| /* sf_atan.c -- float version of s_atan.c. |
| * Conversion to float by Ian Lance Taylor, Cygnus Support, [email protected]. |
| */ |
| |
| /* |
| * ==================================================== |
| * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. |
| * |
| * Developed at SunPro, a Sun Microsystems, Inc. business. |
| * Permission to use, copy, modify, and distribute this |
| * software is freely granted, provided that this notice |
| * is preserved. |
| * ==================================================== |
| * |
| */ |
| |
| #include "fdlibm.h" |
| |
| #ifdef __STDC__ |
| static const float atanhi[] = { |
| #else |
| static float atanhi[] = { |
| #endif |
| 4.6364760399e-01, /* atan(0.5)hi 0x3eed6338 */ |
| 7.8539812565e-01, /* atan(1.0)hi 0x3f490fda */ |
| 9.8279368877e-01, /* atan(1.5)hi 0x3f7b985e */ |
| 1.5707962513e+00, /* atan(inf)hi 0x3fc90fda */ |
| }; |
| |
| #ifdef __STDC__ |
| static const float atanlo[] = { |
| #else |
| static float atanlo[] = { |
| #endif |
| 5.0121582440e-09, /* atan(0.5)lo 0x31ac3769 */ |
| 3.7748947079e-08, /* atan(1.0)lo 0x33222168 */ |
| 3.4473217170e-08, /* atan(1.5)lo 0x33140fb4 */ |
| 7.5497894159e-08, /* atan(inf)lo 0x33a22168 */ |
| }; |
| |
| #ifdef __STDC__ |
| static const float aT[] = { |
| #else |
| static float aT[] = { |
| #endif |
| 3.3333334327e-01, /* 0x3eaaaaaa */ |
| -2.0000000298e-01, /* 0xbe4ccccd */ |
| 1.4285714924e-01, /* 0x3e124925 */ |
| -1.1111110449e-01, /* 0xbde38e38 */ |
| 9.0908870101e-02, /* 0x3dba2e6e */ |
| -7.6918758452e-02, /* 0xbd9d8795 */ |
| 6.6610731184e-02, /* 0x3d886b35 */ |
| -5.8335702866e-02, /* 0xbd6ef16b */ |
| 4.9768779427e-02, /* 0x3d4bda59 */ |
| -3.6531571299e-02, /* 0xbd15a221 */ |
| 1.6285819933e-02, /* 0x3c8569d7 */ |
| }; |
| |
| #ifdef __STDC__ |
| static const float |
| #else |
| static float |
| #endif |
| one = 1.0, |
| huge = 1.0e30; |
| |
| #ifdef __STDC__ |
| float atanf(float x) |
| #else |
| float atanf(x) |
| float x; |
| #endif |
| { |
| float w,s1,s2,z; |
| __int32_t ix,hx,id; |
| |
| GET_FLOAT_WORD(hx,x); |
| ix = hx&0x7fffffff; |
| if(ix>=0x50800000) { /* if |x| >= 2^34 */ |
| if(FLT_UWORD_IS_NAN(ix)) |
| return x+x; /* NaN */ |
| if(hx>0) return atanhi[3]+atanlo[3]; |
| else return -atanhi[3]-atanlo[3]; |
| } if (ix < 0x3ee00000) { /* |x| < 0.4375 */ |
| if (ix < 0x31000000) { /* |x| < 2^-29 */ |
| if(huge+x>one) return x; /* raise inexact */ |
| } |
| id = -1; |
| } else { |
| x = fabsf(x); |
| if (ix < 0x3f980000) { /* |x| < 1.1875 */ |
| if (ix < 0x3f300000) { /* 7/16 <=|x|<11/16 */ |
| id = 0; x = ((float)2.0*x-one)/((float)2.0+x); |
| } else { /* 11/16<=|x|< 19/16 */ |
| id = 1; x = (x-one)/(x+one); |
| } |
| } else { |
| if (ix < 0x401c0000) { /* |x| < 2.4375 */ |
| id = 2; x = (x-(float)1.5)/(one+(float)1.5*x); |
| } else { /* 2.4375 <= |x| < 2^66 */ |
| id = 3; x = -(float)1.0/x; |
| } |
| }} |
| /* end of argument reduction */ |
| z = x*x; |
| w = z*z; |
| /* break sum from i=0 to 10 aT[i]z**(i+1) into odd and even poly */ |
| s1 = z*(aT[0]+w*(aT[2]+w*(aT[4]+w*(aT[6]+w*(aT[8]+w*aT[10]))))); |
| s2 = w*(aT[1]+w*(aT[3]+w*(aT[5]+w*(aT[7]+w*aT[9])))); |
| if (id<0) return x - x*(s1+s2); |
| else { |
| z = atanhi[id] - ((x*(s1+s2) - atanlo[id]) - x); |
| return (hx<0)? -z:z; |
| } |
| } |
| |
| #ifdef _DOUBLE_IS_32BITS |
| |
| #ifdef __STDC__ |
| double atan(double x) |
| #else |
| double atan(x) |
| double x; |
| #endif |
| { |
| return (double) atanf((float) x); |
| } |
| |
| #endif /* defined(_DOUBLE_IS_32BITS) */ |
