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 #include <sys/cdefs.h> 17 #if defined(LIBM_SCCS) && !defined(lint) 18 __RCSID("$NetBSD: e_acoshf.c,v 1.8 2002/05/26 22:01:48 wiz Exp $"); 19 #endif 20 21 #include "math.h" 22 #include "math_private.h" 23 24 static const float 25 one = 1.0, 26 ln2 = 6.9314718246e-01; /* 0x3f317218 */ 27 28 float 29 __ieee754_acoshf(float x) 30 { 31 float t; 32 int32_t hx; 33 GET_FLOAT_WORD(hx,x); 34 if(hx<0x3f800000) { /* x < 1 */ 35 return (x-x)/(x-x); 36 } else if(hx >=0x4d800000) { /* x > 2**28 */ 37 if(hx >=0x7f800000) { /* x is inf of NaN */ 38 return x+x; 39 } else 40 return __ieee754_logf(x)+ln2; /* acosh(huge)=log(2x) */ 41 } else if (hx==0x3f800000) { 42 return 0.0; /* acosh(1) = 0 */ 43 } else if (hx > 0x40000000) { /* 2**28 > x > 2 */ 44 t=x*x; 45 return __ieee754_logf((float)2.0*x-one/(x+__ieee754_sqrtf(t-one))); 46 } else { /* 1<x<2 */ 47 t = x-one; 48 return log1pf(t+sqrtf((float)2.0*t+t*t)); 49 } 50 } 51