[Haskell-cafe] closed classes

[Ketil Malde]

Duncan Coutts <duncan.coutts at worcester.oxford.ac.uk> 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.

-ketil
-- 
If I haven't seen further, it is by standing in the footprints of giants