case neg hn =>
  rw [if_neg hn]
  rfl
f : Bool → Bool → Bool
f_stable : f false false = false
m n : Nat
hm : ¬m = 0
hn : ¬n = 0
⊢ (if n = 0 then if f true false = true then m % 2 else 0
    else if f (decide (m % 2 = 1)) (decide (n % 2 = 1)) = true then 1 % 2 else 0) =
    if f (decide (m % 2 = 1)) (decide (n % 2 = 1)) = true then 1 else 0
no goals