proposition: Lemma round_round_minus_radix_ge_3 : (3 <= beta)%Z -> forall (fexp1 fexp2 : Z -> Z), Valid_exp fexp1 -> Valid_exp fexp2 -> forall (choice1 choice2 : Z -> bool), round_round_plus_radix_ge_3_hyp fexp1 fexp2 -> forall x y, generic_format beta fexp1 x -> generic_format beta fexp1 y -> round_round_eq fexp1 fexp2 choice1 choice2 (x - y).
proof: Proof. intros Hbeta fexp1 fexp2 Vfexp1 Vfexp2 choice1 choice2 Hexp x y Fx Fy. unfold Rminus. apply generic_format_opp in Fy. now apply round_round_plus_radix_ge_3. Qed.
imports: Coq(ZArith Reals Psatz) Core FTZ