C / C++ / MFC

Re: How to struct AA{ struct BB; }; struct BB { struct AA; };

2-Jul-08 22:09

Chesnokov Yuriy wrote:
aa.bb->b = 1; //error???? Ahhhh

Should be as follows:

aa->bb->b = 1;

Steve

CPallini2-Jul-08 22:19

CPallini

2-Jul-08 22:19

You have a lot of patience, man. My 5.
Smile | :)

If the Lord God Almighty had consulted me before embarking upon the Creation, I would have recommended something simpler.
-- Alfonso the Wise, 13th Century King of Castile.

This is going on my arrogant assumptions. You may have a superb reason why I'm completely wrong.
-- Iain Clarke

[My articles]

Re: How to struct AA{ struct BB; }; struct BB { struct AA; };

Chesnokov Yuriy2-Jul-08 22:34

Chesnokov Yuriy

2-Jul-08 22:34

No way

AA aa;
aa->bb??? how can you access with -> object on stack not a pointer??

the glitch is

struct BB;
typedef struct _AA {
struct BB* bb;
int a;
} AA, *PAA;

typedef struct _BB {
struct AA* aa;
int b;
} BB, *PBB;

that one works but you can not access bbs constents from AA nor vice versa?

chesnokov

Re: How to struct AA{ struct BB; }; struct BB { struct AA; };

Stephen Hewitt2-Jul-08 22:37

Re: How to struct AA{ struct BB; }; struct BB { struct AA; };

2-Jul-08 22:37

Yeah, you're right. So what's your problem exactly?

Steve

Chesnokov Yuriy2-Jul-08 23:05

Chesnokov Yuriy

2-Jul-08 23:05

to compile and run that code:

struct BB;
typedef struct _AA {
struct BB* bb;
int a;
} AA, *PAA;

typedef struct _BB {
struct AA* aa;
int b;
} BB, *PBB;

main()
{
AA a;
BB b;
a.bb = &b;
b.aa = &a;
a.bb->b = 1;
b.aa->a = 3;
}

chesnokov

Re: How to struct AA{ struct BB; }; struct BB { struct AA; };

Stephen Hewitt6-Jul-08 14:56

Re: How to struct AA{ struct BB; }; struct BB { struct AA; };

6-Jul-08 14:56

This works fine for me:

// StraightC.cpp : Defines the entry point for the console application.
//
 
#include "stdafx.h"
 
struct BB;
 
struct AA
{
	struct BB* bb;
	int a;
};
 
struct BB
{
	struct AA* aa;
	int b;
};
 
void main()
{
	struct AA a;
	struct BB b;
	a.bb = &b;
	b.aa = &a;
	a.bb->b = 1;
	b.aa->a = 3;
}

Steve

Iain Clarke, Warrior Programmer2-Jul-08 22:24

Re: How to struct AA{ struct BB; }; struct BB { struct AA; };

2-Jul-08 22:24

You're having trouble with them being declared as pointers, and want them as real contained structs.

To borrow a phrase, "Imagine if you could do what you're asking".

AA would contain a BB which would contain an AA which would contain a BB which would contain an AA which would contain a BB which would contain an AA which would contain a BB which would contain an AA which would contain a BB which would contain an AA which would contain a BB which would contain an AA which would contain a BB which would contain an AA which would contain a BB...

I hope I'm getting the point across - I'm bored of typing. But your structure would end up infinitely large.

You can contain a *pointer* to your structures evil twin - a pointer only takes up a few bytes. But you need to give the pointer something to point to.

So:

struct BB;

struct AA
{
    struct BB *bb;
    int a;
};
struct BB
{
    struct AA *aa;
    int b;
};

main ()
{
    AA a;
    BB b;

    a.bb->b = 1;   // Will compile, but will crash horribly, because a.bb doesn't have any useful value in it.
}

In the above example, C isn't psychic, so hasn't pointed A.bb at any BB structure. How can it? That's your job.

Try the below code.

AA a;
BB b;

a.bb = &b;
b.aa = &a;

a.bb->b = 1;
b.aa->a = 3;

Now your two structure can talk to each other to their heart's content.

I'd go back to your C book, and look up linked lists - it'll give you a light bulb moment about pointers.

Iain.

Plz sir... ^CPallini ^CPallini abuz drugz, plz plz help urgent.

CPallini2-Jul-08 22:28

CPallini

2-Jul-08 22:28

Iain Clarke wrote:
I'd go back to your C book

If any.

Re: How to struct AA{ struct BB; }; struct BB { struct AA; };

Chesnokov Yuriy2-Jul-08 22:38

Chesnokov Yuriy

2-Jul-08 22:38

Do not push to other limits I know to self refere them in future the glitch is it does not compile??
Try it yourself:

AA a;
BB b;
a.bb = &b;
b.aa = &a;
a.bb->b = 1; //error C2037
b.aa->a = 3; //error C2037

chesnokov

Re: How to struct AA{ struct BB; }; struct BB { struct AA; };

Iain Clarke, Warrior Programmer2-Jul-08 22:49

2-Jul-08 22:49

My apologies, I hadn't fully switched off my C++ brain.

try:

struct AA a;
struct BB b;
a.bb = &b;
b.aa = &a;
a.bb->b = 1; //Just fine!
b.aa->a = 3; //Just fine!

