What's the nicest + efficient way to do a map of some collections into sets, and flatten into a unio...

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[Nir]

What's the nicest + efficient way to do a map of some collections into sets, and flatten into a union of those sets?
Right now I'm thinking:

val finalSet = whateverlist.fold(mutableSetOf()) { acc, element ->
    val individualSet = someCode(element)
    acc.apply { addAll(individualSet) }
}

I'd expect this to be a little faster than some of the other approaches (e.g. reduce with regular Set and union )

[randomcat]

I'd think someList.flatten().toSet() would work well enough

[randomcat]

you could throw in an asSequence() if you thought it was necessary

[Nir]

You're probably right

[Nir]

a very primitive benchmark confirms little difference, thanks for the suggestion

[randomcat]

np 🙂

[Nir]

for some reason I didn't think of that, when I was doing map I was followuping up with reduce + union instead of simply flatten and toSet