c++ - DoublyLinkedList. Does nothing when trying to insert between 2 nodes -

im having problem dll insert function. has no problem appending onto list when have list of 5 objects , want insert in between nodes nothing. have been looking around hours resolve , nothing has changed.

here code: implementation in main.cpp

cout << "\n---------------------------insert---------------------------\n";         //ask user position want enter player in.         cout << "enter position want enter player: ";         int insertchoice = validators.getnum();         //move iterator start.         itr.start();         //if position not equal zero, continue.         if (insertchoice != 0)         {             //loop until position entered reached.             (int = 0; < insertchoice; i++)             {                 //move iterator forware position.                 itr.forth();             }         //insert player position entered user.         //list.insert(itr,stats.input());         }         //if position entered equal zero, continue.         else         {             //append onto list.(add onto start).             list.append(stats.input());         } 

insert function in header file.

// ---------------------------------------------------------------------------------------------------------------- //  name:           insert //  description:    inserts data before iterator, works whether iterator backwards of forwards //                  through list.inserts @ end of list if iterator invalid. //  arguments:      p_iterator: iterator insert before //                  p_data: data insert //  return value:   none. // ----------------------------------------------------------------------------------------------------------------     void insert(doublylinkedlistiterator<datatype>& p_itr, datatype p_data)     {         if(p_itr.m_node != 0)         {             // insert data before iterator             p_itr.m_node->insertbefore(p_data);              //if iterator @ head of list,             //reset head pointer             if(p_itr.m_node == m_head)             {                 m_head = m_head->m_prev;             }             // increment count             m_count++;         }         else         {             append(p_data);         }     } 

append

void append(datatype p_data)     {         if(m_head == 0)         {             // create new head node.             m_head= m_tail= new doublylistnode<datatype>;             m_head->m_data= p_data;             m_head->m_next= 0;             m_head->m_prev= 0;         }         else         {             // insert new node after tail , reset tail.             m_tail->insertafter(p_data);             m_tail= m_tail->m_next;         }         m_count++;     } 

insertbefore

// ---------------------------------------------------------------- //  name:           insertbefore //  description:    adds node before current node. //  arguments:      p_data - data store in new node. //  return value:   none. // ----------------------------------------------------------------  void insertbefore(datatype p_data) {     //create new node     doublylinkedlistnode<datatype>* newnode = new doublylinkedlistnode<datatype>;     newnode->m_data = p_data;     //set new node pointers     newnode->m_next = this;     newnode->m_prev = m_prev;     //if theres node before it, make point new node     if(m_prev != 0)     m_prev = newnode; } 

i dont think problem lies int implementation in main rather in actual insert function. in advance, becca.

insertbefore

newnode->m_next = this; newnode->m_prev = this->m_prev; 

you need tell this point (as previous) new node too.

newnode->m_next = this; newnode->m_prev = this->m_prev; this->m_prev->m_next = newnode; this->m_prev = newnode; 

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this should be

insert function in header file.

 if(p_itr.m_node == m_head)  {       m_head = p_itr->m_prev;                ^^^^^^  }