For an associated data type D, we know that the type function D is injective, i.e., for different indicies given to D we'll get different data types. This makes much more powerful reasoning possible in the type checker. If associated data types are removed there has to be some new mechanism to declare an associated type as injective, or the type system will lose power.
-- Lennart 2008/12/10 Eyal Lotem <[EMAIL PROTECTED]>: > If we have associated type synonyms, is there still reason to have > associated data types? > > For example, we can replace: > > class C b where > data D b > ... > > instance C Int where > data D Int = D | E > > with: > > class C b where > type D b > ... > > data DInt = D | E > instance C Int where > type D Int = DInt > > > Or perhaps allow, for convenience, this form (which would desugar to the > above): > > class C b where > type D b > ... > > instance C Int where > data D Int = D | E > _______________________________________________ > Haskell-Cafe mailing list > [email protected] > http://www.haskell.org/mailman/listinfo/haskell-cafe > > _______________________________________________ Haskell-Cafe mailing list [email protected] http://www.haskell.org/mailman/listinfo/haskell-cafe
