polynomials using a linked list

[yodadbl07]

hey im trying to write a class of polynomials using a linked list. But I am getting an error at run time with my Polynomial* getNext() function. The error says access violation reading location. Im not sure what im doing wrong.

 #ifndef POLYNOMIAL_H
#define POLYNOMIAL_H
 
class Polynomial
{
public:
    Polynomial( ){}
    Polynomial(int theCoefficient);
    Polynomial(int theCoefficient, int thePower);
    Polynomial(Polynomial&);//copy constructor
    Polynomial* getNext( ) {return next;}
    void setNext(Polynomial* polyLoc) {next = polyLoc;}
    double evaluate(double value);
    Polynomial& operator =(Polynomial& rightSide);
    Polynomial operator +(Polynomial& polyObj);
    Polynomial operator -(Polynomial& polyObj);
    Polynomial operator *(Polynomial& polyObj);
    virtual ~Polynomial( );
private:
    int coefficient;
    int power;
    Polynomial* next;
    Polynomial* head;
};
#endif //POLYNOMIAL_H
 
 
//begin Polynomial.cpp 
 
#include <iostream>
#include <math.h>
#include "polynomial.h"
 
using namespace std;
 
Polynomial::Polynomial(int theCoefficient)
{
    head = new Polynomial;
    coefficient = theCoefficient;
    power = 0;
    next = new Polynomial;
    setNext(NULL);
}
 
Polynomial::Polynomial(int theCoefficient, int thePower)
{
    head = new Polynomial;
    coefficient = theCoefficient; 
    power = thePower;
    next = new Polynomial;
    setNext(NULL);
}
 
Polynomial::Polynomial(Polynomial& polyObj)
{/*not completed*/ }
 
 
double Polynomial::evaluate(double value)
{
    double total = 1;
    Polynomial* temp = head;
    while(temp->getNext() != NULL)
    {
        total = total + pow((coefficient*value), power);
        temp = temp->getNext();
    }
 
 
return total;
}
 
Polynomial& Polynomial::operator =(Polynomial& rightSide)
{
    power = rightSide.power;
    coefficient = rightSide.coefficient;
    next = rightSide.next;
 
    return *this;
}
 
Polynomial Polynomial::operator +(Polynomial& polyObj)
{
    Polynomial* temp = head;
    while(temp->getNext() != NULL)
    {
        if (power == polyObj.power)
            coefficient = coefficient + polyObj.coefficient;
        temp = temp->getNext();
    }
 
    return *this;    
}
 
Polynomial Polynomial::operator -(Polynomial& polyObj)
{
    Polynomial* temp = head;
    while(temp->getNext() != NULL)
    {
        if (power == polyObj.power)
            coefficient = coefficient - polyObj.coefficient;
        temp = temp->getNext();
    }
 
    return *this;    
}
 
Polynomial Polynomial::operator *(Polynomial& polyObj)
{
    Polynomial* temp = head;
    while(temp->getNext() != NULL)
    {
        coefficient = coefficient*polyObj.coefficient;
        power = power+polyObj.power;
        temp = temp->getNext();
    }
 
    return *this;    
}
 
 
Polynomial::~Polynomial( )
{
    Polynomial* temp = head;
 
    while(temp->getNext() != NULL)
    {
        temp = temp->getNext();
        delete head;
        head = temp;
    }
 
    delete head;
}

THanks

[AdrianH]

I would guess that it may have something to do with you not initialising your member variables. ;)


Adrian

[yodadbl07]

which ones are not initialized? dont my constructors take care of that?

thanks

[weaknessforcats]

This is C++, right? Then how come:

Polynomial* next;
Polynomial* head;

this is in your Polynomial class???

It looks like you are using as a node and then somehwere else you use next/head pointers to make a list, etc, etc...

Use a list:

list<Polynomial> thelist;
 

and remove all the linked list code from your class.

What you have here is spaghetti code. The polynomial and the linked list are interwoven and not separable. If you need a different type in the linked list, you have to recode the linked list again.


The list is already coded for you in the C++ Standard Library. It's a waste of time to recode linked lists over and over.

[AdrianH]

This is C++, right? Then how come:


this is in your Polynomial class???

It looks like you are using as a node and then somehwere else you use next/head pointers to make a list, etc, etc...

Use a list:

list<Polynomial> thelist;
 

and remove all the linked list code from your class.

What you have here is spaghetti code. The polynomial and the linked list are interwoven and not separable. If you need a different type in the linked list, you have to recode the linked list again.


The list is already coded for you in the C++ Standard Library. It's a waste of time to recode linked lists over and over.

That's true. I assumed it was done that way as part of the assignment. ;)


Adrian

[AdrianH]

which ones are not initialized? dont my constructors take care of that?

thanks

Only the ones that initialise them. And there is at least one that doesn't.


Adrian

[svlsr2000]

It would be great if you could post your other code as well. ie piece of code where your creating and using objects of your class. with just a brief look i found one mistake, which could be source of your problem

Polynomial::Polynomial(int theCoefficient, int thePower)
 
{
 
head = new Polynomial;
 
coefficient = theCoefficient; 
 
power = thePower;
 
next = new Polynomial; //ERROR 
 
setNext(NULL); //ERROR
 
}
 
 

Here your creating a new object and making next to point to it, but the very next statement your calling setNext with NULL as arguement. This would ground your next pointer, without even using it or freeing it.

The same is the case with other constructor too.

[AdrianH]

Only the ones that initialise them. And there is at least one that doesn't.


Adrian

Hint: look at line 7.


Adrian