proposition: Lemma big_cons : forall i r (P : pred I) F, let x := \big[op/idx]_(j <- r | P j) F j in \big[op/idx]_(j <- i :: r | P j) F j === if P i then op (F i) x else x.
proof: Proof. by reflexivity. Qed.
imports: ssreflect ssrbool ssrfun eqtype ssrnat seq div choice fintype finfun paths Setoid Morphisms OperationClasses bigops