arb/fmpz_holonomic/seq_mul.c

53 lines
1.8 KiB
C

/*=============================================================================
This file is part of ARB.
ARB is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.
ARB is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with ARB; if not, write to the Free Software
Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
=============================================================================*/
/******************************************************************************
Copyright (C) 2012 Fredrik Johansson
******************************************************************************/
#include "fmpz_holonomic.h"
void
fmpz_holonomic_seq_mul(fmpz_holonomic_t res, const fmpz_holonomic_t op1, const fmpz_holonomic_t op2)
{
if (op1->length <= 1 || op2->length <= 1)
{
fmpz_holonomic_one(res);
}
else if (op1->length != 2 || op2->length != 2)
{
printf("not implemented: product of non-hypergeometric sequences\n");
abort();
}
else
{
fmpz_holonomic_fit_length(res, 2);
/* todo: better to compute gcd first? */
fmpz_poly_mul(res->coeffs + 0, op1->coeffs + 0, op2->coeffs + 0);
fmpz_poly_mul(res->coeffs + 1, op1->coeffs + 1, op2->coeffs + 1);
fmpz_poly_neg(res->coeffs + 1, res->coeffs + 1);
_fmpz_holonomic_set_length(res, 2);
fmpz_holonomic_seq_normalise(res);
}
}