arb/arb_fmpz_poly/deflate.c
2017-06-23 15:14:30 +02:00

38 lines
1,015 B
C

/*
Copyright (C) 2017 Fredrik Johansson
This file is part of Arb.
Arb 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 2.1 of the License, or
(at your option) any later version. See <http://www.gnu.org/licenses/>.
*/
#include "arb_fmpz_poly.h"
void
arb_fmpz_poly_deflate(fmpz_poly_t result, const fmpz_poly_t input, ulong deflation)
{
slong res_length, i;
if (deflation == 0)
{
flint_printf("Exception (fmpz_poly_deflate). Division by zero.\n");
flint_abort();
}
if (input->length <= 1 || deflation == 1)
{
fmpz_poly_set(result, input);
return;
}
res_length = (input->length - 1) / deflation + 1;
fmpz_poly_fit_length(result, res_length);
for (i = 0; i < res_length; i++)
fmpz_set(result->coeffs + i, input->coeffs + i*deflation);
result->length = res_length;
}