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/*=============================================================================
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) 2010 Fredrik Johansson
******************************************************************************/
#include "fmpz.h"
#include "arith.h"
void arith_euler_phi(fmpz_t res, const fmpz_t n)
{
fmpz_factor_t factors;
fmpz_t t;
ulong exp;
slong i;
if (fmpz_sgn(n) <= 0)
{
fmpz_zero(res);
return;
}
if (fmpz_abs_fits_ui(n))
{
fmpz_set_ui(res, n_euler_phi(fmpz_get_ui(n)));
return;
}
fmpz_factor_init(factors);
fmpz_factor(factors, n);
fmpz_one(res);
fmpz_init(t);
for (i = 0; i < factors->num; i++)
{
fmpz_sub_ui(t, factors->p + i, UWORD(1));
fmpz_mul(res, res, t);
exp = factors->exp[i];
if (exp != 1)
{
fmpz_pow_ui(t, factors->p + i, exp - UWORD(1));
fmpz_mul(res, res, t);
}
}
fmpz_clear(t);
fmpz_factor_clear(factors);
}
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