I cant find the error in which my double linked list wont display .pdf

I can't find the error in which my double linked list won't display help me pls
#include
using namespace std;
typedef string Elem;
class DNode {
private:
Elem elem;
DNode* prev;
DNode* next;
friend class DLinkedList;
};
class DLinkedList {
public:
DLinkedList();
~DLinkedList();
bool empty() const;
const Elem& front() const;
const Elem& back() const;
void addFront(const Elem& e);
void addBack(const Elem& e);
void removeFront();
void removeBack();
void print(); // prints the doubly linked list
void insertElem(const Elem& e); // inserts element e in ascending order
void deleteElem(const Elem& e); // deletes element e
private:
DNode* header;
DNode* trailer;
protected:
void add(DNode* v, const Elem& e);
void remove(DNode* v);

};
DLinkedList::DLinkedList() {
header = new DNode;
trailer = new DNode;
header->next = trailer;
trailer->prev = header;
}
DLinkedList::~DLinkedList() {
while (!empty()) removeFront();
delete header;
delete trailer;
}
bool DLinkedList::empty() const {
return (header->next == trailer);
}
const Elem& DLinkedList::front() const {
return header->next->elem;
}
const Elem& DLinkedList::back() const {
return trailer->prev->elem;
}
void DLinkedList::add(DNode* v, const Elem& e) {
DNode* u = new DNode;
u->elem = e;
u->next = v;
u->prev = v->prev;
v->prev->next = v->prev = u;
}

void DLinkedList::addFront(const Elem& e) {
add(header->next, e);
}
void DLinkedList::addBack(const Elem& e) {
add(trailer, e);
}
void DLinkedList::remove(DNode* v) {
DNode* u = v->prev;
DNode* w = v->next;
u->next = w;
w->prev = u;
delete v;
}
void DLinkedList::removeFront() {
remove(header->next);
}
void DLinkedList::removeBack() {
remove(trailer->prev);
}
void DLinkedList::print() {
DNode* cur = header->next; // First element in the list is header->next
while (cur != trailer) { // Loop until the end is not reached
cout<elem<<" "; // Print the element
cur = cur->next; // Increment the pointer
}
cout<next;
while (cur != trailer && cur->elem < e) { // Loop until end of list or current element becomes
equal to or more than e
cur = cur->next;
}

add(cur, e); // Add e just before cur
}
void DLinkedList::deleteElem(const Elem& e) {
DNode* cur = header->next;
while (cur != trailer && cur->elem != e) { // Loop until end of list or current element matches e
cur = cur->next;
}
if (cur != trailer) { // If element is found
remove(cur); // Remove this node
}
}
int main() {
DLinkedList dlist;
dlist.addFront("c");
dlist.addFront("a");
dlist.addBack("d");
dlist.print(); // prints a c d
dlist.insertElem("b");
dlist.print(); // prints a b c d
dlist.deleteElem("d");
dlist.print(); // prints a b c
return 0;
}

I cant find the error in which my double linked list wont display .pdf

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I cant find the error in which my double linked list wont display .pdf