1 (**************************************************************************)
4 (* ||A|| A project by Andrea Asperti *)
6 (* ||I|| Developers: *)
7 (* ||T|| The HELM team. *)
8 (* ||A|| http://helm.cs.unibo.it *)
10 (* \ / This file is distributed under the terms of the *)
11 (* v GNU General Public License Version 2 *)
13 (**************************************************************************)
17 (* LENGTH *******************************************************************)
19 (* Note: this gives the number of abstractions and applications in M *)
20 let rec length M on M ≝ match M with
22 | Abst A ⇒ length A + 1
23 | Appl B A ⇒ (length B) + (length A) + 1
26 interpretation "term length"
29 lemma length_lift: ∀h,M,d. |↑[d, h] M| = |M|.
30 #h #M elim M -M normalize //