Section ReductionEncodings.
Context {X: Const}.
Definition finst I n := Lambda n (AppL (map var I) (@var X n)).

Lemma finst_equivalence u v I W delta:
I ⊆ nats (length W) ->
AppR (ren delta (finst I (length W))) (Enc u v W) ≡ enc u v (concat (select I W)) (var (delta 0)).