1 /* s_tanhf.c -- float version of s_tanh.c.
2 * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com.
3 */
4
5 /*
6 * ====================================================
7 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
8 *
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
12 * is preserved.
13 * ====================================================
14 */
15
16 #include <sys/cdefs.h>
17 #if defined(LIBM_SCCS) && !defined(lint)
18 __RCSID("$NetBSD: s_tanhf.c,v 1.7 2002/05/26 22:01:59 wiz Exp $");
19 #endif
20
21 #include "math.h"
22 #include "math_private.h"
23
24 static const float one=1.0, two=2.0, tiny = 1.0e-30;
25
26 float
tanhf(float x)27 tanhf(float x)
28 {
29 float t,z;
30 int32_t jx,ix;
31
32 GET_FLOAT_WORD(jx,x);
33 ix = jx&0x7fffffff;
34
35 /* x is INF or NaN */
36 if(ix>=0x7f800000) {
37 if (jx>=0) return one/x+one; /* tanh(+-inf)=+-1 */
38 else return one/x-one; /* tanh(NaN) = NaN */
39 }
40
41 /* |x| < 22 */
42 if (ix < 0x41b00000) { /* |x|<22 */
43 if (ix<0x24000000) /* |x|<2**-55 */
44 return x*(one+x); /* tanh(small) = small */
45 if (ix>=0x3f800000) { /* |x|>=1 */
46 t = expm1f(two*fabsf(x));
47 z = one - two/(t+two);
48 } else {
49 t = expm1f(-two*fabsf(x));
50 z= -t/(t+two);
51 }
52 /* |x| > 22, return +-1 */
53 } else {
54 z = one - tiny; /* raised inexact flag */
55 }
56 return (jx>=0)? z: -z;
57 }
58