--- /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 "static_2/syntax/tweq_tweq.ma".
+include "static_2/relocation/lifts_tweq.ma".
+include "basic_2/rt_transition/cpr_drops_basic.ma".
+include "basic_2/rt_computation/cpms.ma".
+
+(* CONTEXT-SENSITIVE PARALLEL R-COMPUTATION FOR TERMS ***********************)
+
+(* Properties with sort-irrelevant whd equivalence on terms *****************)
+
+lemma cprs_abbr_pos_twneq (h) (G) (L) (V) (T1):
+ ∃∃T2. ⦃G,L⦄ ⊢ +ⓓV.T1 ➡*[h] T2 & (+ⓓV.T1 ≅ T2 → ⊥).
+#h #G #L #V #U1
+elim (cpr_subst h G (L.ⓓV) U1 … 0) [|*: /2 width=4 by drops_refl/ ] #U2 #T2 #HU12 #HTU2
+elim (tweq_dec U1 U2) [ #HpU12 | -HTU2 #HnU12 ]
+[ @(ex2_intro … T2) (**) (* full auto not tried *)
+ [ /3 width=6 by cpms_zeta, cpms_step_sn, cpm_bind/
+ | /4 width=6 by tweq_inv_abbr_pos_x_lifts_y_y, tweq_canc_sn, tweq_abbr_pos/
+ ]
+| /4 width=3 by cpm_cpms, cpm_bind, tweq_inv_abbr_pos_bi, ex2_intro/
+]
+qed-.