Kotlin Code Example for Extension Functions

/**
 * Checks if a given number is prime or not.
 */
fun main() {
    println("Please enter a number:")
    val input = readlnOrNull()?.toIntOrNull()
    if (input != null) {
        if (input.isPrime()) println("$input is a prime number")
        else println("$input is not a prime number")
    } else {
        println("Invalid input. Please enter a valid number.")
    }
}

/**
 * Checks if a given number is prime or not.
 * @return true if the number is prime, false otherwise.
 */

fun Int.isPrime(): Boolean {
    if (this <= 1) return false
    for (i in 2..<(this - 1)) {
        if (this % i == 0) return false
    }
    return true
}