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comparison lib/cosl.c @ 4239:b33b8603715c

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Transcendental functions for 'long double', from Paolo Bonzini.
author Bruno Haible <bruno@clisp.org>
date Tue, 18 Feb 2003 17:05:23 +0000
parents
children b09c3f1225b6
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4238:b0b208dbaf73 4239:b33b8603715c
1 /* s_cosl.c -- long double version of s_sin.c.
2 * Conversion to long double by Jakub Jelinek, jj@ultra.linux.cz.
3 */
4
5 /*
6 * ====================================================
7 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
8 *
9 * Developed at SunPro, a Sun Microsystems, Inc. business.
10 * Permission to use, copy, modify, and distribute this
11 * software is freely granted, provided that this notice
12 * is preserved.
13 * ====================================================
14 */
15
16 /* sinl(x)
17 * Return sine function of x.
18 *
19 * kernel function:
20 * __kernel_sinl ... sine function on [-pi/4,pi/4]
21 * __kernel_cosl ... cose function on [-pi/4,pi/4]
22 * __ieee754_rem_pio2l ... argument reduction routine
23 *
24 * Method.
25 * Let S,C and T denote the sin, cos and tan respectively on
26 * [-PI/4, +PI/4]. Reduce the argument x to y1+y2 = x-k*pi/2
27 * in [-pi/4 , +pi/4], and let n = k mod 4.
28 * We have
29 *
30 * n sin(x) cos(x) tan(x)
31 * ----------------------------------------------------------
32 * 0 S C T
33 * 1 C -S -1/T
34 * 2 -S -C T
35 * 3 -C S -1/T
36 * ----------------------------------------------------------
37 *
38 * Special cases:
39 * Let trig be any of sin, cos, or tan.
40 * trig(+-INF) is NaN, with signals;
41 * trig(NaN) is that NaN;
42 *
43 * Accuracy:
44 * TRIG(x) returns trig(x) nearly rounded
45 */
46
47 #include <math.h>
48
49 #include "mathl.h"
50
51 #include "trigl.h"
52 #ifdef HAVE_SINL
53 #include "trigl.c"
54 #include "sincosl.c"
55 #endif
56
57 long double cosl(long double x)
58 {
59 long double y[2],z=0.0L;
60 int n;
61
62 /* |x| ~< pi/4 */
63 if(x >= -0.7853981633974483096156608458198757210492 &&
64 x <= 0.7853981633974483096156608458198757210492)
65 return kernel_cosl(x, z);
66
67 /* sinl(Inf or NaN) is NaN, sinl(0) is 0 */
68 else if ((x + x == x && x != 0.0) || x != x)
69 return x-x; /* NaN */
70
71 /* argument reduction needed */
72 else {
73 n = ieee754_rem_pio2l(x,y);
74 switch(n&3) {
75 case 0: return kernel_cosl(y[0],y[1]);
76 case 1: return -kernel_sinl(y[0],y[1],1);
77 case 2: return -kernel_cosl(y[0],y[1]);
78 default:
79 return kernel_sinl(y[0],y[1],1);
80 }
81 }
82 }
83
84 #if 0
85 int
86 main ()
87 {
88 printf ("%.16Lg\n", cosl(0.7853981633974483096156608458198757210492));
89 printf ("%.16Lg\n", cosl(0.7853981633974483096156608458198757210492 *29));
90 printf ("%.16Lg\n", cosl(0.7853981633974483096156608458198757210492 *2));
91 printf ("%.16Lg\n", cosl(0.7853981633974483096156608458198757210492 *30));
92 printf ("%.16Lg\n", cosl(0.7853981633974483096156608458198757210492 *4));
93 printf ("%.16Lg\n", cosl(0.7853981633974483096156608458198757210492 *32));
94 printf ("%.16Lg\n", cosl(0.7853981633974483096156608458198757210492 *2/3));
95 printf ("%.16Lg\n", cosl(0.7853981633974483096156608458198757210492 *4/3));
96 }
97 #endif