is there some stdlib function to retrieve all the ...

# getting-started

[elect]

is there some stdlib function to retrieve all the indices which satisfy a custom predicate?

[Joffrey]

Not directly (to my knowledge), but you could use mapIndexedNotNull like this:

val indicesOfMatches = items.mapIndexedNotNull { i, elt -> i.takeIf { predicate(elt) }}

[elect]

pity, no mapIndexedNotNull on FloatArray ..

[Klitos Kyriacou]

You can do myPrimitiveArray.asList().mapIndexedNotNull. This avoids creating a whole List but has the overhead of boxing each element as it iterates through the array.