[Haskell-cafe] type families with non-type indices

[oleg at okmij.org]

Doug McIlroy wrote:
> An example of such a family is integers mod p. One wants to define the
> operations once for all p, so that a type for any particular p can be
> introduced by a one-line declaration.

That was precisely the motivating example for the 2004 Haskell
Workshop paper
   Implicit configurations -- or, type classes reflect the values of types
   ftp://ftp.deas.harvard.edu/techreports/tr-15-04.pdf
(The Technical Report is the extended version of the paper) 

which discusses several solutions to the problem.