CODEWITHSUNDEEP
scala
Ru Hasha
Ru Hasha

Reputation: 956

One-liner loop using only recursion in scala

I'm not sure where to ask this... (it doesn't quite fit the code-golf stackoverflow community)

I have this proof-of-concept javascript snippet that loops without for/while loops by using recursion:

(x=>x(x))(x=>{console.log('...'); x(x);})

Is there an equivalent one-liner scala snippet that would do the same? (again, using only recursion to achieve looping)?

Upvotes: 0

Views: 113

Answers (3)

Jörg W Mittag
Jörg W Mittag

Reputation: 369458

Using recursion for looping is the standard way of doing iteration in any functional language, Scala and ECMAScript or by no means special in this regard. And implementing this is a typical beginner's exercise. In Scala, it might look something like this:

@scala.annotation.tailrec
def whileLoop(condition: => Boolean)(body: => Unit): Unit = 
  if (condition) {
    body
    whileLoop(condition)(body) 
  }

var i = 10
var j = 100

whileLoop { i < j } {
  println(i)
  i += 1
  j -= 1
}

Now, you might say "But wait, that's not on one line!" But here's the thing: that's a meaningless requirement because all code can always be condensed into one line by removing line breaks:

@scala.annotation.tailrec def whileLoop(condition: => Boolean)(body: => Unit): Unit = if (condition) { body; whileLoop(condition)(body) }; var i = 10; var j = 100; whileLoop { i < j } { println(i); i += 1; j -= 1 }

Upvotes: 0

Luis Miguel Mej&#237;a Su&#225;rez
Luis Miguel Mej&#237;a Su&#225;rez

Reputation: 22850

Well, you can do this:

def loop(): Unit = { println("loop"); loop() }

Or this:

def loop[A](f: (A => A) = (loop[A] _)): A = { println("loop"); loop(f) }

But I do not see what is the value, it is just a dumb infinite function.

Upvotes: 5

Terry Dactyl
Terry Dactyl

Reputation: 1868

def f():Unit = { println("..."); f() }

Upvotes: 0

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