Module K := knot_full_variant.KnotFull(Input)(Output).
Definition knot := K.knot.
Definition ageable_knot := K.ageable_knot.
Definition squash: (nat * KI.F (pred knot)) -> knot := K.squash.
Definition unsquash: knot -> (nat * KI.F (pred knot)) := K.unsquash.
Definition approx: nat -> pred knot -> pred knot := K.approx.

Lemma approx_spec : forall n p k,
approx n p k = (level k < n /\ p k).