std::sized_sentinel_for,std::disable_sized_sentinel_for(3)

NAME
std::sized_sentinel_for,std::disable_sized_sentinel_for - std::sized_sentinel_for,std::disable_sized_sentinel_for

Synopsis
   Defined in header <iterator>
   template< class S, class I >
       concept sized_sentinel_for =
           std::sentinel_for<S, I> &&
           !std::disable_sized_sentinel_for<std::remove_cv_t<S>,
                        std::remove_cv_t<I>> && (1) (since C++20)
           requires(const I& i, const S& s) {
               { s - i } -> std::same_as<std::iter_difference_t<I>>;
               { i - s } -> std::same_as<std::iter_difference_t<I>>;
           };
   template< class S, class I > (2) (since C++20)
       inline constexpr bool disable_sized_sentinel_for = false;
   1) The sized_sentinel_for concept specifies that an object of the iterator type I
   and an object of the sentinel type S can be subtracted to compute the distance
   between them in constant time.
   2) The disable_sized_sentinel_for variable template can be used to prevent iterators
   and sentinels that can be subtracted but do not actually model sized_sentinel_for
   from satisfying the concept.
   A program may specialize disable_sized_sentinel_for for cv-unqualified non-array
   object type S and I, as long as at least one of which is a program-defined type.
   Such specializations are usable in constant expressions and have type const bool.

See also
   ranges::sized_range specifies that a range knows its size in constant time
   (C++20) (concept)
   ranges::size returns an integer equal to the size of a range
   (C++20) (customization point object)