(** Square root *)
Definition Fsqrt_core_binary m e :=
let d := Zdigits2 m in
let s := Zmax (2 * prec - d) 0 in
let e' := (e - s)%Z in
let (s', e'') := if Zeven e' then (s, e') else (s + 1, e' - 1)%Z in
let m' :=
match s' with
| Zpos p => Z.shiftl m (Zpos p)
| _ => m
end in
let (q, r) := Z.sqrtrem m' in
let l :=
if Zeq_bool r 0 then loc_Exact
else loc_Inexact (if Zle_bool r q then Lt else Gt) in
(q, Zdiv2 e'', l).

Lemma Bsqrt_correct_aux :
forall m mx ex (Hx : bounded mx ex = true),
let x := F2R (Float radix2 (Zpos mx) ex) in
let z :=
let '(mz, ez, lz) := Fsqrt_core_binary (Zpos mx) ex in
match mz with
| Zpos mz => binary_round_aux m false mz ez lz
| _ => F754_nan false xH (* dummy *)
end in
valid_binary z = true /\
FF2R radix2 z = round radix2 fexp (round_mode m) (sqrt x) /\
is_finite_FF z = true /\ sign_FF z = false.