23 Ranges library [ranges]

23.7 Range adaptors [range.adaptors]

23.7.5 Transform view [range.transform]

23.7.5.4 Class template transform_­view​::​sentinel [range.transform.sentinel]

namespace std::ranges {
  template<class V, class F>
  template<bool Const>
  class transform_view<V, F>::sentinel {
  private:
    using Parent =                                      // exposition only
      conditional_t<Const, const transform_view, transform_view>;
    using Base = conditional_t<Const, const V, V>;      // exposition only
    sentinel_t<Base> end_ = sentinel_t<Base>();         // exposition only
  public:
    sentinel() = default;
    constexpr explicit sentinel(sentinel_t<Base> end);
    constexpr sentinel(sentinel<!Const> i)
      requires Const && ConvertibleTo<sentinel_t<V>, sentinel_t<Base>>;

    constexpr sentinel_t<Base> base() const;

    friend constexpr bool operator==(const iterator<Const>& x, const sentinel& y);
    friend constexpr bool operator==(const sentinel& x, const iterator<Const>& y);
    friend constexpr bool operator!=(const iterator<Const>& x, const sentinel& y);
    friend constexpr bool operator!=(const sentinel& x, const iterator<Const>& y);

    friend constexpr iter_difference_t<iterator_t<Base>>
      operator-(const iterator<Const>& x, const sentinel& y)
        requires SizedSentinel<sentinel_t<Base>, iterator_t<Base>>;
    friend constexpr iter_difference_t<iterator_t<Base>>
      operator-(const sentinel& y, const iterator<Const>& x)
        requires SizedSentinel<sentinel_t<Base>, iterator_t<Base>>;
  };
}