Category:Architecture/Development/CPP

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C++

IDE/Compilation

IDE

In AptanaStudio3, add the following repository to support C/C++: 

http://download.eclipse.org/tools/cdt/releases/helios

Compilation

Example (both below sources are identical):

Source1.cpp Source2.cpp 
#include <iostream>

int main()
{
  std::cout << "Hello world" << std::endl;
  return 0;
}

#include <iostream>

using namespace std;

int main()
{
  cout << "Hello world" << endl;
  return 0;
}

Let's compile: 

g++ -Wall -o main source1.cpp

And run: 

$ ./main
Hello world
Info.png
Note
If you have several *.cpp source files, all you need to do is to list them in the command, as follows: g++ -Wall -o main source1.cpp source2.cpp source3.cpp

Variables & references

Source Output 
#include <iostream>
#include <string>

using namespace std;

int main()
{
  int age(37);
  string name("Alice Shaw");
  double const pi(3.14159);  // Constant. You can't modify it.

  cout << "Hello " << name << ". You are " << age << " years old." << endl;
  return 0;
}

Hello Alice Shaw. You are 37 years old.

In C++, you can define references as follows:

Source Output 
#include <iostream>
#include <string>

using namespace std;

int main()
{
  int num(16);
  int& refnum1(num);
  int& refnum2(num);
  string name("Alice Shaw");
  string &refname(name);

  cout << "Num: " << num << endl;
  cout << "Ref Num 1: " << refnum1 << endl;
  cout << "Ref Num 2: " << refnum2 << endl;
  cout << "Name: " << name << endl;
  cout << "Ref name: " << refname << endl;

  return 0;
}

$ ./main 
Num: 16
Ref Num 1: 16
Ref Num 2: 16
Name: Alice Shaw
Ref name: Alice Shaw

Below is a more concrete example:

Source Run 
#include <iostream>
using namespace std;

void swap(int &a, int &b)
{
  int temp(a);
  a = b;
  b = temp;
}

int main() {
  int a(2), b(4);
  cout << "a=" << a << ", b=" << b << endl;
  swap(a, b);
  cout << "a=" << a << ", b=" << b << endl;
  return 0;
}

$ ./main
a=2, b=4
a=4, b=2

Arrays

Static size

Static size arrays work the same way as for C:

Source Run 
#include <iostream>
using namespace std;

double avg(double scores[], int len);

int main() {
  int const len(5);
  double scores[len];

  scores[0] = 13.2;
  scores[1] = 10.5;
  scores[2] = 15;
  scores[3] = 17.5;
  scores[4] = 12.8;

  cout << "Average: " << avg(scores, len) << endl;

  return 0;
}

double avg(double scores[], int len)
{
  double avg(0);
  int i(0);

  for(i=0; i<len; i++)
    avg += scores[i];
  avg /= len;
  return avg;
}

$ ./main
Average: 13.8

Dynamic size

To use a dynamic size array, first include the vector header: 

#include <vector>

Then do as follows: 

// Array of integers, size of 5, filled with 3
vector<int> tab(5, 3);

// Array of strings, size of 5, filled with "hello" 
vector<string> tab(5, "hello");

// Array of double, with no size specified and no default value
vector<double> tab;

To add and delete cells, respectively use array_name.push_back(val) and array_name.pop_back() as follows:

Source Output
main.h 
#ifndef DEF_MAIN
#define DEF_MAIN

#include <vector>
void tabinfo(std::vector<double> const &tab);

#endif
main.cpp 
#include <iostream>
#include <vector>
#include "main.h"
using namespace std;

int main() {
  vector<double> scores(5,0);
  int i(0);

  scores[0] = 13.2;
  scores[1] = 10.5;
  scores[2] = 15;
  scores[3] = 17.5;
  scores[4] = 12.8;
  tabinfo(scores);

  scores.push_back(12.3);
  tabinfo(scores);

  for(i=0; i<4; i++) {
    scores.pop_back();
    tabinfo(scores);
  }

  return 0;
}

void tabinfo(vector<double> const &tab)
{
  int i(0);

  cout << "Size: " << tab.size() << ", Items:";
  for (i=0; i<tab.size(); i++)
    cout << " " <<  tab[i];
  cout << endl;
}

