author | William Roberts <williamr@symbian.org> |
Thu, 22 Jul 2010 16:48:56 +0100 | |
branch | GCC_SURGE |
changeset 45 | 4b03adbd26ca |
parent 0 | e4d67989cc36 |
permissions | -rw-r--r-- |
0
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/*-------------------------------------------------------------------- |
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*© Portions copyright (c) 2006 Nokia Corporation. All rights reserved. |
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*-------------------------------------------------------------------- |
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*/ |
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/* @(#)s_cos.c 5.1 93/09/24 */ |
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/* |
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* ==================================================== |
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* Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. |
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* |
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* Developed at SunPro, a Sun Microsystems, Inc. business. |
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* Permission to use, copy, modify, and distribute this |
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* software is freely granted, provided that this notice |
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* is preserved. |
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* ==================================================== |
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*/ |
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#ifndef __SYMBIAN32__ |
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#ifndef lint |
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static char rcsid[] = "$FreeBSD: src/lib/msun/src/s_cos.c,v 1.9 2003/07/23 04:53:46 peter Exp $"; |
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#endif |
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#endif //__SYMBIAN32__ |
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|
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/* cos(x) |
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* Return cosine function of x. |
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* |
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* kernel function: |
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* __kernel_sin ... sine function on [-pi/4,pi/4] |
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* __kernel_cos ... cosine function on [-pi/4,pi/4] |
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* __ieee754_rem_pio2 ... argument reduction routine |
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* |
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* Method. |
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* Let S,C and T denote the sin, cos and tan respectively on |
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* [-PI/4, +PI/4]. Reduce the argument x to y1+y2 = x-k*pi/2 |
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* in [-pi/4 , +pi/4], and let n = k mod 4. |
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* We have |
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* |
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* n sin(x) cos(x) tan(x) |
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* ---------------------------------------------------------- |
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* 0 S C T |
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* 1 C -S -1/T |
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* 2 -S -C T |
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* 3 -C S -1/T |
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* ---------------------------------------------------------- |
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* |
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* Special cases: |
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* Let trig be any of sin, cos, or tan. |
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* trig(+-INF) is NaN, with signals; |
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* trig(NaN) is that NaN; |
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* |
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* Accuracy: |
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* TRIG(x) returns trig(x) nearly rounded |
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*/ |
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|
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#include <math.h> |
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#include "math_private.h" |
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EXPORT_C double cos(double x) |
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{ |
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double y[2],z=0.0; |
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int32_t n, ix; |
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/* High word of x. */ |
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GET_HIGH_WORD(ix,x); |
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/* |x| ~< pi/4 */ |
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ix &= 0x7fffffff; |
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if(ix <= 0x3fe921fb) return __kernel_cos(x,z); |
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|
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/* cos(Inf or NaN) is NaN */ |
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else if (ix>=0x7ff00000) |
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#ifdef __SYMBIAN32__ |
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return NAN; |
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#else |
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return x-x; |
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#endif //__SYMBIAN32__ |
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|
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/* argument reduction needed */ |
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else { |
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n = __ieee754_rem_pio2(x,y); |
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switch(n&3) { |
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case 0: return __kernel_cos(y[0],y[1]); |
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case 1: return -__kernel_sin(y[0],y[1],1); |
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case 2: return -__kernel_cos(y[0],y[1]); |
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default: |
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return __kernel_sin(y[0],y[1],1); |
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} |
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} |
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} |