View Template Library

union_view<Cont_a, Cont_b, Const_tag, Iter_tag, Base_a, Base_b>


Category: adaptors	Component type: type

Description

The union_view template represents objects that reference two containers, and that have methods for accessing their elements. The properties of any union_view instance depend on the properties of the container template parameters. More accurately, a union_view referencing Container provides a Container interface, a union_view referencing Forward Containers provides a Forward Container interface while a Random Access Container provides a Random Access Conatiner interface.[1].

The union_view presents all the elements of both containers concatenated.

The guarantees of the order of elements are the same as those provided by both underlying container, as is the validity of more than one active iterators at any one time.

union_views are mutable if and only if the const_tag template parameter is mutable_view_tag.

A union_view owns its referenced containers, if its corresponding base template parameter is aggregated_ownership, it merely references its containers, if the base template parameter is referenced_ownership.

WARNING: Do not confuse the view type with the view concept!

Template parameters

Parameter	Description	Default
`container_a`	The view's container A type: the type of container referenced by this view
`container_b`	The view's container B type: the type of container referenced by this view
`const_tag`	The view's const tag: either `const_view_tag` or `mutable_view_tag`	`const_view_tag`
`iterator_tag`	The view's directional iterator category	The minium of `container_a::iterator::iterator_cateory` and `container_b::iterator::iterator_category`
`base_a`	The view's ownership type: the base class that determines if the view references or owns the container	`referenced_ownership`
`base_b`	The view's ownership type: the base class that determines if the view references or owns the container	`referenced_ownership`

Definition

Defined in the header union_view.h.

Model of

View

Type requirements

The two containers have to have the same value type. The requirements the union_view satisfies depend on the requirements its template parameters satisfy:

Container satisfies	View satisfies
Container	Container [1]
Forward Containers	Forward Containers [1]

Members

Member	Where defined	Description
`value_type`	Container	The type T of the elements accessed through the container.
`domain_type_a`	view	The type of the referenced container A.
`domain_type_b`	view	The type of the referenced container B.
`pointer`	Container	`container::pointer`.
`reference`	Container	`container::reference`.
`const_reference`	Container	`container::const_reference`.
`size_type`	Container	`conainer::size_type`.
`difference_type`	Container	`container::difference_type`.
`iterator`	Container	Iterator used to iterate through the view.
`const_iterator`	Container	Const iterator used to iterate through the view.
`reverse_iterator`	Reversible Container	Iterator used to iterate backwards through a container.
`const_reverse_iterator`	Reversible Container	Const iterator used to iterate backwards through a container.
`iterator begin()`	Container	Returns an iterator pointing to the begin of the view.
`iterator end()`	Container	Returns an iterator pointing to the end of the view.
`const_iterator begin() const`	Container	Returns a const_iterator pointing to the begin of the view.
`const_iterator end() const`	Container	Returns a const_iterator pointing to the end of the view.
`reverse_iterator rbegin()`	Reversible Container	Valid for bidirectional container's only. Returns a `reverse_iterator` pointing to the beginning of the reversed container.
`reverse_iterator rend()`	Reversible Container	Valid for bidirectional container's only. Returns a `reverse_iterator` pointing to the end of the reversed container.
`const_reverse_iterator rbegin() const`	Reversible Container	Valid for bidirectional container's only. Returns a `const_reverse_iterator` pointing to the beginning of the reversed container.
`const_reverse_iterator rend() const`	Reversible Container	Valid for bidirectional container's only. Returns a `"const_reverse_iterator` pointing to the end of the reversed container.
`reference front()`	Sequence	Returns a `reference` for the first element in the `container`.
`reference back()`	Sequence	Returns a `reference` for the last element in the `container`. Requires a bidirectional container.
`const_reference front() const`	Sequence	Returns a `const_reference` for the first element in the `view`.
`const_reference back() const`	Sequence	Returns a `const_reference` for the last element in the `view`. Requires a bidirectional container.
`reference` operator[](size_type n)	Random access container	Returns a `reference` for the nth element in the `container`.
`const_reference operator[](size_type n)const`	Random access container	Returns a `const_reference` for the nth element in the `container`.
`reference at(size_type n)`	Random access container	Returns a `const_reference` for the nth element in the `container`. Does a range check on n and will throw `std::range_error` if it fails.
`const_reference at(size_type n)const`	Random access container	Returns a `const_reference` for the nth element in the `container`. Does a range check on n and will throw `std::range_error` if it fails.
`size_type size() const`	Container	Returns the size of the view.
`size_type max_size() const`	Container	Returns the largest possible size of the view.
`bool empty() const`	Container	true if the view's size is 0.
`union_view()`	view	Creates an empty view.
`union_view(domain_a_type&, domain_b_type&)`	view	Creates a view of given container.
`void swap(union_view&)`	Container	Swaps the two views. Iterators are invalidated by this operation. For referencing views, the containers themselves are not swapped.
`bool operator==(const union_view&, const union_view&)`	Forward Container	Tests two views for equality. This is a global function, not a member function. Views may be equal even if their referenced containers are not.
`bool operator<(const union_view&, const union_view&)`	Forward Container	Lexicographical comparison. This is a global function, not a member function.

Notes

[1]