α : Type ?u
a : α
as bs : List α
h : bs = a :: as
⊢ List.length (?head :: as) = List.length bs

case head
α : Type ?u
a : α
as bs : List α
h : bs = a :: as
⊢ α
α : Type ?u
b a : α
as bs : List α
h : as = bs
⊢ List.length as + 1 + 1 = List.length bs + 2
α : Type ?u
b a : α
as bs : List α
h : as = bs
⊢ List.length as + 1 + 1 = List.length (b :: bs) + 1
α : Type ?u
b a : α
as bs : List α
h : as = bs
⊢ List.length as + 1 + 1 = List.length bs + 1 + 1
α : Type ?u
b a : α
as bs : List α
h : as = bs
⊢ id (List.length (a :: b :: as)) = List.length (b :: bs) + 1
α : Type ?u
b a : α
as bs : List α
h : as = bs
⊢ List.length (a :: b :: as) = List.length (b :: bs) + 1
α : Type ?u
b a : α
as bs : List α
h : as = bs
⊢ List.length as + 1 + 1 = List.length bs + 1 + 1