cpp-useful-iterators/iterator_fwd.hpp

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

#pragma once

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));
  }
}