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/*
Copyright (C) 2025 Kacper Proniewski
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 "fmpq.h"
#include "fmpq_poly.h"
#include "fmpz.h"
#include "fmpz_poly.h"
void _fmpq_poly_discriminant(
fmpq_t res, const fmpz* poly, const fmpz_t den, slong len)
{
fmpz_t rnum, rden;
fmpz_init(rnum);
fmpz_init(rden);
_fmpz_poly_discriminant(rnum, poly, len);
// according to the formula disc(c*f)=c^(2n-2)disc(f) where n=len-1 is the degree
fmpz_pow_ui(rden, den, (ulong)2 * len - 4);
fmpq_set_fmpz_frac(res, rnum, rden);
fmpz_clear(rnum);
fmpz_clear(rden);
}
void fmpq_poly_discriminant(fmpq_t res, const fmpq_poly_t poly)
{
slong len = poly->length;
if (len <= 1)
fmpq_zero(res);
else
_fmpq_poly_discriminant(res, poly->coeffs, poly->den, len);
}