Sorry, that should be (Const "="). The GADT is defined as follows: data Var a where MkVar :: (GType a) => String -> Var a data LTerm a where Var :: (GType a) => Var a -> LTerm a Const :: (GType a) => String -> LTerm a (:.) :: (GType a, GType b) => LTerm (a -> b) -> LTerm a -> LTerm b Abs :: (GType a, GType b) => Var a -> LTerm b -> LTerm (a -> b) infixl 6 :. (here i have used :. instead of App so that it is easier to read). I had to restrict types to the class (GType) of types that I have instantiated for comparison. On 6 Jul 2011, at 11:16, Henning Thielemann wrote:
On Wed, 6 Jul 2011, Ian Childs wrote:
Term a is meant to be the simply-typed lambda-calculus as a GADT. Then given two terms App (App "=" l1) r1, and App (App "=" l2) r2, I want to form App (App "=" (App l1 l2)) (App r1 r2), but as you can see this will only work if the types of l1 and l2, and r1 and r2, match as detailed previously. does that make sense?
What is App? It looks like you apply it once to a string ("=") and also to terms(?) like l1, r1. How is the GADT defined?