newlib/libm/mathfp/s_atan2.c

   1
   2 /* @(#)z_atan2.c 1.0 98/08/13 */
   3
   4 /*
   5 FUNCTION
   6         <<atan2>>, <<atan2f>>---arc tangent of y/x
   7
   8 INDEX
   9    atan2
  10 INDEX
  11    atan2f
  12
  13 SYNOPSIS
  14         #include <math.h>
  15         double atan2(double <[y]>,double <[x]>);
  16         float atan2f(float <[y]>,float <[x]>);
  17
  18 DESCRIPTION
  19
  20 <<atan2>> computes the inverse tangent (arc tangent) of <[y]>/<[x]>.
  21 <<atan2>> produces the correct result even for angles near
  22 @ifnottex
  23 pi/2 or -pi/2
  24 @end ifnottex
  25 @tex
  26 $\pi/2$ or $-\pi/2$
  27 @end tex
  28 (that is, when <[x]> is near 0).
  29
  30 <<atan2f>> is identical to <<atan2>>, save that it takes and returns
  31 <<float>>.
  32
  33 RETURNS
  34 <<atan2>> and <<atan2f>> return a value in radians, in the range of
  35 @ifnottex
  36 -pi to pi.
  37 @end ifnottex
  38 @tex
  39 $-\pi$ to $\pi$.
  40 @end tex
  41
  42 If both <[x]> and <[y]> are 0.0, <<atan2>> causes a <<DOMAIN>> error.
  43
  44 PORTABILITY
  45 <<atan2>> is ANSI C.  <<atan2f>> is an extension.
  46
  47
  48 */
  49
  50 /******************************************************************
  51  * Arctangent2
  52  *
  53  * Input:
  54  *   v, u - floating point values
  55  *
  56  * Output:
  57  *   arctan2 of v / u
  58  *
  59  * Description:
  60  *   This routine returns the arctan2 of v / u.
  61  *
  62  *****************************************************************/
  63
  64 #include "fdlibm.h"
  65 #include "zmath.h"
  66
  67 #ifndef _DOUBLE_IS_32BITS
  68
  69 double
  70 atan2 (double v,
  71         double u)
  72 {
  73   return (atangent (0.0, v, u, 1));
  74 }
  75
  76 #endif /* _DOUBLE_IS_32BITS */