have hb : assignments.size = assignments.size := rfl
α : Type u
assignments : Array Assignment
f : Array Assignment → α → Array Assignment
f_preserves_size : ∀ (arr : Array Assignment) (a : α), (f arr a).size = arr.size
l : List α
⊢ (List.foldl f assignments l).size = assignments.size
α : Type u
assignments : Array Assignment
f : Array Assignment → α → Array Assignment
f_preserves_size : ∀ (arr : Array Assignment) (a : α), (f arr a).size = arr.size
l : List α
hb : assignments.size = assignments.size
⊢ (List.foldl f assignments l).size = assignments.size