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     FUNCTION
  10       Calculate the hyperbolic cosine of the IEEE single precision number
  11
  12     RESULT
  13       IEEE single precision floating point number
  14
  15       flags:
  16         zero     : result is zero
  17         negative : 0 (not possible)
  18         overflow : result too big for ffp-number
  19
  20     NOTES
  21
  22     EXAMPLE
  23
  24     BUGS
  25
  26     SEE ALSO
  27
  28     INTERNALS
  29       <code>
  30       cosh(x) = (1/2)*( e^x + e^(-x) )
  31
  32       cosh( |x| >= 9  ) = (1/2) * (e^x);
  33       </code>
  34
  35     HISTORY
  36 */
  37
  38 AROS_LH1(float, IEEESPCosh,
  39     AROS_LHA(float, y, D0),
  40     struct Library *, MathIeeeSingTransBase, 11, MathIeeeSingTrans
  41 )
  42 {
  43     AROS_LIBFUNC_INIT
  44
  45     LONG Res;
  46     /* cosh(-x) = cosh(x) */
  47     y &= ( IEEESPMantisse_Mask + IEEESPExponent_Mask );
  48
  49     if ( IEEESP_Pinfty == y)
  50     {
  51         SetSR(Overflow_Bit, Zero_Bit | Negative_Bit | Overflow_Bit);
  52         return y;
  53     }
  54
  55     Res = IEEESPExp(y);
  56
  57     if ( IEEESP_Pinfty == Res )
  58     {
  59         SetSR(Overflow_Bit, Zero_Bit | Negative_Bit | Overflow_Bit);
  60         return 0x7f000000; /* Res; */
  61     }
  62
  63     if ( y < 0x41100000  ) Res = IEEESPAdd(Res, IEEESPDiv(one, Res));
  64
  65     /* Res = Res / 2 */
  66     Res -= 0x00800000;
  67
  68     if ( 0 == Res || Res < 0 )
  69     {
  70         SetSR(Zero_Bit, Zero_Bit | Negative_Bit | Overflow_Bit);
  71         return 0;
  72     }
  73
  74     return Res;
  75
  76     AROS_LIBFUNC_EXIT
  77 }