De Bruijn indices

module Main

import Data.Fin

data Term : Nat -> Type where
  BVar : Fin n -> Term n
  FVar : String -> Term n
  Abs : Term (n + 1) -> Term n
  App : Term n -> Term n -> Term n

exampleId : Term 0
exampleId = Abs (BVar 0)

exampleConst : Term 0
exampleConst = Abs (Abs (BVar 1))

-- exampleIll : Term 0
-- exampleIll = BVar 0

main : IO ()
main = putStrLn "Hello World!"