std::iterator_traits<std::common_iterator>

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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)
bidirectional_iterator (C++20)
random_access_iterator (C++20)
contiguous_iterator (C++20)

Iterator primitives

input_iterator_tagoutput_iterator_tagforward_iterator_tagbidirectional_iterator_tagrandom_access_iterator_tagcontiguous_iterator_tag

(C++20)

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)
iterator_traits
incrementable_traits (C++20)
indirectly_readable_traits (C++20)

Algorithm concepts and utilities

Indirect callable concepts

indirectly_unary_invocableindirectly_regular_unary_invocable

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

indirect_unary_predicate (C++20)
indirect_binary_predicate (C++20)

indirect_equivalence_relation (C++20)
indirect_strict_weak_order (C++20)

Common algorithm requirements

indirectly_movable (C++20)
indirectly_movable_storable (C++20)
indirectly_copyable (C++20)

indirectly_copyable_storable (C++20)
indirectly_swappable (C++20)
indirectly_comparable (C++20)

permutable (C++20)
mergeable (C++20)
sortable (C++20)

(C++20)

(C++20)

(C++26)

reverse_iterator
make_reverse_iterator (C++14)
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)

front_insert_iterator
back_insert_iterator
inserter
insert_iterator
front_inserter
back_inserter
move_sentinel (C++20)

common_iterator (C++20)
counted_iterator (C++20)
basic_const_iterator (C++23)
const_iterator (C++23)
const_sentinel (C++23)
make_const_iterator (C++23)
make_const_sentinel (C++23)

Stream iterators

istream_iterator
ostream_iterator

istreambuf_iterator
ostreambuf_iterator

Iterator customization points
ranges::iter_move (C++20)
ranges::iter_swap (C++20)

Iterator operations

advance
distance
prev (C++11)
next (C++11)

ranges::advance (C++20)
ranges::distance (C++20)
ranges::prev (C++20)
ranges::next (C++20)

Range access

begincbegin (C++11)(C++14)
rbegincrbegin (C++14)(C++14)

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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std::common_iterator

Member functions
common_iterator::common_iterator
common_iterator::operator=
common_iterator::operator*common_iterator::operator->
common_iterator::operator++common_iterator::operator++(int)
Non-member functions
operator== (C++20)
operator- (C++20)
iter_move (C++20)
iter_swap (C++20)
Helper classes
incrementable_traits<std::common_iterator> (C++20)
iterator_traits<std::common_iterator> (C++20)

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Defined in header`<iterator>`
template<std::input_iterator I,class S> struct iterator_traits<std::common_iterator<I, S>>;		(since C++20)

Provides the uniform interface to the properties of thestd::common_iterator type.

[edit]Member types

Type name	Definition
`iterator_concept`	std::forward_iterator_tag, if`I` modelsstd::forward_iterator. std::input_iterator_tag otherwise.
`iterator_category` (conditionally present)	Not defined, ifstd::iter_difference_t<I> is not an integral type. std::forward_iterator_tag otherwise, ifstd::iterator_traits<I>::iterator_category is valid and denotes a type that modelsstd::derived_from<std::forward_iterator_tag>. std::input_iterator_tag otherwise.
`value_type`	std::iter_value_t<I>
`difference_type`	std::iter_difference_t<I>
`pointer`	decltype(c.operator->()), if it is well-formed (wherec is an lvalue of typeconststd::common_iterator<I, S>). void otherwise.
`reference`	std::iter_reference_t<I>

[edit]Example

Run this code

#include <iterator>#include <type_traits>#include <vector> int main(){std::vector v{1,2,3,4};using CV=std::common_iterator<std::counted_iterator<std::vector<int>::iterator>,std::default_sentinel_t>;    CV i{std::counted_iterator{v.begin(),3}};using TRCV=std::iterator_traits<decltype(i)>;    static_assert(std::is_same<TRCV::iterator_concept,std::forward_iterator_tag>());    static_assert(std::is_same<TRCV::iterator_category,std::forward_iterator_tag>());    static_assert(std::is_same<TRCV::value_type,int>());    static_assert(std::is_same<TRCV::difference_type,std::vector<int>::difference_type>());    static_assert(std::is_same<TRCV::pointer, decltype(i.operator->())>());    static_assert(std::is_same<TRCV::reference,int&>());     CV s{std::default_sentinel};using TRCS=std::iterator_traits<decltype(s)>;    static_assert(std::is_same<TRCS::iterator_concept,std::forward_iterator_tag>());    static_assert(std::is_same<TRCS::iterator_category,std::forward_iterator_tag>());    static_assert(std::is_same<TRCS::value_type,int>());    static_assert(std::is_same<TRCS::difference_type,std::vector<int>::difference_type>());    static_assert(std::is_same<TRCS::pointer, decltype(s.operator->())>());    static_assert(std::is_same<TRCS::reference,int&>());}

[edit]Defect reports

The following behavior-changing defect reports were applied retroactively to previously published C++ standards.

DR	Applied to	Behavior as published	Correct behavior
LWG 3749	C++20	ifstd::iter_difference_t<I> is not an integer type, `iterator_category` wasstd::input_iterator_tag	`iterator_category` is undefined in this case

[edit]See also

iterator_traits	provides uniform interface to the properties of an iterator (class template)[edit]
std::incrementable_traits<std::common_iterator> (C++20)	computes the associated difference type of thestd::common_iterator type (class template specialization)[edit]

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std::iterator_traits<std::common_iterator>

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