Sequences And Arrays

Scala provides a data structure, the array, which stores a fixed-size sequential collection of elements of the same type. An array is used to store a collection of data, but it is often more useful to think of an array as a collection of variables of the same type.

A list can be converted to an array:

val l = List(1, 2, 3)
val a = l.toArray
a should equal(Array(res0, res1, res2))

Sequences are special cases of iterable collections of class Iterable. Unlike iterables, sequences always have a defined order of elements.

Any sequence can be converted to a list:

val a = Array(1, 2, 3)
val s = a.toSeq
val l = s.toList
l should equal(res0)

You can create a sequence from a for loop:

val s = for (v ← 1 to 4) yield v
s.toList should be(res0)

You can create a sequence from a for loop with a filter:

val s = for (v ← 1 to 10 if v % 3 == 0) yield v
s.toList should be(res0)

You can filter any sequence based on a predicate:

val s = Seq("hello", "to", "you")
val filtered = s.filter(_.length > 2)
filtered should be(Seq(res0, res1))

You can also filter Arrays in the same way:

val a = Array("hello", "to", "you", "again")
val filtered = a.filter(_.length > 3)
filtered should be(Array(res0, res1))

You can map values in a sequence through a function:

val s = Seq("hello", "world")
val r = s map {
  _.reverse
}

r should be(res0)