proposition: Lemma big_ord_widen : forall n1 n2 (F : nat -> A), n1 <= n2 -> \big[op/idx]_(i < n1) F i === \big[op/idx]_(i < n2 | i < n1) F i.
proof: Proof. by move=> *; apply: (big_ord_widen_cond (predT)). Qed.
imports: ssreflect ssrbool ssrfun eqtype ssrnat seq div choice fintype finfun paths Setoid Morphisms OperationClasses bigops