workbench/libs/mathieeesingtrans/ieeesptanh.c

   1 /*
   2     Copyright © 1995-2003, The AROS Development Team. All rights reserved.
   3     $Id$
   4 */
   5
   6 #include "mathieeesingtrans_intern.h"
   7
   8 /*****************************************************************************
   9
  10     NAME */
  11
  12         AROS_LH1(float, IEEESPTanh,
  13
  14 /*  SYNOPSIS */
  15         AROS_LHA(float, y, D0),
  16
  17 /*  LOCATION */
  18         struct Library *, MathIeeeSingTransBase, 12, MathIeeeSingTrans)
  19
  20 /*  FUNCTION
  21         Calculate hyperbolic tangens of the IEEE single precision number
  22
  23     INPUTS
  24
  25     RESULT
  26         IEEE single precision floating point number
  27
  28         flags:
  29         zero     : result is zero
  30         negative : result is negative
  31         overflow : (not possible)
  32
  33     BUGS
  34
  35     INTERNALS
  36
  37 *****************************************************************************/
  38 {
  39     AROS_LIBFUNC_INIT
  40
  41     LONG Res;
  42     LONG y2 = y & (IEEESPMantisse_Mask + IEEESPExponent_Mask );
  43     LONG tmp;
  44
  45     if ( y2 >= 0x41100000 )
  46     /*
  47         tanh( x > 9 ) =  1
  48         tanh( x <-9 ) = -1
  49     */
  50     return (one | ( y & IEEESPSign_Mask ));
  51
  52     /* tanh(-x) = -tanh(x) */
  53     Res = IEEESPExp(y2);
  54     tmp = IEEESPDiv(one, Res);
  55     Res = IEEESPDiv
  56     (
  57         IEEESPAdd(Res, (tmp | IEEESPSign_Mask) ),
  58         IEEESPAdd(Res, tmp)
  59     );
  60
  61     /* Result is zero */
  62     if (0 == Res )
  63     {
  64         if (y < 0)
  65         {
  66             SetSR(Zero_Bit | Negative_Bit, Zero_Bit | Negative_Bit | Overflow_Bit);
  67         }
  68         else
  69         {
  70             SetSR(Zero_Bit, Zero_Bit | Negative_Bit | Overflow_Bit);
  71         }
  72
  73         return (y & IEEESPSign_Mask);
  74     }
  75
  76     /* Argument is negative -> result is negative */
  77     if ( y < 0)
  78     {
  79         SetSR(Negative_Bit, Zero_Bit | Negative_Bit | Overflow_Bit);
  80         return (Res | IEEESPSign_Mask );
  81     }
  82
  83     return Res;
  84
  85     AROS_LIBFUNC_EXIT
  86 }