Learn Scala 3 Fast: Constructs: The while Loop

Scala also has a while loop, but because Scala puts an emphasis on functional programming — and because the collections classes have dozens of built-in methods — I rarely use it. But if you need it, this is what it looks like:

var i = 0

while i < 3 do
    println(i)
    i += 1

If you prefer, you can add end while to the end of the loop:

while i < 3 do
    println(i)
    i += 1
end while

The while loop is generally used for a side-effect, such as printing to the console with println or updating a mutable variable, and when you write code in an FP style you avoid side effects as much as possible, so you don’t use while loops. Frankly, I have written maybe one while loop every year or two, so I don’t want to put too much emphasis on it here.

Exercises

The exercises for this lesson are available here.

More information

For more information about how FP avoids side effects, see my book, Functional Programming, Simplified.