I have a school project in which I am supposed to build a template class Vanzare meaning sale. I have 2 STL vectors, one for the cars that are in stock, and one for the cars that are sold, and 2 variables that count how many cars are in stock and how many cars are sold.
The class is supposed to have the -= operator overloaded, and it's supposed to sell a car, meaning deleting it from the stock vector (named stoc) and adding it to the sold vector (named vandut).
I also overloaded the += operator to add a car to stock.
The types of cars I have are all derived from the base class Masina, and some of them have extra fields.
The problem is that whenever I use += or -= ( or push_back() in general) for anything that has extra fields (compared to the base class), it breaks the previous elements from the vector. So I can't store any derived objects without loss of information.
I was also told that making a specialization of the whole class might help, but it didn't.
The template class starts around line 300 (I didn't know how to highlight it sorry). I am sorry if what I wrote wasn't clear, I am kinda new to all of this object oriented stuff. Thank you in advance!
Edit: I tried my best to slim the program down as much as I can, but it still has 250 lines of code. I also renamed (hopefully everything) to English. The field sh still gets lost when I add an object to the vector.
#include <iostream>
#include <string.h>
#include <vector>
#include <ctime>
using namespace std;
class Car
{
int capacity;
float length;
int price;
int year;
public:
int getYear();
void setPrice(int);
int getPrice();
Car();
~Car();
Car(int , float , int , int);
Car(const Car&);
friend istream& operator>>(istream& , Car&);
friend ostream& operator<<(ostream& , Car&);
friend class VAN;
};
int Car::getYear()
{
return year;
}
int Car::getPrice()
{
return price;
}
void Car::setPrice(int p)
{
price = p;
}
ostream& operator<<(ostream& out , Car& m)
{
out<<"capacity: "<<m.capacity<<"\nlength: "<<m.length<<"\nprice: "<<m.price<<"\nYear: "<<m.year;
return out;
}
istream& operator>>(istream& in , Car& m)
{
cout<<"capacity: ";
in>>m.capacity;
cout<<"length: ";
in>>m.length;
cout<<"price: ";
in>>m.price;
cout<<"Year: ";
in>>m.year;
return in;
}
Car::Car()
{
capacity = 0;
length = 0;
year = 0;
price = 0;
}
Car::Car(int lit , float lun , int an , int pre)
{
capacity = lit;
length = lun;
year = an;
price = pre;
}
Car::Car(const Car& m)
{
capacity = m.capacity;
length = m.length;
year = m.year;
price = m.price;
}
Car::~Car()
{
capacity = 0;
year = 0;
length = 0;
price = 0;
}
class VAN:public Car
{
int sh;
public:
void setSH(int);
int isSH();
VAN();
~VAN();
VAN(int , float , int , int , int);
VAN(const VAN&);
friend istream& operator>>(istream& , VAN&);
friend ostream& operator<<(ostream& , VAN&);
};
void VAN::setSH(int s)
{
if(s)
sh = 1;
else
sh = 0;
}
int VAN::isSH()
{
return sh;
}
ostream& operator<<(ostream& out , VAN& m)
{
out<<(Car&)m;
out<<endl<<"Second hand: "<<m.sh;
return out;
}
istream& operator>>(istream& in , VAN& m)
{
in>>(Car&)m;
cout<<"Second Hand: ";
int x;
in>>x;
if(x)
m.sh = 1;
return in;
}
VAN::VAN():Car()
{
;
}
VAN::~VAN()
{
;
}
VAN::VAN(int a , float b , int c, int d , int s):Car(a , b, c , d)
{
if(s)
sh = 1;
}
VAN::VAN(const VAN& m):Car(m)
{
;
}
template <class T>
class Sale
{
vector<T> stock;
vector<T> sold;
int nrSold;
int nrStock;
public:
Sale();
Sale<T>& operator += (T&);
template <class U>
