// create an empty Int array
var arr = [Int]()
// extend the array using a Range    
arr += 1...100

var arr30 = Array(1...30)

// even array
var arr40 = Array(1...40)
print(arr40[arr40.partition{$0 % 2 == 0}...])

print(Array(stride(from: 0, to: 40, by: 2)))

// partition based on the use of odd or even numbers
let idx = partition(&arr, indices(arr)) { i, _ in i%2==0 }
// use the returned point of partition (index) to split the array into odd and even
arr[0..<idx] // even
arr[idx..<arr.endIndex] // odd