Definition double_round_sqrt_hyp fexp1 fexp2 :=
  (forall ex, (2 * fexp1 ex <= fexp1 (2 * ex))%Z)
  /\ (forall ex, (2 * fexp1 ex <= fexp1 (2 * ex - 1))%Z)
  /\ (forall ex, (fexp1 (2 * ex) < 2 * ex)%Z ->
                 (fexp2 ex + ex <= 2 * fexp1 ex - 2)%Z).

Lemma double_round_sqrt : forall fexp1 fexp2 : Z -> Z, Valid_exp fexp1 -> Valid_exp fexp2 -> forall (choice1 choice2 : Z -> bool), double_round_sqrt_hyp fexp1 fexp2 -> forall x, generic_format beta fexp1 x -> double_round_eq fexp1 fexp2 choice1 choice2 (sqrt x).