lazy var tallest: Person? = {
return people.max(by: { $0.height < $1.height })
}()

enum Direction {
case North
case East
case South
case West
}

typealias Weight = Float

let mass1: Weight = 150.0
let mass2: Weight = 220.0
let total: Weight = mass1 + mass2

var name: String? = «Charles»
if let realName = name {
print (realName)
}

Charles

var name: String?
if name != nil {
print(name)
} else {
print(«N/A»)
}

print(name ?? «N/A»)

class Weight {
var kilograms: Float = 0.0
var pounds: Float {
get { return (kilograms * 2.205)}set(newWeight) {
kilograms = newWeight /2.205
}}}
let weight = Weight()
weight.kilograms = 100print(weight.pounds) // prints '220.5'weight.pounds = 315print(weight.kilograms) // prints '142.85715'