Instance length_getSupport_nz : forall (A : Set)(c : Comp A),
  well_formed_comp c ->
  nz (length (getSupport c)).

Theorem low_tree_approx_same : forall n (A : Set)(eqd : eq_dec A)(c : Comp A)(t : DistApproxTree A), well_formed_comp c -> dat_correct c n t -> forall a, lowDistApprox c a n (lowDistApproxFromTree eqd t a).