Why return *this

[bluekite2000]

In one of the books, the author writes:
Class Complex
{
....
Complex& operator+=(const Complex& Other)
{
real_+=Other.real_;
im_+=Other.im_;
return *this;
}
....
}

Why cant it just be
void operator+=(const Complex& Other)
{
real_+=Other.real_;
im_+=Other.im_;

}

 

[Andre Kostur]

(e-mail address removed) wrote in @g14g2000cwa.googlegroups.com:

In one of the books, the author writes:
Class Complex
{
...
Complex& operator+=(const Complex& Other)
{
real_+=Other.real_;
im_+=Other.im_;
return *this;
}
...
}

Why cant it just be
void operator+=(const Complex& Other)
{
real_+=Other.real_;
im_+=Other.im_;

}

So that one can do:

Complex x;

x += othercomplex += thirdcomplex;

 

[Howard]

In one of the books, the author writes:
Class Complex
{
...
Complex& operator+=(const Complex& Other)
{
real_+=Other.real_;
im_+=Other.im_;
return *this;
}
...
}

Why cant it just be
void operator+=(const Complex& Other)
{
real_+=Other.real_;
im_+=Other.im_;

}

It could be... but then the result couldn't be used in an expression. Why
limit yourself?

-Howard

 

[Rolf Magnus]

In one of the books, the author writes:
Class Complex
{
...
Complex& operator+=(const Complex& Other)
{
real_+=Other.real_;
im_+=Other.im_;
return *this;
}
...
}

Why cant it just be
void operator+=(const Complex& Other)
{
real_+=Other.real_;
im_+=Other.im_;

}

It can, but shouldn't. A good rule for operator overloading is: "do it as
int does". And you can e.g. write:

a = b = c;

Therefore, it's good to return a reference to an object, so that you can use
the assignment in other expressions.