operator==,<=>(std::counted_iterator)

 

C++

Compiler support

Freestanding and hosted

Language

Standard library

Standard library headers

Named requirements

Feature test macros(C++20)

Language support library

Concepts library(C++20)

Diagnostics library

Memory management library

Metaprogramming library(C++11)

General utilities library

Containers library

Iterators library

Ranges library(C++20)

Algorithms library

Strings library

Text processing library

Numerics library

Date and time library

Input/output library

Filesystem library(C++17)

Concurrency support library(C++11)

Execution control library(C++26)

Technical specifications

Symbols index

External libraries

 

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)
Utilities
indirect_result_t (C++20)	projected (C++20)	projected_value_t (C++26)
Iterator adaptors
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)

 

std::counted_iterator

Member functions

counted_iterator::counted_iterator

counted_iterator::operator=

counted_iterator::base

counted_iterator::count

counted_iterator::operator*counted_iterator::operator->

counted_iterator::operator[]

counted_iterator::operator++counted_iterator::operator++(int)counted_iterator::operator+counted_iterator::operator+=counted_iterator::operator--counted_iterator::operator--(int)counted_iterator::operator-counted_iterator::operator-=

Non-member functions

operator==operator<=> (C++20)(C++20)

operator==(default_sentinel_t) (C++20)

operator+ (C++20)

operator- (C++20)

operator-(default_sentinel_t) (C++20)

iter_move (C++20)

iter_swap (C++20)

Helper classes

iterator_traits<std::counted_iterator> (C++20)

 

template<std::common_with<I> I2 >     friendconstexprbool operator==(         const counted_iterator& x, const counted_iterator<I2>& y );	(1)	(since C++20)
template<std::common_with<I> I2 >     friendconstexpr strong_ordering operator<=>(         const counted_iterator& x, const counted_iterator<I2>& y );	(2)	(since C++20)

Compares the underlying lengths (i.e. distances to the end).

1) Checks if the underlying lengths are equal.

2) Compares the underlying lengths with operator <=>.

The behavior is undefined if x and y do not point to elements of the same sequence. That is, there must exist some n such that std::next(x.base(), x.count()+ n) and std::next(y.base(), y.count()+ n) refer to the same element.

The <, <=, >, >=, and != operators are synthesized from operator<=> and operator== respectively.

This function template is not visible to ordinary unqualified or qualified lookup, and can only be found by argument-dependent lookup when std::counted_iterator<I> is an associated class of the arguments.

Parameters

x, y

-

iterator adaptors

Return value

1)x.count()== y.count()

2)y.count()<=> x.count()

Notes

Since the length counts down, not up, the order of the arguments of operator<=> in the underlying comparison expression is reversed, i.e. y is lhs, x is rhs.

Example

Run this code

#include <initializer_list>#include <iterator>   int main(){staticconstexprauto v ={1, 2, 3, 4, 5, 6};constexprstd::counted_iterator<std::initializer_list<int>::iterator> it1{v.begin(), 5}, it2{v.begin(), 5}, it3{v.begin()+1, 4}, it4{v.begin(), 0}; static_assert(it1 == it2); static_assert(it2 != it3); static_assert(it2 < it3); static_assert(it1 <= it2); static_assert(it3 !=std::default_sentinel); static_assert(it4 ==std::default_sentinel);   // it2 == std::counted_iterator{v.begin(), 4}; // UB: operands do not refer to// elements of the same sequence}

See also

operator==(std::default_sentinel) (C++20)	checks if the distance to the end is equal to ​0​ (function template)
operator+ (C++20)	advances the iterator (function template)
operator- (C++20)	computes the distance between two iterator adaptors (function template)