1 /* s_tanhf.c -- float version of s_tanh.c.
2 * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com.
6 * ====================================================
7 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
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
13 * ====================================================
17 static char rcsid[] = "$FreeBSD$";
21 #include "math_private.h"
23 static const float one=1.0, two=2.0, tiny = 1.0e-30;
36 if (jx>=0) return one/x+one; /* tanh(+-inf)=+-1 */
37 else return one/x-one; /* tanh(NaN) = NaN */
41 if (ix < 0x41b00000) { /* |x|<22 */
42 if (ix<0x24000000) /* |x|<2**-55 */
43 return x*(one+x); /* tanh(small) = small */
44 if (ix>=0x3f800000) { /* |x|>=1 */
45 t = expm1f(two*fabsf(x));
46 z = one - two/(t+two);
48 t = expm1f(-two*fabsf(x));
51 /* |x| > 22, return +-1 */
53 z = one - tiny; /* raised inexact flag */
55 return (jx>=0)? z: -z;