@auto_closure for control over evaluation

gistfile1.txt

func myAnd(lhs : Bool, rhs : @auto_closure () -> Bool) -> Bool {
    if lhs {
        return rhs()
    } else {
        return false
    }
}

func logAndBool(val : Bool) -> Bool {
    println("evaluating and returning \(val)!")
    return val
}

var res = myAnd(logAndBool(false), logAndBool(true))
// log reads "evaluating and returning false!", does not contain a log for true.