classes

[Errratic]

hay guys, im having trouble with this code in the toutorial
// static members in classes
#include <iostream>
using namespace std;

class CDummy {
public:
static int n;
CDummy () { n++; };
~CDummy () { n--; };
};

int CDummy::n=0;

int main () {
CDummy a;
CDummy b[5];
CDummy * c = new CDummy;
cout << a.n << endl;
delete c;
cout << CDummy::n << endl;
return 0;
}

but it outputs 7 and then 6, shouldnt it output 0? i mean how is the static variable increased from 0 to 7 and then 6? pls help

[Errratic]

w8 is it like everytime we declare something with type CDummy, n increases? and then when something of that type is deleted n is decreased? if so u someone explain to me properly hoe the ~ operator works?

[Disch]

Remember that constructors are called every time an object is created, and destructors are called every time an object is destroyed.

class CDummy {
public:
static int n;
CDummy () { n++; };  // this is the constructor
~CDummy () { n--; };  // this is the destructor
};

Every time the constructor is called (when an object is created), 'n' increments by 1. Every time the destructor is called (when an object is destroyed), 'n' decrements by 1.

int CDummy::n=0;  // n starts at zero

int main () {
CDummy a;  // this creates an object.  n is incremented by 1.  n==1
CDummy b[5];  // this creates 5 objects.  n is incremented 5 times
        // once for each object.  n==6
CDummy * c = new CDummy;  // this creates another object.  n==7
cout << a.n << endl;  // this prints 7
delete c;  // this destroys an object.  n==6
cout << CDummy::n << endl;  // this prints 6 

EDIT:

it's not really about the ~ operator... it's about ctors and dtors.

I think you skipped over an important section of the tutorial.

http://cplusplus.com/doc/tutorial/classes/ <-- see section on constructors and destructors.