Section Fprop_divsqrt_error.
Variable beta : radix.
Notation bpow e := (bpow beta e).
Variable prec : Z.

Lemma generic_format_plus_prec :
forall fexp, (forall e, (fexp e <= e - prec)%Z) ->
forall x y (fx fy: float beta),
(x = F2R fx)%R -> (y = F2R fy)%R -> (Rabs (x+y) < bpow (prec+Fexp fx))%R ->
(Rabs (x+y) < bpow (prec+Fexp fy))%R ->
generic_format beta fexp (x+y)%R.