Linked List Errors

Guys I keep getting these errors in this linked list template I'm trying to do. Can any one tell me what I'm doing wrong?

  #include <iostream>
#include <string>
using namespace std;

typedef string T;           // list element type
//typedef double T;           // list element type
const int SIZE = 11;        // maximum size of List
struct Node;                // forward reference

template <class T>
class LinkList		
{	
 protected :         // private data members
	int length;         // number of elements in list
	Node * head;        // pointer to data array
	Node * currPos;     // current position in list
    void inFront(T item);    // insert item at head of list
    void append(T item);     // insert item at tail of list
 public :           // public member functions
    //  Pre: None
    // Post: a list exist with room for SIZE elements of type T
    LinkList();         // default ctor
    //  Pre: list is created
    // Post: list is destructed, dynamic memory is freed
    ~LinkList();         // dtor
    //  Pre: None
    // Post: List is empty
	void makeMT();
    //  Pre: Key member of item is initialized
    // Post: If found, itemÕs key matches an elementÕs key in the list and a copy of 
    //	 that element has been stored in item; otherwise, item is unchanged
	void retrieve(T item, bool & found);
    //  Pre: List is initialized; List is not full; item is not in list
    // Post: item is in list
	void insert(T item); 
	//  Pre: an element in the list has a key that matches itemÕs
    // Post: no element in the list has a key that matches itemÕs
	void remove(T item); 	
    //  Pre: List is initialized
    // Post: Current position is prior to first element in list
	void reset();
    //  Pre: List is initialized; current position is defined; 
    //		element at current position is not last in list 
    // Post: current position is updated to next position; 
    // 		item is a copy of element at current position 
	void getNextItem(T & item); 	 
    //  Pre: List has been initialized
    // Post: Function value == (list is full)
	bool isFull() const; 
    //  Pre: List has been initialized
    // Post: Function value == (number of elements in list)
	int	getLength() const;  // returns length of list
    //  Pre: List has been initialized
    // Post: Function value == (number of elements in list)
	void prnt() const;  // prints the linked list
};


struct Node
{
    T data; 	//  Node data of type T
    Node * next;     //  link to next Node
    Node() : data(0), next(NULL)	
    { } // default c-tor for Node (numeric)	
    Node(const T & e, Node * nx = NULL) : data(e), next(nx) 
    { } // parameterized c-tor for Node
};  // end Node

// list.cpp - implementation file - array-based list 
//#include list.h

const char FRONT = 'f';     // 'f' for insert at front
const char APPEND = 'b';    // 'b' for append or insert at back
static char fORb = APPEND;     // 'f' for insert at front; 'b' for back
template <class T>
LinkList<T>::LinkList() : length(0), head(NULL)
{ } // end ctor

template <class T>
LinkList<T>::~LinkList()
{
    Node * upOne;
    Node * ptr = head;
    while (ptr != NULL) {
        head = ptr->next;   // traverse the list, 
        delete ptr;         // deleting each node 
        ptr = head;
    } // endwhile    
} // end dtor

template <class T>
void LinkList<T>::makeMT() 
{ 
	length = 0;
    head = NULL;
    LinkList::~LinkList();
} // end makeMT()

template <class T>
void LinkList<T>::insert(T item)
{
	if (fORb == FRONT)
        inFront(item);
    else
        append(item);
    ++length;
} // end insert()

template <class T>
void LinkList<T>::inFront(T item)
{
	Node * ptr = new Node(item, head);
    ptr->next = head;
    head = ptr;
} // end inFront()

template <class T>
void LinkList<T>::append(T item)
{
    Node * ptr = new Node(item);  // allocate new node with item
    Node * tail;    // ptr for traversing list
    if (!head)   // no nodes in list, insert as first node
        head = ptr;
    else {      // insert new Node at end
        tail = head;
        while (tail->next)  // travel to last node in the list
            tail = tail->next;
        tail->next = ptr;   // make new Node the last node
    } // endif
} // end append()

template <class T>
int LinkList<T>::getLength() const
{ 
	return length;
} // end getLength()

template <class T>
bool LinkList<T>::isFull() const
{
	return false;
} // end isFull()

template <class T>
void LinkList<T>::retrieve(T item, bool & found) 
{ 
    Node * loc = head; 
    found = false;
    while (loc && !found) {
        if (item == loc->data) { 
            found = true;
            item = loc->data;
        } // endif-thenpart
        else {
            loc = loc->next;
        } // endif-elsepart
    } // endwhile
} // end retrieve()

template <class T>
void LinkList<T>::remove(T item)
{ 
	Node * prev;
    Node * loc = head;
    if (!loc)       // if MT list, we are done
        return;
    if (loc->data == item) {    // remove first node
        head = loc->next;       // new head pointer
        delete loc;             // remove first node
    } // endif-thenpart
    else {
        while (loc && loc->data != item) {
            prev = loc;
            loc = loc->next;
        } // endwhile
		if (loc) {                    // if not at end of list,
            prev->next = loc->next;   // link previous node to one after 
            delete loc;               // delete node  
        } // endif
    } // endif-elsepart
    --length;       // decrement length
} // end remove()

