update in ground

[helm.git] / matita / matita / contribs / lambdadelta / ground / lib / list_tl.ma

diff --git a/matita/matita/contribs/lambdadelta/ground/lib/list_tl.ma b/matita/matita/contribs/lambdadelta/ground/lib/list_tl.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 "ground/notation/functions/downharpoonright_2.ma".
+include "ground/lib/list.ma".
+
+(* TAIL FOR LISTS ***********************************************************)
+
+definition list_tl (A:Type[0]): list A → list A.
+#A * [ @(ⓔ) | #_ #t @t ]
+defined.
+
+interpretation
+  "tail (streams)"
+  'DownHarpoonRight A t = (list_tl A t).
+
+(* Basic constructions ******************************************************)
+
+lemma list_tl_empty (A):
+      ⓔ = ⇂{A}ⓔ.
+// qed.
+
+lemma list_tl_lcons (A) (a) (t):
+      t = ⇂{A}(a⨮t).
+// qed.