[Haskell-cafe] Trying to make a Typeable instance

[Neil Mitchell]

Hi

> data ListGT map k a
>   = Empt
>   | BraF ![k] a !(map (ListGT map k a))
>   | BraE ![k]   !(map (ListGT map k a))
>    deriving( Typeable )

Not in Haskell, only in GHC.

Thanks

Neil

>
> ?
>
> On 7/7/07, Adrian Hey <ahey at iee.org> wrote:
> > Hello,
> >
> > I'm trying to make the type (ListGT map k a) an instance of Typeable,
> > where map is kind (* -> *).
> >
> > data ListGT map k a
> >   = Empt
> >   | BraF ![k] a !(map (ListGT map k a))
> >   | BraE ![k]   !(map (ListGT map k a))
> >
> > I thought I'd cracked it with something like this..
> >
> > instance (Typeable (map (ListGT map k a)), Typeable k, Typeable a) =>
> >           Typeable (ListGT map k a) where
> >     typeOf lgt = mkTyConApp (mkTyCon " Data.Trie.General.ListGT")
> >                 [mTypeRep, kTypeRep, aTypeRep]
> >       where BraF [k] a m = lgt -- This is just to get types for k a m !!
> >             kTypeRep = typeOf k
> >             aTypeRep = typeOf a
> >             mTypeRep = typeOf m
> >
> > However, showing the resulting TypRep gives a stack overflow. I wasn't
> > too surprised about this, so I tried replacing the last line with..
> >             mTypeRep = mkTyConApp (typeRepTyCon (typeOf m)) []
> > ..thinking that this would make it terminate. But it doesn't.
> >
> > Could someone explain how to do this?
> >
> > Thanks
> > --
> > Adrian Hey
> >
> >
> > _______________________________________________
> > Haskell-Cafe mailing list
> > Haskell-Cafe at haskell.org
> > http://www.haskell.org/mailman/listinfo/haskell-cafe
> >
>
>
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