Size: 5, Items: 13.2 10.5 15 17.5 12.8
Size: 6, Items: 13.2 10.5 15 17.5 12.8 12.3
Size: 5, Items: 13.2 10.5 15 17.5 12.8
Size: 4, Items: 13.2 10.5 15 17.5
Size: 3, Items: 13.2 10.5 15
Size: 2, Items: 13.2 10.5

Multi-dimensional arrays

Source Output
main.h 
#ifndef DEF_MAIN
#define DEF_MAIN

#include <vector>
void showtab(std::vector<std::vector<int>> const &tab);

#endif
main.cpp 
#include <iostream>
#include <vector>
#include "main.h"
using namespace std;

int main() {
  vector<vector<int>> tab;

  // 1st row of size 5 filled with 1
  tab.push_back(vector<int>(5,1));
  // 2nd row of size 5 filled with 2
  tab.push_back(vector<int>(5,2));

  tab[0][3] = 8;
  tab[0][4] = 9;
  tab[1][1] = 5;
  tab[1][2] = 4;
  showtab(tab);

  // Add 3 at the end of the 1st row
  tab[0].push_back(3);
  showtab(tab);

  return 0;
}

void showtab(vector<vector<int>> const &tab)
{
  unsigned int row(0), col(0);
  for(row=0; row<tab.size(); row++) {
    for(col=0; col<tab[0].size(); col++) {
      cout << " | " << tab[row][col];
    }
    cout << " |" << endl;
  }
  cout << "--------------------------" << endl;
}

 | 1 | 1 | 1 | 8 | 9 |
 | 2 | 5 | 4 | 2 | 2 |
--------------------------
 | 1 | 1 | 1 | 8 | 9 | 3 |
 | 2 | 5 | 4 | 2 | 2 | 0 |
--------------------------

Heterogeneous containers

main.cpp 
#include <iostream>
#include <string>
#include <vector>
#include "Garage.h"

using namespace std;

void showInfo(Vehicle const &vehicle);

int main()
{
  vector<Vehicle*> vehicles;
  unsigned int i(0);

  vehicles.push_back(new Car(8550, 5));
  vehicles.push_back(new Car(3950, 3));
  vehicles.push_back(new Motorcycle(3250, 200.5));

  vehicles[0]->showInfo();
  vehicles[2]->showInfo();

  for(i=0; i<vehicles.size(); ++i)
  {
    delete vehicles[i];
    vehicles[i] = 0;
  }

  return 0;
}

void showInfo(Vehicle const &vehicle)
{
  vehicle.showInfo();
}
Garage.h 
#ifndef DEF_GARAGE
#define DEF_GARAGE

class Vehicle
{
  public:
    Vehicle(int price);
    virtual void showInfo() const;
    virtual ~Vehicle();

  protected:
    int m_price;
};

class Car: public Vehicle
{
  public:
    Car(int price, int doors);
    virtual void showInfo() const;
    virtual ~Car();

  private:
    int m_doors;
};

class Motorcycle : public Vehicle
{
  public:
    Motorcycle(int price, double speed);
    virtual void showInfo() const;
    virtual ~Motorcycle();

  private:
    double m_speed;
};

#endif /* DEF_GARAGE */
Garage.cpp 
#include <iostream>
#include <string>
#include "Garage.h"

using namespace std;

/***
 *  Vehicle
 */
Vehicle::Vehicle(int price) : m_price(price) {}
Vehicle::~Vehicle() {}

void Vehicle::showInfo() const {
  cout << "This vehicle costs $" << m_price << "." << endl;
}


/***
 *  Car
 */
Car::Car(int price, int doors) : Vehicle(price), m_doors(doors) {}
Car::~Car() {}
void Car::showInfo() const {
  cout << "This car has " << m_doors << " doors and costs $" << m_price << "." << endl;
}

/***
 * Motorcycle
 */
Motorcycle::Motorcycle(int price, double speed) : Vehicle(price), m_speed(speed) {}
Motorcycle::~Motorcycle() {}
void Motorcycle::showInfo() const {
  cout << "This motorcycle can drive " << m_speed << "mph and costs $" << m_price << "." << endl;
}

The above code produces the following output: 

This car has 5 doors and costs $8550.
This motorcycle can drive 200.5mph and costs $3250.

