mirror of
https://https.git.savannah.gnu.org/git/gnulib.git
synced 2026-09-01 02:34:55 +00:00
Bruno Haible
105 lines
3.0 KiB
C
105 lines
3.0 KiB
C
/* s_cosl.c -- long double version of s_sin.c.
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* Conversion to long double by Jakub Jelinek, jj@ultra.linux.cz.
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*/
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/*
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* ====================================================
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* Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
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*
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* Developed at SunPro, a Sun Microsystems, Inc. business.
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* Permission to use, copy, modify, and distribute this
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* software is freely granted, provided that this notice
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* is preserved.
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* ====================================================
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*/
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#include <config.h>
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/* Specification. */
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#include <math.h>
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/* sinl(x)
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* Return sine function of x.
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*
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* kernel function:
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* __kernel_sinl ... sine function on [-pi/4,pi/4]
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* __kernel_cosl ... cose function on [-pi/4,pi/4]
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* __ieee754_rem_pio2l ... argument reduction routine
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*
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* Method.
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* Let S,C and T denote the sin, cos and tan respectively on
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* [-PI/4, +PI/4]. Reduce the argument x to y1+y2 = x-k*pi/2
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* in [-pi/4 , +pi/4], and let n = k mod 4.
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* We have
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*
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* n sin(x) cos(x) tan(x)
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* ----------------------------------------------------------
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* 0 S C T
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* 1 C -S -1/T
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* 2 -S -C T
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* 3 -C S -1/T
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* ----------------------------------------------------------
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*
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* Special cases:
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* Let trig be any of sin, cos, or tan.
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* trig(+-INF) is NaN, with signals;
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* trig(NaN) is that NaN;
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*
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* Accuracy:
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* TRIG(x) returns trig(x) nearly rounded
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*/
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#include "trigl.h"
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long double
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cosl (long double x)
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{
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long double y[2],z=0.0L;
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int n;
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/* cosl(NaN) is NaN */
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if (isnanl (x))
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return x;
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/* |x| ~< pi/4 */
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if (x >= -0.7853981633974483096156608458198757210492
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&& x <= 0.7853981633974483096156608458198757210492)
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return kernel_cosl(x, z);
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/* cosl(Inf) is NaN, cosl(0) is 1 */
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else if (x + x == x && x != 0.0)
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return x - x; /* NaN */
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/* argument reduction needed */
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else
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{
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n = ieee754_rem_pio2l (x, y);
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switch (n & 3)
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{
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case 0:
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return kernel_cosl (y[0], y[1]);
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case 1:
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return -kernel_sinl (y[0], y[1], 1);
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case 2:
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return -kernel_cosl (y[0], y[1]);
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default:
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return kernel_sinl (y[0], y[1], 1);
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}
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}
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}
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#if 0
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int
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main (void)
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{
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printf ("%.16Lg\n", cosl (0.7853981633974483096156608458198757210492));
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printf ("%.16Lg\n", cosl (0.7853981633974483096156608458198757210492 *29));
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printf ("%.16Lg\n", cosl (0.7853981633974483096156608458198757210492 *2));
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printf ("%.16Lg\n", cosl (0.7853981633974483096156608458198757210492 *30));
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printf ("%.16Lg\n", cosl (0.7853981633974483096156608458198757210492 *4));
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printf ("%.16Lg\n", cosl (0.7853981633974483096156608458198757210492 *32));
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printf ("%.16Lg\n", cosl (0.7853981633974483096156608458198757210492 *2/3));
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printf ("%.16Lg\n", cosl (0.7853981633974483096156608458198757210492 *4/3));
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}
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#endif
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