proposition: Lemma big_andbC r (P Q : pred I) F : \big[op/idx]_(i <- r | P i && Q i) F i = \big[op/idx]_(i <- r | Q i && P i) F i.
proof: Proof. by apply: eq_bigl => i; apply: andbC. Qed.
imports: HB(structures) mathcomp(ssreflect ssrbool ssrfun eqtype ssrnat seq path) mathcomp(div fintype tuple finfun)