Friends

I’m giving a series of five lectures at the Laser Summer School (2-8 Sept), on “Adventures with types in Haskell”.  My plan is:

1. Type classes

2. Type families [examples including Repa type tags]

3. GADTs

4. Kind polymorphism

5. System FC and deferred type errors

This message is to invite you to send me your favourite example of using a GADT to get the job done.  Ideally I’d like to use examples that are (a) realistic, drawn from practice (b) compelling and (c) easy to present without a lot of background.  Most academic papers only have rather limited examples, usually eval :: Term t -> t, but I know that GADTs are widely used in practice.

Any ideas from your experience, satisfying (a-c)?  If so, and you can spare the time, do send me a short write-up. Copy the list, so that we can all benefit.

Many thanks

Simon