# `chain_one` Annoyed that you `[T; N]` doesn't implement `IntoIterator`? Annoyed that `Chain` doesn't implement `ExactSizeIterator`? Do I have a project for you! ```rust assert_eq!(iter![1, 2, 3, 4, 5].collect::>(), vec![1, 2, 3, 4, 5]); assert_eq!(iter![1, 2, 3, 4, 5].rev().collect::>(), vec![5, 4, 3, 2, 1]); assert_eq!((0..5).chain_one(0).collect::>(), vec![0, 1, 2, 3, 4, 0]); ```