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/* poly/eval.c
*
* Copyright (C) 2009 Marc JOURDAIN
*
* This program 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.
*
* This program 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 this program; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
*/
#include <config.h>
#include <gsl/gsl_errno.h>
#include <gsl/gsl_poly.h>
int
gsl_poly_eval_derivs (const double c[], const size_t lenc, const double x,
double res[], const size_t lenres)
{
size_t i, n, nmax;
size_t k, l, lmax;
for (i = 0, n = 0, nmax = 0; i < lenres; i++)
{
if (n < lenc)
{
res[i] = c[lenc - 1];
nmax = n;
n++;
}
else
res[i] = 0.0;
}
for (i = 0; i < lenc - 1; i++)
{
k = (lenc - 1) - i;
res[0] = ((x * res[0]) + c[k - 1]);
lmax = (nmax < k) ? nmax : k - 1;
for (l = 1; l <= lmax; l++)
{
res[l] = ((x * res[l]) + res[l - 1]);
}
}
{
double f = 1.0;
for (i = 2; i <= nmax; i++)
{
f *= i;
res[i] *= f;
}
}
return GSL_SUCCESS;
}
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