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/*
Copyright (C) 2023 Fredrik Johansson
This file is part of FLINT.
FLINT is free software: you can redistribute it and/or modify it under
the terms of the GNU Lesser General Public License (LGPL) as published
by the Free Software Foundation; either version 3 of the License, or
(at your option) any later version. See <https://www.gnu.org/licenses/>.
*/
#include "arb.h"
void
arb_nint(arb_t res, const arb_t x, slong prec)
{
if (arb_is_int(x))
{
arb_set(res, x);
}
else
{
arb_t t, u;
arb_init(t);
arb_init(u);
arb_set_d(t, 0.5);
arb_add(t, x, t, prec);
arb_mul_2exp_si(u, x, 1);
arb_sub_ui(u, u, 1, prec);
arb_mul_2exp_si(u, u, -2);
arb_floor(res, t, prec);
/* nint(x) = floor(x+0.5) - isint((2*x-1)/4) */
if (arb_is_int(u))
{
arb_sub_ui(res, res, 1, prec);
}
else if (arb_contains_int(u))
{
arf_one(arb_midref(u));
mag_one(arb_radref(u));
arb_mul_2exp_si(u, u, -1);
arb_sub_ui(res, res, 1, prec);
}
arb_clear(t);
arb_clear(u);
}
}