;
-        let b0 = self.and_stack[e].b0; // STACK[E+2+1]
-
-        if b > b0 {
-            self.b = b0;
-            self.tidy_trail();
-        }
-
-        self.p += 1;        
-    }
-    
     fn execute_cut_instr(&mut self, instr: &CutInstruction) {
         match instr {
-            &CutInstruction::Cut =>
+            &CutInstruction::NeckCut => {
-                self.non_neck_cut(),                
+                let b = self.b;
+                let b0 = self.b0;
+
+                if b > b0 {
+                    self.b = b0;
+                    self.tidy_trail();
+                }
+
+                self.p += 1;                
+            },
             &CutInstruction::GetLevel => {
                 let b0 = self.b0;
                 let e  = self.e;
@@ -2063,8 +2030,18 @@ impl MachineState {
                 self.and_stack[e].b0 = b0;
                 self.p += 1;
             },
-            &CutInstruction::NeckCut =>
+            &CutInstruction::Cut => {
-                self.neck_cut()
+                let b = self.b;
+                let e = self.e;
+                let b0 = self.and_stack[e].b0; // STACK[E+2+1]
+
+                if b > b0 {
+                    self.b = b0;
+                    self.tidy_trail();
+                }
+
+                self.p += 1;   
+            }
         }
     }
 

src/prolog/macros.rs

@@ -309,15 +309,9 @@ macro_rules! unify_variable {
     )
 }
 
-macro_rules! set_neck_cut {
+macro_rules! set_cp {
     ($r:expr) => (
-        Line::BuiltIn(BuiltInInstruction::SetNeckCutPoint($r))
+        Line::BuiltIn(BuiltInInstruction::SetCutPoint($r))
-    )
-}
-
-macro_rules! set_non_neck_cut {
-    ($r:expr) => (
-        Line::BuiltIn(BuiltInInstruction::SetNonNeckCutPoint($r))
     )
 }