std::sentinel_for(3) C++ Standard Libary std::sentinel_for(3) NAME std::sentinel_for - std::sentinel_for Synopsis Defined in header <iterator> template< class S, class I > concept sentinel_for = std::semiregular<S> && (since C++20) std::input_or_output_iterator<I> && __WeaklyEqualityComparableWith<S, I>; The sentinel_for concept specifies the relationship between an input_or_output_iterator type and a semiregular type whose values denote a range. The exposition-only concept __WeaklyEqualityComparableWith is described in equality_comparable. Semantic requirements Let s and i be values of type S and I, respectively, such that [i, s) denotes a range. sentinel_for<S, I> is modeled only if: * i == s is well-defined. * If bool(i != s) then i is dereferenceable and [++i, s) denotes a range. * std::assignable_from<I&, S> is either modeled or not satisfied. The domain of == can change over time. Given an iterator i and sentinel s such that [i, s) denotes a range and i != s, [i, s) is not required to continue to denote a range after incrementing any iterator equal to i (and so i == s is no longer required to be well-defined after such an increment). Notes A sentinel type and its corresponding iterator type are not required to model equality_comparable_with, because the sentinel type may not be compara- ble with itself, and they are not required to have a common reference type. It has been permitted to use a sentinel type different from the iterator type in the range-based for loop since C++17. Defect reports The following behavior-changing defect reports were applied retroac- tively to previously published C++ standards. DR Applied to Behavior as published Cor- rect behavior LWG 3453 C++20 semantic requirements for sentinel_for were too strengthened loose for ranges::advance http://cppreference.com 2024.06.10 std::sentinel_for(3)
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