LinearSeq

Linear sequences have the notion of a head and a tail. The definition looks like trait LinearSeq[+A] extends Seq[A] with LinearSeqOps[A, LinearSeq, LinearSeq[A]] and the class diagram is shown here:

There are three representatives of LinearSeq, all are immutable:

• List defines three symbolic methods which provide a nice syntax for pattern-matching and building lists. :: prepends element to the list, ::: prepends all elements of a given list, and reverse_::: prepends all elements of a given list but in the reverse order.
• LazyList is a new immutable collection available since Scala 2.13. It implements a list with a head and a tail, which are not evaluated until needed. As it is superior to Stream, which is only lazy in the tail, Stream is now deprecated. LazyList has two additional methods, force which evaluates it, and lazyAppendAll which lazily appends a given collection to this list.
• Queue in this hierarchy is also immutable. It allows a first-in-first-out (FIFO) insertion and retrieval of the elements. For this functionality, it defines the enqueue, enqueueAll, dequeue, dequeueOption, and front methods.