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#### unique

Calculates the minimal set of a geometry.

###### Description

The free function unique calculates the minimal set (where duplicate consecutive points are removed) of a geometry.

###### Synopsis

    template<typename Geometry>
    void unique(Geometry & geometry)

###### Parameters

Type | Concept | Name | Description
--- | --- | --- | ---
Geometry & | Any type fulfilling a Geometry Concept | geometry | A model of the specified concept which will be made unique

###### Header

Either

`#include <boost/geometry/geometry.hpp>`

Or

`#include <boost/geometry/algorithms/unique.hpp>`

###### Conformance

The function unique is not defined by OGC.

The function unique conforms to the std::unique function of the C++ std-library.

###### Behavior

Case | Behavior
--- | ---
Point | Nothing happens, geometry is unchanged
Segment | Nothing happens, geometry is unchanged
Rectangle | Nothing happens, geometry is unchanged
Linestring | Removes all consecutive duplicate points
Ring | Removes all consecutive duplicate points
Polygon | Removes all consecutive duplicate points in all rings
Multi Point | Nothing happens, geometry is unchanged. Even if two equal points happen to be stored consecutively, they are kept
Multi Linestring | Removes all consecutive duplicate points in all contained linestrings
Multi Polygon | Removes all consecutive duplicate points in all contained polygons (all rings)

###### Complexity

Linear

###### Example

Shows how to make a so-called minimal set of a polygon by removing duplicate points

    #include <iostream>

    #include <boost/geometry.hpp>
    #include <boost/geometry/geometries/polygon.hpp>
    #include <boost/geometry/geometries/adapted/boost_tuple.hpp>

    BOOST_GEOMETRY_REGISTER_BOOST_TUPLE_CS(cs::cartesian)

    int main()
    {
        boost::geometry::model::polygon<boost::tuple<double, double> > poly;
        boost::geometry::read_wkt("POLYGON((0 0,0 0,0 5,5 5,5 5,5 5,5 0,5 0,0 0,0 0,0 0,0 0))", poly);
        boost::geometry::unique(poly);
        std::cout << boost::geometry::wkt(poly) << std::endl;

        return 0;
    }

Output:

    POLYGON((0 0,0 5,5 5,5 0,0 0))