69 lines
1.7 KiB
Plaintext
69 lines
1.7 KiB
Plaintext
|
`/* 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"'
|
||
|
|
include(iparm.m4)dnl
|
||
|
|
|
||
|
|
/* 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. */
|
||
|
|
|
||
|
|
rtype_name
|
||
|
|
`prefix(pow_'rtype_code`_'atype_code) (rtype_name a, atype_name b)
|
||
|
|
{
|
||
|
|
rtype_name pow, x;
|
||
|
|
atype_name n, u;
|
||
|
|
|
||
|
|
n = b;
|
||
|
|
x = a;
|
||
|
|
pow = 1;
|
||
|
|
if (n != 0)
|
||
|
|
{
|
||
|
|
if (n < 0)
|
||
|
|
{
|
||
|
|
ifelse(rtype_letter,i,`dnl
|
||
|
|
if (x == 1)
|
||
|
|
return 1;
|
||
|
|
if (x == -1)
|
||
|
|
return (n & 1) ? -1 : 1;
|
||
|
|
return (x == 0) ? 1 / x : 0;
|
||
|
|
',`
|
||
|
|
n = -n;
|
||
|
|
x = pow / x;
|
||
|
|
')dnl
|
||
|
|
}
|
||
|
|
u = n;
|
||
|
|
for (;;)
|
||
|
|
{
|
||
|
|
if (u & 1)
|
||
|
|
pow *= x;
|
||
|
|
u >>= 1;
|
||
|
|
if (u)
|
||
|
|
x *= x;
|
||
|
|
else
|
||
|
|
break;
|
||
|
|
}
|
||
|
|
}
|
||
|
|
return pow;
|
||
|
|
}
|