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