Scala

object-functional

Lorenzo Gallegos, Keith Risper, Lars Walen

Big Picture

• development started in 2001
• at the École Polytechnique Fédérale de Lausae (Switzerland)
• by Martin Odersky
• "for general software applications, statically typed, designed to concisely express solutions in an elegant, type-safe and lightweight manner"

Hello World

 object HelloWorld extends App {
	println("Hello, World!")
 }
			

println("Hello, World!")
			

99 Bottles of Beer

(99 to 1 by -1).par foreach {n =>
  println("""|%d bottles of beer on the wall
				 |%d bottles of beer
				 |Take one down, pass it around
				 |%d bottles of beer on the wall\n""".stripMargin format (n, n, n -1))}
			

Object-Oriented Features

• Every value is an object
• Class methods and variables
• Subclassing

Classes

class Point(xc: Int, yc: Int) {
  var x: Int = xc
  var y: Int = yc
  def move(dx: Int, dy: Int) {
	 x = x + dx
	 y = y + dy
  }
  override def toString(): String = "(" + x + ", " + y + ")";
}
		

Possible successor to Java?

James Strachan, creator of Groovy, thinks so.

Functional Features

Just about everything we learned about in Haskell

For-expressions

• Different name for list comprehensions

val s = for (x <- 1 to 25 if x*x > 50) yield 2*x

Anonymous Functions

• Like lambdas in Haskell
• Use type inference

list map { x => sqrt(x) }

Lazy Evaluation

• Usually evaluates eagerly
• lazy keyword specifies lazy evaluation

Higher-Order Functions

list.filter(_ > 2).map(_ * 3).sum

Exception Handling

• Very similar to Java
• No checked exceptions

Likeable Things

• Immutable data structures
• Traits
• Imports