/* s_atanf.c -- float version of s_atan.c. * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com. */ /* * ==================================================== * 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 <sys/cdefs.h> //__FBSDID("$FreeBSD$"); #include "math_private.h" static const float atanhi[] = { 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 */ }; static const float atanlo[] = { 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 */ }; static const float aT[] = { 3.3333328366e-01, -1.9999158382e-01, 1.4253635705e-01, -1.0648017377e-01, 6.1687607318e-02, }; static const float one = 1.0, huge = 1.0e30; float atanf(float x) { float w,s1,s2,z; int32_t ix,hx,id; GET_FLOAT_WORD(hx,x); ix = hx&0x7fffffff; if(ix>=0x4c800000) { /* if |x| >= 2**26 */ if(ix>0x7f800000) return x+x; /* NaN */ if(hx>0) return atanhi[3]+*(volatile float *)&atanlo[3]; else return -atanhi[3]-*(volatile float *)&atanlo[3]; } if (ix < 0x3ee00000) { /* |x| < 0.4375 */ if (ix < 0x39800000) { /* |x| < 2**-12 */ 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**26 */ 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])); s2 = w*(aT[1]+w*aT[3]); if (id<0) return x - x*(s1+s2); else { z = atanhi[id] - ((x*(s1+s2) - atanlo[id]) - x); return (hx<0)? -z:z; } }