toolchain/gcc/newlib/libm/mathfp/s_atan.c

   1
   2 /* @(#)z_atan.c 1.0 98/08/13 */
   3
   4 /*
   5 FUNCTION
   6         <<atan>>, <<atanf>>---arc tangent
   7
   8 INDEX
   9    atan
  10 INDEX
  11    atanf
  12
  13 ANSI_SYNOPSIS
  14         #include <math.h>
  15         double atan(double <[x]>);
  16         float atanf(float <[x]>);
  17
  18 TRAD_SYNOPSIS
  19         #include <math.h>
  20         double atan(<[x]>);
  21         double <[x]>;
  22
  23         float atanf(<[x]>);
  24         float <[x]>;
  25
  26 DESCRIPTION
  27
  28 <<atan>> computes the inverse tangent (arc tangent) of the input value.
  29
  30 <<atanf>> is identical to <<atan>>, save that it operates on <<floats>>.
  31
  32 RETURNS
  33 @ifnottex
  34 <<atan>> returns a value in radians, in the range of -pi/2 to pi/2.
  35 @end ifnottex
  36 @tex
  37 <<atan>> returns a value in radians, in the range of $-\pi/2$ to $\pi/2$.
  38 @end tex
  39
  40 PORTABILITY
  41 <<atan>> is ANSI C.  <<atanf>> is an extension.
  42
  43 */
  44
  45 /******************************************************************
  46  * Arctangent
  47  *
  48  * Input:
  49  *   x - floating point value
  50  *
  51  * Output:
  52  *   arctan of x
  53  *
  54  * Description:
  55  *   This routine returns the arctan of x.
  56  *
  57  *****************************************************************/
  58
  59 #include "fdlibm.h"
  60 #include "zmath.h"
  61
  62 #ifndef _DOUBLE_IS_32BITS
  63
  64 double
  65 _DEFUN (atan, (double),
  66         double x)
  67 {
  68   switch (numtest (x))
  69     {
  70       case NAN:
  71         errno = EDOM;
  72         return (x);
  73       case INF:
  74         /* this should check to see if neg NaN or pos NaN... */
  75         return (__PI_OVER_TWO);
  76       case 0:
  77         return (0.0);
  78       default:
  79         return (atangent (x, 0, 0, 0));
  80     }
  81 }
  82
  83 #endif /* _DOUBLE_IS_32BITS */