Peter Padawitz wrote:
Yes, the recursive calls of compCommand are supposed to be calls of compBlock.
The intention of the program is a generic evaluator comp... of Sigma-terms in arbitrary Sigma-algebras. The signature Sigma is given by the first 4 types (and the corresponding functions in the class declaration), the terms are the objects of the types, and the algebras are the class instances.
The problem with my implementation in terms of multiple-parameter classes seems to be - I conclude this from Ryan's comment - that the intended dependency among the parameters is not reflected here. But what are the alternatives? Roughly said, I need a construct that allows me gather several type variables such that an instance is always an instance of all of them.
well, given class Java a b c d where .... if it is true that everything is determined by choice of any one of them, you could write class Java a b c d | a -> b, b -> c, c -> d, d -> a where... otherwise, well you can express whatever dependency network you want... Jules