cpp-useful-iterators/include/iterator/iterator_fwd.hpp

//
//  iterator_fwd.hpp
//  iterator
//
//  Created by Sam Jaffe on 2/18/17.
//

#pragma once

#include <iterator>
#include <utility>

namespace iterator {
  namespace detail {
    template <typename> struct void_t { using type = void; };

    template <typename IterType>
    using value_iterator = decltype(std::begin(*std::declval<IterType>()));

    template <typename IterType>
    using mapped_iterator =
        decltype(std::begin(std::declval<IterType>()->second));
  }

  struct {
  } in_place;
  using in_place_t = decltype(in_place);

  template <typename Iterator> class end_aware_iterator;
  template <typename MetaIterator> class joining_iterator;
  template <typename Iterator> class recursive_iterator;
  template <typename Iterator, std::size_t MaxDepth> class recursive_iterator_n;
}