query(rtree<...> const &, Predicates const &, OutIter)

Finds values meeting passed predicates e.g. nearest to some Point and/or intersecting some Box.

Description

This query function performs spatial and k-nearest neighbor searches. It allows to pass a set of predicates. Values will be returned only if all predicates are met.

Spatial predicates

Spatial predicates may be generated by one of the functions listed below:

It is possible to negate spatial predicates:

! boost::geometry::index::contains(),
! boost::geometry::index::covered_by(),
! boost::geometry::index::covers(),
! boost::geometry::index::disjoint(),
! boost::geometry::index::intersects(),
! boost::geometry::index::overlaps(),
! boost::geometry::index::within()

Satisfies predicate

This is a special kind of predicate which allows to pass a user-defined function or function object which checks if Value should be returned by the query. It's generated by:

boost::geometry::index::satisfies().

Nearest predicate

If the nearest predicate is passed a k-nearest neighbor search will be performed. This query will result in returning k values to the output iterator. Only one nearest predicate may be passed to the query. It may be generated by:

boost::geometry::index::nearest().

Connecting predicates

Predicates may be passed together connected with operator&&().

Synopsis

template<typename Value,
         typename Parameters,
         typename IndexableGetter,
         typename EqualTo,
         typename Allocator,
         typename Predicates,
         typename OutIter>
rtree< Value, Parameters, IndexableGetter, EqualTo, Allocator >::size_type query(rtree< Value, Parameters, IndexableGetter, EqualTo, Allocator > const & tree,
                                                                                 Predicates const & predicates,
                                                                                 OutIter out_it)

Parameter(s)

Type	Name	Description
`rtree< Value, Parameters, IndexableGetter, EqualTo, Allocator > const &`	`tree`	The rtree.
`Predicates const &`	`predicates`	Predicates.
`OutIter`	`out_it`	The output iterator, e.g. generated by std::back_inserter().

Returns

The number of values found.

Example

// return elements intersecting box
bgi::query(tree, bgi::intersects(box), std::back_inserter(result));
// return elements intersecting poly but not within box
bgi::query(tree, bgi::intersects(poly) && !bgi::within(box), std::back_inserter(result));
// return elements overlapping box and meeting my_fun value predicate
bgi::query(tree, bgi::overlaps(box) && bgi::satisfies(my_fun), std::back_inserter(result));
// return 5 elements nearest to pt and elements are intersecting box
bgi::query(tree, bgi::nearest(pt, 5) && bgi::intersects(box), std::back_inserter(result));

// For each found value do_something (it is a type of function object)
tree.query(bgi::intersects(box),
           boost::make_function_output_iterator(do_something()));

Throws

If Value copy constructor or copy assignment throws.

	Warning
	Only one `nearest()` predicate may be passed to the query. Passing more of them results in compile-time error.