view src/libm/s_cos.c @ 4805:de3b3455f8ec

Put the render loop back in its right place, but with delaying functionality to keep it down to roughly 60fps, not eating up all the X11 time.
author Eli Gottlieb <eligottlieb@gmail.com>
date Mon, 19 Jul 2010 00:24:02 -0400
parents dc1eb82ffdaa
children
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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.
 * ====================================================
 */

#if defined(LIBM_SCCS) && !defined(lint)
static const char rcsid[] =
    "$NetBSD: s_cos.c,v 1.7 1995/05/10 20:47:02 jtc Exp $";
#endif

/* 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 "math.h"
#include "math_private.h"

libm_hidden_proto(cos)
#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);
        }
    }
}

libm_hidden_def(cos)