cscg22-gearboy

CSCG 2022 Challenge 'Gearboy'
git clone https://git.sinitax.com/sinitax/cscg22-gearboy
Log | Files | Refs | sfeed.txt

s_cos.c (2333B)

      1/* @(#)s_cos.c 5.1 93/09/24 */
      2/*
      3 * ====================================================
      4 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
      5 *
      6 * Developed at SunPro, a Sun Microsystems, Inc. business.
      7 * Permission to use, copy, modify, and distribute this
      8 * software is freely granted, provided that this notice
      9 * is preserved.
     10 * ====================================================
     11 */
     12
     13#if defined(LIBM_SCCS) && !defined(lint)
     14static const char rcsid[] =
     15    "$NetBSD: s_cos.c,v 1.7 1995/05/10 20:47:02 jtc Exp $";
     16#endif
     17
     18/* cos(x)
     19 * Return cosine function of x.
     20 *
     21 * kernel function:
     22 *	__kernel_sin		... sine function on [-pi/4,pi/4]
     23 *	__kernel_cos		... cosine function on [-pi/4,pi/4]
     24 *	__ieee754_rem_pio2	... argument reduction routine
     25 *
     26 * Method.
     27 *      Let S,C and T denote the sin, cos and tan respectively on
     28 *	[-PI/4, +PI/4]. Reduce the argument x to y1+y2 = x-k*pi/2
     29 *	in [-pi/4 , +pi/4], and let n = k mod 4.
     30 *	We have
     31 *
     32 *          n        sin(x)      cos(x)        tan(x)
     33 *     ----------------------------------------------------------
     34 *	    0	       S	   C		 T
     35 *	    1	       C	  -S		-1/T
     36 *	    2	      -S	  -C		 T
     37 *	    3	      -C	   S		-1/T
     38 *     ----------------------------------------------------------
     39 *
     40 * Special cases:
     41 *      Let trig be any of sin, cos, or tan.
     42 *      trig(+-INF)  is NaN, with signals;
     43 *      trig(NaN)    is that NaN;
     44 *
     45 * Accuracy:
     46 *	TRIG(x) returns trig(x) nearly rounded
     47 */
     48
     49#include "math_libm.h"
     50#include "math_private.h"
     51
     52libm_hidden_proto(cos)
     53#ifdef __STDC__
     54     double cos(double x)
     55#else
     56     double cos(x)
     57     double x;
     58#endif
     59{
     60    double y[2], z = 0.0;
     61    int32_t n, ix;
     62
     63    /* High word of x. */
     64    GET_HIGH_WORD(ix, x);
     65
     66    /* |x| ~< pi/4 */
     67    ix &= 0x7fffffff;
     68    if (ix <= 0x3fe921fb)
     69        return __kernel_cos(x, z);
     70
     71    /* cos(Inf or NaN) is NaN */
     72    else if (ix >= 0x7ff00000)
     73        return x - x;
     74
     75    /* argument reduction needed */
     76    else {
     77        n = __ieee754_rem_pio2(x, y);
     78        switch (n & 3) {
     79        case 0:
     80            return __kernel_cos(y[0], y[1]);
     81        case 1:
     82            return -__kernel_sin(y[0], y[1], 1);
     83        case 2:
     84            return -__kernel_cos(y[0], y[1]);
     85        default:
     86            return __kernel_sin(y[0], y[1], 1);
     87        }
     88    }
     89}
     90
     91libm_hidden_def(cos)