add call_residue_vars/2

README.md

@@ -41,7 +41,7 @@ Extend rusty-wam to include the following, among other features:
   is straightforward with attributed variables (_in progress_).
      - [x] Support for `verify_attributes/3`
      - [x] Support for `attribute_goals/2` and `project_attributes/2`
-     - [ ] `call_residue/2` and `call_residue_vars/2`
+     - [x] `call_residue_vars/2`
 * `if_` and related predicates, following the developments of the
   paper "Indexing `dif/2`" (_in progress_).
 * All-solutions predicates (`findall/{3,4}`, `bagof/3`, `setof/3`).
@@ -140,6 +140,7 @@ The following predicates are built-in to rusty-wam.
 * `call/1..62`
 * `call_cleanup/2`
 * `call_with_inference_limit/3`
+* `call_residue_vars/2`
 * `can_be/2`
 * `catch/3`
 * `compare/3`

src/prolog/instructions.rs

@@ -242,9 +242,12 @@ pub enum SystemClauseType {
     DeleteHeadAttribute,
     DynamicModuleResolution,
     EnqueueAttributeGoal,
+    EnqueueAttributedVar,
     ExpandGoal,
     ExpandTerm,
     GetAttributedVariableList,
+    GetAttrVarQueueDelimiter,
+    GetAttrVarQueueBeyond,
     GetBValue,
     GetSCCCleaner,
     InstallSCCCleaner,
@@ -285,9 +288,12 @@ impl SystemClauseType {
             &SystemClauseType::DeleteHeadAttribute => clause_name!("$del_attr_head"),
             &SystemClauseType::DynamicModuleResolution => clause_name!("$module_call"),
             &SystemClauseType::EnqueueAttributeGoal => clause_name!("$enqueue_attribute_goal"),
+            &SystemClauseType::EnqueueAttributedVar => clause_name!("$enqueue_attr_var"),
             &SystemClauseType::ExpandTerm => clause_name!("$expand_term"),
             &SystemClauseType::ExpandGoal => clause_name!("$expand_goal"),
             &SystemClauseType::GetAttributedVariableList => clause_name!("$get_attr_list"),
+            &SystemClauseType::GetAttrVarQueueDelimiter => clause_name!("$get_attr_var_queue_delim"),
+            &SystemClauseType::GetAttrVarQueueBeyond => clause_name!("$get_attr_var_queue_beyond"),
             &SystemClauseType::GetBValue => clause_name!("$get_b_value"),
             &SystemClauseType::GetDoubleQuotes => clause_name!("$get_double_quotes"),
             &SystemClauseType::GetSCCCleaner => clause_name!("$get_scc_cleaner"),
@@ -328,6 +334,7 @@ impl SystemClauseType {
             ("$del_attr_head", 1) => Some(SystemClauseType::DeleteHeadAttribute),            
             ("$module_call", 2) => Some(SystemClauseType::DynamicModuleResolution),
             ("$enqueue_attribute_goal", 1) => Some(SystemClauseType::EnqueueAttributeGoal),
+            ("$enqueue_attr_var", 1) => Some(SystemClauseType::EnqueueAttributedVar),
             ("$expand_term", 2) => Some(SystemClauseType::ExpandTerm),
             ("$expand_goal", 2) => Some(SystemClauseType::ExpandGoal),
             ("$get_attr_list", 2) => Some(SystemClauseType::GetAttributedVariableList),
@@ -346,6 +353,8 @@ impl SystemClauseType {
             ("$clean_up_block", 1) => Some(SystemClauseType::CleanUpBlock),
             ("$erase_ball", 0) => Some(SystemClauseType::EraseBall),
             ("$fail", 0) => Some(SystemClauseType::Fail),
+            ("$get_attr_var_queue_beyond", 2) => Some(SystemClauseType::GetAttrVarQueueBeyond),
+            ("$get_attr_var_queue_delim", 1) => Some(SystemClauseType::GetAttrVarQueueDelimiter),
             ("$get_ball", 1) => Some(SystemClauseType::GetBall),
             ("$get_current_block", 1) => Some(SystemClauseType::GetCurrentBlock),
             ("$get_cp", 1) => Some(SystemClauseType::GetCutPoint),

src/prolog/lib/atts.pl

@@ -1,7 +1,8 @@
-:- module(atts, [attribute/1, '$absent_attr'/2, '$copy_attr_list'/2,
+:- module(atts, [attribute/1, call_residue_vars/2, '$absent_attr'/2,
-		 '$get_attr'/2, '$put_attr'/2, '$absent_from_list'/2,
+		 '$copy_attr_list'/2, '$get_attr'/2, '$put_attr'/2,
-		 '$get_from_list'/2, '$add_to_list'/2, '$del_attr'/3,
+		 '$absent_from_list'/2, '$get_from_list'/3,
-		 '$del_attr_step'/2, '$del_attr_buried'/3]).
+		 '$add_to_list'/3, '$del_attr'/3, '$del_attr_step'/3,
+		 '$del_attr_buried'/4]).
 
