flatten bracketed commas in dcgs

src/prolog/compile.rs

@@ -193,13 +193,14 @@ impl ListingCompiler {
     {
         let mod_name = self.get_module_name();
 
-        if let Some(submodule) = wam_indices.take_module(submodule) {
+        if let Some(mut submodule) = wam_indices.take_module(submodule) {
             indices.use_module(code_repo, flags, &submodule)?;
 
             if let &mut Some(ref mut module) = &mut self.module {
                 module.remove_module(mod_name, &submodule);
                 module.use_module(code_repo, flags, &submodule)?;
             } else {
+                submodule.inserted_expansions = true;
                 wam_indices.remove_module(clause_name!("user"), &submodule);
             }
 
@@ -216,13 +217,14 @@ impl ListingCompiler {
     {
         let mod_name = self.get_module_name();
 
-        if let Some(submodule) = wam_indices.take_module(submodule) {
+        if let Some(mut submodule) = wam_indices.take_module(submodule) {
             indices.use_qualified_module(code_repo, flags, &submodule, exports)?;
 
             if let &mut Some(ref mut module) = &mut self.module {
                 module.remove_module(mod_name, &submodule);
                 module.use_qualified_module(code_repo, flags, &submodule, exports)?;
             } else {
+                submodule.inserted_expansions = true;
                 wam_indices.remove_module(clause_name!("user"), &submodule);
             }
 
@@ -346,7 +348,7 @@ impl ListingCompiler {
                 Ok(self.add_non_counted_bt_flag(name, arity)),
             Declaration::Op(op_decl) =>
                 op_decl.submit(self.get_module_name(), &mut indices.op_dir),
-            Declaration::UseModule(name) =>
+            Declaration::UseModule(name) =>                
                 self.use_module(name, code_repo, flags, wam_indices, indices),
             Declaration::UseQualifiedModule(name, exports) =>
                 self.use_qualified_module(name, code_repo, flags, &exports, wam_indices, indices),

src/prolog/instructions.rs

@@ -232,6 +232,7 @@ pub struct Module {
     pub op_dir: OpDir,
     pub term_expansions: (Predicate, VecDeque<TopLevel>),
     pub goal_expansions: (Predicate, VecDeque<TopLevel>),
+    pub inserted_expansions: bool // has the module been successfully inserted into toplevel??
 }
 
 #[derive(Copy, Clone, PartialEq)]
@@ -1103,7 +1104,8 @@ impl Module {
                  term_expansions: (Predicate::new(), VecDeque::from(vec![])),
                  goal_expansions: (Predicate::new(), VecDeque::from(vec![])),
                  code_dir: ModuleCodeDir::new(),
-                 op_dir: default_op_dir() }
+                 op_dir: default_op_dir(),
+                 inserted_expansions: false }
     }
 
     pub fn dump_expansions(&self, code_repo: &mut CodeRepo, flags: MachineFlags)

src/prolog/lib/dcgs.pl

@@ -45,15 +45,27 @@ expand_dcgs(Term0, N, (ModHead :- ModBody)) :-
     nonvar(Body),
     expand_body(Body, ModBody, N, N1).
 
-expand_body(Term0, (ModTerm, ModTerms), N0, N) :-
+expand_body(Term0, ModTerms, N0, N) :-
     nonvar(Term0), Term0 = (Term, Terms), !,
     nonvar(Term),
     expand_body_term(Term, ModTerm, N0, N1),
-    expand_body(Terms, ModTerms, N1, N).
+    unfurl_commas(ModTerm, ModTerms, ModTerms1),
+    expand_body(Terms, ModTerms1, N1, N).
 expand_body(Term0, ModTerm, N0, N) :-
     nonvar(Term0),
     expand_body_term(Term0, ModTerm, N0, N).
 
+/* unfurl_commas(?ModTerm, -ModTerms, -ModTerms1) :
+   sets  ModTerms = (ModTermI0, ModTermI1, ..., ModTermIN, ModTerms1) 
+   where ModTerm  = (ModTermI0, ModTermI1, ..., ModTermIN) */
+unfurl_commas(ModTerm, ModTerms, ModTerms1) :-
+    nonvar(ModTerm),
+    ModTerm  = (ModTermI0, ModTermIs),
+    !,
+    ModTerms = (ModTermI0, ModTerms2),    
+    unfurl_commas(ModTermIs, ModTerms2, ModTerms1).
+unfurl_commas(ModTermIN, (ModTermIN, ModTerms1), ModTerms1).
+
 expand_body_term([], true, N, N) :- !.
 expand_body_term([Arg|Args], ModTerm, N0, N) :-
     !, N is N0 + 1,

src/prolog/machine/mod.rs

@@ -299,7 +299,12 @@ impl SubModuleUser for IndexStore {
                   -> Result<(), SessionError>
     {
         use_module(self, submodule)?;
-        submodule.dump_expansions(code_repo, flags).map_err(SessionError::from)
+
+        if !submodule.inserted_expansions {
+            submodule.dump_expansions(code_repo, flags).map_err(SessionError::from)
+        } else {
+            Ok(())
+        }
     }
 }