friend ostream& operator<<(ostream& , Sale<U>& );
Sale<T>& operator -= (int);
};
template <class T> Sale<T>& Sale<T>::operator -= (int i)
{
nrStock--;
nrSold++;
sold.push_back(stock[i]);
stock.erase(stock.begin()+i);
time_t now = time(0);
tm *ltm = localtime(&now);
if(ltm->tm_mon == 5 || ltm->tm_mon == 6 || ltm->tm_mon == 7)
{
(sold[nrSold-1]).setPret((sold[nrSold-1].getPret()/10)*9);
}
return *this;
}
template <class T> Sale<T>::Sale()
{
nrSold = 0;
nrStock = 0;
}
template <class T> ostream& operator<<(ostream& out, Sale<T>& v)
{
out<<"\nWhat we have in stock:\n\n";
for(int i = 0; i < v.nrStock ; i++)
{
out<<v.stock[i]<<endl;
}
cout<<"\nWhat we sold:\n\n";
for(int i = 0; i < v.nrSold ; i++)
{
out<<v.sold[i]<<endl;
}
return out;
}
template <class T> Sale<T>& Sale<T>::operator += (T& t)
{
nrStock ++;
stock.push_back(t);
return *this;
}
int main()
{
VAN x;
cin>>x;
cout<<x;
Sale<VAN> v;
v += x;
v += x;
cout<<v;
}
There are logic errors in ALL of your VAN constructors:
in the default constructor, the sh member is not being initialized at all, so it's value is indeterminate.
In the conversion constructor, the sh member is not being initialized if the s parameter is 0, so it's value is indeterminate in that case. Your operator>> has a similar logic error that it is not updating the m.sh member if the input is 0.
in the copy constructor, the sh member is not being copied from m at all, so it's value is indeterminate.
When you push a VAN object into your vector, a copy of the object is made. And if the vector needs to reallocate its array to grow its capacity, new copies of existing elements are made. Since your copy constructor is broken, that is why you are losing your sh values.
Your VAN constructors need to look more like this instead 1:
VAN::VAN() : Car(), sh(0)
{
}
VAN::VAN(int a , float b , int c, int d , int s) : Car(a , b, c , d)
{
sh = (s != 0);
}
VAN::VAN(const VAN& m) : Car(m), sh(m.sh)
{
}
1: in the case of the copy constructor, you can actually omit it completely, and let the compiler auto-generate a suitable copy constructor for you.
And your operator>> needs to look more like this instead:
istream& operator>>(istream& in , VAN& m)
{
in >> (Car&)m;
cout << "Second Hand: ";
int x;
in >> x;
m.sh = (x != 0);
return in;
}
On a couple of side notes:
your sh member is declared as an int, but it clearly should be a bool instead.
VAN does not need to, and should not, be declared as a friend of Car. If VAN needs direct access to Car's private members, they should be declared as protected instead.
Related
This is part of my polynomial.cpp to get terms by overloading istream
void Newterm(float coef, int deg) {
if (terms == capacity) {
capacity *= 2;
Term* tmp = new Term[capacity];
copy(termArray, termArray + terms, tmp);
termArray = tmp;
delete[] tmp;
}
termArray[terms].degree = deg;
termArray[terms++].coef = coef;
}
friend istream& operator >> (istream& is, Polynomial& pl) {
cout << "number of terms : ";
int t; is >> t;
cout << endl;
float coeff;
int degree;
for (int i = 0; i < t;i++) {
cout << i + 1 << "'s term: ";
is >> coeff >> degree;
pl.Newterm(coeff, degree);
}
return is;
};
of course, i tried to figure out whaaat made this result..
tried:
removing 'for' loop
this actually worked.. but it only works when terms=1
firstly creating term and input data
Newterm(0,0);
is>>pl.termArray[i].coef>>pl.termArray[i].degree;
it couldn't fix anything...
so i think it has to do with loops..
but whyyyy?
