Reference Manual: CGAL_Min_circle_2

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Traits Class Adapter for 2D Smallest Enclosing Circle to 2D Homogeneous Points (CGAL_Min_circle_2_adapterH2)

Definition

The class CGAL_Min_circle_2_adapterH2<PT,DA> interfaces the 2D optimisation algorithm for smallest enclosing circles with the point class PT. The data accessor DA [KW97] is used to access the hx-, hy- and hw-coordinate of PT, i.e. PT is supposed to have a homogeneous representation of its coordinates.

#include <CGAL/Min_circle_2_adapterH2.h>

Types

CGAL_Min_circle_2_adapterH2<PT,DA>::DA
Data accessor for homogeneous coordinates.

CGAL_Min_circle_2_adapterH2<PT,DA>::Point
Point type.

CGAL_Min_circle_2_adapterH2<PT,DA>::Circle
Circle type.

Creation

CGAL_Min_circle_2_adapterH2<PT,DA> adapter ( DA da = DA());

CGAL_Min_circle_2_adapterH2<PT,DA> adapter ( CGAL_Min_circle_2_adapterH2<PT,DA>);

Operations

CGAL_Orientation adapter.orientation ( Point p, Point q, Point r)
returns constants CGAL_LEFTTURN, CGAL_COLLINEAR, or CGAL_RIGHTTURN iff r lies properly to the left, on, or properly to the right of the oriented line through p and q, resp.

Example

The following example illustrates the use of the traits class adapters with your own point class. For the sake of simplicity, we expect a point class with homogeneous int coordinates and access functions hx(), hy(), and hw(). Based on this we show how to implement and use data accessors.

Note: In this release correct results are only guaranteed if exact arithmetic is used, so this example (using integer arithmetic with possible overflows) is only intended to illustrate the techniques.

#include <CGAL/Min_circle_2_adapterH2.h>
#include <CGAL/Min_circle_2.h>

// your own point class (homogeneous)
class PtH {
    // ...
  public:
    PtH( int hx, int hy, int hw);
    int  hx( ) const;
    int  hy( ) const;
    int  hw( ) const;
    // ...
};

// the data accessor for PtH
class PtH_DA {
  public:
    typedef  int  RT;
    void  get( const PtH& p, int& hx, int& hy, int& hw) const {
        hx = p.hx(); hy = p.hy(); hw.phw();
    }
    int  get_x( const PtH& p) const { return( p.hx()); }
    int  get_y( const PtH& p) const { return( p.hy()); }
    int  get_w( const PtH& p) const { return( p.hw()); }
    void  set( PtH& p, int hx, int hy, int hw) const { p = PtH( hx, hy, hw); }
};

// some typedefs
typedef  CGAL_Min_circle_2_adapterH2< PtH, PtH_DA >  AdapterH;
typedef  CGAL_Min_circle_2< AdapterH >               Min_circle;

// do something with Min_circle
Min_circle   mc( /*...*/ );

Next: Requirements of Traits Class Adapters to 2D Cartesian Points