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/* Hypotenuse of a right-angled triangle.
Copyright (C) 2012-2021 Free Software Foundation, Inc.
This file is free software: you can redistribute it and/or modify
it under the terms of the GNU Lesser General Public License as
published by the Free Software Foundation; either version 3 of the
License, or (at your option) any later version.
This file is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public License
along with this program. If not, see <https://www.gnu.org/licenses/>. */
/* Written by Bruno Haible <bruno@clisp.org>, 2012. */
#include <config.h>
/* Specification. */
#include <math.h>
double
hypot (double x, double y)
{
if (isfinite (x) && isfinite (y))
{
/* Determine absolute values. */
x = fabs (x);
y = fabs (y);
{
/* Find the bigger and the smaller one. */
double a;
double b;
if (x >= y)
{
a = x;
b = y;
}
else
{
a = y;
b = x;
}
/* Now 0 <= b <= a. */
{
int e;
double an;
double bn;
/* Write a = an * 2^e, b = bn * 2^e with 0 <= bn <= an < 1. */
an = frexp (a, &e);
bn = ldexp (b, - e);
{
double cn;
/* Through the normalization, no unneeded overflow or underflow
will occur here. */
cn = sqrt (an * an + bn * bn);
return ldexp (cn, e);
}
}
}
}
else
{
if (isinf (x) || isinf (y))
/* x or y is infinite. Return +Infinity. */
return HUGE_VAL;
else
/* x or y is NaN. Return NaN. */
return x + y;
}
}
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