Classes and Objects in C++
practice.

#include <iostream>
using namespace std;
int main()
{
    typedef int num;
    num a = 10, b = 15;
    num c = a + b + a - b;
    cout << c;
    return 0;
}

#include <iostream>
#include <string>
using namespace std;
class B
{
	int b;
   public:
	B(int i){
		b = i;
	}
};
 
class C
{
	B b;
    public:
	C(int i){
		b = B(i);
	}
	friend void show();
};
 
void show()
{
	C c(10);
	cout<<"value of b is: "<<c.b.b<<endl;
}
 
int main(int argc, char const *argv[])
{
	show();
	return 0;
}

#include <iostream>
#include <string>
using namespace std;
int main ()
{
    string str ("nobody does like this");
    string key ("nobody");
    size_t f;
    f = str.rfind(key);
    if (f != string::npos)
        str.replace (f, key.length(), "everybody");
    cout << str << endl;
    return 0;
}

---------------------------
Example class:
class A
{
	public:
		static int value;
}
---------------------------

#include <iostream>
using namespace std;
class myclass
{
    public:
    int i;
    myclass *operator->()
    {return this;}
};
int main()
{
    myclass ob;
    ob->i = 10; 
    cout << ob.i << " " << ob->i;
    return 0;
}

#include <iostream>
#include <complex>
using namespace std;
int main()
{
    complex<double> c_double(2, 3);
    complex<int> c_int(4, 5);
    c_double *= 2;
    c_double = c_int;
    cout << c_double;
    return 0;
}

#include <iostream>
using namespace std;
int operate (int a, int b)
{
    return (a * b);
}
float operate (float a, float b)
{
    return (a / b);
}
int main ()
{
    int x = 5, y = 2;
    float n = 5.0, m = 2.0;
    cout << operate (x, y);
    cout << operate (n, m);
    return 0;
}

#include <iostream>
using namespace std;
class Box
{
    public :
    double length;
    double breadth;
    double height;
};
int main( )
{
    Box Box1;
    double volume;
    Box1.height = 5;
    Box1.length = 6;
    Box1.breadth = 7.1;
    volume = Box1.height * Box1.length * Box1.breadth;
    cout << "Volume of Box1 : " << volume <<endl;
    return 0;
}

#include <iostream>
using namespace std;
class sample 
{
    int width, height;
    public:
    void set_values (int, int);
    int area () {return (width * height);}
    friend sample duplicate (sample);
};
void sample::set_values (int a, int b) 
{
    width = a;
    height = b;
}
sample duplicate (sample rectparam)
{
    sample rectres;
    rectres.width = rectparam.width * 2;
    rectres.height = rectparam.height * 2;
    return (rectres);
}  
int main ()  
{
    sample rect, rectb;
    rect.set_values (2, 3);
    rectb = duplicate (rect);
    cout << rectb.area();
    return 0;
}