 :- use_module(library(control)).
 :- use_module(library(dcgs)).
@@ -19,21 +20,21 @@
     ( L \= Attr -> '$absent_from_list'(Ls, Attr) ).
 
 '$get_attr'(V, Attr) :-
-    '$get_attr_list'(V, Ls), nonvar(Ls), '$get_from_list'(Ls, Attr).
+    '$get_attr_list'(V, Ls), nonvar(Ls), '$get_from_list'(Ls, V, Attr).
 
-'$get_from_list'([L|Ls], Attr) :-
+'$get_from_list'([L|Ls], V, Attr) :-
     nonvar(L),
-    ( L \= Attr -> nonvar(Ls), '$get_from_list'(Ls, Attr)
+    ( L \= Attr -> nonvar(Ls), '$get_from_list'(Ls, V, Attr)
-    ; L = Attr
+    ; L = Attr, '$enqueue_attr_var'(V)
-    ; '$get_from_list'(Ls, Attr)
+    ; '$get_from_list'(Ls, V, Attr)
     ).
 
 '$put_attr'(V, Attr) :-
-    '$get_attr_list'(V, Ls), '$add_to_list'(Ls, Attr).
+    '$get_attr_list'(V, Ls), '$add_to_list'(Ls, V, Attr).
 
-'$add_to_list'(Ls, Attr) :-
+'$add_to_list'(Ls, V, Attr) :-
-    ( var(Ls) -> Ls = [Attr | _]
+    ( var(Ls) -> Ls = [Attr | _], '$enqueue_attr_var'(V)
-    ; Ls = [_ | Ls0] -> '$add_to_list'(Ls0, Attr)
+    ; Ls = [_ | Ls0] -> '$add_to_list'(Ls0, V, Attr)
     ).
 
 '$del_attr'(Ls0, _, _) :-
@@ -41,25 +42,26 @@
 '$del_attr'(Ls0, V, Attr) :-
     Ls0 = [Att | Ls1],
     nonvar(Att),
-    ( Att \= Attr -> '$del_attr_buried'(Ls0, Ls1, Attr)
+    ( Att \= Attr -> '$del_attr_buried'(Ls0, Ls1, V, Attr)
-    ; '$del_attr_head'(V), '$del_attr'(Ls1, V, Attr)
+    ; '$enqueue_attr_var'(V), '$del_attr_head'(V), '$del_attr'(Ls1, V, Attr)
     ).
 
-'$del_attr_step'(Ls1, Attr) :-
+'$del_attr_step'(Ls1, V, Attr) :-
-    ( nonvar(Ls1) -> Ls1 = [_ | Ls2], '$del_attr_buried'(Ls1, Ls2, Attr)
+    ( nonvar(Ls1) -> Ls1 = [_ | Ls2], '$del_attr_buried'(Ls1, Ls2, V, Attr)
     ; true ).
 
 %% assumptions: Ls0 is a list, Ls1 is its tail;
 %%              the head of Ls0 can be ignored.
-'$del_attr_buried'(Ls0, Ls1, Attr) :-
+'$del_attr_buried'(Ls0, Ls1, V, Attr) :-
     Ls0 = [_, Att | _],
     nonvar(Att),
     !,
-    ( Att \= Attr -> '$del_attr_step'(Ls1, Attr)
+    ( Att \= Attr -> '$del_attr_step'(Ls1, V, Attr)
-    ; '$del_attr_non_head'(Ls0), %% set tail of Ls0 = tail of Ls1. can be undone by backtracking.
+    ; '$enqueue_attr_var'(V),
-      '$del_attr_step'(Ls1, Attr)
+      '$del_attr_non_head'(Ls0), %% set tail of Ls0 = tail of Ls1. can be undone by backtracking.
+      '$del_attr_step'(Ls1, V, Attr)
     ).
-'$del_attr_buried'(_, _, _).
+'$del_attr_buried'(_, _, _, _).
 
 '$copy_attr_list'(L, []) :- var(L), !.
 '$copy_attr_list'([Att|Atts], [Att|CopiedAtts]) :-
@@ -123,3 +125,8 @@ user:goal_expansion(Term, M:put_atts(Var, Attr)) :-
 user:goal_expansion(Term, M:get_atts(Var, Attr)) :-
     nonvar(Term),
     Term = get_atts(Var, M, Attr).
+
+call_residue_vars(Goal, Vars) :-
+    '$get_attr_var_queue_delim'(B),
+    call(Goal),
+    '$get_attr_var_queue_beyond'(B, Vars).

src/prolog/lib/dif.pl

@@ -9,25 +9,27 @@ dif_set_variables([Var|Vars], X, Y) :-
     put_atts(Var, dif(X, Y)),
     dif_set_variables(Vars, X, Y).
 
