matita/contribs/LOGIC/datatypes_defs/Formula.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
  16
  17 (* FORMULAE
  18    - Naming policy:
  19      - formulae: a b c d
  20 *)
  21
  22 include "preamble0.ma".
  23
  24 inductive Formula: Type \def
  25    | posr: Nat \to Formula
  26    | impl: Formula \to Formula \to Formula
  27 .