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/*
Copyright (C) 2021 Daniel Schultz
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_mpoly.h"
int fmpq_mpoly_discriminant(fmpq_mpoly_t R, const fmpq_mpoly_t A,
slong var, const fmpq_mpoly_ctx_t ctx)
{
int success;
fmpz_mpoly_univar_t Ax;
fmpz_mpoly_univar_init(Ax, ctx->zctx);
fmpz_mpoly_to_univar(Ax, A->zpoly, var, ctx->zctx);
success = fmpz_mpoly_univar_discriminant(R->zpoly, Ax, ctx->zctx);
if (success && Ax->length > 0)
{
fmpz_t t;
fmpz_init(t);
fmpz_mul_ui(t, Ax->exps + 0, 2);
fmpz_sub_ui(t, t, 2);
success = fmpq_pow_fmpz(R->content, A->content, t);
fmpz_clear(t);
}
else
{
fmpq_zero(R->content);
}
fmpq_mpoly_reduce(R, ctx);
fmpz_mpoly_univar_clear(Ax, ctx->zctx);
return success;
}