| Topic: |
DEVELOP > c-Plus-Plus |
| User: |
"India" |
| Date: |
20 Dec 2007 11:20:12 PM |
| Object: |
overloaded operator=() |
overloaded operator=()
--------------------------------
overloaded assignment operator should be a non-static MEMBER function
of a class. This ensures that the first operand is an lvalue.
If the overloaded assignment operator function is allowed to be a non-
member function then we may be able to write the following:
Suppose we have a class Test for which operator+() is defined,
suppose we have
Test operator=(Test lhs, Test rhs)
{
Test obj;
//...
Return obj;
}
Test x;
Test y;
Test x;
x + y = z;
This is wrong because x + y is not an lvalue but would become legal
due to the above definition of overloaded operator=(). That is why
operator=() should be a member function. Is this understanding of mine
is correct ?
Kindly clarify.
Thanks
V.Subramanian
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| User: "Sachin" |
|
| Title: Re: overloaded operator=() |
21 Dec 2007 12:02:43 AM |
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On Dec 21, 10:20=A0am, "subramanian10...@yahoo.com, India"
<subramanian10...@yahoo.com> wrote:
overloaded operator=3D()
--------------------------------
overloaded assignment operator should be a non-static MEMBER function
of a class. This ensures that the first operand is an lvalue.
If the overloaded assignment operator function is allowed to be a non-
member function then we may be able to write the following:
Suppose =A0we have a class Test for which operator+() is defined,
suppose we have
Test operator=3D(Test lhs, Test rhs)
{
=A0 =A0 =A0 =A0 Test obj;
//...
Return obj;
}
Test x;
Test y;
Test x;
x + y =3D z;
This is wrong because x + y is not an lvalue but would become legal
due to the above definition of overloaded operator=3D(). That is why
operator=3D() should be a member function. Is this understanding of mine
is correct ?
Kindly clarify.
Thanks
V.Subramanian
x+y =3D z is legal or not depends on implementation of operator+
Test Operator+(Test) // above call x+y =3D z works
void Operator+(Test t1, Test t2); // above call returns an error
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| User: "James Kanze" |
|
| Title: Re: overloaded operator=() |
21 Dec 2007 06:48:55 AM |
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On Dec 21, 6:20 am, "subramanian10...@yahoo.com, India"
<subramanian10...@yahoo.com> wrote:
overloaded operator=3D()
--------------------------------
overloaded assignment operator should be a non-static MEMBER function
of a class. This ensures that the first operand is an lvalue.
No it doesn't.
The reason a user defined assignment operator (overloaded or
not) should be a member is first and foremost because the
standard doesn't allow it to be a non-member. The reason the
standard doesn't allow this is because if there isn't a user
declared copy assignment operator, the standard implicitly
declares one.
If the overloaded assignment operator function is allowed to
be a non-member function then we may be able to write the
following:
Suppose we have a class Test for which operator+() is defined,
suppose we have
Test operator=3D(Test lhs, Test rhs)
{
Test obj;
//...
Return obj;
}
I suppose that the above is a typo; that you meant to define
operator+. (Defining an operator=3D which took all of its
parameters by value wouldn't make any sense.)
Test x;
Test y;
Test x;
x + y =3D z;
This is wrong because x + y is not an lvalue but would become
legal due to the above definition of overloaded operator=3D().
That is why operator=3D() should be a member function. Is this
understanding of mine is correct ?
Not at all. In fact, if operator+ returns a non-const object
(which is usually the case), then the above is legal.
--
James Kanze (GABI Software) email:james.kanze@gmail.com
Conseils en informatique orient=E9e objet/
Beratung in objektorientierter Datenverarbeitung
9 place S=E9mard, 78210 St.-Cyr-l'=C9cole, France, +33 (0)1 30 23 00 34
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