Files

Write and Read file

Source Output 
#include <iostream>
#include <fstream> /* ifstream(), ofstream() */
#include <string> /* getline() */
using namespace std;

int main()
{
  string const myfile("test.txt");

  // file stream (write)
  ofstream mystream(myfile.c_str());
  if(!mystream) perror("Error creating stream");

  // Write to file
  mystream << "This is a test file" << endl;
  mystream << "Hello world!" << endl;

  // file stream (read)
  ifstream readfile(myfile.c_str());
  if(!readfile) perror("Error creating stream");

  // Read a word
  string word;
  readfile >> word;
  cout << "A word: " << word << endl;

  // Read file line by line
  string line;
  while( getline(readfile, line) )
    cout << "A line: " << line << endl;

  return 0;
}

$ ./main 
A word: This
A line:  is a test file
A line: Hello world!

Pointers

Syntax Description Example
&thing Address of thing
Source Output 
#include <iostream>
using namespace std;

int main()
{
  int num(3);
  cout << "Address of num: " << &num << endl;
  return 0;
}

Address of num: 0x7ffee04a04ec
type *ptr a pointer of type named ptr

Examples: 

string *pVar1(nullptr);
unsigned int *pVar2(nullptr);
vector<int> *pVar3(nullptr);
Syntax Output 
#include <iostream>
using namespace std;
int main()
{
  int num(10);
  int *pNum(nullptr);

  pNum = &num;

  cout << "num=" << num << endl;
  cout << "&num=" << &num << endl;
  cout << "pNum=" << pNum << endl;
  cout << "*pNum=" << *pNum << endl;

  return 0;
}

num=10
&num=0x7ffe377fd054
pNum=0x7ffe377fd054
*pNum=10
*ptr the value of whatever ptr is pointed at

Pointers and references

Source Run 
#include <iostream>
using namespace std;

int main()
{
  int num1(3);     // num1 set to 3
  int &num2(num1); // num2 as reference to num1
  cout << "num1=" << num1 << ", num2=" << num2 << endl;
 
  // If num1 is updated, num2 is also set to the updated value
  num1 = 4;
  cout << "num1=" << num1 << ", num2=" << num2 << endl;

  // If num2 is updated, num1 is also updated
  num2 = 5;
  cout << "num1=" << num1 << ", num2=" << num2 << endl;
  
  // This is because both num1 and num2 point to the same address
  cout << "Addr num1=" << &num1 << ", Addr. num2=" << &num2 << endl;
  return 0;
}

num1=3, num2=3
num1=4, num2=4
num1=5, num2=5
Addr num1=0x7ffcc98af0f4, Addr. num2=0x7ffcc98af0f4

Memory allocation

C C++ 
int *ageAlice = NULL;
ageAlice = malloc(sizeof(int));
if(ageAlice==NULL) exit(1);
// ...
free(ageAlice);

int *ageAlice(0);
ageAlice = new int;
// ...
delete(ageAlice);
ageAlice = 0;

Below is a full example:

Source Run 
#include <iostream>
using namespace std;

int main()
{
  int agePaul(0);
  int *ageAlice(0);
  ageAlice = new int;

  cout << "How old is Paul? ";
  cin >> agePaul;
  cout << "How old is Alice? ";
  cin >> *ageAlice;

  cout << "Paul is " << agePaul << " years old and Alice is " << *ageAlice << " years old." << endl;

  delete(ageAlice);
  ageAlice = 0;

  return 0;
}

$ ./main 
How old is Paul? 33
How old is Alice? 35
Paul is 33 years old and Alice is 35 years old.

