23 Iterators library [iterators]

23.5 Iterator adaptors [predef.iterators]

23.5.3 Move iterators and sentinels [move.iterators]

23.5.3.9 Class template move_­sentinel [move.sentinel]

1
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Class template move_­sentinel is a sentinel adaptor useful for denoting ranges together with move_­iterator.
When an input iterator type I and sentinel type S model sentinel_­for<S, I>, move_­sentinel<S> and move_­iterator<I> model sentinel_­for<move_­sentinel<S>, move_­iterator<I>> as well.
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[Example
:
A move_­if algorithm is easily implemented with copy_­if using move_­iterator and move_­sentinel: 
template<input_iterator I, sentinel_for<I> S, weakly_incrementable O,
         indirect_unary_predicate<I> Pred>
  requires indirectly_movable<I, O>
void move_if(I first, S last, O out, Pred pred) {
  std::ranges::copy_if(move_iterator<I>{first}, move_sentinel<S>{last}, out, pred);
}
— end example
]
namespace std {
  template<semiregular S>
  class move_sentinel {
  public:
    constexpr move_sentinel();
    constexpr explicit move_sentinel(S s);
    template<class S2>
      requires convertible_to<const S2&, S>
        constexpr move_sentinel(const move_sentinel<S2>& s);
    template<class S2>
      requires assignable_from<S&, const S2&>
        constexpr move_sentinel& operator=(const move_sentinel<S2>& s);

    constexpr S base() const;
  private:
    S last;     // exposition only
  };
}