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 #include "math.h"
17 #include "math_private.h"
18 
19 static const float one = 1.0, huge = 1e30;
20 static const float zero = 0.0;
21 
22 float
23 atanhf(float x)
24 {
25 	float t;
26 	int32_t hx,ix;
27 	GET_FLOAT_WORD(hx,x);
28 	ix = hx&0x7fffffff;
29 	if (ix>0x3f800000) 		/* |x|>1 */
30 	    return (x-x)/(x-x);
31 	if(ix==0x3f800000)
32 	    return x/zero;
33 	if(ix<0x31800000&&(huge+x)>zero) return x;	/* x<2**-28 */
34 	SET_FLOAT_WORD(x,ix);
35 	if(ix<0x3f000000) {		/* x < 0.5 */
36 	    t = x+x;
37 	    t = (float)0.5*log1pf(t+t*x/(one-x));
38 	} else
39 	    t = (float)0.5*log1pf((x+x)/(one-x));
40 	if(hx>=0) return t; else return -t;
41 }
42