pqc/external/flint-2.4.3/padic/pow_si.c

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2014-05-18 22:03:37 +00:00
/*=============================================================================
This file is part of FLINT.
FLINT 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.
FLINT 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 FLINT; if not, write to the Free Software
Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
=============================================================================*/
/******************************************************************************
Copyright (C) 2011, 2012 Sebastian Pancratz
******************************************************************************/
#include "padic.h"
void padic_pow_si(padic_t rop, const padic_t op, slong e, const padic_ctx_t ctx)
{
if (e == 0)
{
padic_one(rop);
}
else if (padic_is_zero(op) || e * padic_val(op) >= padic_prec(rop))
{
padic_zero(rop);
}
else
{
fmpz_t pow;
int alloc;
padic_val(rop) = e * padic_val(op);
alloc = _padic_ctx_pow_ui(pow, padic_prec(rop) - padic_val(rop), ctx);
if (e > 0)
{
fmpz_powm_ui(padic_unit(rop), padic_unit(op), e, pow);
}
else /* e < 0 */
{
/* u^{-1} to precision ceil((N - v e) / -e) */
_padic_inv(padic_unit(rop), padic_unit(op),
ctx->p, (padic_prec(rop) - padic_val(rop) + (-e - 1)) / -e);
fmpz_powm_ui(padic_unit(rop), padic_unit(rop), -e, pow);
}
if (alloc)
fmpz_clear(pow);
}
}