expect.hpp

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#ifndef BOOST_MPL11_DETAIL_TEST_EXPECT_HPP
#define BOOST_MPL11_DETAIL_TEST_EXPECT_HPP

#include <boost/mpl11/detail/dependent.hpp>
#include <boost/mpl11/detail/std_size_t.hpp>
#include <boost/mpl11/functional.hpp>
#include <boost/mpl11/fwd/comparable.hpp>
#include <boost/mpl11/logical.hpp>


namespace boost { namespace mpl11 { namespace detail {
    template <typename ...xs>
    struct instantiate {
        // We avoid empty arrays by adding a dummy 0.
        static constexpr std_size_t go[] = {0, sizeof(xs)...};

        using type = instantiate;
    };

    template <typename ...xs>
    struct show {
        static_assert(dependent<xs...>::value(false), "");
    };

    template <typename expr>
    struct expect {
        template <template <typename ...> class Bool>
        struct _to {
            template <typename r, bool =
                Bool<equal<expr, r>>::value &&
                !Bool<not_equal<expr, r>>::value
            >
            struct eq { };

            template <typename r>
            struct eq<r, false>
                : show<expr, r>,
                  show<typename expr::type, typename r::type>
            { };

            template <typename predicate>
            struct satisfy {
                static_assert(Bool<
                    typename predicate::type::template apply<expr>
                >::value, "");
            };

            template <typename comparison>
            struct be {
                template <typename r, bool = Bool<
                    typename comparison::type::template apply<expr, r>
                >::value>
                struct than { };

                template <typename r>
                struct than<r, false>
                    : show<expr, r>
                    , show<typename expr::type, typename r::type>
                { };

                template <typename r>
                using with = than<r>;
            };

            template <template <typename ...> class f>
            using be_ = be<lift<f>>;
        };

        using to = _to<id>;
        using not_to = _to<not_>;

        template <typename r>
        using to_eq = typename to::template eq<r>;

        template <typename pred>
        using to_satisfy = typename to::template satisfy<pred>;
    };
}}} // end namespace boost::mpl11::detail

#endif // !BOOST_MPL11_DETAIL_TEST_EXPECT_HPP