proposition: Lemma itv_splitI bl br x : x \in Interval bl br = (x \in Interval bl +oo) && (x \in Interval -oo br).
proof: Proof. by rewrite !itv_boundlr andbT. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq choice) mathcomp(div fintype bigop order ssralg finset fingroup) mathcomp(ssrnum)