Instance Inhabitant_hist_el : Inhabitant hashtable_hist_el := HGet 0 0.

Lemma one_add_succeeds : forall k v b l H0 H (HH : apply_hist H0 l = Some H) (Hk : H0 k = None)
(Hin : In (HAdd k v b) l) (Hout : forall v, ~In (HSet k v) l), exists v', In (HAdd k v' true) l.