[sepp2k]

Writing cout << a += b is the same as writing the following:

cout << a;
cout += b;

Do you understand why cout += b can not work?

[healix]

sepp2k, on 15 August 2012 - 09:47 AM, said:

Writing cout << a += b is the same as writing the following:

cout << a;
cout += b;

Do you understand why cout += b can not work?

I understand why

cout += b;

can't work. But what I'm confused about is adding an ostream to the '+=' overload function. How does that work?

and what about this example from wiki?

Vector2D& Vector2D::operator+=(const Vector2D& right)
{
    this->x += right.x;
    this->y += right.y;
    return *this;
}

This post has been edited by healix: 15 August 2012 - 10:18 AM

[sepp2k]

healix, on 15 August 2012 - 07:15 PM, said:

I understand why

cout += b;

can't work. But what I'm confused about is adding an ostream to the '+=' overload function. How does that work?

It doesn't. The fix here isn't to make += work with a stream as the left operand, it's to re-write the expression, so that the left operand of += is a and not cout << a.

Quote

and what about this example from wiki?

What about it?

[Skydiver]

healix, on 15 August 2012 - 10:15 AM, said:

sepp2k, on 15 August 2012 - 09:47 AM, said:

Writing cout << a += b is the same as writing the following:

cout << a;
cout += b;

Do you understand why cout += b can not work?

I understand why

cout += b;

can't work. But what I'm confused about is adding an ostream to the '+=' overload function. How does that work?

That is how the C++ compiler is parsing the line statement: cout << a += b
This is due to the operator precedence in C++: http://en.cppreferen...ator_precedence

healix, on 15 August 2012 - 10:15 AM, said:

and what about this example from wiki?

Vector2D& Vector2D::operator+=(const Vector2D& right)
{
    this->x += right.x;
    this->y += right.y;
    return *this;
}

What is your question about that example? It's showing how an overload of the += operator is being implemented.

[healix]

ok I think I see what's going on. Not sure we were on the same page.

In main I can't write

cout << a+=b;

but I can write

 a+=b; 

which works.

so then how would I make it so that it can be written as

 cout << a+=b; 

overload stream, use paranthesis?

[Skydiver]

Although parenthesis will work, just write it out as two lines.

a += b;
cout << a;

[healix]

ok, thanks everyone. really appreciated

[blackcompe]

Good catch, sepp2k. I totally missed that.