Re: [Haskell-cafe] closed classes

Ketil Malde writes:

Duncan Coutts writes:

...

closed class GConfValue v where

Hmm...doesn't

--8<-- module Closed(foo) where class C a where foo = ... instance C ... --8<-- module Main where import Closed ...foo... --8<--

do what you want? You can only use existing instances of C, but not declare them (outside of the Closed module), IIUC.

Ah, but now you cannot use (Closed t) => as a predicate in type signatures, and since you cannot write a partial signature, you must omit the signature altogether... Regards, Malcolm