refine Nat.le_of_mul_le_mul_left ?_ two_pos
case inr
n x : ℕ
round : ℕ → ℕ
npos : 0 < n
hcorrect₁ : correct₁ n round
hhi : round x = next n (trunc n x)
no_uflow : x ≥ 2 ^ n
⊢ trunc n x + ulp n x / 2 ≤ x
case inr
n x : ℕ
round : ℕ → ℕ
npos : 0 < n
hcorrect₁ : correct₁ n round
hhi : round x = next n (trunc n x)
no_uflow : x ≥ 2 ^ n
⊢ 2 * (trunc n x + ulp n x / 2) ≤ 2 * x