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  1. /* Copyright (C) 1994 DJ Delorie, see COPYING.DJ for details */
  2. /* e_atanhf.c -- float version of e_atanh.c.
  3.  * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com.
  4.  */
  5.  
  6. /*
  7.  * ====================================================
  8.  * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
  9.  *
  10.  * Developed at SunPro, a Sun Microsystems, Inc. business.
  11.  * Permission to use, copy, modify, and distribute this
  12.  * software is freely granted, provided that this notice
  13.  * is preserved.
  14.  * ====================================================
  15.  */
  16.  
  17. #if defined(LIBM_SCCS) && !defined(lint)
  18. static char rcsid[] = "$Id: e_atanhf.c,v 1.2 1994/08/18 23:05:14 jtc Exp $";
  19. #endif
  20.  
  21. #include "math.h"
  22. #include "math_private.h"
  23.  
  24. #ifdef __STDC__
  25. static const float one = 1.0, huge = 1e30;
  26. #else
  27. static float one = 1.0, huge = 1e30;
  28. #endif
  29.  
  30. #ifdef __STDC__
  31. static const float zero = 0.0;
  32. #else
  33. static float zero = 0.0;
  34. #endif
  35.  
  36. #ifdef __STDC__
  37.         float __ieee754_atanhf(float x)
  38. #else
  39.         float __ieee754_atanhf(x)
  40.         float x;
  41. #endif
  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.