-verify_dif_attrs([dif(X, Y) | Attrs], Var, [X \== Y | Goals]) :-
+verify_dif_attrs([dif(X, Y) | Attrs], Value, [X \== Y | Goals]) :-
-    (   get_atts(Var, +dif(X, Y)) -> true
+    (   get_atts(Value, +dif(X, Y)) -> true
-    ;   put_atts(Var, +dif(X, Y))
+    ;   put_atts(Value, +dif(X, Y))
     ),
-    verify_dif_attrs(Attrs, Var, Goals).
+    verify_dif_attrs(Attrs, Value, Goals).
-verify_dif_attrs([_ | Attrs], Var, Goals) :-
+verify_dif_attrs([_ | Attrs], Value, Goals) :-
-    verify_dif_attrs(Attrs, Var, Goals).
+    verify_dif_attrs(Attrs, Value, Goals).
 verify_dif_attrs([], _, []).
 
-verify_dif_attrs_no_var([dif(X, Y) | Attrs], [X \== Y | Goals]) :-
+verify_dif_attrs_no_var([dif(X, Y) | Attrs], Value, [X \== Y | Goals]) :-
-    verify_dif_attrs_no_var(Attrs, Goals).
+    term_variables(Value, ValueVars),
-verify_dif_attrs_no_var([_ | Attrs], Goals) :-
+    dif_set_variables(ValueVars, X, Y),
-    verify_dif_attrs_no_var(Attrs, Goals).
+    verify_dif_attrs_no_var(Attrs, Value, Goals).
-verify_dif_attrs_no_var([], []).
+verify_dif_attrs_no_var([_ | Attrs], Value, Goals) :-
+    verify_dif_attrs_no_var(Attrs, Value, Goals).
+verify_dif_attrs_no_var([], _, []).
 
 verify_attributes(Var, Value, Goals) :-
     (   get_atts(Var, Attrs) ->
 	(   var(Value) -> verify_dif_attrs(Attrs, Value, Goals)
-	;   verify_dif_attrs_no_var(Attrs, Goals)
+	;   verify_dif_attrs_no_var(Attrs, Value, Goals)
 	)
     ).
 

src/prolog/machine/attributed_variables.rs

@@ -11,6 +11,7 @@ pub(super) type Bindings = Vec<(usize, Addr)>;
 
 pub(super) struct AttrVarInitializer {
     pub(super) attribute_goals: Vec<Addr>,
+    pub(super) attr_var_queue: Vec<usize>,
     pub(super) bindings: Bindings,
     pub(super) cp: LocalCodePtr,
     pub(super) verify_attrs_loc: usize,
@@ -21,6 +22,7 @@ impl AttrVarInitializer {
     pub(super) fn new(verify_attrs_loc: usize, project_attrs_loc: usize) -> Self {
         AttrVarInitializer {
             attribute_goals: vec![],
+            attr_var_queue: vec![],
             bindings: vec![],
             cp: LocalCodePtr::default(),
             verify_attrs_loc,
@@ -30,6 +32,7 @@ impl AttrVarInitializer {
 
     #[inline]
     pub(super) fn reset(&mut self) {
+        self.attr_var_queue.clear();
         self.bindings.clear();
     }
 }

src/prolog/machine/machine_state.rs

@@ -341,6 +341,9 @@ pub(crate) trait CallPolicy: Any {
 
         machine_st.heap.truncate(machine_st.or_stack[b].h);
 
+        let attr_var_init_b = machine_st.or_stack[b].attr_var_init_b;
+        machine_st.attr_var_init.attr_var_queue.truncate(attr_var_init_b);
+
         machine_st.hb = machine_st.heap.h;
         machine_st.p += 1;
 
@@ -379,6 +382,9 @@ pub(crate) trait CallPolicy: Any {
 
         machine_st.heap.truncate(machine_st.or_stack[b].h);
 
+        let attr_var_init_b = machine_st.or_stack[b].attr_var_init_b;
+        machine_st.attr_var_init.attr_var_queue.truncate(attr_var_init_b);
+
         machine_st.hb = machine_st.heap.h;
         machine_st.p += offset;
 
@@ -414,8 +420,11 @@ pub(crate) trait CallPolicy: Any {
         machine_st.pstr_trail.truncate(machine_st.pstr_tr);
 
         machine_st.heap.truncate(machine_st.or_stack[b].h);
-        machine_st.b = machine_st.or_stack[b].b;
 
