4 Extending the Existing DrRacket Classes

Each of the names:
is bound to an extender function. In order to change the behavior of DrRacket, you can derive new classes from the standard classes for the frame, texts, canvases. Each extender accepts a function as input. The function it accepts must take a class as it’s argument and return a classes derived from that class as its result. For example:

    (lambda (super%)
      (class super%
        (define/public (method1 x) ...)
extends the interactions text class with a method named method1.