On Wed, 1 Jun 2005, Thomas Davie wrote: > Hi, > I was wondering if I hat missed something and it was possible to > do this within the Haskell type system or not... > > Essentially I would like some sort of inderritance property for > Haskell types, I often find myself wanting to for example extend a > tree with black/white colouring, or later extend the tree with some > sort of ID, etc. > > So I would eno up with three data types > > data MyTree = Branch MyTree MyTree | Leaf > > type BwTag = Bool > data MyBwTree = Branch BwTag MyBwTree MyBwTree | Node BwTag
What about data MyTree a = Branch a (MyTree a) (MyTree a) | Node a and the types MyTree () MyTree Bool MyTree (Bool, Int) ? _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
