At Tue, 15 Jul 2008 09:43:40 -0400,
Jeff Polakow wrote:
> Hello,
Hi Jeff,
>
> > data LSet t where
> > Nil :: LSet Nil
> > --either add the new element or do nothing
> > Ins :: (Member a t b
> > , If b (LSet t) (LSet (a ::: t)) r)
> > => L a -> LSet t -> r
> >
> The constructor Ins needs to return an LSet. Maybe try replacing occurrences
> of r with (LSet r).
>
I expected that r would be an LSet, as its the output of If which
returns its 2nd or 3rd argument:
class If p x y z | p x y -> z
where if' :: p -> x -> y -> z
instance If T x y x
instance If F x y y
Jim
> -Jeff
>
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