std::span::subspan

C++

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Named requirements

Language support library

Concepts library (C++20)

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Regular expressions library (C++11)

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Technical Specifications

Containers library

array (C++11)

vector

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list

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stack

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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

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)