std::ranges::concat_view<Views...>::iterator

 

C++

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Standard library

Standard library headers

Named requirements

Feature test macros (C++20)

Language support library

Concepts library (C++20)

Metaprogramming library (C++11)

Diagnostics library

General utilities library

Strings library

Containers library

Iterators library

Ranges library (C++20)

Algorithms library

Numerics library

Localizations library

Input/output library

Filesystem library (C++17)

Regular expressions library (C++11)

Concurrency support library (C++11)

Execution support library (C++26)

Technical specifications

Symbols index

External libraries

 

Ranges library

Range access begin cbegin   end cend rbegin crbegin   rend crend size ssize   data cdata empty

Range conversions std::from_range_t std::from_range (C++23)(C++23)     to (C++23)

Dangling iterator handling dangling borrowed_iterator_t borrowed_subrange_t

Range primitives
range_size_trange_difference_trange_value_t elements_of (C++23)	iterator_tconst_iterator_tsentinel_tconst_sentinel_t (C++23)(C++23)	range_reference_trange_const_reference_trange_rvalue_reference_trange_common_reference_t (C++23)

Range concepts
range borrowed_range    sized_range	common_range view viewable_range	input_range output_range forward_range	bidirectional_range    random_access_range contiguous_range	constant_range (C++23)

Views
view_interface	subrange

Range factories
empty_viewviews::empty	single_viewviews::single	basic_istream_viewviews::istream	iota_viewviews::iota	repeat_viewviews::repeat (C++23)(C++23)

Range adaptors
views::all_tviews::all ref_view owning_view as_rvalue_viewviews::as_rvalue (C++23)(C++23)   filter_viewviews::filter transform_viewviews::transform take_viewviews::take take_while_viewviews::take_while concat_viewviews::concat (C++26)(C++26)	drop_viewviews::drop drop_while_viewviews::drop_while join_viewviews::join join_with_viewviews::join_with (C++23)(C++23)   lazy_split_viewviews::lazy_split split_viewviews::split views::counted common_viewviews::common	reverse_viewviews::reverse as_const_viewviews::as_const (C++23)(C++23) elements_viewviews::elements keys_viewviews::keys values_viewviews::values enumerate_viewviews::enumerate (C++23)(C++23) zip_viewviews::zip (C++23)(C++23) zip_transform_viewviews::zip_transform (C++23)(C++23)	adjacent_viewviews::adjacent (C++23)(C++23) views::pairwise (C++23) adjacent_transform_viewviews::adjacent_transform (C++23)(C++23) views::pairwise_transform (C++23) chunk_viewviews::chunk (C++23)(C++23) slide_viewviews::slide (C++23)(C++23) chunk_by_viewviews::chunk_by (C++23)(C++23) stride_viewviews::stride (C++23)(C++23) cartesian_product_viewviews::cartesian_product (C++23)(C++23)

Range generators std::generator (C++23)

Range adaptor closure objects range_adaptor_closure (C++23)

Range adaptor objects

Helper items
copyable-box movable-box (until C++23)  (C++23)	simple-view non-propagating-cache

 

std::ranges::concat_view

Member functions

concat_view::concat_view

concat_view::begin

concat_view::end

concat_view::size

Deduction guides

Iterator

Member functions

concat_view::iterator::iterator

concat_view::iterator::operator*

concat_view::iterator::operator[]

concat_view::iterator::operator++ concat_view::iterator::operator++(int) concat_view::iterator::operator-- concat_view::iterator::operator--(int) concat_view::iterator::operator+= concat_view::iterator::operator-=

concat_view::iterator::satisfy concat_view::iterator::prev concat_view::iterator::advance-fwd concat_view::iterator::advance-bwd

Non-member functions

operator==(concat_view::iterator) operator<(concat_view::iterator) operator>(concat_view::iterator) operator<=(concat_view::iterator) operator>=(concat_view::iterator) operator<=>(concat_view::iterator)

operator+(concat_view::iterator) operator-(concat_view::iterator)

iter_move(concat_view::iterator)

iter_swap(concat_view::iterator)

 

template< bool Const > class /*iterator*/	(1)	(exposition only*)
Helper concepts
template< bool Const, class... Rs > concept /*concat-is-random-access*/ = /* see description */;	(2)	(exposition only*)
template< bool Const, class... Rs > concept /*concat-is-bidirectional*/ = /* see description */;	(3)	(exposition only*)

1) ranges::concat_view<Views...>::iterator is the type of the iterators returned by begin() and end() of ranges::concat_view<Views...>.

