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`/* Support routines for the intrinsic power (**) operator.
Copyright (C) 2004-2020 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 3 of the License, or (at your option) any later version.
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.
Under Section 7 of GPL version 3, you are granted additional
permissions described in the GCC Runtime Library Exception, version
3.1, as published by the Free Software Foundation.
You should have received a copy of the GNU General Public License and
a copy of the GCC Runtime Library Exception along with this program;
see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
<http://www.gnu.org/licenses/>. */
#include "libgfortran.h"'
include(iparm.m4)dnl
/* 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_'rtype_name`) && defined (HAVE_'atype_name`)'
rtype_name `pow_'rtype_code`_'atype_code` ('rtype_name` a, 'atype_name` b);
export_proto(pow_'rtype_code`_'atype_code`);
'rtype_name`
pow_'rtype_code`_'atype_code` ('rtype_name` a, 'atype_name` b)
{
'rtype_name` pow, x;
'atype_name` n;
GFC_UINTEGER_'atype_kind` 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;
',`
u = -n;
x = pow / x;
')dnl
` }
else
{
u = n;
}
for (;;)
{
if (u & 1)
pow *= x;
u >>= 1;
if (u)
x *= x;
else
break;
}
}
return pow;
}
#endif'
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