// Arrays
var dogNames = ["Miki", "Miki1", "Miki2"]
dogNames.first    // Miki
dogNames.last     // Miki2
dogNames.count    // 3
dogNames[1]     // Miki1
dogNames.append("Miki3")    // "Miki", "Miki1", "Miki2", "Miki3"
dogNames.insert("Miki4", at: 3)    // "Miki", "Miki1", "Miki2", "Miki4", "Miki3"
dogNames.removeAll() // empty

var emptyDoubles: [Double] = []    // create an empty array by specifying the Element type

reference: https://developer.apple.com/documentation/swift/array