Instance Inhabitant_hist_el : Inhabitant hashtable_hist_el := HGet 0 0.

Lemma only_one_add_succeeds : forall k v1 v2 l i1 i2 H0 H (HH : apply_hist H0 l = Some H) (Hin1 : Znth i1 l = HAdd k v1 true) (Hin2 : Znth i2 l = HAdd k v2 true), i2 = i1 /\ v2 = v1.