POK
e_atanhf.c
1 /*
2  * POK header
3  *
4  * The following file is a part of the POK project. Any modification should
5  * made according to the POK licence. You CANNOT use this file or a part of
6  * this file is this part of a file for your own project
7  *
8  * For more information on the POK licence, please see our LICENCE FILE
9  *
10  * Please follow the coding guidelines described in doc/CODING_GUIDELINES
11  *
12  * Copyright (c) 2007-2009 POK team
13  *
14  * Created by julien on Fri Jan 30 14:41:34 2009
15  */
16 
17 /* e_atanhf.c -- float version of e_atanh.c.
18  * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com.
19  */
20 
21 /*
22  * ====================================================
23  * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
24  *
25  * Developed at SunPro, a Sun Microsystems, Inc. business.
26  * Permission to use, copy, modify, and distribute this
27  * software is freely granted, provided that this notice
28  * is preserved.
29  * ====================================================
30  */
31 
32 #ifdef POK_NEEDS_LIBMATH
33 #include <libm.h>
34 #include "math_private.h"
35 
36 static const float one = 1.0, huge = 1e30;
37 
38 static const float zero = 0.0;
39 
40 float
41 __ieee754_atanhf(float x)
42 {
43  float t;
44  int32_t hx,ix;
45  GET_FLOAT_WORD(hx,x);
46  ix = hx&0x7fffffff;
47  if (ix>0x3f800000) /* |x|>1 */
48  return (x-x)/(x-x);
49  if(ix==0x3f800000)
50  return x/zero;
51  if(ix<0x31800000&&(huge+x)>zero) return x; /* x<2**-28 */
52  SET_FLOAT_WORD(x,ix);
53  if(ix<0x3f000000) { /* x < 0.5 */
54  t = x+x;
55  t = (float)0.5*log1pf(t+t*x/(one-x));
56  } else
57  t = (float)0.5*log1pf((x+x)/(one-x));
58  if(hx>=0) return t; else return -t;
59 }
60 #endif