What would be the kotlin way to write below code: ...

# getting-started

[Sourabh Rawat]

What would be the kotlin way to write below code:

var toPlayer = players.random()
                while (toPlayer == fromPlayer) {
                    toPlayer = players.random()
}

I am not liking the multiple assignments + var here...

[Sebastian Galkin]

How about something like

val toPlayers = generateSequence {players.random()}.filter {it != fromPlayer}

[Sebastian Galkin]

that gives you an infinite stream of players that are not fromPlayer

[Sourabh Rawat]

interesting. just what I needed. Thank you!

[nanodeath]

make sure there are at least two players 😅

[nanodeath]

I guess that's a requirement regardless

[Ruckus]

(players - fromPlayer).random()

[Sebastian Galkin]

nice!

[nanodeath]

it does duplicate the array, but also who cares 🙂

[Ruckus]

You could also define a helper function like so:

fun <T> List<T>.randomBut(exclude: T): T {
    var value: T
    do value = random() while (value == exclude)
    return value
}

Then just do

players.randomBut(fromPlayer)

[Ruckus]

Or more general:

inline fun <T> List<T>.randomWhere(predicate: (T) -> Boolean): T {
    var value: T
    do value = random() while (!predicate(value))
    return value
}

And

players.randomWhere { it != fromPlayer }

[Sourabh Rawat]

yes. thats doable. But I didnt want to write the do while + var combo, even in a helper, myself.

[Ruckus]

Fair enough, and not worth it for a single use, but with keeping in mind if you find yourself doing it a lot.

[nanodeath]

I've never seen a one-liner do-while loop before...huh

[Sourabh Rawat]

Me too. I thought this do while + assignment was only possible in Java.

[bjonnh]

See

doWhileStatement
(used by loopStatement)
  : 'do' controlStructureBody? 'while' '(' expression ')'
  ;

in https://kotlinlang.org/docs/reference/grammar.html#whileStatement

[bjonnh]

you can even write: "do while (value == exclude)"

[bjonnh]

and it is valid grammar…

[Michael de Kaste]

anything with random that can't mutually exclude itself from the edge case where it needs to check again is bad in my opinion.

in that case I feel that the following code from Ruckus is the best

(players - fromPlayer).random()

Yes you could technically use some sort of smart indexer where you exclude the result, but that would include searching for that element in the first place so the complexity would be the same.