Hi John,

In the class I wrote, c has kind * (e.g. [a]), but then I don't see how to write a suitable map function. For that, I would want c to have kind * -> *. Unfortunately then I don't know to write the others.

Would I have to do something with c having kind (* -> *) ?

class Chunkable2 c el where cLength :: c el -> Int cHead :: c el -> Maybe el cMap :: (el -> el') -> c el -> c el'

When c is (* -> *), why do you need el to be a parameter of the typeclass at all? I.e., would this work for your purposes:

class Chunkable3 c where

cLength :: c el -> Int

cHead :: c el -> Maybe el

cMap :: (a -> b) -> c a -> c b

instance Chunkable3 [] where

cLength = length

cMap = map cHead = ...

Using Functor as a superclass of Chunkable3 works too. Thanks, -Brian _________________________________________________________________ More than messages–check out the rest of the Windows Live™. http://www.microsoft.com/windows/windowslive/