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(** ** Local closure *)
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(** The local closure judgement classifies terms that have _no_ dangling indices.  Step through this derivation to see why the term [((\x. Y x) Y)] is locally closed. *)

(* Specifications: *)
Lemma demo_lc :
lc_exp (app (abs (app (var_f Y) (var_b 0))) (var_f Y)).