1 /* s_atanf.c -- float version of s_atan.c.
2 * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com.
6 * ====================================================
7 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
9 * Developed at SunPro, a Sun Microsystems, Inc. business.
10 * Permission to use, copy, modify, and distribute this
11 * software is freely granted, provided that this notice
13 * ====================================================
17 static char rcsid[] = "$FreeBSD$";
21 #include "math_private.h"
24 static const float atanhi[] = {
26 static float atanhi[] = {
28 4.6364760399e-01, /* atan(0.5)hi 0x3eed6338 */
29 7.8539812565e-01, /* atan(1.0)hi 0x3f490fda */
30 9.8279368877e-01, /* atan(1.5)hi 0x3f7b985e */
31 1.5707962513e+00, /* atan(inf)hi 0x3fc90fda */
35 static const float atanlo[] = {
37 static float atanlo[] = {
39 5.0121582440e-09, /* atan(0.5)lo 0x31ac3769 */
40 3.7748947079e-08, /* atan(1.0)lo 0x33222168 */
41 3.4473217170e-08, /* atan(1.5)lo 0x33140fb4 */
42 7.5497894159e-08, /* atan(inf)lo 0x33a22168 */
46 static const float aT[] = {
50 3.3333334327e-01, /* 0x3eaaaaaa */
51 -2.0000000298e-01, /* 0xbe4ccccd */
52 1.4285714924e-01, /* 0x3e124925 */
53 -1.1111110449e-01, /* 0xbde38e38 */
54 9.0908870101e-02, /* 0x3dba2e6e */
55 -7.6918758452e-02, /* 0xbd9d8795 */
56 6.6610731184e-02, /* 0x3d886b35 */
57 -5.8335702866e-02, /* 0xbd6ef16b */
58 4.9768779427e-02, /* 0x3d4bda59 */
59 -3.6531571299e-02, /* 0xbd15a221 */
60 1.6285819933e-02, /* 0x3c8569d7 */
83 if(ix>=0x50800000) { /* if |x| >= 2^34 */
86 if(hx>0) return atanhi[3]+atanlo[3];
87 else return -atanhi[3]-atanlo[3];
88 } if (ix < 0x3ee00000) { /* |x| < 0.4375 */
89 if (ix < 0x31000000) { /* |x| < 2^-29 */
90 if(huge+x>one) return x; /* raise inexact */
95 if (ix < 0x3f980000) { /* |x| < 1.1875 */
96 if (ix < 0x3f300000) { /* 7/16 <=|x|<11/16 */
97 id = 0; x = ((float)2.0*x-one)/((float)2.0+x);
98 } else { /* 11/16<=|x|< 19/16 */
99 id = 1; x = (x-one)/(x+one);
102 if (ix < 0x401c0000) { /* |x| < 2.4375 */
103 id = 2; x = (x-(float)1.5)/(one+(float)1.5*x);
104 } else { /* 2.4375 <= |x| < 2^66 */
105 id = 3; x = -(float)1.0/x;
108 /* end of argument reduction */
111 /* break sum from i=0 to 10 aT[i]z**(i+1) into odd and even poly */
112 s1 = z*(aT[0]+w*(aT[2]+w*(aT[4]+w*(aT[6]+w*(aT[8]+w*aT[10])))));
113 s2 = w*(aT[1]+w*(aT[3]+w*(aT[5]+w*(aT[7]+w*aT[9]))));
114 if (id<0) return x - x*(s1+s2);
116 z = atanhi[id] - ((x*(s1+s2) - atanlo[id]) - x);