rw [this, Nat.zero_add]
f : Bool → Bool → Bool
m n : Nat
hm : ¬m = 0
hn : ¬n = 0
this : 1 / 2 = 0
⊢ (if f (decide (m % 2 = 1)) (decide (n % 2 = 1)) = true then 1 / 2 + bitwise f (m / 2) (n / 2)
    else bitwise f (m / 2) (n / 2)) =
    bitwise f (m / 2) (n / 2)
f : Bool → Bool → Bool
m n : Nat
hm : ¬m = 0
hn : ¬n = 0
this : 1 / 2 = 0
⊢ (if f (decide (m % 2 = 1)) (decide (n % 2 = 1)) = true then bitwise f (m / 2) (n / 2)
    else bitwise f (m / 2) (n / 2)) =
    bitwise f (m / 2) (n / 2)