std::ranges::subrange<I,S,K>::operator PairLike

 

C++

Compiler support

Freestanding and hosted

Language

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::subrange

Member functions

subrange::subrange

subrange::operator PairLike

Observers

subrange::begin

subrange::end

subrange::empty

subrange::size

Iterator operations

subrange::advance

subrange::next

subrange::prev

Deduction guides

Non-member functions

get(std::ranges::subrange)

Helper types

subrange_kind

tuple_size<std::ranges::subrange>

tuple_element<std::ranges::subrange>

 

template< /*different-from*/<subrange> PairLike >     requires /*pair-like-convertible-from*/<PairLike, const I&, const S&> constexpr operator PairLike() const;	(1)	(since C++20)
Helper concepts
template< class T > concept /*pair-like*/ = /* see description */;	(2)	(exposition only*)
template< class T, class U, class V > concept /*pair-like-convertible-from*/ = /* see description */;	(3)	(exposition only*)

1) Converts subrange to a pair-like type.

For the definition of /*different-from*/, see different-from .

2) Determines whether a type is pair-like .

Equivalent to: template< class T > concept /*pair-like*/ = !std::is_reference_v<T> && requires(T t) { typename std::tuple_size<T>::type; requires std::derived_from<std::tuple_size<T>, std::integral_constant<std::size_t, 2>>; typename std::tuple_element_t<0, std::remove_const_t<T>>; typename std::tuple_element_t<1, std::remove_const_t<T>>; { std::get<0>(t) } -> std::convertible_to< const std::tuple_element_t<0, T>&>; { std::get<1>(t) } -> std::convertible_to< const std::tuple_element_t<1, T>&>; };

(until C++23)

This concept is equivalent to the library-wide exposition-only concept pair-like.

(since C++23)

3) Determines whether a pair-like type can be constructed from two values of possibly different given types.

Equivalent to: template< class T, class U, class V > concept /*pair-like-convertible-from*/ = !ranges::range<T> && /*pair-like*/<T> && std::constructible_from<T, U, V> && /*convertible-to-non-slicing*/<U, std::tuple_element_t<0, T>> && std::convertible_to<V, std::tuple_element_t<1, T>>;	(until C++23)
Equivalent to: template< class T, class U, class V > concept /*pair-like-convertible-from*/ = !ranges::range<T> && !std::is_reference_v<T> && /*pair-like*/<T> && std::constructible_from<T, U, V> && /*convertible-to-non-slicing*/<U, std::tuple_element_t<0, T>> && std::convertible_to<V, std::tuple_element_t<1, T>>;	(since C++23)

Return value

PairLike(begin_ , end_ )

Notes

Following types in the standard library are pair-like:

• std::pair<T, U>
• std::tuple<T, U>
• std::array<T, 2>
• std::ranges::subrange<I, S, K>

std::complex<T>

(since C++26)

A program-defined type derived from one of these types can be a pair-like type, if std::tuple_size and std::tuple_element are correctly specialized for it, and calls to std::get<0> and std::get<1> for its value are well-formed.

(until C++23)

Since subrange specializations are range types, conversion to them are not performed via this conversion function.

std::array specializations cannot be converted from subrange, since they are range types.

Example

Run this code

#include <iostream>
#include <ranges>
#include <string>
#include <utility>
 
using striter = std::string::const_iterator;
 
using legacy_strview = std::pair<striter, striter>;
 
void legacy_print(legacy_strview p)
{
    for (; p.first != p.second; ++p.first)
        std::cout << *p.first << ' ';
    std::cout << '\n';
}
 
int main()
{
    std::string dat{"ABCDE"};
    for (auto v{std::ranges::subrange{dat}}; v; v = {v.begin(), v.end() - 1})
    {
        /*...*/
        legacy_print(legacy_strview{v});
    }
}

Output:

A B C D E 
A B C D 
A B C 
A B 
A

See also

tuple-likepair-like (C++23)

specifies that a type implemented the tuple protocol (std::get, std::tuple_element, std::tuple_size) (exposition-only concept*)