14 Oct
2008
14 Oct
'08
10:37 p.m.
On Tue, Oct 14, 2008 at 8:20 PM, George Pollard
Illegal instance declaration for `Stringable [Char]' (All instance types must be of the form (T a1 ... an) where a1 ... an are distinct type *variables* Use -XFlexibleInstances if you want to disable this.) In the instance declaration for `Stringable [Char]'
'Blah' isn't a type variable, is it? Is my brain just not working right today?
If you're stuck, this is a fairly arbitrary limitation and is easily generalized. GHC, at least, implements the FlexibleInstances extension. Put {-# LANGUAGE FlexibleInstances #-} At the top of the file and that will be an acceptable instance. Luke