< cpp‎ | iterator
Iterator library
Iterator concepts
Iterator primitives
Algorithm concepts and utilities
Indirect callable concepts
Common algorithm requirements
Iterator adaptors
Stream iterators
Iterator customization points
Iterator operations
Range access
Defined in header <iterator>
template< std::input_iterator Iter >
class basic_const_iterator;
(since C++23)

std::basic_const_iterator is an iterator adaptor which behaves exactly like the underlying iterator (which must be at least an LegacyInputIterator or model input_iterator), except that dereferencing converts the value returned by the underlying iterator as immutable. Specializations of std::basic_const_iterator are constant iterators, that is, the iterator can never be used as an output iterator because modifying elements is not allowed.


[edit] Member types

Member type Definition

If Iter models forward_iterator:

Otherwise, there is no member iterator_category.

value_type std::iter_value_t<Iter>
difference_type std::iter_difference_t<Iter>
reference (private) std::iter_const_reference_t<Iter>
(exposition-only member type*)

[edit] Member objects

Member name Definition
current (private) the underlying iterator from which base() copies or moves
(exposition-only member object*)

[edit] Member functions

constructs a new iterator adaptor
(public member function) [edit]
assigns another iterator adaptor
(public member function) [edit]
accesses the underlying iterator
(public member function) [edit]
accesses the pointed-to element
(public member function) [edit]
accesses an element by index
(public member function) [edit]
advances or decrements the iterator
(public member function) [edit]

[edit] Non-member functions

compares the underlying iterators
(function template) [edit]
advances the iterator
(function template) [edit]
computes the distance between two iterator adaptors
(function template) [edit]
casts the result of dereferencing the underlying iterator to its associated rvalue reference type
(function) [edit]

[edit] Helper classes

determines the common type of an iterator and an adapted basic_const_iterator type
(class template specialization) [edit]

[edit] Helper alias templates

template< std::input_iterator I >
using const_iterator = /* see description */;
(since C++23)

If I models constant-iterator (an exposition-only concept), then const_iterator<I> denotes a type I. Otherwise, basic_const_iterator<I>.

template< std::semiregular S >
using const_sentinel = /* see description */;
(since C++23)

If S models input_iterator, then const_sentinel<S> denotes a type const_iterator<S>. Otherwise, S.

[edit] Helper function templates

template< std::input_iterator T >
constexpr const_iterator<T> make_const_iterator( I it ) { return it; }
(since C++23)
template< std::semiregular S >
constexpr const_sentinel<S> make_const_sentinel( S s ) { return s; }
(since C++23)

[edit] Example