exact leaf x i (Nat.le_of_not_lt hl)
α : Type u
lt : α → α → Bool
x : Subarray α
i : Nat
lhs : Nat := 2 * i + 1
rhs : Nat := lhs + 1
hr : ¬rhs < Subarray.size x
hl : ¬lhs < Subarray.size x
⊢ heapifyDown.OpSpec lt x i x
no goals