Re: [Haskell-cafe] more thoughts on "Finally tagless"

Tom Schrijvers wrote:

data EvalDict sem = EvalDict { val :: Int -> sem Int, add :: sem Int -> sem Int -> sem Int }

An alternative option is to capture the structure in a GADT:

data Eval a where Val :: Int -> Eval Int Add :: Eval Int -> Eval Int -> Eval Int

And then write what were instances before as functions Eval a -> whatever. Of course, this makes it harder to combine multiple models. Martijn.