Re: [Haskell-beginners] How to avoid repeating a type restriction from a data constructor

On Wednesday 24 April 2013, 10:35:34, gs wrote:

Daniel Fischer writes:

...

Use a GADT,

{-# LANGUAGE GADTs #-}

data Source x y where

Source :: Variable v => { bindings :: v [Binding a], var :: v a }

-> Source v a

I tried this, but every place that I remove the restriction Variable v => from something using Source, I get an error No instance for (Variable v) ...

Sounds like you're not pattern-matching on the `Source` constructor. Can you post some example code?