Definition pure {A}{JA: Join A}{PA: Perm_alg A}{SA: Sep_alg A}
     (P: pred A) : Prop :=
   P |-- emp.

Lemma ewand_TT_sepcon {T}{JT: Join T}{PT: Perm_alg T}{ST: Sep_alg T}: forall P Q R, (P * Q && ewand R (!!True))%pred |-- (P && ewand R (!!True) * (Q && ewand R (!!True)))%pred.