Using std::vector instead of doing your own memory managment
(why reinvent the wheel if there is a tested solution in the standard library)
#include <iostream>
#include <vector>
struct Term final
{
Term() = default;
~Term() = default;
Term(int d, double c) :
degree{ d },
coef{ c }
{
}
int degree{ 0 };
double coef{ 1.0 };
};
class Polynomial final
{
public:
Polynomial() = default;
~Polynomial() = default;
explicit Polynomial(const std::initializer_list<Term> terms) :
m_terms{ terms }
{
}
void add(const Term& term)
{
m_terms.push_back(term);
}
private:
std::vector<Term> m_terms;
};
std::istream& operator>>(std::istream& is, Polynomial& polynomial)
{
std::size_t n{ 0 }; // indices are not ints the can't be < 0
is >> n;
for (std::size_t i = 0; i < n; ++i)
{
Term term{};
is >> term.coef;
is >> term.degree;
polynomial.add(term);
}
return is;
}
int main()
{
// to show you that std::vector can handle all the memory managment for you
// constructor with an initializer list that adds 3 terms
// that's also why the Term has a constructor, it is to make it work with
// initializer list
Polynomial p{ { 1,2.0 }, { 2,4.0 }, { 1,-1.0 } };
}
I'm a CS student taking an OOP course and I don't know how to fix this issue. I understand that when the += operator tries to add the first element into the array, 'this' is nullptr and an exception is thrown, but I don't know how to fix it.
Shopping list header looks like this:
#include "Groceries.h"
class ShoppingList{
Groceries* list;
int size = 0, capacity = 2;
public:
//methods
ShoppingList& operator+=( const Groceries& c);
operator+= looks like:
ShoppingList& ShoppingList::operator+=( const Groceries& c) {
if (size == capacity) {
Groceries* l1 = new Groceries[capacity * 2];
l1 = list;
list = l1;
capacity *= 2;
}
list[size++]=c;//here is the exception
return *this;
}
Groceries header looks like:
#include <string>
#include <iostream>
class Groceries {
std::string product;
int quantity;
public:
Groceries() : product("empty"), quantity(0) {};
Groceries(std::string s, int x) : product(s), quantity(x) {};
Groceries(const Groceries& c);
~Groceries() {};
std::string product();
int quantity();
void Print();
};
and main HAS TO look like
int main()
{
ShoppingList L;
(L += Groceries("bread", 5)) += Groceries("cheese", 2);
L.Print();
//...
}
These statements in the body of the operator
l1 = list;
list = l1;
do not make sense. After the first assignment statement there is a memory leak because the address of the allocated memory is lost. In fact these two statements are equivalent to this statement
list = list;
including the side effect of the overwriting the pointer l1.
The operator can be defined the following way
ShoppingList& ShoppingList::operator+=( const Groceries& c) {
if (size == capacity) {
Groceries* l1 = new Groceries[capacity * 2];
std::copy( list, list + size, l1 );
delete [] list;
list = l1;
capacity *= 2;
}
list[size++]=c;//here is the exception
return *this;
}
Pay attention to that you are using the same identifiers product and quantity to declare different entities
class Groceries {
std::string product;
int quantity;
public:
//...
std::string product();
int quantity();
//...
Here is a demonstrative program based on your code.
