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 1.6 1999/07/02 15:37:43 simonb Exp $");
19#endif
20
21#include "math.h"
22#include "math_private.h"
23
24static const float one=1.0, two=2.0, tiny = 1.0e-30;
25
26float
27tanhf(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