Classes

Classes

The following program:

main.cpp 
#include <iostream>
#include <string>
#include "Player.h"
using namespace std;

int main()
{
    // Instantiation of Player class
    Player player1, player2("Sword", 20);

    // Actions (methods called from Player class)
    player2.attack(player1);
    player1.drinkHealingPotion(20);
    player2.attack(player1);
    player1.attack(player2);
    player2.switchWeapon("Ax", 40);
    player2.attack(player1);

    cout << "=== Player 1 ===" << endl;
    player1.showStatus();
    cout << "=== Player 2 ===" << endl;
    player2.showStatus();

    return 0;
}
Player.h 
#ifndef DEF_PLAYER
#define DEF_PLAYER

#include <iostream>
#include <string>
#include "Weapon.h"

class Player
{
    // Methods are public so that we can call them from main()
    public:

    Player(); // Default constructor
    Player(std::string weaponName, int weaponDamage); // Constructor that overrides the default weapon
    ~Player(); // Destructor

    void sufferDamage(int damage);
    void attack(Player &target);
    void drinkHealingPotion(int potionQuantity);
    void switchWeapon(std::string newWeaponName, int newWeaponDamage);
    bool isAlive();
    void showStatus();

    // Attributes should always remain private
    private:

    int m_lives;
    int m_mana;
    Weapon m_weapon;
};

#endif
Player.cpp 
#include "Player.h"
using namespace std;

// Initialization
Player::Player() : m_lives(100), m_mana(100) {}
Player::Player(string weaponName, int weaponDamage) : m_lives(100), m_mana(100), m_weapon(weaponName, weaponDamage) {}

// Destructor
Player::~Player() {}

void Player::sufferDamage(int damage)
{
    m_lives -= damage;
    if (m_lives < 0) m_lives = 0;
}

void Player::attack(Player &target)
{
    target.sufferDamage(m_weapon.getDamage());
}

void Player::drinkHealingPotion(int potionQuantity)
{
    m_lives += potionQuantity;
    if(m_lives>100) m_lives = 100;
}

void Player::switchWeapon(string newWeaponName, int newWeaponDamage)
{
    m_weapon.switchWeapon(newWeaponName, newWeaponDamage);
}

bool Player::isAlive()
{
    if (m_lives > 0)
    	return true;
    else
    	return false;
}

void Player::showStatus()
{
    cout << "Lives: " << m_lives << endl;
    cout << "Mana: " << m_mana << endl;
    m_weapon.showWeapon();
}
Weapon.h 
#ifndef DEF_WEAPON
#define DEF_WEAPON

#include <iostream>
#include <string>

class Weapon
{
    public:

    Weapon();
    Weapon(std::string name, int damage);
    ~Weapon();
    void switchWeapon(std::string name, int damage);
    void showWeapon();
    int getDamage() const; // accessor


    private:

    std::string m_name;
    int m_damage;
};

#endif
Weapon.cpp 
#include "Weapon.h"
using namespace std;

// Init
Weapon::Weapon() : m_name("Knife"), m_damage(10) {}
Weapon::Weapon(string name, int damage) : m_name(name), m_damage(damage) {}

// Destructor
Weapon::~Weapon() {}

void Weapon::switchWeapon(string name, int damage)
{
    m_name = name;
    m_damage = damage;
}

void Weapon::showWeapon()
{
    cout << "Weapon: " << m_name << " (Damage: " << m_damage << ")" << endl;
}

int Weapon::getDamage() const
{
    return m_damage;
}

...will show the following output: 

=== Player 1 ===
Lives: 40
Mana: 100
Weapon: Knife (Damage: 10)
=== Player 2 ===
Lives: 90
Mana: 100
Weapon: Ax (Damage: 40)

Inheritance

main.cpp 
#include <iostream>
#include <string>
#include "Vehicle.h"
#include "Car.h"
#include "Motorcycle.h"

using namespace std;

int main()
{
  Vehicle v(6800);
  v.showInfo();
  cout << "-----" << endl;

