From 0b83a7f154dd462300bec448089541d0b1b6521a Mon Sep 17 00:00:00 2001
From: Salvador Abreu <spa@debian.org>
Date: Thu, 2 Jul 2015 17:26:48 +0900
Subject: [PATCH] First stab at semantic analysis (names & types). New Prolog files for semantic analysis (semantic.pl), symbol table (stable.pl) and known types (types.pl). Lots of changes in grammar. fznslurp is now fzsem; new "name" action.

---
 fzn-parser/Makefile              | 11 ++++++++---
 fzn-parser/TODO                  |  3 +++
 fzn-parser/examples/aust.ast     | 76 ++++++++++++++++++++++++++++++++++++++++++++--------------------------------
 fzn-parser/examples/aust.ast.old | 23 +++++++++++++++++++++++
 fzn-parser/flatzinc.y            | 68 ++++++++++++++++++++++++++++++++++++++++++++------------------------
 fzn-parser/fznslurp.pl           | 11 ++++++++---
 fzn-parser/semantic.pl           | 32 ++++++++++++++++++++++++++++++++
 fzn-parser/stable.pl             | 10 ++++++++++
 fzn-parser/types.pl              |  6 ++++++
 9 files changed, 178 insertions(+), 62 deletions(-)
 create mode 100644 fzn-parser/TODO
 create mode 100644 fzn-parser/semantic.pl
 create mode 100644 fzn-parser/stable.pl
 create mode 100644 fzn-parser/types.pl

diff --git a/fzn-parser/Makefile b/fzn-parser/Makefile
index 7488d16..5a69d99 100644
--- a/fzn-parser/Makefile
+++ b/fzn-parser/Makefile
@@ -3,6 +3,8 @@ OBJ = 		flatzinc.tab.o
 GENCFILES = 	flatzinc.tab.c lex.yy.c 
 OTHER = 	flatzinc.output 
 
+PLFILES =       $(wildcard *.pl)
+
 # NOTE: we need to pass the `-l' flag to ensure the scanner internal
 # variable `yylineno' is available.
 #
@@ -20,13 +22,16 @@ GPLC =		gplc
 
 RM =		/bin/rm -f
 
-all: fzp fznslurp
+%.ast:: %.fzn
+	fzp < $< > $@
+
+all: fzp fzsem
 
 fzp:	$(OBJ)
 	$(CC) $(CFLAGS) -o $@ $(OBJ) $(LEXLIB)
 
-fznslurp: fznslurp.pl
-	$(GPLC) -o $@ $<
+fzsem: $(PLFILES)
+	$(GPLC) -o $@ $(PLFILES)
 
