That pattern looks so familiar. :) Existential types seem to fit in to the type system really well so I never got why it is not part of the standard. On Aug 12, 2012 10:36 AM, "Daniel Trstenjak" <daniel.trsten...@gmail.com> wrote:
> > Hi Oleg, > > On Sat, Aug 11, 2012 at 08:14:47AM -0000, o...@okmij.org wrote: > > I'd like to point out that the only operation we can do on the first > > argument of MkFoo is to show to it. This is all we can ever do: > > we have no idea of its type but we know we can show it and get a > > String. Why not to apply show to start with (it won't be evaluated > > until required anyway)? > > It's only a test case. The real thing is for a game and will be > something like: > > class EntityT e where > update :: e -> e > > render :: e -> IO () > > handleEvent :: e -> Event -> e > > getBound :: e -> Maybe Bound > > > data Entity = forall e. (EntityT e) => Entity e > > data Level = Level { > entities = [Entity], > ... > } > > > Greetings, > Daniel > > _______________________________________________ > Haskell-Cafe mailing list > Haskell-Cafe@haskell.org > http://www.haskell.org/mailman/listinfo/haskell-cafe >
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