  Car c(8500, 4);
  c.showInfo();
  cout << "-----" << endl;

  Motorcycle m(3850, 200);
  m.showInfo();

  return 0;
}
Vehicle.h 
#ifndef VEHICLE_H_
#define VEHICLE_H_

class Vehicle {
  public:
    Vehicle(int price);
    virtual ~Vehicle();
    void showInfo() const;

 /* protected indicates that it
    remains private but accessible
    from the children */
 protected:
    int m_price;
};

#endif /* VEHICLE_H_ */
Vehicle.cpp 
#include <iostream>
#include <string>
#include "Vehicle.h"
using namespace std;

Vehicle::Vehicle(int price)
  : m_price(price) {}
Vehicle::~Vehicle() {}

void Vehicle::showInfo() const
{
  cout << "This vehicle costs $"
       << m_price
       << " (call from Vehicle class)."
       << endl;
}
Car.h 
#ifndef CAR_H_
#define CAR_H_

class Car : public Vehicle {
  public:
    Car(int price, int doors);
    virtual ~Car();
    void showInfo() const;

  private:
    int m_doors;
};

#endif /* CAR_H_ */
Car.cpp 
#include <iostream>
#include <string>
#include "Vehicle.h"
#include "Car.h"
using namespace std;

Car::Car(int price, int doors)
  : Vehicle(price), m_doors(doors) {}
Car::~Car() {}

void Car::showInfo() const
{
  /* Access price thanks to the
     protected mode in Vehicle class */
  cout << "This vehicle costs $"
       << m_price
       << " (access m_price from Vehicle)."
       << endl;
  cout << "This car has "
       << m_doors
       << " doors (Car member)."
       << endl;
}
Motorcycle.h 
#ifndef MOTORCYCLE_H_
#define MOTORCYLE_H_

class Motorcycle : public Vehicle {
  public:
    Motorcycle(int price, int speed);
    virtual ~Motorcycle();
    void showInfo() const;

  private:
    int m_speed;
};

#endif /* MOTORCYLE_H_ */
Motorcycle.cpp 
#include <iostream>
#include <string>
#include "Vehicle.h"
#include "Motorcycle.h"

using namespace std;

Motorcycle::Motorcycle(int price, int speed)
  : Vehicle(price), m_speed(speed) {}
Motorcycle::~Motorcycle() {}

void Motorcycle::showInfo() const
{
  // Call showInfo method from Vehicle
  Vehicle::showInfo();
  cout << "This motorcycle drives "
       << m_speed
       << "mph (Motorcycle member)."
       << endl;
}

The above code produces the following output: 

This vehicle costs $6800 (call from Vehicle class).
-----
This vehicle costs $8500 (access m_price from Vehicle).
This car has 4 doors (Car member).
-----
This vehicle costs $3850 (call from Vehicle class).
This motorcycle drives 200mph (Motorcycle member).

Static methods

main.cpp 
#include <iostream>
#include "Hello.h"

using namespace std;

int main()
{
  Hello::sayHello();
  return 0;
}
Hello.h 
#ifndef DEF_HELLO
#define DEF_HELLO

class Hello
{
  public:
    Hello();
    virtual ~Hello();
    static void sayHello();
};

#endif
Hello.cpp 
#include <iostream>
#include "Hello.h"

using namespace std;

Hello::Hello() {}
Hello::~Hello() {}

void Hello::sayHello()
{
  cout << "Hello" << endl;
}

The above code will produce the following output: 

Hello

Operator overloading

Comparison operators ("==" and "!=")

Below is the code for the == and != operators. The same logic can be applied for <, <=, > and >=.

