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/* @(#)s_cos.c 5.1 93/09/24 */
/*
 * ====================================================
 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
 *
 * Developed at SunPro, a Sun Microsystems, Inc. business.
 * Permission to use, copy, modify, and distribute this
 * software is freely granted, provided that this notice
 * is preserved.
 * ====================================================
 */
 
/* cos(x)
 * Return cosine function of x.
 *
 * kernel function:
 *      __kernel_sin            ... sine function on [-pi/4,pi/4]
 *      __kernel_cos            ... cosine function on [-pi/4,pi/4]
 *      __ieee754_rem_pio2      ... argument reduction routine
 *
 * Method.
 *      Let S,C and T denote the sin, cos and tan respectively on
 *      [-PI/4, +PI/4]. Reduce the argument x to y1+y2 = x-k*pi/2
 *      in [-pi/4 , +pi/4], and let n = k mod 4.
 *      We have
 *
 *          n        sin(x)      cos(x)        tan(x)
 *     ----------------------------------------------------------
 *          0          S           C             T
 *          1          C          -S            -1/T
 *          2         -S          -C             T
 *          3         -C           S            -1/T
 *     ----------------------------------------------------------
 *
 * Special cases:
 *      Let trig be any of sin, cos, or tan.
 *      trig(+-INF)  is NaN, with signals;
 *      trig(NaN)    is that NaN;
 *
 * Accuracy:
 *      TRIG(x) returns trig(x) nearly rounded
 */
 
#include "fdlibm.h"
 
#ifndef _DOUBLE_IS_32BITS
 
#ifdef __STDC__
        double cos(double x)
#else
        double cos(x)
        double x;
#endif
{
        double y[2],z=0.0;
        __int32_t n,ix;
 
    /* High word of x. */
        GET_HIGH_WORD(ix,x);
 
    /* |x| ~< pi/4 */
        ix &= 0x7fffffff;
        if(ix <= 0x3fe921fb) return __kernel_cos(x,z);
 
    /* cos(Inf or NaN) is NaN */
        else if (ix>=0x7ff00000) return x-x;
 
    /* argument reduction needed */
        else {
            n = __ieee754_rem_pio2(x,y);
            switch(n&3) {
                case 0: return  __kernel_cos(y[0],y[1]);
                case 1: return -__kernel_sin(y[0],y[1],1);
                case 2: return -__kernel_cos(y[0],y[1]);
                default:
                        return  __kernel_sin(y[0],y[1],1);
            }
        }
}
 
#endif /* _DOUBLE_IS_32BITS */

Line No.	Rev	Author	Line
1	39	lampret
2			`/* @(#)s_cos.c 5.1 93/09/24 */`
3			`/*`
4			`* ====================================================`
5			`* Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.`
6			`*`
7			`* Developed at SunPro, a Sun Microsystems, Inc. business.`
8			`* Permission to use, copy, modify, and distribute this`
9			`* software is freely granted, provided that this notice`
10			`* is preserved.`
11			`* ====================================================`
12			`*/`
13
14			`/* cos(x)`
15			`* Return cosine function of x.`
16			`*`
17			`* kernel function:`
18			`* __kernel_sin ... sine function on [-pi/4,pi/4]`
19			`* __kernel_cos ... cosine function on [-pi/4,pi/4]`
20			`* __ieee754_rem_pio2 ... argument reduction routine`
21			`*`
22			`* Method.`
23			`* Let S,C and T denote the sin, cos and tan respectively on`
24			`* [-PI/4, +PI/4]. Reduce the argument x to y1+y2 = x-k*pi/2`
25			`* in [-pi/4 , +pi/4], and let n = k mod 4.`
26			`* We have`
27			`*`
28			`* n sin(x) cos(x) tan(x)`
29			`* ----------------------------------------------------------`
30			`* 0 S C T`
31			`* 1 C -S -1/T`
32			`* 2 -S -C T`
33			`* 3 -C S -1/T`
34			`* ----------------------------------------------------------`
35			`*`
36			`* Special cases:`
37			`* Let trig be any of sin, cos, or tan.`
38			`* trig(+-INF) is NaN, with signals;`
39			`* trig(NaN) is that NaN;`
40			`*`
41			`* Accuracy:`
42			`* TRIG(x) returns trig(x) nearly rounded`
43			`*/`
44
45			`#include "fdlibm.h"`
46
47			`#ifndef _DOUBLE_IS_32BITS`
48
49			`#ifdef __STDC__`
50			`double cos(double x)`
51			`#else`
52			`double cos(x)`
53			`double x;`
54			`#endif`
55			`{`
56			`double y[2],z=0.0;`
57			`__int32_t n,ix;`
58
59			`/* High word of x. */`
60			`GET_HIGH_WORD(ix,x);`
61
62			`/* \|x\| ~< pi/4 */`
63			`ix &= 0x7fffffff;`
64			`if(ix <= 0x3fe921fb) return __kernel_cos(x,z);`
65
66			`/* cos(Inf or NaN) is NaN */`
67			`else if (ix>=0x7ff00000) return x-x;`
68
69			`/* argument reduction needed */`
70			`else {`
71			`n = __ieee754_rem_pio2(x,y);`
72			`switch(n&3) {`
73			`case 0: return __kernel_cos(y[0],y[1]);`
74			`case 1: return -__kernel_sin(y[0],y[1],1);`
75			`case 2: return -__kernel_cos(y[0],y[1]);`
76			`default:`
77			`return __kernel_sin(y[0],y[1],1);`
78			`}`
79			`}`
80			`}`
81
82			`#endif /* _DOUBLE_IS_32BITS */`

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[/] [or1k/] [trunk/] [newlib/] [newlib/] [libm/] [math/] [s_cos.c] - Blame information for rev 1771