Problem with chaining operator<< and operator++

Question

I\'m learning C++ and I have this problem:

#include 
using namespace std;


class test
{
    public:
             


        

Answer 1

For starters the data member i can be uninitialized if the default constructor will be used.

Either declare the data member like

int var = 0;

Or redefine the default constructor for example by using the delegating constructor.

class test
{
    public:
    test() : test( 0 ){};
    test(int i):var{i}{};
    // ...

The pre-increment operator should look like

test& operator++(){++var; return *this;}
                                 ^^^^^

In the post-increment operator the identifier dummy is not used. So remove it

test  operator++( int ){test tmp =*this;var++;return tmp;}

This statement

cout << obj <<' '<< ++obj<

has undefined behavior because reading writing the object obj are not sequenced.

You have to split this statement into two statements

cout << obj <<' ';
cout << ++obj<