exercise-5-7.hpp

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// ===-- chapter-5/exercise-5-7.hpp ----------------------- -*- C++ -*- --=== //
#ifndef EXERCISE_5_7
#define EXERCISE_5_7
 
#include "exercise-5-6.hpp"
 
#include <boost/mpl/pop_back.hpp>
#include <boost/mpl/push_back.hpp>
 
 
namespace exercise_5_7 {
 
struct dimensions_b_tag { };
 
template <typename S>
struct dimensions_b_iterator
{
    typedef boost::mpl::bidirectional_iterator_tag category;
};
 
template <typename T, typename Next>
struct dimensions_b_impl
    : boost::mpl::void_
{
    typedef dimensions_b_tag tag;
 
    typedef boost::mpl::void_ next;
    typedef boost::mpl::void_ prev;
};
 
template <typename T, size_t N, typename Next>
struct dimensions_b_impl<T[N], Next>
    : boost::mpl::int_<N>
{
    typedef dimensions_b_tag tag;
 
    typedef Next next;
    typedef typename
        boost::mpl::if_<
            boost::is_array<T>,
            dimensions_b_impl< T, dimensions_b_impl<T[N], Next> >,
            boost::mpl::void_
        >::type prev;
};
 
template <typename T>
struct dimensions_b : dimensions_b_impl<T, boost::mpl::void_> { };
 
template <typename S, typename S_Prev>
struct begin_impl_traversal
    : begin_impl_traversal<S_Prev, typename S_Prev::prev> { };
 
template <typename S>
struct begin_impl_traversal<S, boost::mpl::void_>
{
    typedef S type;
};
 
} // namespace exercise_5_7
 
 
namespace boost {
namespace mpl {
 
 
// Implementation metaclasses:
 
template<>
struct begin_impl<exercise_5_7::dimensions_b_tag>
{
    template <typename S>
    struct apply
    {
        typedef exercise_5_7::dimensions_b_iterator<
            typename exercise_5_7::begin_impl_traversal<
                S,
                typename S::prev>::type
        > type;
    };
};
 
template<>
struct end_impl<exercise_5_7::dimensions_b_tag>
{
    template <typename S>
    struct apply
    {
        typedef exercise_5_7::dimensions_b_iterator<boost::mpl::void_> type;
    };
};
 
template<>
struct pop_back_impl<exercise_5_7::dimensions_b_tag>
{
    template <typename S> struct apply;
 
    template <typename T, size_t N>
    struct apply< exercise_5_7::dimensions_b<T[N]> >
    {
        typedef exercise_5_7::dimensions_b<T> type;
    };
};
 
template<>
struct push_back_impl<exercise_5_7::dimensions_b_tag>
{
    template <typename S, size_t N>
    struct apply_num { };
 
    // We only work with dimensions_b types...
    template <typename T, size_t N>
    struct apply_num< exercise_5_7::dimensions_b<T>, N>
    {
        typedef exercise_5_7::dimensions_b<T[N]> type;
    };
 
    template <typename S, typename Elem>
    struct apply : apply_num<S, Elem::value> { };
};
 
// Metafunction specializations
 
template <typename S>
struct deref< exercise_5_7::dimensions_b_iterator<S> > : S { };
 
template <typename S>
struct next< exercise_5_7::dimensions_b_iterator<S> >
{
    typedef exercise_5_7::dimensions_b_iterator<typename S::next> type;
};
 
template <typename S>
struct prior< exercise_5_7::dimensions_b_iterator<S> >
{
    typedef exercise_5_7::dimensions_b_iterator<typename S::prev> type;
};
 
 
} // namespace mpl
} // namespace boost
 
#endif // EXERCISE_5_7