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  1. double
  2. _DEFUN (sine, (double, int),
  3.         double x _AND
  4.         int cosine)
  5. {
  6.   int sgn, N;
  7.   double y, XN, g, R, res;
  8.   double YMAX = 210828714.0;
  9.  
  10.   switch (numtest (x))
  11.     {
  12.       case NAN:
  13.         errno = EDOM;
  14.         return (x);
  15.       case INF:
  16.         errno = EDOM;
  17.         return (z_notanum.d);
  18.     }
  19.  
  20.   /* Use sin and cos properties to ease computations. */
  21.   if (cosine)
  22.     {
  23.       sgn = 1;
  24.       y = fabs (x) + HALF_PI;
  25.     }
  26.   else
  27.     {
  28.       if (x < 0.0)
  29.         {
  30.           sgn = -1;
  31.           y = -x;
  32.         }
  33.       else
  34.         {
  35.           sgn = 1;
  36.           y = x;
  37.         }
  38.     }
  39.  
  40.   /* Check for values of y that will overflow here. */
  41.   if (y > YMAX)
  42.     {
  43.       errno = ERANGE;
  44.       return (x);
  45.     }
  46.  
  47.   /* Calculate the exponent. */
  48.   if (y < 0.0)
  49.     N = (int) (y * ONE_OVER_PI - 0.5);
  50.   else
  51.     N = (int) (y * ONE_OVER_PI + 0.5);
  52.   XN = (double) N;
  53.  
  54.   if (N & 1)
  55.     sgn = -sgn;
  56.  
  57.   if (cosine)
  58.     XN -= 0.5;
  59.  
  60.   y = fabs (x) - XN * __PI;
  61.  
  62.   if (-z_rooteps < y && y < z_rooteps)
  63.     res = y;
  64.  
  65.   else
  66.     {
  67.       g = y * y;
  68.  
  69.       /* Calculate the Taylor series. */
  70.       R = (((((((r[6] * g + r[5]) * g + r[4]) * g + r[3]) * g + r[2]) * g + r[1]) * g + r[0]) * g);
  71.  
  72.       /* Finally, compute the result. */
  73.       res = y + y * R;
  74.     }
  75.  
  76.   res *= sgn;
  77.  
  78.   return (res);
  79. }
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