Definition Ztrunc x := if Rlt_bool x 0 then Zceil x else Zfloor x.

(* Specifications: *)
Theorem Ztrunc_Z2R :
forall n,
Ztrunc (Z2R n) = n.
Theorem Ztrunc_floor :
forall x,
(0 <= x)%R ->
Ztrunc x = Zfloor x.
Theorem Ztrunc_ceil :
forall x,
(x <= 0)%R ->
Ztrunc x = Zceil x.
Theorem Ztrunc_le :
forall x y, (x <= y)%R ->
(Ztrunc x <= Ztrunc y)%Z.
Theorem Ztrunc_opp :
forall x,
Ztrunc (- x) = Zopp (Ztrunc x).
Theorem Ztrunc_abs :
forall x,
Ztrunc (Rabs x) = Zabs (Ztrunc x).
Theorem Ztrunc_lub :
forall n x,
(Z2R n <= Rabs x)%R ->
(n <= Zabs (Ztrunc x))%Z.