256: Mainline

In addition to reducing duplication, there are other reasons for exploiting inheritance, such as the following:

• You may already have defined a fully debugged Attraction class. To prevent the gratuitous introduction of bugs, you would want to use that class definition as it stands, rather than, say, copying bits of the Attraction class definition into the Movie and Symphony class definitions.
• You may have decided to purchase code for the Attraction class from a vendor, because you anticipate using the elaborate capabilities advertised by that vendor. Because the vendor supplies you with compiled code only, you cannot access the source code, so you cannot copy bits of the vendor's Attraction class definition into your Movie and Symphony class definitions. You can only define new classes that inherit from your purchased classes.