Section COMPRESS.
Variable uf: t.
Variable a b: elt.
Hypothesis a_diff_b: a <> b.
Hypothesis a_repr_b: repr uf a = b.
Remark compress_Acc:
forall x,
Acc (order uf.(m)) x -> Acc (order (M.set a b uf.(m))) x.

Lemma compress_wf:
well_founded (order (M.set a b uf.(m))).