View Template Library

filter_view<Container, Pred, Const_tag, Iter_tag, Base>


Category: adaptors	Component type: type

Description

The filter_view template represents objects that reference one container, and that have methods for accessing its elements. The properties of any filter_view instance depend on the properties of the container template parameter. More accurately, a filter_view referencing a Container provides a Container interface, a filter_view referencing Forward Containers provides a Forward Container interface.

The filter_view presents only those elements for which its predicate is true.

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

filter_views are mutable if and only if the const_tag template parameter is mutable_view_tag. Note that changing elements of the container may result in invalidated iterators and may change the size of the view. Thus, use mutable views only if you really know what you are doing.

A filter_view owns its referenced container, if its base template parameter is aggregated_ownership, it merely references its container, if the base template parameter is referenced_ownership.

Template parameters

Parameter	Description	Default
`container`	The view's container type: the type of container referenced by this view
`predicate`	The view's predicate type: the type of the predicate used to filter the container's elements
`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	`Container::iterator::category` or `bidirectional_iterator_tag` whichever is the lesser.
`base`	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 filter_view.hpp.

Model of

Single Container View

Type requirements

T has to be assignable. predicate has to be a predicate with argument type container::value_type. predicate's operator() has to be a const member. The requirements the filter_view satisfies depend on the requirements its template parameters satisfy:

Container satisfies

View satisfies

Container

Container [1]

Forward Container

Forward Container [1]

Members

Member	Where defined	Description
`value_type`	Container	The type T of the elements accessed through the container.
`domain_type`	Single View	The type of the referenced container.
`predicate_t`	view	The type of the filtering predicate.
`pointer`	Container	Pointer to T.
`reference`	Container	Reference to T.
`const_reference`	Container	Const reference to T.
`size_type`	Container	An unsigned integral type.
`difference_type`	Container	A signed integral 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 reversible container's only. Returns a `reverse_iterator` pointing to the beginning of the reversed container.
`reverse_iterator rend()`	Reversible Container	Valid for reversible container's only. Returns a `reverse_iterator` pointing to the end of the reversed container.
`const_reverse_iterator rbegin() const`	Reversible Container	Valid for reversible 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 reversible container's only. Returns a `const_reverse_iterator` pointing to the end of the reversed container.
`size_type size() const`	Container	Returns the size of the view. [1]
`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.
`filter_view()`	view	The behaviour of default constructed views is undefined, except for subsequent assignment. This is only provided to satisfy the Default Constructible requirement.
`filter_view(container_t&, const predicate_t&)`	view	Creates a view of given container.
`void swap(filter_view&)`	Container	Swaps the two views. Iterators are invalidated by this operation. For referencing views, the containers themselves are not swapped.
`bool operator==(const filter_view&, const filter_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 filter_view&, const filter_view&)`	Forward Container	Lexicographical comparison. This is a global function, not a member function.

Notes

[1] A filter_view satisfies all the requirements of container, except for size() and iterator increment/decrement not guaranteeing constant complexity.

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