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    Copyright (c) 2001-2003 Joel de Guzman

    Distributed under the Boost Software License, Version 1.0. (See accompanying 
    file LICENSE_1_0.txt or copy at
#include <vector>
#include <algorithm>
#include <iostream>
#include <boost/spirit/include/phoenix_core.hpp>
#include <boost/spirit/include/phoenix_function.hpp>

using namespace boost::phoenix;
using namespace boost::phoenix::arg_names;
using namespace std;

struct factorial_impl
    template <typename Arg>
    struct result
        typedef Arg type;

    template <typename Arg>
    Arg operator()(Arg n) const
        return (n <= 0) ? 1 : n * this->operator()(n-1);

function<factorial_impl> factorial;

    int i = 4;
    cout << factorial(arg1)(i) << endl;
    return 0;