intros dPos; apply ln_beta_unique_pos.
split.
apply Rle_trans with (F2R d).
destruct (ln_beta beta (F2R d)) as (e,He).
simpl.
rewrite Rabs_right in He.
apply He.
now apply Rgt_not_eq.
apply Rle_ge; now left.
apply d_le_m.
case m_le_u; intros H.
apply Rlt_le_trans with (1:=H).
rewrite u_eq.
apply round_le_generic...
apply generic_format_bpow.
apply valid_exp.
apply ln_beta_generic_gt...
now apply Rgt_not_eq.
now apply generic_format_canonic.
case (Rle_or_lt x (bpow (ln_beta beta (F2R d)))); trivial; intros Z.
absurd ((bpow (ln_beta beta (F2R d)) <= (F2R d)))%R.
apply Rlt_not_le.
destruct  (ln_beta beta (F2R d)) as (e,He).
simpl in *; rewrite Rabs_right in He.
apply He.
now apply Rgt_not_eq.
apply Rle_ge; now left.
apply Rle_trans with (round beta fexp Zfloor x).
2: right; apply sym_eq, d_eq.
apply round_ge_generic...
apply generic_format_bpow.
apply valid_exp.
apply ln_beta_generic_gt...
now apply Rgt_not_eq.
now apply generic_format_canonic.
now left.
replace m with (F2R d).
destruct (ln_beta beta (F2R d)) as (e,He).
simpl in *; rewrite Rabs_right in He.
apply He.
now apply Rgt_not_eq.
apply Rle_ge; now left.
unfold m in H |- *.
lra.
Qed.

Lemma ln_beta_m_0: (0 = F2R d)%R
-> (ln_beta beta m =ln_beta beta (F2R u)-1:>Z)%Z.