list.cpp

#include <iostream>

class ListEntry {
    int m_v;
    ListEntry *m_next;
public:
    ListEntry (int v, ListEntry *next = nullptr) : m_v(v), m_next(next) {}
    ListEntry *getNext() {return m_next;}
    void setNext(ListEntry *next) {m_next = next;}

    int getValue() {return m_v;}
};

class List {
    ListEntry *m_head;
public:
    List() : m_head(nullptr) {
        std::cerr << "List is created\n";
    };
    ~List() {
        std::cerr << "List is deleted\n";
        ListEntry *p = m_head;
        while (p) {
            ListEntry *n = p->getNext();
            delete p;
            p = n;
        }
    }

    void insert(int v) {
        ListEntry *entry = new ListEntry(v, m_head);
        m_head = entry;
    }

    typedef std::pair<bool,int> int_bool_pair;
    int_bool_pair remove_at_index(unsigned idx) {
        ListEntry *prev = nullptr;
        ListEntry *curr = m_head;

        unsigned i = 0;
        while (i < idx && curr) {
            prev = curr;
            curr = curr->getNext();
            i = i + 1;
        }

        if (!curr) {
            std::cerr << "remove_at_index: index beyond list size\n";
            return std::make_pair(false, 0);
        }

        prev->setNext(curr->getNext());

        int v = curr->getValue();
        delete curr;

        return std::make_pair(true, v);
    }
    bool is_empty() {return m_head;}


    ListEntry *get_head() {return m_head;}

    void print(std::ostream &out) {
        if (m_head) print_rec(out, *m_head);
    }
    void print_rec(std::ostream &out, ListEntry &entry) {

        out << entry.getValue();
        if (entry.getNext()) {
            out << ", ";
            print_rec(out, *(entry.getNext()));
        }
    }
};

std::ostream &operator<<(std::ostream &out, List &v) {
    v.print(out);
    return out;
}

int main(void) {
    std::cout << "Hello world!\n";

    int r;
    std::unique_ptr<List> l(new List());
    l->insert(5);
    l->insert(4);
    l->insert(3);

    // l->print(std::cerr);
    // std::cerr << "\n";
    std::cerr << *l << "\n";

    for (unsigned i = 0; i < 3; i++) {
        auto res = l->remove_at_index(1);
        if (res.first) { std::cerr << "Removed element: " << res.second << "\n"; }
        else {std::cerr << "Index too large: idx=" << i << "\n";}
    }

    return 0;
}