isLowerCase

expect fun Char.isLowerCase(): Boolean(source)

fun main() {
    val char1: Char = 'a'
    val char2: Char = 'Z'
    println("$char1 is lower case: ${char1.isLowerCase()}") // true
    println("$char2 is lower case: ${char2.isLowerCase()}") // false
}