When I compile my code for a linked list, I get a bunch of undefined reference errors. The code is below. I have been compiling with both of these statements:
g++ test.cpp
as well as
g++ LinearNode.h LinearNode.cpp LinkedList.h LinkedList.cpp test.cpp
I really do not understand why I am getting these errors because I am really rusty on classes in C++. I could really use some help.
LinearNode.h:
#ifndef LINEARNODE_H
#define LINEARNODE_H
#include<iostream>
using namespace std;
class LinearNode
{
public:
//Constructor for the LinearNode class that takes no arguments
LinearNode();
//Constructor for the LinearNode class that takes the element as an argument
LinearNode(int el);
//returns the next node in the set.
LinearNode* getNext();
//returns the previous node in the set
LinearNode* getPrevious();
//sets the next element in the set
void setNext(LinearNode* node);
//sets the previous element in the set
void setPrevious(LinearNode* node);
//sets the element of the node
void setElement(int el);
//gets the element of the node
int getElement();
private:
LinearNode* next;
LinearNode* previous;
int element;
};//ends the LinearNode class
#endif
LinearNode.cpp:
#ifndef LINEARNODE_cpp
#define LINEARNODE_cpp
#include<iostream>
#include"LinearNode.h"
using namespace std;
//Constructor for LinearNode, sets next and element to initialized states
LinearNode::LinearNode()
{
next = NULL;
element = 0;
}//ends LinearNode default constructor
//Constructor for LinearNode takes an element as argument.
LinearNode::LinearNode(int el)
{
next = NULL;
previous = NULL;
element = 0;
}//ends LinearNode constructor
//returns the next element in the structure
LinearNode* LinearNode::getNext()
{
return next;
}//ends getNext function
//returns previous element in structure
LinearNode* LinearNode::getPrevious()
{
return previous;
}//ends getPrevious function
//sets the next variable for the node
void LinearNode::setNext(LinearNode* node)
{
next = node;
}//ends the setNext function
//sets previous for the node
void LinearNode::setPrevious(LinearNode* node)
{
previous = node;
}//ends the setPrevious function
//returns element of the node
int LinearNode::getElement()
{
return element;
}//ends the getelement function
//sets the element of the node
void LinearNode::setElement(int el)
{
element = el;
}//ends the setElement function
#endif
LinkedList.h:
#ifndef LINKEDLIST_H
#define LINKEDLIST_H
#include<iostream>
#include"LinearNode.h"
using namespace std;
class LinkedList
{
public:
LinkedList();
void add(int element);
int removie (int element);
private:
int count;
LinearNode *contents;
};//ends the class linked list
#endif
LinkedList.cpp:
#ifndef LINKEDLIST_CPP
#define LINKEDLIST_CPP
#include<iostream>
#include"LinearNode.h"
#include"LinkedList.h"
using namespace std;
//linkedlist constructor for an empty linked list
LinkedList::LinkedList()
{
count = 0;
contents = NULL;
}//ends the constructor
//adds an element to the front of the linked list
void LinkedList::add(int element)
{
int found = 0, current = 0;
while( (found == 0) && (current !=count) )
{
if (contents.getElement() == element)
found = 1;
else
{
contents = contents.getNext();
current++;
}//ends the else statement
}//ends the while loop
if (found == 0)
{
LinearNode node = new LinearNode(element);
node.setNext(contents);
contents.setPrevious(node);
count++;
}//ends the found == 0 if statment
}//ends the add function
//this function removes one element from the linked list.
int LinearNode::remove(int element)
{
int found = 0;
if (count == 0)
cout << "The list is empty" << endl;
else
{
if (contents.getElement() == element)
{
result = contents.getElement();
contents = contents.getNext();
}//ends the contents.getElement() == element
else
{
previous = contents;
current = contents.getNext();
for (int index = 0; ( (index < count) && (found == 0) )index++)
if (current.getElement() = element)
found = 1;
else
{
previous = current;
current = current.getNext();
}//ends the else statement
if (found == 0)
cout << "The element is not in the list" << endl;
else
{
result = current.getElement();
previous.setNext(current.getNext());
}//ends else statement
}//ends the else stamtement
count--;
}//ends the else statement of count == 0
return result;
}//ends the remove function
#endif
test.cpp:
#include<iostream>
#include"LinearNode.h"
#include"LinkedList.h"
using namespace std;
int main()
{
LinearNode node1, node2, node3, move;
LinkedList list;
node1.setElement(1);
node2.setElement(2);
node3.setElement(3);
}
Answer
- Usually headers guards are for header files (i.e.,
.h) not for source files ( i.e.,.cpp). - Include the necessary standard headers and namespaces in source files.
LinearNode.h:
#ifndef LINEARNODE_H
#define LINEARNODE_H
class LinearNode
{
// .....
};
#endif
LinearNode.cpp:
#include "LinearNode.h"
#include <iostream>
using namespace std;
// And now the definitions
LinkedList.h:
#ifndef LINKEDLIST_H
#define LINKEDLIST_H
class LinearNode; // Forward Declaration
class LinkedList
{
// ...
};
#endif
LinkedList.cpp
#include "LinearNode.h"
#include "LinkedList.h"
#include <iostream>
using namespace std;
// Definitions
test.cpp is source file is fine. Note that header files are never compiled. Assuming all the files are in a single folder -
g++ LinearNode.cpp LinkedList.cpp test.cpp -o exe.out