main.cpp 
#include <iostream>
#include <string>
#include "Person.h"
using namespace std;

int main()
{
    Person person1("alice", 38), person2("paul", 35),
           person3("alice", 34), person4("paul", 35);

    cout << "Person1: ";
    person1.showInfo();

    cout << "Person2: ";
    person2.showInfo();

    cout << "Person3: ";
    person3.showInfo();

    cout << "Person4: ";
    person4.showInfo();

    if (person1 == person3)
    	cout << "Person 1 and 3 are the same" << endl;
    if (person1 != person3)
    	cout << "Person 1 and 3 are different" << endl;
    if (person2 == person4)
    	cout << "Person 2 and 4 are the same" << endl;
    if (person2 != person4)
    	cout << "Person 2 and 4 are different" << endl;

    return 0;
}
Person.h 
#ifndef DEF_PERSON
#define DEF_PERSON

class Person
{
    public:

    Person(std::string name, int age);
    ~Person();
    void showInfo();
    bool isIdentical(Person const& person) const;


    private:

    std::string m_name;
    int m_age;
};

bool operator==(Person const& person1, Person const& person2);
bool operator!=(Person const& person1, Person const& person2);

#endif
Person.cpp 
#include <iostream>
#include <string>
#include "Person.h"

using namespace std;

Person::Person(string name, int age)
	: m_name(name), m_age(age) {}
Person::~Person() {}

void Person::showInfo()
{
    cout << m_name << " is " << m_age << " years old." << endl;
}

bool Person::isIdentical(Person const& person) const
{
    return (m_name == person.m_name && m_age == person.m_age);
}

bool operator==(Person const& person1, Person const& person2)
{
    return person1.isIdentical(person2);
}

bool operator!=(Person const& person1, Person const& person2)
{
    return !person1.isIdentical(person2);
}

The above code will show the following output: 

Person1: alice is 38 years old.
Person2: paul is 35 years old.
Person3: alice is 34 years old.
Person4: paul is 35 years old.
Person 1 and 3 are different
Person 2 and 4 are the same

Arithmetic operators ("+", "-", "+=" and "-=")

main.cpp 
#include <iostream>
#include <string>
#include "Duration.h"
using namespace std;

int main()
{
    Duration duration1(3,25,25),
    		 duration2(1,45,38),
    		 duration3;

    cout << "Duration 1: ";
    duration1.showDuration();

    cout << "Duration 2: ";
    duration2.showDuration();

    duration3 = duration1 + duration2;
    cout << "Duration (1)+(2): ";
    duration3.showDuration();

    duration3 = duration1 - duration2;
    cout << "Duration (1)-(2): ";
    duration3.showDuration();

    return 0;
}
Duration.h 
#ifndef DEF_DURATION
#define DEF_DURATION

class Duration {
	public:
		Duration(int hours=0, int minutes=0, int seconds=0);
		~Duration();
		void showDuration();
		Duration& operator+=(const Duration &duration);
		Duration& operator-=(const Duration &duration);

	private:
		int m_hours;
		int m_minutes;
		int m_seconds;
};

Duration operator+(Duration const& duration1, Duration const& duration2);
Duration operator-(Duration const& duration1, Duration const& duration2);

#endif /* DEF_DURATION */
Duration.cpp 
#include <iostream>
#include <string>
#include <iomanip> /* for proper time format */
#include "Duration.h"

using namespace std;

Duration::Duration(int hours, int minutes, int seconds)
	: m_hours(hours), m_minutes(minutes), m_seconds(seconds) {}
Duration::~Duration() {}

void Duration::showDuration()
{
	cout << setfill('0') << setw(2) << m_hours
		<< ":" << setfill('0') << setw(2) << m_minutes
		<< ":" << setfill('0') << setw(2) << m_seconds
		<< endl;
}

Duration& Duration::operator+=(const Duration &duration)
{
	int nseconds = m_hours * 3600 + m_minutes * 60 + m_seconds;
	nseconds += duration.m_hours * 3600 + duration.m_minutes * 60 + duration.m_seconds;
	m_hours = nseconds / 3600;
	m_minutes = nseconds % 3600 / 60;
	m_seconds = nseconds % 3600 % 60;
	return *this;
}

Duration& Duration::operator-=(const Duration &duration)
{
	int nseconds = m_hours * 3600 + m_minutes * 60 + m_seconds;
	nseconds -= duration.m_hours * 3600 + duration.m_minutes * 60 + duration.m_seconds;
	m_hours = nseconds / 3600;
	m_minutes = nseconds % 3600 / 60;
	m_seconds = nseconds % 3600 % 60;
	return *this;
}

