code: public SimpleDistanceConstraint getConstraint(TimePoint tpFrom, TimePoint tpTo) {
  		if (this.distance[tpFrom.getID()][tpTo.getID()] != INF)
  			return tPoints[tpFrom.getID()].getOut(tpTo.getID());
  		return null;
  	}
docs: Get active constraint between two {@link TimePoint}s.
  @param tpFrom The source {@link TimePoint}.
  @param tpTo The destination {@link TimePoint}.
  @return The active {@link SimpleDistanceConstraint} between the
  two {@link TimePoint}s (<code>null</code> if none exists).