+++ /dev/null
-(**************************************************************************)
-(* ___ *)
-(* ||M|| *)
-(* ||A|| A project by Andrea Asperti *)
-(* ||T|| *)
-(* ||I|| Developers: *)
-(* ||T|| The HELM team. *)
-(* ||A|| http://helm.cs.unibo.it *)
-(* \ / *)
-(* \ / This file is distributed under the terms of the *)
-(* v GNU General Public License Version 2 *)
-(* *)
-(**************************************************************************)
-
-include "ground_2/ynat/ynat_lt.ma".
-include "basic_2/grammar/lenv.ma".
-
-(* LENGTH OF A LOCAL ENVIRONMENT ********************************************)
-
-let rec length L ≝ match L with
-[ LAtom ⇒ 0
-| LPair L _ _ ⇒ ⫯(length L)
-].
-
-interpretation "length (local environment)" 'card L = (length L).
-
-(* Basic properties *********************************************************)
-
-lemma length_atom: |⋆| = 0.
-// qed.
-
-lemma length_pair: ∀I,L,V. |L.ⓑ{I}V| = ⫯|L|.
-// qed.
-
-lemma length_inj: ∀L. |L| < ∞.
-#L elim L -L /2 width=1 by ylt_succ_Y/
-qed.
-
-(* Basic inversion lemmas ***************************************************)
-
-lemma length_inv_zero_dx: ∀L. |L| = 0 → L = ⋆.
-* // #L #I #V >length_pair
-#H elim (ysucc_inv_O_dx … H)
-qed-.
-
-lemma length_inv_zero_sn: ∀L. yinj 0 = |L| → L = ⋆.
-/2 width=1 by length_inv_zero_dx/ qed-.
-
-lemma length_inv_pos_dx: ∀l,L. |L| = ⫯l →
- ∃∃I,K,V. |K| = l & L = K. ⓑ{I}V.
-#l * /3 width=5 by ysucc_inj, ex2_3_intro/
->length_atom #H elim (ysucc_inv_O_sn … H)
-qed-.
-
-lemma length_inv_pos_sn: ∀l,L. ⫯l = |L| →
- ∃∃I,K,V. l = |K| & L = K. ⓑ{I}V.
-#l #L #H lapply (sym_eq ??? H) -H
-#H elim (length_inv_pos_dx … H) -H /2 width=5 by ex2_3_intro/
-qed-.