Operator Overload = Not Working

Again Problem With teh Same Point Class
Code Pasted Here http://phpfi.com/246031
BEFORE I used

Code:

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pt2 = pt1;//Works fine

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But I noticed that
Its not calling the overloaded 'Operator='
So I made it

Code:

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*pt1 -= *pt2;

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On line 44 But Although Its Calling the Overloaded 'Operator='
{As its printing "I am Getting Executed" on the line}
This is the 'Operator=' function

Code:

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Point* Point::operator=(const Point& pt){
        cout<<"I am Getting Executed"<<endl;
        return this;//datatype Of this is Point* Const
}

---

On line 20-22
Please help.
--------------------------------------------------------------------
here is the Output of this Programm
--------------------------------------------------------------------

Code:

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Describing Class :              pt1            x = 15  y = 10
Describing Class : pt2 before Copying          x = 4  y = 8
I am Getting Executed
Describing Class : pt2 after Copying            x = 4  y = 8
destructing
Describing Class : pt2 after Increamenting              x = 9  y = 13
destructing
Describing Class : pt1 after Decrementing              x = 6  y = -3

---

Make operator=, operator+= and operator-= all return a Point&, not a Point or Point*.

In fact, because none of your member variables are in need of memory management by you, you can just use the compiler provided copy assignment operator and thus not provide your own operator=.

Also, as mentioned, there is no need to write:
Point* pt1 = new Point(15, 10);
You can just use:
Point pt1(15, 10);

If you do use new, then you should have a corresponding delete.

Thanks anyway
I've fixed it by myself.
My 'operator=' Function

Code:

---

Point* Point::operator=(const Point& pt){
        return this;//datatype Of this is Point* Const
}

---

was not doing anything So I made it like this.

Code:

---

Point* Point::operator=(const Point& pt){
        this->x = pt.x;
        this->y = pt.y;
        return this;//datatype Of this is Point* Const
}

---

And Its Working Fine
I am New to C++ Previously I used Code like this
var = new class_name(args)
var->member_function()->member_var
So I need to use new to adjust.

That is a wrong fix. Yes, this is a pointer. But now, how would you go about doing copying without pointers?

Rather, write your copy assignment operator along these lines:

Code:

---

Point& Point::operator=(const Point& pt) {
    x = pt.x;
    y = pt.y;
    return *this;
}

---

You may also include a check for self-assignment:

Code:

---

Point& Point::operator=(const Point& pt) {
    if (this != &pt) {
        x = pt.x;
        y = pt.y;
    }
    return *this;
}

---

If you provide a swap member function, you could even write:

Code:

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Point& Point::operator=(const Point& pt) {
    Point temp(pt);
    swap(temp);
    return *this;
}

---

Quote:

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I am New to C++ Previously I used Code like this
var = new class_name(args)
var->member_function()->member_var
So I need to use new to adjust.

---

Then where's your delete? I suggest that you learn how to use C++ without pointers first. It seems to be causing you lots of unnecessary problems.

Quote:

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Quote:I am New to C++ Previously I used Code like this
var = new class_name(args)
var->member_function()->member_var
So I need to use new to adjust.

Then where's your delete?

---

I didnt need to delete often cause after execution of the Function it went out from memory.
Whenm used As Global I used unset(var) to delete.But that was not mandatory.
------------------------------------------------------------------
However I didnt Understand this Line

Quote:

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how would you go about doing copying without pointers? It would be something of a hack involving the address-of operator,

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Quote:

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I didnt need to delete often cause after execution of the Function it went out from memory.
Whenm used As Global I used unset(var) to delete.But that was not mandatory.

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What's unset()? As for delete: there is no guarantee that the system will reclaim resources without the delete, so just use it.

Quote:

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However I didnt Understand this Line

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Actually, I think that by returning a Point*, you probably cannot use it for normal copy assignment.

Take this for example:

Code:

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Point a, b(1, 2);
a = b;

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At a glance, most people will expect that this means that a is now a copy of b. With your code, there would be an error. So, how do we make a into a copy of b?

So here I need To use

Code:

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Point* pt1 = new Point;
Point *pt2 = new Point(1, 2);
*a = *b

---

am I right ??

hmm... I looked more carefully, and I think that I am wrong: there should not be an error produced for my example. There would only be an error for operator chaining, e.g.,
a = b = c;

Quote:

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So here I need To use

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No, stop using pointers for the time being. You do not need them. It should be something as simple as:

Code:

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Point pt1;
Point pt2(1, 2);
a = b;

---

Ok this is my code now http://phpfi.com/246046
I am Getting this Following Error

no Match for 'operator=' in 'pt3 = pt1'
No candidats are : Point* point::operator=(const Point&)

NOTE
NO problem on line Number 41 it has been fixed before
I've forgotten to remove that Comment line

Why are you using pointers? Why are you using new? This is not Java, you don't use new to create normal objects.

