cppListFwOperatorPlus_operatorMult_clone

#include <iostream>

template <typename ElemT>
class ListFw
{
    class Node
    {
        ElemT data;
        Node* next;
    public:
        Node(const ElemT& dataP, Node* nextP = nullptr) : data{ dataP }, next{ nextP }{}
        friend ListFw;
        template <typename ElemT>
        friend std::ostream& operator<<(std::ostream& out, const ListFw<ElemT>& list);
        template <typename ElemT>
        friend ListFw<ElemT> operator+(const ListFw<ElemT>& lhs, const ListFw<ElemT>& rhs);
        template <typename ElemT>
        friend ListFw<ElemT> operator*(const ListFw<ElemT>& lhs, const ListFw<ElemT>& rhs);
    };

    Node* head;
    Node* tail;
    size_t size;
    Node* getNode(size_t idx);
public:
    ListFw() : head{ nullptr }, tail{ nullptr }, size{ 0 } {}
    ListFw(const ListFw& listP) : head{ nullptr }, tail{ nullptr }, size{ 0 }
    {
        for (auto curr{ listP.head }; curr; curr = curr->next)
        {
            push_back(curr->data);
        }
        std::cout << "Copy-shmopy!\n";
    };
    ListFw(ListFw&& listP) : head{ listP.head }, tail{ listP.tail }, size{ listP.size }
    {
        listP.head = nullptr;
        listP.tail = nullptr;
        listP.size = 0;
        std::cout << "I liket to mov'it, mov'it! :[]\n";
    };
    ListFw(const std::initializer_list<ElemT> initList) : head{ nullptr }, tail{ nullptr }, size{ 0 }
    {
        for (const auto& elem : initList)
        {
            push_back(elem);
        }
    };
    bool empty()const { return size == 0; }
    size_t get_size()const { return size; }
    ElemT& front() { return head->data; }
    const ElemT& front()const { return head->data; }
    ElemT& back() { return tail->data; }
    const ElemT& back()const { return tail->data; }
    void push_front(const ElemT& data);
    void push_back(const ElemT& data);
    bool pop_front();
    bool pop_back();

    void insert_at(size_t idx, const ElemT& data);
    bool delete_at(size_t idx);

    void print()
    {
        if (!head) { std::cout << "[empty]"; }
        else
        {
            for (auto curr{ head }; curr; curr = curr->next)
            {
                std::cout << curr->data << ' ';
            }
        }
        std::cout << '\n';
    }

    void clear();
    ~ListFw();
    template <typename ElemT>
    friend std::ostream& operator<<(std::ostream& out, const ListFw<ElemT>& list);

    template <typename ElemT>
    friend ListFw<ElemT> operator+(const ListFw<ElemT>& lhs, const ListFw<ElemT>& rhs)
    {
        ListFw<ElemT> res;
        for (auto curr{ lhs.head }; curr; curr = curr->next)
        {
            res.push_back(curr->data);
        }
        for (auto curr{ rhs.head }; curr; curr = curr->next)
        {
            res.push_back(curr->data);
        }
        return res;
    };

    template <typename ElemT>
    friend ListFw<ElemT> operator*(const ListFw<ElemT>& lhs, const ListFw<ElemT>& rhs)
    {
        ListFw<ElemT> res;
        for (auto currL{ lhs.head }; currL; currL = currL->next)
        {
            for (auto currR{ rhs.head }; currR; currR = currR->next)
            {
                if (currL->data == currR->data)
                {
                    res.push_back(currL->data);
                    break;
                }
            }
        }
        return res;
    };
};

template <typename ElemT>
std::ostream& operator<<(std::ostream& out, const ListFw<ElemT>& list)
{
    if (!list.head) { out << "[empty]"; }
    else
    {
        for (auto curr{ list.head }; curr; curr = curr->next)
        {
            out << curr->data << ' ';
        }
    }
    return out;
}

