* Makefile (conftest, conftest2): Link math

library so we can test for math functions.

* arith.c (log2_init): New static function.
(log2, logtwo): New functions.
(l2): New static variable.
(arith_init): Call log2_init.

* configure (lang_flags): Switching _XOPEN_SOURCE
from 500 to 600 to reveal log2.
Adding test for log2.

* eval.c (eval_init): Register log2 intrinsic.

* lib.h (logtwo): Declared.

* txr.1: Documented log2.

1 files changed, 1 insertions, 0 deletions

diff --git a/lib.h b/lib.h
index 81fea9b8..27b5c544 100644
--- a/lib.h
+++ b/lib.h
@@ -544,6 +544,7 @@ val atang(val);
 val atang2(val, val);
 val loga(val);
 val logten(val num);
+val logtwo(val num);
 val expo(val);
 val logand(val, val);
 val logior(val, val);