1::2::nil : List ℕ
1::2::3::4::5::nil : List ℕ
`[`:1024 (foldr 0 `,`) `]`:0 := #0
`-[1+`:1024 _:1 `]`:0 := int.neg_succ_of_nat #0
_ `^[`:1 _:1 `]`:0 := nat.iterate #1 #0
_ `≈[`:50 _:1 `]`:0 _:50 := @strict_weak_order.equiv _ #1 #2 #0