e_acoshf.c (1379B)
1 /* e_acoshf.c -- float version of e_acosh.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 #ifndef lint 17 static char rcsid[] = "$FreeBSD: src/lib/msun/src/e_acoshf.c,v 1.7 2002/05/28 17:03:12 alfred Exp $"; 18 #endif 19 20 #include "math.h" 21 #include "math_private.h" 22 23 static const float 24 one = 1.0, 25 ln2 = 6.9314718246e-01; /* 0x3f317218 */ 26 27 float 28 __ieee754_acoshf(float x) 29 { 30 float t; 31 int32_t hx; 32 GET_FLOAT_WORD(hx,x); 33 if(hx<0x3f800000) { /* x < 1 */ 34 return (x-x)/(x-x); 35 } else if(hx >=0x4d800000) { /* x > 2**28 */ 36 if(hx >=0x7f800000) { /* x is inf of NaN */ 37 return x+x; 38 } else 39 return __ieee754_logf(x)+ln2; /* acosh(huge)=log(2x) */ 40 } else if (hx==0x3f800000) { 41 return 0.0; /* acosh(1) = 0 */ 42 } else if (hx > 0x40000000) { /* 2**28 > x > 2 */ 43 t=x*x; 44 return __ieee754_logf((float)2.0*x-one/(x+__ieee754_sqrtf(t-one))); 45 } else { /* 1<x<2 */ 46 t = x-one; 47 return log1pf(t+__ieee754_sqrtf((float)2.0*t+t*t)); 48 } 49 }