1 /* e_coshf.c -- float version of e_cosh.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 #if defined(LIBM_SCCS) && !defined(lint) 17 static char rcsid[] = "$NetBSD: e_coshf.c,v 1.5 1995/05/10 20:45:01 jtc Exp $"; 18 #endif 19 20 #include "math.h" 21 #include "math_private.h" 22 23 #ifdef __STDC__ 24 static const volatile float huge = 1.0e30; 25 static const float one = 1.0, half=0.5; 26 #else 27 static float one = 1.0, half=0.5, huge = 1.0e30; 28 #endif 29 30 #ifdef __STDC__ 31 float __ieee754_coshf(float x) 32 #else 33 float __ieee754_coshf(x) 34 float x; 35 #endif 36 { 37 float t,w; 38 int32_t ix; 39 40 GET_FLOAT_WORD(ix,x); 41 ix &= 0x7fffffff; 42 43 /* x is INF or NaN */ 44 if(ix>=0x7f800000) return x*x; 45 46 /* |x| in [0,0.5*ln2], return 1+expm1(|x|)^2/(2*exp(|x|)) */ 47 if(ix<0x3eb17218) { 48 t = expm1f(fabsf(x)); 49 w = one+t; 50 if (ix<0x24000000) return w; /* cosh(tiny) = 1 */ 51 return one+(t*t)/(w+w); 52 } 53 54 /* |x| in [0.5*ln2,22], return (exp(|x|)+1/exp(|x|)/2; */ 55 if (ix < 0x41b00000) { 56 t = __ieee754_expf(fabsf(x)); 57 return half*t+half/t; 58 } 59 60 /* |x| in [22, log(maxdouble)] return half*exp(|x|) */ 61 if (ix < 0x42b17180) return half*__ieee754_expf(fabsf(x)); 62 63 /* |x| in [log(maxdouble), overflowthresold] */ 64 if (ix<=0x42b2d4fc) { 65 w = __ieee754_expf(half*fabsf(x)); 66 t = half*w; 67 return t*w; 68 } 69 70 /* |x| > overflowthresold, cosh(x) overflow */ 71 return huge*huge; 72 } 73