cases hf with 
| nil => constructor
| cons hlt _ _ => 
  constructor <;> try assumption
  . apply Nat.lt_of_le_of_lt hle hlt
α : Sort ?u.12184
le : α → α → Bool
not_le_le : ∀ (x y : α), ¬le x y = true → le y x = true
n : ℕ
α✝ : Type u_1
xs : List (BinTree α✝)
m : ℕ
hf : IsHeapForest' n xs
hle : m ≤ n
⊢ IsHeapForest' m xs
no goals