proposition: Lemma nil_length: forall A (l : list A), 0 = length l -> l = nil.
proof: Proof. intuition. unfold length in H. destruct l;trivial. inversion H. Qed.
imports: Coq(List) JML(Stack) Coq(ListSet) Coq(Bool) Coq(ZArith) Coq(Relation_Operators) JML(ListHelpers) Coq(Classical) Coq(DecidableType) Coq(FSetInterface) Coq(FSetProperties) Coq(FSetEqProperties) Coq(FSetFacts) Coq(Sumbool) Coq(Lia)