Subversion Repositories or1k

/* @(#)w_atan2.c 5.1 93/09/24 */

/*

 * ====================================================

 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.

 *

 * Developed at SunPro, a Sun Microsystems, Inc. business.

 * Permission to use, copy, modify, and distribute this

 * software is freely granted, provided that this notice

 * is preserved.

 * ====================================================

 *

 */

/*

FUNCTION

        <<atan2>>, <<atan2f>>---arc tangent of y/x

INDEX

   atan2

INDEX

   atan2f

ANSI_SYNOPSIS

        #include <math.h>

        double atan2(double <[y]>,double <[x]>);

        float atan2f(float <[y]>,float <[x]>);

TRAD_SYNOPSIS

        #include <math.h>

        double atan2(<[y]>,<[x]>);

        double <[y]>;

        double <[x]>;

        float atan2f(<[y]>,<[x]>);

        float <[y]>;

        float <[x]>;

DESCRIPTION

<<atan2>> computes the inverse tangent (arc tangent) of <[y]>/<[x]>.

<<atan2>> produces the correct result even for angles near

@ifinfo

pi/2 or -pi/2

@end ifinfo

@tex

$\pi/2$ or $-\pi/2$

@end tex

(that is, when <[x]> is near 0).

<<atan2f>> is identical to <<atan2>>, save that it takes and returns

<<float>>.

RETURNS

<<atan2>> and <<atan2f>> return a value in radians, in the range of

@ifinfo

-pi to pi.

@end ifinfo

@tex

$-\pi$ to $\pi$.

@end tex

If both <[x]> and <[y]> are 0.0, <<atan2>> causes a <<DOMAIN>> error.

You can modify error handling for these functions using <<matherr>>.

PORTABILITY

<<atan2>> is ANSI C.  <<atan2f>> is an extension.

*/

/*

 * wrapper atan2(y,x)

 */

#include "fdlibm.h"

#include <errno.h>

#ifndef _DOUBLE_IS_32BITS

#ifdef __STDC__

        double atan2(double y, double x)        /* wrapper atan2 */

#else

        double atan2(y,x)                       /* wrapper atan2 */

        double y,x;

#endif

{

#ifdef _IEEE_LIBM

        return __ieee754_atan2(y,x);

#else

        double z;

        struct exception exc;

        z = __ieee754_atan2(y,x);

        if(_LIB_VERSION == _IEEE_||isnan(x)||isnan(y)) return z;

        if(x==0.0&&y==0.0) {

            /* atan2(+-0,+-0) */

            exc.arg1 = y;

            exc.arg2 = x;

            exc.type = DOMAIN;

            exc.name = "atan2";

            exc.retval = 0.0;

            if(_LIB_VERSION == _POSIX_)

               errno = EDOM;

            else if (!matherr(&exc)) {

               errno = EDOM;

            }

            if (exc.err != 0)

               errno = exc.err;

            return exc.retval;

        } else

            return z;

#endif

}

#endif /* defined(_DOUBLE_IS_32BITS) */