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Scala List FAQ: How do I merge Scala Lists?
There are at least three ways to merge/concatenate Scala List instances, as shown in the examples below.
1) The Scala List ::: method
First, you can merge two Scala lists using the ::: method of the List class, as demonstrated here at theScala command prompt:
scala> val a = List(1,2,3) a: List[Int] = List(1, 2, 3) scala> val b = List(4,5,6) b: List[Int] = List(4, 5, 6) scala> val c = a ::: b c: List[Int] = List(1, 2, 3, 4, 5, 6)
This operation is said to have O(n) speed, where n is the number of elements in the first List.
2) The Scala List concat method
You can also merge two Scala lists using the List class concat method:
scala> val a = List(1,2,3) a: List[Int] = List(1, 2, 3) scala> val b = List(4,5,6) b: List[Int] = List(4, 5, 6) scala> val c = List.concat(a, b) c: List[Int] = List(1, 2, 3, 4, 5, 6)
3) The Scala List ++ method
You can also use the List ++ method to concatenate Scala Lists, as shown here:
scala> val a = List(1,2,3) a: List[Int] = List(1, 2, 3) scala> val b = List(4,5,6) b: List[Int] = List(4, 5, 6) scala> val c = a ++ b c: List[Int] = List(1, 2, 3, 4, 5, 6)
I'll try to add more information on these three approaches as I learn about them, but for now, I just wanted to share these three approaches.
