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/* ef_acosh.c -- float version of e_acosh.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 "fdlibm.h"
#ifdef __STDC__
static const float
#else
static float
#endif
one = 1.0,
ln2 = 6.9314718246e-01; /* 0x3f317218 */
#if defined(_IEEE_LIBM) && defined(HAVE_ALIAS_ATTRIBUTE)
__strong_reference(__ieee754_acoshf, acoshf);
#endif
#ifdef __STDC__
float __ieee754_acoshf(float x)
#else
float __ieee754_acoshf(x)
float x;
#endif
{
float t;
__int32_t hx;
GET_FLOAT_WORD(hx,x);
if(hx<0x3f800000) { /* x < 1 */
return (x-x)/(x-x);
} else if(hx >=0x4d800000) { /* x > 2**28 */
if(!FLT_UWORD_IS_FINITE(hx)) { /* x is inf of NaN */
return x+x;
} else
return __ieee754_logf(x)+ln2; /* acosh(huge)=log(2x) */
} else if (hx==0x3f800000) {
return 0.0; /* acosh(1) = 0 */
} else if (hx > 0x40000000) { /* 2**28 > x > 2 */
t=x*x;
return __ieee754_logf((float)2.0*x-one/(x+__ieee754_sqrtf(t-one)));
} else { /* 1<x<2 */
t = x-one;
return log1pf(t+__ieee754_sqrtf((float)2.0*t+t*t));
}
}
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