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(* File created for Coq V5.10.14b, Oct 1995 *)
(* Classical tactics for proving disjunctions by Julien Narboux, Jul 2005 *)
(* Inferred proof-irrelevance and eq_rect_eq added by Hugo Herbelin, Mar 2006 *)
(** Classical Propositional Logic *)
Hint Unfold not: core.
(** Peirce's law states [forall P Q:Prop, ((P -> Q) -> P) -> P]. Thanks to [forall P, False -> P], it is equivalent to the following form *)

Lemma imply_to_or : forall P Q:Prop, (P -> Q) -> ~ P \/ Q.