Collections & Closures

var fruits = ["apple", "banana", "cherry"]
fruits.append("date")
fruits[0]                       // "apple"
fruits.count                    // 4
fruits.contains("banana")       // true

var ages = ["Ada": 17, "Alan": 16]
ages["Grace"] = 17              // insert
let adaAge = ages["Ada"]        // Int? — key might be missing!

let unique: Set = [1, 2, 2, 3]  // {1, 2, 3}

// let makes collections deeply immutable:
let locked = [1, 2, 3]
// locked.append(4)             // error

let students = [
    (name: "Ada", grade: 95),
    (name: "Alan", grade: 88),
    (name: "Grace", grade: 92),
]

// Closures, from verbose to idiomatic:
let names1 = students.map({ (s: (name: String, grade: Int)) -> String in
    return s.name
})
let names2 = students.map { $0.name }    // same thing

let honorRoll = students
    .filter { $0.grade >= 90 }
    .map { $0.name }
    .sorted()                             // ["Ada", "Grace"]

let total = students.reduce(0) { $0 + $1.grade }
let best = students.max { $0.grade < $1.grade }

// sorted with a custom order:
let byGrade = students.sorted { $0.grade > $1.grade }