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.
Definition compress := mk (M.set a b uf.(m)) compress_wf.

Lemma repr_compress:
forall x, repr compress x = repr uf x.