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 * ====================================================
15 * $FreeBSD: head/lib/msun/src/s_atanf.c 181100 2008-08-01 01:24:25Z das $
19 #include "math_private.h"
21 static const float atanhi[] = {
22 4.6364760399e-01, /* atan(0.5)hi 0x3eed6338 */
23 7.8539812565e-01, /* atan(1.0)hi 0x3f490fda */
24 9.8279368877e-01, /* atan(1.5)hi 0x3f7b985e */
25 1.5707962513e+00, /* atan(inf)hi 0x3fc90fda */
28 static const float atanlo[] = {
29 5.0121582440e-09, /* atan(0.5)lo 0x31ac3769 */
30 3.7748947079e-08, /* atan(1.0)lo 0x33222168 */
31 3.4473217170e-08, /* atan(1.5)lo 0x33140fb4 */
32 7.5497894159e-08, /* atan(inf)lo 0x33a22168 */
35 static const float aT[] = {
55 if(ix>=0x4c800000) { /* if |x| >= 2**26 */
58 if(hx>0) return atanhi[3]+*(volatile float *)&atanlo[3];
59 else return -atanhi[3]-*(volatile float *)&atanlo[3];
60 } if (ix < 0x3ee00000) { /* |x| < 0.4375 */
61 if (ix < 0x39800000) { /* |x| < 2**-12 */
62 if(huge+x>one) return x; /* raise inexact */
67 if (ix < 0x3f980000) { /* |x| < 1.1875 */
68 if (ix < 0x3f300000) { /* 7/16 <=|x|<11/16 */
69 id = 0; x = ((float)2.0*x-one)/((float)2.0+x);
70 } else { /* 11/16<=|x|< 19/16 */
71 id = 1; x = (x-one)/(x+one);
74 if (ix < 0x401c0000) { /* |x| < 2.4375 */
75 id = 2; x = (x-(float)1.5)/(one+(float)1.5*x);
76 } else { /* 2.4375 <= |x| < 2**26 */
77 id = 3; x = -(float)1.0/x;
80 /* end of argument reduction */
83 /* break sum from i=0 to 10 aT[i]z**(i+1) into odd and even poly */
84 s1 = z*(aT[0]+w*(aT[2]+w*aT[4]));
85 s2 = w*(aT[1]+w*aT[3]);
86 if (id<0) return x - x*(s1+s2);
88 z = atanhi[id] - ((x*(s1+s2) - atanlo[id]) - x);