update in delayed updating

[helm.git] / matita / matita / contribs / lambdadelta / delayed_updating / syntax / path_structure.ma

diff --git a/matita/matita/contribs/lambdadelta/delayed_updating/syntax/path_structure.ma b/matita/matita/contribs/lambdadelta/delayed_updating/syntax/path_structure.ma
new file mode 100644 (file)
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+++ b/matita/matita/contribs/lambdadelta/delayed_updating/syntax/path_structure.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 "delayed_updating/syntax/path.ma".
+include "delayed_updating/notation/functions/circled_times_1.ma".
+
+(* STRUCTURE FOR PATH *******************************************************)
+
+rec definition path_structure (p) on p ≝
+match p with
+[ list_empty     ⇒ 𝐞
+| list_lcons l q ⇒
+   match l with
+   [ label_node_d n ⇒ path_structure q
+   | label_edge_L   ⇒ 𝗟;path_structure q
+   | label_edge_A   ⇒ 𝗔;path_structure q
+   | label_edge_S   ⇒ 𝗦;path_structure q
+   ]
+].
+
+interpretation
+  "structure (path)"
+  'CircledTimes p = (path_structure p).