proposition: Lemma InA_app_nil_l z l : InA eqA z ([] ++ l) ↔ InA eqA z l.
proof: Proof. firstorder. Qed.
imports: Coq.Lists.List Coq.Lists.SetoidList MathClasses.interfaces.abstract_algebra MathClasses.interfaces.monads MathClasses.theory.monads