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(************************************************************************)
(* v * The Coq Proof Assistant / The Coq Development Team *)
(* <O___,, * CNRS-Ecole Polytechnique-INRIA Futurs-Universite Paris Sud *)
(* \VV/ **************************************************************)
(* // * This file is distributed under the terms of the *)
(* * GNU Lesser General Public License Version 2.1 *)
(************************************************************************)
(*i $Id: Zerob.v,v 1.8.2.1 2004/07/16 19:31:03 herbelin Exp $ i*)
Require Import Arith.
Require Import Bool.
Open Local Scope nat_scope.
Definition zerob (n:nat) : bool :=
match n with
| O => true
| S _ => false
end.
Lemma zerob_true_intro : forall n:nat, n = 0 -> zerob n = true.
destruct n; [ trivial with bool | inversion 1 ].
Qed.
Hint Resolve zerob_true_intro: bool.
Lemma zerob_true_elim : forall n:nat, zerob n = true -> n = 0.
destruct n; [ trivial with bool | inversion 1 ].
Qed.
Lemma zerob_false_intro : forall n:nat, n <> 0 -> zerob n = false.
destruct n; [ destruct 1; auto with bool | trivial with bool ].
Qed.
Hint Resolve zerob_false_intro: bool.
Lemma zerob_false_elim : forall n:nat, zerob n = false -> n <> 0.
destruct n; [ intro H; inversion H | auto with bool ].
Qed.
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