proposition: Lemma big_seq (I : eqType) (r : seq I) F : \big[op/idx]_(i <- r) F i = \big[op/idx]_(i <- r | i \in r) F i.
proof: Proof. by rewrite big_seq_cond big_andbC. Qed.
imports: HB(structures) mathcomp(ssreflect ssrbool ssrfun eqtype ssrnat seq path) mathcomp(div fintype tuple finfun)