I'm working with code from a DVD Store example from chapter 16 of DS Malik's C++ Programming: Program Design Including Data Structures. There is an unordered list class that inherits from a linked list class, and when I compile all of the project files, I get 18 "Use of undeclared identifier" messages for every invocation of the inherited member variables first and count when the unordered linked list class is compiled. The files are copied and pasted and were not altered in any form. Compiling on a Windows machine resulted in no problems with this code, and my professor has claimed problems in the past with C++ compiling on macs.
Here is the parent class, linkedList.h:
#ifndef H_LinkedListType
#define H_LinkedListType
#include <iostream>
#include <cassert>
using namespace std;
//Definition of the node
template <class Type>
struct nodeType
{
Type info;
nodeType<Type> *link;
};
template <class Type>
class linkedListIterator
{
public:
linkedListIterator();
//Default constructor
//Postcondition: current = nullptr;
linkedListIterator(nodeType<Type> *ptr);
//Constructor with a parameter.
//Postcondition: current = ptr;
Type operator*();
//Function to overload the dereferencing operator *.
//Postcondition: Returns the info conatined in the node.
linkedListIterator<Type> operator++();
//Overload the pre-increment operator.
//Postcondition: The iterator is advanced to the next
// node.
bool operator==(const linkedListIterator<Type>& right) const;
//Overload the equality operator.
//Postcondition: Returns true if this iterator is equal to
// the iterator specified by right,
// otherwise it returns the value false.
bool operator!=(const linkedListIterator<Type>& right) const;
//Overload the not equal to operator.
//Postcondition: Returns true if this iterator is not
// equal to the iterator specified by
// right; otherwise it returns the value
// false.
private:
nodeType<Type> *current; //pointer to point to the current
//node in the linked list
};
template <class Type>
linkedListIterator<Type>::linkedListIterator()
{
current = nullptr;
}
template <class Type>
linkedListIterator<Type>::
linkedListIterator(nodeType<Type> *ptr)
{
current = ptr;
}
template <class Type>
Type linkedListIterator<Type>::operator*()
{
return current->info;
}
template <class Type>
linkedListIterator<Type> linkedListIterator<Type>::operator++()
{
current = current->link;
return *this;
}
template <class Type>
bool linkedListIterator<Type>::operator==
(const linkedListIterator<Type>& right) const
{
return (current == right.current);
}
template <class Type>
bool linkedListIterator<Type>::operator!=
(const linkedListIterator<Type>& right) const
{ return (current != right.current);
}
//***************** class linkedListType ****************
template <class Type>
class linkedListType
{
public:
const linkedListType<Type>& operator=
(const linkedListType<Type>&);
//Overload the assignment operator.
void initializeList();
//Initialize the list to an empty state.
//Postcondition: first = nullptr, last = nullptr, count = 0;
bool isEmptyList() const;
//Function to determine whether the list is empty.
//Postcondition: Returns true if the list is empty,
// otherwise it returns false.
void print() const;
//Function to output the data contained in each node.
//Postcondition: none
int length() const;
//Function to return the number of nodes in the list.
//Postcondition: The value of count is returned.
void destroyList();
//Function to delete all the nodes from the list.
//Postcondition: first = nullptr, last = nullptr, count = 0;
Type front() const;
//Function to return the first element of the list.
//Precondition: The list must exist and must not be
// empty.
//Postcondition: If the list is empty, the program
// terminates; otherwise, the first
// element of the list is returned.
Type back() const;
//Function to return the last element of the list.
//Precondition: The list must exist and must not be
// empty.
//Postcondition: If the list is empty, the program
// terminates; otherwise, the last
// element of the list is returned.
virtual bool search(const Type& searchItem) const = 0;
//Function to determine whether searchItem is in the list.
//Postcondition: Returns true if searchItem is in the
// list, otherwise the value false is
// returned.
virtual void insertFirst(const Type& newItem) = 0;
//Function to insert newItem at the beginning of the list.
//Postcondition: first points to the new list, newItem is
// inserted at the beginning of the list,
// last points to the last node in the list,
// and count is incremented by 1.
virtual void insertLast(const Type& newItem) = 0;
//Function to insert newItem at the end of the list.
//Postcondition: first points to the new list, newItem
// is inserted at the end of the list,
// last points to the last node in the list,
// and count is incremented by 1.
virtual void deleteNode(const Type& deleteItem) = 0;
//Function to delete deleteItem from the list.
