proposition: Lemma eq_bigr r (P : pred I) F1 F2 : (forall i, P i -> F1 i = F2 i) -> \big[op/idx]_(i <- r | P i) F1 i = \big[op/idx]_(i <- r | P i) F2 i.
proof: Proof. by move=> eqF12; elim/big_rec2: _ => // i x _ /eqF12-> ->. Qed.
imports: HB(structures) mathcomp(ssreflect ssrbool ssrfun eqtype ssrnat seq path) mathcomp(div fintype tuple finfun)