Chapter 2

Instructor's Guide

1. The letter/envelope idiom is a means to separate interface aspects of a class from implementation aspects. An advantage is that implementations may be dynamically changed.
2. Polymorphism may be characterized as the ability to be of a different type, dependent upon circumstances. For object-oriented languages, the best-known form is (inclusion) polymorphism by inheritance. However, (ad hoc) polymorphism, due to function overloading, is a facility found in many languages.
3. See section canonical.
4. See section hush-idioms.
5. We can distinguish between creational, structural and behavioral patterns. For a discussion of their relevance see section Patterns.
6. See section Behavioral.
7. The Reactor pattern describes how to deal with events, in particular when multiple event loops are involved. See section Reactor.
8. See section events.