Scala change for loop mutable aggregation to immutable

Question

If I have this simple loop which is imperative style

val num = 100
var result = 0.0
for (i <- 0 until num) {
    result += 4.0 * (1 - (i % 2) * 2) / (2 * i + 1)
}

How would I change it to immutable and functional?

Have you tried to solve this yourself before asking here? Paste a code snippet of your attempts before asking for the answer. I'll give you a hint, you're looking for a fold — cdk
– cdk, Commented Jun 17, 2014 at 14:20

vptheron · Accepted Answer · 2014-06-17 14:21:44Z

8

You have an initial value, you iterate over a collection of values and apply an operation to each item to eventually return one single value.

This looks a lot like something that could be turned into a fold.

answered Jun 17, 2014 at 14:21

vptheron

7,4761 gold badge29 silver badges35 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

KChaloux Over a year ago

Might be worth providing the code that does the folding, in case he's never seen a fold before: (0 until num).foldLeft(0.0) { (result, i) => result + 4.0 * (1 - (i % 2) * 2) / (2 * i + 1) }.

elm · Accepted Answer · 2014-06-17 15:52:36Z

0

Another approach, with a parallel collection,

(1 to 100).par.map { i => 4.0 * (1 - (i % 2) * 2) / (2 * i + 1) }.sum

answered Jun 17, 2014 at 15:52

elm

20.5k15 gold badges72 silver badges116 bronze badges

Collectives™ on Stack Overflow

Scala change for loop mutable aggregation to immutable

2 Answers 2

1 Comment

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

1 Comment

Comments

Your Answer

Sign up or log in

Post as a guest

Related