operator==(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
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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)

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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template<class I2,std::sentinel_for<I> S2> requiresstd::sentinel_for<S, I2> friendconstexprbool operator==(const common_iterator& x, conststd::common_iterator<I2, S2>& y);	(1)	(since C++20)
template<class I2,std::sentinel_for<I> S2> requiresstd::sentinel_for<S, I2>&&std::equality_comparable_with<I, I2> friendconstexprbool operator==(const common_iterator& x, conststd::common_iterator<I2, S2>& y);	(2)	(since C++20)

Compares the iterators and/or sentinels held by underlyingstd::variant member objectsvar. Two incomparable iterators or two sentinels are considered equal.

The behavior is undefined if eitherx ory is in an invalid state, i.e.x.var.valueless_by_exception()|| y.var.valueless_by_exception() is equal totrue.

Leti bex.var.index() andj bey.var.index().

1) Ifi== j (i.e. bothx andy hold iterators or both hold sentinels), returnstrue, otherwise returnsstd::get<i>(x.var)== std::get<j>(y.var).

2) Ifi==1&& j==1 (i.e. bothx andy hold sentinels), returnstrue, otherwise returnsstd::get<i>(x.var)== std::get<j>(y.var).

The!= operator issynthesized fromoperator==.

These function templates are not visible to ordinaryunqualified orqualified lookup, and can only be found byargument-dependent lookup when std::common_iterator<I> is an associated class of the arguments.

[edit]Parameters

x, y

iterator adaptors to compare

[edit]Return value

true if underlying iterators and/or sentinels are equal.

[edit]Example

Run this code

#include <cassert>#include <iterator> int main(){int a[]{0,1,2,3}; using CI=std::common_iterator<std::counted_iterator<int*>,std::default_sentinel_t>;     CI i1{std::counted_iterator{a+0,2}};    CI i2{std::counted_iterator{a+1,2}};    CI i3{std::counted_iterator{a+0,3}};    CI i4{std::counted_iterator{a+0,0}};    CI s1{std::default_sentinel};    CI s2{std::default_sentinel}; assert((i1== i2)==true);assert((i1== i3)==false);assert((i2== i3)==false);assert((s1== s2)==true);assert((i1== s1)==false);assert((i4== s1)==true);}