You also aren't using the advice you are being given. You don't need an operator=, and if you are going to write one don't have it return a Point*.

I am not making it professionaly I need to learn Pointers, I need to focus on new . I am Learning C++
And see on line 45 I am Using normal Class
and then I got that Error
Please tell me how can I solve the Problem.

Cool just one Change and it worked
I've changed on line number 48
pt3 = pt1;
to
pt3 = *pt1;
It worked Nice
But Why ??

Quote:

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Originally Posted by noobcpp

Cool just one Change and it worked
I've changed on line number 48
pt3 = pt1;
to
pt3 = *pt1;
It worked Nice
But Why ??

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It didn't work because you were assigning a pointer to an object.
Now you're assigning an object to an object.
Trouble is that the compiler is not using your overloaded assignement operator

Code:

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Point * operator=(const Point&);//Overloading = operator

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it uses the the

Code:

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Point & operator=(const Point&);

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that it created for you and this will result in a memory leak
because of the char* note member variable.
Kurt

Because pt1 is a pointer and needs to be dereferenced like you do in every other place...

Quote:

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Trouble is that the compiler is not using your overloaded assignement operator...

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Why would that be? If it were so, wouldn't there be an error because there's a function overload based on return type only?

Returning a pointer from operator= is bad, as mentioned earlier, but in x = y; (x.operator=(y);) the return value is not used.

No Compiler is executing My overloaded operator I've tested using

Code:

---

Point* Point::operator=(const Point& pt){
        cout<<"Compiler is executing Me"<<endl;
        this->x = pt.x;
        this->y = pt.y;
        return this;//datatype Of this is Point* Const
}

---

And it has Printed "Compiler is executing Me" 2 times
I've forgotten to Use the char* note I'll Use that latter.

Yes I found that out in the meantime. Was just confused by the strange overload.
Sorry.
Kurt

I am learning. So whatever I'll do now would be strange.

Don't mix learning two things at once. If you want to learn pointers, learn pointers. (But learn both how and when to use them. The learning effect of using new Java-style is just about nil.) If you want to learn operator overloading, learn operator overloading. Don't mix the two. It leads to strange results, as you've discovered.

I am actually a very experienced PHP programmer that's why I am much familiar with new and -> operator
And -> can be used with pointer only.
And that's why I've a tendency to use new.else it looks like Function not like object to myself.
And what can I do if new operator involves Pointer.

In this case you don't need to learn but unlearn about pointers :)

Quote:

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Originally Posted by anon

In this case you don't need to learn but unlearn about pointers :)

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Hey Why ??
Is there any way of using new without pointers ??
If yes then Please tell me.

Quote:

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Originally Posted by noobcpp

Hey Why ??
Is there any way of using new without pointers ??
If yes then Please tell me.

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Sorry to disappoint you. All that operator new does is creating an object and returning pointer to that object. There is no way to access that object without using that pointer.
Kurt

OK.
Thanks Pointer is Cool then.
But I still didn't Understand

Quote:

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Originally Posted by anon

you don't need to learn but unlearn about pointers

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Quote:

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Originally Posted by noobcpp

OK.
Thanks Pointer is Cool then.

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Most C++ users will disagree on that. They think that pointers should not be used unless there is no other way to get a problem solved ( it's too easy to create memory leaks when using pointers ).
Kurt

In PHP its too hard to make a parser.It has only refference although I've atlast Made it.
Its a HTML / XML / wml / ...ML Parser Compleately made by PHP (95 % made still now)
With it you can Parse XMl with SQL like Statement. and Its very fast It takes just 0.02 MICROsecond to parse a Standerd XML File
Now I wanna Convert it to C and C++ also
Thats why I found pointer and refference in C++ Very Cool.
PHP keeps Pointer Internally But dont lets us to use it like C++ or C.

About why it's wrong to return a pointer to object from overloaded = operator.

With built-in types it is normal to write the following to set both a and b to c.

Code:

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int a, b, c = 42;
a = b = c; // means: a = (b = c);

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If you return a pointer from your operator overload, you couldn't use this syntax any more. Instead you'll need to dereference the returned pointer.

Code:

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MyClass a, b, c;
a = *(b = c);

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If you added more assignments to the chain, it would look even worse.

That's why this overload should return a reference instead.

Oh! I see.

C++ is not PHP. If you learn a new language, you will have to learn the best practices for this language, else your code will be bad. For C++, using pointers only where necessary is a best practice.

I think you are right.