c++ - creating doubly linked list -

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i want create doubly linked list , check if empty. please tell mistake. error shown : in function empty(), head , tail out of scope. didn't work when define struct in class dict.

#include <iostream> #include <fstream> #include <string> using namespace std;  class node {   public:     string data;     node* next;     node* prev;     friend class dict; };  class dict {   public:     bool empty();     dict();     node* head;     node* tail;  };  dict::dict() {   head=new node;     tail= new node;     head->next=tail;     tail->prev=head;  }  bool empty() {     return head->next==tail; }  int main() {     dict my_list;     if(my_list.empty())         {cout<<"empty list"<<endl;}     else         {cout<<"not empty"<<endl;} }

i think need include empty method in class:

bool dict::empty() {     return head->next==tail; }

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