Find family

Say you have an unordered list of objects:

data class Person(val firstName: String, 
                  val lastName: String,
                  val age: Int)
val people = listOf(Person("Jane", "Doe", 19),
            Person("John", "Doe", 24),
            Person("John", "Smith", 23))

And would like to find a first object that matches some criteria. Using extension functions, you could write something like this:

fun <T> List<T>.find(check: (T) -> Boolean): T? {
    for (p in this) {
        if (check(p)) {
            return p
        }
    }
    return null
}

And then, when you have a list of objects, you can simply call find() on it:

println(people.find {
    it.firstName == "John"
}) // Person(firstName=John, lastName=Doe)

Luckily, you don't have to implement anything. This method is already...