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/* s_tanhf.c -- float version of s_tanh.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.
* ====================================================
*/
#if defined(LIBM_SCCS) && !defined(lint)
static char rcsid[] = "$NetBSD: s_tanhf.c,v 1.4 1995/05/10 20:48:24 jtc Exp $";
#endif
#include <float.h>
#include <math.h>
#include <math_private.h>
#include <math-underflow.h>
#include <libm-alias-float.h>
static const float one=1.0, two=2.0, tiny = 1.0e-30;
float __tanhf(float x)
{
float t,z;
int32_t jx,ix;
GET_FLOAT_WORD(jx,x);
ix = jx&0x7fffffff;
/* x is INF or NaN */
if(ix>=0x7f800000) {
if (jx>=0) return one/x+one; /* tanh(+-inf)=+-1 */
else return one/x-one; /* tanh(NaN) = NaN */
}
/* |x| < 22 */
if (ix < 0x41b00000) { /* |x|<22 */
if (ix == 0)
return x; /* x == +-0 */
if (ix<0x24000000) /* |x|<2**-55 */
{
math_check_force_underflow (x);
return x*(one+x); /* tanh(small) = small */
}
if (ix>=0x3f800000) { /* |x|>=1 */
t = __expm1f(two*fabsf(x));
z = one - two/(t+two);
} else {
t = __expm1f(-two*fabsf(x));
z= -t/(t+two);
}
/* |x| > 22, return +-1 */
} else {
z = one - tiny; /* raised inexact flag */
}
return (jx>=0)? z: -z;
}
libm_alias_float (__tanh, tanh)
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