1 /* s_atanf.c -- float version of s_atan.c. 2 * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com. 3 */ 4 5 /* 6 * ==================================================== 7 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. 8 * 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 12 * is preserved. 13 * ==================================================== 14 */ 15 16 #include <sys/cdefs.h> 17 #if defined(LIBM_SCCS) && !defined(lint) 18 __RCSID("$NetBSD: s_atanf.c,v 1.5 1997/10/09 11:31:02 lukem Exp $"); 19 #endif 20 21 #include "math.h" 22 #include "math_private.h" 23 24 #ifdef __STDC__ 25 static const float atanhi[] = { 26 #else 27 static float atanhi[] = { 28 #endif 29 4.6364760399e-01, /* atan(0.5)hi 0x3eed6338 */ 30 7.8539812565e-01, /* atan(1.0)hi 0x3f490fda */ 31 9.8279368877e-01, /* atan(1.5)hi 0x3f7b985e */ 32 1.5707962513e+00, /* atan(inf)hi 0x3fc90fda */ 33 }; 34 35 #ifdef __STDC__ 36 static const float atanlo[] = { 37 #else 38 static float atanlo[] = { 39 #endif 40 5.0121582440e-09, /* atan(0.5)lo 0x31ac3769 */ 41 3.7748947079e-08, /* atan(1.0)lo 0x33222168 */ 42 3.4473217170e-08, /* atan(1.5)lo 0x33140fb4 */ 43 7.5497894159e-08, /* atan(inf)lo 0x33a22168 */ 44 }; 45 46 #ifdef __STDC__ 47 static const float aT[] = { 48 #else 49 static float aT[] = { 50 #endif 51 3.3333334327e-01, /* 0x3eaaaaaa */ 52 -2.0000000298e-01, /* 0xbe4ccccd */ 53 1.4285714924e-01, /* 0x3e124925 */ 54 -1.1111110449e-01, /* 0xbde38e38 */ 55 9.0908870101e-02, /* 0x3dba2e6e */ 56 -7.6918758452e-02, /* 0xbd9d8795 */ 57 6.6610731184e-02, /* 0x3d886b35 */ 58 -5.8335702866e-02, /* 0xbd6ef16b */ 59 4.9768779427e-02, /* 0x3d4bda59 */ 60 -3.6531571299e-02, /* 0xbd15a221 */ 61 1.6285819933e-02, /* 0x3c8569d7 */ 62 }; 63 64 #ifdef __STDC__ 65 static const float 66 #else 67 static float 68 #endif 69 one = 1.0, 70 huge = 1.0e30; 71 72 #ifdef __STDC__ 73 float atanf(float x) 74 #else 75 float atanf(x) 76 float x; 77 #endif 78 { 79 float w,s1,s2,z; 80 int32_t ix,hx,id; 81 82 GET_FLOAT_WORD(hx,x); 83 ix = hx&0x7fffffff; 84 if(ix>=0x50800000) { /* if |x| >= 2^34 */ 85 if(ix>0x7f800000) 86 return x+x; /* NaN */ 87 if(hx>0) return atanhi[3]+atanlo[3]; 88 else return -atanhi[3]-atanlo[3]; 89 } if (ix < 0x3ee00000) { /* |x| < 0.4375 */ 90 if (ix < 0x31000000) { /* |x| < 2^-29 */ 91 if(huge+x>one) return x; /* raise inexact */ 92 } 93 id = -1; 94 } else { 95 x = fabsf(x); 96 if (ix < 0x3f980000) { /* |x| < 1.1875 */ 97 if (ix < 0x3f300000) { /* 7/16 <=|x|<11/16 */ 98 id = 0; x = ((float)2.0*x-one)/((float)2.0+x); 99 } else { /* 11/16<=|x|< 19/16 */ 100 id = 1; x = (x-one)/(x+one); 101 } 102 } else { 103 if (ix < 0x401c0000) { /* |x| < 2.4375 */ 104 id = 2; x = (x-(float)1.5)/(one+(float)1.5*x); 105 } else { /* 2.4375 <= |x| < 2^66 */ 106 id = 3; x = -(float)1.0/x; 107 } 108 }} 109 /* end of argument reduction */ 110 z = x*x; 111 w = z*z; 112 /* break sum from i=0 to 10 aT[i]z**(i+1) into odd and even poly */ 113 s1 = z*(aT[0]+w*(aT[2]+w*(aT[4]+w*(aT[6]+w*(aT[8]+w*aT[10]))))); 114 s2 = w*(aT[1]+w*(aT[3]+w*(aT[5]+w*(aT[7]+w*aT[9])))); 115 if (id<0) return x - x*(s1+s2); 116 else { 117 z = atanhi[id] - ((x*(s1+s2) - atanlo[id]) - x); 118 return (hx<0)? -z:z; 119 } 120 } 121