mirror/meta_prog/before.hpp

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#ifndef MIRROR_META_PROG_BEFORE_1107061248_HPP
#define MIRROR_META_PROG_BEFORE_1107061248_HPP


#include <mirror/meta_prog/range.hpp>
#include <mirror/meta_prog/traits.hpp>

MIRROR_NAMESPACE_BEGIN
namespace mp {

#ifdef MIRROR_DOCUMENTATION_ONLY


template <typename Range, typename Type>
struct before
{
    typedef Range type;
};
#endif

// specialization of before for other expressions
template <typename X, typename T>
struct before
{
    MIRROR_ASSERT_RETURNS_RANGE(X);
    typedef typename before<typename X::type, T>::type type;
};

// specialization of before for empty ranges
template <typename T>
struct before<range<>, T>
{
    typedef range<> type;
};

namespace aux {

template <typename Result, typename Range, typename T>
struct bfr_hlpr;

template <typename ... R, typename ... P, typename T>
struct bfr_hlpr<
    mirror::mp::range<R...>,
    mirror::mp::range<T, P...>,
    T
>
{
    typedef mirror::mp::range<R...> type;
};

template <typename ... R, typename L, typename ... P, typename T>
struct bfr_hlpr<
    mirror::mp::range<R...>,
    mirror::mp::range<L, P...>,
    T
>
{
    typedef typename bfr_hlpr<
        mirror::mp::range<R..., L>,
        mirror::mp::range<P...>,
        T
    >::type type;
};

template <typename ... R, typename T>
struct bfr_hlpr<
    mirror::mp::range<R...>,
    mirror::mp::range<>,
    T
>
{
    typedef mirror::mp::range<R...> type;
};

} // namespace aux

template <typename H, typename ... P, typename T>
struct before<range<H, P...>, T>
{
    typedef typename mirror::mp::aux::bfr_hlpr<
        mirror::mp::range<>,
        mirror::mp::range<H, P...>,
        T
    >::type type;
};

} // namespace mp
MIRROR_NAMESPACE_END

#endif //include guard