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exceptions problem just dont understand

LiverEatnJohnson (23)
The real problem is i just don't understand exceptions at all. Here is what I got it is a stack program.

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/**
 * Passes the top tag from the stack
 * @param me, tag to be returned
 * @throws StackException
 */
void TagStack::get(Tag &me) throw (StackException) {
    if (!isEmpty()) {
        me = top->tag;
    }
    throw StackException("StackException: Stack is empty can't get.");
}

/**
 * Takes the top tag off the stack
 * @throws StackException.
 */
void TagStack::pop() throw (StackException) {
    if (!isEmpty()) {
        TagStackNode *temp;

        temp = top;
        top = temp->next;
        delete temp;
    }
    throw StackException("StackException: Stack is empty can't pop.");
}

/**
 * Puts a new tag on top of the stack
 * @param me, tag to be put on top
 * @throws StackException                                                  
 */
void TagStack::push(Tag me) throw (StackException) {
    try{
        TagStackNode *node = new TagStackNode;
        node->tag = me;
        node->next = top;
        top = node;
    }catch(StackException &e){
        throw StackException("StackException: push can't allocate memory.");
    }
}


on each throw line netbeans gives me this.
/home/bullfrog/NetBeansProjects/CnCpp/XmlValidator/TagStack.cpp:69: undefined reference to `StackException::StackException(std::basic_string<char, std::char_traits<char>, std::allocator<char> >)'

here is my stackexception.h file

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/******************************************** 
 * Project:     XmlValidator
 * File:        StackException.h
 * Author:      Jeremiah Johnson
 * Assignments: Stack
 * Date:        November 15, 2011
 ********************************************/

#ifndef STACKEXCEPTION_H
#define	STACKEXCEPTION_H

#include <exception>
#include <string>
#include <stdexcept>

using namespace std;

class StackException: public exception {
public:
    StackException(); throw ();
    
    StackException(string explain) throw ();

    virtual const char* what() const throw ();
};

#endif	/* STACKEXCEPTION_H */


i really need a better understanding of exceptions and what might be missing from my program
Peter87 (11234)
did you include StackException.h?

Also you have a bug in your get and pop function. They will always throw.
LiverEatnJohnson (23)
yes i did include StackException.h and i changed the pop to say

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/**
 * Takes the top tag off the stack
 * @throws StackException.
 */
void TagStack::pop() throw (StackException) {
    if (!isEmpty()) {
        TagStackNode *temp;

        temp = top;
        top = temp->next;
        delete temp;
    } else {
        throw StackException("StackException: Stack is empty can't pop.");
    }
}


that should fix the allways throw u were mentioning thanks any other ideas.
Peter87 (11234)
The undefined reference error says it can't find the definition of the StackException constructor. Did you define it somewhere?
LiverEatnJohnson (23)
I think i did that is what i mean by i don't understand exceptions yet i have the .h file right here.

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/******************************************** 
 * Project:     XmlValidator
 * File:        StackException.h
 * Author:      Jeremiah Johnson
 * Assignments: Stack
 * Date:        November 15, 2011
 ********************************************/

#ifndef STACKEXCEPTION_H
#define	STACKEXCEPTION_H

#include <exception>
#include <string>
#include <stdexcept>

using namespace std;

class StackException: public exception {
public:
    StackException(); throw ();
    
    StackException(string explain) throw ();

    virtual const char* what() const throw ();
};

#endif	/* STACKEXCEPTION_H */


or do I need to do it more like any other variable like this

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/**
 * Takes the top tag off the stack
 * @throws StackException.
 */
void TagStack::pop() throw (StackException) {
    StackException exception;
    if (!isEmpty()) {
        TagStackNode *temp;

        temp = top;
        top = temp->next;
        delete temp;
    } else {
    throw StackException("StackException: Stack is empty can't pop.");
    }
}


Thanks for the tip let me see if that works thanks.
LiverEatnJohnson (23)
Thanks for the tip that worked now i just need to know what goes in to an StackException.h file I have no idea what to put in it.
LiverEatnJohnson (23)
any ideas would be a great help. Thanks.
LiverEatnJohnson (23)
ok that didnt work eather really i thought it did but now i am getting the same error that i was getting on the throw line on the line 6 of the above code I am just plain confused here is the source code for my current StackException.h file and the TagStack.cpp and TagStack.h

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/***********************************
 * Project:    XmlValidator
 * File:       TagStack.h
 * Author:     Jeremiah Johnson
 * Assignment: Stacks
 * Date:       November 3, 2011
 ***********************************/

#ifndef TAGSTACK_H
#define	TAGSTACK_H

#include <istream>
#include "Tag.h"
#include "TagStackNode.h"
#include "StackException.h"
#include <exception>

using namespace std;

class TagStack {
public:
    TagStack();
    
    ~TagStack();
    
    bool isEmpty();
    
    void push(Tag me) throw(StackException);
    
    void pop() throw(StackException);
    
    void get(Tag &me) throw(StackException);
    
private:
    TagStackNode *top;

};

#endif	/* TAGSTACK_H */

/******************************************** 
 * Project:     XmlValidator
 * File:        StackException.h
 * Author:      Jeremiah Johnson
 * Assignments: Stack
 * Date:        November 15, 2011
 ********************************************/

#ifndef STACKEXCEPTION_H
#define	STACKEXCEPTION_H

#include <exception>
#include <string>
#include <stdexcept>

using namespace std;

class StackException: public exception {
public:
    StackException() throw ();
    
    StackException(string explain) throw ();

    virtual const char* what() const throw ();

};

#endif	/* STACKEXCEPTION_H */

/***********************************
 * Project:    XmlValidator
 * File:       TagStack.cpp
 * Author:     Jeremiah Johnson
 * Assignment: Stacks
 * Date:       November 3, 2011
 ***********************************/

#include "TagStack.h"
#include "TagStackNode.h"
#include "Tag.h"
#include <string>
#include <istream>
#include <fstream>
#include "StackException.h"
#include <new>
#include <stdexcept>

using namespace std;

/**
 * Constructs an empty stack
 */
TagStack::TagStack() {
    top = NULL;
}

/**
 * Destroys the stack
 */
TagStack::~TagStack() {
    while (top != NULL) {
        pop();
    }
}

/**
 * Returns weather or not the stack is empty
 * @return bool, true if stack is empty
 */
bool TagStack::isEmpty() {
    return top == NULL;
}

/**
 * Passes the top tag from the stack
 * @param me, tag to be returned
 * @throws StackException
 */
void TagStack::get(Tag &me) throw (StackException) {
    StackException except;
    
    if (!isEmpty()) {
        me = top->tag;
    } else {
    throw except;
    }
}

/**
 * Takes the top tag off the stack
 * @throws StackException.
 */
void TagStack::pop() throw (StackException) {
    StackException except;
    
    if (!isEmpty()) {
        TagStackNode *temp;
        temp = top;
        top = temp->next;
        delete temp;
    } else {
        throw except;
    }
}

/**
 * Puts a new tag on top of the stack
 * @param me, tag to be put on top
 * @throws StackException                                                  
 */
void TagStack::push(Tag me) throw (StackException) {
    StackException except;
    
    try {
        TagStackNode *node = new TagStackNode;
        node->tag = me;
        node->next = top;
        top = node;
    } catch (StackException &e) {
        throw except;
    }
}


Any help would be great thanks in advance.
LiverEatnJohnson (23)
All working good now Source code is avalible upon request
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