workbench/libs/mathieeedoubtrans/ieeedpcosh.c

   1 /*
   2     Copyright © 1995-2003, The AROS Development Team. All rights reserved.
   3     $Id$
   4 */
   5
   6 #include "mathieeedoubtrans_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       cosh(x) = (1/2)*( e^x + e^(-x) )
  30
  31       cosh( |x| >= 18 ) = (1/2) * (e^x);
  32
  33     HISTORY
  34 */
  35
  36 AROS_LHQUAD1(double, IEEEDPCosh,
  37     AROS_LHAQUAD(double, y, D0, D1),
  38     struct MathIeeeDoubTransBase *, MathIeeeDoubTransBase, 11, MathIeeeDoubTrans
  39 )
  40 {
  41     AROS_LIBFUNC_INIT
  42
  43     QUAD Res;
  44     /* cosh(-x) = cosh(x) */
  45     /* y &= ( IEEEDPMantisse_Mask + IEEEDPExponent_Mask ); */
  46     AND64QC
  47     (
  48         y,
  49         (IEEEDPMantisse_Mask_Hi + IEEEDPExponent_Mask_Hi),
  50         (IEEEDPMantisse_Mask_Lo + IEEEDPExponent_Mask_Lo)
  51     );
  52
  53     if ( is_eqC(y, IEEEDPPInfty_Hi, IEEEDPPInfty_Lo))
  54     {
  55         SetSR(Overflow_Bit, Zero_Bit | Negative_Bit | Overflow_Bit);
  56         return y;
  57     }
  58
  59     Res = IEEEDPExp(y);
  60
  61     if ( is_eqC(Res, IEEEDPPInfty_Hi, IEEEDPPInfty_Lo))
  62     {
  63         SetSR(Overflow_Bit, Zero_Bit | Negative_Bit | Overflow_Bit);
  64         return  Res;
  65     }
  66
  67     /* does adding of 1/(e^x) still change the result? */
  68     if ( is_lessC(y, 0x40320000, 0x0 ))
  69     {
  70         QUAD One;
  71         Set_Value64C(One, 0x3ff00000, 0x0);
  72
  73         Res = IEEEDPAdd(Res, IEEEDPDiv(One, Res));
  74     }
  75     /* Res = Res / 2 */
  76     ADD64QC(Res, 0xFFF00000, 0x0);
  77
  78     if
  79     (
  80            is_eqC(Res, 0x0, 0x0)
  81         || is_lessSC(Res, 0x0, 0x0)
  82     )
  83     {
  84         SetSR(Zero_Bit, Zero_Bit | Negative_Bit | Overflow_Bit);
  85         Set_Value64C(Res, 0x0, 0x0);
  86         return Res;
  87     }
  88     return Res;
  89
  90     AROS_LIBFUNC_EXIT
  91 }