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/*
* Copyright (c) 2003 Matteo Frigo
* Copyright (c) 2003 Massachusetts Institute of Technology
*
* 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 2 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., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*
*/
/* $Id: trig1.c,v 1.1 2008/10/17 06:11:29 scuri Exp $ */
/* trigonometric functions */
#include "ifftw.h"
#include <math.h>
#ifdef FFTW_LDOUBLE
# define COS cosl
# define SIN sinl
# define TAN tanl
# define KTRIG(x) (x##L)
#else
# define COS cos
# define SIN sin
# define TAN tan
# define KTRIG(x) (x)
#endif
static const trigreal K2PI =
KTRIG(6.2831853071795864769252867665590057683943388);
#define by2pi(m, n) ((K2PI * (m)) / (n))
/*
* Improve accuracy by reducing x to range [0..1/8]
* before multiplication by 2 * PI.
*/
trigreal X(sincos)(trigreal m, trigreal n, int sinp)
{
/* waiting for C to get tail recursion... */
trigreal half_n = n * KTRIG(0.5);
trigreal quarter_n = half_n * KTRIG(0.5);
trigreal eighth_n = quarter_n * KTRIG(0.5);
trigreal sgn = KTRIG(1.0);
if (sinp) goto sin;
cos:
if (m < 0) { m = -m; /* goto cos; */ }
if (m > half_n) { m = n - m; goto cos; }
if (m > eighth_n) { m = quarter_n - m; goto sin; }
return sgn * COS(by2pi(m, n));
msin:
sgn = -sgn;
sin:
if (m < 0) { m = -m; goto msin; }
if (m > half_n) { m = n - m; goto msin; }
if (m > eighth_n) { m = quarter_n - m; goto cos; }
return sgn * SIN(by2pi(m, n));
}
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