Re: =?UTF-8?B?Kz0=?= operation

From:
Sam <sam@email-scan.com>
Newsgroups:
comp.lang.c++
Date:
Sat, 14 Jun 2008 11:35:37 -0500
Message-ID:
<cone.1213461336.906187.2581.500@commodore.email-scan.com>
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foolsmart2005@gmail.com writes:

for += operation, my code is:
ComplexNum ComplexNum::operator += (const ComplexNum& rhs) const
{
           ComplexNum ans;
           ans.real += rhs.real;
           ans.imaginary += rhs.imaginary;
           return ans;
 }

here is lecturer's comment:
+= should be different. a += b means a = a + b


Your lecturer should've also told you that your results are undefined since
the contents of the ans object are, apparently, not initialized. Your +=
operation on ans's members are applied to, apparently, uninitialized members
of this object. This would be the same as writing:

   int x;

   x += 4;

Obviously, the results of this are undefined.

therefore *this object (i.e. a) should be updated with the answer.


Correct.

Do anyone know how to write += operation?


Yes, but why don't you try to figure this out yourself. Look around, there
are plenty of examples of assignment operators for other classes. Here are
two free clues:

1) operator += modifies this object, therefore it cannot be a const
function (well, it can be, but you're not there, yet).

2) The assignment operator, be it operator =(), operator +=(), operator
-=(), or anything else, traditional does not return another instance of the
object, but rather a reference to this, modified, object.

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