binding attributed variables more eagerly after each implementation o…

…f verify_attributes/3 has been called (#248)

src/prolog/clause_types.rs

@@ -165,6 +165,7 @@ pub enum SystemClauseType {
     CallAttributeGoals,
     CharCode,
     CharsToNumber,
+    ClearAttrVarBindings,
     CloneAttributeGoals,
     CodesToNumber,
     CopyTermWithoutAttrVars,
@@ -214,7 +215,7 @@ pub enum SystemClauseType {
     REPL(REPLCodePtr),
     ReadQueryTerm,
     ReadTerm,
-    RedoAttrVarBindings,
+    RedoAttrVarBinding,
     RemoveCallPolicyCheck,
     RemoveInferenceCounter,
     ResetGlobalVarAtKey,
@@ -280,6 +281,7 @@ impl SystemClauseType {
 	    &SystemClauseType::REPL(REPLCodePtr::UseQualifiedModuleFromFile) => {
 		clause_name!("$use_qualified_module_from_file")
 	    }
+            &SystemClauseType::ClearAttrVarBindings => clause_name!("$clear_attr_var_bindings"),
             &SystemClauseType::CopyToLiftedHeap => clause_name!("$copy_to_lh"),
             &SystemClauseType::DeleteAttribute => clause_name!("$del_attr_non_head"),
             &SystemClauseType::DeleteHeadAttribute => clause_name!("$del_attr_head"),
@@ -340,7 +342,7 @@ impl SystemClauseType {
             &SystemClauseType::NumberToChars => clause_name!("$number_to_chars"),
             &SystemClauseType::NumberToCodes => clause_name!("$number_to_codes"),
             &SystemClauseType::RawInputReadChar => clause_name!("$raw_input_read_char"),
-            &SystemClauseType::RedoAttrVarBindings => clause_name!("$redo_attr_var_bindings"),
+            &SystemClauseType::RedoAttrVarBinding => clause_name!("$redo_attr_var_binding"),
             &SystemClauseType::RemoveCallPolicyCheck => clause_name!("$remove_call_policy_check"),
             &SystemClauseType::RemoveInferenceCounter => clause_name!("$remove_inference_counter"),
             &SystemClauseType::RestoreCutPolicy => clause_name!("$restore_cut_policy"),
@@ -395,6 +397,7 @@ impl SystemClauseType {
             ("$call_attribute_goals", 2) => Some(SystemClauseType::CallAttributeGoals),
             ("$char_code", 2) => Some(SystemClauseType::CharCode),
             ("$chars_to_number", 2) => Some(SystemClauseType::CharsToNumber),
+            ("$clear_attr_var_bindings", 0) => Some(SystemClauseType::ClearAttrVarBindings),
             ("$clone_attribute_goals", 1) => Some(SystemClauseType::CloneAttributeGoals),
             ("$codes_to_number", 2) => Some(SystemClauseType::CodesToNumber),
             ("$copy_term_without_attr_vars", 2) => Some(SystemClauseType::CopyTermWithoutAttrVars),
@@ -444,7 +447,7 @@ impl SystemClauseType {
             ("$number_to_chars", 2) => Some(SystemClauseType::NumberToChars),
             ("$number_to_codes", 2) => Some(SystemClauseType::NumberToCodes),
             ("$op", 3) => Some(SystemClauseType::OpDeclaration),
-            ("$redo_attr_var_bindings", 0) => Some(SystemClauseType::RedoAttrVarBindings),
+            ("$redo_attr_var_binding", 2) => Some(SystemClauseType::RedoAttrVarBinding),
             ("$remove_call_policy_check", 1) => Some(SystemClauseType::RemoveCallPolicyCheck),
             ("$remove_inference_counter", 2) => Some(SystemClauseType::RemoveInferenceCounter),
             ("$restore_cut_policy", 0) => Some(SystemClauseType::RestoreCutPolicy),

src/prolog/lib/atts.pl

@@ -46,7 +46,8 @@
     '$get_attr_list'(V, Ls), '$add_to_list'(Ls, V, Attr).
 
 '$add_to_list'(Ls, V, Attr) :-
-    ( var(Ls) -> Ls = [Attr | _], '$enqueue_attr_var'(V)
+    ( var(Ls) ->
+      Ls = [Attr | _], '$enqueue_attr_var'(V)
     ; Ls = [_ | Ls0], '$add_to_list'(Ls0, V, Attr)
     ).
 
@@ -56,7 +57,8 @@
     Ls0 = [Att | Ls1],
     nonvar(Att),
     ( Att \= Attr -> '$del_attr_buried'(Ls0, Ls1, V, Attr)
-    ; '$enqueue_attr_var'(V), '$del_attr_head'(V), '$del_attr'(Ls1, V, Attr)
+    ; '$enqueue_attr_var'(V),
+      '$del_attr_head'(V), '$del_attr'(Ls1, V, Attr)
     ).
 