 flatzinc.tab.c:	flatzinc.y lex.yy.c
 		$(YACC) $(YACCFLAGS) flatzinc.y
diff --git a/fzn-parser/TODO b/fzn-parser/TODO
new file mode 100644
index 0000000..059b254
--- /dev/null
+++ b/fzn-parser/TODO
@@ -0,0 +1,3 @@
+- define AST syntax
+- define type system
+- 
\ No newline at end of file
diff --git a/fzn-parser/examples/aust.ast b/fzn-parser/examples/aust.ast
index bcea9bc..6f8f443 100644
--- a/fzn-parser/examples/aust.ast
+++ b/fzn-parser/examples/aust.ast
@@ -3,69 +3,69 @@ _T > [[]|_T].
 [X|_T] > [preds(X)|_T].
 _T > [[]|_T].
 _T > [int|_T].
-_T > [id('X_INTRODUCED_0')|_T].
+_T > ['X_INTRODUCED_0'|_T].
 _T > [[]|_T].
 _T > [int:lit(1)|_T].
 _T > [int:lit(-1)|_T].
 [T2:E2,T1:E1|_T] > [(T1,T2):(E1,E2)|_T].
 [Es|_T] > [array(_):alit(Es)|_T].
-[VAL,AN,T|_T] > [var(array(T,1,2), VAL, AN)|_T].
+[VAL,AN,ID,T|_T] > [var(ID, array(T,1,2), VAL, AN)|_T].
 [H,T|_T] > [[H|T]|_T].
 _T > [int(1,3)|_T].
-_T > [id('wa')|_T].
+_T > ['wa'|_T].
 _T > [_:id('output_var')|_T].
 _T > [[]|_T].
-[H,T|_T] > [[H|T]|_T].
+[As, E|_T] > [[E|As]|_T].
 _T > [[]|_T].
-[VAL,AN,T|_T] > [var(T, VAL, AN)|_T].
+[VAL,AN,ID,T|_T] > [var(ID, T, VAL, AN)|_T].
 [H,T|_T] > [[H|T]|_T].
 _T > [int(1,3)|_T].
-_T > [id('nt')|_T].
+_T > ['nt'|_T].
 _T > [_:id('output_var')|_T].
 _T > [[]|_T].
-[H,T|_T] > [[H|T]|_T].
+[As, E|_T] > [[E|As]|_T].
 _T > [[]|_T].
-[VAL,AN,T|_T] > [var(T, VAL, AN)|_T].
+[VAL,AN,ID,T|_T] > [var(ID, T, VAL, AN)|_T].
 [H,T|_T] > [[H|T]|_T].
 _T > [int(1,3)|_T].
-_T > [id('sa')|_T].
+_T > ['sa'|_T].
 _T > [_:id('output_var')|_T].
 _T > [[]|_T].
-[H,T|_T] > [[H|T]|_T].
+[As, E|_T] > [[E|As]|_T].
 _T > [[]|_T].
-[VAL,AN,T|_T] > [var(T, VAL, AN)|_T].
+[VAL,AN,ID,T|_T] > [var(ID, T, VAL, AN)|_T].
 [H,T|_T] > [[H|T]|_T].
 _T > [int(1,3)|_T].
-_T > [id('q')|_T].
+_T > ['q'|_T].
 _T > [_:id('output_var')|_T].
 _T > [[]|_T].
-[H,T|_T] > [[H|T]|_T].
+[As, E|_T] > [[E|As]|_T].
 _T > [[]|_T].
-[VAL,AN,T|_T] > [var(T, VAL, AN)|_T].
+[VAL,AN,ID,T|_T] > [var(ID, T, VAL, AN)|_T].
 [H,T|_T] > [[H|T]|_T].
 _T > [int(1,3)|_T].
-_T > [id('nsw')|_T].
+_T > ['nsw'|_T].
 _T > [_:id('output_var')|_T].
 _T > [[]|_T].
-[H,T|_T] > [[H|T]|_T].
+[As, E|_T] > [[E|As]|_T].
 _T > [[]|_T].
-[VAL,AN,T|_T] > [var(T, VAL, AN)|_T].
+[VAL,AN,ID,T|_T] > [var(ID, T, VAL, AN)|_T].
 [H,T|_T] > [[H|T]|_T].
 _T > [int(1,3)|_T].
-_T > [id('v')|_T].
+_T > ['v'|_T].
 _T > [_:id('output_var')|_T].
 _T > [[]|_T].
-[H,T|_T] > [[H|T]|_T].
+[As, E|_T] > [[E|As]|_T].
 _T > [[]|_T].
-[VAL,AN,T|_T] > [var(T, VAL, AN)|_T].
+[VAL,AN,ID,T|_T] > [var(ID, T, VAL, AN)|_T].
 [H,T|_T] > [[H|T]|_T].
 _T > [int(1,3)|_T].
-_T > [id('t')|_T].
+_T > ['t'|_T].
 _T > [_:id('output_var')|_T].
 _T > [[]|_T].
-[H,T|_T] > [[H|T]|_T].
+[As, E|_T] > [[E|As]|_T].
 _T > [[]|_T].
-[VAL,AN,T|_T] > [var(T, VAL, AN)|_T].
