Question

The following program contains the definition of a class called List, a class called Date and a main program. Create a template out of the List class so that it can contain not just integers which is how it is now, but any data type, including user defined data types, such as objects of Date class. The main program is given so that you will know what to test your template with. It first creates a List of integers and displays them and then creates a List of Dates and displays them. From this, you can see how a container class such as List can be made into a template that can store any data type.

Main Program:

#include <iostream>

#include <conio.h>

using namespace std;

class List //contains a series of integers using dynamic memory with flexible size,

known as a container class

{

private:

int size; //number of elements

int *ptr; //points to first element

public:

List(int size = 0, int* ptr = 0); //default size is 0 List(const List& l);

List(const List& l); //copy constructor - used to create and at once

initialize a List object

int get_size() const;

const List& operator=(const List& l); //overloaded assignment operator

int& operator[](int index); //returns a reference to int so it can be

assigned to(used as lvalue)

const int operator[](int index) const; //returns list member at specified

index(a rvalue)

~List(); //destructor frees allocated dynamic memory

};

class Date {

friend ostream& operator<<(ostream& out, const Date& date); //a non-member

function is used to display because

friend istream& operator>>(istream& in, Date& date); //a non-member function

is used to display because

private:

int day, month, year;

public:

Date(int = 1, int = 1, int = 1900);

void set(int = 1, int = 1, int = 1900);

void get();

void print() const;

bool operator==(const Date &) const;

};

Date::Date(int d, int m, int y)

{

set(d, m, y);

}

void Date::set(int d, int m, int y)

{

if (d >= 1 && d <= 31)

day = d;

else

{

std::cout << "\ninvalid day: " << d;

std::cout << "\nProgram ending. . .";

system("pause");

exit(1);

}

if (m >= 1 && m <= 12)

month = m;

else

{

std::cout << "\ninvalid month: " << m;

std::cout << "\nProgram ending. . .";

system("pause");

exit(1);

}

if (y >= 1900 && y <= 3000)

year = y;

else

{

std::cout << "\ninvalid year: " << y;

std::cout << "\nProgram ending. . .";

system("pause");

exit(1);

}

}

void Date::get()

{

char ch;

std::cout << "Enter date in month/day/year format: ";

cin >> month >> ch >> day >> ch >> year;

}

ostream& operator<<(ostream& out, const Date& date) //a non-member function is used

to display because

{

out << date.month << '/' << date.day << '/' << date.year;

return out;

}

istream& operator>>(istream& in, Date& date) //a non-member function is used to

display because

{

in >> date.month >> date.day >> date.year;

return in;

}

bool Date::operator==(const Date &d) const

{

return day == d.day && month == d.month && year == d.year;

}

List::List(int s, int* ptr) : size(s), ptr(new int[s])

{

} //initialization being done by the member initializer; alternatively we could

write them in the body like in set_size

List::List(const List& l) : size(l.size) //copy constructor used to initialize a

List object using an existing List object

{ //this creates the new object with l.size elements

ptr = new int[size];

for (int i = 0; i < size; i++) //now copy elements

ptr[i] = l.ptr[i];

}

int List::get_size() const

{

return size;

}

int& List::operator[](int index) //returns a reference to object so it can be

assigned to

{

return ptr[index];

}

const int List::operator[](int index) const //returns list member at specified

index

{

return ptr[index];

}

List::~List()

{

delete[] ptr;

}

int main()

{

List<int>numbers(10);

for (int i = 0; i < 10; i++)

{

numbers[i] = i + 1;

cout << numbers[i] << ' ';

}

List<Date>dates(3);

dates[0].set(1, 12, 2016);

dates[1].set(2, 12, 2016);

dates[2].set(3, 12, 2016);

for (int i = 0; i < 3; i++)

cout << endl << dates[i];

cout << "\nPress any key to continue.";

_getch();

}

Answer 1

If you have any doubts, please give me comment...

