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33 lines
1.2 KiB
C
33 lines
1.2 KiB
C
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/* Compute x^2 + y^2 - 1, without large cancellation error.
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Copyright (C) 2012 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with the GNU C Library; if not, see
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<http://www.gnu.org/licenses/>. */
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#include <math.h>
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#include <math_private.h>
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#include <float.h>
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/* Return X^2 + Y^2 - 1, computed without large cancellation error.
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It is given that 1 > X >= Y >= epsilon / 2, and that either X >=
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0.75 or Y >= 0.5. */
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float
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__x2y2m1f (float x, float y)
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{
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double dx = x, dy = y;
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return (float) ((dx - 1) * (dx + 1) + dy * dy);
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}
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