Advanced

fun main() {
    a = [1]
    t = {a: "value"}
    print(t)
    print(t[[1]])
    a.add(2)
    print(t)
    print(t.entries[0]["key"])
    print(t[t.entries[0]["key"]])
    print(t[[1, 2]])
}

fun main() {
    val a = mutableListOf("a")
    val m = mutableMapOf(a to "b")
    println(m[mutableListOf("a")]) // b
    a.add("b")
    println(m) // {[a, b]=b}
    println(m[mutableListOf("a", "b")]) // null
}

# frozenset
# tuple