[Haskell-cafe] Re: Approaches to dependent types (DT)

pbrowne wrote:

Dependent Types (DT) The purpose of dependent types (DT) is to allow programmers to specify dependencies between the parameters of a multiple parameter class.

'Dependent type' means result type (of a function) can depend on argument values. This is not (directly) supported in Haskell. What you are talking about is called 'functional dependencies', not 'dependent types'. Sometimes abbreviated as 'fundeps'.

DTs can be seen as a move towards more general purpose parametric type classes.

This is at least misleading, as adding a functional dependency does not make the class more general, but more special, as it reduces the number of possible instances. Cheers Ben