(** IEEE-754 roundings: up, down and to zero *)

Global Instance valid_rnd_DN : Valid_rnd Zfloor.Global Instance valid_rnd_UP : Valid_rnd Zceil.Global Instance valid_rnd_ZR : Valid_rnd Ztrunc.Global Instance valid_rnd_AW : Valid_rnd Zaway.

Theorem exp_small_round_0 : forall rnd {Hr : Valid_rnd rnd} x ex, (bpow (ex - 1) <= Rabs x < bpow ex)%R -> round rnd x = 0%R -> (ex <= fexp ex)%Z .