Difference between a Seq and a List in Scala

Question

I\'ve seen in many examples that sometimes a Seq is being used, while other times is the List...

Is there any difference, other than the former one being a Scala typ

Answer 1

Seq is a trait that List implements.

If you define your container as Seq, you can use any container that implements Seq trait.

scala> def sumUp(s: Seq[Int]): Int = { s.sum }
sumUp: (s: Seq[Int])Int

scala> sumUp(List(1,2,3))
res41: Int = 6

scala> sumUp(Vector(1,2,3))
res42: Int = 6

scala> sumUp(Seq(1,2,3))
res44: Int = 6

Note that

scala> val a = Seq(1,2,3)
a: Seq[Int] = List(1, 2, 3)

Is just a short hand for:

scala> val a: Seq[Int] = List(1,2,3)
a: Seq[Int] = List(1, 2, 3)

if the container type is not specified, the underlying data structure defaults to List.