80 lines
2.0 KiB
C
80 lines
2.0 KiB
C
/* Hypotenuse of a right-angled triangle.
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Copyright (C) 2012-2024 Free Software Foundation, Inc.
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This file is free software: you can redistribute it and/or modify
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it under the terms of the GNU Lesser General Public License as
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published by the Free Software Foundation, either version 3 of the
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License, or (at your option) any later version.
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This file 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
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GNU Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public License
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along with this program. If not, see <https://www.gnu.org/licenses/>. */
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/* Written by Bruno Haible <bruno@clisp.org>, 2012. */
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#include <config.h>
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/* Specification. */
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#include <math.h>
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double
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hypot (double x, double y)
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{
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if (isfinite (x) && isfinite (y))
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{
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/* Determine absolute values. */
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x = fabs (x);
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y = fabs (y);
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{
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/* Find the bigger and the smaller one. */
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double a;
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double b;
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if (x >= y)
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{
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a = x;
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b = y;
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}
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else
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{
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a = y;
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b = x;
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}
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/* Now 0 <= b <= a. */
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{
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int e;
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double an;
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double bn;
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/* Write a = an * 2^e, b = bn * 2^e with 0 <= bn <= an < 1. */
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an = frexp (a, &e);
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bn = ldexp (b, - e);
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{
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double cn;
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/* Through the normalization, no unneeded overflow or underflow
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will occur here. */
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cn = sqrt (an * an + bn * bn);
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return ldexp (cn, e);
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}
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}
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}
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}
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else
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{
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if (isinf (x) || isinf (y))
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/* x or y is infinite. Return +Infinity. */
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return HUGE_VAL;
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else
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/* x or y is NaN. Return NaN. */
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return x + y;
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}
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}
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