INTERFACE PotenEnergy;
IMPORT Energy;
TYPE
  T <: Public;
  Public = Energy.T OBJECT METHODS
      init(): T;
    END;
  (*
    The "Poten" energy measures the overall spread of the vertices.
    It is the sum over every existing vertex "v" of the distance 
    squared between "v" and the origin. *)
  
END PotenEnergy.