simp [smallest, hyp]
α : Type
inst✝ : LinearOrder α
l : List α
head : α
tail : List α
hyp : head :: tail ≠ []
⊢ ∀ a ∈ head :: tail, smallest (head :: tail) hyp ≤ a
α : Type
inst✝ : LinearOrder α
l : List α
head : α
tail : List α
hyp : head :: tail ≠ []
⊢ (if c : tail = [] then head else min head (smallest tail c)) ≤ head ∧
    ∀ a ∈ tail, (if c : tail = [] then head else min head (smallest tail c)) ≤ a