#include <iostream>
#include <string>
#include <iterator>
#include <algorithm>
class Groceries {
std::string product;
int quantity;
public:
Groceries() : product("empty"), quantity(0) {};
Groceries(std::string s, int x) : product(s), quantity(x) {};
Groceries(const Groceries& c);
~Groceries() {};
// std::string product();
// int quantity();
void Print();
friend std::ostream & operator <<( std::ostream &os, const Groceries &g )
{
return os << g.product << ": " << g.quantity;
}
};
class ShoppingList{
Groceries* list;
int size = 0, capacity = 2;
public:
//methods
ShoppingList& operator+=( const Groceries& c);
ShoppingList() : list( new Groceries[2]() ) {}
~ShoppingList() { delete [] list; }
friend std::ostream & operator <<( std::ostream &os, const ShoppingList &sl )
{
std::copy( sl.list, sl.list + sl.size,
std::ostream_iterator<Groceries>( os, " " ) );
return os;
}
};
ShoppingList& ShoppingList::operator+=( const Groceries& c) {
if (size == capacity) {
Groceries* l1 = new Groceries[capacity * 2];
std::copy( list, list + size, l1 );
delete [] list;
list = l1;
capacity *= 2;
}
list[size++]=c;//here is the exception
return *this;
}
int main()
{
ShoppingList L;
(L += Groceries("bread", 5)) += Groceries("cheese", 2);
std::cout << L << '\n';
return 0;
}
The program output is
bread: 5 cheese: 2
I got this project where I have to overload the i/o operators to read and write polynomials. Unfortunately I can't seem to get it to work.
I have the header file:
#ifndef POLYNOMIAL_H
#define POLYNOMIAL_H
#include <iostream>
using namespace std;
class Polynomial
{
public:
Polynomial();
Polynomial(int degree, double coef[]);
int degree;
double coef[ ];
friend istream& operator>>(istream&,Polynomial& );
friend ostream& operator<<(ostream&,const Polynomial&);
virtual ~Polynomial();
};
#endif // POLYNOMIAL_H
and the cpp file:
#include "Polynomial.h"
#include<iostream>
#include<string>
using namespace std;
Polynomial::Polynomial()
{
//ctor
}
Polynomial::~Polynomial()
{
//dtor
}
Polynomial::Polynomial(int d, double c[])
{
degree = d;
double coef [degree+1];
for(int i = 0; i < d+1; i++)
{
coef[i] = c[i];
}
}
istream& operator>>(istream& x, const Polynomial& p)
{
cout<<"The degree: ";
x>>p.degree;
for(int i = 0; i < p.degree+1; i++)
{
cout<<"The coefficient of X^"<<i<<"=";
x>>p.coef[i];
}
return x;
}
ostream& operator<<(ostream& out, const Polynomial& p)
{
out << p.coef[0];
for (int i = 1; i < p.degree; i++)
{
out << p.coef[i];
out << "*X^";
out << i;
}
return out;
}
In the name I am trying to read a polynomial and then to write another one:
#include <iostream>
using namespace std;
#include "Polynomial.h"
int main()
{
Polynomial p1();
cin >> p1;
int degree = 2;
double coef [3];
coef[0]=1;
coef[1]=2;
coef[3]=3;
Polynomial p(degree, coef);
cout<<p;
return 0;
}
When I run the program it just freezes and I can't seem to find the error.
Any ideas?
Polynomial::Polynomial(int d, double c[])
{
degree = d;
double coef [degree+1];
for(int i = 0; i < d+1; i++)
{
coef[i] = c[i];
}
}
Here, you create local array coef (with non-standard C++ btw) and then assign to it. Your member coeff is not initialized to anything meanigfull (and makes little sense the way it is right now in the first place).
Instead of double coef[] you should use std::vector like this:
struct polynomial {
std::vector<double> coef;
// No need for member varaible degree, vector knows its lengths
polynomial (const std::vector<double> &coeffs) : coef (coeffs) {}
};
And then define all other constructors you need to do something meaningful. Alternatively, you can leave out constructors entirely and directly assign the coefficient vector. Then you can for example functions like
int degree (const polynomial &p) {
return p.coef.size() - 1;
}
or
std::ostream &operator << (std::ostream &out, const polynomial p) {
if (p.coef.size() == 0) {
out << "0\n";
return out;
}
out << p.coeff[0];
for (int i = 1; i < p.coef.size(); ++i)
out << " + " << p.coef[i] << "*X^i";
out << "\n";
return out;
}
(1)
double coef[];
This is non-standard approach to have un-sized/dynamic-sized array on stack. You better give the array some size, OR make it a pointer and allocate memory yourself; OR use vector<double>
(2)
You are creating a local variable in constructor, which will hide the member-variable in class. If you are using pointer approach, you need to allocate it properly here in constructor. With either approach, you should initialize the (member) variable coef with zeros, ideally.
