Array append() and assignment operator (+=)

import Cocoa

var someInts = [Int]()
var someStrings=[String]()

someStrings.append("a")
someStrings.append("b")
someStrings.append("c")
someStrings += ["d"]

var someVa = someStrings[3]
println(someVa)

someInts.append(20)
someInts.append(30)
someInts += [40]

var someVar = someInts[0]

println( "Value of first element is \(someVar)" )
println( "Value of second element is \(someInts[1])" )
println( "Value of third element is \(someInts[2])" )