fusion/test/algorithm/fold.cpp

/*=============================================================================
    Copyright (c) 2001-2006 Joel de Guzman
    Copyright (c) 2007 Dan Marsden

    Distributed under the Boost Software License, Version 1.0. (See accompanying 
    file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
==============================================================================*/
#include <boost/detail/lightweight_test.hpp>
#include <boost/fusion/sequence/container/vector/vector.hpp>
#include <boost/fusion/sequence/adapted/mpl.hpp>
#include <boost/fusion/sequence/io/out.hpp>
#include <boost/fusion/sequence/intrinsic/at.hpp>
#include <boost/fusion/algorithm/iteration/fold.hpp>
#include <boost/fusion/algorithm/iteration/accumulate.hpp>
#include <boost/type_traits/is_same.hpp>
#include <boost/mpl/if.hpp>
#include <boost/mpl/next.hpp>
#include <boost/mpl/int.hpp>
#include <boost/mpl/vector.hpp>

using boost::mpl::if_;
using boost::mpl::int_;
using boost::is_same;

struct add_ints_only
{
    template<typename T>
    struct result;

    template <typename T, typename State>
    struct result<add_ints_only(T,State)>
    {
        typedef State type;
    };

    template <typename T, typename State>
    State const&
    operator()(T const& x, State const& state) const
    {
        return state;
    }

    int
    operator()(int x, int state) const
    {
        return x + state;
    }
};

struct count_ints
{
    template<typename T>
    struct result;

    template <typename T, typename CountT>
    struct result<count_ints(T,CountT)>
    {
        typedef typename
            if_<
                is_same<T, int>
              , typename boost::mpl::next<CountT>::type
              , CountT
            >::type
        type;
    };

    template <typename T, typename CountT>
    typename result<count_ints(T, CountT)>::type
    operator()(T const&, CountT const&) const
    {
        typedef typename result<count_ints(T, CountT)>::type result;
        return result();
    }
};

int
main()
{
    using namespace boost::fusion;
    namespace fusion = boost::fusion;

    {
        typedef vector<int, char, int, double> vector_type;
        vector_type v(12345, 'x', 678910, 3.36);
        int result = fold(v, 0, add_ints_only());
        std::cout << result << std::endl;
        BOOST_TEST(result == 12345+678910);
    }

    {
        typedef vector<int> vector_type;
        vector_type v(12345);

        int n = fusion::fold(v, int_<0>(), count_ints());
        std::cout << n << std::endl;
        BOOST_TEST(n == 1);
    }

    {
        typedef vector<int, char, int, double, int> vector_type;
        vector_type v(12345, 'x', 678910, 3.36, 8756);

        int n = fusion::fold(v, int_<0>(), count_ints());
        std::cout << n << std::endl;
        BOOST_TEST(n == 3);
    }

    {
        typedef boost::mpl::vector<int, char, int, double, int> mpl_vec;
        int n = fusion::fold(mpl_vec(), int_<0>(), count_ints());
        std::cout << n << std::endl;
        BOOST_TEST(n == 3);
    }

    {
        typedef vector<int, char, int, double> vector_type;
        vector_type v(12345, 'x', 678910, 3.36);
        int result = accumulate(v, 0, add_ints_only());
        std::cout << result << std::endl;
        BOOST_TEST(result == 12345+678910);
    }

    {
        typedef vector<int> vector_type;
        vector_type v(12345);

        int n = fusion::accumulate(v, int_<0>(), count_ints());
        std::cout << n << std::endl;
        BOOST_TEST(n == 1);
    }

    {
        typedef vector<int, char, int, double, int> vector_type;
        vector_type v(12345, 'x', 678910, 3.36, 8756);

        int n = fusion::accumulate(v, int_<0>(), count_ints());
        std::cout << n << std::endl;
        BOOST_TEST(n == 3);
    }

    {
        typedef boost::mpl::vector<int, char, int, double, int> mpl_vec;
        int n = fusion::accumulate(mpl_vec(), int_<0>(), count_ints());
        std::cout << n << std::endl;
        BOOST_TEST(n == 3);
    }


    return boost::report_errors();
}