std::sentinel_for

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Iterator library

Iterator concepts

indirectly_readable (C++20)
indirectly_writable (C++20)
weakly_incrementable (C++20)
incrementable (C++20)
is-integer-like is-signed-integer-like (C++20)(C++20)

sentinel_for (C++20)
sized_sentinel_for (C++20)
input_iterator (C++20)
output_iterator (C++20)
input_or_output_iterator (C++20)

forward_iterator (C++20)
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iter_value_titer_difference_titer_reference_titer_const_reference_titer_rvalue_reference_titer_common_reference_t

(C++20)(C++20)(C++20)(C++23)(C++20)(C++20)

iterator (deprecated in C++17)
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(C++20)(C++20)

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(C++20)

(C++20)

(C++26)

reverse_iterator
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move_iterator (C++11)
make_move_iterator (C++11)
default_sentinel_tdefault_sentinel (C++20)(C++20)
unreachable_sentinel_tunreachable_sentinel (C++20)(C++20)

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make_const_sentinel (C++23)

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endcend (C++11)(C++14)
rendcrend (C++14)(C++14)

sizessize (C++17)(C++20)
empty (C++17)
data (C++17)

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Defined in header`<iterator>`
template<class S,class I> concept sentinel_for= std::semiregular<S>&& std::input_or_output_iterator<I>&& __WeaklyEqualityComparableWith<S, I>;		(since C++20)

Thesentinel_for concept specifies the relationship between aninput_or_output_iterator type and asemiregular type whose values denote a range. The exposition-only concept__WeaklyEqualityComparableWith is described inequality_comparable.

[edit]Semantic requirements

Lets andi be values of typeS andI, respectively, such that[i, s) denotes arange.sentinel_for<S, I> is modeled only if:

i== s is well-defined.
Ifbool(i!= s) theni 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 iteratori and sentinels such that[i, s) denotes a range andi!= s,[i, s) is not required to continue to denote a range after incrementing any iterator equal toi (and soi== s is no longer required to be well-defined after such an increment).

[edit]Notes

A sentinel type and its corresponding iterator type are not required to modelequality_comparable_with, because the sentinel type may not be comparable 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 therange-basedfor loop since C++17.