rewrite [trunc_add_half_ulp_eq_of_no_uflow npos no_uflow]
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
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 + next n (trunc n x) ≤ 2 * x