matita/matita/contribs/lambdadelta/static_2/syntax/tweq_tweq.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 "static_2/syntax/tweq.ma".
  16
  17 (* SORT-IRRELEVANT WHD EQUIVALENCE ON TERMS *********************************)
  18
  19 (* Main properties **********************************************************)
  20
  21 theorem tweq_trans: Transitive … tweq.
  22 #T1 #T #H elim H -T1 -T
  23 [ #s1 #s #X #H
  24   elim (tweq_inv_sort_sn … H) -s #s2 destruct
  25   /2 width=1 by tweq_sort/
  26 | #i1 #i #H //
  27 | #l1 #l #H //
  28 | #p #V1 #V #T1 #T #_ #IHT #X #H
  29   elim (tweq_inv_abbr_sn … H) -H #V2 #T2 #HT #H destruct
  30   /4 width=1 by tweq_abbr/
  31 | #p #V1 #V #T1 #T #X #H
  32   elim (tweq_inv_abst_sn … H) -H #V2 #T2 #H destruct
  33   /2 width=1 by tweq_abst/
  34 | #V1 #V #T1 #T #_ #IHT #X #H
  35   elim (tweq_inv_appl_sn … H) -H #V2 #T2 #HT #H destruct
  36   /3 width=1 by tweq_appl/
  37 | #V1 #V #T1 #T #_ #_ #IHV #IHT #X #H
  38   elim (tweq_inv_cast_sn … H) -H #V2 #T2 #HV #HT #H destruct
  39   /3 width=1 by tweq_cast/
  40 ]
  41 qed-.
  42
  43 theorem tweq_canc_sn: left_cancellable … tweq.
  44 /3 width=3 by tweq_trans, tweq_sym/ qed-.
  45
  46 theorem tweq_canc_dx: right_cancellable … tweq.
  47 /3 width=3 by tweq_trans, tweq_sym/ qed-.
  48
  49 theorem tweq_repl:
  50         ∀T1,T2. T1 ≅ T2 → ∀U1. T1 ≅ U1 → ∀U2. T2 ≅ U2 → U1 ≅ U2.
  51 /3 width=3 by tweq_canc_sn, tweq_trans/ qed-.