I'm new to scala and just playing around with it in my free time and ran into this problem:
if I have this list:
val list = List(1,2,3,4)
and then say:
val newList = list :: 5
scala tells me
error: value :: is not a member of Int
but if I say:
val newList = list ::: List(5)
scala is completely alright with it. Why can I not append an element to a List, but I can append all elements of a List to the end of a List
You've got the syntax backwards:
5 :: list
This will prepend the element 5 to the front of list.
In Scala, operators that end with a colon (:) are right-associative. So 5 :: list calls the :: method on list and gives the argument 5.
The reason list ::: List(5) works is that it's actually prepending list to the front of List(5).
By the way, List also has the operators +: and :+ for prepend and append, respectively. (But keep in mind that prepending to a List is O(1) while appending is O(n).)
