1*2fe8fb19SBen Gras /* s_tanhf.c -- float version of s_tanh.c.
2*2fe8fb19SBen Gras * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com.
3*2fe8fb19SBen Gras */
4*2fe8fb19SBen Gras
5*2fe8fb19SBen Gras /*
6*2fe8fb19SBen Gras * ====================================================
7*2fe8fb19SBen Gras * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
8*2fe8fb19SBen Gras *
9*2fe8fb19SBen Gras * Developed at SunPro, a Sun Microsystems, Inc. business.
10*2fe8fb19SBen Gras * Permission to use, copy, modify, and distribute this
11*2fe8fb19SBen Gras * software is freely granted, provided that this notice
12*2fe8fb19SBen Gras * is preserved.
13*2fe8fb19SBen Gras * ====================================================
14*2fe8fb19SBen Gras */
15*2fe8fb19SBen Gras
16*2fe8fb19SBen Gras #include <sys/cdefs.h>
17*2fe8fb19SBen Gras #if defined(LIBM_SCCS) && !defined(lint)
18*2fe8fb19SBen Gras __RCSID("$NetBSD: s_tanhf.c,v 1.7 2002/05/26 22:01:59 wiz Exp $");
19*2fe8fb19SBen Gras #endif
20*2fe8fb19SBen Gras
21*2fe8fb19SBen Gras #include "math.h"
22*2fe8fb19SBen Gras #include "math_private.h"
23*2fe8fb19SBen Gras
24*2fe8fb19SBen Gras static const float one=1.0, two=2.0, tiny = 1.0e-30;
25*2fe8fb19SBen Gras
26*2fe8fb19SBen Gras float
tanhf(float x)27*2fe8fb19SBen Gras tanhf(float x)
28*2fe8fb19SBen Gras {
29*2fe8fb19SBen Gras float t,z;
30*2fe8fb19SBen Gras int32_t jx,ix;
31*2fe8fb19SBen Gras
32*2fe8fb19SBen Gras GET_FLOAT_WORD(jx,x);
33*2fe8fb19SBen Gras ix = jx&0x7fffffff;
34*2fe8fb19SBen Gras
35*2fe8fb19SBen Gras /* x is INF or NaN */
36*2fe8fb19SBen Gras if(ix>=0x7f800000) {
37*2fe8fb19SBen Gras if (jx>=0) return one/x+one; /* tanh(+-inf)=+-1 */
38*2fe8fb19SBen Gras else return one/x-one; /* tanh(NaN) = NaN */
39*2fe8fb19SBen Gras }
40*2fe8fb19SBen Gras
41*2fe8fb19SBen Gras /* |x| < 22 */
42*2fe8fb19SBen Gras if (ix < 0x41b00000) { /* |x|<22 */
43*2fe8fb19SBen Gras if (ix<0x24000000) /* |x|<2**-55 */
44*2fe8fb19SBen Gras return x*(one+x); /* tanh(small) = small */
45*2fe8fb19SBen Gras if (ix>=0x3f800000) { /* |x|>=1 */
46*2fe8fb19SBen Gras t = expm1f(two*fabsf(x));
47*2fe8fb19SBen Gras z = one - two/(t+two);
48*2fe8fb19SBen Gras } else {
49*2fe8fb19SBen Gras t = expm1f(-two*fabsf(x));
50*2fe8fb19SBen Gras z= -t/(t+two);
51*2fe8fb19SBen Gras }
52*2fe8fb19SBen Gras /* |x| > 22, return +-1 */
53*2fe8fb19SBen Gras } else {
54*2fe8fb19SBen Gras z = one - tiny; /* raised inexact flag */
55*2fe8fb19SBen Gras }
56*2fe8fb19SBen Gras return (jx>=0)? z: -z;
57*2fe8fb19SBen Gras }
58