C / C++ / MFC Discussion Boards

Re: address of constant

George_George18-Nov-07 4:21

George_George

18-Nov-07 4:21

Thanks Roger,

My question is answered.

regards,
George

Re: address of constant

Iain Clarke, Warrior Programmer14-Nov-07 23:31

Iain Clarke, Warrior Programmer

14-Nov-07 23:31

George-so-good-you-named-yourself-twice,

As has been said, the answer depends on compiler flags. But I would strongly pretend to yourself that the answer is impossible to know, and not depend on it.

If you want two pointers to the same place, be explicit about it. Or some person who changes your code in three years (ie, you) will have no idea you intended them to be the same, and will break things.
Or you will upgrade to Visual Studio 2020 (in the year 2012) and the compiler will do different things and you'll get nasty to find bugs.

To save this you'll have to write more comments than the effort is worth.

Iain.

Re: address of constant

George_George18-Nov-07 4:24

George_George

18-Nov-07 4:24

Thanks for your advice, Iain!

I agree that your idea will make code more safe and conforming to standard -- by not assuming any non-language-standard points. Smile | :)

regards,
George

FFT CODE

itsgood12314-Nov-07 19:47

itsgood123

14-Nov-07 19:47

Hi ALL,

Can please anyone give me the code in vc++ to calculate FFT?I have the gray values of the image as input in array form.

Please help me.I really need it ASAP.I would really appreciate it.

Thanks & Regards

Re: FFT CODE

Nelek14-Nov-07 20:28

Nelek

14-Nov-07 20:28

The forum usually is to ask questions, I don't think the people here is going to give ready codes without questions. Have you at least used google to search? Most probably there will somewhere be available code to do that.

Greetings.

--------
M.D.V.

If something has a solution... Why do we have to worry about?. If it has no solution... For what reason do we have to worry about?

Help me to understand what I'm saying, and I'll explain it better to you

“The First Rule of Program Optimization: Don't do it. The Second Rule of Program Optimization (for experts only!): Don't do it yet.” - Michael A. Jackson

Wink | ;)

Re: FFT CODE

Rajesh R Subramanian14-Nov-07 20:50

Rajesh R Subramanian

14-Nov-07 20:50

raavn wrote:
I really need it ASAP.

Asking for free help and wanting it ASAP is rude. You are abusive in my opinion.

Re: FFT CODE

itsgood12315-Nov-07 8:03

itsgood123

15-Nov-07 8:03

Please do not take it in negative sense.
I was really in need of it.

If you would be in such a need,then only you can understand.

Re: FFT CODE

Nelek15-Nov-07 20:35

Nelek

15-Nov-07 20:35

We understand it, but you don't understand, that the "high level" users (and I'm not including me, I'm just a bit more than a begginer), that most of times help answering the questions, are pissed off about ASAP, URGENT, and such expressions, the first message of all (Chris Maunders) is there for a very clear reason.

On the other hand, if someone reads your message and knows the answer you will have it. If not... you won't have it. Is pretty useless that you write ASAP, it depends on when your message is read, if the reader knows the answer, if your message don't annoy the reader avoiding the answer and many other factors.

And as you can see below... If you just need code or examples about something, Google can sometimes do miracles. Other question is if you don't understand something, then you will logically have to ask.

BTW and for your info... The most of the URGENT, VERY NEEDED, ASAP and so on, is from people that left the work for the last moment and, then, OOOOHHHH the world is ending, I don't know how to continue.

Just a few % of the urgent questions, are things not depending on the asker. It maybe is not right, that innocent people pays for the errors of the others...

but as you ask to be understood in your hurry, this is to make you understand the other side. And the reason for some comments.

Greetings.

--------
M.D.V. Wink | ;)

If something has a solution... Why do we have to worry about?. If it has no solution... For what reason do we have to worry about?

Help me to understand what I'm saying, and I'll explain it better to you

“The First Rule of Program Optimization: Don't do it. The Second Rule of Program Optimization (for experts only!): Don't do it yet.” - Michael A. Jackson

Re: FFT CODE

jhwurmbach14-Nov-07 23:29

jhwurmbach

14-Nov-07 23:29

raavn wrote:
Can please anyone give me the code in vc++ to calculate FFT?

http://faculty.prairiestate.edu/skifowit/fft/[^]
which happens to be the first entry in
http://www.mathtools.net/C_C__/FFT/index.html[^]

Google can be your friend, too!

