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
  10     NAME */
  11
  12         AROS_LHQUAD1(double, IEEEDPCosh,
  13
  14 /*  SYNOPSIS */
  15         AROS_LHAQUAD(double, y, D0, D1),
  16
  17 /*  LOCATION */
  18         struct MathIeeeDoubTransBase *, MathIeeeDoubTransBase, 11, MathIeeeDoubTrans)
  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| >= 18 ) = (1/2) * (e^x);
  39
  40 *****************************************************************************/
  41 {
  42     AROS_LIBFUNC_INIT
  43
  44     QUAD Res;
  45     /* cosh(-x) = cosh(x) */
  46     /* y &= ( IEEEDPMantisse_Mask + IEEEDPExponent_Mask ); */
  47     AND64QC
  48     (
  49         y,
  50         (IEEEDPMantisse_Mask_Hi + IEEEDPExponent_Mask_Hi),
  51         (IEEEDPMantisse_Mask_Lo + IEEEDPExponent_Mask_Lo)
  52     );
  53
  54     if ( is_eqC(y, IEEEDPPInfty_Hi, IEEEDPPInfty_Lo))
  55     {
  56         SetSR(Overflow_Bit, Zero_Bit | Negative_Bit | Overflow_Bit);
  57         return y;
  58     }
  59
  60     Res = IEEEDPExp(y);
  61
  62     if ( is_eqC(Res, IEEEDPPInfty_Hi, IEEEDPPInfty_Lo))
  63     {
  64         SetSR(Overflow_Bit, Zero_Bit | Negative_Bit | Overflow_Bit);
  65         return  Res;
  66     }
  67
  68     /* does adding of 1/(e^x) still change the result? */
  69     if ( is_lessC(y, 0x40320000, 0x0 ))
  70     {
  71         QUAD One;
  72         Set_Value64C(One, 0x3ff00000, 0x0);
  73
  74         Res = IEEEDPAdd(Res, IEEEDPDiv(One, Res));
  75     }
  76     /* Res = Res / 2 */
  77     ADD64QC(Res, 0xFFF00000, 0x0);
  78
  79     if
  80     (
  81            is_eqC(Res, 0x0, 0x0)
  82         || is_lessSC(Res, 0x0, 0x0)
  83     )
  84     {
  85         SetSR(Zero_Bit, Zero_Bit | Negative_Bit | Overflow_Bit);
  86         Set_Value64C(Res, 0x0, 0x0);
  87         return Res;
  88     }
  89     return Res;
  90
  91     AROS_LIBFUNC_EXIT
  92 }