seeking ideas for short lecture on type classes

[Norman Ramsey]

 > > In a fit of madness, I have agreed to deliver a 50-minute lecture
 > > on type classes to an audience of undergraduate students.  These
 > > students will have seen some simple typing rules for F2 and will
 > > have some exposure to Hindley-Milner type inference in the context
 > > of ML.
 > 
 > Will they have had exposure to more "traditional" OO programming?  If
 > so, it might be useful to note the difference between Haskell type
 > classes and C++/Java/whatever classes, namely that Haskell decouples
 > types and the interfaces that they support.  The advantage is that you
 > can extend a type with a new interface at any point, not just when you
 > define the type.

Hmm --- you are talking about the `instance' declarations, right?

A fact that I know but don't understand the implication of is that
Haskell dispatches on the static type of a value, whereas OO languages
dispatch on the dynamic type of a value.  But I suspect I'll leave
that out :-)


N