Say I have `fun myCheck Boolean` which I want to repeatedly kotlinlang #getting-started

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Mark

01/30/2020, 10:39 AM

Say I have

fun myCheck(): Boolean

which I want to repeatedly call until it returns false. If I use

while (myCheck()) {}

then I get a warning saying “control flow with empty body”. So I guess

while

is supposed to be used with a non-empty body. Does this mean there is a more appropriate way?

Francisco Javier Ruiz Rodriguez

01/30/2020, 10:57 AM

Yep, It seems you want to run some code while your condition is true, so put your code inside the

while

Mark

01/30/2020, 10:58 AM

But there is no code to run while the condition is true. The check does all that is needed.

Francisco Javier Ruiz Rodriguez

01/30/2020, 11:00 AM

So you can try this:

do {
        val bool = myCheck()
    }while(bool)

elizarov

01/30/2020, 11:04 AM

Write a comment inside that it is intentionally empty.

👍 7

Mark

01/30/2020, 11:25 AM

var index = start
while (myCheck(index++)) { /* nothing to do */ }

Very much a style question, but I just wonder if there is a neater way - probably a for loop so that

index

is encapsulated, but then the code is maybe too verbose.

arve

01/30/2020, 11:29 AM

var index = start
while (myCheck(index++)) { continue; }

Mark

01/30/2020, 11:34 AM

The equivalent of in Java;

for (int index = start; myCheck(index); index++) { /*do nothing */ }

kyleg

01/30/2020, 3:52 PM

There’s also

generateSequence(start){ it+1 }.takeWhile(::myCheck).count()

if you want to be kooky. :)

James Richardson

01/31/2020, 8:03 AM

Spinning on a check like this is not very good for battery life or energy consumption. The check could be executed millions of times a second. Have you considered some other synchronisation method. E.g. condition variable, countdown latch....

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