proposition: Lemma splitP p x (i := index x p) : x \in p -> split x p (take i p) (drop i.+1 p).
proof: Proof. rewrite -has_pred1 => /split_find[? ? ? /eqP->]. by rewrite has_pred1; constructor. Qed.
imports: Coq(Setoid Morphisms) mathcomp(all_ssreflect) GraphTheory(edone)