cpp-lazy-stream/include/stream/ref_view.h

#pragma once

#include <iterator>

#include <stream/forward.h>
#include <stream/owning_view.h>

namespace stream::ranges {
template <typename It> class ref_view {
private:
  It begin_;
  It end_;

public:
  ref_view(It begin, It end) : begin_(begin), end_(end) {}
  template <typename C>
  ref_view(C & container)
      : begin_(std::begin(container)), end_(std::end(container)) {}

  auto begin() const { return end_aware_iterator(begin_, end_); }
  auto end() const { return end_aware_iterator<It>(); }
  bool empty() const { return begin_ == end_; }
  size_t size() const { return std::distance(begin_, end_); }
};

template <typename It> ref_view(It, It) -> ref_view<It>;
template <typename C> ref_view(C &) -> ref_view<iter<C>>;
}

namespace stream::ranges::views {
template <typename C> auto all(C & container) { return ref_view(container); }
template <typename C> auto all(C const & container) {
  return ref_view(container);
}
template <typename C> auto all(C && container) {
  return owning_view(std::move(container));
}
}