proposition: Lemma big_rec I r (P : pred I) F (Kop : forall i x, P i -> K x -> K (op (F i) x)) : K (\big[op/idx]_(i <- r | P i) F i).
proof: Proof. by rewrite unlock; elim: r => //= i r; case: ifP => //; apply: Kop. Qed.
imports: HB(structures) mathcomp(ssreflect ssrbool ssrfun eqtype ssrnat seq path) mathcomp(div fintype tuple finfun)