(3)
Polynomial p1();
This effectively declares a function named p1 which would return a Polynomial and not a variable of tyoe Polynomial. You may want to use:
Polynomial p1;
i am required to read a file with data of this format (Date, ID, Activity, Qty, Price) in the main test class. I'm supposed to read and store the "Date" values into int day,month,year of type Date, followed by "ID, Activity, Qty, Price" of stock class.
02/08/2011, ABC, BUY, 100, 20.00
05/08/2011, ABC, BUY, 20, 24.00
06/08/2011, ABC, BUY, 200, 36.00
i stored the values accordingly to Stock() constructor and store all data via push_back() in my own "Vector" class. what must i add/ edit so that i can retrieve the rows of data in Vector and get(Date, ID, Activity, Qty, Price) and make calculations for qty and price.
#include"Vector.h"
#include"Date.h"
#include"Stock.h"
#include<iomanip>
#include<fstream>
#include<iostream>
#include<string>
using namespace std;
int main(){
string stockcode;
string act;
int qty;
double p;
int d,m,y;
char x;
//declare file stream variables
ifstream inFile;
ofstream outFile;
//open the file
inFile.open("share-data.txt");
//code for data manipulation
cout << fixed << showpoint << setprecision(2);
while(!inFile.eof()){
inFile>> d >> x >> m >> x >> y >> x
>> stockcode >> act >> qty >> x >> p;
Stock s1(d,m,y,stockcode,act,qty,p);
stockcode = stockcode.substr(0, stockcode.length()-1);
act = act.substr(0, act.length()-1);
Stock s1(d,m,y,stockcode,act,qty,p);
stockList.push_back(s1);
}
inFile.close();
system("PAUSE");
return 0;
}
i have my own Vector class which is needed for this assignment because i am not allowed to use #include default vector
#include<iostream>
using namespace std;
template <class T>
class Vector
{
public:
Vector(); // default constructor
virtual ~Vector() {}; //destructor
bool isEmpty() const;
bool isFull() const;
void print() const;
void push_back(T);
T pop_back();
T at(int i);
int Size();
//Vector<T> operator +=(T);
private:
int size;
T list[100];
};
template <class T>
Vector<T>::Vector()
{
size = 0;
}
template <class T>
Vector<T> Vector<T>::operator +=(T i)
{
this->push_back(i);
return *this;
}
template <class T>
bool Vector<T>::isEmpty() const
{
return (size == 0);
}
template <class T>
bool Vector<T>::isFull() const
{
return (size == 100);
}
template <class T>
void Vector<T>::push_back(T x)
{
list[size] = x;
size++;
}
template <class T>
T Vector<T>::operator[](T i)
{
return list[i];
}
template <class T>
T Vector<T>::at(int i)
{
if(i<size)
return list[i];
throw 10;
}
template <class T>
T Vector<T>::pop_back()
{
T y;
size--;
y= list[size];
return y;
}
template <class T>
void Vector<T>::print() const
{
for (int i = 0; i < size; i++)
cout << list[i] << " ";
cout << endl;
}
template <class T>
int Vector<T>::Size()
{
return size;
}
and here's my Stock class
#include"Date.h"
Stock::Stock()
{
stockID="";
act="";
qty=0;
price=0.0;
}
Stock::Stock(int d, int m , int y, string id,string a, int q, double p)
:date(d,m,y){
stockID = id;
act = a;
qty = q;
price = p;
}
.
.
.
use string::substr
act = act.substr(0, act.length()-1);
You can do the same for the other string variables.
