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).