In Scala how do I remove duplicates from a list?

Question

Suppose I have

val dirty = List("a", "b", "a", "c") 

Is there a list operation that returns "a", "b", "c"

Answer 1

Have a look at the ScalaDoc for Seq,

scala> dirty.distinct res0: List[java.lang.String] = List(a, b, c) 

Update. Others have suggested using Set rather than List. That's fine, but be aware that by default, the Set interface doesn't preserve element order. You may want to use a Set implementation that explicitly does preserve order, such as collection.mutable.LinkedHashSet.

Answer 2

scala.collection.immutable.List now has a .distinct method.

So calling dirty.distinct is now possible without converting to a Set or Seq.