View Template Library

flagged_filter_view<container, flags, const_tag, iter_tag, base_a,base_b>


Category: adaptors	Component type: type

Description

The flagged_filter_view template represents objects that reference one data container, and that have methods for accessing its elements. The properties of any flagged_filter_view instance depend on the properties of the container and flags template parameters.

The flagged_filter_view presents only those elements for which the corresponding flag in the flags container is true.

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

flagged_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. Thus, use mutable views only if you really know what you are doing.

A flagged_filter_view owns its referenced container/flags, if its base_a/base_b template parameter is aggregated_ownership, it merely references its container/flags, if the base_a/base_b template parameter is referenced_ownership.

Template parameters

Parameter	Description	Default
`container`	The view's container type: the type of container referenced by this view
`flags`	A parallel container used to filter the first 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` or `flags::iterator::category`, whichever is the lessest.
`base_a`	The view's ownership type: the tag class that determines if the view references or owns the container	`referenced_ownership`
`base_b`	The view's flag ownership type: the tag class that determines if the view references or owns the flags.	`referenced_ownership`

Definition

Defined in the header flagged_filter_view.hpp.

Model of

Single Container View

This is debateable since actually two containers are used. Since only one of them is publically visible and use of a flag container instead of a predicate compared to filter_view is just an implementation detail (efficiency: you could use a predicate that looks up the values in a flag container), we feel that this must be a single container view.

Type requirements

T has to be assignable. flags has to be a container with a value type convertible to bool.

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.
`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.
`flagged_filter_view()`	Default Constructible	The behaviour of default constructed views is undefined, except for subsequent assignment. This is only provided to satisfy the Default Constructible requirement.
`flagged_filter_view(container_t&,flags const&)`	view	Creates a view of given container. The size of the flags container must be equal or greater than the size of the data container.
`void swap(flagged_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 flagged_filter_view&, const flagged_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 flagged_filter_view&, const flagged_filter_view&)`	Forward Container	Lexicographical comparison. This is a global function, not a member function.

Notes

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