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/*
Copyright (C) 2014 Alex J. Best
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 "fmpz.h"
#include "fmpz_mat.h"
int fmpz_mat_is_in_snf(const fmpz_mat_t A)
{
slong i, j;
for (i = 0; i < A->r; i++)
{
for (j = 0; j < A->c; j++)
{
if (i == j)
{
if (fmpz_sgn(fmpz_mat_entry(A, i, i)) < 0)
return 0;
if (i > 0)
{
if (!fmpz_is_zero(fmpz_mat_entry(A, i, i)) &&
fmpz_is_zero(fmpz_mat_entry(A, i - 1, i - 1)))
return 0;
if (!fmpz_divisible(fmpz_mat_entry(A, i, i),
fmpz_mat_entry(A, i - 1, i - 1)))
return 0;
}
}
else if (!fmpz_is_zero(fmpz_mat_entry(A, i, j)))
return 0;
}
}
return 1;
}