proposition: Lemma big_all_cond : \big[andb/true]_(i <- r | P i) B i = all [pred i | P i ==> B i] r.
proof: Proof. by rewrite big_mkcond unlock. Qed.
imports: HB(structures) mathcomp(ssreflect ssrbool ssrfun eqtype ssrnat seq path) mathcomp(div fintype tuple finfun)