What is an idiomatic Scala way to "remove" one element from an immutable List?
list, scala
Solution
I haven't seen this possibility in the answers above, so:
scala> def remove(num: Int, list: List[Int]) = list diff List(num)
remove: (num: Int,list: List[Int])List[Int]
scala> remove(2,List(1,2,3,4,5))
res2: List[Int] = List(1, 3, 4, 5)
Edit:
scala> remove(2,List(2,2,2))
res0: List[Int] = List(2, 2)
Like a charm :-).
Problem
I have a List, which may contain elements that will compare as equal. I would like a similar List, but with one element removed. So from (A, B, C, B, D) I would like to be able to "remove" just one B to get e.g. (A, C, B, D). The order of the elements in the result does not matter. I have working code, written in a Lisp-inspired way in Scala. Is there a more idiomatic way to do this? The context is a card game where two decks of standard cards are in play, so there may be duplicate cards but still played one at a time. ``` def removeOne(c: Card, left: List[Card], right: List[Card]): List[Card] = { if (Nil == right) { return left } if (c == right.head) { return left ::: right.tail } return removeOne(c, right.head :: left, right.tail) } def removeCard(c: Card, cards: List[Card]): List[Card] = { return removeOne(c, Nil, cards) } ```