operation overloading headache

[Guest]

The code below I suspect creates memory leaks:
In the main() in line "c += a + b;" when compiler runs "a + b" creates a new object.
After "c += 'new_object'"
we have an unreferenced object which created from "a + b" and not destroyed.
am I right?
What I can do to avoid this?
------------------------------
class Vector3D {
protected:
float _x, _y, _z;
public:
Vector3D(float x, float y, float z) : _x(x), _y(y), _z(z) {}
const Vector3D &operator+=(con st Vector3D &a);
friend const Vector3D operator+(const Vector3D &a, const Vector3D &b);
};

const Vector3D &Vector3D::oper ator+=(const Vector3D &a) {
_x += a._x; _y += a._y; _z += a._z; return *this;
}
const Vector3D operator+(const Vector3D &a, const Vector3D &b) {
return Vector3D(a._x + b._x, a._y + b._y, a._z + b._z);
}

void main() {
Vector3D a = Vector3D(1, 2, 3);
Vector3D b = Vector3D(4, 5, 6);
Vector3D c = Vector3D(0, 0, 0);
c += a + b;
}

[Guest]

Re: operatOR overloading headache

Not OperatION, operatOR. Sorry!
[color=blue]
> The code below I suspect creates memory leaks:
> In the main() in line "c += a + b;" when compiler runs "a + b" creates a new object.
> After "c += 'new_object'"
> we have an unreferenced object which created from "a + b" and not destroyed.
> am I right?
> What I can do to avoid this?
> ------------------------------
> class Vector3D {
> protected:
> float _x, _y, _z;
> public:
> Vector3D(float x, float y, float z) : _x(x), _y(y), _z(z) {}
> const Vector3D &operator+=(con st Vector3D &a);
> friend const Vector3D operator+(const Vector3D &a, const Vector3D &b);
> };
>
> const Vector3D &Vector3D::oper ator+=(const Vector3D &a) {
> _x += a._x; _y += a._y; _z += a._z; return *this;
> }
> const Vector3D operator+(const Vector3D &a, const Vector3D &b) {
> return Vector3D(a._x + b._x, a._y + b._y, a._z + b._z);
> }
>
> void main() {
> Vector3D a = Vector3D(1, 2, 3);
> Vector3D b = Vector3D(4, 5, 6);
> Vector3D c = Vector3D(0, 0, 0);
> c += a + b;
> }
>
>[/color]

[Peter van Merkerk]

Re: operation overloading headache

"<- Chameleon ->" <cham_gss@hotma il.NOSPAM.com> wrote in message
news:bki555$nik $1@nic.grnet.gr ...[color=blue]
> The code below I suspect creates memory leaks:
> In the main() in line "c += a + b;" when compiler runs "a + b" creates a[/color]
new object.[color=blue]
> After "c += 'new_object'"
> we have an unreferenced object which created from "a + b" and not[/color]
destroyed.[color=blue]
> am I right?[/color]

No. You don't have to worry about a memory leak; temporary objects will be
automatically destroyed after the expression which caused them to be created
has been fully evaluated.

--
Peter van Merkerk
peter.van.merke rk(at)dse.nl

[Alf P. Steinbach]

Re: operation overloading headache

On Sat, 20 Sep 2003 21:06:41 +0300, "<- Chameleon ->" <cham_gss@hotma il.NOSPAM.com> wrote:
[color=blue]
>The code below I suspect creates memory leaks:[/color]

Nope.

But it's prone to have other bugs since you don't use indentation.


[color=blue]
>In the main() in line "c += a + b;" when compiler runs "a + b" creates a new object.[/color]

The new object (if any, this depends on what optimizations the compiler
throws in; read about RVO) is a temporary one, on the stack, and it's
discarded after its value is assigned to 'c'.


[color=blue]
>After "c += 'new_object'"
>we have an unreferenced object which created from "a + b" and not destroyed.
>am I right?[/color]

No.

[color=blue]
>What I can do to avoid this?[/color]

Write correct code.

[color=blue]
>------------------------------
>class Vector3D {
>protected:
>float _x, _y, _z;[/color]

Don't use leading underscores. In C++ names beginning with leading
underscore followed by uppercase letter are reserved for the
implementation. In C there are even more restrictions.

If you don't have a lot of vectors at the same time, consider using
'double' instead of 'float'. 'double' has better precision and on
modern machines is as fast as, or even faster than, 'float'.

[color=blue]
>public:
>Vector3D(flo at x, float y, float z) : _x(x), _y(y), _z(z) {}[/color]

Do use indentation, and also some blank lines.

[color=blue]
>const Vector3D &operator+=(con st Vector3D &a);[/color]


[color=blue]
>friend const Vector3D operator+(const Vector3D &a, const Vector3D &b);
>};
>
>const Vector3D &Vector3D::oper ator+=(const Vector3D &a) {
>_x += a._x; _y += a._y; _z += a._z; return *this;
>}[/color]

OK except for formatting and names.

[color=blue]
>const Vector3D operator+(const Vector3D &a, const Vector3D &b) {
>return Vector3D(a._x + b._x, a._y + b._y, a._z + b._z);
>}[/color]

OK except for formatting and names.


[color=blue]
>void main() {[/color]

Non-standard extension. Use a standard 'main'.

[color=blue]
>Vector3D a = Vector3D(1, 2, 3);
>Vector3D b = Vector3D(4, 5, 6);
>Vector3D c = Vector3D(0, 0, 0);
>c += a + b;
>}[/color]


To be honest, Vector3D looks like someone else's code reformatted.

