mirror of
git://gcc.gnu.org/git/gcc.git
synced 2024-12-30 02:24:45 +08:00
77 lines
2.2 KiB
C
77 lines
2.2 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 (libgfortran).
|
||
|
|
|
||
|
|
Libgfortran is free software; you can redistribute it and/or
|
||
|
|
modify it under the terms of the GNU General Public
|
||
|
|
License as published by the Free Software Foundation; either
|
||
|
|
version 2 of the License, or (at your option) any later version.
|
||
|
|
|
||
|
|
In addition to the permissions in the GNU General Public License, the
|
||
|
|
Free Software Foundation gives you unlimited permission to link the
|
||
|
|
compiled version of this file into combinations with other programs,
|
||
|
|
and to distribute those combinations without any restriction coming
|
||
|
|
from the use of this file. (The General Public License restrictions
|
||
|
|
do apply in other respects; for example, they cover modification of
|
||
|
|
the file, and distribution when not linked into a combine
|
||
|
|
executable.)
|
||
|
|
|
||
|
|
Libgfortran 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 General Public License for more details.
|
||
|
|
|
||
|
|
You should have received a copy of the GNU General Public
|
||
|
|
License along with libgfortran; see the file COPYING. If not,
|
||
|
|
write to the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
|
||
|
|
Boston, MA 02110-1301, USA. */
|
||
|
|
|
||
|
|
#include "config.h"
|
||
|
|
#include "libgfortran.h"
|
||
|
|
|
||
|
|
/* Use 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. */
|
||
|
|
|
||
|
|
#if defined (HAVE_GFC_COMPLEX_16) && defined (HAVE_GFC_INTEGER_16)
|
||
|
|
|
||
|
|
GFC_COMPLEX_16 pow_c16_i16 (GFC_COMPLEX_16 a, GFC_INTEGER_16 b);
|
||
|
|
export_proto(pow_c16_i16);
|
||
|
|
|
||
|
|
GFC_COMPLEX_16
|
||
|
|
pow_c16_i16 (GFC_COMPLEX_16 a, GFC_INTEGER_16 b)
|
||
|
|
{
|
||
|
|
GFC_COMPLEX_16 pow, x;
|
||
|
|
GFC_INTEGER_16 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;
|
||
|
|
}
|
||
|
|
|
||
|
|
#endif
|