An iterator to endlessly iterate over the same sequence.

CycleIterator.swift

struct CycleIterator<Element>: IteratorProtocol, ExpressibleByArrayLiteral {
    private var elements: [Element]
    private var offset: Int = 0

    init(_ elements: [Element]) {
        self.elements = elements
    }

    init(arrayLiteral elements: Element...) {
        self.init(elements)
    }

    mutating func next() -> Element? {
        let index = offset % elements.count
        offset += 1
        return elements[index]
    }
}