Scala language feature: Lazyness

Overview of definition keywords

Lazy val

lazy val a: Int = {
    println("set!")
    3
}

By-name parameters

def test(value: => Int): Int = {
    if (value > 0) 0 else value * 2
}
test {
    println("test")
    scala.util.Random.nextInt
}

https://stackoverflow.com/questions/4543228/whats-the-difference-between-and-unit

Lazyness is like functions as values

Streams as infinite lists

Simple example of DSL

References

• How to Use By-Name Parameters in Scala
• Intro to Functional Streams for Scala (FS2)
• Functional programming in Scala Chapter 5
• Lazy Evaluation