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)

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
to (C++23)
Range primitives
range_size_trange_difference_trange_value_trange_reference_t	iterator_tconst_iterator_tsentinel_tconst_sentinel_t (C++23)(C++23)	range_const_reference_trange_rvalue_reference_trange_common_reference_t (C++23)	elements_of (C++23)
Dangling iterator handling
dangling	borrowed_iterator_t	borrowed_subrange_t
Range concepts
range borrowed_range sized_range constant_range (C++23)	common_range view viewable_range	input_range output_range forward_range	bidirectional_range random_access_range contiguous_range
Views
view_interface	subrange
Range factories
empty_viewviews::empty single_viewviews::single	iota_viewviews::iota repeat_viewviews::repeat (C++23)(C++23)	basic_istream_viewviews::istream
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	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 objects
Range adaptor closure objects
range_adaptor_closure (C++23)
Helper items
copyable-box movable-box (until C++23)(C++23)	simple-view non-propagating-cache

 

std::ranges::subrange

Member functions

subrange::subrange (C++20)

subrange::operator PairLike (C++20)

Observers

subrange::begin (C++20)

subrange::end (C++20)

subrange::empty (C++20)

subrange::size (C++20)

Iterator operations

subrange::advance (C++20)

subrange::next (C++20)

subrange::prev (C++20)

Deduction guides

Non-member functions

get (C++20)

Helper types

subrange_kind (C++20)

tuple_size (C++20)

tuple_element (C++20)

 

template< /* see below */ 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 =     !std::is_reference_v<T> && requires(T t) {         typename std::tuple_size<T>::type; // ensures std::tuple_size<T>                                            // is complete         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>&>;     };	(2)	(until C++23) (exposition only*)
	(3)
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) (exposition only*)
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) (exposition only*)

1) Converts subrange to a pair-like type (i.e. a type models the helper concept pair-like defined below (until C++23)pair-like (since C++23)). Equivalent to return PairLike(i_, s_);, where i_ and s_ are the stored iterator and sentinel respectively.

PairLike is constrained that std::same_as<std::remove_cvref_t<PairLike>, subrange> is false.

This conversion function has additional constraints imposed by pair-like-convertible (see below).

2) The exposition-only concept pair-like specifies a type is pair-like. Generally, an expression e of a pair-like type can be used for structured binding (i.e. auto const& [x, y] = e; is generally well-formed). This concept is replaced by the library-wide exposition-only concept pair-like. (since C++23)

3) The exposition-only concept pair-like-convertible-from refines pair-like. It

• rejects reference types and (since C++23)range types,
• requires that U and V are convertible to the first and second element type of T respectively, and
• requires the conversion from U (which will be replaced by const I&) to the first element type to be non-slicing (see convertible-to-non-slicing).

Parameters

(none)

Return value

A PairLike value direct-initialized with the stored iterator and sentinel.

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>

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