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

//
//  capture_iterator.h
//  iterator
//
//  Created by Sam Jaffe on 4/1/23.
//  Copyright © 2023 Sam Jaffe. All rights reserved.
//

#pragma once

#include <iterator/forwards.h>
#include <iterator/proxy.h>

namespace iterator {
template <typename It>
class CaptureIterator : public Proxy<It, CaptureIterator<It>> {
public:
  using super_t = Proxy<It, CaptureIterator<It>>;
  using value_type = typename std::iterator_traits<It>::value_type;
  using difference_type = typename std::iterator_traits<It>::difference_type;

private:
  value_type cache_;

public:
  CaptureIterator() = default;
  CaptureIterator(It it) : super_t(it) { cache_ = super_t::dereference(); }

  value_type const & dereference() const { return cache_; }

  void increment()
    requires(forward<super_t>)
  {
    super_t::increment();
    cache_ = super_t::dereference();
  }

  void decrement()
    requires(bidirectional<super_t>)
  {
    super_t::decrement();
    cache_ = super_t::dereference();
  }

  void advance(difference_type off)
    requires(random_access<super_t>)
  {
    super_t::advance(off);
    cache_ = super_t::dereference();
  }
};

template <typename It> CaptureIterator(It) -> CaptureIterator<It>;

}