New catch*, giving access to exception symbol.

* eval.c (op_catch): The sys:catch operator now passes the
exception symbol as the first argument of each clause.
This means the catch macro must be adjusted.

* share/txr/stdlib/except.tl (catch): Macro now inserts
a gensym dummy first argument into each clause to take the
symbol passed by the sys:catch operator.
(catch*): New macro, which is identical to the previous
catch macro, and thus exposes the symbol passed as the
first argument.

* txr.1: Documented catch*.

* tests/012/struct.tl: Some gensym numbers need adjusting
in one test case.

1 files changed, 4 insertions, 1 deletions

diff --git a/eval.c b/eval.c
index b46cfb05..74521190 100644
--- a/eval.c
+++ b/eval.c
@@ -2285,10 +2285,13 @@ static val op_catch(val form, val env)
   result = eval(try_form, env, try_form);
 
   uw_catch(exsym, exvals) {
-    args_decl_list(args, ARGS_MIN, exvals);
+    args_decl(args, ARGS_MIN);
     val catches = rest(rest(rest(form)));
     val iter;
 
+    args_add(args, exsym);
+    args_add_list(args, exvals);
+
     for (iter = catches; iter; iter = cdr(iter)) {
       val clause = car(iter);
       val type = first(clause);