sysdeps/ieee754/flt-32/s_tanhf.c

   1 /* s_tanhf.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 #if defined(LIBM_SCCS) && !defined(lint)
  17 static char rcsid[] = "$NetBSD: s_tanhf.c,v 1.4 1995/05/10 20:48:24 jtc Exp $";
  18 #endif
  19
  20 #include "math.h"
  21 #include "math_private.h"
  22
  23 #ifdef __STDC__
  24 static const float one=1.0, two=2.0, tiny = 1.0e-30;
  25 #else
  26 static float one=1.0, two=2.0, tiny = 1.0e-30;
  27 #endif
  28
  29 #ifdef __STDC__
  30         float __tanhf(float x)
  31 #else
  32         float __tanhf(x)
  33         float x;
  34 #endif
  35 {
  36         float t,z;
  37         int32_t jx,ix;
  38
  39         GET_FLOAT_WORD(jx,x);
  40         ix = jx&0x7fffffff;
  41
  42     /* x is INF or NaN */
  43         if(ix>=0x7f800000) {
  44             if (jx>=0) return one/x+one;    /* tanh(+-inf)=+-1 */
  45             else       return one/x-one;    /* tanh(NaN) = NaN */
  46         }
  47
  48     /* |x| < 22 */
  49         if (ix < 0x41b00000) {          /* |x|<22 */
  50             if (ix == 0)
  51                 return x;               /* x == +-0 */
  52             if (ix<0x24000000)          /* |x|<2**-55 */
  53                 return x*(one+x);       /* tanh(small) = small */
  54             if (ix>=0x3f800000) {       /* |x|>=1  */
  55                 t = __expm1f(two*fabsf(x));
  56                 z = one - two/(t+two);
  57             } else {
  58                 t = __expm1f(-two*fabsf(x));
  59                 z= -t/(t+two);
  60             }
  61     /* |x| > 22, return +-1 */
  62         } else {
  63             z = one - tiny;             /* raised inexact flag */
  64         }
  65         return (jx>=0)? z: -z;
  66 }
  67 weak_alias (__tanhf, tanhf)