(**************************************************)
(*  some decidability properties                  *)
(**************************************************)

Lemma assoc_add_hasmem_choice :
forall (b0 b : assoc) (k k0 : K) (v v0 : V),
b = assoc_add b0 k0 v0 ->
assoc_hasmem b k v -> assoc_hasmem b0 k v \/ k = k0 /\ v = v0.