code: @Pure
  	public double distance(double x, double y) {
  		double dist = Double.POSITIVE_INFINITY;
  		if (isValidPrimitive()) {
  			for (final BusStop stop : this.busStops) {
  				final double d = stop.distance(x, y);
  				if (!Double.isNaN(d) && d < dist) {
  					dist = d;
  				}
  			}
  		}
  		return Double.isInfinite(dist) ? Double.NaN : dist;
  	}
docs: Replies the distance between the given point and this bus hub.
  
  <p>The distance to the hub is the distance to the nearest bus stop
  located in the hub.
  
  @param x x coordinate.
  @param y y coordinate.
  @return the distance to this bus hub