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  1. /* ef_atanh.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.  
  17. #include "fdlibm.h"
  18.  
  19. #ifdef __STDC__
  20. static const float one = 1.0, huge = 1e30;
  21. #else
  22. static float one = 1.0, huge = 1e30;
  23. #endif
  24.  
  25. #ifdef __STDC__
  26. static const float zero = 0.0;
  27. #else
  28. static float zero = 0.0;
  29. #endif
  30.  
  31. #ifdef __STDC__
  32.         float __ieee754_atanhf(float x)
  33. #else
  34.         float __ieee754_atanhf(x)
  35.         float x;
  36. #endif
  37. {
  38.         float t;
  39.         __int32_t hx,ix;
  40.         GET_FLOAT_WORD(hx,x);
  41.         ix = hx&0x7fffffff;
  42.         if (ix>0x3f800000)              /* |x|>1 */
  43.             return (x-x)/(x-x);
  44.         if(ix==0x3f800000)
  45.             return x/zero;
  46.         if(ix<0x31800000&&(huge+x)>zero) return x;      /* x<2**-28 */
  47.         SET_FLOAT_WORD(x,ix);
  48.         if(ix<0x3f000000) {             /* x < 0.5 */
  49.             t = x+x;
  50.             t = (float)0.5*log1pf(t+t*x/(one-x));
  51.         } else
  52.             t = (float)0.5*log1pf((x+x)/(one-x));
  53.         if(hx>=0) return t; else return -t;
  54. }
  55.