Mastering Functional Programming

Pattern matching

Special constructs in Scala are partial functions and pattern matching. For example, you can write expressions as follows:

scala> val str = "Foo"str: String = Fooscala> str match {     | case "Bar" => println("It is a bar")     | case "Foo" => println("It is a foo")     | }It is a foo

More complex pattern matching is also possible. For example, given a list, we can match on its head and tail, or its head and its second argument and its tail:

scala> val list = List(1, 2, 3, 4, 5)list: List[Int] = List(1, 2, 3, 4, 5)scala> list match {     | case e1 :: e2 :: rest => e1 + e2     | }<console>:13: warning: match may not be exhaustive.It would fail on the following inputs: List(_), Nil       list match {       ^res10: Int = 3

In fact, we can perform pattern matching ...