Yes indeed. Swift lacks the "yield return" statement of C#. Yet you can do well with "SequenceOf" and "GeneratorOf".

// Fibonacci sequence

let fib = SequenceOf { () -> GeneratorOf<Int> in

    var a = 0, b = 1

    return GeneratorOf {
        () -> Int? in
        let c = a + b
        a = b
        b = c
        return a
    }

}

// Print Fibonacci numbers <= 1000

for e in fib {

    if e > 1000 {
        break
    }

    print(" \(e)")

}

println()

$ xcrun swift fib_test.swift

1 1 2 3 5 8 13 21 34 55 89 144 233 377 610 987

See http://www.oki-osk.jp/esc/swift/linq.html