std::iterator_traits<std::counted_iterator>

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Compiler support
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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
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External libraries

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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::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)

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Defined in header`<iterator>`
template<std::input_iterator I> requires/* see below */ struct iterator_traits<std::counted_iterator<I>>:std::iterator_traits<I>{ using pointer=std::conditional_t<std::contiguous_iterator<I>, std::add_pointer_t<std::iter_reference_t<I>>, void>; };		(since C++20)

Inherits the properties from customized (generated from either a standard partial specialization or a program-defined specialization)std::iterator_traits, with the member typepointer adjusted, whereI modelsinput_iterator.

Notably, theiterator_concept (if present) anditerator_category are inherited fromstd::iterator_traits.

The condition in the requires-clause istrue if and only ifstd::iterator_traits is not generated from the primary template.

[edit]Note

BeforeP2259R1, this specialization is used even ifstd::iterator_traits is generated from the primary template. As a result, when testingstd::counted_iterator against an iterator concept (e.g.forward_iterator), the determination of/*ITER_CONCEPT*/ does not takeI::iterator_concept into account, and thusstd::counted_iterator sometimes erroneously behaves as if it cannot model that concept. This incorrect behavior is implemented in libstdc++ prior to 10.4, and in MSVC STL prior to VS 2022 17.0 Preview 3.

The standard library provides partial specializations ofstd::iterator_traits for pointer types,std::counted_iterator, andstd::common_iterator.

[edit]Example

Run this code

#include <iterator>#include <list>#include <type_traits>#include <vector> int main(){std::vector v{1,2,3,4};std::list l{1,2,3,4};std::counted_iterator iv{v.begin(),3};std::counted_iterator il{l.begin(),3};    static_assert(std::is_same<int*,std::iterator_traits<decltype(iv)>::pointer>());    static_assert(std::is_same<void,std::iterator_traits<decltype(il)>::pointer>());}