Though you could have worked that out for yourself...

Iain.

Plz sir... ^CPallini ^CPallini abuz drugz, plz plz help urgent.

CPallini2-Jul-08 23:06

CPallini

2-Jul-08 23:06

Iain Clarke wrote:
Though you could have worked that out for yourself...

Another hint the C book was lost sometime.
Smile | :)

Help with CTabCtrl

rbmarasigan20012-Jul-08 20:42

rbmarasigan2001

2-Jul-08 20:42

Good day Guys,

Just would like to ask for help on this, how do I disable a tab in CTabCtrl?

I have a custom class extending CTabCtrl for some processing and also 3 Dialogs as Tabs.

On runtime, while processing on one tab, I would like to disable the other 3 tabs as not to mess
with the processing.

Thanks in advance

rbmarasigan2001

Re: Help with CTabCtrl

Iain Clarke, Warrior Programmer2-Jul-08 22:39

Re: GPL - and bullying hippy teachers.

2-Jul-08 22:39

My first thought was "what a lazy question! Just called CTabCtrl::EnableItem (n, FALSE), or SetStyle (some struct with enable flag turned off)"...

But neither CTabCtrl, or (more authoratively) appear to have any disable tab functionality.

In my software, I don't use CTabCtrl as such - I use CFolderTabCtrl written by Paul diLascia in October 2002's MSDN magazine. Lot's of nice goodies in it, which hopefully will help you. You may even find it has the functionality you've added yourself...

http://msdn.microsoft.com/en-us/magazine/cc188936.aspx[^]
Iain.

Plz sir... ^CPallini ^CPallini abuz drugz, plz plz help urgent.

GPL

Dennis L2-Jul-08 20:35

Dennis L

2-Jul-08 20:35

Hi every one!

I have started a project using ciphering. That is going to be my last project in my school!
My teacher has told me this project is going to be published with no fee in the internet.

I want to use RSA and SHA1 taken by XYSSL Cristophe's Devine project (you may know : www.xyssl.org)
and make some modifications. How can do it so as to make it by low?

Also: What does it mean XYSSL having GPL license?

thanks!

Re: GPL

Hamid_RT2-Jul-08 21:31

Hamid_RT

2-Jul-08 21:31

See here[^] Im not sure its helpful for you or no?

Re: GPL

Dennis L2-Jul-08 21:54

Dennis L

2-Jul-08 21:54

Thanks for your reply!

Iain Clarke, Warrior Programmer2-Jul-08 23:20

2-Jul-08 23:20

Dennis L wrote:
My teacher has told me this project is going to be published with no fee in the internet.

Not really a programming answer, but this seems a bit wrong to me. Surely this is work that you will create - it's valid for your teacher to mark it, and maybe keep confidential copies for reference in case someone challenges her marks - but why does she have a right to give your work to the world?

If *you* allowed it to be published to the world, then great. I've written some articles here, and am happy to give back to the greater community. But I'd be peeved if I had no choice about it.

Would you fail if you handed in the code with "Copyright Dennis L, not GPL, not using GPL, and not to be published without permission" on the top of every page?

Saying that, if you use GPL components, their license will infect your code too, I suppose.

Iain.

Plz sir... ^CPallini ^CPallini abuz drugz, plz plz help urgent.

header-files

testcrap2-Jul-08 20:03

testcrap

2-Jul-08 20:03

I have problems compiling my project.
There a two header-files:

the first one, ClassA.h:

#include "ClassB.h"
class ClassA
{
...
private:
ClassB classB;
...
}

and the second, ClassB.h:

#include "ClassA.h"
class ClassB
{
...
private:
ClassA classA;
...
}

So ClassA requires ClassB and ClassB requires ClassA.
The Compiler doesnt semm to like this kind of cross-requirements.
How can i solve this problem?

Stephen Hewitt2-Jul-08 20:13

2-Jul-08 20:13

The way you're going about things doesn't make sense if you think about it. If Class A contains an instance of Class B and Class B contains an instance of Class A you've got something akin to infinite recursion. Perhaps this diagram will clarify this:

Class A
{
    Class B
    {
        Class A
        {
            Class B
            {
                Class A
                {
                    .
                    . // etc...
                    .
                }
            }
        }
    }
}

Steve

Stephen Hewitt2-Jul-08 21:04

2-Jul-08 21:04

Why vote down this you clowns? This post explains why the approach doesn't make sense and the next suggests a solution.

Steve

Iain Clarke, Warrior Programmer2-Jul-08 23:21

2-Jul-08 23:21

"Vote me down, and I shall become more popular than you can imagine!"

Maybe the thought of an infinite struct blew their minds?

Iain.

Plz sir... ^CPallini ^CPallini abuz drugz, plz plz help urgent.

Stephen Hewitt2-Jul-08 20:22

2-Jul-08 20:22

Perhaps something like this is what you're after:

In "ClassA.h":

// No need to include "class B"'s header.
 
class B; // Forward reference.
 
class A
{
...
private:
    ClassB &classB; // A reference to class B, not an instance.
};

In "ClassB.h":

// No need to include "class A"'s header.
 
class A; // Forward reference.
 
class B
{
...
private:
    ClassA &classA; // A reference to class A, not an instance.
};

Steve