* 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/eval.c b/eval.c
index e8c1c7da..b5ded23a 100644
--- a/eval.c
+++ b/eval.c
@@ -3585,6 +3585,7 @@ void eval_init(void)
   reg_fun(intern(lit("atan2"), user_package), func_n2(atang2));
   reg_fun(intern(lit("log"), user_package), func_n1(loga));
   reg_fun(intern(lit("log10"), user_package), func_n1(logten));
+  reg_fun(intern(lit("log2"), user_package), func_n1(logtwo));
   reg_fun(intern(lit("exp"), user_package), func_n1(expo));
   reg_fun(intern(lit("sqrt"), user_package), func_n1(sqroot));
   reg_fun(intern(lit("cum-norm-dist"), user_package), func_n1(cum_norm_dist));