view src/libm/s_sin.c @ 5133:ec13e48ee0d9

Fixed bug #1112 (retina display support) Vittorio Giovara 2011-02-01 02:21:50 PST with the attached patch, the opengles context will always use the maximum screensize available; this is particularly useful for supporting retina display on latest iphone. please note: Apple documentation warns that using the "upscaled" gl context actually uses more memory and bandwitdh, so it might be worth to let the user decide whether to disable it or not, either with a flag or a sdl function...
author Sam Lantinga <slouken@libsdl.org>
date Tue, 01 Feb 2011 08:54:34 -0800
parents dc1eb82ffdaa
children
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/* @(#)s_sin.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_sin.c,v 1.7 1995/05/10 20:48:15 jtc Exp $";
#endif

/* sin(x)
 * Return sine function of x.
 *
 * kernel function:
 *	__kernel_sin		... sine function on [-pi/4,pi/4]
 *	__kernel_cos		... cose 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(sin)
#ifdef __STDC__
     double sin(double x)
#else
     double sin(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_sin(x, z, 0);

    /* sin(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_sin(y[0], y[1], 1);
        case 1:
            return __kernel_cos(y[0], y[1]);
        case 2:
            return -__kernel_sin(y[0], y[1], 1);
        default:
            return -__kernel_cos(y[0], y[1]);
        }
    }
}

libm_hidden_def(sin)