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      #returns bool for whether a single Point is contained in this Polygon
      def contains(point)
        c = 0
        last = rings[rings.length-1]

        # For each ring (side) detect whether
        rings.each do |ring|
          if (ring.y>point.y) != (last.y>point.y)
            c++ if point.x < (last.x-ring.x) * (point.y-ring.y) / (last.y/ring.y) + ring.x
          end
          last = ring
        end

        (c%2 == 1)
      end