Questions regarding Reflections: I was playing ar...

# getting-started

[JP]

Questions regarding Reflections:

I was playing around with reflections, reading the documentation.
Q1.

import kotlin.reflect.KFunction1

fun isOdd(x: Int) = x % 2 == 1
fun isOdd(s: String) = s == "brillig" || s == "slithy" || s == "tove"

fun main() {
    val numbers = listOf(1, 2, 3)
    println(numbers::class.qualifiedName)
    println(numbers.filter(::isOdd)) // refers to isOdd(x: Int) among the overloaded functions, from the context

    val strings = listOf("Hello", "brillig", "World", "tove")
    println(strings.filter(::isOdd)) // refers to isOdd(x: String)


    val n = IntRange(1, 10).toList()
    println(n::class.qualifiedName)

    val predicate: KFunction1<Int, Boolean> = ::isOdd
    // val predicate: (Int) -> Boolean = ::isOdd // then below codes would not work
    println(predicate)
    println(predicate.returnType)
    println(predicate.parameters)
    println(predicate.parameters[0].type)
    println(predicate.parameters[0].also { println(it.kind) }.name)
}

Is it correct to say that ::isOdd actually returns the value of type KFunction1<Int, Boolean> which is a subtype of the function type (Int) -> Boolean?

Q2. While I was searching in the api documentation, I found out that KFunction1, doesn’t have a page for it. Is there a reason? And in the page for KFunction

interface KFunction<out R> : KCallable<R>, Function<R>

Why does KFunction NOT have the input parameter types in the definition, and only have the output type?

Q3. What is the difference between KFunction and KCallable? I’m not so sure what a callable means in Kotlin. Is it correct to say a “callable” = “function or property”, a superset of function? (P.S. are constructors also function? Or is it a callable, but different from a function?)