Interpreter mit Funktionen

abstrakte Syntax:

data Exp = ...
  | Abs { formal :: Name , body :: Exp }
  | App { rator  :: Exp  , rand :: Exp }

konkrete Syntax:

let { f = \ x -> x * x }  in  f (f 3)

konkrete Syntax (Alternative):

let { f x = x * x }  in  f (f 3)