workbench/libs/mathtrans/sptan.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, SPTan,
  13
  14 /*  SYNOPSIS */
  15         AROS_LHA(float, fnum1, D0),
  16
  17 /*  LOCATION */
  18         struct Library *, MathTransBase, 8, MathTrans)
  19
  20 /*  FUNCTION
  21         Calculate the tangens 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 :
  32
  33     BUGS
  34
  35     INTERNALS
  36
  37 *****************************************************************************/
  38 {
  39     AROS_LIBFUNC_INIT
  40
  41     LONG z,SIN,Res,ysquared,yabs,tmp;
  42     yabs = fnum1 & (FFPMantisse_Mask + FFPExponent_Mask);
  43
  44     if ((LONG)FFP_Pinfty == yabs)
  45     {
  46         SetSR(Overflow_Bit, Zero_Bit | Negative_Bit | Overflow_Bit);
  47         return FFP_NAN;
  48     }
  49
  50     z = SPFloor(SPDiv(pi, yabs));
  51     tmp  = SPMul(z,pi);
  52     tmp |= FFPSign_Mask; /* tmp = -tmp; */
  53     yabs = SPAdd(yabs, tmp);
  54
  55     if ( (char)yabs > (char)pio2  &&  (yabs & FFPMantisse_Mask) > (pio2 & FFPMantisse_Mask) )
  56     {
  57         yabs |= FFPSign_Mask;
  58         yabs  =SPAdd(pi, yabs);
  59         tmp = TRUE;
  60     }
  61     else
  62     {
  63         tmp = FALSE;
  64     }
  65
  66     ysquared = SPMul(yabs,yabs);
  67                SIN = SPMul(yabs,
  68                SPAdd(sinf1,
  69                SPMul(ysquared,
  70                SPAdd(sinf2,
  71                SPMul(ysquared,
  72                SPAdd(sinf3,
  73                SPMul(ysquared,
  74                SPAdd(sinf4,
  75                SPMul(ysquared,
  76                SPAdd(sinf5,
  77                SPMul(ysquared, sinf6)))))))))));
  78     /* cos  */
  79     z   = SPAdd(cosf1,
  80           SPMul(ysquared,
  81           SPAdd(cosf2,
  82           SPMul(ysquared,
  83           SPAdd(cosf3,
  84           SPMul(ysquared,
  85           SPAdd(cosf4,
  86           SPMul(ysquared,
  87           SPAdd(cosf5,
  88           SPMul(ysquared, cosf6))))))))));
  89
  90     Res = SPDiv(z, SIN);
  91
  92     if ((char)fnum1 < 0 ) Res ^= FFPSign_Mask;
  93     if (TRUE == tmp)      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 }