gistfile1.txt

import Foundation
import QuartzCore

func benchmark(repeatCount: Int = 1, name: String = "closure", closure: () -> Void) {
    let d = CACurrentMediaTime()
    for _ in 0..<repeatCount {
        closure()
    }
    let d1 = CACurrentMediaTime()-d
    print("Benchmark of \(name) took \(d1) seconds")
}

class SuperClass {}
class A : SuperClass {}
class B : SuperClass {}

var a = [A]()
var b = [B]()

for i in 0..<10000000 {
    a.append(A())
    b.append(B())
}

benchmark {
    let f = a as [SuperClass]
    print(f.last!) // to prevent the compiler from optimising everything away
}

benchmark {
    let f = a.map{$0 as SuperClass}
    print(f.last!) // to prevent the compiler from optimising everything away
}