Mercurial > sdl-ios-xcode
diff src/libm/s_sin.c @ 2756:a98604b691c8
Expanded the libm support and put it into a separate directory.
author | Sam Lantinga <slouken@libsdl.org> |
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date | Mon, 15 Sep 2008 06:33:23 +0000 |
parents | |
children | dc1eb82ffdaa |
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--- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/src/libm/s_sin.c Mon Sep 15 06:33:23 2008 +0000 @@ -0,0 +1,90 @@ +/* @(#)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 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)