proposition: Lemma eq_fbigl (A B : {fset I}) (F : I -> R) : A =i B -> \big[op/idx]_(i <- A) F i = \big[op/idx]_(i <- B) F i.
proof: Proof. by move=> AB; apply: eq_fbig. Qed.
imports: HB(structures) mathcomp(ssreflect ssrbool ssrnat eqtype ssrfun seq) mathcomp(choice path finset finfun fintype bigop)