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 #include "math_private.h"
19 static const float one=1.0, two=2.0, tiny = 1.0e-30;
32 if (jx>=0) return one/x+one; /* tanh(+-inf)=+-1 */
33 else return one/x-one; /* tanh(NaN) = NaN */
37 if (ix < 0x41b00000) { /* |x|<22 */
38 if (ix<0x24000000) /* |x|<2**-55 */
39 return x*(one+x); /* tanh(small) = small */
40 if (ix>=0x3f800000) { /* |x|>=1 */
41 t = expm1f(two*fabsf(x));
42 z = one - two/(t+two);
44 t = expm1f(-two*fabsf(x));
47 /* |x| > 22, return +-1 */
49 z = one - tiny; /* raised inexact flag */
51 return (jx>=0)? z: -z;