Loop up from or down to zero in an unsigned integer type

Using Swift
3

There is also a version of the stride function that includes the upper bound: stride(from:through:by:). It looks like this does what you want:

let range = up ? stride(from: 0, through: max, by: 1) : stride(from: max, through: 0, by: -1)

Test code:

func useStrideThrough(_ max: UInt, _ up: Bool, _ stop: UInt) {
    let range = up ? stride(from: 0, through: max, by: 1) : stride(from: max, through: 0, by: -1)
    var result = ""
    for index in range {
        result += "\(index)"
        if index == stop { break }
    }
    print("\(#function)(\(max), \(up), \(stop)) = \(result)")
}

useStrideThrough(5, true , 6) // 012345
useStrideThrough(5, false, 6) // 543210
useStrideThrough(5, true , 3) // 0123
useStrideThrough(5, false, 3) // 543
4 Likes