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(* as published by the Free Software Foundation; either version 2.1   *)
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(* GNU General Public License for more details.                       *)
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(* 02110-1301 USA                                                     *)
(* conservation de l'invariant de compatibilité par rapport à une signature pour l'union *)

Lemma union_mpl_correct_wrt_sign_invar_1 :
forall (s0 s1 : state) (pa : pre_ad) (sigma : signature),
state_correct_wrt_sign_with_offset s0 sigma pa ->
state_correct_wrt_sign_with_offset s1 sigma pa ->
state_correct_wrt_sign_with_offset (union_mpl s0 s1) sigma pa.