Create basic lambda term type

src/Props/Lambda.hs

@@ -0,0 +1,23 @@
+{-# LANGUAGE OverloadedStrings #-}
+
+module Props.Lambda
+  ( Term(..)
+  , displayTerm
+  ) where
+
+import qualified Data.Set  as Set
+import qualified Data.Text as T
+
+type Name = T.Text
+type PreferredName = Maybe Name
+
+-- | Lambda calculus term using De Bruijn indexing
+data Term a
+  = Var PreferredName Int
+  | Lambda PreferredName (Term a)
+  | App (Term a) (Term a)
+  | Native a
+  deriving (Show)
+
+displayTerm :: (Set.Set Name -> a -> T.Text) -> Term a -> T.Text
+displayTerm = undefined