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"
Hi Oleg,
On Sat, Aug 11, 2012 at 08:14:47AM -0000, oleg@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
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