-
-lemma lift_app: ∀M,N,k,p.
- lift (App M N) k p = App (lift M k p) (lift N k p).
-// qed.
-
-lemma lift_lambda: ∀N,M,k,p. lift (Lambda N M) k p =
- Lambda (lift N k p) (lift M (k + 1) p).
-// qed.
-
-lemma lift_prod: ∀N,M,k,p.
- lift (Prod N M) k p = Prod (lift N k p) (lift M (k + 1) p).
-// qed.
-
-lemma subst_app: ∀M,N,k,L. (App M N)[k≝L] = App M[k≝L] N[k≝L].
-// qed.
-
-lemma subst_lambda: ∀N,M,k,L. (Lambda N M)[k≝L] = Lambda N[k≝L] M[k+1≝L].
-// qed.
-
-lemma subst_prod: ∀N,M,k,L. (Prod N M)[k≝L] = Prod N[k≝L] M[k+1≝L].
-// qed.
-
-
-axiom lift_subst_lt: ∀A,B,i,j,k. lift (B[j≝A]) (j+k) i =
- (lift B (j+k+1) i)[j≝lift A k i].
-
-(* telescopic delifting substitution of l in M.
- * Rel 0 is replaced with the head of l
- *)
-let rec tsubst M l on l ≝ match l with
- [ nil ⇒ M
- | cons A D ⇒ (tsubst M[0≝A] D)
- ].
-
-interpretation "telescopic substitution" 'Subst1 M l = (tsubst M l).
-
-lemma tsubst_refl: ∀l,t. (lift t 0 (|l|))[l] = t.
-#l elim l -l; normalize // #hd #tl #IHl #t cut (S (|tl|) = |tl| + 1) // (**) (* eliminate cut *)
-qed.
-
-lemma tsubst_sort: ∀n,l. (Sort n)[l] = Sort n.
-// qed.