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/*
Copyright (C) 2016 Fredrik Johansson
This file is part of Arb.
Arb 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 2.1 of the License, or
(at your option) any later version. See <http://www.gnu.org/licenses/>.
*/
#include "mag.h"
#include "arf.h"
void
mag_sub(mag_t z, const mag_t x, const mag_t y)
{
if (mag_is_special(x) || mag_is_special(y))
{
if (mag_is_inf(x))
mag_inf(z);
else if (mag_is_inf(y))
mag_zero(z);
else
mag_set(z, x); /* x - 0 = x; max(0 - y, 0) = 0 */
}
else
{
/* this should eventually have a proper implementation... */
arf_t t, u;
arf_init(t);
arf_init(u);
arf_set_mag(t, x);
arf_set_mag(u, y);
arf_sub(t, t, u, MAG_BITS, ARF_RND_UP);
if (arf_sgn(t) >= 0)
arf_get_mag(z, t);
else
mag_zero(z);
arf_clear(t);
arf_clear(u);
}
}
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