(* What identifiers are in scope in the various code sections? *)

let fun a() =
      let fun b() = a()+b()+c()+d()  (* -- code 1 *)
      in a()+b()+c()+d() end         (* -- code 2 *)
  and c() =
      let fun d() = a()+b()+c()+d()  (* -- code 3 *)
      in a()+b()+c()+d() end         (* -- code 4 *)
in a()+b()+c()+d() end               (* -- code 5 *)

(* This will not compile and it would not work if it did.    *)

(* EXERCISE: Predit ALL the compile-time erros, and          *)
(*           after you have done that confirm them with sml. *)