have lohi : trunc n b ≤ next n (trunc n a) :=
  Nat.le_trans lolo (Nat.le_add_right _ _)
n a b : ℕ
round : ℕ → ℕ
npos : 0 < n
hfaithful₁ : faithful₁ n round
hcorrect₀ : correct₀ n round
hcorrect₁ : correct₁ n round
hba : b ≤ a
lolo : trunc n b ≤ trunc n a
⊢ round b ≤ round a
n a b : ℕ
round : ℕ → ℕ
npos : 0 < n
hfaithful₁ : faithful₁ n round
hcorrect₀ : correct₀ n round
hcorrect₁ : correct₁ n round
hba : b ≤ a
lolo : trunc n b ≤ trunc n a
lohi : trunc n b ≤ next n (trunc n a)
⊢ round b ≤ round a