def edges
	    points = self.vertices
	    points.each_cons(2).map {|p1,p2| Edge.new(p1,p2) } + [Edge.new(points.last, points.first)]
	end
def edges
	    points = self.vertices
	    points.each_cons(2).map {|p1,p2| Edge.new(p1,p2) } + [Edge.new(points.last, points.first)]
	end
!@attribute [r] edges