proposition: Lemma lex_intro : forall a a' b b', gtA a a' \/ (eqA a a' /\ gtB b b') -> lex (a,b) (a',b').
proof: Proof. intros. destruct H. apply lex1. exact H. destruct H. apply lex2. exact H. exact H0. Qed.
imports: Coq(Morphisms Basics) CoLoR(SN LogicUtil NatUtil VecUtil VecOrd ListUtil RelUtil)