[Guest]

Re: operation overloading headache

> >The code below I suspect creates memory leaks:[color=blue]
> Nope.
> But it's prone to have other bugs since you don't use indentation.[/color]

Thanks for your response.
What is indentation? I don't understand the word ;-(
[color=blue][color=green]
> >What I can do to avoid this?[/color]
>
> Write correct code.[/color]

lol ;-)
[color=blue]
> Do use indentation, and also some blank lines.
> OK except for formatting and names.[/color]

I "pack" the code to avoid a big message.
[color=blue][color=green]
> >Vector3D a = Vector3D(1, 2, 3);
> >Vector3D b = Vector3D(4, 5, 6);
> >Vector3D c = Vector3D(0, 0, 0);
> >c += a + b;
> >}[/color]
> To be honest, Vector3D looks like someone else's code reformatted.[/color]

grrrrrr! of course its mine! I am trying to test operator overloading because I read "Thinking in C++"
Because I use OpenGL, I am trying to write (what else) a Vector3D class

[Agent Mulder]

Re: operation overloading headache

<Alf P. Steinbach>[color=blue]
>To be honest, Vector3D looks like someone else's code reformatted.[/color]
</>

That's a good way to learn. I recommend it to every student. Reformat
someone else's code.

<- Chameleon ->
What is indentation? I don't understand the word ;-(
</>

It's an old C++ joke: "The road to perdition is paved with good
indentation". It means that you must set your tab width to zero.


#include<iostre am.h>
class Vector3D
{
public:Vector3D (double a,double b,double c):x(a),y(b),z( c)
{
cout<<"\nVector 3D("<<x<<','<<y <<','<<z<<") created...";
}
public:const Vector3D&operat or+=(const Vector3D&a)
{
x+=a.x;
y+=a.y;
z+=a.z;
return*this;
}
friend const Vector3D operator+(const Vector3D&a,cons t Vector3D&b)
{
return Vector3D(a.x+b. x,a.y+b.y,a.z+b .z);
}
protected:doubl e x,y,z;
};
int main()
{
Vector3D a=Vector3D(1,2, 3);
Vector3D b=Vector3D(4,5, 6);
Vector3D c=Vector3D(0,0, 0);
c+=a+b;
return 0;
}
____________
output:
Vector3D(1,2,3) created...
Vector3D(4,5,6) created...
Vector3D(0,0,0) created...
Vector3D(5,7,9) created...

-X

[Guest]

Re: operation overloading headache

> It means that you must set your tab width to zero.

Zero tab width???!!!
You mean this
----
while (1)
{
doit();
}
----
instead of this?
----
while(1)
{
doit();
}
----
Never!!!

In the code below, why you use inline functions?
[color=blue]
> #include<iostre am.h>
> class Vector3D
> {
> public:Vector3D (double a,double b,double c):x(a),y(b),z( c)
> {
> cout<<"\nVector 3D("<<x<<','<<y <<','<<z<<") created...";
> }
> public:const Vector3D&operat or+=(const Vector3D&a)
> {
> x+=a.x;
> y+=a.y;
> z+=a.z;
> return*this;
> }
> friend const Vector3D operator+(const Vector3D&a,cons t Vector3D&b)
> {
> return Vector3D(a.x+b. x,a.y+b.y,a.z+b .z);
> }
> protected:doubl e x,y,z;
> };
> int main()
> {
> Vector3D a=Vector3D(1,2, 3);
> Vector3D b=Vector3D(4,5, 6);
> Vector3D c=Vector3D(0,0, 0);
> c+=a+b;
> return 0;
> }
> ____________
> output:
> Vector3D(1,2,3) created...
> Vector3D(4,5,6) created...
> Vector3D(0,0,0) created...
> Vector3D(5,7,9) created...
>
> -X
>
>
>[/color]

[Agent Mulder]

Re: operation overloading headache

<- Chameleon ->[color=blue]
> Zero tab width???!!!
> You mean this
> ----
> while (1)
> {
> doit();
> }
> ----
> instead of this?
> ----
> while(1)
> {
> doit();
> }
> ----
> Never!!![/color]
</>

Try

while(1)doit();

-X

[Kevin Goodsell]

Re: operation overloading headache

Peter van Merkerk wrote:
[color=blue]
> temporary objects will be
> automatically destroyed after the expression which caused them to be created
> has been fully evaluated.[/color]

After the *full expression* is finished. A full expression is an
expression which is not part of a larger expression.

-Kevin
--
My email address is valid, but changes periodically.
To contact me please use the address from a recent posting.

[Jacek Dziedzic]

Re: operation overloading headache

"<- Chameleon ->" <cham_gss@hotma il.NOSPAM.com> wrote in
message news:bki9sl$ril $1@nic.grnet.gr ...[color=blue]
> [...]
> What is indentation? I don't understand the word ;-(
> [...][/color]

Inserting spaces and tabs into source code so that it's
more readable.

// code with no indentation
for(int k=0;k<3;k++)
{std::cout<<k<< std::endl;
for(int l=k;l<5;l++)
{std::cout<<k*l <<std::endl;};} ;

// code with indentation
// how exactly you do it is a matter of personal taste,
// so others might indent it very differently but I don't care
for(int k=0;k<3;k++) {
std::cout << k << std::endl;
for(int l=k;l<5;l++) {
std::cout << k*l << std::endl;
};
};

HTH,
- J.