lawbreakers in Text.PrettyPrint.HughesPJ

[Christian Maeder]

Conal Elliott wrote:
>> Can you construct an example [...]
> 
>     Prelude Text.PrettyPrint> isEmpty (empty<>empty)
>     False

Indeed, isEmpty seems to be the problem that needs a fix:

   isEmpty d     = case reduceDoc d of
                 Empty -> True
                 _ -> False

Christian