//Postcondition: If found, the node containing
// deleteItem is deleted from the list.
// first points to the first node, last
// points to the last node of the updated
// list, and count is decremented by 1.
linkedListIterator<Type> begin();
//Function to return an iterator at the begining of the
//linked list.
//Postcondition: Returns an iterator such that current is
// set to first.
linkedListIterator<Type> end();
//Function to return an iterator one element past the
//last element of the linked list.
//Postcondition: Returns an iterator such that current is
// set to nullptr.
linkedListType();
//default constructor
//Initializes the list to an empty state.
//Postcondition: first = nullptr, last = nullptr, count = 0;
linkedListType(const linkedListType<Type>& otherList);
//copy constructor
~linkedListType();
//destructor
//Deletes all the nodes from the list.
//Postcondition: The list object is destroyed.
protected:
int count; //variable to store the number of
//elements in the list
nodeType<Type> *first; //pointer to the first node of the list
nodeType<Type> *last; //pointer to the last node of the list
private:
void copyList(const linkedListType<Type>& otherList);
//Function to make a copy of otherList.
//Postcondition: A copy of otherList is created and
// assigned to this list.
};
template <class Type>
bool linkedListType<Type>::isEmptyList() const
{
return(first == nullptr);
}
template <class Type>
linkedListType<Type>::linkedListType() //default constructor
{
first = nullptr;
last = nullptr;
count = 0;
}
template <class Type>
void linkedListType<Type>::destroyList()
{
nodeType<Type> *temp; //pointer to deallocate the memory
//occupied by the node
while (first != nullptr) //while there are nodes in the list
{
temp = first; //set temp to the current node
first = first->link; //advance first to the next node
delete temp; //deallocate the memory occupied by temp
}
last = nullptr; //initialize last to nullptr; first has already
//been set to nullptr by the while loop
count = 0;
}
template <class Type>
void linkedListType<Type>::initializeList()
{
destroyList(); //if the list has any nodes, delete them
}
template <class Type>
void linkedListType<Type>::print() const
{
nodeType<Type> *current; //pointer to traverse the list
current = first; //set current so that it points to
//the first node
while (current != nullptr) //while more data to print
{
cout << current->info << " ";
current = current->link;
}
}//end print
template <class Type>
int linkedListType<Type>::length() const
{
return count;
} //end length
template <class Type>
Type linkedListType<Type>::front() const
{
assert(first != nullptr);
return first->info; //return the info of the first node
}//end front
template <class Type>
Type linkedListType<Type>::back() const
{
assert(last != nullptr);
return last->info; //return the info of the last node
}//end back
template <class Type>
linkedListIterator<Type> linkedListType<Type>::begin()
{
linkedListIterator<Type> temp(first);
return temp;
}
template <class Type>
linkedListIterator<Type> linkedListType<Type>::end()
{
linkedListIterator<Type> temp(nullptr);
return temp;
}
template <class Type>
void linkedListType<Type>::copyList
(const linkedListType<Type>& otherList)
{
nodeType<Type> *newNode; //pointer to create a node
nodeType<Type> *current; //pointer to traverse the list
if (first != nullptr) //if the list is nonempty, make it empty
destroyList();
if (otherList.first == nullptr) //otherList is empty
{
first = nullptr;
last = nullptr;
count = 0;
}
else
{
current = otherList.first; //current points to the
//list to be copied
count = otherList.count;
//copy the first node
first = new nodeType<Type>; //create the node
first->info = current->info; //copy the info
first->link = nullptr; //set the link field of
//the node to nullptr
last = first; //make last point to the
//first node
current = current->link; //make current point to
//the next node
//copy the remaining list
while (current != nullptr)
{
newNode = new nodeType<Type>; //create a node
newNode->info = current->info; //copy the info
newNode->link = nullptr; //set the link of
//newNode to nullptr
last->link = newNode; //attach newNode after last
last = newNode; //make last point to
//the actual last node
current = current->link; //make current point
//to the next node
}//end while
}//end else
}//end copyList
template <class Type>
linkedListType<Type>::~linkedListType() //destructor
{
destroyList();
}//end destructor
template <class Type>
linkedListType<Type>::linkedListType
(const linkedListType<Type>& otherList)
{
first = nullptr;
copyList(otherList);
}//end copy constructor
//overload the assignment operator
template <class Type>
const linkedListType<Type>& linkedListType<Type>::operator=
(const linkedListType<Type>& otherList)
{
if (this != &otherList) //avoid self-copy
{
copyList(otherList);
}//end else
return *this;
}
#endif
Here is the code for the child class, unorderedLinkedList.h:
#ifndef H_UnorderedLinkedList
#define H_UnorderedLinkedList
#include "linkedList.h"
using namespace std;
template <class Type>
class unorderedLinkedList: public linkedListType<Type>
{
public:
bool search(const Type& searchItem) const;
//Function to determine whether searchItem is in the list.
