Scaladocs explain how to add an element to a Vector.
def :+(elem: A): Vector[A]
[use case] A copy of this vector with an element appended.
Example:
scala> Vector(1,2) :+ 3
res12: scala.collection.immutable.Vector[Int] = Vector(1, 2, 3)
For a large collection, it seems expensive to copy the whole Vector, and then add an element to it.
What's the best(fastest) way to add an element to a Vector?
Concatenation to an immutable Vector is O(logN). Take a look at this paper to see how it is done.
If you're going to be doing a lot of appends you should use a Queue as it guarantees constant time append. For information on the time complexity of collections you can refer to this cheat sheet.
http://www.scala-lang.org/docu/files/collections-api/collections_40.html
Appending to a vector in Scala takes effectively constant time. The vector is copied in the sense that many of its data structures are reused, not in the sense that all of the elements are copied into a new vector. See the link provided by coltfred for more information about time complexity of collections:
http://www.scala-lang.org/docu/files/collections-api/collections_40.html
