Working example of the running example on p. 15 of Chang et al, "Shape Analysis," in Trends and Foundations of Programming Languages vol 6, no 1-2, pp. 1-158.

List_insertion.cpp

#include <iostream>

using namespace std;

typedef struct list {
    struct list * n;
    int d;
} list;

void insert(list * l, int d) {
    list * t = l;
    while (t != NULL) {
        if (t->d == d) {
            list * fresh = (list *) malloc(sizeof(list));
            fresh->n = t->n;
            fresh->d = d;
            t->n = fresh;
            break;
        } else {
            t = t->n;
        }
    }
}

void print_list(list l) {
    cout << "[";
    cout << l.d;
    while (l.n != NULL) {
        l = *l.n;
        cout << ", " << l.d;
    }
    cout << "]" << "\n";
}

int main()
{
    cout << "Running program..." << "\n\n";
 
    list l1;
    l1.n = 0;
    l1.d = 3;
 
    cout << "List 1:" << "\n";
    print_list(l1);
    cout << "\n";
    
    cout << "List 2:" << "\n";
    list l2;
    l2.n = &l1;
    l2.d = 4;
    
    print_list(l2);
    cout << "\n";
    
    cout << "Inserting an extra 3:" << "\n";
    insert(&l2, 3);
    
    print_list(l2);
    cout << "\n";
    
    return 0;
}