61 lines
1.6 KiB
C
61 lines
1.6 KiB
C
|
/* Support routines for the intrinsic power (**) operator.
|
||
|
|
Copyright 2004 Free Software Foundation, Inc.
|
||
|
|
Contributed by Paul Brook
|
||
|
|
|
||
|
|
This file is part of the GNU Fortran 95 runtime library (libgfor).
|
||
|
|
|
||
|
|
Libgfor is free software; you can redistribute it and/or
|
||
|
|
modify it under the terms of the GNU Lesser General Public
|
||
|
|
License as published by the Free Software Foundation; either
|
||
|
|
version 2.1 of the License, or (at your option) any later version.
|
||
|
|
|
||
|
|
Ligbfor is distributed in the hope that it will be useful,
|
||
|
|
but WITHOUT ANY WARRANTY; without even the implied warranty of
|
||
|
|
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
|
||
|
|
GNU Lesser General Public License for more details.
|
||
|
|
|
||
|
|
You should have received a copy of the GNU Lesser General Public
|
||
|
|
License along with libgfor; see the file COPYING.LIB. If not,
|
||
|
|
write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
|
||
|
|
Boston, MA 02111-1307, USA. */
|
||
|
|
|
||
|
|
#include "config.h"
|
||
|
|
#include "libgfortran.h"
|
||
|
|
|
||
|
|
/* Uuse Binary Method to calculate the powi. This is not an optimal but
|
||
|
|
a simple and reasonable arithmetic. See section 4.6.3, "Evaluation of
|
||
|
|
Powers" of Donald E. Knuth, "Seminumerical Algorithms", Vol. 2, "The Art
|
||
|
|
of Computer Programming", 3rd Edition, 1998. */
|
||
|
|
|
||
|
|
GFC_COMPLEX_4
|
||
|
|
prefix(pow_c4_i8) (GFC_COMPLEX_4 a, GFC_INTEGER_8 b)
|
||
|
|
{
|
||
|
|
GFC_COMPLEX_4 pow, x;
|
||
|
|
GFC_INTEGER_8 n, u;
|
||
|
|
|
||
|
|
n = b;
|
||
|
|
x = a;
|
||
|
|
pow = 1;
|
||
|
|
if (n != 0)
|
||
|
|
{
|
||
|
|
if (n < 0)
|
||
|
|
{
|
||
|
|
|
||
|
|
n = -n;
|
||
|
|
x = pow / x;
|
||
|
|
}
|
||
|
|
u = n;
|
||
|
|
for (;;)
|
||
|
|
{
|
||
|
|
if (u & 1)
|
||
|
|
pow *= x;
|
||
|
|
u >>= 1;
|
||
|
|
if (u)
|
||
|
|
x *= x;
|
||
|
|
else
|
||
|
|
break;
|
||
|
|
}
|
||
|
|
}
|
||
|
|
return pow;
|
||
|
|
}
|