767: Mainline

Once you have a way to make lists of railroad cars, you could make lists of other objects—such as cylinders or integers—by editing the link and header class definitions by hand, replacing the railroad_car string of characters by another string of characters appropriate to the new type.

Of course, there are good reasons why creating list class definitions by manual editing of the existing header and link class definitions is a bad idea:

• Manual editing is error prone.
• Future improvements to the original class definitions would not propagate to the copied-and-edited class definitions without further, even more error-prone editing.
• You would have to have different names for header and link, corresponding to each type of object that you want to put into lists.