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 __FBSDID("$FreeBSD$");
18
19 #include "math.h"
20 #include "math_private.h"
21
22 static const float one=1.0, two=2.0, tiny = 1.0e-30, huge = 1.0e30;
23 float
tanhf(float x)24 tanhf(float x)
25 {
26 float t,z;
27 int32_t jx,ix;
28
29 GET_FLOAT_WORD(jx,x);
30 ix = jx&0x7fffffff;
31
32 /* x is INF or NaN */
33 if(ix>=0x7f800000) {
34 if (jx>=0) return one/x+one; /* tanh(+-inf)=+-1 */
35 else return one/x-one; /* tanh(NaN) = NaN */
36 }
37
38 /* |x| < 9 */
39 if (ix < 0x41100000) { /* |x|<9 */
40 if (ix<0x39800000) { /* |x|<2**-12 */
41 if(huge+x>one) return x; /* tanh(tiny) = tiny with inexact */
42 }
43 if (ix>=0x3f800000) { /* |x|>=1 */
44 t = expm1f(two*fabsf(x));
45 z = one - two/(t+two);
46 } else {
47 t = expm1f(-two*fabsf(x));
48 z= -t/(t+two);
49 }
50 /* |x| >= 9, return +-1 */
51 } else {
52 z = one - tiny; /* raise inexact flag */
53 }
54 return (jx>=0)? z: -z;
55 }
56