/**
 * Beispiel aus
 *
 * - Algorithmen und Datenstrukturen für Dummies
 *   - von Andreas Gogol-Döring und Thomas Letschert
 *   - Verlag Wiley-VCH; Oktober 2019
 *  - Kapitel 4, Listen: Immer einer nach dem anderen
 *
 * @author A. Gogol-Döring, Th. Letschert
 */

import Foundation

struct AuD_04_05_List_Iterator {

    enum IntList : Sequence {
        case Nil
        indirect case Cons(first: Int, rest: IntList)

        func makeIterator() -> IntLstIterator {
            IntLstIterator(lst: self)
        }
    }

    struct IntLstIterator : IteratorProtocol {
        var lst: IntList
        init(lst: IntList) {
            self.lst = lst
        }
        mutating func next() -> Int? {
            switch lst {
            case .Nil: return nil
            case .Cons(let first, let rest):
                lst = rest
                return first
            }
        }
    }

    static func run() {
        let l: IntList =
                .Cons(first: 1,
                        rest: .Cons(first: 2,
                                rest: .Cons(first: 3,
                                        rest: .Cons(first: 4,
                                                rest: .Cons(first: 5,
                                                        rest: .Cons(first: 6,
                                                                rest: .Cons(first: 7,
                                                                        rest: .Nil)))))))

        for x in l {
            print(x)
        }
    }

}