proposition: Lemma bigcap_inf j P F : P j -> \bigcap_(i | P i) F i \subset F j.
proof: Proof. by move=> Pj; rewrite (bigD1 j) //= subsetIl. Qed.
imports: HB(structures) mathcomp(ssreflect ssrbool ssrfun eqtype ssrnat div seq) mathcomp(choice fintype finfun bigop)