template <typename ElemT>
void ListFw<ElemT>::push_front(const ElemT& data)
{
    head = new Node{ data, head };

    if (!tail) { tail = head; }
    ++size;
}

template <typename ElemT>
void ListFw<ElemT>::push_back(const ElemT& data)
{
    if (!head)
    {
        head = new Node{ data, head };
        tail = head;
    }
    else
    {
        tail->next = new Node{ data, nullptr };
        tail = tail->next;
    }
    ++size;
}

template <typename ElemT>
bool ListFw<ElemT>::pop_front()
{
    if (head)
    {
        Node* oldHead{ head };
        head = head->next;
        delete oldHead;
        --size;
        if (!size) { tail = nullptr; }
        return true;
    }
    return false;
}

template <typename ElemT>
bool ListFw<ElemT>::pop_back()
{
    if (tail)
    {
        if (tail == head)
        {
            delete tail;
            head = nullptr;
            tail = nullptr;
            size = 0;
            return true;
        }

        Node* curr{ head };
        for (; !(curr->next == tail); curr = curr->next);

        delete tail;
        curr->next = nullptr;
        tail = curr;
        --size;
        return true;
    }
    return false;
}

template <typename ElemT>
void ListFw<ElemT>::clear()
{
    while (head)
    {
        std::cout << "Clear for: " << front() << '\n';
        pop_front();
    }
}

template <typename ElemT>
ListFw<ElemT>::~ListFw()
{
    while (tail)
    {
        //std::cout << "Destruct for: " << back() << '\n';
        pop_back();
    }
}

template <typename ElemT>
void printListState(const ListFw<ElemT>& l)
{
    std::cout << "Size: " << l.get_size() << '\n';
    std::cout << "Front: " << l.front() << '\n';
    std::cout << "Back: " << l.back() << '\n';
}

template <typename ElemT>
typename ListFw<ElemT>::Node* ListFw<ElemT>::getNode(size_t idx)
{
    Node* curr{ nullptr };
    size_t currIdx;

    if (idx >= 0 and idx < size)
    {
        for (curr = head, currIdx = 0; currIdx < idx; curr = curr->next, ++currIdx);
    }
    return curr;
}

template <typename ElemT>
void ListFw<ElemT>::insert_at(size_t idx, const ElemT& data)
{
    Node* prev{ getNode(idx - 1) };
    Node* curr{ prev ? prev->next : nullptr };

    if (!curr or curr == head) { push_front(data); return; }
    else
    {
        prev->next = new Node{ data, curr };
    }
    ++size;
}

template <typename ElemT>
bool ListFw<ElemT>::delete_at(size_t idx)
{
    if (idx == 0) { pop_front(); return true; }
    Node* prev{ getNode(idx - 1) };
    Node* curr{ prev ? prev->next : nullptr };

    if (curr)
    {
        if (curr == head) { head = curr->next; }
        else
        {
            if (curr->next) { prev->next = curr->next; }
            else { tail = prev; prev->next = nullptr; }
        }
        --size;
        delete curr;
        return true;
    }
    return false;
}

int main()
{
    ListFw<int> a;
    a.push_back(1);
    a.push_back(2);
    a.push_back(3);
    a.push_back(4);
    std::cout << "a -> " << a << '\n';

    ListFw<int> b{ a };
    std::cout << "b -> " << b << '\n';

    ListFw<int> c;
    c.push_back(5);
    c.push_back(6);
    c.push_back(7);
    c.push_back(8);
    std::cout << "c -> " << c << '\n';

    ListFw<int> d{ b + c };
    std::cout << "d -> " << d << '\n';

    ListFw<int> e{ 1,3,5,7,3,5,7,1 };
    ListFw<int> f{ 2,1,4,6,7,1,6,7 };
    std::cout << "e -> " << e << '\n';
    std::cout << "f -> " << f << '\n';

    ListFw<int> g{ e * f };
    std::cout << "g -> " << g << '\n';

    return 0;
}