Case Classes in Scala Intro UMBC CMSC 331

Basic Properties Case classes are regular classes which export their constructor parameters and which provide a recursive decomposition mechanism via pattern matching.

Example abstract class Term case class Var(name: String) extends Term case class Fun(arg: String, body: Term) extends Term case class App(f: Term, v: Term) extends Term

Code Code Example Fun("x", Fun("y", App(Var("x"), Var("y")))) For every case class the Scala compiler generates equals method which implements structural equality and atoString method. For instance and so ... Fun("x", Fun("y", App(Var("x"), Var("y"))))

Results val x1 = Var("x") val x2 = Var("x") val y1 = Var("y") println("" + x1 + " == " + x2 + " => " + (x1 == x2)) println("" + x1 + " == " + y1 + " => " + (x1 == y1)) Var(“x”) == Var(“x”) =>true Var(“x”) == Var(“y”) => false

Another Example abstract class IntTree case class Empty() extends IntTree case class Node(value: Int, left: IntTree, right:IntTree) extends IntTree

References A tour of Scala : Traits (see http://www.scala-lang.org) Programming in Scala, Martin Odersky et al, Artima press 2009 Beginning Scala, David Pollak, Apress, 2009