[Haskell-beginners] creating a relational tuple type

[Stephen Tetley]

The type classes in Haskell DB are to allow manipulations on type level lists.

You probably want to read the paper "Strongly typed heterogeneous
collections" by Oleg Kiselyov, Ralf Lämmel, and Keean Schupke to get a
sense of Haskell DB:

http://homepages.cwi.nl/~ralf/HList/

To learn Haskell, writing a "less typed" relational algebra engine
would be significantly easier. The early sections of the HList give
simpler heterogeneous lists that don't use type level programming (but
aren't as well typed).