Project Euler #7 - 10001st prime
for var i = 5; i &lt;= maxPrime; i += 6 {
    if number % i == 0  || number % (i + 2) == 0 {
        return false
    }
}


We can implement some Swift syntax here:

for i in stride(from:5 through:maxPrime by: 6) {
    if number % i == 0 || number % (i + 2) == 0 {
        return false
    }
}


I don't know how this would compare in terms of performance however.  I suspect it's the same or better however.