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, 15 insertions, 1 deletions

diff --git a/txr.1 b/txr.1
index c0ce427b..4abfebb1 100644
--- a/txr.1
+++ b/txr.1
@@ -33055,10 +33055,12 @@ using the
 .code format
 string and additional arguments.
 
-.coNP Macro @ catch
+.coNP Macros @ catch and @ catch*
 .synb
 .mets (catch < try-expression
 .mets \ \  >> {( symbol <> ( arg *) << body-form *)}*)
+.mets (catch* < try-expression
+.mets \ \  >> {( symbol >> ( type-arg << arg *) << body-form *)}*)
 .syne
 .desc
 The
@@ -33113,6 +33115,18 @@ If there is only one element,
 takes on the value
 .codn nil .
 
+The
+.code catch*
+macro is a variant of
+.code catch
+with the following difference: when
+.code catch*
+invokes a clause, it passes the exception symbol as the leftmost argument
+.metn type-arg .
+Then the exception arguments follow. In contrast,
+only the exception arguments are passed to the clauses of
+.codn catch .
+
 Also see: the
 .code unwind-protect
 operator, and the functions