Our goal here is implement conceptual lists in C++. It is not possible to add notation [2, 4, 6], since we cannot add new notation to C++. But we can add functions and a type.
The first issue is how to represent the information in a list. We use a linked representation, where a linked list contains one list cell for each of its members, and the cells are linked to one another by pointers. The last cell in the linked list holds a null pointer. Here is a linked list diagram of list [2, 4, 6].
Each cell has type ListCell, defined as follows.
struct ListCell
{
ListCell* tail;
int head;
ListCell(int h, ListCell* t)
{
head = h;
tail = t;
}
};
Since a list is always a pointer to a ListCell, it is convenient to make two additional type definitions.
typedef ListCell* List; typedef const ListCell* ConstList;