# std::experimental::ranges::Sentinel

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< cpp‎ | experimental‎ | ranges

Defined in header `<experimental/ranges/iterator>` |  |
template < class S, class I > concept bool Sentinel = Semiregular <S> && Iterator <I> && WeaklyEqualityComparableWith <S, I>; |  | (ranges TS)

The `Sentinel` concept specifies the relationship between an `Iterator` type and a `Semiregular` type whose values denote a range.

Let `s` and `i` be values of type `S` and `I`, respectively, such that `[i, s)` denotes a range. `Sentinel<S, I>` is satisfied only if:

- i == s is well-defined.
- If bool(i != s) then `i` is dereferenceable and `[++i, s)` denotes a range.

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).

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