intros rnd x Hx.
unfold round, scaled_mantissa.
rewrite canonic_exp_FLT_FLX ; trivial.
Qed.

Theorem generic_format_FLT_FIX :
forall x : R,
(Rabs x <= bpow (emin + prec))%R ->
generic_format beta (FIX_exp emin) x ->
generic_format beta FLT_exp x.