workbench/libs/mathtrans/spsin.c

   1 /*
   2     Copyright © 1995-2003, The AROS Development Team. All rights reserved.
   3     $Id$
   4 */
   5
   6 #include "mathtrans_intern.h"
   7
   8 /*****************************************************************************
   9
  10     NAME */
  11
  12         AROS_LH1(float, SPSin,
  13
  14 /*  SYNOPSIS */
  15         AROS_LHA(float, fnum1, D0),
  16
  17 /*  LOCATION */
  18         struct Library *, MathTransBase, 6, MathTrans)
  19
  20 /*  FUNCTION
  21         Calculate the sine of a given FFP number in radians
  22
  23     INPUTS
  24
  25     RESULT
  26         Motorola fast floating point number
  27
  28         flags:
  29         zero     : result is zero
  30         negative : result is negative
  31         overflow : 0
  32
  33     BUGS
  34
  35     INTERNALS
  36         Algorithm for Calculation of sin(y):
  37
  38         z    = floor ( |y| / pi );
  39         y_1  = |y| - z * pi;        => 0 <= y_1 < pi
  40
  41         if (y_1 > pi/2 ) then y_1 = pi - y_1;
  42
  43         => 0 <= y_1 < pi/2
  44
  45         Res = y - y^3/3! + y^5/5! - y^7/7! + y^9/9! - y^11/11! =
  46             = y(1+y^2(-1/3!+y^2(1/5!+y^2(-1/7!+y^2(1/9!-1/11!y^2)))));
  47
  48         if (y < 0)
  49           Res = -Res;
  50
  51         if (z was an odd number)
  52           Res = -Res;
  53
  54 *****************************************************************************/
  55 {
  56     AROS_LIBFUNC_INIT
  57
  58     LONG z,Res,ysquared,yabs,tmp;
  59     yabs = fnum1 & (FFPMantisse_Mask + FFPExponent_Mask);
  60
  61     if ((LONG)FFP_Pinfty == yabs)
  62     {
  63         SetSR(Overflow_Bit, Zero_Bit | Negative_Bit | Overflow_Bit);
  64         return FFP_NAN;
  65     }
  66
  67     z = SPFloor(SPDiv(pi, yabs));
  68     tmp  = SPMul(z,pi);
  69     tmp |= FFPSign_Mask; /* tmp = -tmp; */
  70     yabs = SPAdd(yabs, tmp);
  71
  72     if ( (char)yabs > (char)pio2  &&  (yabs & FFPMantisse_Mask) > (pio2 & FFPMantisse_Mask) )
  73     {
  74         yabs |= FFPSign_Mask;
  75         yabs  = SPAdd(pi, yabs);
  76     }
  77     ysquared = SPMul(yabs,yabs);
  78     Res = SPMul(yabs,
  79           SPAdd(sinf1,
  80           SPMul(ysquared,
  81           SPAdd(sinf2,
  82           SPMul(ysquared,
  83           SPAdd(sinf3,
  84           SPMul(ysquared,
  85           SPAdd(sinf4,
  86           SPMul(ysquared,
  87           SPAdd(sinf5,
  88           SPMul(ysquared, sinf6)))))))))));
  89
  90     if ((char)fnum1 < 0 ) Res ^= FFPSign_Mask;
  91
  92     if (TRUE == intern_SPisodd(z)) Res ^= FFPSign_Mask;
  93
  94     if (0 == Res)
  95     {
  96         SetSR(Zero_Bit, Zero_Bit | Negative_Bit | Overflow_Bit);
  97         return 0;
  98     }
  99
 100     if ((char)Res < 0)
 101     {
 102         SetSR(Negative_Bit, Zero_Bit | Negative_Bit | Overflow_Bit);
 103     }
 104
 105     return Res;
 106
 107     AROS_LIBFUNC_EXIT
 108 }