e_atanhf.c revision 97407 
1/* e_atanhf.c -- float version of e_atanh.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#ifndef lint
17static char rcsid[] = "$FreeBSD: head/lib/msun/src/e_atanhf.c 97407 2002-05-28 17:03:12Z alfred $";
18#endif
19
20#include "math.h"
21#include "math_private.h"
22
23static const float one = 1.0, huge = 1e30;
24
25static const float zero = 0.0;
26
27float
28__ieee754_atanhf(float x)
29{
30	float t;
31	int32_t hx,ix;
32	GET_FLOAT_WORD(hx,x);
33	ix = hx&0x7fffffff;
34	if (ix>0x3f800000) 		/* |x|>1 */
35	    return (x-x)/(x-x);
36	if(ix==0x3f800000)
37	    return x/zero;
38	if(ix<0x31800000&&(huge+x)>zero) return x;	/* x<2**-28 */
39	SET_FLOAT_WORD(x,ix);
40	if(ix<0x3f000000) {		/* x < 0.5 */
41	    t = x+x;
42	    t = (float)0.5*log1pf(t+t*x/(one-x));
43	} else
44	    t = (float)0.5*log1pf((x+x)/(one-x));
45	if(hx>=0) return t; else return -t;
46}
47