Question

I am writing a program in c++ which implements a doubly-linked list that holds a single character in each node. I am inserting characters via the append function:

doubly_linked_list adam; adam.append('a'); 

This function is implemented as follows:

//Append node     node* append(const item c){          //If the list is not empty...         if(length){             //maintain pointers to end nodes             node* old_last_node = last;             node* new_last_node = new node;              //re-assign the double link and exit link             old_last_node->next = new_last_node;             new_last_node->back = old_last_node;             new_last_node->next = NULL;              //re-assign the last pointer             last = new_last_node;         }         //If this is the first node         else{             //assign first and last to the new node             last = first = new node;              //assign nulls to the pointers on new node             first->next = first->back = NULL;         }          //increase length and exit         ++length;         return last;     } 

However, I think there is an issue, perhaps with the way C++ handles characters. When I go to print my list, somehow I never get the characters to print which I have appended to my list. This is what I’m using to print:

//Friendly output function     friend std::ostream& operator << (std::ostream& out_s, const doubly_linked_list& source_list){         //create iteration node pointer         node* traverse_position = source_list.first;          //iterate through, reading from start         for(int i = 1; i <= source_list.length; ++i){             //print the character             out_s << (traverse_position->data);             traverse_position = traverse_position->next;         }          //return the output stream         return out_s;     } 

I just get crap when I print it. It prints characters that I never appended to my list – you know, just characters just from somewhere in the memory. What could possibly be causing this?

Answer 1

Where are you assigning the value c in the append() function? I fear you may have concentrated too much on the doubly-linked-list part and not enough on the storing-data part. 🙂