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std::counted_iterator<I>::base

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< cpp‎ | iterator‎ | counted iterator

Compiler support

Freestanding and hosted

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

External libraries

Iterator library

Iterator concepts

indirectly_readable

(C++20)

indirectly_writable

(C++20)

weakly_incrementable

(C++20)

(C++20)

is-integer-like
is-signed-integer-like

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

(C++20)

sized_sentinel_for

(C++20)

(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)

(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)

(C++20)

(C++20)

(C++20)

indirect_result_t

(C++20)

(C++20)

projected_value_t

(C++26)

Iterator adaptors

reverse_iterator

make_reverse_iterator

(C++14)

(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

insert_iterator

(C++20)

common_iterator

(C++20)

counted_iterator

(C++20)

basic_const_iterator

(C++23)

(C++23)

(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

(C++11)

(C++11)

ranges::advance

(C++20)

ranges::distance

(C++20)

(C++20)

(C++20)

(C++11)(C++14)

(C++14)(C++14)

(C++11)(C++14)

(C++14)(C++14)

(C++17)(C++20)

(C++17)

(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)

(C++20)

(C++20)

operator-(default_sentinel_t)

(C++20)

(C++20)

(C++20)

iterator_traits<std::counted_iterator>

(C++20)

constexpr const 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.

Contents

[edit] Parameters

(none)

[edit] Return value

1) A reference to the underlying iterator.

2) An iterator move constructed from the underlying iterator.

[edit] Exceptions

May throw implementation-defined exceptions.

[edit] 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

[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 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

[edit] See also

operator*operator->

accesses the pointed-to element
(public member function) [edit]

returns the distance to the end
(public member function) [edit]

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