Adding notation for cycles and shared structure.

This commit implements the parse-side support
for handling a notation that exists in ANSI
Common Lisp for specifying objects with cycles
and shared substructure.

* parser.h (struct parser): New members, circ_ref_hash
and circ_count.
(circref_s, parser_resolve_circ, parser_circ_def,
parser_circ_ref): Declared.

* parser.c (circref_s): New symbol variable.
(parser_mark): Visit the new circ_ref_hash member of the
parser structure.
(parser_common_init): Initialize new members
circ_ref_hash and circ_count of parser structure.
(patch_ref, circ_backpatch): New static functions.
(parser_resolve_circ, parser_circ_def, parser_circ_ref): New
functions.
(circref): New static function.
(parse_init): Initialize circref_s as sys:circref symbol.
Register sys:circref function.

* parser.l (grammar): Scan #<num>= and #<num># notation as
tokens, extracting their numeric value.

* parser.y (HASH_N_EQUALS, HASH_N_HASH): New token types.
(i_expr, n_expr): Adding phrases for hash-equalsign and
hash-hash syntax.
(yybadtoken): Handle new token types in switch.
(parse_once): Call parser_resolve_circ after parsing
to rewrite any remaining #<num># references in the
structure to the objects they denote.
(parse): Reset new struct parse members to initial
state. Call parser_resolve_circ after parsing
to rewrite any remaining #<num># references.

1 files changed, 12 insertions, 0 deletions

diff --git a/parser.l b/parser.l
index 8816bb4b..763f6544 100644
--- a/parser.l
+++ b/parser.l
@@ -708,6 +708,18 @@ UONLY   {U2}{U}|{U3}{U}{U}|{U4}{U}{U}{U}
   return HASH_R;
 }
 
+<NESTED,BRACED>#{DIG}+= {
+  val str = string_own(utf8_dup_from(yytext + 1));
+  yylval->val = int_str(str, num(10));
+  return HASH_N_EQUALS;
+}
+
+<NESTED,BRACED>#{DIG}+# {
+  val str = string_own(utf8_dup_from(yytext + 1));
+  yylval->val = int_str(str, num(10));
+  return HASH_N_HASH;
+}
+
 <NESTED>\.\. {
   yylval->lineno = yyextra->lineno;
   return DOTDOT;