some renaming and a minor addition

[helm.git] / matita / matita / contribs / lambdadelta / basic_2 / multiple / mr2.ma

diff --git a/matita/matita/contribs/lambdadelta/basic_2/multiple/mr2.ma b/matita/matita/contribs/lambdadelta/basic_2/multiple/mr2.ma
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+(**************************************************************************)
+(*       ___                                                              *)
+(*      ||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 "basic_2/notation/relations/rat_3.ma".
+include "basic_2/grammar/term_vector.ma".
+
+(* MULTIPLE RELOCATION WITH PAIRS *******************************************)
+
+inductive at: list2 nat nat → relation nat ≝
+| at_nil: ∀i. at (⟠) i i
+| at_lt : ∀des,d,e,i1,i2. i1 < d →
+          at des i1 i2 → at ({d, e} @ des) i1 i2
+| at_ge : ∀des,d,e,i1,i2. d ≤ i1 →
+          at des (i1 + e) i2 → at ({d, e} @ des) i1 i2
+.
+
+interpretation "application (multiple relocation with pairs)"
+   'RAt i1 des i2 = (at des i1 i2).
+
+(* Basic inversion lemmas ***************************************************)
+
+fact at_inv_nil_aux: ∀des,i1,i2. @⦃i1, des⦄ ≡ i2 → des = ⟠ → i1 = i2.
+#des #i1 #i2 * -des -i1 -i2
+[ //
+| #des #d #e #i1 #i2 #_ #_ #H destruct
+| #des #d #e #i1 #i2 #_ #_ #H destruct
+]
+qed-.
+
+lemma at_inv_nil: ∀i1,i2. @⦃i1, ⟠⦄ ≡ i2 → i1 = i2.
+/2 width=3 by at_inv_nil_aux/ qed-.
+
+fact at_inv_cons_aux: ∀des,i1,i2. @⦃i1, des⦄ ≡ i2 →
+                      ∀d,e,des0. des = {d, e} @ des0 →
+                      i1 < d ∧ @⦃i1, des0⦄ ≡ i2 ∨
+                      d ≤ i1 ∧ @⦃i1 + e, des0⦄ ≡ i2.
+#des #i1 #i2 * -des -i1 -i2
+[ #i #d #e #des #H destruct
+| #des1 #d1 #e1 #i1 #i2 #Hid1 #Hi12 #d2 #e2 #des2 #H destruct /3 width=1 by or_introl, conj/
+| #des1 #d1 #e1 #i1 #i2 #Hdi1 #Hi12 #d2 #e2 #des2 #H destruct /3 width=1 by or_intror, conj/
+]
+qed-.
+
+lemma at_inv_cons: ∀des,d,e,i1,i2. @⦃i1, {d, e} @ des⦄ ≡ i2 →
+                   i1 < d ∧ @⦃i1, des⦄ ≡ i2 ∨
+                   d ≤ i1 ∧ @⦃i1 + e, des⦄ ≡ i2.
+/2 width=3 by at_inv_cons_aux/ qed-.
+
+lemma at_inv_cons_lt: ∀des,d,e,i1,i2. @⦃i1, {d, e} @ des⦄ ≡ i2 →
+                      i1 < d → @⦃i1, des⦄ ≡ i2.
+#des #d #e #i1 #e2 #H
+elim (at_inv_cons … H) -H * // #Hdi1 #_ #Hi1d
+lapply (le_to_lt_to_lt … Hdi1 Hi1d) -Hdi1 -Hi1d #Hd
+elim (lt_refl_false … Hd)
+qed-.
+
+lemma at_inv_cons_ge: ∀des,d,e,i1,i2. @⦃i1, {d, e} @ des⦄ ≡ i2 →
+                      d ≤ i1 → @⦃i1 + e, des⦄ ≡ i2.
+#des #d #e #i1 #e2 #H
+elim (at_inv_cons … H) -H * // #Hi1d #_ #Hdi1
+lapply (le_to_lt_to_lt … Hdi1 Hi1d) -Hdi1 -Hi1d #Hd
+elim (lt_refl_false … Hd)
+qed-.