cpp-useful-iterators/include/iterator/end_aware_iterator.h

//
//  end_aware_iterator.h
//  iterator
//
//  Created by Sam Jaffe on 2/7/17.
//

#pragma once

#include <iterator/detail/traits.h>
#include <iterator/facade.h>
#include <iterator/forwards.h>
#include <iterator/sentinel.h>

namespace iterator {
/**
 * @class end_aware_iterator
 * @brief An iterator that keeps track of the relative end of the range.
 *
 * @tparam It The underlying iterator type
 */
template <typename It>
class end_aware_iterator : public facade<end_aware_iterator<It>> {
public:
  using sentinel_type = sentinel_t;

public:
  end_aware_iterator() = default;
  end_aware_iterator(It it, It end) : curr_(it), end_(end) {}

  template <typename C, typename = std::enable_if_t<detail::is_container_v<C>>>
  end_aware_iterator(C && container)
      : curr_(std::begin(container)), end_(std::end(container)) {
    static_assert(std::is_reference_v<C>,
                  "Cannot access iterator of a temporary");
  }

  template <typename Ot>
  end_aware_iterator(end_aware_iterator<Ot> const & other)
      : curr_(other.curr_), end_(other.end_) {}

  end_aware_iterator(end_aware_iterator<It> other, end_aware_iterator<It>)
      : curr_(other.curr_), end_(other.end_) {}

  decltype(auto) dereference() const { return *curr_; }
  void increment() {
    if (!at_end()) { ++curr_; }
  }
  bool at_end() const { return curr_ == end_; }
  bool equal_to(end_aware_iterator const & other) const {
    return curr_ == other.curr_;
  }

private:
  template <typename O> friend class end_aware_iterator;
  It curr_, end_;
};

template <typename C>
end_aware_iterator(C &&) -> end_aware_iterator<detail::iter<C>>;
template <typename It> end_aware_iterator(It, It) -> end_aware_iterator<It>;
template <typename It>
end_aware_iterator(end_aware_iterator<It>, end_aware_iterator<It>)
    -> end_aware_iterator<It>;
}

MAKE_ITERATOR_FACADE_TYPEDEFS_T(::iterator::end_aware_iterator);