2) Let Fs be the pack that consists of all elements of Rs except the last element. Equivalent to

template<bool Const, class... Rs>
concept concat-is-random-access = // exposition only
    all-random-access <Const, Rs...> &&
    (ranges::common_range<maybe-const <Const, Fs>> && ...);

.

3) Let Fs be the pack that consists of all elements of Rs except the last element. Equivalent to

template<bool Const, class... Rs>
concept concat-is-bidirectional = // exposition only
    all-bidirectional <Const, Rs...> &&
    (ranges::common_range<maybe-const <Const, Fs>> && ...);

.

Template parameters

Const

-

whether the iterator is a constant iterator

Nested types

Exposition-only types
Type	Definition
base-iter	std::variant<ranges::iterator_t<maybe-const <Const, Views>>...> (exposition-only member type*)
Iterator property types
Type	Definition
iterator_concept	an iterator tag, see below
iterator_category (conditionally present)	an iterator tag, see below
value_type	concat-value-t <maybe-const <Const, Views>...>
difference_type	std::common_type_t<ranges::range_difference_t<maybe-const <Const, Views>>...>

Determining the iterator concept

iterator_concept is defined as follows:

• If concat-is-random-access <Const, Views...> is modeled, iterator_concept denotes std::random_access_iterator_tag.
• Otherwise, if concat-is-bidirectional <Const, Views...> is modeled, iterator_concept denotes std::bidirectional_iterator_tag.
• Otherwise, if all-forward <Const, Views...> is modeled, iterator_concept denotes std::forward_iterator_tag.
• Otherwise, iterator_concept denotes std::input_iterator_tag.

Determining the iterator category

iterator_category is defined if and only if all-forward <Const, Views...> is modeled. In this case, it is defined as follows:

• If std::is_reference_v<concat-reference-t <maybe-const <Const, Views>...>> is false, iterator_category denotes std::input_iterator_tag.
• Otherwise, let Cs denote the pack of types std::iterator_traits<ranges::iterator_t<maybe-const <Const, Views>>>::iterator_category...:
  • If (std::derived_from<Cs, std::random_access_iterator_tag> && ...) &&
        concat-is-random-access <Const, Views...> is true, iterator_category denotes std::random_access_iterator_tag.
  • Otherwise, if (std::derived_from<Cs, std::bidirectional_iterator_tag> && ...) &&
        concat-is-bidirectional <Const, Views...> is true, iterator_category denotes std::bidirectional_iterator_tag.
  • Otherwise, if (std::derived_from<Cs, std::forward_iterator_tag> && ...) is true, iterator_category denotes std::forward_iterator_tag.
  • Otherwise, iterator_category denotes std::input_iterator_tag.

Data members

Member	Definition
maybe-const <Const, ranges::concat_view>* parent_	a pointer to the parent concat_view (exposition-only member object*)
base-iter it_	an iterator into the current view (exposition-only member object*)

Member functions

(constructor)	constructs an iterator (public member function)
operator*	accesses the element (public member function)
operator[]	accesses an element by index (public member function)
operator++operator++(int)operator--operator--(int)operator+=operator-=	advances or decrements the underlying iterator (public member function)
Exposition-only function templates
satisfy	replaces it_ with the beginning of the next view, if it_ is the end of current view (exposition-only member function*)
prev	decrements it_ such that it points to the previous position (exposition-only member function*)
advance-fwd	advances the current position on given offset (exposition-only member function*)
advance-bwd	decrements the current position on given value (exposition-only member function*)

Non-member functions

operator==operator<operator>operator<=operator>=operator<=> (C++26)	compares the underlying iterators (function)
operator+operator- (C++26)	performs iterator arithmetic (function)
iter_move (C++26)	casts the result of dereferencing the underlying iterator to its associated rvalue reference type (function)
iter_swap (C++26)	swaps the objects pointed to by two underlying iterators (function)

Example

The preliminary version can be checked out on Compiler Explorer.

Run this code

#include <iostream>
#include <iterator>
#include <ranges>
 
int main()
{
    namespace views = std::views;
    static constexpr int p[]{1, 2, 3};
    static constexpr auto e = {4, 5};
    auto t = views::iota(6, 9);
    auto cat = views::concat(p, e, t);
    auto dog = views::concat(cat, cat);
    for (auto i{dog.begin()}; i != std::default_sentinel; ++i)
        std::cout << *i << ' ';
    std::cout << '\n';
}

Output:

1 2 3 4 5 6 7 8 1 2 3 4 5 6 7 8

References

• C++26 standard (ISO/IEC 14882:2026):

• 26.7.18.3 Class template concat_view::iterator [range.concat.iterator]