#include <iostream>

#include <cstdlib>

// #include <conio.h>

using namespace std;

template<class T>

class List //contains a series of integers using dynamic memory with flexible size, known as a container class

{

private:

    int size; //number of elements

    T *ptr; //points to first element

public:

    List(int size = 0, T *ptr = 0); //default size is 0 List(const List& l);

    List(const List &l);              //copy constructor - used to create and at once     initialize a List object

    int get_size() const;

    const List &operator=(const List<T> &l); //overloaded assignment operator

    T &operator[](int index);           //returns a reference to int so it can be     assigned to(used as lvalue)

    const T operator[](int index) const; //returns list member at specified index(a rvalue)

    ~List<T>(); //destructor frees allocated dynamic memory

};

class Date

{

    friend ostream &operator<<(ostream &out, const Date &date); //a non-member     function is used to display because

    friend istream &operator>>(istream &in, Date &date); //a non-member function is used to display because

        private :

        int day,

        month,

        year;

public:

    Date(int = 1, int = 1, int = 1900);

    void set(int = 1, int = 1, int = 1900);

    void get();

    void print() const;

    bool operator==(const Date &) const;

};

Date::Date(int d, int m, int y)

{

    set(d, m, y);

}

void Date::set(int d, int m, int y)

{

    if (d >= 1 && d <= 31)

        day = d;

    else

    {

        std::cout << "\ninvalid day: " << d;

        std::cout << "\nProgram ending. . .";

        system("pause");

        exit(1);

    }

    if (m >= 1 && m <= 12)

        month = m;

    else

    {

        std::cout << "\ninvalid month: " << m;

        std::cout << "\nProgram ending. . .";

        system("pause");

        exit(1);

    }

    if (y >= 1900 && y <= 3000)

        year = y;

    else

    {

        std::cout << "\ninvalid year: " << y;

        std::cout << "\nProgram ending. . .";

        system("pause");

        exit(1);

    }

}

void Date::get()

{

    char ch;

    std::cout << "Enter date in month/day/year format: ";

    cin >> month >> ch >> day >> ch >> year;

}

ostream &operator<<(ostream &out, const Date &date) //a non-member function is used    to display because

{

    out << date.month << '/' << date.day << '/' << date.year;

    return out;

}

istream &operator>>(istream &in, Date &date) //a non-member function is used to     display because

{

    in >> date.month >> date.day >> date.year;

    return in;

}

bool Date::operator==(const Date &d) const

{

    return day == d.day && month == d.month && year == d.year;

}

template<class T>

List<T>::List(int s, T *ptr) : size(s), ptr(new T[s])

{

} //initialization being done by the member initializer; alternatively we could write them in the body like in set_size

template<class T>

List<T>::List(const List<T> &l) : size(l.size) //copy constructor used to initialize a List object using an existing List object

{ //this creates the new object with l.size elements

    ptr = new T[size];

    for (int i = 0; i < size; i++) //now copy elements

        ptr[i] = l.ptr[i];

}

template<class T>

int List<T>::get_size() const

{

    return size;

}

template<class T>

T &List<T>::operator[](int index) //returns a reference to object so it can be assigned to

{

    return ptr[index];

}

template<class T>

const T List<T>::operator[](int index) const //returns list member at specified index

{

    return ptr[index];

}

template<class T>

List<T>::~List<T>()

{

    delete[] ptr;

}

int main()

{

    List<int> numbers(10);

    for (int i = 0; i < 10; i++)

    {

        numbers[i] = i + 1;

        cout << numbers[i] << ' ';

    }

    List<Date> dates(3);

    dates[0].set(1, 12, 2016);

    dates[1].set(2, 12, 2016);

    dates[2].set(3, 12, 2016);

    for (int i = 0; i < 3; i++)

        cout << endl << dates[i];

    cout << "\nPress any key to continue.";

    // _getch();

}