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/* sys/pow_int.c
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*
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* Copyright (C) 1996, 1997, 1998, 1999, 2000 Gerard Jungman
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 3 of the License, or (at
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* your option) any later version.
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*
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* This program is distributed in the hope that it will be useful, but
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* WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
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*/
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#include <config.h>
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#include <math.h>
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/* Compile all the inline functions */
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#define COMPILE_INLINE_STATIC
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#include "build.h"
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#include <gsl/gsl_pow_int.h>
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double gsl_pow_int(double x, int n)
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{
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unsigned int un;
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if(n < 0) {
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x = 1.0/x;
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un = -n;
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} else {
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un = n;
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}
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return gsl_pow_uint(x, un);
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}
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double gsl_pow_uint(double x, unsigned int n)
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{
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double value = 1.0;
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/* repeated squaring method
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* returns 0.0^0 = 1.0, so continuous in x
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*/
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do {
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if(n & 1) value *= x; /* for n odd */
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n >>= 1;
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x *= x;
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} while (n);
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return value;
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}
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