Birleştirme

data class Book(val title: String, val author: String, val isbn: String)
data class Member(val name: String, val id: String)

class Library {
    val books = mutableListOf<Book>()
    val members = mutableListOf<Member>()
    val borrowed = mutableMapOf<String, String>()
    fun addBook(book: Book) { books.add(book) }
    fun addMember(member: Member) { members.add(member) }
    fun checkout(memberId: String, isbn: String) {
        borrowed[isbn] = memberId
        println("Ödünç: $memberId -> $isbn")
    }
    fun returnBook(isbn: String) {
        borrowed.remove(isbn)
        println("İade: $isbn")
    }
    fun searchByAuthor(author: String): List<Book> = books.filter { it.author == author }
    fun availableBooks(): List<Book> = books.filter { it.isbn !in borrowed }
}

fun main() {
    val lib = Library()
    lib.addBook(Book("Suç ve Ceza", "Dostoyevski", "978-1"))
    lib.addMember(Member("Ayşe", "M1"))
    val command = "checkout"
    when (command) {
        "checkout" -> lib.checkout("M1", "978-1")
        "return" -> lib.returnBook("978-1")
        "list" -> lib.books.forEach { println(it) }
    }
}