toolchain/gcc/newlib/libm/math/w_atan2.c

   1
   2 /* @(#)w_atan2.c 5.1 93/09/24 */
   3 /*
   4  * ====================================================
   5  * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
   6  *
   7  * Developed at SunPro, a Sun Microsystems, Inc. business.
   8  * Permission to use, copy, modify, and distribute this
   9  * software is freely granted, provided that this notice
  10  * is preserved.
  11  * ====================================================
  12  *
  13  */
  14
  15 /*
  16 FUNCTION
  17         <<atan2>>, <<atan2f>>---arc tangent of y/x
  18
  19 INDEX
  20    atan2
  21 INDEX
  22    atan2f
  23
  24 ANSI_SYNOPSIS
  25         #include <math.h>
  26         double atan2(double <[y]>,double <[x]>);
  27         float atan2f(float <[y]>,float <[x]>);
  28
  29 TRAD_SYNOPSIS
  30         #include <math.h>
  31         double atan2(<[y]>,<[x]>);
  32         double <[y]>;
  33         double <[x]>;
  34
  35         float atan2f(<[y]>,<[x]>);
  36         float <[y]>;
  37         float <[x]>;
  38
  39 DESCRIPTION
  40
  41 <<atan2>> computes the inverse tangent (arc tangent) of <[y]>/<[x]>.
  42 <<atan2>> produces the correct result even for angles near
  43 @ifnottex
  44 pi/2 or -pi/2
  45 @end ifnottex
  46 @tex
  47 $\pi/2$ or $-\pi/2$
  48 @end tex
  49 (that is, when <[x]> is near 0).
  50
  51 <<atan2f>> is identical to <<atan2>>, save that it takes and returns
  52 <<float>>.
  53
  54 RETURNS
  55 <<atan2>> and <<atan2f>> return a value in radians, in the range of
  56 @ifnottex
  57 -pi to pi.
  58 @end ifnottex
  59 @tex
  60 $-\pi$ to $\pi$.
  61 @end tex
  62
  63 If both <[x]> and <[y]> are 0.0, <<atan2>> causes a <<DOMAIN>> error.
  64
  65 You can modify error handling for these functions using <<matherr>>.
  66
  67 PORTABILITY
  68 <<atan2>> is ANSI C.  <<atan2f>> is an extension.
  69
  70
  71 */
  72
  73 /*
  74  * wrapper atan2(y,x)
  75  */
  76
  77 #include "fdlibm.h"
  78 #include <errno.h>
  79
  80 #ifndef _DOUBLE_IS_32BITS
  81
  82 #ifdef __STDC__
  83         double atan2(double y, double x)        /* wrapper atan2 */
  84 #else
  85         double atan2(y,x)                       /* wrapper atan2 */
  86         double y,x;
  87 #endif
  88 {
  89 #ifdef _IEEE_LIBM
  90         return __ieee754_atan2(y,x);
  91 #else
  92         double z;
  93         struct exception exc;
  94         z = __ieee754_atan2(y,x);
  95         if(_LIB_VERSION == _IEEE_||isnan(x)||isnan(y)) return z;
  96         if(x==0.0&&y==0.0) {
  97             /* atan2(+-0,+-0) */
  98             exc.arg1 = y;
  99             exc.arg2 = x;
 100             exc.type = DOMAIN;
 101             exc.name = "atan2";
 102             exc.err = 0;
 103             exc.retval = 0.0;
 104             if(_LIB_VERSION == _POSIX_)
 105                errno = EDOM;
 106             else if (!matherr(&exc)) {
 107                errno = EDOM;
 108             }
 109             if (exc.err != 0)
 110                errno = exc.err;
 111             return exc.retval;
 112         } else
 113             return z;
 114 #endif
 115 }
 116
 117 #endif /* defined(_DOUBLE_IS_32BITS) */