| 1 |
14 |
jlechner |
`/* Support routines for the intrinsic power (**) operator.
|
| 2 |
|
|
Copyright 2004 Free Software Foundation, Inc.
|
| 3 |
|
|
Contributed by Paul Brook
|
| 4 |
|
|
|
| 5 |
|
|
This file is part of the GNU Fortran 95 runtime library (libgfortran).
|
| 6 |
|
|
|
| 7 |
|
|
Libgfortran is free software; you can redistribute it and/or
|
| 8 |
|
|
modify it under the terms of the GNU General Public
|
| 9 |
|
|
License as published by the Free Software Foundation; either
|
| 10 |
|
|
version 2 of the License, or (at your option) any later version.
|
| 11 |
|
|
|
| 12 |
|
|
In addition to the permissions in the GNU General Public License, the
|
| 13 |
|
|
Free Software Foundation gives you unlimited permission to link the
|
| 14 |
|
|
compiled version of this file into combinations with other programs,
|
| 15 |
|
|
and to distribute those combinations without any restriction coming
|
| 16 |
|
|
from the use of this file. (The General Public License restrictions
|
| 17 |
|
|
do apply in other respects; for example, they cover modification of
|
| 18 |
|
|
the file, and distribution when not linked into a combine
|
| 19 |
|
|
executable.)
|
| 20 |
|
|
|
| 21 |
|
|
Libgfortran is distributed in the hope that it will be useful,
|
| 22 |
|
|
but WITHOUT ANY WARRANTY; without even the implied warranty of
|
| 23 |
|
|
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
|
| 24 |
|
|
GNU General Public License for more details.
|
| 25 |
|
|
|
| 26 |
|
|
You should have received a copy of the GNU General Public
|
| 27 |
|
|
License along with libgfortran; see the file COPYING. If not,
|
| 28 |
|
|
write to the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
|
| 29 |
|
|
Boston, MA 02110-1301, USA. */
|
| 30 |
|
|
|
| 31 |
|
|
#include "config.h"
|
| 32 |
|
|
#include "libgfortran.h"'
|
| 33 |
|
|
include(iparm.m4)dnl
|
| 34 |
|
|
|
| 35 |
|
|
/* Use Binary Method to calculate the powi. This is not an optimal but
|
| 36 |
|
|
a simple and reasonable arithmetic. See section 4.6.3, "Evaluation of
|
| 37 |
|
|
Powers" of Donald E. Knuth, "Seminumerical Algorithms", Vol. 2, "The Art
|
| 38 |
|
|
of Computer Programming", 3rd Edition, 1998. */
|
| 39 |
|
|
|
| 40 |
|
|
`#if defined (HAVE_'rtype_name`) && defined (HAVE_'atype_name`)'
|
| 41 |
|
|
|
| 42 |
|
|
rtype_name `pow_'rtype_code`_'atype_code (rtype_name a, atype_name b);
|
| 43 |
|
|
export_proto(pow_`'rtype_code`_'atype_code);
|
| 44 |
|
|
|
| 45 |
|
|
rtype_name
|
| 46 |
|
|
`pow_'rtype_code`_'atype_code (rtype_name a, atype_name b)
|
| 47 |
|
|
{
|
| 48 |
|
|
rtype_name pow, x;
|
| 49 |
|
|
atype_name n, u;
|
| 50 |
|
|
|
| 51 |
|
|
n = b;
|
| 52 |
|
|
x = a;
|
| 53 |
|
|
pow = 1;
|
| 54 |
|
|
if (n != 0)
|
| 55 |
|
|
{
|
| 56 |
|
|
if (n < 0)
|
| 57 |
|
|
{
|
| 58 |
|
|
ifelse(rtype_letter,i,`dnl
|
| 59 |
|
|
if (x == 1)
|
| 60 |
|
|
return 1;
|
| 61 |
|
|
if (x == -1)
|
| 62 |
|
|
return (n & 1) ? -1 : 1;
|
| 63 |
|
|
return (x == 0) ? 1 / x : 0;
|
| 64 |
|
|
',`
|
| 65 |
|
|
n = -n;
|
| 66 |
|
|
x = pow / x;
|
| 67 |
|
|
')dnl
|
| 68 |
|
|
}
|
| 69 |
|
|
u = n;
|
| 70 |
|
|
for (;;)
|
| 71 |
|
|
{
|
| 72 |
|
|
if (u & 1)
|
| 73 |
|
|
pow *= x;
|
| 74 |
|
|
u >>= 1;
|
| 75 |
|
|
if (u)
|
| 76 |
|
|
x *= x;
|
| 77 |
|
|
else
|
| 78 |
|
|
break;
|
| 79 |
|
|
}
|
| 80 |
|
|
}
|
| 81 |
|
|
return pow;
|
| 82 |
|
|
}
|
| 83 |
|
|
|
| 84 |
|
|
#endif
|
