Class not declared in scope in main

Question

"dlist_test.cc:16: error: 'testList' was not declared in this scope.

dlist_test.cc:16: error: 'Dlist' was not declared in this scope."

I have been looking at other threads on circular dependences or namespace but I only have one header file, and I'm not using a namespace for dlist.h or dlist.cc. Where am I not declaring this correctly? Is it a Makefile problem? Any help would be appreciated, thank you for your time.

dlist.h:

#ifndef DLIST_H
#define DLIST_H

struct ListNode 
{
  /* define your list node type */
  int val;
  ListNode* next;
  ListNode* prev;
};

class DList
{
  public:
  DList();
  /* implement copy constructor, assignment, destructor if needed */
  void add_to_front(int value);
  void add_to_back(int value);
  int first();
  int last();
  void remove(ListNode* node);
  ListNode* previous(ListNode* node);
  ListNode* next(ListNode* node);
  ListNode* search_value(int value);

  private:
  /* declare your data */
  ListNode* head;
  ListNode* tail;
};

#endif

dlist.cc

#include "dlist.h"
#include <cstddef>
#include <stdlib.h>

class Dlist{
   public:

      Dlist(){
               head = NULL;
               tail = NULL;
      }

      void add_to_front(int value){ 
         struct ListNode* newhead = (struct ListNode*) malloc(sizeof(struct ListNode)); 
         newhead->val  = value; 
         newhead->prev = NULL; 
         newhead->next = head;     
         if(head !=  NULL) 
            head->prev = newhead ;     
         head = newhead; 
      }   

      void add_to_back(int value){
         if (tail == NULL){
            struct ListNode* firstValue = (struct ListNode*)malloc(sizeof(ListNode));
            firstValue->val = value;
            firstValue->prev = NULL;
            firstValue->next = NULL;
            tail = firstValue;
         }else{
            struct ListNode* newtail = (struct ListNode*)malloc(sizeof(ListNode));
            newtail->val = value;
            newtail->next = NULL;
            newtail->prev = tail;

            tail->next = newtail;

            tail = newtail;
         }
      }

      int first(){
         return head->val;
      }

      int last(){
         return tail->val;
      }

      void remove(ListNode* node){
         if (head == NULL || node == NULL){
            return;
         }

         if(head == node){
            head = node->next;
         }

         if (node->next != NULL){
            node->next->prev = node->prev;
         }
         if (node->prev != NULL){
            node->prev->next = node->next;
         }
         free(node);
      }

      ListNode* previous(ListNode* node){
         if(node->prev != NULL){
            return node->prev;
         }
      }

      ListNode* next(ListNode* node){
         if(node->next != NULL){
            return node->next;
         }
      }

      ListNode* search_value(int value){
         while(head->next != NULL){
            if(head->next->val == value){
               return head;
            }else{
               head = head->next;
            }
         }
      }
   private:
      ListNode* head;
      ListNode* tail;

   };

dlist_test.cc

#include <assert.h>
#include <stdlib.h>
#include <stdio.h>
#include <time.h>
#include "dlist.h"
#include <bits/stdc++.h> 
using namespace std; 

int main (int argc, char* argv[])
{
  int N = -1;
  if (argc == 2) {
    N = atoi (argv[1]);
    assert (N > 0);
  } 
  testList = Dlist();
  int i = 0;
  while(i<N){
    testList.add_to_back(i+1);
    i++;
  }
  int randn = rand() % N + 1;// randn in the range 1 to N
  //
  time_t start, end;
  time(&start); 
  ios_base::sync_with_stdio(false); 
  struct ListNode* loc = testList.search_value(randn);
  testList.remove(loc);
  time(&end); 
  double time_taken = double(end - start); 
    cout << "Time taken by program is : " << fixed 
         << time_taken << setprecision(5); 
    cout << " sec " << endl; 
  //
  testList.add_to_front(N);


  return 0;
}

Makefile:

default:
    @echo "=================================================="
    @echo "To build your sorting code, use:"
    @echo "make dlist_test or  make queue_test"
    @echo "=================================================="

# Queue driver
queue_test: queue.o


# Doubly linked list driver
dlist_test: dlist.o dlist_test.o
    g++ -o dlist_test dlist.o dlist_test.o

dlist.o: dlist.cc dlist.h
    g++ -c dlist.cc

dlist_test.o: dlist_test.cc
    g++ -c dlist_test.cc

clean:
    rm -f core *.o *~ queue_test dlist_test

# eof

Answer 1

These are two different problems:

1) C++ distinguishes uppercase letters from lowercase ones. You declared the class as DList so you need write this name exactly this way. Dlist (with lower case "L") is considered an entirely different name.

2) You've never created variable testList so C++ is right to tell that it doesn't exist. It happens to the best ;) Just change the line

testList = Dlist();

to

Dlist testList = Dlist();

or

Dlist testList;

The both variants are equivalent. C++ will use a constructor without parameters by default.