/* origin: FreeBSD /usr/src/lib/msun/src/e_coshf.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 "libm.h"
static const float one = 1.0, half = 0.5, huge = 1.0e30;
float coshf(float x)
{
float t, w;
int32_t ix;
GET_FLOAT_WORD(ix, x);
ix &= 0x7fffffff;
/* x is INF or NaN */
if (ix >= 0x7f800000)
return x*x;
/* |x| in [0,0.5*ln2], return 1+expm1(|x|)^2/(2*exp(|x|)) */
if (ix < 0x3eb17218) {
t = expm1f(fabsf(x));
w = one+t;
if (ix<0x39800000)
return one; /* cosh(tiny) = 1 */
return one + (t*t)/(w+w);
}
/* |x| in [0.5*ln2,9], return (exp(|x|)+1/exp(|x|))/2; */
if (ix < 0x41100000) {
t = expf(fabsf(x));
return half*t + half/t;
}
/* |x| in [9, log(maxfloat)] return half*exp(|x|) */
if (ix < 0x42b17217)
return half*expf(fabsf(x));
/* |x| in [log(maxfloat), overflowthresold] */
if (ix <= 0x42b2d4fc)
return __expo2f(fabsf(x));
/* |x| > overflowthresold, cosh(x) overflow */
return huge*huge;
}
