Making use of WhereTo and ThisIsA

Listing 4:

LinkedList.01

1#include <iostream>
2#include "whereis03.cc"
3
4using namespace std;
5
6template <class T> class List
7{
8    class Node
9    {
10        T payload;
11        WhereIs<Node> next;
12      public:
13        void setNext(WhereIs<Node> &next)
14        {
15          next.detach();
16          next.becomesAliasOf(next);
17        }
18        WhereIs<Node> getNext(void) const { return next; }
19        Node(const T &v):payload(v)
20        {
21        }
22        Node(const Node &n):payload(n.payload),next(n.next)
23        {
24        }
25    };
26    WhereIs<Node> first;
27  public:
28    void insert(const T &v)
29    {
30      Node n(v);
31      WhereIs<Node> oldFirst;
32      oldFirst.becomesAliasOf(first);
33      first.detach();
34      first.allocate(n);
35      (*first).setNext(oldFirst);
36    }
37    unsigned count(void) const
38    {
39      WhereIs<Node> tmp;
40      tmp.becomesAliasOf(first);
41      while (!tmp.isNull())
42      {
43        tmp.detach();
44        tmp.becomesAliasOf((*tmp).getNext());
45      }
46    }
47};
48
49int main(void)
50{
51  List<int> l;
52
53  l.insert(12);
54  l.insert(23);
55  cout << l.count();
56  return 0;
57}

4.4 Making use of WhereTo and ThisIsA