코틀린스럽다 - 조태영

[taiyoung12]

// User
data class User(val name: String, val age: Int)

// UserManagementSystem
class UserManagementSystem {
    val users = mutableListOf<User>()

    fun addUser(name: String, age: Int) {
        users.add(User(name, age))
    }

    fun List<User>.filterAdults() = filter { it.age >= 18 }

    fun processUsers(action: (List<User>) -> Unit) {
        action(users)
    }

    fun getAdultUsers() = users.filterAdults()

    fun printUserNames() = processUsers { userList ->
        userList.forEach { println(it.name) }
    }

    fun calculateAverageAge() = users.map { it.age }.average()
}