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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 | 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 | DESCRIPTION |
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| 30 | |
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| 31 | <<atan2>> computes the inverse tangent (arc tangent) of <[y]>/<[x]>. |
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| 32 | <<atan2>> produces the correct result even for angles near |
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| 33 | @ifnottex |
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| 34 | pi/2 or -pi/2 |
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| 35 | @end ifnottex |
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| 36 | @tex |
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| 37 | $\pi/2$ or $-\pi/2$ |
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| 38 | @end tex |
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| 39 | (that is, when <[x]> is near 0). |
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| 40 | |
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| 41 | <<atan2f>> is identical to <<atan2>>, save that it takes and returns |
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| 42 | <<float>>. |
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| 43 | |
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| 44 | RETURNS |
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| 45 | <<atan2>> and <<atan2f>> return a value in radians, in the range of |
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| 46 | @ifnottex |
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| 47 | -pi to pi. |
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| 48 | @end ifnottex |
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| 49 | @tex |
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| 50 | $-\pi$ to $\pi$. |
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| 51 | @end tex |
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| 52 | |
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| 53 | You can modify error handling for these functions using <<matherr>>. |
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| 54 | |
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| 55 | PORTABILITY |
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| 56 | <<atan2>> is ANSI C. <<atan2f>> is an extension. |
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| 57 | |
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| 58 | |
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| 59 | */ |
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| 60 | |
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| 61 | /* |
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| 62 | * wrapper atan2(y,x) |
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| 63 | */ |
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| 64 | |
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| 65 | #include "fdlibm.h" |
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| 66 | #include <errno.h> |
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| 67 | |
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| 68 | #ifndef _DOUBLE_IS_32BITS |
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| 69 | |
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| 70 | #ifdef __STDC__ |
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| 71 | double atan2(double y, double x) /* wrapper atan2 */ |
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| 72 | #else |
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| 73 | double atan2(y,x) /* wrapper atan2 */ |
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| 74 | double y,x; |
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| 75 | #endif |
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| 76 | { |
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| 77 | return __ieee754_atan2(y,x); |
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| 78 | } |
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| 79 | |
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| 80 | #endif /* defined(_DOUBLE_IS_32BITS) */ |
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