-(**************************************************************************)
-(* ___ *)
-(* ||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/static/ssta.ma".
-include "basic_2/computation/cprs.ma".
-include "basic_2/equivalence/cpcs.ma".
-
-(* LOCAL ENVIRONMENT REFINEMENT FOR CONTEXT-SENSITIVE PARALLEL EQUIVALENCE **)
-
-(* Note: this is not transitive *)
-inductive lsubse (h:sh) (g:sd h): relation lenv ≝
-| lsubse_atom: lsubse h g (⋆) (⋆)
-| lsubse_pair: ∀I,L1,L2,V. lsubse h g L1 L2 →
- lsubse h g (L1. ⓑ{I} V) (L2. ⓑ{I} V)
-| lsubse_abbr: ∀L1,L2,V1,V2,W1,W2,l. L1 ⊢ W1 ⬌* W2 →
- ⦃h, L1⦄ ⊢ V1 •[g, l + 1] W1 → ⦃h, L2⦄ ⊢ W2 •[g, l] V2 →
- lsubse h g L1 L2 → lsubse h g (L1. ⓓV1) (L2. ⓛW2)
-.
-
-interpretation
- "local environment refinement (context-sensitive parallel equivalence)"
- 'CrSubEqSE h g L1 L2 = (lsubse h g L1 L2).
-
-(* Basic inversion lemmas ***************************************************)
-
-fact lsubse_inv_atom1_aux: ∀h,g,L1,L2. h ⊢ L1 ⊢•⊑[g] L2 → L1 = ⋆ → L2 = ⋆.
-#h #g #L1 #L2 * -L1 -L2
-[ //
-| #I #L1 #L2 #V #_ #H destruct
-| #L1 #L2 #V1 #V2 #W1 #W2 #l #_ #_ #_ #_ #H destruct
-]
-qed-.
-
-lemma lsubse_inv_atom1: ∀h,g,L2. h ⊢ ⋆ ⊢•⊑[g] L2 → L2 = ⋆.
-/2 width=5 by lsubse_inv_atom1_aux/ qed-.
-
-fact lsubse_inv_pair1_aux: ∀h,g,L1,L2. h ⊢ L1 ⊢•⊑[g] L2 →
- ∀I,K1,V1. L1 = K1. ⓑ{I} V1 →
- (∃∃K2. h ⊢ K1 ⊢•⊑[g] K2 & L2 = K2. ⓑ{I} V1) ∨
- ∃∃K2,W1,W2,V2,l. ⦃h, K1⦄ ⊢ V1 •[g,l+1] W1 & ⦃h, K2⦄ ⊢ W2 •[g,l] V2 &
- K1 ⊢ W1 ⬌* W2 & h ⊢ K1 ⊢•⊑[g] K2 & L2 = K2. ⓛW2 & I = Abbr.
-#h #g #L1 #L2 * -L1 -L2
-[ #J #K1 #U1 #H destruct
-| #I #L1 #L2 #V #HL12 #J #K1 #U1 #H destruct /3 width=3/
-| #L1 #L2 #V1 #V2 #W1 #W2 #l #HW12 #HVW1 #HWV2 #HL12 #J #K1 #U1 #H destruct /3 width=10/
-]
-qed-.
-
-lemma lsubse_inv_pair1: ∀h,g,I,K1,L2,V1. h ⊢ K1. ⓑ{I} V1 ⊢•⊑[g] L2 →
- (∃∃K2. h ⊢ K1 ⊢•⊑[g] K2 & L2 = K2. ⓑ{I} V1) ∨
- ∃∃K2,W1,W2,V2,l. ⦃h, K1⦄ ⊢ V1 •[g,l+1] W1 & ⦃h, K2⦄ ⊢ W2 •[g,l] V2 &
- K1 ⊢ W1 ⬌* W2 & h ⊢ K1 ⊢•⊑[g] K2 & L2 = K2. ⓛW2 & I = Abbr.