+[VAL,AN,ID,T|_T] > [var(ID, T, VAL, AN)|_T].
 [H,T|_T] > [[H|T]|_T].
 [X|_T] > [vars(X)|_T].
 _T > [[]|_T].
@@ -77,8 +77,9 @@ _T > [_:id('nt')|_T].
 _T > [int:lit(0)|_T].
 [T2:E2,T1:E1|_T] > [(T1,T2):(E1,E2)|_T].
 [T2:E2,T1:E1|_T] > [(T1,T2):(E1,E2)|_T].
+[AL|_T] > [C|_T] :- C =.. ['int_lin_ne'|AL].
 _T > [[]|_T].
-[A, C|_T] > [constraint(C, A)|_T].
+[A,C,E|_T] > [constraint(C,E,A)|_T].
 [H,T|_T] > [[H|T]|_T].
 _T > [_:id('X_INTRODUCED_0')|_T].
 _T > [_:id('wa')|_T].
@@ -88,8 +89,9 @@ _T > [_:id('sa')|_T].
 _T > [int:lit(0)|_T].
 [T2:E2,T1:E1|_T] > [(T1,T2):(E1,E2)|_T].
 [T2:E2,T1:E1|_T] > [(T1,T2):(E1,E2)|_T].
+[AL|_T] > [C|_T] :- C =.. ['int_lin_ne'|AL].
 _T > [[]|_T].
-[A, C|_T] > [constraint(C, A)|_T].
+[A,C,E|_T] > [constraint(C,E,A)|_T].
 [H,T|_T] > [[H|T]|_T].
 _T > [_:id('X_INTRODUCED_0')|_T].
 _T > [_:id('nt')|_T].
@@ -99,8 +101,9 @@ _T > [_:id('sa')|_T].
 _T > [int:lit(0)|_T].
 [T2:E2,T1:E1|_T] > [(T1,T2):(E1,E2)|_T].
 [T2:E2,T1:E1|_T] > [(T1,T2):(E1,E2)|_T].
+[AL|_T] > [C|_T] :- C =.. ['int_lin_ne'|AL].
 _T > [[]|_T].
-[A, C|_T] > [constraint(C, A)|_T].
+[A,C,E|_T] > [constraint(C,E,A)|_T].
 [H,T|_T] > [[H|T]|_T].
 _T > [_:id('X_INTRODUCED_0')|_T].
 _T > [_:id('nt')|_T].
@@ -110,8 +113,9 @@ _T > [_:id('q')|_T].
 _T > [int:lit(0)|_T].
 [T2:E2,T1:E1|_T] > [(T1,T2):(E1,E2)|_T].
 [T2:E2,T1:E1|_T] > [(T1,T2):(E1,E2)|_T].
+[AL|_T] > [C|_T] :- C =.. ['int_lin_ne'|AL].
 _T > [[]|_T].
-[A, C|_T] > [constraint(C, A)|_T].
+[A,C,E|_T] > [constraint(C,E,A)|_T].
 [H,T|_T] > [[H|T]|_T].
 _T > [_:id('X_INTRODUCED_0')|_T].
 _T > [_:id('sa')|_T].
@@ -121,8 +125,9 @@ _T > [_:id('q')|_T].
 _T > [int:lit(0)|_T].
 [T2:E2,T1:E1|_T] > [(T1,T2):(E1,E2)|_T].
 [T2:E2,T1:E1|_T] > [(T1,T2):(E1,E2)|_T].
+[AL|_T] > [C|_T] :- C =.. ['int_lin_ne'|AL].
 _T > [[]|_T].
-[A, C|_T] > [constraint(C, A)|_T].
+[A,C,E|_T] > [constraint(C,E,A)|_T].
 [H,T|_T] > [[H|T]|_T].
 _T > [_:id('X_INTRODUCED_0')|_T].
 _T > [_:id('sa')|_T].
@@ -132,8 +137,9 @@ _T > [_:id('nsw')|_T].
 _T > [int:lit(0)|_T].
 [T2:E2,T1:E1|_T] > [(T1,T2):(E1,E2)|_T].
 [T2:E2,T1:E1|_T] > [(T1,T2):(E1,E2)|_T].
+[AL|_T] > [C|_T] :- C =.. ['int_lin_ne'|AL].
 _T > [[]|_T].
-[A, C|_T] > [constraint(C, A)|_T].
+[A,C,E|_T] > [constraint(C,E,A)|_T].
 [H,T|_T] > [[H|T]|_T].
 _T > [_:id('X_INTRODUCED_0')|_T].
 _T > [_:id('sa')|_T].
@@ -143,8 +149,9 @@ _T > [_:id('v')|_T].
 _T > [int:lit(0)|_T].
 [T2:E2,T1:E1|_T] > [(T1,T2):(E1,E2)|_T].
 [T2:E2,T1:E1|_T] > [(T1,T2):(E1,E2)|_T].
+[AL|_T] > [C|_T] :- C =.. ['int_lin_ne'|AL].
 _T > [[]|_T].
-[A, C|_T] > [constraint(C, A)|_T].
+[A,C,E|_T] > [constraint(C,E,A)|_T].
 [H,T|_T] > [[H|T]|_T].
 _T > [_:id('X_INTRODUCED_0')|_T].
 _T > [_:id('q')|_T].
@@ -154,8 +161,9 @@ _T > [_:id('nsw')|_T].
 _T > [int:lit(0)|_T].
 [T2:E2,T1:E1|_T] > [(T1,T2):(E1,E2)|_T].
