std::span::span

C++

Language

Headers

Freestanding and hosted implementations

Named requirements

Language support library

Concepts library (C++20)

Diagnostics library

Utilities library

Strings library

Containers library

Algorithms library

Iterators library

Numerics library

Input/output library

Localizations library

Regular expressions library (C++11)

Atomic operations library (C++11)

Thread support library (C++11)

Filesystem library (C++17)

Technical Specifications

Containers library

array (C++11)

vector

deque

forward_list (C++11)

list

set

multiset

map

multimap

unordered_set (C++11)

unordered_multiset (C++11)

unordered_map (C++11)

unordered_multimap (C++11)

stack

queue

priority_queue

span (C++20)

std::span

Member functions

span::span

span::operator=

Element access

span::operator[]span::operator()

span::data

Iterators

span::beginspan::cbegin

span::endspan::cend

span::rbeginspan::crbegin

span::rendspan::crend

Observers

span::empty

span::size

span::size_bytes

Subviews

span::first

span::last

span::subspan

Non-member functions

operator==operator!=operator<operator<=operator>operator>=

as_bytesas_writable_bytes

Non-member constant

dynamic_extent

Deduction guides

constexpr span() noexcept;	(1)
constexpr span(pointer ptr, index_type count);	(2)
constexpr span(pointer firstElem, pointer lastElem);	(3)
template <std::size_t N> constexpr span(element_type (&arr)[N]) noexcept;	(4)
template <std::size_t N> constexpr span(std::array<value_type, N>& arr) noexcept;	(5)
template <std::size_t N> constexpr span(const std::array<value_type, N>& arr) noexcept;	(6)
template <class Container> constexpr span(Container& cont);	(7)
template <class Container> constexpr span(const Container& cont);	(8)
template <class U, ptrdiff_t N> constexpr span(const std::span<U, N>& s) noexcept;	(9)
constexpr span(const span& other) noexcept = default;	(10)

Constructs a span.

1) Constructs an empty span whose data() == nullptr and size() == 0. This overload only participates in overload resolution if extent == 0 || extent == std::dynamic_extent.

2) Constructs a span that is a view over the range [ptr, ptr + count); the resulting span has data() == ptr and size() == count. The behavior is undefined if [ptr, ptr + count) is not a valid range or if extent != std::dynamic_extent && count != extent.

3) Constructs a span that is a view over the range [firstElem, lastElem); equivalent to span(firstElem, lastElem - firstElem).

4-6) Constructs a span that is a view over the array arr; the resulting span has size() == N and data() == std::data(arr). These overloads only participate in overload resolution if extent == std::dynamic_extent || N == extent is true and std::remove_pointer_t<decltype(std::data(arr))>(*)[] is convertible to element_type (*)[]

7-8) Constructs a span that is a view over the range [std::data(cont), std::data(cont) + std::size(cont)); the resulting span has size() == std::size(cont) and data() == std::data(cont). The behavior is undefined if that is not a valid range or if extent != std::dynamic_extent && std::size(cont) != extent. These functions do not participate in overload resolution unless

• Container is not a specialization of std::span, a specialization of std::array, or an array type;
• std::data(cont) and std::size(cont) are both well-formed; and
• std::remove_pointer_t<decltype(std::data(cont))>(*)[] is convertible to element_type (*)[].

9) Converting constructor from another span s; the resulting span has size() == s.size() and data() == s.data(). This overload only participates in overload resolution if extent == std::dynamic_extent || N == extent is true and U (*)[] is convertible to element_type (*)[].

10) Defaulted copy constructor copies the size and data pointer; the resulting span has size() == other.size() and data() == other.data().

Parameters

ptr, firstElem	-	pointer to the first element of the sequence
count	-	number of elements in the sequence
lastElem	-	pointer past the last element of the sequence
arr	-	array to construct a view for
cont	-	container to construct a view for
s	-	another span to convert from
other	-	another span to copy from

Exceptions

2-3) Throws nothing.

7-8) Throws what and when std::size(cont) and std::data(cont) throw.

See also

data	returns a pointer to the beginning of the sequence of elements (public member function)
size	returns the number of elements in the sequence (public member function)
operator=	assigns a span (public member function)
size (C++17)	returns the size of a container or array (function)
data (C++17)	obtains the pointer to the underlying array (function)