How do primitives work in kotlin? ```public class Char private constructor() : Comparable<Char&g...

# getting-started

[ursus]

How do primitives work in kotlin?

public class Char private constructor() : Comparable<Char> {
    public fun toInt(): Int
    ...
}

First of all, what is this even, and why does it compile? a concrete class with no implementation of methods?
Secondly, does charArratOf('a', 'b', 'c') create 3 instances of Char class?
Or, is there some magic

[ephemient]

that builtin "implementation" is just a stub. on JVM the compiler emits java.lang.Character, char, char[], etc. as appropriate.

[ursus]

okay so charArrayOf(..) is then equal to the java char[] ?

[ephemient]

yes, primitiveArrayOf()/PrimitiveArray is exactly equivalent to Java's primitive[], and arrayOf<T>()/Array<T> is exactly equivalent to Java's T[]

[ursus]

thanks

Id like how ask how does the Char class compile like that? Is there some special case in the compiler?

[ephemient]

yes, builtins are hard-wired in the compiler

[ursus]

thank you

[CLOVIS]

It doesn't actually compile to anything, what you're looking at is more or less a “binding” that declares functions, similar to external interfaces, so the rest of your code can call these methods; but the real implementation is inside the compiler/runtime.