 [T2:E2,T1:E1|_T] > [(T1,T2):(E1,E2)|_T].
+[AL|_T] > [C|_T] :- C =.. ['int_lin_ne'|AL].
 _T > [[]|_T].
-[A, C|_T] > [constraint(C, A)|_T].
+[A,C,E|_T] > [constraint(C,E,A)|_T].
 [H,T|_T] > [[H|T]|_T].
 _T > [_:id('X_INTRODUCED_0')|_T].
 _T > [_:id('nsw')|_T].
@@ -165,8 +173,12 @@ _T > [_:id('v')|_T].
 _T > [int:lit(0)|_T].
 [T2:E2,T1:E1|_T] > [(T1,T2):(E1,E2)|_T].
 [T2:E2,T1:E1|_T] > [(T1,T2):(E1,E2)|_T].
+[AL|_T] > [C|_T] :- C =.. ['int_lin_ne'|AL].
 _T > [[]|_T].
-[A, C|_T] > [constraint(C, A)|_T].
+[A,C,E|_T] > [constraint(C,E,A)|_T].
 [H,T|_T] > [[H|T]|_T].
 [X|_T] > [constrs(X)|_T].
 _T > [[]|_T].
+_T > [satisfy|_T].
+[S,A|_T] > [solve(S, A)|_T].
+[S,C,V,P|_T] > [fzn(P, V, C, S)|_T].
diff --git a/fzn-parser/examples/aust.ast.old b/fzn-parser/examples/aust.ast.old
index eb5aeb1..bcea9bc 100644
--- a/fzn-parser/examples/aust.ast.old
+++ b/fzn-parser/examples/aust.ast.old
@@ -3,46 +3,69 @@ _T > [[]|_T].
 [X|_T] > [preds(X)|_T].
 _T > [[]|_T].
 _T > [int|_T].
+_T > [id('X_INTRODUCED_0')|_T].
 _T > [[]|_T].
 _T > [int:lit(1)|_T].
 _T > [int:lit(-1)|_T].
 [T2:E2,T1:E1|_T] > [(T1,T2):(E1,E2)|_T].
 [Es|_T] > [array(_):alit(Es)|_T].
+[VAL,AN,T|_T] > [var(array(T,1,2), VAL, AN)|_T].
 [H,T|_T] > [[H|T]|_T].
 _T > [int(1,3)|_T].
+_T > [id('wa')|_T].
 _T > [_:id('output_var')|_T].
 _T > [[]|_T].
 [H,T|_T] > [[H|T]|_T].
+_T > [[]|_T].
+[VAL,AN,T|_T] > [var(T, VAL, AN)|_T].
 [H,T|_T] > [[H|T]|_T].
 _T > [int(1,3)|_T].
+_T > [id('nt')|_T].
 _T > [_:id('output_var')|_T].
 _T > [[]|_T].
 [H,T|_T] > [[H|T]|_T].
+_T > [[]|_T].
+[VAL,AN,T|_T] > [var(T, VAL, AN)|_T].
 [H,T|_T] > [[H|T]|_T].
 _T > [int(1,3)|_T].
+_T > [id('sa')|_T].
 _T > [_:id('output_var')|_T].
 _T > [[]|_T].
 [H,T|_T] > [[H|T]|_T].
+_T > [[]|_T].
+[VAL,AN,T|_T] > [var(T, VAL, AN)|_T].
 [H,T|_T] > [[H|T]|_T].
 _T > [int(1,3)|_T].
+_T > [id('q')|_T].
 _T > [_:id('output_var')|_T].
 _T > [[]|_T].
 [H,T|_T] > [[H|T]|_T].
+_T > [[]|_T].
+[VAL,AN,T|_T] > [var(T, VAL, AN)|_T].
 [H,T|_T] > [[H|T]|_T].
 _T > [int(1,3)|_T].
+_T > [id('nsw')|_T].
 _T > [_:id('output_var')|_T].
 _T > [[]|_T].
 [H,T|_T] > [[H|T]|_T].
+_T > [[]|_T].
+[VAL,AN,T|_T] > [var(T, VAL, AN)|_T].
 [H,T|_T] > [[H|T]|_T].
 _T > [int(1,3)|_T].
+_T > [id('v')|_T].
 _T > [_:id('output_var')|_T].
 _T > [[]|_T].
 [H,T|_T] > [[H|T]|_T].
+_T > [[]|_T].
+[VAL,AN,T|_T] > [var(T, VAL, AN)|_T].
 [H,T|_T] > [[H|T]|_T].
 _T > [int(1,3)|_T].
+_T > [id('t')|_T].
 _T > [_:id('output_var')|_T].
 _T > [[]|_T].
 [H,T|_T] > [[H|T]|_T].
+_T > [[]|_T].
+[VAL,AN,T|_T] > [var(T, VAL, AN)|_T].
 [H,T|_T] > [[H|T]|_T].
 [X|_T] > [vars(X)|_T].
 _T > [[]|_T].
diff --git a/fzn-parser/flatzinc.y b/fzn-parser/flatzinc.y
index 842f3f4..512faf6 100644
--- a/fzn-parser/flatzinc.y
+++ b/fzn-parser/flatzinc.y
@@ -19,6 +19,14 @@
 