//Postcondition: Returns true if searchItem is in the
// list, otherwise the value false is
// returned.
void insertFirst(const Type& newItem);
//Function to insert newItem at the beginning of the list.
//Postcondition: first points to the new list, newItem is
// inserted at the beginning of the list,
// last points to the last node in the
// list, and count is incremented by 1.
void insertLast(const Type& newItem);
//Function to insert newItem at the end of the list.
//Postcondition: first points to the new list, newItem
// is inserted at the end of the list,
// last points to the last node in the
// list, and count is incremented by 1.
void deleteNode(const Type& deleteItem);
//Function to delete deleteItem from the list.
//Postcondition: If found, the node containing
// deleteItem is deleted from the list.
// first points to the first node, last
// points to the last node of the updated
// list, and count is decremented by 1.
};
template <class Type>
bool unorderedLinkedList<Type>::
search(const Type& searchItem) const
{
nodeType<Type> *current; //pointer to traverse the list
bool found = false;
current = first; //set current to point to the first
//node in the list
while (current != nullptr && !found) //search the list
if (current->info == searchItem) //searchItem is found
found = true;
else
current = current->link; //make current point to
//the next node
return found;
}//end search
template <class Type>
void unorderedLinkedList<Type>::insertFirst(const Type& newItem)
{
nodeType<Type> *newNode; //pointer to create the new node
newNode = new nodeType<Type>; //create the new node
newNode->info = newItem; //store the new item in the node
newNode->link = first; //insert newNode before first
first = newNode; //make first point to the
//actual first node
count++; //increment count
if (last == nullptr) //if the list was empty, newNode is also
//the last node in the list
last = newNode;
}//end insertFirst
template <class Type>
void unorderedLinkedList<Type>::insertLast(const Type& newItem)
{
nodeType<Type> *newNode; //pointer to create the new node
newNode = new nodeType<Type>; //create the new node
newNode->info = newItem; //store the new item in the node
newNode->link = nullptr; //set the link field of newNode
//to nullptr
if (first == nullptr) //if the list is empty, newNode is
//both the first and last node
{
first = newNode;
last = newNode;
count++; //increment count
}
else //the list is not empty, insert newNode after last
{
last->link = newNode; //insert newNode after last
last = newNode; //make last point to the actual
//last node in the list
count++; //increment count
}
}//end insertLast
template <class Type>
void unorderedLinkedList<Type>::deleteNode(const Type& deleteItem)
{
nodeType<Type> *current; //pointer to traverse the list
nodeType<Type> *trailCurrent; //pointer just before current
bool found;
if (first == nullptr) //Case 1; the list is empty.
cout << "Cannot delete from an empty list."
<< endl;
else
{
if (first->info == deleteItem) //Case 2
{
current = first;
first = first->link;
count--;
if (first == nullptr) //the list has only one node
last = nullptr;
delete current;
}
else //search the list for the node with the given info
{
found = false;
trailCurrent = first; //set trailCurrent to point
//to the first node
current = first->link; //set current to point to
//the second node
while (current != nullptr && !found)
{
if (current->info != deleteItem)
{
trailCurrent = current;
current = current-> link;
}
else
found = true;
}//end while
if (found) //Case 3; if found, delete the node
{
trailCurrent->link = current->link;
count--;
if (last == current) //node to be deleted
//was the last node
last = trailCurrent; //update the value
//of last
delete current; //delete the node from the list
}
else
cout << "The item to be deleted is not in "
<< "the list." << endl;
}//end else
}//end else
}//end deleteNode
#endif
I have been able to get this to compile by prefixing every invocation of first and count with this->, but this only got me compiled classes whose search methods did not work.
Maybe the author of the textbook put in some things that are Windows specific? Or maybe there is indeed a problem with the compiler (Apple LLVM 7.0) that I am using. This problem seems related: C++ inheritance/undeclared identifier issue and, although the problem seems a bit vague, it seems to suggest that DS Malik's code is poorly written.
If the problem is the compiler, please provide details on how to use a recommended compiler with XCode.
