Adding whena macro.

We have ifa and conda; whena is conspicuously absent.

* lisplib.c (ifa_set_entries): Add autoload entry for whena.

* share/txr/stdlib/ifa.tl (whena): New macro.

* txr.1: Documented whena.

1 files changed, 17 insertions, 0 deletions

diff --git a/txr.1 b/txr.1
index 65c6c940..9bdc0cd4 100644
--- a/txr.1
+++ b/txr.1
@@ -14283,6 +14283,23 @@ as well as the anaphoric
 .code it
 variable feature.
 
+.coNP Macro @ whena
+.synb
+.mets (whena < test << form *)
+.syne
+.desc
+The
+.code whena
+macro is similar to the
+.code when
+macro, except that it is anaphoric in exactly the same manner as the
+.code ifa
+macro. It may be understood as conforming to the following equivalence:
+
+.cblk
+  (whena x f0 f2 ...)  <-->  (if x (progn f0 f2 ...))
+.cble
+
 .coNP Macro @ dotimes
 .synb
 .mets (dotimes >> ( var < count-form <> [ result-form ]) << body-form *)