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     FUNCTION
  10       Calculate the sine of a given FFP number in radians
  11
  12     RESULT
  13       Motorola fast floating point number
  14
  15       flags:
  16         zero     : result is zero
  17         negative : result is negative
  18         overflow : 0
  19
  20     NOTES
  21
  22     EXAMPLE
  23
  24     BUGS
  25
  26     SEE ALSO
  27
  28     INTERNALS
  29      Algorithm for Calculation of sin(y):
  30      <code>
  31          z    = floor ( |y| / pi );
  32          y_1  = |y| - z * pi;        => 0 <= y_1 < pi
  33
  34          if (y_1 > pi/2 ) then y_1 = pi - y_1;
  35
  36          => 0 <= y_1 < pi/2
  37
  38          Res = y - y^3/3! + y^5/5! - y^7/7! + y^9/9! - y^11/11! =
  39              = y(1+y^2(-1/3!+y^2(1/5!+y^2(-1/7!+y^2(1/9!-1/11!y^2)))));
  40
  41          if (y < 0)
  42            Res = -Res;
  43
  44          if (z was an odd number)
  45            Res = -Res;
  46      </code>
  47
  48
  49     HISTORY
  50 */
  51
  52 AROS_LH1(float, SPSin,
  53     AROS_LHA(float, fnum1, D0),
  54     struct Library *, MathTransBase, 6, MathTrans
  55 )
  56 {
  57     AROS_LIBFUNC_INIT
  58
  59     LONG z,Res,ysquared,yabs,tmp;
  60     yabs = fnum1 & (FFPMantisse_Mask + FFPExponent_Mask);
  61
  62     if ((LONG)FFP_Pinfty == yabs)
  63     {
  64         SetSR(Overflow_Bit, Zero_Bit | Negative_Bit | Overflow_Bit);
  65         return FFP_NAN;
  66     }
  67
  68     z = SPFloor(SPDiv(pi, yabs));
  69     tmp  = SPMul(z,pi);
  70     tmp |= FFPSign_Mask; /* tmp = -tmp; */
  71     yabs = SPAdd(yabs, tmp);
  72
  73     if ( (char)yabs > (char)pio2  &&  (yabs & FFPMantisse_Mask) > (pio2 & FFPMantisse_Mask) )
  74     {
  75         yabs |= FFPSign_Mask;
  76         yabs  = SPAdd(pi, yabs);
  77     }
  78     ysquared = SPMul(yabs,yabs);
  79     Res = SPMul(yabs,
  80           SPAdd(sinf1,
  81           SPMul(ysquared,
  82           SPAdd(sinf2,
  83           SPMul(ysquared,
  84           SPAdd(sinf3,
  85           SPMul(ysquared,
  86           SPAdd(sinf4,
  87           SPMul(ysquared,
  88           SPAdd(sinf5,
  89           SPMul(ysquared, sinf6)))))))))));
  90
  91     if ((char)fnum1 < 0 ) Res ^= FFPSign_Mask;
  92
  93     if (TRUE == intern_SPisodd(z)) Res ^= FFPSign_Mask;
  94
  95     if (0 == Res)
  96     {
  97         SetSR(Zero_Bit, Zero_Bit | Negative_Bit | Overflow_Bit);
  98         return 0;
  99     }
 100
 101     if ((char)Res < 0)
 102     {
 103         SetSR(Negative_Bit, Zero_Bit | Negative_Bit | Overflow_Bit);
 104     }
 105
 106     return Res;
 107
 108     AROS_LIBFUNC_EXIT
 109 }