Overview

I went to Wisconsin to visit family a couple weeks ago, and I came home with a bad cold that went down into my chest.  Because of that, and because Chapter 3 of Functional Programming in Scala is packed with lots of exercises, it has taken me awhile to get through.  In this chapter the authors discuss Functional Data Structures and also introduce Pattern Matching.

Functional Data Structure

A functional data structure is only operated on by pure functions.  They are, by definition, immutable.  The authors go on to point out, that although this may seem like a lot of wasted copying, in fact it is not – because of data sharing.  Data sharing is the idea of reusing data (since it is immutable we know it won’t change!) instead of copying it.

Pattern Matching

Pattern matching is a lot of fun, and can make for very concise and clean code.  It can be used to pull out sub-expressions of a structure. Here is a very simple example of pattern matching which pulls out the second element in a list.

  test("Example Pattern Matching") {
    val x = List(1, 2, 3, 4) match {
      case _ :: x :: _ => x
    }

    assert(x == 2)
  }

Conclusion

All of my solutions to the exercises from Chapter 3 can be found on GitHub.