Definition pLhalf : pshare := fst (split_pshare pfullshare).Definition pRhalf : pshare := snd (split_pshare pfullshare).

(* Specifications: *)
Lemma pleftright : join pLhalf pRhalf pfullshare.
Lemma pshare_nonunit: forall sh: pshare, nonunit (pshare_sh sh).
Lemma pshare_not_identity: forall sh: pshare, ~ identity (pshare_sh sh).