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

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##### 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:

- `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()`,

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()` perdicate may be passed to the query. Passing more of them results in compile-time error.