Duration operator+(Duration const& duration1, Duration const& duration2)
{
	Duration copyDuration1(duration1);
	copyDuration1 += duration2;
	return copyDuration1;
}

Duration operator-(Duration const& duration1, Duration const& duration2)
{
	Duration copyDuration1(duration1);
	copyDuration1 -= duration2;
	return copyDuration1;
}

It outputs: 

Duration 1: 03:25:25
Duration 2: 01:45:38
Duration (1)+(2): 05:11:03
Duration (1)-(2): 01:39:47

Stream operator

Modify Duration.h and Duration.cpp as follows:

Duration.h 
#ifndef DEF_DURATION
#define DEF_DURATION

class Duration {
	public:
		Duration(int hours=0, int minutes=0, int seconds=0);
		~Duration();
		void showDuration(std::ostream &mystream) const;
		Duration& operator+=(const Duration &duration);
		Duration& operator-=(const Duration &duration);

	private:
		int m_hours;
		int m_minutes;
		int m_seconds;
};

Duration operator+(Duration const& duration1, Duration const& duration2);
Duration operator-(Duration const& duration1, Duration const& duration2);
std::ostream &operator<<(std::ostream &mystream, Duration const& duration);

#endif /* DEF_DURATION */
Duration.cpp 
#include <iostream>
#include <string>
#include <iomanip> /* for proper time format */
#include "Duration.h"

using namespace std;

Duration::Duration(int hours, int minutes, int seconds)
	: m_hours(hours), m_minutes(minutes), m_seconds(seconds) {}
Duration::~Duration() {}

void Duration::showDuration(ostream &mystream) const
{
	mystream << setfill('0') << setw(2) << m_hours
		<< ":" << setfill('0') << setw(2) << m_minutes
		<< ":" << setfill('0') << setw(2) << m_seconds;
}

Duration& Duration::operator+=(const Duration &duration)
{
	int nseconds = m_hours * 3600 + m_minutes * 60 + m_seconds;
	nseconds += duration.m_hours * 3600 + duration.m_minutes * 60 + duration.m_seconds;
	m_hours = nseconds / 3600;
	m_minutes = nseconds % 3600 / 60;
	m_seconds = nseconds % 3600 % 60;
	return *this;
}

Duration& Duration::operator-=(const Duration &duration)
{
	int nseconds = m_hours * 3600 + m_minutes * 60 + m_seconds;
	nseconds -= duration.m_hours * 3600 + duration.m_minutes * 60 + duration.m_seconds;
	m_hours = nseconds / 3600;
	m_minutes = nseconds % 3600 / 60;
	m_seconds = nseconds % 3600 % 60;
	return *this;
}

Duration operator+(Duration const& duration1, Duration const& duration2)
{
	Duration copyDuration1(duration1);
	copyDuration1 += duration2;
	return copyDuration1;
}

Duration operator-(Duration const& duration1, Duration const& duration2)
{
	Duration copyDuration1(duration1);
	copyDuration1 -= duration2;
	return copyDuration1;
}

ostream &operator<<(ostream &mystream, Duration const& duration)
{
	duration.showDuration(mystream);
	return mystream;
}

Now, we can display our class directly from cout:

main.cpp 
#include <iostream>
#include <string>
#include "Duration.h"
using namespace std;

int main()
{
    Duration duration1(3,25,25),
    		 duration2(1,45,38);

    cout << "Duration 1: " << duration1 << endl;
    cout << "Duration 2: " << duration2 << endl;
    cout << "Duration (1)+(2): " << duration1+duration2 << endl;
    cout << "Duration (1)-(2): " << duration1-duration2 << endl;

    return 0;
}

Some programs

guess-word
Player 1 is entering a secret. This secret is scrambled and shown to player 2 who should guess the secret
Download

Subcategories

This category has the following 2 subcategories, out of 2 total.

A

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