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/*
Copyright (C) 2009 William Hart
Copyright (C) 2022 Albin Ahlbäck
Copyright (C) 2022 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 "gmpcompat.h"
#include "fmpz.h"
#define VARIANT 1
void
fmpz_add_ui(fmpz_t res, const fmpz_t x, ulong y)
{
if (!COEFF_IS_MPZ(*x))
{
slong a = *x;
if (y <= COEFF_MAX) /* likely case */
{
#if VARIANT
slong b = a + y;
if (b <= COEFF_MAX)
{
if (COEFF_IS_MPZ(*res))
_fmpz_clear_mpz(*res);
*res = b;
}
else
{
mpz_ptr mpz_res = _fmpz_promote(res);
flint_mpz_set_si(mpz_res, b);
}
#else
fmpz_set_si(res, a + (slong) y);
#endif
}
else
{
if (a < 0) /* opposite signs, and y > |a|, so no borrow */
fmpz_set_ui(res, y + a);
else
fmpz_set_uiui(res, ((ulong) a + y) < y, (ulong) a + y);
}
}
else
{
mpz_ptr rp;
mpz_srcptr xp;
nn_ptr rd;
nn_srcptr xd;
slong xn_signed, xn;
ulong cy;
xp = COEFF_TO_PTR(*x);
xn_signed = xp->_mp_size;
xn = FLINT_ABS(xn_signed);
if (COEFF_IS_MPZ(*res))
rp = COEFF_TO_PTR(*res);
else
rp = _fmpz_promote_val(res);
rd = FLINT_MPZ_REALLOC(rp, xn + 1);
xd = xp->_mp_d;
if (xn_signed >= 0) /* positive + nonnegative */
{
rd[xn] = cy = mpn_add_1(rd, xd, xn, y);
rp->_mp_size = xn + (cy != 0);
}
else if (xn >= 2) /* negative + nonnegative; result cannot be 0 */
{
mpn_sub_1(rd, xd, xn, y);
xn -= (rd[xn - 1] == 0);
rp->_mp_size = -xn;
if (xn == 1 && rd[0] <= COEFF_MAX) /* possible demotion */
{
cy = rd[0];
_fmpz_clear_mpz(*res);
*res = -(slong) cy;
}
}
else
{
/* 1 limb, different signs;
possible sign change and possible demotion */
ulong a = xd[0];
if (y >= a)
{
if (y - a <= COEFF_MAX)
{
_fmpz_clear_mpz(*res);
*res = y - a;
}
else
{
rd[0] = y - a;
rp->_mp_size = 1;
}
}
else
{
if (a - y <= COEFF_MAX)
{
_fmpz_clear_mpz(*res);
*res = -(slong) (a - y);
}
else
{
rd[0] = a - y;
rp->_mp_size = -1;
}
}
}
}
}
void
fmpz_sub_ui(fmpz_t res, const fmpz_t x, ulong y)
{
if (!COEFF_IS_MPZ(*x))
{
slong a = *x;
if (y <= COEFF_MAX)
{
#if VARIANT
slong b = a - y;
if (b >= COEFF_MIN)
{
if (COEFF_IS_MPZ(*res))
_fmpz_clear_mpz(*res);
*res = b;
}
else
{
mpz_ptr mpz_res = _fmpz_promote(res);
flint_mpz_set_si(mpz_res, b);
}
#else
fmpz_set_si(res, a - (slong) y);
#endif
}
else
{
if (a > 0) /* opposite signs, and y > |a|, so no borrow */
fmpz_neg_ui(res, y - a);
else
fmpz_neg_uiui(res, ((ulong) (-a) + y) < y, (ulong) (-a) + y);
}
}
else
{
mpz_ptr rp;
mpz_srcptr xp;
nn_ptr rd;
nn_srcptr xd;
slong xn_signed, xn;
ulong cy;
xp = COEFF_TO_PTR(*x);
xn_signed = xp->_mp_size;
xn = FLINT_ABS(xn_signed);
if (COEFF_IS_MPZ(*res))
rp = COEFF_TO_PTR(*res);
else
rp = _fmpz_promote_val(res);
rd = FLINT_MPZ_REALLOC(rp, xn + 1);
xd = xp->_mp_d;
if (xn_signed <= 0) /* positive + nonnegative */
{
rd[xn] = cy = mpn_add_1(rd, xd, xn, y);
rp->_mp_size = -(xn + (cy != 0));
}
else if (xn >= 2) /* negative + nonnegative; result cannot be 0 */
{
mpn_sub_1(rd, xd, xn, y);
xn -= (rd[xn - 1] == 0);
rp->_mp_size = xn;
if (xn == 1 && rd[0] <= COEFF_MAX) /* possible demotion */
{
cy = rd[0];
_fmpz_clear_mpz(*res);
*res = (slong) cy;
}
}
else
{
/* 1 limb, different signs;
possible sign change and possible demotion */
ulong a = xd[0];
if (y >= a)
{
if (y - a <= COEFF_MAX)
{
_fmpz_clear_mpz(*res);
*res = -(slong) (y - a);
}
else
{
rd[0] = y - a;
rp->_mp_size = -1;
}
}
else
{
if (a - y <= COEFF_MAX)
{
_fmpz_clear_mpz(*res);
*res = a - y;
}
else
{
rd[0] = a - y;
rp->_mp_size = 1;
}
}
}
}
}