(** Checks that all members of a list are P *)
Fixpoint alllist (A : Set) (P : A -> Prop) (qlist : list A) {struct qlist} :
Prop :=
match qlist with
| Nil => True
| Cons m l => P m /\ alllist A P l
end.

Lemma alllist_dec :
forall (A : Set) (P : A -> Prop) (l : list A),
(forall x : A, P x \/ ~ P x) -> alllist A P l \/ ~ alllist A P l.