std::weakly_incrementable

 

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Technical Specifications

 

Iterator library

Iterator concepts
indirectly_readable (C++20) indirectly_writable (C++20) weakly_incrementable (C++20) incrementable (C++20) input_or_output_iterator (C++20) sentinel_for (C++20) sized_sentinel_for (C++20)	input_iterator (C++20) output_iterator (C++20) forward_iterator (C++20) bidirectional_iterator (C++20) random_access_iterator (C++20) contiguous_iterator (C++20)
Iterator primitives
iterator_traits input_iterator_tagoutput_iterator_tagforward_iterator_tagbidirectional_iterator_tagrandom_access_iterator_tagcontiguous_iterator_tag (C++20) iterator (deprecated in C++17)	incrementable_traits (C++20) indirectly_readable_traits (C++20) iter_value_titer_difference_titer_reference_titer_rvalue_reference_titer_common_reference_t (C++20)(C++20)(C++20)(C++20)(C++20)
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reverse_iterator move_iterator (C++11) move_sentinel (C++20) common_iterator (C++20) counted_iterator (C++20) back_insert_iterator front_insert_iterator insert_iterator	make_reverse_iterator (C++14) make_move_iterator (C++11) default_sentinel_tdefault_sentinel (C++20)(C++20) unreachable_sentinel_tunreachable_sentinel (C++20)(C++20) back_inserter front_inserter inserter
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istream_iterator ostream_iterator	istreambuf_iterator ostreambuf_iterator
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ranges::iter_move (C++20)
ranges::iter_swap (C++20)
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advance distance prev (C++11) next (C++11)	ranges::advance (C++20) ranges::distance (C++20) ranges::prev (C++20) ranges::next (C++20)
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begincbegin (C++11)(C++14) endcend (C++11)(C++14) sizessize (C++17)(C++20)	rbegincrbegin (C++14)(C++14) rendcrend (C++14)(C++14) empty (C++17) data (C++17)

 

Defined in header <iterator>
template<class I>   concept weakly_incrementable =     std::default_initializable<I> && std::movable<I> &&     requires(I i) {       typename std::iter_difference_t<I>;       requires /*is-signed-integer-like*/<std::iter_difference_t<I>>;       { ++i } -> std::same_as<I&>;   // not required to be equality-preserving       i++;                           // not required to be equality-preserving     };		(since C++20)

where /*is-signed-integer-like*/<I> is true if std::signed_­integral<I> is true or if I is a class that behaves like a signed integer type including all operators, implicit conversions, and std::numeric_limits specializations.

This concept specifies requirements on types that can be incremented with the pre- and post-increment operators, but those increment operations are not necessarily equality-preserving, and the type itself is not required to be std::equality_comparable.

Additionally, for any object i of type I, I satisfies std::weakly_incrementable only if

• The expressions ++i and i++ have the same domain
• If i is incrementable, then both ++i and i++ advance i
• If i is incrementable, then std::addressof(++i) == std::addressof(i)

For std::weakly_­incrementable types, a == b does not imply that ++a == ++b. Algorithms on weakly incrementable types must be single-pass algorithms. These algorithms can be used with istreams as the source of the input data through std::istream_iterator

See also

incrementable

specifies that the increment operation on a weakly_incrementable type is equality-preserving and that the type is equality_comparable (concept)