std::ranges::range

 

C++

Language

Standard Library Headers

Freestanding and hosted implementations

Named requirements

Language support library

Concepts library (C++20)

Diagnostics library

Utilities library

Strings library

Containers library

Iterators library

Ranges library (C++20)

Algorithms library

Numerics library

Input/output library

Localizations library

Regular expressions library (C++11)

Atomic operations library (C++11)

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Technical Specifications

 

Ranges library

Range access
begincbegin endcend	rbegincrbegin rendcrend	size empty datacdata
Range primitives
iteartor_tsentinel_t	range_difference_trange_value_t	range_reference_trange_rvalue_reference_t
Dangling iterator handling
dangling	safe_iterator_t	safe_subrange_t
Range concepts
range sized_range view	input_range output_range forward_range	bidirectional_range random_access_range contiguous_range	common_range viewable_range
Views
view_interface	subrange
Semiregular wrapper
Factories
empty_viewviews::empty	single_viewviews::single	iota_viewviews::iota	views::counted
Adaptors
all_viewviews::all join_viewviews::join take_viewviews::take basic_istream_viewistream_view	ref_view                                split_viewviews::split take_while_viewviews::take_while elements_viewviews::elements	common_viewviews::common transform_viewviews::transform drop_viewviews::drop keys_viewviews::keys	reverse_viewviews::reverse filter_viewviews::filter drop_while_viewviews::drop_while values_viewviews::values

 

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 = ranges::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.

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.

Semantic requirements

1) 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 forward_iterator, 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) 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, 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.

Expression-equivalent

Expression e is expression-equivalent to expression f, if e and f have the same effects, either are both potentially-throwing or are both not potentially-throwing (i.e. noexcept(e) == noexcept(f)), and either are both constant subexpressions or are both not constant subexpressions.