double linked list

void doubleList::doubleAddEnd(int item, doubleNode *&head, doubleNode *&tail)
{
    doubleNode *newNode = new doubleNode;
    newNode->next = NULL;
    newNode->data = item;
    if (head == NULL)
    {
        newNode->perv = NULL;
        head = tail = newNode;
    }
    else
    {
        newNode->perv = tail;
        tail->next = newNode;
        tail = newNode;
    }
}

//Lab functions
void doubleList::doubleAddBegin(int item, doubleNode *&head, doubleNode *&tail)
{
    doubleNode *newNode = new doubleNode;
    newNode->perv = NULL;
    newNode->data = item;
    if (head == NULL)
    {
        newNode->next = NULL;
        head = tail = newNode;
    }
    else
    {
        newNode->next = head;
        head->perv = newNode;
        head = newNode;
    }
}

//Lab functions
void doubleList::doubleAddByPosition(int item, doubleNode *&head, doubleNode *&tail, int pos)
{
    doubleNode *newNode = new doubleNode;
    newNode->next = NULL;
    newNode->data = item;
    doubleNode *temp;
    temp = head;
    int tempos = 1;
    if (head == NULL)
    {
        cout << "\nEmpty list, location not found\n";
    }
    else
    {
        while (tempos != pos)
        {
            if (temp == NULL)
            {
                cout << "The required location not found\n";
            }
            else
            {
                temp = temp->next;
            }
            tempos++;
        }
    }
    if (temp->next == NULL)
    {
        temp->next = newNode;
        newNode->perv = temp;
        newNode->next = NULL;
        tail = newNode;
    }
    else
    {
        newNode->perv = temp;
        newNode->next = temp->next;
        temp->next->perv = newNode;
        temp->next = newNode;
    }
}

//lab function
void doubleList::doubleAddByData(int item, doubleNode *&head, doubleNode *&tail, int value)
{
    doubleNode *newNode = new doubleNode;
    newNode->next = NULL;
    newNode->data = item;
    doubleNode *temp;
    temp = head;
    if (head == NULL)
    {
        cout << "\nEmpty list, location not found\n";
    }
    else
    {
        while (temp->data != value)
        {
            if (temp == NULL)
            {
                cout << "The required location not found\n";
            }
            else
            {
                temp = temp->next;
            }
        }
    }
    if (temp->next == NULL)
    {
        temp->next = newNode;
        newNode->perv = temp;
        newNode->next = NULL;
        tail = newNode;
    }
    else
    {
        newNode->perv = temp;
        newNode->next = temp->next;
        temp->next->perv = newNode;
        temp->next = newNode;
    }
}

//lab function
void doubleList::doubleDisplay(doubleNode *&head)
{
    doubleNode *temp = new doubleNode;
    temp = head;
    if (head == NULL)
    {
        cout << "Empty list\n";
    }
    else
    {
        while (temp != NULL)
        {
            cout << "--| " << temp->data << endl;
            temp = temp->next;
        }
    }
    cout << endl;
}

//lab function
void doubleList::doubleDeleteEnd(doubleNode *&head, doubleNode *&tail)
{
    if (head == NULL)
    {
        cout << "Empty list\n";
        return;
    }
    else
    {
        doubleNode *temp;
        temp = tail;
        if (temp->next == NULL && temp->perv == NULL)
        {
            head = tail = NULL;
            delete temp;
        }
        else
        {
            tail = tail->perv;
            tail->next = NULL;
            delete temp;
        }
    }
}

//lab function
void doubleList::doubleDeleteBegin(doubleNode *&head)
{
    if (head == NULL)
    {
        cout << "Empty list\n";
        return;
    }
    else
    {
        doubleNode *temp;
        temp = head;
        if (temp->next == NULL)
        {
            head = NULL;
            delete temp;
        }
        else
        {
            head = head->next;
            head->perv = NULL;
            delete temp;
        }
    }
}

//lab function
void doubleList::doubleDeleteByPosition(int pos, doubleNode *&head, doubleNode *&tail)
{
    doubleNode *temp;
    temp = head;
    int tempos = 1;
    if (head == NULL)
    {
        cout << "Empty list\n";
        return;
    }
    else
    {
        while (tempos != pos)
        {
            if (temp = NULL)
            {
                cout << "The required position not found\n";
                return;
            }
            else
            {
                temp = temp->next;
            }
            tempos++;
        }
    }
    if (temp->next == NULL && temp->perv == NULL)
    {
        head = tail = NULL;
        delete temp;
    }
    else if (temp == head)
    {
        head = head->next;
        head->perv = NULL;
        delete temp;
    }
    else if (temp->next == NULL)
    {
        tail = tail->perv;
        tail->next = NULL;
        delete temp;
    }
    else
    {
        temp->perv->next = temp->next;
        temp->next->perv = temp->perv;
        delete temp;
    }
}

//lab function
void doubleList::doubleDeleteByData(int value, doubleNode *&head, doubleNode *&tail)
{
    doubleNode *temp;
    temp = head;
    if (head == NULL)
    {
        cout << "Empty list\n";
        return;
    }
    else
    {
        while (temp->data != value)
        {
            if (temp = NULL)
            {
                cout << "The required position not found\n";
                return;
            }
            else
            {
                temp = temp->next;
            }
        }
    }
    if (temp->next == NULL && temp->perv == NULL)
    {
        head = tail = NULL;
        delete temp;
    }
    else if (temp == head)
    {
        head = head->next;
        head->perv = NULL;
        delete temp;
    }
    else if (temp->next == NULL)
    {
        tail = tail->perv;
        tail->next = NULL;
        delete temp;
    }
    else
    {
        temp->perv->next = temp->next;
        temp->next->perv = temp->perv;
        delete temp;
    }
}