 '$del_attr_step'(Ls1, V, Attr) :-
@@ -122,13 +124,18 @@
     { functor(Attr, Name, Arity),
       numbervars(Attr, 0, Arity),
       V = '$VAR'(Arity) },
-    [(put_atts(V, +Attr) :- !, functor(Attr, Head, Arity), functor(AttrForm, Head, Arity),
-			    '$get_attr_list'(V, Ls), '$del_attr'(Ls, V, AttrForm),
+    [(put_atts(V, +Attr) :- !, functor(Attr, Head, Arity),
+			    functor(AttrForm, Head, Arity),
+			    '$get_attr_list'(V, Ls),
+			    '$del_attr'(Ls, V, AttrForm),
 			    '$put_attr'(V, Attr)),
-     (put_atts(V,  Attr) :- !, functor(Attr, Head, Arity), functor(AttrForm, Head, Arity),
-			    '$get_attr_list'(V, Ls), '$del_attr'(Ls, V, AttrForm), 
+     (put_atts(V,  Attr) :- !, functor(Attr, Head, Arity),
+			    functor(AttrForm, Head, Arity),
+			    '$get_attr_list'(V, Ls), 
+			    '$del_attr'(Ls, V, AttrForm), 
 			    '$put_attr'(V, Attr)),
-     (put_atts(V, -Attr) :- !, functor(Attr, _, _), '$get_attr_list'(V, Ls), 
+     (put_atts(V, -Attr) :- !, functor(Attr, _, _),
+			    '$get_attr_list'(V, Ls), 
 			    '$del_attr'(Ls, V, Attr))].
 
 get_attr(Name, Arity) -->

src/prolog/machine/attributed_variables.pl

@@ -1,13 +1,14 @@
 driver(Vars, Values) :-
     iterate(Vars, Values, ListOfListsOfGoalLists),
-    '$redo_attr_var_bindings', % the bindings list is emptied here.
+    '$clear_attr_var_bindings',
     !,
     call_goals(ListOfListsOfGoalLists),
     '$return_from_verify_attr'.
 
 iterate([Var|VarBindings], [Value|ValueBindings], [ListOfGoalLists | ListsCubed]) :-
     '$get_attr_list'(Var, Ls),
     call_verify_attributes(Ls, Var, Value, ListOfGoalLists),
+    '$redo_attr_var_binding'(Var, Value),
     iterate(VarBindings, ValueBindings, ListsCubed).
 iterate([], [], []).
 

src/prolog/machine/compile.rs

@@ -649,7 +649,8 @@ impl ListingCompiler {
             let idx = code_dir
                 .entry((name.clone(), arity))
                 .or_insert(CodeIndex::default());
-            set_code_index!(idx, IndexPtr::Index(p), self.get_module_name());
+
+            set_code_index!(idx, IndexPtr::Index(p), self.get_module_name());            
 
             self.localize_self_calls(name, arity, &mut decl_code, p);
             code.extend(decl_code.into_iter());

src/prolog/machine/system_calls.rs

@@ -1644,11 +1644,32 @@ impl MachineState {
                     }
                 };
             }
-            &SystemClauseType::RedoAttrVarBindings => {
-                let bindings = mem::replace(&mut self.attr_var_init.bindings, vec![]);
+            &SystemClauseType::ClearAttrVarBindings => {
+                self.attr_var_init.bindings.clear();
+            }
+            &SystemClauseType::RedoAttrVarBinding => {
+                let var = self.store(self.deref(self[temp_v!(1)].clone()));
+                let value = self.store(self.deref(self[temp_v!(2)].clone()));
+
+                match var {
+                    Addr::AttrVar(h) => {
+                        if let Addr::AttrVar(h1) = value {
+                            self.heap[h] = HeapCellValue::Addr(Addr::AttrVar(h1));
 
-                for (h, addr) in bindings {
-                    self.heap[h] = HeapCellValue::Addr(addr);
+                            // append h's attributes list to h1's.
+                            let mut l = h1 + 1;
+
+                            while let Addr::Lis(l1) = self.store(self.deref(self.heap[l].as_addr(l))) {
+                                l = l1 + 1;
+                            }
+
+                            self.heap[l] = HeapCellValue::Addr(Addr::HeapCell(h + 1));
+                            self.trail(TrailRef::Ref(Ref::HeapCell(l)));
+                        } else {
+                            self.heap[h] = HeapCellValue::Addr(value);
+                        }
+                    }
+                    _ => unreachable!()
                 }
             }
             &SystemClauseType::ResetGlobalVarAtKey => {