+        let attr_var_init_b = machine_st.or_stack[b].attr_var_init_b;
+        machine_st.attr_var_init.attr_var_queue.truncate(attr_var_init_b);
+
+        machine_st.b = machine_st.or_stack[b].b;
         machine_st.or_stack.truncate(machine_st.b);
 
         machine_st.hb = machine_st.heap.h;
@@ -454,8 +463,10 @@ pub(crate) trait CallPolicy: Any {
 
         machine_st.heap.truncate(machine_st.or_stack[b].h);
 
-        machine_st.b = machine_st.or_stack[b].b;
+        let attr_var_init_b = machine_st.or_stack[b].attr_var_init_b;
+        machine_st.attr_var_init.attr_var_queue.truncate(attr_var_init_b);
 
+        machine_st.b = machine_st.or_stack[b].b;
         machine_st.or_stack.truncate(machine_st.b);
 
         machine_st.hb = machine_st.heap.h;

src/prolog/machine/machine_state_impl.rs

@@ -2256,6 +2256,7 @@ impl MachineState {
                 self.or_stack.push(gi,
                                    self.e,
                                    self.cp.clone(),
+                                   self.attr_var_init.attr_var_queue.len(),
                                    self.b,
                                    self.p.clone() + 1,
                                    self.tr,
@@ -2292,6 +2293,7 @@ impl MachineState {
                 self.or_stack.push(gi,
                                    self.e,
                                    self.cp.clone(),
+                                   self.attr_var_init.attr_var_queue.len(),
                                    self.b,
                                    self.p.clone() + offset,
                                    self.tr,

src/prolog/machine/system_calls.rs

@@ -265,6 +265,15 @@ impl MachineState {
                 let addr = self[temp_v!(1)].clone();
                 self.attr_var_init.attribute_goals.push(addr);
             },
+            &SystemClauseType::EnqueueAttributedVar => {
+                let addr = self[temp_v!(1)].clone();
+
+                match self.store(self.deref(addr)) {
+                    Addr::AttrVar(h) =>
+                        self.attr_var_init.attr_var_queue.push(h),
+                    _ => {}
+                }
+            },
             &SystemClauseType::ExpandGoal => {
                 self.p = CodePtr::Local(LocalCodePtr::UserGoalExpansion(0));
                 return Ok(());
@@ -296,6 +305,35 @@ impl MachineState {
                 let list_addr = self[temp_v!(2)].clone();
                 self.unify(Addr::HeapCell(attr_var_list), list_addr);
             },
+            &SystemClauseType::GetAttrVarQueueDelimiter => {
+                let addr  = self[temp_v!(1)].clone();
+                let value = Addr::Con(Constant::Usize(self.attr_var_init.attr_var_queue.len()));
+
+                self.unify(addr, value);
+            },
+            &SystemClauseType::GetAttrVarQueueBeyond => {
+                let addr = self[temp_v!(1)].clone();
+
+                match self.store(self.deref(addr)) {
+                    Addr::Con(Constant::Usize(b)) => {
+                        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
+                                }).collect();
+
+                        attr_vars.sort_unstable_by(|a1, a2| self.compare_term_test(a1, a2));
+
+                        self.term_dedup(&mut attr_vars);
+                        let var_list_addr = Addr::HeapCell(self.heap.to_list(attr_vars.into_iter()));
+
+                        let list_addr = self[temp_v!(2)].clone();
+                        self.unify(var_list_addr, list_addr);
+                    },
+                    _ => self.fail = true
+                }
+            },
             &SystemClauseType::GetDoubleQuotes => {
                 let a1 = self[temp_v!(1)].clone();
 

src/prolog/or_stack.rs

@@ -7,6 +7,7 @@ pub struct Frame {
     pub global_index: usize,
     pub e: usize,
     pub cp: LocalCodePtr,
+    pub attr_var_init_b: usize,
     pub b: usize,    
     pub bp: CodePtr,
     pub tr: usize,
@@ -20,6 +21,7 @@ impl Frame {
     fn new(global_index: usize,
            e: usize,
            cp: LocalCodePtr,
+           attr_var_init_b: usize,
            b: usize,
            bp: CodePtr,
            tr: usize,
@@ -33,6 +35,7 @@ impl Frame {
             global_index,
             e,
             cp,
+            attr_var_init_b,
             b,
             bp,
             tr,
@@ -59,6 +62,7 @@ impl OrStack {
                 global_index: usize,
                 e: usize,
                 cp: LocalCodePtr,
+                attr_var_init_b: usize,
                 b: usize,
                 bp: CodePtr,
                 tr: usize,
@@ -67,7 +71,7 @@ impl OrStack {
                 b0: usize,
                 n: usize)
     {
-        self.0.push(Frame::new(global_index, e, cp, b, bp, tr, pstr_tr, h, b0, n));
+        self.0.push(Frame::new(global_index, e, cp, attr_var_init_b, b, bp, tr, pstr_tr, h, b0, n));
     }
 
     pub fn len(&self) -> usize {