calc b - w - a - ulp n (b - w - 1)
  _ ≤ b - w - a - 1 := tsub_le_tsub_left (Nat.one_le_of_lt $ ulp_pos n _) _
  _ ≤ b - w - 1     := tsub_le_tsub_right tsub_le_self _
case succ.inl.h₂.h
n a b : ℕ
npos : 0 < n
hfb : trunc n b = b
hf : trunc n (b - a) = b - a
w : ℕ
h : 2 * a < b - Nat.succ w
ih : trunc n (trunc n (b - w) - a) = trunc n (b - w) - a
hfb₁ : trunc n (b - w) = b - w
bpos : 0 < b - w
⊢ b - w - a - ulp n (b - w - 1) ≤ b - w - 1
no goals