Fixpoint make_conj (A : Type) (eval : A -> Prop) (l : list A) {struct l} : Prop :=
  match l with
    | nil => True
    | cons e nil => (eval e)
    | cons e l2 => ((eval e) /\ (make_conj eval l2))
  end.

Lemma make_conj_in : forall (A : Type) (eval : A -> Prop) (l : list A), make_conj eval l -> (forall p, In p l -> eval p).