-/2 width=3 by lsubse_inv_pair1_aux/ qed-.
-
-fact lsubse_inv_atom2_aux: ∀h,g,L1,L2. h ⊢ L1 ⊢•⊑[g] L2 → L2 = ⋆ → L1 = ⋆.
-#h #g #L1 #L2 * -L1 -L2
-[ //
-| #I #L1 #L2 #V #_ #H destruct
-| #L1 #L2 #V1 #V2 #W1 #W2 #l #_ #_ #_ #_ #H destruct
-]
-qed-.
-
-lemma lsubse_inv_atom2: ∀h,g,L1. h ⊢ L1 ⊢•⊑[g] ⋆ → L1 = ⋆.
-/2 width=5 by lsubse_inv_atom2_aux/ qed-.
-
-fact lsubse_inv_pair2_aux: ∀h,g,L1,L2. h ⊢ L1 ⊢•⊑[g] L2 →
- ∀I,K2,W2. L2 = K2. ⓑ{I} W2 →
- (∃∃K1. h ⊢ K1 ⊢•⊑[g] K2 & L1 = K1. ⓑ{I} W2) ∨
- ∃∃K1,W1,V1,V2,l. ⦃h, K1⦄ ⊢ V1 •[g,l+1] W1 & ⦃h, K2⦄ ⊢ W2 •[g,l] V2 &
- K1 ⊢ W1 ⬌* W2 & h ⊢ K1 ⊢•⊑[g] K2 & L1 = K1. ⓓV1 & I = Abst.
-#h #g #L1 #L2 * -L1 -L2
-[ #J #K2 #U2 #H destruct
-| #I #L1 #L2 #V #HL12 #J #K2 #U2 #H destruct /3 width=3/
-| #L1 #L2 #V1 #V2 #W1 #W2 #l #HW12 #HVW1 #HWV2 #HL12 #J #K2 #U2 #H destruct /3 width=10/
-]
-qed-.
-
-lemma lsubse_inv_pair2: ∀h,g,I,L1,K2,W2. h ⊢ L1 ⊢•⊑[g] K2. ⓑ{I} W2 →
- (∃∃K1. h ⊢ K1 ⊢•⊑[g] K2 & L1 = K1. ⓑ{I} W2) ∨
- ∃∃K1,W1,V1,V2,l. ⦃h, K1⦄ ⊢ V1 •[g,l+1] W1 & ⦃h, K2⦄ ⊢ W2 •[g,l] V2 &
- K1 ⊢ W1 ⬌* W2 & h ⊢ K1 ⊢•⊑[g] K2 & L1 = K1. ⓓV1 & I = Abst.
-/2 width=3 by lsubse_inv_pair2_aux/ qed-.
-
-(* Basic_forward lemmas *****************************************************)
-
-lemma lsubse_fwd_lsubs1: ∀h,g,L1,L2. h ⊢ L1 ⊢•⊑[g] L2 → L1 ≼[0, |L1|] L2.
-#h #g #L1 #L2 #H elim H -L1 -L2 // /2 width=1/
-qed-.
-
-lemma lsubse_fwd_lsubs2: ∀h,g,L1,L2. h ⊢ L1 ⊢•⊑[g] L2 → L1 ≼[0, |L2|] L2.
-#h #g #L1 #L2 #H elim H -L1 -L2 // /2 width=1/
-qed-.
-
-(* Basic properties *********************************************************)
-
-lemma lsubse_refl: ∀h,g,L. h ⊢ L ⊢•⊑[g] L.
-#h #g #L elim L -L // /2 width=1/
-qed.
-
-lemma lsubse_cprs_trans: ∀h,g,L1,L2. h ⊢ L1 ⊢•⊑[g] L2 →
- ∀T1,T2. L2 ⊢ T1 ➡* T2 → L1 ⊢ T1 ➡* T2.
-/3 width=5 by lsubse_fwd_lsubs2, cprs_lsubs_trans/
-qed-.