std::ranges::Range

 

C++

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Language support library

Concepts library (C++20)

Diagnostics library

Utilities library

Strings library

Containers library

Iterators library

Ranges library (C++20)

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Technical Specifications

 

Ranges library

Range access
begincbegin endcend	rbegincrbegin rendcrend	size empty datacdata
Range primitives
iterator_t	sentinel_t
Dangling iterator handling
dangling	safe_iterator_t	safe_subrange_t
Range concepts
Range SizedRange View	InputRange OutputRange ForwardRange	BidirectionalRange RandomAccessRange ContiguousRange	CommonRange ViewableRange
Views
view_interface	subrange
Semiregular wrapper
Factories
empty_viewview::empty	single_viewview::single	iota_viewview::iota	view::counted
Adaptors
all_viewview::all ref_view filter_viewview::filter	transform_viewview::transform                                take_viewview::take	join_viewview::join split_viewview::split	common_viewview::common reverse_viewview::reverse

 

Defined in header <ranges>
template< class T > concept Range = __RangeImpl<T&>; // exposition-only definition	(1)
// exposition-only helper concept template< class T > concept __RangeImpl = requires(T&& t) {   ranges::begin(std::forward<T>(t)); // equality-preserving for forward iterators   ranges::end  (std::forward<T>(t)); };	(2)
// exposition-only helper concept template< class T > concept __ForwardingRange = Range<T> && __RangeImpl<T>;	(3)

1) The Range concept defines the requirements of a type that allows iteration over its elements by providing an iterator and sentinel that denote the elements of the range.

Formally, given an expression E such that decltype((E)) is T, T models Range only if

• [ranges::begin(E), ranges::end(E)) denotes a range, and
• both ranges::begin(E) and ranges::end(E) are amortized constant time and non-modifying, and
• if the type of ranges::begin(E) models ForwardIterator, ranges::begin(E) is equality-preserving (in other words, forward iterators support multi-pass algorithms)

Note: In the exposition-only definition above, the required expressions ranges::begin(std::forward<T>(t)) and ranges::end(std::forward<T>(t)) do not require implicit expression variations.

3) The exposition-only concept __ForwardingRange defines the requirements of a range such that a function can take it by value and return iterators obtained from it without danger of dangling.

Formally, given an expression E such that decltype((E)) is T and an lvalue t that denotes the same object as E, T models __ForwardingRange only if

• ranges::begin(E) and ranges::begin(t) are expression-equivalent (have the same effect when evaluated, and both or neither are potentially-throwing, both or neither are constant subexpressions), and
• ranges::end(E) and ranges::end(t) are expression-equivalent, and
• the validity of iterators obtained from the object denoted by E is not tied to the lifetime of that object.