diff options
Diffstat (limited to 'src/floatfns.c')
| -rw-r--r-- | src/floatfns.c | 26 |
1 files changed, 7 insertions, 19 deletions
diff --git a/src/floatfns.c b/src/floatfns.c index c44784f2120..87fa19acb1f 100644 --- a/src/floatfns.c +++ b/src/floatfns.c @@ -484,31 +484,19 @@ DEFUN ("expt", Fexpt, Sexpt, 2, 2, 0, && INTEGERP (arg2) /* don't promote, if both are ints, and */ && 0 <= XINT (arg2)) /* we are sure the result is not fractional */ { /* this can be improved by pre-calculating */ - EMACS_INT acc, x, y; /* some binary powers of x then accumulating */ + EMACS_INT y; /* some binary powers of x then accumulating */ + EMACS_UINT acc, x; /* Unsigned so that overflow is well defined. */ Lisp_Object val; x = XINT (arg1); y = XINT (arg2); - acc = 1; + acc = (y & 1 ? x : 1); - if (y < 0) + while ((y >>= 1) != 0) { - if (x == 1) - acc = 1; - else if (x == -1) - acc = (y & 1) ? -1 : 1; - else - acc = 0; - } - else - { - while (y > 0) - { - if (y & 1) - acc *= x; - x *= x; - y >>= 1; - } + x *= x; + if (y & 1) + acc *= x; } XSETINT (val, acc); return val; |