Boost C++ Libraries

Checks if the first geometry is completely inside the second geometry using the specified strategy.

Description

The free function within checks if the first geometry is completely inside the second geometry, using the specified strategy. Reasons to specify a strategy include: use another coordinate system for calculations; construct the strategy beforehand (e.g. with the radius of the Earth); select a strategy when there are more than one available for a calculation.

Synopsis

template<typename Geometry1, typename Geometry2, typename Strategy>
bool within(Geometry1 const & geometry1, Geometry2 const & geometry2, Strategy const & strategy)

Parameters

Returns

true if geometry1 is completely contained within geometry2, else false

Header

Either

#include <boost/geometry.hpp>

Or

#include <boost/geometry/algorithms/within.hpp>

Conformance

The function within implements function Within from the OGC Simple Feature Specification.

	Note
	OGC defines within as completely within and not on the border. See the notes for within / on the border

Supported geometries

	Note
	In this status matrix above: columns are types of first parameter and rows are types of second parameter. So a point can be checked to be within a polygon, but not vice versa.

Notes

If a point is located exactly on the border of a geometry, the result depends on the strategy. The default strategy (Winding (coordinate system agnostic)) returns false in that case.

If a polygon has a reverse oriented (e.g. counterclockwise for a clockwise typed polygon), the result also depends on the strategy. The default strategy returns still true if a point is completely within the reversed polygon. There is a specific strategy which returns false in this case.

Complexity

Linear

See also

Available Strategies

Example

[within_strategy] [within_strategy_output]