118 lines
2.3 KiB
C
118 lines
2.3 KiB
C
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/* @(#)w_atan2.c 5.1 93/09/24 */
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/*
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* ====================================================
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* Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
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*
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* Developed at SunPro, a Sun Microsystems, Inc. business.
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* Permission to use, copy, modify, and distribute this
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* software is freely granted, provided that this notice
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* is preserved.
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* ====================================================
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*
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*/
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/*
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FUNCTION
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<<atan2>>, <<atan2f>>---arc tangent of y/x
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INDEX
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atan2
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INDEX
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atan2f
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ANSI_SYNOPSIS
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#include <math.h>
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double atan2(double <[y]>,double <[x]>);
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float atan2f(float <[y]>,float <[x]>);
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TRAD_SYNOPSIS
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#include <math.h>
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double atan2(<[y]>,<[x]>);
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double <[y]>;
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double <[x]>;
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float atan2f(<[y]>,<[x]>);
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float <[y]>;
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float <[x]>;
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DESCRIPTION
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<<atan2>> computes the inverse tangent (arc tangent) of <[y]>/<[x]>.
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<<atan2>> produces the correct result even for angles near
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@ifnottex
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pi/2 or -pi/2
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@end ifnottex
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@tex
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$\pi/2$ or $-\pi/2$
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@end tex
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(that is, when <[x]> is near 0).
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<<atan2f>> is identical to <<atan2>>, save that it takes and returns
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<<float>>.
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RETURNS
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<<atan2>> and <<atan2f>> return a value in radians, in the range of
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@ifnottex
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-pi to pi.
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@end ifnottex
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@tex
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$-\pi$ to $\pi$.
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@end tex
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If both <[x]> and <[y]> are 0.0, <<atan2>> causes a <<DOMAIN>> error.
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You can modify error handling for these functions using <<matherr>>.
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PORTABILITY
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<<atan2>> is ANSI C. <<atan2f>> is an extension.
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*/
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/*
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* wrapper atan2(y,x)
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*/
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#include "fdlibm.h"
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#include <errno.h>
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#ifndef _DOUBLE_IS_32BITS
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#ifdef __STDC__
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double atan2(double y, double x) /* wrapper atan2 */
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#else
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double atan2(y,x) /* wrapper atan2 */
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double y,x;
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#endif
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{
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#ifdef _IEEE_LIBM
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return __ieee754_atan2(y,x);
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#else
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double z;
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struct exception exc;
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z = __ieee754_atan2(y,x);
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if(_LIB_VERSION == _IEEE_||isnan(x)||isnan(y)) return z;
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if(x==0.0&&y==0.0) {
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/* atan2(+-0,+-0) */
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exc.arg1 = y;
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exc.arg2 = x;
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exc.type = DOMAIN;
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exc.name = "atan2";
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exc.err = 0;
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exc.retval = 0.0;
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if(_LIB_VERSION == _POSIX_)
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errno = EDOM;
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else if (!matherr(&exc)) {
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errno = EDOM;
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}
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if (exc.err != 0)
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errno = exc.err;
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return exc.retval;
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} else
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return z;
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#endif
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}
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#endif /* defined(_DOUBLE_IS_32BITS) */
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