touches (two geometries)

Checks if two geometries have at least one touching point (tangent - non overlapping)

Synopsis

template<typename Geometry1, typename Geometry2>
bool touches(Geometry1 const & geometry1, Geometry2 const & geometry2)

Parameters

Type	Concept	Name	Description
Geometry1 const &	Any type fulfilling a Geometry Concept	geometry1	A model of the specified concept
Geometry2 const &	Any type fulfilling a Geometry Concept	geometry2	A model of the specified concept

Returns

Returns true if two geometries touch each other

Header

Either

#include <boost/geometry.hpp>

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

Conformance

The function touches implements function Touches from the OGC Simple Feature Specification.

The version with one parameter is additional and not described in the OGC standard

	Note
	Implemented for Point/Linestring/MultiLinestring/Polygon/MultiPolygon.

Examples

Checks if two geometries have at least one touching point (tangent - non overlapping)

#include <iostream>

#include <boost/geometry.hpp>
#include <boost/geometry/geometries/point_xy.hpp>
#include <boost/geometry/geometries/polygon.hpp>

namespace bg = boost::geometry; 

int main()
{
    // Checks if the two geometries touch
    bg::model::polygon<bg::model::d2::point_xy<double> > poly1;
    bg::read_wkt("POLYGON((0 0,0 4,4 4,4 0,0 0))", poly1);
    bg::model::polygon<bg::model::d2::point_xy<double> > poly2;
    bg::read_wkt("POLYGON((0 0,0 -4,-4 -4,-4 0,0 0))", poly2);
    bool check_touches = bg::touches(poly1, poly2);
    if (check_touches) {
         std::cout << "Touches: Yes" << std::endl;
    } else {
        std::cout << "Touches: No" << std::endl;
    }

    bg::model::polygon<bg::model::d2::point_xy<double> > poly3;
    bg::read_wkt("POLYGON((1 1,0 -4,-4 -4,-4 0,1 1))", poly3);
    check_touches = bg::touches(poly1, poly3);
    if (check_touches) {
         std::cout << "Touches: Yes" << std::endl;
    } else {
        std::cout << "Touches: No" << std::endl;
    }

    return 0;
}

Convenient namespace alias

Output:

Touches: Yes



Touches: No