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[/] [openrisc/] [trunk/] [gnu-src/] [newlib-1.18.0/] [newlib/] [libm/] [mathfp/] [sf_atangent.c] - Blame information for rev 262

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Line No. Rev Author Line
1 207 jeremybenn
 
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/* @(#)z_atangentf.c 1.0 98/08/13 */
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/******************************************************************
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 * The following routines are coded directly from the algorithms
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 * and coefficients given in "Software Manual for the Elementary
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 * Functions" by William J. Cody, Jr. and William Waite, Prentice
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 * Hall, 1980.
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 ******************************************************************/
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/******************************************************************
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 * Arctangent
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 *
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 * Input:
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 *   x - floating point value
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 *
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 * Output:
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 *   arctangent of x
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 *
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 * Description:
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 *   This routine calculates arctangents.
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 *
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 *****************************************************************/
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#include <float.h>
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#include "fdlibm.h"
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#include "zmath.h"
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static const float ROOT3 = 1.732050807;
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static const float a[] = { 0.0, 0.523598775, 1.570796326,
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                     1.047197551 };
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static const float q[] = { 0.1412500740e+1 };
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static const float p[] = { -0.4708325141, -0.5090958253e-1 };
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float
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_DEFUN (atangentf, (float, float, float, int),
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        float x _AND
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        float v _AND
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        float u _AND
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        int arctan2)
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{
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  float f, g, R, P, Q, A, res;
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  int N;
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  int branch = 0;
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  int expv, expu;
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  /* Preparation for calculating arctan2. */
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  if (arctan2)
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    {
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      if (u == 0.0)
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        if (v == 0.0)
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          {
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            errno = ERANGE;
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            return (z_notanum_f.f);
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          }
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        else
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          {
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            branch = 1;
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            res = __PI_OVER_TWO;
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          }
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      if (!branch)
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        {
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          int e;
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          /* Get the exponent values of the inputs. */
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          g = frexpf (v, &expv);
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          g = frexpf (u, &expu);
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          /* See if a divide will overflow. */
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          e = expv - expu;
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          if (e > FLT_MAX_EXP)
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            {
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               branch = 1;
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               res = __PI_OVER_TWO;
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            }
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          /* Also check for underflow. */
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          else if (e < FLT_MIN_EXP)
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            {
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               branch = 2;
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               res = 0.0;
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            }
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         }
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    }
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  if (!branch)
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    {
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      if (arctan2)
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        f = fabsf (v / u);
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      else
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        f = fabsf (x);
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      if (f > 1.0)
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        {
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          f = 1.0 / f;
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          N = 2;
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        }
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      else
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        N = 0;
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      if (f > (2.0 - ROOT3))
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        {
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          A = ROOT3 - 1.0;
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          f = (((A * f - 0.5) - 0.5) + f) / (ROOT3 + f);
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          N++;
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        }
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      /* Check for values that are too small. */
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      if (-z_rooteps_f < f && f < z_rooteps_f)
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        res = f;
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      /* Calculate the Taylor series. */
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      else
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        {
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          g = f * f;
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          P = (p[1] * g + p[0]) * g;
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          Q = g + q[0];
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          R = P / Q;
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          res = f + f * R;
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        }
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      if (N > 1)
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        res = -res;
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      res += a[N];
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    }
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  if (arctan2)
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    {
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      if (u < 0.0)
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        res = __PI - res;
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      if (v < 0.0)
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        res = -res;
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    }
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  else if (x < 0.0)
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    {
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      res = -res;
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    }
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  return (res);
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}

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