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lightning-sunbird  0.9+nobinonly
s_sin.c
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00001 /* -*- Mode: C; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
00002  *
00003  * ***** BEGIN LICENSE BLOCK *****
00004  * Version: MPL 1.1/GPL 2.0/LGPL 2.1
00005  *
00006  * The contents of this file are subject to the Mozilla Public License Version
00007  * 1.1 (the "License"); you may not use this file except in compliance with
00008  * the License. You may obtain a copy of the License at
00009  * http://www.mozilla.org/MPL/
00010  *
00011  * Software distributed under the License is distributed on an "AS IS" basis,
00012  * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
00013  * for the specific language governing rights and limitations under the
00014  * License.
00015  *
00016  * The Original Code is Mozilla Communicator client code, released
00017  * March 31, 1998.
00018  *
00019  * The Initial Developer of the Original Code is
00020  * Sun Microsystems, Inc.
00021  * Portions created by the Initial Developer are Copyright (C) 1998
00022  * the Initial Developer. All Rights Reserved.
00023  *
00024  * Contributor(s):
00025  *
00026  * Alternatively, the contents of this file may be used under the terms of
00027  * either of the GNU General Public License Version 2 or later (the "GPL"),
00028  * or the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
00029  * in which case the provisions of the GPL or the LGPL are applicable instead
00030  * of those above. If you wish to allow use of your version of this file only
00031  * under the terms of either the GPL or the LGPL, and not to allow others to
00032  * use your version of this file under the terms of the MPL, indicate your
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00034  * and other provisions required by the GPL or the LGPL. If you do not delete
00035  * the provisions above, a recipient may use your version of this file under
00036  * the terms of any one of the MPL, the GPL or the LGPL.
00037  *
00038  * ***** END LICENSE BLOCK ***** */
00039 
00040 /* @(#)s_sin.c 1.3 95/01/18 */
00041 /*
00042  * ====================================================
00043  * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
00044  *
00045  * Developed at SunSoft, a Sun Microsystems, Inc. business.
00046  * Permission to use, copy, modify, and distribute this
00047  * software is freely granted, provided that this notice 
00048  * is preserved.
00049  * ====================================================
00050  */
00051 
00052 /* sin(x)
00053  * Return sine function of x.
00054  *
00055  * kernel function:
00056  *     __kernel_sin         ... sine function on [-pi/4,pi/4]
00057  *     __kernel_cos         ... cose function on [-pi/4,pi/4]
00058  *     __ieee754_rem_pio2   ... argument reduction routine
00059  *
00060  * Method.
00061  *      Let S,C and T denote the sin, cos and tan respectively on 
00062  *     [-PI/4, +PI/4]. Reduce the argument x to y1+y2 = x-k*pi/2 
00063  *     in [-pi/4 , +pi/4], and let n = k mod 4.
00064  *     We have
00065  *
00066  *          n        sin(x)      cos(x)        tan(x)
00067  *     ----------------------------------------------------------
00068  *         0         S         C           T
00069  *         1         C        -S          -1/T
00070  *         2        -S        -C           T
00071  *         3        -C         S          -1/T
00072  *     ----------------------------------------------------------
00073  *
00074  * Special cases:
00075  *      Let trig be any of sin, cos, or tan.
00076  *      trig(+-INF)  is NaN, with signals;
00077  *      trig(NaN)    is that NaN;
00078  *
00079  * Accuracy:
00080  *     TRIG(x) returns trig(x) nearly rounded 
00081  */
00082 
00083 #include "fdlibm.h"
00084 
00085 #ifdef __STDC__
00086        double fd_sin(double x)
00087 #else
00088        double fd_sin(x)
00089        double x;
00090 #endif
00091 {
00092         fd_twoints u;
00093        double y[2],z=0.0;
00094        int n, ix;
00095 
00096     /* High word of x. */
00097         u.d = x;
00098        ix = __HI(u);
00099 
00100     /* |x| ~< pi/4 */
00101        ix &= 0x7fffffff;
00102        if(ix <= 0x3fe921fb) return __kernel_sin(x,z,0);
00103 
00104     /* sin(Inf or NaN) is NaN */
00105        else if (ix>=0x7ff00000) return x-x;
00106 
00107     /* argument reduction needed */
00108        else {
00109            n = __ieee754_rem_pio2(x,y);
00110            switch(n&3) {
00111               case 0: return  __kernel_sin(y[0],y[1],1);
00112               case 1: return  __kernel_cos(y[0],y[1]);
00113               case 2: return -__kernel_sin(y[0],y[1],1);
00114               default:
00115                      return -__kernel_cos(y[0],y[1]);
00116            }
00117        }
00118 }