code: @Pure
  	protected double computeCostFor(ST segment) {
  		if (this.costComputer != null) {
  			return this.costComputer.computeCostFor(segment);
  		}
  		return segment.getLength();
  	}
docs: Compute and replies the cost to traverse the given graph segment.
  
  @param segment the segment.
  @return the cost to traverse the segment.