 #include "types.h"
 
+// -- AST stack macros: -------------------------------------------------------
+// AST  (POP, (PUSH))
+// ASTT (POP, (PUSH), TRANS)
+// INIT (STACK)
+// PUSH (ITEM)
+// CONS ()
+// NIL  ()
+
 #define AST(pop, push)				\
 {						\
     printf ("[%s|_T] > [", pop);		\
@@ -26,6 +34,15 @@
     printf ("|_T].\n");				\
 }
 
+#define ASTT(pop, push, trans)			\
+{						\
+    printf ("[%s|_T] > [", pop);		\
+    printf push;				\
+    printf ("|_T] :- ");			\
+    printf trans;				\
+    printf (".\n");				\
+}
+
 #define INIT(x)					\
 {						\
   printf ("_ > %s.\n", x);			\
@@ -51,6 +68,9 @@
   // pop an item and a list, push new list (CONS)
 #define CONS()  AST ("H,T", ("[H|T]"))
 
+  // pop a list and an item, push new list (RCONS)
+#define RCONS() AST ("T,H", ("[H|T]"))
+
   // push the empty list
 #define NIL()   PUSH (("[]"))
 
@@ -67,7 +87,9 @@
        <id>         IDENT UNDERSCORE_IDENT
        ARRAY BOOL CONSTRAINT FALSE FLOAT INT MAXIMIZE MINIMIZE OF
        PREDICATE SATISFY SET SOLVE TRUE VAR DOTDOT COLONCOLON 
-       
+
+%right ','
+
 %%
 
 //---------------------------------------------------------------------------
@@ -132,10 +154,10 @@ ident_anns:			/* -> [ ANNOT,ID | _ ] */
 
 constraint_item:		/* -> [ constraint(...) | ] */
     CONSTRAINT constraint_elem annotations
-                             { AST ("A,C,E", ("constraint(C,E,A)")); }
+                             { AST ("A,C", ("constraint(C,A)")); }
 
 constraint_elem:		/* -> [ CONSTR_ID, EXPRLIST | _ ] */
-    IDENT '(' exprs ')'      { PUSH (("'%s'", $1)); }
+    IDENT '(' exprs ')'      { ASTT ("AL", ("C"), ("C =.. ['%s'|AL]", $1)); }
 
 solve_item:			/* -> [ solve(S,A) | _ ] */
     SOLVE annotations solve_kind { AST ("S,A", ("solve(S, A)")); }
@@ -191,7 +213,7 @@ int_ti_expr_tail:
   | '{' int_literals '}'                { AST ("Ls", ("int(Ls)")); }
 
