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, 10 insertions, 3 deletions

diff --git a/share/txr/stdlib/except.tl b/share/txr/stdlib/except.tl
index 17055207..abba8bdb 100644
--- a/share/txr/stdlib/except.tl
+++ b/share/txr/stdlib/except.tl
@@ -27,9 +27,16 @@
 (defun sys:handle-bad-syntax (item)
   (throwf 'eval-error "~s: bad clause syntax: ~s" 'handle item))
 
-(defmacro catch (try-form . handle-clauses)
-  (let ((catch-syms [mapcar car handle-clauses]))
-    ^(sys:catch ,catch-syms ,try-form ,*handle-clauses)))
+(defmacro catch (:form form try-form . catch-clauses)
+  (let ((catch-syms [mapcar car catch-clauses])
+        (sys-catch-clauses (mapcar (do mac-param-bind @1 (type args . body) @1
+                                     ^(,type (,(gensym) ,*args) ,*body))
+                                   catch-clauses)))
+    ^(sys:catch ,catch-syms ,try-form ,*sys-catch-clauses)))
+
+(defmacro catch* (try-form . catch-clauses)
+  (let ((catch-syms [mapcar car catch-clauses]))
+    ^(sys:catch ,catch-syms ,try-form ,*catch-clauses)))
 
 (defmacro handle (:whole form try-form . handle-clauses)
   (let* ((exc-sym (gensym))