1 /* ef_acosh.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 17 #include "fdlibm.h" 18 19 #ifdef __STDC__ 20 static const float 21 #else 22 static float 23 #endif 24 one = 1.0, 25 ln2 = 6.9314718246e-01; /* 0x3f317218 */ 26 27 #ifdef __STDC__ __ieee754_acoshf(float x)28 float __ieee754_acoshf(float x) 29 #else 30 float __ieee754_acoshf(x) 31 float x; 32 #endif 33 { 34 float t; 35 __int32_t hx; 36 GET_FLOAT_WORD(hx,x); 37 if(hx<0x3f800000) { /* x < 1 */ 38 return (x-x)/(x-x); 39 } else if(hx >=0x4d800000) { /* x > 2**28 */ 40 if(!FLT_UWORD_IS_FINITE(hx)) { /* x is inf of NaN */ 41 return x+x; 42 } else 43 return __ieee754_logf(x)+ln2; /* acosh(huge)=log(2x) */ 44 } else if (hx==0x3f800000) { 45 return 0.0; /* acosh(1) = 0 */ 46 } else if (hx > 0x40000000) { /* 2**28 > x > 2 */ 47 t=x*x; 48 return __ieee754_logf((float)2.0*x-one/(x+__ieee754_sqrtf(t-one))); 49 } else { /* 1<x<2 */ 50 t = x-one; 51 return log1pf(t+__ieee754_sqrtf((float)2.0*t+t*t)); 52 } 53 } 54