 int_literals:
-    INT_LITERAL ',' int_literals        { AST ("Ls, L", ("[L|Ls]")); }
+    INT_LITERAL ',' int_literals        { AST ("Ls", ("[%d|Ls]", $1)); }
   | INT_LITERAL                         { PUSH (("[%d]", $1)); }
 
 float_ti_expr_tail:
@@ -206,46 +228,44 @@ set_ti_expr_tail:
 //---------------------------------------------------------------------------
 
 exprs:
-    expr ',' exprs               { AST ("T2:E2,T1:E1", ("(T1,T2):(E1,E2)")); }
-  | expr
+    exprs ',' exprs              { CONS (); }
+  | expr			 { AST ("E", ("[E]")); }
 
 expr:
     bool_literal
-  | INT_LITERAL                  { PUSH (("int:lit(%d)", $1.ival)); }
-  | FLOAT_LITERAL                { PUSH (("float:lit(%g)", $1.rval)); }
-  | STRING_LITERAL               { PUSH (("string:lit(\"%s\")", $1.sval)); }
+  | INT_LITERAL                  { PUSH (("lit(%d,int)", $1.ival)); }
+  | FLOAT_LITERAL                { PUSH (("lit(%g,float)", $1.rval)); }
+  | STRING_LITERAL               { PUSH (("lit(\"%s\",string)", $1.sval)); }
   | set_literal
   | array_literal
   | array_access_expr
-  | IDENT                        { PUSH (("_:id('%s')", $1)); }
-  | UNDERSCORE_IDENT             { PUSH (("_:uid('%s')", $1)); }
+  | IDENT                        { PUSH (("id('%s')", $1)); }
+  | UNDERSCORE_IDENT             { PUSH (("id('%s')", $1)); }
   | IDENT '(' exprs ')'	/* An annotation value with > 0 arguments. */
 
 bool_literal:
-   FALSE                         { PUSH (("bool:lit(false)")); }
- | TRUE                          { PUSH (("bool:lit(true)")); }
+   FALSE                         { PUSH (("lit(false,bool)")); }
+ | TRUE                          { PUSH (("lit(true,bool)")); }
 
 set_literal:
-    '{' exprs '}'                { AST ("Ts:Es", ("set(Ts):lit(Es)")); }
-  | '{' '}'                      { PUSH (("set(_):lit([])")); }
+    '{' exprs '}'                { AST ("Es", ("lit(Es,set(_))")); }
+  | '{' '}'                      { PUSH (("lit([],set(_))")); }
   | INT_LITERAL DOTDOT INT_LITERAL { int i;
 				     PRE();
-				     printf ("set(int):lit(");
+				     printf ("lit([");
 				     for (i=$1.ival; i<$3.ival; ++i)
 				       printf ("%d, ", i);
-				     printf ("%d)", $3.ival);
+				     printf ("%d], set(int))", $3.ival);
 				     POST(); }
 
 array_literal:
-    '[' exprs ']'                { AST ("Es", ("array(_):alit(Es)")); }
-  | '[' ']'                      { PUSH (("array(_):alit([])")); }
+    '[' exprs ']'                { AST ("Es", ("lit(Es,array(_))")); }
+  | '[' ']'                      { PUSH (("lit([],array(_))")); }
 
-array_access_expr: IDENT '[' INT_LITERAL ']'
-                                 { AST ("int:EI,array(T):ID",
-					("T:aref(array(T):ID,int:EI)")); }
+array_access_expr:
+    IDENT '[' INT_LITERAL ']'    { PUSH (("aref('%s',lit(%d,int),_)",$1,$3)); }
   | UNDERSCORE_IDENT '[' INT_LITERAL ']'
-                                 { AST ("int:EI,array(T):ID",
-					("T:aref(array(T):ID,int:EI)")); }
+                                 { PUSH (("aref('%s',lit(%d,int),_)",$1,$3)); }
 
