Kotlin collections: Why doesn't the function call in .map work?

Question

Kotlin

How to pass a static class method(Basically doesn't matter, any method) tocollection.map()

Code example

class Utils {
  companion object {
    	fun squareOf(x:Int) = x * x
    }
}

fun main(args: Array<String>) {
    val a = listOf(1, 2, 3, 5, 10)
    val b = a.map(Utils.squareOf)
    
    for(x in a) print("$x ")
    println("");
    for(x in b) print("$x ")
    println("");
}

Строка val b = a.map(Utils.squareOf) не работает. Я могу сделать так: val b = a.map { Utils.squareOf(it) }, но должно работать и в первом случае.

Answer 1

First, not "does not work", but "does not compile". Secondly, you wrote a syntactically incorrect construction. This is not a function call, you cannot write it in this place. You can only lambda or function reference.
You can write it like this: .map(Utils.Companion::squareOf)
Thirdly, you don't need to drag a bad Java model into Kotlin, where "everything is a class". This Utils class is of no use. You just need to write a function
fun squareOf(x:Int) = x * x //in the Utils.kt file
and then use a reference to it:
.map(::squareOf)