std::counted_iterator<I>::base

 

C++

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Feature test macros(C++20)

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Concepts library(C++20)

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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)
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)

 

constexprconst I& base()const&noexcept;	(1)	(since C++20)
constexpr I base()&&;	(2)	(since C++20)

Returns the underlying base iterator.

1) Returns a reference to the underlying iterator.

2) Move constructs the return value from the underlying iterator.

Parameters

(none)

Return value

1) A reference to the underlying iterator.

2) An iterator move constructed from the underlying iterator.

Exceptions

May throw implementation-defined exceptions.

Example

Run this code

#include <algorithm>#include <iostream>#include <iterator>#include <type_traits>#include <vector>   int main(){std::vector<int> v{0, 1, 2, 3, 4};   std::reverse_iterator<std::vector<int>::iterator> reverse{v.rbegin()};   std::counted_iterator counted{reverse, 3};   static_assert(std::is_same< decltype(counted.base()), std::reverse_iterator<std::vector<int>::iterator>const&>{});   std::cout<<"Print with reverse_iterator: ";for(auto r = counted.base(); r != v.rend();++r)std::cout<<*r <<' ';std::cout<<'\n';   std::cout<<"Print with counted_iterator: ";for(; counted !=std::default_sentinel;++counted)std::cout<< counted[0]<<' ';std::cout<<'\n';}

Output:

Print with reverse_iterator: 4 3 2 1 0 Print with counted_iterator: 4 3 2

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 3391	C++20	the const version of base returns a copy of the underlying iterator	returns a reference
LWG 3593	C++20	the const version of base returns a reference but might not be noexcept	made noexcept

See also

operator*operator->	accesses the pointed-to element (public member function)
count	returns the distance to the end (public member function)