Use round-to-nearest internally in jn, test with ALL_RM_TEST (bug 18602).
[glibc.git] / sysdeps / ieee754 / ldbl-96 / s_cosl.c
blob8b0b7d3cc2784ae2aeb9885aa9faeecc492d0c8d
1 /* s_cosl.c -- long double version of s_cos.c.
2 * Conversion to long double by Ulrich Drepper,
3 * Cygnus Support, drepper@cygnus.com.
4 */
6 /*
7 * ====================================================
8 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
10 * Developed at SunPro, a Sun Microsystems, Inc. business.
11 * Permission to use, copy, modify, and distribute this
12 * software is freely granted, provided that this notice
13 * is preserved.
14 * ====================================================
17 #if defined(LIBM_SCCS) && !defined(lint)
18 static char rcsid[] = "$NetBSD: $";
19 #endif
21 /* cosl(x)
22 * Return cosine function of x.
24 * kernel function:
25 * __kernel_sinl ... sine function on [-pi/4,pi/4]
26 * __kernel_cosl ... cosine function on [-pi/4,pi/4]
27 * __ieee754_rem_pio2l ... argument reduction routine
29 * Method.
30 * Let S,C and T denote the sin, cos and tan respectively on
31 * [-PI/4, +PI/4]. Reduce the argument x to y1+y2 = x-k*pi/2
32 * in [-pi/4 , +pi/4], and let n = k mod 4.
33 * We have
35 * n sin(x) cos(x) tan(x)
36 * ----------------------------------------------------------
37 * 0 S C T
38 * 1 C -S -1/T
39 * 2 -S -C T
40 * 3 -C S -1/T
41 * ----------------------------------------------------------
43 * Special cases:
44 * Let trig be any of sin, cos, or tan.
45 * trig(+-INF) is NaN, with signals;
46 * trig(NaN) is that NaN;
48 * Accuracy:
49 * TRIG(x) returns trig(x) nearly rounded
52 #include <errno.h>
53 #include <math.h>
54 #include <math_private.h>
56 long double __cosl(long double x)
58 long double y[2],z=0.0;
59 int32_t n, se, i0, i1;
61 /* High word of x. */
62 GET_LDOUBLE_WORDS(se,i0,i1,x);
64 /* |x| ~< pi/4 */
65 se &= 0x7fff;
66 if(se < 0x3ffe || (se == 0x3ffe && i0 <= 0xc90fdaa2))
67 return __kernel_cosl(x,z);
69 /* cos(Inf or NaN) is NaN */
70 else if (se==0x7fff) {
71 if (i1 == 0 && i0 == 0x80000000)
72 __set_errno (EDOM);
73 return x-x;
76 /* argument reduction needed */
77 else {
78 n = __ieee754_rem_pio2l(x,y);
79 switch(n&3) {
80 case 0: return __kernel_cosl(y[0],y[1]);
81 case 1: return -__kernel_sinl(y[0],y[1],1);
82 case 2: return -__kernel_cosl(y[0],y[1]);
83 default:
84 return __kernel_sinl(y[0],y[1],1);
88 weak_alias (__cosl, cosl)