check_finite_iterable.hpp

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#ifndef BOOST_MPL11_TEST_CHECK_FINITE_ITERABLE_HPP
#define BOOST_MPL11_TEST_CHECK_FINITE_ITERABLE_HPP

#include <boost/mpl11/fwd/comparable.hpp>
#include <boost/mpl11/fwd/iterable.hpp>
#include <boost/mpl11/integer.hpp>

#include "minimal_iterable.hpp"
#include "static_assert.hpp"


namespace check_finite_iter_detail {
    using namespace boost::mpl11;
    using boost::mpl11::size_t;

    template <typename x, typename y,
        typename Expected = typename x::type,
        typename Actual = typename y::type>
    using assert_eq = static_assert_<equal<x, y>>;

    template <typename reference, typename iter,
        typename index = size_t<0>,
        bool = is_empty<reference>::value>
    struct impl;

    template <typename reference, typename iter>
    struct impl<reference, iter, size_t<length<reference>::value>, false>
        : assert_eq<head<reference>, head<iter>>
        , assert_eq<tail<reference>, tail<iter>>
        , assert_eq<is_empty<reference>, is_empty<iter>>

        , assert_eq<last<reference>, last<iter>>
        , assert_eq<length<reference>, length<iter>>
    { };

    template <typename reference, typename iter, typename index>
    struct impl<reference, iter, index, false>
        : assert_eq<at<index, reference>, at<index, iter>>
        , impl<reference, iter, size_t<index::type::value + 1>>
    { };

    template <typename reference, typename iter, typename index>
    struct impl<reference, iter, index, true>
        : static_assert_<is_empty<iter>>
        , assert_eq<size_t<0>, length<iter>>
    { };
} // end namespace check_finite_iter_detail


template <typename iter, typename ...xs>
using check_finite_iterable =
    check_finite_iter_detail::impl<minimal_iterable<xs...>, iter>;

#endif // !BOOST_MPL11_TEST_CHECK_FINITE_ITERABLE_HPP