https://hjaem.info/articles/kr_5_2

아래 세 표현식은 동등하다.

• 0 :: Nil
• ::(0, Nil)
• Nil.::(0)
• List(0)

https://www.oreilly.com/library/view/scala-reactive-programming/9781787288645/2a3ae044-05a5-4eb6-82ad-ac578ef5f026.xhtml

We cannot use the Cons operator to add a new element at the end of the List. It accepts it only to add it at the beginning of the List