NAME¶

std::span::span - std::span::span

Synopsis¶

constexpr span() noexcept; (1)
template< class It >

explicit(extent != std::dynamic_extent) (2)

constexpr span( It first, size_type count );
template< class It, class End >

explicit(extent != std::dynamic_extent) (3)

constexpr span( It first, End last );
template< std::size_t N > (4)
constexpr span( element_type (&arr)[N] ) noexcept;
template< class U, std::size_t N > (5)
constexpr span( std::array<U, N>& arr ) noexcept;
template< class U, std::size_t N > (6)
constexpr span( const std::array<U, N>& arr ) noexcept;
template< class R >

explicit(extent != std::dynamic_extent) (7)

constexpr span( R&& range );
template< class U, std::size_t N >

explicit(extent != std::dynamic_extent && N == std::dynamic_extent) (8)

constexpr span( const std::span<U, N>& source ) noexcept;
constexpr span( const span& other ) noexcept = default; (9)

Constructs a span.

1) Constructs an empty span whose data() == nullptr and size() == 0.

* This overload participates in overload resolution only if extent == 0 || extent
== std::dynamic_extent.

2) Constructs a span that is a view over the range [first, first + count); the
resulting span has data() == std::to_address(first) and size() == count.

* The behavior is undefined if [first, first + count) is not a valid range, if It
does not actually model contiguous_iterator, or if extent != std::dynamic_extent
&& count != extent.
* This overload participates in overload resolution only if

* It satisfies contiguous_iterator
* the conversion from std::iter_reference_t<It> to element_type is at
most a qualification conversion.

3) Constructs a span that is a view over the range [first, last); the resulting span
has data() == std::to_address(first) and size() == last-first.

* The behavior is undefined if [first, last) is not a valid range, if It does not
actually model contiguous_iterator, if End does not actually model
sized_sentinel_for for It, or if extent != std::dynamic_extent && last-first !=
extent.
* This overload participates in overload resolution only if

* It satisfies contiguous_iterator,
* End satisfies sized_sentinel_for for It,
* the conversion from std::iter_reference_t<It> to element_type is at
most a qualification conversion, and
* std::is_convertible_v<End, std::size_t> is false.

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 participate in overload resolution only if extent ==
std::dynamic_extent || N == extent is true and the conversion from
std::remove_pointer_t<decltype(data(arr))> to element_type is at most a
qualification conversion. These constructor templates are never used for class
template argument deduction.

7) Constructs a span that is a view over the range range; the resulting span has
size() == std::ranges::size(range) and data() == std::ranges::data(range).

* The behavior is undefined if R does not actually model contiguous_range and
sized_range or if R does not model borrowed_range while element_type is
non-const or both extent != dynamic_extent and std::ranges::size(range) !=
extent are true.
* This overload participates in overload resolution only if

* R satisfies contiguous_range and sized_range,
* either R satisfies borrowed_range or std::is_const_v<element_type> is
true
* std::remove_cvref_t<R> is not a specialization of std::span,
* std::remove_cvref_t<R> is not a specialization of std::array
* std::is_array_v<std::remove_cvref_t<R>> is false, and
* the conversion from std::ranges::range_reference_t<R> to element_type
is at most a qualification conversion.

8) Converting constructor from another span source; the resulting span has size() ==
source.size() and data() == source.data().

* The behavior is undefined if both extent != dynamic_extent and source.size() !=
extent are true.
* This overload participates in overload resolution only if at least one of extent
== std::dynamic_extent, N == std::dynamic_extent and N == extent is true and the
conversion from U to element_type is at most a qualification conversion.

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

Parameters¶

first - iterator to the first element of the sequence
count - number of elements in the sequence
last - iterator past the last element of the sequence or another sentinel
arr - array to construct a view for
range - range to construct a view for
source - another span to convert from
other - another span to copy from

Exceptions¶

2) Throws nothing.
3) Throws what and when last - first throws.
7) Throws what and when std::ranges::size(r) and std::ranges::data(r) 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
ssize returns the size of a container or array
(C++17) (function template)
(C++20)
data obtains the pointer to the underlying array
(C++17) (function template)