template <class T>
void LinkList<T>::reset() 
{ 
	currPos = NULL;
} // reset()

template <class T>
void LinkList<T>::getNextItem(T & item) 
{
    if (!currPos) {
        currPos = head;
        //cout << endl << "head: " << head << '\t' << "curr: " << currPos << '\t';
        item = currPos->data;
        currPos = currPos->next;
        //cout << endl << "head: " << head << '\t' << "curr: " << currPos << '\t';
    } // endif-thenpart
    else {
        //cout << '\n' << "curr: " << currPos << '\t';
        if (currPos) {
            item = currPos->data;
            currPos = currPos->next;
            //cout << endl << "head: " << head << '\t' << "curr: " << currPos << '\t';
        } // endif
        //cout << '\t' << currPos->data << '\t';
    } // endif-elsepart
} // getNextItem()

template <class T>
void LinkList<T>::prnt() const
{
    Node * ptr = head;
    cout << "\nThe linked list: "; 
    while (ptr) {
        cout << ptr->data << '\t';
        ptr = ptr->next;
    }// endwhile
}

// print the list

void prnt(LinkList & al);
  
int main()
{
    LinkList frnds;
    bool isThere = false;
    
    prnt(frnds);
    frnds.retrieve("Joan", isThere);
    if (isThere)
        cout << "\n \"Joan\" already in list";
    else
        frnds.insert("Joan");
    prnt(frnds);
    frnds.insert("Brandi");
    frnds.insert("Sami");
    frnds.insert("Jill");
    frnds.insert("Sally");
    prnt(frnds);
    frnds.retrieve("Brandy", isThere);
    if (isThere)
        frnds.remove("Brandy");
    else
        cout << "\n \"Brandy\" not found";
    prnt(frnds);
    frnds.retrieve("Brandi", isThere);
    if (isThere)
        frnds.remove("Brandi");
    else
        cout << "\n \"Brandi\" not found";
    prnt(frnds);
    
    cout << "\n -- Done --\n";
    return 0;
}
 
/*int main()
{
    LinkList dbls;
    bool isThere = false;
 
    prnt(dbls);
    dbls.retrieve(-44.5, isThere);
    if (isThere)
        cout << "\n \"-44.5\" already in list";
    else
        dbls.insert(-44.5);
    dbls.insert(32.23);
    dbls.insert(17.92);
    dbls.insert(-65.72);
    dbls.insert(98.6);
    dbls.insert(45.36);
    prnt(dbls);
    dbls.retrieve(17.92, isThere);
    if (isThere)
        dbls.remove(17.92);
    else
        cout << "\n 17.92 not found";
    prnt(dbls);
    cout << "\n -- Done --\n";
    return 0;
}*/
 

void prnt(LinkList & al)
{
    al.reset();
    T val;
    if (al.getLength() > 0) {
        cout << "\nPrinting the list...";
        for (int k = 0; k < al.getLength(); ++k) {
            al.getNextItem(val);
            cout << "  "  << val;
        } // endfor
    } // endif-thenpart
    else
        cout << "\nThe list is MT...";
} // end prnt()

codewalker (394)

What errors?

JBIRD304 (65)

Lines 224 , 228 , and 288 it's saying argument list for class template "LinkList" is missing. Sorry for not specifying.

AbstractionAnon (6954)

Guys I keep getting these errors

Please be specific and post the exact error messages you're getting.

Line 61: Node is not a template. You can't use T here unless you make this a template also.

Line 224,228,288: Linklist is a template that expects 1 type. Therefore, you must specify a type here.

e.g.

    LinkList<string> frnds;

Last edited on

JBIRD304 (65)

So I need to make the struct a template?

AbstractionAnon (6954)

Yes, or declare it with your class.

codewalker (394)

There is no struct involved here. This involves LinkList which IS a templated class hence declaring a variable of that class will require you to specify the class T in template <class T>

So the lines with errors should look like what AbstractionAnon suggested as in similar to LinkList<string> frnds;

AbstractionAnon has I think guessed that you need to use strings but you decide and pass the correct data type

AbstractionAnon (6954)

codewalker wrote:
There is no struct involved here

.
There is indeed a struct here. See lines 59-67. That struct attempts to use T which is only valid within the scope of the templated class.

codewalker (394)

@AbstractionAnon; unfortunately the struct on these lines uses T from line 5 I think.
I just said there is no struct involved as JBIRD304 posted the lines with error on those lines, these lines/errors do not involve any structs I think.

JBIRD304 (65)

I tried to comment out line 5 but it gave me an error. The only way it would run is if I left it in. I wasn't sure if that defeated the purpose of making it a template class or not.

AbstractionAnon (6954)

I missed the typedef at line 5. That does allow the struct to compile. I was thinking that T was undefined at line 61.

If you had intended Node to work with different types, then Node should be templated or included within Linklist. The use of T within Node was misleading.

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