Hi Evan, that looks very interesting indeed - as still newby I try to understand: - u create a class "Y" to tackle the "zero" problem for different kinds of y vectors in a common way - u create a "Signal" class for the Y- signal inheriting interfaces from y and Storable.Storable Then u nest X and Y in a V.Vector - array and give it the type synonym SigVec. In all of this X and Y are ur types (or type synonyms) and y is a help variable. Then u define the function at -- and that where my understanding fails ? - this function takes X and sigVec and give u Y ? -- do u use it to applies all functions on SigVec on Y ? - don't u need to create instances somewhere in the process and wouldn't u then have to write all the code during the instance declaration ? Cheers Phil P.S.: - some generic question: - I read using composite datatype using the "data" keyword makes code rather slow - is nesting better ? : e.g. "data Signal Double v.Vector" versus "newtype (Double, v.Vector) - which nesting structure is most efficient - touples, lists, V.vector, ... - alternatively I'm thinking of an "external parallel list" to store information about the signals -- View this message in context: http://haskell.1045720.n5.nabble.com/Data-Type-Inheritance-ala-OO-Inheritenc... Sent from the Haskell - Haskell-Cafe mailing list archive at Nabble.com.