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(*         *   The Coq Proof Assistant / The Coq Development Team       *)
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(* (c) Copyright 2006-2016 Microsoft Corporation and Inria.                  *)
Goal forall m n p, n <= p -> m <= n -> m <= p.
by move=> m n p le_n_p /leq_trans; apply.
Undo 1.
by move=> m n p le_n_p /leq_trans /(_ le_n_p) le_m_p; exact: le_m_p.
Undo 1.
by move=> m n p le_n_p /leq_trans ->.
Qed.
Goal forall P Q X : Prop, Q -> (True -> X -> Q = P) -> X -> P.
by move=> P Q X q V /V <-.
Qed.

Lemma test0: forall a b, a && a && b -> b.