Extending syntax to allow for @VAR and @(...) forms inside

nested lists. This is in anticipation of future features.

* lib.c (expr_s): New symbol variable.
(obj_init): expr_s initialized.

* lib.h (expr_s): Declared.

* match.c (dest_bind): Now takes linenum. Tests for the meta-syntax
denoted by the system symbols var_s and expr_s, and throws an
error.
(eval_form): Similar error checks added. Also, hack: do not add
file and line number to an exception which begins with a '('
character; just re-throw it. This suppresses duplicate line
number addition when this throw occurs across some nestings.
(match_files): Updated calls to dest_bind.

* parser.l (yybadtoken): Handle new token kind, METAVAR and METAPAR.
(grammar): Refactoring among patterns: TOK broken into
SYM and NUM, NTOK introduced, unused NUM_END removed.
Rule for @( producing METAPAR in nested state.

* parser.y (METAVAR, METAPAR): New tokens.
(meta_expr): New nonterminal.
(expr): meta_expr and META_VAR productions handled.

1 files changed, 2 insertions, 1 deletions

diff --git a/lib.c b/lib.c
index b5562c54..ed1e737a 100644
--- a/lib.c
+++ b/lib.c
@@ -52,7 +52,7 @@ val system_package, keyword_package, user_package;
 
 val null, t, cons_s, str_s, chr_s, num_s, sym_s, pkg_s, fun_s, vec_s;
 val stream_s, hash_s, hash_iter_s, lcons_s, lstr_s, cobj_s;
-val var_s, regex_s, chset_s, set_s, cset_s, wild_s, oneplus_s;
+val var_s, expr_s, regex_s, chset_s, set_s, cset_s, wild_s, oneplus_s;
 val nongreedy_s, compiled_regex_s;
 val zeroplus_s, optional_s, compl_s, compound_s, or_s, and_s, quasi_s;
 val skip_s, trailer_s, block_s, next_s, freeform_s, fail_s, accept_s;
@@ -2165,6 +2165,7 @@ static void obj_init(void)
   lstr_s = intern(lit("lstr"), user_package);
   cobj_s = intern(lit("cobj"), user_package);
   var_s = intern(lit("var"), system_package);
+  expr_s = intern(lit("expr"), system_package);
   regex_s = intern(lit("regex"), system_package);
   nongreedy_s = intern(lit("nongreedy"), system_package);
   compiled_regex_s = intern(lit("compiled-regex"), system_package);