(Fexpt): Use floats for negative exponent.

2 files changed, 7 insertions, 1 deletions

diff --git a/src/ChangeLog b/src/ChangeLog
index 6d8608dde22..9ff58e7f5a8 100644
--- a/src/ChangeLog
+++ b/src/ChangeLog
@@ -1,3 +1,8 @@
+2005-08-06  Thien-Thi Nguyen  <ttn@gnu.org>
+
+        * floatfns.c (Fexpt): Use floats for negative
+        exponent (computing a root).  Reported by D Goel.
+
 2005-08-02  Richard M. Stallman  <rms@gnu.org>
 
         * frame.c (Fframe_char_width): Doc fix.
diff --git a/src/floatfns.c b/src/floatfns.c
index 529e7b76e39..cbcc0bfe520 100644
--- a/src/floatfns.c
+++ b/src/floatfns.c
@@ -460,7 +460,8 @@ DEFUN ("expt", Fexpt, Sexpt, 2, 2, 0,
   CHECK_NUMBER_OR_FLOAT (arg1);
   CHECK_NUMBER_OR_FLOAT (arg2);
   if (INTEGERP (arg1)     /* common lisp spec */
-      && INTEGERP (arg2)) /* don't promote, if both are ints */
+      && INTEGERP (arg2)   /* don't promote, if both are ints, and */
+      && 0 <= XINT (arg2)) /* we are not computing the -ARG2 root */
     {                           /* this can be improved by pre-calculating */
       EMACS_INT acc, x, y;      /* some binary powers of x then accumulating */
       Lisp_Object val;