| /* e_asinf.c -- float version of e_asin.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 "math.h" |
| #include "math_private.h" |
| |
| static const float |
| one = 1.0000000000e+00, /* 0x3F800000 */ |
| huge = 1.000e+30; |
| |
| /* |
| * The coefficients for the rational approximation were generated over |
| * 0x1p-12f <= x <= 0.5f. The maximum error satisfies log2(e) < -30.084. |
| */ |
| static const float |
| pS0 = 1.66666672e-01f, /* 0x3e2aaaab */ |
| pS1 = -1.19510300e-01f, /* 0xbdf4c1d1 */ |
| pS2 = 5.47002675e-03f, /* 0x3bb33de9 */ |
| qS1 = -1.16706085e+00f, /* 0xbf956240 */ |
| qS2 = 2.90115148e-01f; /* 0x3e9489f9 */ |
| |
| static const double |
| pio2 = 1.570796326794896558e+00; |
| |
| float |
| asinf(float x) |
| { |
| double s; |
| float t,w,p,q; |
| int32_t hx,ix; |
| GET_FLOAT_WORD(hx,x); |
| ix = hx&0x7fffffff; |
| if(ix>=0x3f800000) { /* |x| >= 1 */ |
| if(ix==0x3f800000) /* |x| == 1 */ |
| return x*pio2; /* asin(+-1) = +-pi/2 with inexact */ |
| return (x-x)/(x-x); /* asin(|x|>1) is NaN */ |
| } else if (ix<0x3f000000) { /* |x|<0.5 */ |
| if(ix<0x39800000) { /* |x| < 2**-12 */ |
| if(huge+x>one) return x;/* return x with inexact if x!=0*/ |
| } |
| t = x*x; |
| p = t*(pS0+t*(pS1+t*pS2)); |
| q = one+t*(qS1+t*qS2); |
| w = p/q; |
| return x+x*w; |
| } |
| /* 1> |x|>= 0.5 */ |
| w = one-fabsf(x); |
| t = w*(float)0.5; |
| p = t*(pS0+t*(pS1+t*pS2)); |
| q = one+t*(qS1+t*qS2); |
| s = sqrt(t); |
| w = p/q; |
| t = pio2-2.0*(s+s*w); |
| if(hx>0) return t; else return -t; |
| } |