cpp-lazy-stream/include/stream/view/subrange.h

#pragma once

#include <iterator>

#include <iterator/detail/facade_traits.h>
#include <stream/forward.h>

#include <iterator/detail/macro.h>

namespace stream::ranges {
template <typename It, typename S = It> class subrange {
private:
  It begin_;
  S end_;

public:
  subrange(It begin, S end) : begin_(begin), end_(end) {}
  template <typename C, REQUIRES(detail::is_container_v<C>)>
  subrange(C && container)
      : subrange(std::begin(container), std::end(container)) {
    // TODO: permissible dangling
    static_assert(std::is_reference_v<C>,
                  "Cannot access iterator of a temporary");
  }

  auto begin() const { return begin_; }
  auto end() const { return end_; }
  bool empty() const { return begin_ == end_; }
  SFINAE(detail::has_distance_to_v<It>, size_t) size() const {
    return end_ - begin_;
  }
};

template <typename It, typename S> subrange(It, S) -> subrange<It, S>;
template <typename C>
subrange(C &&) -> subrange<detail::begin_t<C>, detail::end_t<C>>;
}

#include <iterator/detail/undef.h>