Dune::Std::span< Element, Extent > Class Template Reference

A contiguous sequence of elements with static or dynamic extent. More...

#include <dune/common/std/span.hh>

Span constructors
template<std::size_t e = extent, std::enable_if_t<(e==dynamic_extent||e==0), int > = 0>
constexpr	span () noexcept
	Default construct an empty span.
template<class Iter , class U = std::remove_reference_t<decltype(*std::declval<Iter>())>, std::enable_if_t< std::is_convertible_v< U(*)[], element_type(*)[]>, int > = 0>
constexpr	span (Iter first, size_type size)
	Constructs a span that is a view over the range [first, first+size)
template<class Iter , class U = std::remove_reference_t<decltype(*std::declval<Iter>())>, std::enable_if_t< std::is_convertible_v< U(*)[], element_type(*)[]>, int > = 0>
constexpr	span (Iter first, Iter last)
	Constructs a span that is a view over the range [first, last)
template<class Range , decltype(std::begin(std::declval< Range >()), std::end(std::declval< Range >()), bool{}) = true, std::enable_if_t< not std::is_array_v< Range >, int > = 0>
constexpr	span (Range &range)
	Constructs a span that is a view over the range [range.begin(), range.end())
template<std::size_t N, std::size_t e = extent, std::enable_if_t<(e==Std::dynamic_extent||e==N), int > = 0>
constexpr	span (Impl::TypeIdentity_t< element_type >(&data)[N]) noexcept
	Constructs a span that is a view over the C-array.
template<class T , size_t N, std::size_t e = extent, std::enable_if_t<(e==Std::dynamic_extent||e==N), int > = 0, std::enable_if_t< std::is_convertible_v< T(*)[], element_type(*)[]>, int > = 0>
constexpr	span (std::array< T, N > &arr) noexcept
	Constructs a span that is a view over the array.
template<class T , size_t N, std::size_t e = extent, std::enable_if_t<(e==Std::dynamic_extent||e==N), int > = 0, std::enable_if_t< std::is_convertible_v< const T(*)[], element_type(*)[]>, int > = 0>
constexpr	span (const std::array< T, N > &arr) noexcept
	Constructs a span that is a view over the const array.
template<class E = element_type, std::enable_if_t< std::is_const_v< E >, int > = 0>
constexpr	span (std::initializer_list< value_type > il)
	Constructs a span that is a view over the initializer-list.
constexpr	span (const span &other) noexcept=default
	Copy constructor.
template<class OtherElementType , std::size_t OtherExtent, std::enable_if_t<(extent==Std::dynamic_extent||OtherExtent==Std::dynamic_extent||extent==OtherExtent), int > = 0, std::enable_if_t< std::is_convertible_v< OtherElementType(*)[], element_type(*)[]>, int > = 0>
constexpr	span (const span< OtherElementType, OtherExtent > &s) noexcept
	Converting copy constructor.
constexpr span &	operator= (const span &other) noexcept=default
	Copy assignment operator.

Iterators
constexpr iterator	begin () const noexcept
	Returns an iterator to the beginning.
constexpr iterator	end () const noexcept
	Returns an iterator to the end.
constexpr const_iterator	cbegin () const noexcept
	Returns an iterator to the beginning.
constexpr const_iterator	cend () const noexcept
	Returns an iterator to the end.
constexpr reverse_iterator	rbegin () const noexcept
	Returns a reverse iterator starting at the end.
constexpr reverse_iterator	rend () const noexcept
	Returns a reverse iterator ending at the beginning.
constexpr const_reverse_iterator	crbegin () const noexcept
	Returns a reverse iterator starting at the end.
constexpr const_reverse_iterator	crend () const noexcept
	Returns a reverse iterator ending at the beginning.

Element and data access
constexpr reference	front () const
	Access the first element.
constexpr reference	back () const
	Access the last element.
constexpr reference	at (size_type i) const
	Access specified element with bounds checking.
constexpr reference	operator[] (size_type i) const
	Access specified element.
constexpr pointer	data () const noexcept
	Direct access to the underlying contiguous storage.

Subspans
template<std::size_t Count>
constexpr span< element_type, Count >	first () const
	Obtains a subspan consisting of the first Count elements of the sequence.
template<std::size_t Count>
constexpr span< element_type, Count >	last () const
	Obtains a subspan consisting of the last Count elements of the sequence.
template<std::size_t Offset, std::size_t Count = Std::dynamic_extent>
constexpr span< element_type, subspan_extent(Offset, Count)>	subspan () const
	Obtains a subspan consisting of Count elements of the sequence starting at Offset. More...
constexpr span< element_type, Std::dynamic_extent >	first (size_type count) const
	Obtains a subspan consisting of the first count elements of the sequence.
constexpr span< element_type, Std::dynamic_extent >	last (size_type count) const
	Obtains a subspan consisting of the last count elements of the sequence.
constexpr span< element_type, Std::dynamic_extent >	subspan (size_type offset, size_type count=Std::dynamic_extent) const
	Obtains a subspan consisting of count elements of the sequence starting at offset. More...

Size information
constexpr size_type	size_bytes () const noexcept
	Returns the size of the sequence in bytes.
constexpr bool	empty () const noexcept
	Checks if the sequence is empty.

Detailed Description

template<class Element, std::size_t Extent = Std::dynamic_extent>
class Dune::Std::span< Element, Extent >

A contiguous sequence of elements with static or dynamic extent.

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 at compile-time and encoded in the type, or a dynamic extent.

If a span has dynamic extent, a typical implementation holds two members: a pointer to Element and a size. A span with static extent may have only one member: a pointer to Element.

The implementation is based on the C++ standard working draft N4971 and the documentation provided in cppreference.

Example:

std::vector v{1, 2, 3, 4, 5, 6, 7, 8, 9, 10};
 
// view data as contiguous memory representing 10 elements
auto s1 = Dune::Std::span(v.data(), 10);
 
// view data as contiguous memory with static size
auto s2 = Dune::Std::span<int,10>(v.data());
 
// write data using 2D view
for (std::size_t i = 0; i != s1.size(); i++)
  s1[i] = 2*i;

Template Parameters

Element	The element type; a complete object type that is not an abstract class type.
Extent	Specifies number of elements in the sequence, or Std::dynamic_extent if dynamic.

Member Function Documentation

subspan() [1/2]

template<class Element , std::size_t Extent = Std::dynamic_extent>

template<std::size_t Offset, std::size_t Count = Std::dynamic_extent>

constexpr span< element_type, subspan_extent(Offset, Count)> Dune::Std::span< Element, Extent >::subspan ( ) const

inlineconstexpr

Obtains a subspan consisting of Count elements of the sequence starting at Offset.

Note

If Count == Std::dynamic_extent, the subspan starting at Offset goes until the end of the current span.

References Dune::Std::span< Element, Extent >::data(), and Dune::Std::dynamic_extent.

subspan() [2/2]

template<class Element , std::size_t Extent = Std::dynamic_extent>

constexpr span< element_type, Std::dynamic_extent > Dune::Std::span< Element, Extent >::subspan ( size_type  offset, size_type  count = Std::dynamic_extent  ) const

inlineconstexpr

Obtains a subspan consisting of count elements of the sequence starting at offset.

Note

If count == Std::dynamic_extent, the subspan starting at offset goes until the end of the current span.

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The documentation for this class was generated from the following file:

• dune/common/std/span.hh