std::span::subspan

 

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)

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

as_bytesas_writable_bytes

Non-member constant

dynamic_extent

Deduction guides

 

template< std::ptrdiff_t Offset,           std::ptrdiff_t Count = std::dynamic_extent > constexpr std::span<element_type, E /* see below */> subspan() const;	(1)
constexpr std::span<element_type, std::dynamic_extent>     subspan( std::ptrdiff_t Offset,              std::ptrdiff_t Count = std::dynamic_extent ) const;	(2)

Obtains a span that is a view over the Count elements of this span starting at offset Offset. If Count is std::dynamic_extent, the number of elements in the subspan is size() - offset (i.e., it ends at the end of *this.).

The behavior is undefined if either Offset or Count is out of range. This happens if

• Offset is either less than zero or greater than size();
• Count is less than zero and not std::dynamic_extent;
• Offset + Count is greater than size().

The extent E of the span returned by (1) is determined as follows:

• If Count is not std::dynamic_extent, Count;
• Otherwise, if Extent is not std::dynamic_extent, Extent - Offset;
• Otherwise, std::dynamic_extent.

Return value

The requested subspan r, such that r.data() == this->data() + Offset. If Count is std::dynamic_extent, r.size() == this->size() - Offset; otherwise r.size() == Count.

See also

first	obtains a subspan consisting of the first N elements of the sequence (public member function)
last	obtains a subspan consisting of the last N elements of the sequence (public member function)