Which of these is likely to perform better? I assume the `List` version but you never know, figured ...

# getting-started

[Gavin Ray]

Which of these is likely to perform better?
I assume the List version but you never know, figured I'd ask others:

fun recur(...): Sequence<*> = sequence {
    yield(...)
    getQueryRelations(innerRequest).forEach {
        yieldAll(
            recur(...)
        )
    }
}

fun recur(...): List<*> {
    return listOf(...) + getQueryRelations(innerRequest).flatMap {
        recur(...)
    }
}

[ephemient]

possibly irrelevant, but if getQueryRelations(innerRequest) is a suspend fun then your sequence version can't be used directly. sequenceOf(...) + getQueryRelations(innerRequest).asSequence().flatMap { ... } could be used though

[ephemient]

I would tend to use

buildList {
    add(...)
    getQueryRelations(innerRequest).flatMapTo(this) { recur(...) }
}

or

getQueryRelations(innerRequest).flatMapTo(mutableListOf(...)) { recur(...) }

instead of your second option, to avoid one whole list copy

[ephemient]

but the performance is likely to vary on several factors

[Gavin Ray]

.flatMapTo(this) I had never thought of that, that's pretty clever!