The DLLIST MergeSort Agent:

All of the functions to implement the mergesort algorithm are implemented in the split, merge and mergesort agents in the DL_CELL class. We can utilize this capability with a call to the mergesort agent for the DL_CELL object pointer head.

    // ************************************ //
    //      merge sort for CHAR_DLLIST      //
    // ************************************ // 
void CHAR_DLLIST::mergesort()
{
   head = head->mergesort(head);
   //must reset end
   if(head==NULL) exit(-1);
   else{   
     CHAR_DL_CELL *again,*before;
     again = head->next;
     while(!(again==NULL)){
       before = again;
       again = again->next;
       }
     end = before;
     end->next = NULL;    
     }    
}