lib/libm/src/e_atanhf.c

   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  * $NetBSD: e_atanhf.c,v 1.7 2002/05/26 22:01:49 wiz Exp $
  16  * $DragonFly: src/lib/libm/src/e_atanhf.c,v 1.1 2005/07/26 21:15:20 joerg Exp $
  17  */
  18
  19 #include <math.h>
  20 #include "math_private.h"
  21
  22 static const float one = 1.0, huge = 1e30;
  23
  24 static const float zero = 0.0;
  25
  26 float
  27 atanhf(float x)
  28 {
  29         float t;
  30         int32_t hx,ix;
  31         GET_FLOAT_WORD(hx,x);
  32         ix = hx&0x7fffffff;
  33         if (ix>0x3f800000)              /* |x|>1 */
  34             return (x-x)/(x-x);
  35         if(ix==0x3f800000)
  36             return x/zero;
  37         if(ix<0x31800000&&(huge+x)>zero) return x;      /* x<2**-28 */
  38         SET_FLOAT_WORD(x,ix);
  39         if(ix<0x3f000000) {             /* x < 0.5 */
  40             t = x+x;
  41             t = (float)0.5*log1pf(t+t*x/(one-x));
  42         } else
  43             t = (float)0.5*log1pf((x+x)/(one-x));
  44         if(hx>=0) return t; else return -t;
  45 }