parser: new *read-unknown-structs* variable.

* parser.c (read_unknown_structs_s): New symbol variable.
(parser_common_init): Initialize read_unknown_structs flag
member of the parser structure from the new special variable.
(parse_init): Initialize read_unknown_struct_s variable.
Register the *read-unknown-structs* dynamic variable.

* parser.h (struct parser): New member, read_unknown_structs.
(read_unknown_structs_s): Declared.

* parser.y (struct): Generate the struct literal syntax not
only for quasiquoted structures, but for structures with an
unknown type name, if the read_unkonwn_structs flag is set.

* txr.1: Documented.

* share/txr/stdlib/doc-syms.tl: Regenerated.

* y.tab.c.shipped: Regenerated.

1 files changed, 4 insertions, 3 deletions

diff --git a/parser.y b/parser.y
index bdc72010..d7c31c8b 100644
--- a/parser.y
+++ b/parser.y
@@ -903,9 +903,10 @@ hash : HASH_H list              { if (parser->quasi_level > 0 && unquotes_occur(
                                     yybadtok(yychar, lit("hash literal")); }
      ;
 
-struct : HASH_S list            { if (parser->quasi_level > 0 && unquotes_occur($2, 0))
-                                    $$ = rl(cons(struct_lit_s, $2),
-                                              num($1));
+struct : HASH_S list            { if ((parser->quasi_level > 0 && unquotes_occur($2, 0)) ||
+                                      (parser->read_unknown_structs &&
+                                        !find_struct_type(first($2))))
+                                  { $$ = rl(cons(struct_lit_s, $2), num($1)); }
                                   else
                                   { val strct = make_struct_lit(first($2),
                                                                 rest($2));