adam vogt
You need to write an instance of TCode for every different "effect" included in the union for the lookup to work. ...
thanks for the explanation; the Includes instances make more sense now
I think you're better off depending on a
type family Eq :: Bool where Eq x x = True Eq x y = False
Or the equivalent with overlapping instances if the code is supposed to work with ghc-7.6.
yes, i've updated the code on hackage to fall back on the overlapping instances implementation for ghc-7.6
Another objection about TList is that it is a linked list, so operations with types at the "end" of the union are probably relatively slow at runtime, since you end up pattern matching on "n" T constructors in some cases.
that may just be a limitation for the code being written for ghc-7.4 iiuc
It might be faster to have more of that traversal done at compile time as in:
thanks for the additional reference. i've been meaning to read up on HList; perhaps this will be my segue
Or with unions that use Typeable.
actually with Typeable being kind polymorphic in ghc-7.8, the improved deriving code, -XAutoDeriveTypeable and -XStandaloneDeriving i don't see much of a drawback with the above approach.
I'm not sure about your other questions.
yes, they were more directed at oleg (in the cc), but figured others might have made their way through these waters before me, so it couldn't hurt to ask. cheers -- Suhail