Proof with auto with typeclass_instances.
intros Y.
assert ((fexp (ln_beta beta (F2R u) - 1) <= fexp (ln_beta beta (F2R u))))%Z.
2: omega.
destruct (ln_beta beta x) as (e,He).
rewrite Rabs_right in He.
2: now left.
assert (e <= fexp e)%Z.
apply exp_small_round_0_pos with beta (Zfloor) x...
now apply He, Rgt_not_eq.
now rewrite <- d_eq, Y.
rewrite u_eq, round_UP_small_pos with (ex:=e); trivial.
2: now apply He, Rgt_not_eq.
rewrite ln_beta_bpow.
ring_simplify (fexp e + 1 - 1)%Z.
replace (fexp (fexp e)) with (fexp e).
case exists_NE_; intros V.
contradict V; rewrite Even_beta; discriminate.
rewrite (proj2 (V e)); omega.
apply sym_eq, valid_exp; omega.
Qed.

(* Specifications: *)
Lemma Fm:  generic_format beta fexpe m.
case (d_ge_0); intros Y.