docs: public void add( Interval another ) {
          this.lowerBound = ( this.lowerBound == MIN || another.lowerBound == MIN ) ? MIN : this.lowerBound+another.lowerBound;
          this.upperBound = ( this.upperBound == MAX || another.upperBound == MAX ) ? MAX : this.upperBound+another.upperBound;
      }