workbench/libs/mathieeesingtrans/ieeespcosh.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, IEEESPCosh,
  13
  14 /*  SYNOPSIS */
  15         AROS_LHA(float, y, D0),
  16
  17 /*  LOCATION */
  18         struct Library *, MathIeeeSingTransBase, 11, MathIeeeSingTrans)
  19
  20 /*  FUNCTION
  21         Calculate the hyperbolic cosine 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 : 0 (not possible)
  31         overflow : result too big for ffp-number
  32
  33     BUGS
  34
  35     INTERNALS
  36         cosh(x) = (1/2)*( e^x + e^(-x) )
  37
  38         cosh( |x| >= 9  ) = (1/2) * (e^x);
  39
  40 *****************************************************************************/
  41 {
  42     AROS_LIBFUNC_INIT
  43
  44     LONG Res;
  45     /* cosh(-x) = cosh(x) */
  46     y &= ( IEEESPMantisse_Mask + IEEESPExponent_Mask );
  47
  48     if ( IEEESP_Pinfty == y)
  49     {
  50         SetSR(Overflow_Bit, Zero_Bit | Negative_Bit | Overflow_Bit);
  51         return y;
  52     }
  53
  54     Res = IEEESPExp(y);
  55
  56     if ( IEEESP_Pinfty == Res )
  57     {
  58         SetSR(Overflow_Bit, Zero_Bit | Negative_Bit | Overflow_Bit);
  59         return 0x7f000000; /* Res; */
  60     }
  61
  62     if ( y < 0x41100000  ) Res = IEEESPAdd(Res, IEEESPDiv(one, Res));
  63
  64     /* Res = Res / 2 */
  65     Res -= 0x00800000;
  66
  67     if ( 0 == Res || Res < 0 )
  68     {
  69         SetSR(Zero_Bit, Zero_Bit | Negative_Bit | Overflow_Bit);
  70         return 0;
  71     }
  72
  73     return Res;
  74
  75     AROS_LIBFUNC_EXIT
  76 }