/[jscoverage]/trunk/js/src/fdlibm/e_atan2.c
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Contents of /trunk/js/src/fdlibm/e_atan2.c

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Wed Aug 1 13:51:53 2007 UTC (12 years, 10 months ago) by siliconforks
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Initial import.

1 /* -*- Mode: C; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
2 *
3 * ***** BEGIN LICENSE BLOCK *****
4 * Version: MPL 1.1/GPL 2.0/LGPL 2.1
5 *
6 * The contents of this file are subject to the Mozilla Public License Version
7 * 1.1 (the "License"); you may not use this file except in compliance with
8 * the License. You may obtain a copy of the License at
9 * http://www.mozilla.org/MPL/
10 *
11 * Software distributed under the License is distributed on an "AS IS" basis,
12 * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
13 * for the specific language governing rights and limitations under the
14 * License.
15 *
16 * The Original Code is Mozilla Communicator client code, released
17 * March 31, 1998.
18 *
19 * The Initial Developer of the Original Code is
20 * Sun Microsystems, Inc.
21 * Portions created by the Initial Developer are Copyright (C) 1998
22 * the Initial Developer. All Rights Reserved.
23 *
24 * Contributor(s):
25 *
26 * Alternatively, the contents of this file may be used under the terms of
27 * either of the GNU General Public License Version 2 or later (the "GPL"),
28 * or the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
29 * in which case the provisions of the GPL or the LGPL are applicable instead
30 * of those above. If you wish to allow use of your version of this file only
31 * under the terms of either the GPL or the LGPL, and not to allow others to
32 * use your version of this file under the terms of the MPL, indicate your
33 * decision by deleting the provisions above and replace them with the notice
34 * and other provisions required by the GPL or the LGPL. If you do not delete
35 * the provisions above, a recipient may use your version of this file under
36 * the terms of any one of the MPL, the GPL or the LGPL.
37 *
38 * ***** END LICENSE BLOCK ***** */
39
40 /* @(#)e_atan2.c 1.3 95/01/18 */
41 /*
42 * ====================================================
43 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
44 *
45 * Developed at SunSoft, a Sun Microsystems, Inc. business.
46 * Permission to use, copy, modify, and distribute this
47 * software is freely granted, provided that this notice
48 * is preserved.
49 * ====================================================
50 *
51 */
52
53 /* __ieee754_atan2(y,x)
54 * Method :
55 * 1. Reduce y to positive by atan2(y,x)=-atan2(-y,x).
56 * 2. Reduce x to positive by (if x and y are unexceptional):
57 * ARG (x+iy) = arctan(y/x) ... if x > 0,
58 * ARG (x+iy) = pi - arctan[y/(-x)] ... if x < 0,
59 *
60 * Special cases:
61 *
62 * ATAN2((anything), NaN ) is NaN;
63 * ATAN2(NAN , (anything) ) is NaN;
64 * ATAN2(+-0, +(anything but NaN)) is +-0 ;
65 * ATAN2(+-0, -(anything but NaN)) is +-pi ;
66 * ATAN2(+-(anything but 0 and NaN), 0) is +-pi/2;
67 * ATAN2(+-(anything but INF and NaN), +INF) is +-0 ;
68 * ATAN2(+-(anything but INF and NaN), -INF) is +-pi;
69 * ATAN2(+-INF,+INF ) is +-pi/4 ;
70 * ATAN2(+-INF,-INF ) is +-3pi/4;
71 * ATAN2(+-INF, (anything but,0,NaN, and INF)) is +-pi/2;
72 *
73 * Constants:
74 * The hexadecimal values are the intended ones for the following
75 * constants. The decimal values may be used, provided that the
76 * compiler will convert from decimal to binary accurately enough
77 * to produce the hexadecimal values shown.
78 */
79
80 #include "fdlibm.h"
81
82 #ifdef __STDC__
83 static const double
84 #else
85 static double
86 #endif
87 tiny = 1.0e-300,
88 zero = 0.0,
89 pi_o_4 = 7.8539816339744827900E-01, /* 0x3FE921FB, 0x54442D18 */
90 pi_o_2 = 1.5707963267948965580E+00, /* 0x3FF921FB, 0x54442D18 */
91 pi = 3.1415926535897931160E+00, /* 0x400921FB, 0x54442D18 */
92 pi_lo = 1.2246467991473531772E-16; /* 0x3CA1A626, 0x33145C07 */
93
94 #ifdef __STDC__
95 double __ieee754_atan2(double y, double x)
96 #else
97 double __ieee754_atan2(y,x)
98 double y,x;
99 #endif
100 {
101 fd_twoints ux, uy, uz;
102 double z;
103 int k,m,hx,hy,ix,iy;
104 unsigned lx,ly;
105
106 ux.d = x; uy.d = y;
107 hx = __HI(ux); ix = hx&0x7fffffff;
108 lx = __LO(ux);
109 hy = __HI(uy); iy = hy&0x7fffffff;
110 ly = __LO(uy);
111 if(((ix|((lx|-(int)lx)>>31))>0x7ff00000)||
112 ((iy|((ly|-(int)ly)>>31))>0x7ff00000)) /* x or y is NaN */
113 return x+y;
114 if(((hx-0x3ff00000)|lx)==0) return fd_atan(y); /* x=1.0 */
115 m = ((hy>>31)&1)|((hx>>30)&2); /* 2*sign(x)+sign(y) */
116
117 /* when y = 0 */
118 if((iy|ly)==0) {
119 switch(m) {
120 case 0:
121 case 1: return y; /* atan(+-0,+anything)=+-0 */
122 case 2: return pi+tiny;/* atan(+0,-anything) = pi */
123 case 3: return -pi-tiny;/* atan(-0,-anything) =-pi */
124 }
125 }
126 /* when x = 0 */
127 if((ix|lx)==0) return (hy<0)? -pi_o_2-tiny: pi_o_2+tiny;
128
129 /* when x is INF */
130 if(ix==0x7ff00000) {
131 if(iy==0x7ff00000) {
132 switch(m) {
133 case 0: return pi_o_4+tiny;/* atan(+INF,+INF) */
134 case 1: return -pi_o_4-tiny;/* atan(-INF,+INF) */
135 case 2: return 3.0*pi_o_4+tiny;/*atan(+INF,-INF)*/
136 case 3: return -3.0*pi_o_4-tiny;/*atan(-INF,-INF)*/
137 }
138 } else {
139 switch(m) {
140 case 0: return zero ; /* atan(+...,+INF) */
141 case 1: return -zero ; /* atan(-...,+INF) */
142 case 2: return pi+tiny ; /* atan(+...,-INF) */
143 case 3: return -pi-tiny ; /* atan(-...,-INF) */
144 }
145 }
146 }
147 /* when y is INF */
148 if(iy==0x7ff00000) return (hy<0)? -pi_o_2-tiny: pi_o_2+tiny;
149
150 /* compute y/x */
151 k = (iy-ix)>>20;
152 if(k > 60) z=pi_o_2+0.5*pi_lo; /* |y/x| > 2**60 */
153 else if(hx<0&&k<-60) z=0.0; /* |y|/x < -2**60 */
154 else z=fd_atan(fd_fabs(y/x)); /* safe to do y/x */
155 switch (m) {
156 case 0: return z ; /* atan(+,+) */
157 case 1: uz.d = z;
158 __HI(uz) ^= 0x80000000;
159 z = uz.d;
160 return z ; /* atan(-,+) */
161 case 2: return pi-(z-pi_lo);/* atan(+,-) */
162 default: /* case 3 */
163 return (z-pi_lo)-pi;/* atan(-,-) */
164 }
165 }

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