Ltac simpl_of_lu :=
match goal with
| |- context [ of_lu (?f ?x) ] =>
rewrite (of_lu_eqn (f x)); simpl hd; simpl tl
end.

Lemma of_lu_revapp d d' :
of_lu (revapp d d') =
of_lu (rev d) + of_lu d' * 10^usize d.