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##### 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>`

Or

`#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