I'm having the above issue when I attempt to set a string (stored in a class) equal to another string. I have combed and combed trying to find if I did not initialize any variables, but I can't find such a situation. In debug mod, I get the above error. In release mode it hangs and Win7 looks for a problem, no major abort or retry window. Here's the relevant code, there is another header file with my main program if you feel it should be included, I'll include the line that causes errors. Language is C++ obviously.
//Error occurs in this area:
Car one;
one = two;
one.addExtra ("Windows");
log << "Car one: " << one << endl;
two = Car(one); // call copy constructor.
//I realize when I call the first one = two, there are no extras
//stored int Car one, which is what differs between the two. Remaining
//code. Extras header:
#include <iostream>
#include <string>
#include <string.h>
using namespace std;
class Extras
{
public:
friend class Car;
friend int main();
friend ostream& operator << (ostream& os, const Extras& in);
friend class CarLot;
Extras(const Extras& other);
Extras& operator=(Extras &rhs);
Extras(string in);
Extras();
~Extras();
void modify_ext(string* in);
//string ex_list;
private:
int place;
string *ex_list;
};
//Extras.cpp:
#include "Extras.h"
Extras::Extras(string in)
{
delete ex_list;
ex_list = new string;
place = 0;
//ex_list = new string[4];
(*ex_list) = in;
place++;
}
Extras::Extras()
{
//ex_list = new string[4];
place = 0;
//for(int i = 0; i < 4; i++)
ex_list = new string;
*ex_list = "0";
}
//Overloaded << operator for Extras class to
//easily output array contents
ostream& operator<< (ostream& os, Extras const &in)
{
os << *(in.ex_list);
return os;
}
Extras& Extras::operator=(Extras &rhs)
{
if(this != &rhs)
{
//string temp;
//temp = rhs.ex_list;
modify_ext(rhs.ex_list);
cout << endl << endl << ex_list << endl << endl;
place = rhs.place;
}
return *this;
}
Extras::Extras(const Extras& other) : place(other.place), ex_list(other.ex_list)
{
//for(int i = 0; i < 4; i++)
//ex_list = other.ex_list;
}
void Extras::modify_ext(string* in)
{
delete ex_list;
ex_list = new string;
(*ex_list).resize((*in).size());
for(unsigned int i = 0; i < (*in).size(); i++)
ex_list[i] = in[i];
}
Extras::~Extras()
{
delete ex_list;
place = 0;
}
//Car Header:
#include "Extras.h"
class Car
{
public:
friend class Extras;
friend Extras& Extras::operator=(Extras &rhs);
friend int main();
friend ostream& operator<< (ostream& os, const Car& in);
friend class CarLot;
friend void add_extra();
~Car();
Car();
Car(Car& other);
Car(string in_name, int in_year, string in_color, float in_cost);
Car& operator=(Car const &rhs);
void edit_extr(int in);
void addExtra(string in);
private:
string name, color;
int year, extr_num;
float cost;
Extras *extr;
};
//Car.cpp:
#include "car.h"
//Constructor
Car::Car(string in_name, int in_year, string in_color, float in_cost)
{
name = in_name;
color = in_color;
year = in_year;
cost = in_cost;
extr = new Extras[3];
extr_num = 0;
}
//Overloaded = operator
Car& Car::operator=(Car const &rhs)
{
if(this != &rhs)
{
name = rhs.name;
color = rhs.color;
year = rhs.year;
cost = rhs.cost;
//delete extr;
extr = rhs.extr;
extr_num = rhs.extr_num;
}
return *this;
}
//Default Constructor
Car::Car()
{
name = "TEMP";
color = "BLUE";
year = 0;
cost = 0;
extr = new Extras[3];
extr_num = 0;
}
//Destructor
Car::~Car()
{
delete extr;
extr = NULL;
}
//Copy constructor
Car::Car(Car& other) : name(other.name), color(other.color), year(other.year),
cost(other.cost), extr_num(other.extr_num)
{
//delete extr;
for(int i = 0; i < extr_num; i++)
{
extr[i].modify_ext(other.extr[i].ex_list);
extr[i].place = other.extr[i].place;
