Subversion Repositories Kolibri OS

Rev

Go to most recent revision | Blame | Last modification | View Log | RSS feed

  1. /* sf_tanh.c -- float version of s_tanh.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 "fdlibm.h"
  17.  
  18. #ifdef __STDC__
  19. static const float one=1.0, two=2.0, tiny = 1.0e-30;
  20. #else
  21. static float one=1.0, two=2.0, tiny = 1.0e-30;
  22. #endif
  23.  
  24. #ifdef __STDC__
  25.         float tanhf(float x)
  26. #else
  27.         float tanhf(x)
  28.         float x;
  29. #endif
  30. {
  31.         float t,z;
  32.         __int32_t jx,ix;
  33.  
  34.         GET_FLOAT_WORD(jx,x);
  35.         ix = jx&0x7fffffff;
  36.  
  37.     /* x is INF or NaN */
  38.         if(!FLT_UWORD_IS_FINITE(ix)) {
  39.             if (jx>=0) return one/x+one;    /* tanh(+-inf)=+-1 */
  40.             else       return one/x-one;    /* tanh(NaN) = NaN */
  41.         }
  42.  
  43.     /* |x| < 22 */
  44.         if (ix < 0x41b00000) {          /* |x|<22 */
  45.             if (ix<0x24000000)          /* |x|<2**-55 */
  46.                 return x*(one+x);       /* tanh(small) = small */
  47.             if (ix>=0x3f800000) {       /* |x|>=1  */
  48.                 t = expm1f(two*fabsf(x));
  49.                 z = one - two/(t+two);
  50.             } else {
  51.                 t = expm1f(-two*fabsf(x));
  52.                 z= -t/(t+two);
  53.             }
  54.     /* |x| > 22, return +-1 */
  55.         } else {
  56.             z = one - tiny;             /* raised inexact flag */
  57.         }
  58.         return (jx>=0)? z: -z;
  59. }
  60.  
  61. #ifdef _DOUBLE_IS_32BITS
  62.  
  63. #ifdef __STDC__
  64.         double tanh(double x)
  65. #else
  66.         double tanh(x)
  67.         double x;
  68. #endif
  69. {
  70.         return (double) tanhf((float) x);
  71. }
  72.  
  73. #endif /* defined(_DOUBLE_IS_32BITS) */
  74.