struct Node {
   Element data;
   Node * prev = NULL;
   Node * next = NULL;
}
Node first;        // reference to the first (beginning) node of the Deque
Node last;        // reference to the last (end) node of the Deque

// add node/element to front of queue
void push ( Element D )
{
   Node temp;
   temp->data = D:
   temp->next = first->next;
   if ( first == last ){
       last = temp;
       first = last;
   }else {
       first = temp;
   }
}
// remove first node of the Deque and return the element from that node
Element pop() {
   if ( last == NULL && First == NULL )
       return NULL;
   Node  temp;
   temp = first;            // store node
   first = first->next;    // change pointer to next node
   return temp->data;        }
// add node to end of the Deque
void inject ( Element D ) {
   Node temp;
   temp->data = D:
   temp->next = first->next;
   if ( first == last ){
       last = temp;
       first = last;
   }else {
       first = temp;
   }
}
// remove last node of the Deque and return the content from that node
Element eject() {
   if ( last == NULL && First == NULL )
       return NULL;
   Node  temp;
   temp = first;            // store node
   first = first->next;    // change pointer to next node
   return temp->data;        }