 //---------------------------------------------------------------------------
 // Annotations
diff --git a/fzn-parser/fznslurp.pl b/fzn-parser/fznslurp.pl
index bfaffe4..62d9d0a 100644
--- a/fzn-parser/fznslurp.pl
+++ b/fzn-parser/fznslurp.pl
@@ -11,9 +11,13 @@ main([]).
 
 action(load)   :- !, load_ast(AST), g_assign(ast, AST).
 action(dump)   :- !, g_read(ast, AST), dump_ast(AST).
+action(name)   :- !, 
+		  g_read(ast, AST), 
+		  sa_names(AST, NAST),
+		  g_assign(ast, NAST).
 action(halt)   :- !, halt.
-action(debug)  :- g_read(ast_debug, true), !, g_write(ast_debug, false).
-action(debug)  :- !, g_write(ast_debug, true).
+action(debug)  :- g_read(ast_debug, true), !, g_assign(ast_debug, false).
+action(debug)  :- !, g_assign(ast_debug, true).
 action(ACTION) :- format("%w: unknown action.\n", [ACTION]).
 
 
@@ -35,7 +39,8 @@ load_ast((IN > INT), IN, OUT) :-
 
 load_ast_deb(end_of_file, AST, AST).
 load_ast_deb(IN > INT,    IN,  OUT) :- read(OP), !,
-				       write(OP), nl,
+				       writeq(IN), write('.'), nl,
+				       writeq(OP), nl,
 				       load_ast_deb(OP, INT, OUT).
 
 % -----------------------------------------------------------------------------
diff --git a/fzn-parser/semantic.pl b/fzn-parser/semantic.pl
new file mode 100644
index 0000000..278f5e8
--- /dev/null
+++ b/fzn-parser/semantic.pl
@@ -0,0 +1,32 @@
+% == No, Emacs this is -*-Prolog-*- code, not what you thought... =============
+
+sa_names(fzn(preds(IP), vars(IV), constrs(IC), SOLVE),
+	 fzn(preds(OP), vars(OV), constrs(OC), SOLVE, ST)) :-
+    sa_n_traverse(IP, OP, [], ST1),  % predicates
+    sa_n_traverse(IV, OV, ST1, ST2), % variables
+    sa_n_traverse(IC, OC, ST2, ST).  % constraints
+
+% -----------------------------------------------------------------------------
+
+sa_n_traverse([], [], ST, ST).
+sa_n_traverse([N|Ns], [NN|NNs], IST, OST) :-
+    sa_n(N, NN, IST, MST),
+    sa_n_traverse(Ns, NNs, MST, OST).
+
+
+% - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
+%
+% sa_n(AST_N_IN, AST_N_OUT, ST_IN, ST_OUT)
+
+sa_n(var(N,T,I,A), var(N,T), IST, OST) :-
+    sa_attribs(A, AX, IST, ST1),
+    st_insert(ST1, N, var(N,T,I,AX), OST).
+
+sa_n(constraint(_C)).
+
+% - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
+
+sa_attribs(A, NA, IST, OST) :-
+    true.
+
+% -----------------------------------------------------------------------------
diff --git a/fzn-parser/stable.pl b/fzn-parser/stable.pl
new file mode 100644
index 0000000..0f79695
--- /dev/null
+++ b/fzn-parser/stable.pl
@@ -0,0 +1,10 @@
+% == No, Emacs this is -*-Prolog-*- code, not what you thought... =============
+
+% -- Symbol table -------------------------------------------------------------
+
+st_lookup([K=V|_], K, V).
+st_lookup([_|ST], K, V) :- st_lookup(ST, K, V).
+
+st_insert([], K, V, [K=V]) :- !.
+st_insert([K=_|_], K, _, _) :- !, throw(duplicate(K)).
+st_insert([KV0|ST], K, V, [KV0|STx]) :- st_insert(ST, K, V, STx).
diff --git a/fzn-parser/types.pl b/fzn-parser/types.pl
new file mode 100644
index 0000000..bac9eca
--- /dev/null
+++ b/fzn-parser/types.pl
@@ -0,0 +1,6 @@
+% == No, Emacs this is -*-Prolog-*- code, not what you thought... =============
+
+% sa_type/2 - locate the TYPE field
+
+sa_type(var(_NAME,TYPE,_INIT,_ANNOT), TYPE).
+sa_type(constraint(_NAME)).
--
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