PragPub 2012-03: Issue #33 by The Pragmatic Bookshelf

Author:The Pragmatic Bookshelf
Language: eng
Format: epub, mobi
Tags: PragPub—Monthly Magazine
Publisher: The Pragmatic Bookshelf, LLC
Published: 2012-03-01T05:00:00+00:00

Scala for the Intrigued

Pattern Matching

by Venkat Subramaniam

In this seventh installment of his series on Scala, Venkat shows how Scala does pattern matching.

You’ve seen quite a few examples of Scala’s expressive and concise nature in this series. Pattern matching is another area where you’ll appreciate the elegance of Scala. When programming you constantly make decisions based on the types of data and their values. Scala provides simple yet powerful facilities to program this common operation, as you’ll see in this article.

To explore the expressive power of pattern matching, let’s write a function that will count the number of nickels, dimes, and quarters in a given collection:

val coins = List(25, 10, 5, 10, 5, 25, 10, 5, 5, 25)

Using the traditional if-else construct, the code would look like this:

def countCoins(coins : Seq[Int], nickels : Int = 0,

dimes : Int = 0, quarters : Int = 0) : Map[String, Int] = {

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