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

 

C++

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Standard library headers

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Feature test macros (C++20)

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Concepts library (C++20)

Metaprogramming library (C++11)

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Containers library

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Ranges library (C++20)

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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_t range_value_t	range_reference_trange_const_reference_trange_rvalue_reference_t   (C++23)	iterator_tconst_iterator_tsentinel_t (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
Factories
empty_viewviews::empty iota_viewviews::iota	single_viewviews::single basic_istream_viewviews::istream	repeat_viewviews::repeat (C++23)(C++23)
Adaptors
ref_view views::all_tviews::all common_viewviews::common owning_view views::counted reverse_viewviews::reverse zip_viewviews::zip (C++23)(C++23) as_const_viewviews::as_const (C++23)(C++23) as_rvalue_viewviews::as_rvalue (C++23)(C++23)	take_viewviews::take take_while_viewviews::take_while drop_viewviews::drop drop_while_viewviews::drop_while zip_transform_viewviews::zip_transform (C++23)(C++23) adjacent_transform_viewviews::adjacent_transform (C++23)(C++23)   cartesian_product_viewviews::cartesian_product (C++23)(C++23)	elements_viewviews::elements keys_viewviews::keys values_viewviews::values transform_viewviews::transform adjacent_viewviews::adjacent (C++23)(C++23) slide_viewviews::slide (C++23)(C++23) stride_viewviews::stride (C++23)(C++23)	filter_viewviews::filter join_viewviews::join split_viewviews::split lazy_split_viewviews::lazy_split join_with_viewviews::join_with (C++23)(C++23) chunk_viewviews::chunk (C++23)(C++23) chunk_by_viewviews::chunk_by (C++23)(C++23)
Range adaptor objects
Range adaptor closure objects
Helper items
copyable-box	simple-view

 

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< /*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*/ =                  // exposition only   !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>>;     typename std::tuple_element_t<1, std::remove_const<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)	(since C++20)
template< class T, class U, class V > concept /*pair-like-convertible-from*/ = // exposition only   !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>>;	(3)	(since C++20)

1) Converts subrange to a pair-like type (i.e. a type models pair-like, see below). Equivalent to return PairLike(i_, s_);, where i_ and s_ are the stored iterator and sentinel respectively. 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). Like standard concepts, this concept is modeled if it is satisfied and all concepts it subsumes are modeled.

3) The exposition-only concept pair-like-convertible-from refines pair-like. It rejects range types and requires that U and V are convertible to the first and second element type of T respectively, and the conversion from U (which will be replaced by const I&) to the first element type is non-slicing (see convertible-to-non-slicing). Like standard concepts, this concept is modeled if it is satisfied and all concepts it subsumes are modeled.

The exposition only concept different-from is modeled by types T and U if and only if std::decay_t<T> and std::decay_t<U> are different types.

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.

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 legacy_strview = std::pair<
    std::string::const_iterator,
    std::string::const_iterator
>;
 
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