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 */
39 return x
; /* x == +-0 */
40 if (ix
<0x24000000) /* |x|<2**-55 */
41 return x
*(one
+x
); /* tanh(small) = small */
42 if (ix
>=0x3f800000) { /* |x|>=1 */
43 t
= expm1f(two
*fabsf(x
));
44 z
= one
- two
/(t
+two
);
46 t
= expm1f(-two
*fabsf(x
));
49 /* |x| > 22, return +-1 */
51 z
= one
- tiny
; /* raised inexact flag */
53 return (jx
>=0)? z
: -z
;