(* * Copyright (c) 2009 Robert Dockins and Aquinas Hobor. * *)
(* Coq development: using indirection theory to model types in l-calculus *)
(* lam_ref_mach_lemmas.v: various boring lemmas about the machine *)
(* COERCIONS *)
(* DECIDABILTY *)
(* SUBSTITUTION *)
(* STEP RELATION *)

Lemma closed_step : forall x y ,
step x y ->
closed (snd x) ->
closed (snd y).