Definition hist_incl (h : hist_part) l := forall t e, h t = Some e -> nth_error l t = Some e.
Definition hist_list (h : hist_part) l := forall t e, h t = Some e <-> nth_error l t = Some e.

Corollary hist_ref_join_nil : forall sh p, sh <> Share.bot ->
ghost_hist sh empty_map p * ghost_ref [] p = ghost_hist_ref sh empty_map empty_map p.