Thread: Help w/nodes

I keep getting the same five errors in my code and cannot figure out what I am doing wrong. I am using Visual C++. I can get the same code to compile at school on a linux workstation though.

I have been looking at this for awhile now and I'm ready to throw my computer out the window. Can someone please tell me what is so obvious that I am not seeing? Thanks in advance.

The compiler does not like my file node.h. Here are the errors I am getting.

node.h(10) : error C2146: syntax error : missing ';' before identifier 'data'
node.h(10) : error C2501: 'string' : missing storage-class or type specifiers
node.h(10) : error C2501: 'data' : missing storage-class or type specifiers
node.h(14) : error C2629: unexpected 'class Node ('
node.h(14) : error C2334: unexpected token(s) preceding '{'; skipping apparent function body
Error executing cl.exe.

main.obj - 5 error(s), 0 warning(s)

[code]
//node.h
#ifndef _NODE_H_
#define _NODE_H_

#include "list.h"

#include <string>
using std::string;

class Node {
friend class List; //doesn't appear to like this code
private:
string data;
Node *next;
public:
Node(string item, Node *ptr) {data = item; next = ptr;}

};

#endif
-------------
//stack.h
#include "list.h"

class Stack :private List {
public:
string pop() {
string retval = showHead();
removeHead();
return retval;
}

void push(string item) {insertAtHead(item);}

void print() {List::print();}
};
---------
//list.h
#ifndef _LIST_H_
#define _LIST_H_

#include "node.h"
#include <string>
using std::string;

class List {
private:
Node *head;
Node *tail;
public:
List() {head=NULL; tail=NULL;}
void insertAtHead(string item);
void insertAtTail(string item);
string showHead();
void removeHead();
void print();
};
#endif
-----------
//list.cpp
#include "list.h"
#include <iostream>

using std::cout;
using std::endl;

void List::print() {
Node* ptr = head;
while (ptr != NULL) {
cout << ptr->data << ", ";
ptr = ptr->next;
}
cout << endl;
}


void List::insertAtHead(string item) {
// insert item at the front of the list pointed to by head
// assumes that this is a valid list
head = new Node(item, head);
if (tail == NULL) {
tail = head;
}
}

void List::insertAtTail(string item) {
// insert item at the end of the list pointed to by head
// assumes that this is a valid list

if (head == NULL) { // if the list is empty,
insertAtHead(item); // the beginning is the same as the end
}
else {
tail->next = new Node(item, NULL);
tail = tail->next;
}
}

void List::removeHead() {
// decapitate the list pointed to by head
// assumes that this is a valid list

if (head != NULL) { // something to delete
Node *deleteMe = head;
head = head -> next;
delete (deleteMe);
if (head == NULL) { // the list is now empty
tail = NULL;
}
}
}

string List::showHead() {
// show the first value of the list pointed to by head
// assumes that this is a valid list
if (head != NULL) {
return head->data;
}
else {
return "ERROR";
}
}
-------------
//main.cpp
#include "list.h"
#include "stack.h"

int main() {
List l1;
l1.insertAtHead("Hello");
l1.insertAtHead("Welcome");
l1.insertAtHead("Greetings");
l1.print();
l1.removeHead();
l1.print();

Stack s;
s.push("Hello");
s.push("Welcome");
s.push("Greetings");
s.print();
s.pop();
s.print();
return 0;

}

[code/]

Please fix your code tags, and I'll take a look.
It's [/code] not [code/]

Thanks! Here goes . . .

Code:

//node.h
#ifndef _NODE_H_
#define _NODE_H_

#include "list.h"

#include <string>
using std::string;

class Node {
	 friend class List;
 private:
	 string data;
    Node *next;
 public:
    Node(string item, Node *ptr) {data = item; next = ptr;}

};

#endif
---------
//stack.h
#include "list.h"

class Stack :private List {
 public:
	 string pop() {
	string retval = showHead();
	removeHead();
	return retval;
    }

	 void push(string item) {insertAtHead(item);}

    void print() {List::print();}
};
-------
//list.h
#ifndef _LIST_H_
#define _LIST_H_

#include "node.h"
#include <string>
using std::string;

class List {
 private:
	 Node *head;
	 Node *tail;
 public:
	 List() {head=NULL; tail=NULL;}
	 void insertAtHead(string item);
	 void insertAtTail(string item);
	 string showHead();
	 void removeHead();
	 void print();
};
#endif
---------
//list.cpp
#include "list.h"
#include <iostream>

using std::cout;
using std::endl;

void List::print() {
    Node* ptr = head;
	 while (ptr != NULL) {
	cout << ptr->data << ", ";
	ptr = ptr->next;
    }
	 cout << endl;
}


void List::insertAtHead(string item) {
    // insert item at the front of the list pointed to by head
	 // assumes that this is a valid list
    head = new Node(item, head);
    if (tail == NULL) {
		tail = head;
    }
}

void List::insertAtTail(string item) {
    // insert item at the end of the list pointed to by head
	 // assumes that this is a valid list

    if (head == NULL) {     // if the list is empty, 
		insertAtHead(item); // the beginning is the same as the end
    }
    else {
		tail->next = new Node(item, NULL);
		tail = tail->next;
	 }
}

void List::removeHead() {
	 // decapitate the list pointed to by head
	 // assumes that this is a valid list

    if (head != NULL) { // something to delete
		Node *deleteMe = head;
		head = head -> next;
		delete (deleteMe);
		if (head == NULL) {   // the list is now empty
			tail = NULL;
		}
    }
}

string List::showHead() {
    // show the first value of the list pointed to by head
    // assumes that this is a valid list
	 if (head != NULL) {
		return head->data;
	 }
    else {
		return "ERROR";
	 }
}



-----------
//main.cpp
#include "list.h"
#include "stack.h"

int main() {
    List l1;
	 l1.insertAtHead("Hello");
	 l1.insertAtHead("Welcome");
	 l1.insertAtHead("Greetings");
	 l1.print();
	 l1.removeHead();
	 l1.print();

	 Stack s;
	 s.push("Hello");
	 s.push("Welcome");
    s.push("Greetings");
	 s.print();
	 s.pop();
	 s.print();
	return 0;

}

Proceed with throwing the computer. I can't see anything wrong with your code :/ Sorry, I looked it over for about 5 minutes.. but nothing stands out as being wrong.

lol! Thanks for looking at it. It's very frustrating for this code to compile at school and then I can't get the !@$%^ code to compile at home. I think it's time to work on another project for my class. Thanks again!