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std::span

Defined in header <span>
template< 
    class T, 
    std::size_t Extent = std::dynamic_extent
> class span;
(since C++20)

The class template span describes an object that can refer to a contiguous sequence of objects with the first element of the sequence at position zero. A span can either have a static extent, in which case the number of elements in the sequence is known and encoded in the type, or a dynamic extent.

A typical implementation holds only two members: a pointer to T and a size.

Template parameters

T - element type; must be a complete type that is not an abstract class type
Extent - the number of elements in the sequence, or std::dynamic_extent if dynamic

Member types

Member type Definition
element_type T
value_type std::remove_cv_t<T>
index_type std::size_t
difference_type std::ptrdiff_t
pointer T*
const_pointer const T*
reference T&
const_reference const T&
iterator implementation-defined LegacyRandomAccessIterator, ConstexprIterator, and LegacyContiguousIterator whose value_type is value_type
const_iterator implementation-defined constant LegacyRandomAccessIterator, ConstexprIterator, and LegacyContiguousIterator whose value_type is value_type
reverse_iterator std::reverse_iterator<iterator>
const_reverse_iterator std::reverse_iterator<const_iterator>

Note: iterator is a mutable iterator if T is not const-qualified.

All requirements on the iterator types of a Container applies to the iterator and const_iterator types of span as well.

Member constant

static constexpr std::size_t extent = Extent;

Member functions

constructs a span
(public member function)
assigns a span
(public member function)
Iterators
returns an iterator to the beginning of the sequence
(public member function)
returns an iterator to the end of the sequence
(public member function)
returns a reverse iterator to the beginning of the sequence
(public member function)
returns a reverse iterator to the end of the sequence
(public member function)
Element access
access the first element
(public member function)
access the last element
(public member function)
accesses an element of the sequence
(public member function)
returns a pointer to the beginning of the sequence of elements
(public member function)
Observers
returns the number of elements in the sequence
(public member function)
returns the size of the sequence in bytes
(public member function)
checks if the sequence is empty
(public member function)
Subviews
obtains a subspan consisting of the first N elements of the sequence
(public member function)
obtains a subspan consisting of the last N elements of the sequence
(public member function)
obtains a subspan
(public member function)

Non-member functions

returns iterators to the beginning and the end of the span
(function)
converts a span into a view of its underlying bytes
(function template)
accesses an element of a static-extent span
(function template)

Non-member constant

(C++20)
a constant of type size_t signifying that the span has dynamic extent
(constant)

Helper classes

obtains the size of a static-extent span
(class template specialization)
obtains the type of the elements of a static-extent span
(class template specialization)

Deduction guides

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