matita/matita/contribs/lambdadelta/delayed_updating/syntax/path_head_structure.ma

   1 (**************************************************************************)
   2 (*       ___                                                              *)
   3 (*      ||M||                                                             *)
   4 (*      ||A||       A project by Andrea Asperti                           *)
   5 (*      ||T||                                                             *)
   6 (*      ||I||       Developers:                                           *)
   7 (*      ||T||         The HELM team.                                      *)
   8 (*      ||A||         http://helm.cs.unibo.it                             *)
   9 (*      \   /                                                             *)
  10 (*       \ /        This file is distributed under the terms of the       *)
  11 (*        v         GNU General Public License Version 2                  *)
  12 (*                                                                        *)
  13 (**************************************************************************)
  14
  15 include "delayed_updating/syntax/path_head.ma".
  16 include "delayed_updating/syntax/path_structure.ma".
  17 include "delayed_updating/syntax/path_depth.ma".
  18
  19 (* HEAD FOR PATH ************************************************************)
  20
  21 (* Constructions with structure *********************************************)
  22
  23 axiom path_head_structure (p) (q):
  24       ⊗p = ↳[♭⊗p]((⊗p)●q).
  25 (*
  26 #p elim p -p
  27 [ #q <path_head_zero //
  28 | * [ #n ] #p #IH #q
  29   [ <structure_d_sn //
  30   | <structure_m_sn //
  31   | <structure_L_sn
  32   | <structure_A_sn <list_append_lcons_sn
  33     <path_head_A_sn //
  34   | <structure_S_sn //
  35   ]
  36 ]
  37 *)