1 /* sf_atan.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 17 #include "fdlibm.h" 18 19 #ifdef __STDC__ 20 static const float atanhi[] = { 21 #else 22 static float atanhi[] = { 23 #endif 24 4.6364760399e-01, /* atan(0.5)hi 0x3eed6338 */ 25 7.8539812565e-01, /* atan(1.0)hi 0x3f490fda */ 26 9.8279368877e-01, /* atan(1.5)hi 0x3f7b985e */ 27 1.5707962513e+00, /* atan(inf)hi 0x3fc90fda */ 28 }; 29 30 #ifdef __STDC__ 31 static const float atanlo[] = { 32 #else 33 static float atanlo[] = { 34 #endif 35 5.0121582440e-09, /* atan(0.5)lo 0x31ac3769 */ 36 3.7748947079e-08, /* atan(1.0)lo 0x33222168 */ 37 3.4473217170e-08, /* atan(1.5)lo 0x33140fb4 */ 38 7.5497894159e-08, /* atan(inf)lo 0x33a22168 */ 39 }; 40 41 #ifdef __STDC__ 42 static const float aT[] = { 43 #else 44 static float aT[] = { 45 #endif 46 3.3333334327e-01, /* 0x3eaaaaaa */ 47 -2.0000000298e-01, /* 0xbe4ccccd */ 48 1.4285714924e-01, /* 0x3e124925 */ 49 -1.1111110449e-01, /* 0xbde38e38 */ 50 9.0908870101e-02, /* 0x3dba2e6e */ 51 -7.6918758452e-02, /* 0xbd9d8795 */ 52 6.6610731184e-02, /* 0x3d886b35 */ 53 -5.8335702866e-02, /* 0xbd6ef16b */ 54 4.9768779427e-02, /* 0x3d4bda59 */ 55 -3.6531571299e-02, /* 0xbd15a221 */ 56 1.6285819933e-02, /* 0x3c8569d7 */ 57 }; 58 59 #ifdef __STDC__ 60 static const float 61 #else 62 static float 63 #endif 64 one = 1.0, 65 huge = 1.0e30; 66 67 #ifdef __STDC__ atanf(float x)68 float atanf(float x) 69 #else 70 float atanf(x) 71 float x; 72 #endif 73 { 74 float w,s1,s2,z; 75 __int32_t ix,hx,id; 76 77 GET_FLOAT_WORD(hx,x); 78 ix = hx&0x7fffffff; 79 if(ix>=0x50800000) { /* if |x| >= 2^34 */ 80 if(FLT_UWORD_IS_NAN(ix)) 81 return x+x; /* NaN */ 82 if(hx>0) return atanhi[3]+atanlo[3]; 83 else return -atanhi[3]-atanlo[3]; 84 } if (ix < 0x3ee00000) { /* |x| < 0.4375 */ 85 if (ix < 0x31000000) { /* |x| < 2^-29 */ 86 if(huge+x>one) return x; /* raise inexact */ 87 } 88 id = -1; 89 } else { 90 x = fabsf(x); 91 if (ix < 0x3f980000) { /* |x| < 1.1875 */ 92 if (ix < 0x3f300000) { /* 7/16 <=|x|<11/16 */ 93 id = 0; x = ((float)2.0*x-one)/((float)2.0+x); 94 } else { /* 11/16<=|x|< 19/16 */ 95 id = 1; x = (x-one)/(x+one); 96 } 97 } else { 98 if (ix < 0x401c0000) { /* |x| < 2.4375 */ 99 id = 2; x = (x-(float)1.5)/(one+(float)1.5*x); 100 } else { /* 2.4375 <= |x| < 2^66 */ 101 id = 3; x = -(float)1.0/x; 102 } 103 }} 104 /* end of argument reduction */ 105 z = x*x; 106 w = z*z; 107 /* break sum from i=0 to 10 aT[i]z**(i+1) into odd and even poly */ 108 s1 = z*(aT[0]+w*(aT[2]+w*(aT[4]+w*(aT[6]+w*(aT[8]+w*aT[10]))))); 109 s2 = w*(aT[1]+w*(aT[3]+w*(aT[5]+w*(aT[7]+w*aT[9])))); 110 if (id<0) return x - x*(s1+s2); 111 else { 112 z = atanhi[id] - ((x*(s1+s2) - atanlo[id]) - x); 113 return (hx<0)? -z:z; 114 } 115 } 116 117 #ifdef _DOUBLE_IS_32BITS 118 119 #ifdef __STDC__ atan(double x)120 double atan(double x) 121 #else 122 double atan(x) 123 double x; 124 #endif 125 { 126 return (double) atanf((float) x); 127 } 128 129 #endif /* defined(_DOUBLE_IS_32BITS) */ 130