[Haskell-cafe] type/class question: toString

Jeff Polakow jeff.polakow at db.com
Tue Nov 6 14:21:55 EST 2007


  Have you tried using -fglasgow-exts? That should enable all ghc 


haskell-cafe-bounces at haskell.org wrote on 11/06/2007 02:02:11 PM:

> On Nov 6, 2007 12:15 PM, David Benbennick <dbenbenn at gmail.com> wrote:
> > In ghc 6.8.1, the error messages are more helpful:
> >
> > foo.hs:5:0:
> >     Illegal instance declaration for `MyShow String'
> >         (All instance types must be of the form (T t1 ... tn)
> >          where T is not a synonym.
> >          Use -XTypeSynonymInstances if you want to disable this.)
> >     In the instance declaration for `MyShow String'
> Thanks for the tip. I might give 6.8.1 a try; I still cannot get it to
> work in 6.6.1. The problem may exist between the keyboard and the
> chair.
> G
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