}
}
//Overloaded << operator for Car class
ostream& operator<< (ostream& os, const Car& in)
{
os.precision(2);
os << in.name << ", " << in.year << ", "
<< in.color << ", $"<< in.cost << ", ";
os << "extras include: ";
for(int k = 0; k < in.extr_num; k++)
{
os << in.extr[k] << ", ";
}
os << endl;
return os;
}
void Car::edit_extr(int in)
{
Extras* temp;
temp = new Extras[in];
for(int i = 0; i < in; i++)
temp[i] = extr[i];
extr_num = in;
delete extr;
extr = temp;
}
void Car::addExtra(string in)
{
if(extr_num == 3)
{
//log << "Car has too many extras.";
return;
}
//edit_extr(extr_num + 1);
*(extr[extr_num].ex_list) = in;
extr[extr_num].place++;
extr_num++;
}
As I said, I have one more additional header, another class, and a main program if those need to be included, but I figured this was more than enough code (sorry!) for anyone to look through. Any help would be incredibly appreciated.
What I'm seeing that's broken:
two = Car(one); // call copy constructor.
No, it creates a temporary object with the copy constructor, passes this to operator=() on two, then destroys the temporary.
Extras& operator=(Extras &rhs);
should be:
Extras& operator=(const Extras &rhs);
Extras::Extras(string in)
{
delete ex_list;
ex_list = new string;
place = 0;
//ex_list = new string[4];
(*ex_list) = in;
place++;
}
Better:
Extras::Extras(const string& in): place(1), ex_list(new string(in))
{
}
Extras::Extras(const Extras& other) : place(other.place), ex_list(other.ex_list)
{
//for(int i = 0; i < 4; i++)
//ex_list = other.ex_list;
}
Looking at your default constructor, it's clear that the Extras object owns the string in ex_list. However, this copy constructor claims ownership of the original object's ex_list. It should make its own copy:
Extras::Extras(const Extras& other): place(other.place),
ex_list(new string(other.ex_list))
{
}
void Extras::modify_ext(string* in)
{
delete ex_list;
ex_list = new string;
(*ex_list).resize((*in).size());
for(unsigned int i = 0; i < (*in).size(); i++)
ex_list[i] = in[i];
}
You're copying the string. All you need is:
void Extras::modify_ext(const string* in)
{
*ex_list = *in;
}
Moving on to the Car...
friend class Extras;
friend Extras& Extras::operator=(Extras &rhs);
friend int main();
friend ostream& operator<< (ostream& os, const Car& in);
friend class CarLot;
friend void add_extra();
You should consider refactoring the code to get rid of these.
Car(Car& other);
Car(string in_name, int in_year, string in_color, float in_cost);
Should be:
Car(const Car& other);
Car(const string& in_name, int in_year, const string& in_color, float in_cost);
References are your friends when passing objects to functions.
I'm going to stop here.
In your constructor you are deleting ex_list. It hasn't even been allocated yet, so this is wrong. Remove that and do this instead when allocating your new string:
ex_list = new string(in);
This way you use the string copy constructor. You can get rid of the rest of whatever you were trying to do below in the constructor since this will do it for you.
Edit:
Actually, there are a ton of problems all throughout this code. Is there any reason you want your string to be a pointer internally? You aren't using pointers correctly in a bunch of different places. I only noticed the first one as I scrolled down.
The allocator in debug builds with VC++ uses some magic values to fill allocated areas. In particular, 0xCC is memory that had been allocated but it now freed. So the address 0xCCCCCCD0, looks suspiciously like a small offset (e.g., to a struct or class member) from a pointer in memory that was freed. Given that, Mark Loeser's answer looks promising.