[Haskell] Modelling languages for FP (like UML for OO)

[Johannes Waldmann]

Mads Lindstrøm wrote:

> In object-oriented programming, UML is used to model programs. In
> functional programming (especially Haskell) we use ???

Nice question.

The problem with UML class diagrams is that they are
only really suited to "classical" OO (composition and inheritance)
and thus are missing some important features:

a) the UML notation for generics (type parameters) is somewhat ad-hoc,
   e. g. there is no good visible disctinction between a template
   and its instantiation.

b) UML supports interfaces, but (speaking Haskell) they are all unary
   predicates (a type implements an interface) and there is
   no notation for multi parameter type classes (would need a hypergraph
   instead of a graph :-)
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