X-Git-Url: http://matita.cs.unibo.it/gitweb/?a=blobdiff_plain;f=matita%2Fmatita%2Fcontribs%2Flambdadelta%2Fdelayed_updating%2Fsyntax%2Fpreterm.ma;h=6406d1dd7e50900f498b1832728315c5701e89e9;hb=829e3a8af3229c4e625245f7265dd67939da98c4;hp=9da0aa838e6f1a9b018063deb566c83d615aa80f;hpb=cfd201c62dd9b854bfb4ada648d3e556b29fac3a;p=helm.git

diff --git a/matita/matita/contribs/lambdadelta/delayed_updating/syntax/preterm.ma b/matita/matita/contribs/lambdadelta/delayed_updating/syntax/preterm.ma
index 9da0aa838..6406d1dd7 100644
--- a/matita/matita/contribs/lambdadelta/delayed_updating/syntax/preterm.ma
+++ b/matita/matita/contribs/lambdadelta/delayed_updating/syntax/preterm.ma
@@ -14,21 +14,28 @@
 
 include "delayed_updating/syntax/prototerm.ma".
 include "delayed_updating/syntax/path_structure.ma".
-include "delayed_updating/notation/relations/predicate_t_hook_1.ma".
+include "delayed_updating/notation/functions/class_t_0.ma".
 
 (* PRETERM ******************************************************************)
 
+(* Note: a preterm is a prototerm satislying the condition below *)
 (* Note: different root paths have different structure *)
 definition structure_injective: predicate prototerm ≝
            λt. ∀p1,p2. p1 ϵ ▵t → p2 ϵ ▵t → ⊗p1 = ⊗p2 → p1 = p2
 .
 
-(* Note: a preterm is a prototerm satislying the conditions above *)
-record is_preterm (t): Prop ≝
-{
-  is_pt_injective: structure_injective t
-}.
-
 interpretation
-  "preterm condition (prototerm)"
-  'PredicateTHook t = (is_preterm t).
+  "preterm (prototerm)"
+  'ClassT = (structure_injective).
+
+(* Basic inversions *********************************************************)
+
+lemma preterm_in_root_append_inv_structure_empty_dx (t) (p) (q):
+      p●q ϵ ▵t → t ϵ 𝐓 → 𝐞 = ⊗q → 𝐞 = q.
+#t #p #q #Hpq #Ht #Hq
+lapply (Ht p ?? Hpq ?)
+[ <structure_append //
+| /2 width=2 by prototerm_in_root_append_des_sn/
+| /2 width=3 by eq_inv_list_append_dx_dx_refl/
+]
+qed-.