New condlet macro; small change to iflet/whenlet.

* eval.c (me_iflet_whenlet): Allow the test form
to be an atomic expression instead of bindings.
This allows iflet to be used as the sole target
construct of condlet, while allowing condlet to
have a fallback clause with t. It also means that
an empty list of bindings is allowed (since it
is the atom nil).

* lisplib.c (ifa_set_entries): Add "condlet" to
the autoload names for the ifa module. That's
where we are adding condlet.

* share/txr/stdlib/ifa.tl (sys:if-to-cond): New
macro expander helper function, generalizing the writing
cond-like macros based on if-like operators.
(conda): Rewritten using sys:if-to-cond.
(condlet): New macro.

* txr.1: Documented change in iflet/whenlet.
Documented condlet.

1 files changed, 1 insertions, 1 deletions

diff --git a/lisplib.c b/lisplib.c
index e06b62e6..fcaf05f1 100644
--- a/lisplib.c
+++ b/lisplib.c
@@ -102,7 +102,7 @@ static val ver_instantiate(val set_fun)
 
 static val ifa_set_entries(val dlt, val fun)
 {
-  val name[] = { lit("ifa"), lit("conda"), nil };
+  val name[] = { lit("ifa"), lit("conda"), lit("condlet"), nil };
   set_dlt_entries(dlt, name, fun);
   return nil;
 }