proposition: Lemma big_mkcondl_idem I r (P Q : pred I) F : \big[op/x]_(i <- r | P i && Q i) F i = \big[op/x]_(i <- r | Q i) (if P i then F i else x).
proof: Proof. by rewrite big_andbC big_mkcondr_idem. Qed.
imports: HB(structures) mathcomp(ssreflect ssrbool ssrfun eqtype ssrnat seq path) mathcomp(div fintype tuple finfun)