Let's think the unthinkable, let's do the undoable, let's prepare to grapple with the ineffable itself, and see if we may not eff it after all.
Douglas Adams, "Dirk Gently's Holistic Detective Agency"

Re: FFT CODE

Iain Clarke, Warrior Programmer14-Nov-07 23:39

Iain Clarke, Warrior Programmer

14-Nov-07 23:39

Have you tried searching google?
http://www.google.com/search?hl=en&q=c+source+code+fft&btnG=Search

Or even a website where there are many articles using code?

http://www.codeproject.com/info/search.asp then type in fft. Lot's of articles there...

Iain.

Re: FFT CODE

itsgood12315-Nov-07 8:01

itsgood123

15-Nov-07 8:01

Thanks for replying.

I am really very thankful to you all.

Re: FFT CODE

Paul Conrad23-Dec-07 15:08

Paul Conrad

23-Dec-07 15:08

raavn wrote:
Can please anyone give me the code in vc++ to calculate FFT?

Nope.

"The clue train passed his station without stopping." - John Simmons / outlaw programmer

Correct "Window Data Types"

CodingLover14-Nov-07 19:47

CodingLover

14-Nov-07 19:47

hi all,

I have a struct define as follows, defines on the 32bit machine.

<br />
struct pac_cont <br />
{<br />
	unsigned int des_list;	<br />
	unsigned int mem_ID;	<br />
	unsigned char dm_con;	<br />
	unsigned char ser_ID;	<br />
	unsigned short act;	<br />
};<br />

This is one of very important part of my application, and I want to keep this structure as it is on any windows system without any issue. So I think it is better to use Windows Data Types. I defined it as follows.

<br />
struct pac_cont<br />
{<br />
	DWORD32 des_list;	<br />
	DWORD32 mem_ID;		<br />
	CHAR	dm_cont;		<br />
	CHAR	ser_ID;		<br />
	SHORT	act;		<br />
};<br />

Is it correct.

I appreciate your help all the time...
Eranga Smile | :)

Re: Correct "Window Data Types"

Roger Broomfield14-Nov-07 20:21

Roger Broomfield

14-Nov-07 20:21

Surely this is going to depend on how your headers typedef them, specifically winnt.h and basetsd.h, and how your compiler interprets the inbuilt types? Once your code is compiled the windows system on which your code is used wont make any difference. Even if you change the structure as you propose and use it with a 32bit compiler and then later port your code to a 64 bit compiler, you will still have to check that the typedefs havent changed and that the inbuilt types are the same as before, also you will have to check that default structure packing hasnt changed.

Ohh and current headers "typedef short SHORT;" so your act member has changed type already.

Re: Correct "Window Data Types"

CodingLover14-Nov-07 21:45

CodingLover

14-Nov-07 21:45

Roger Broomfield wrote:
Ohh and current headers "typedef short SHORT;" so your act member has changed type already.

I'm not clear what you say.

I appreciate your help all the time...
Eranga Smile | :)

Re: Correct &quot;Window Data Types&quot;

Nelek14-Nov-07 22:20

Nelek

14-Nov-07 22:20

unsigned short != short

so...

unsigned short != SHORT

so...

you have already change the type of the datas using SHORT

Re: Correct &quot;Window Data Types&quot;

CodingLover14-Nov-07 22:54

CodingLover

14-Nov-07 22:54

That mean, I can't change unsigned short act; as SHORT act;

Ok, I think I have to read more about this. Sigh | :sigh:

I appreciate your help all the time...
Eranga Smile | :)

Re: Correct &quot;Window Data Types&quot;

Nelek15-Nov-07 0:18

Nelek

15-Nov-07 0:18

You can, but you will already have a change of the typ. If you DO need a unsigned short... then you can not use SHORT. At least that is what I guess after reading Roger's answer

Re: Correct &quot;Window Data Types&quot;

CodingLover15-Nov-07 0:43

CodingLover

15-Nov-07 0:43

Hmmm,

Anyhow I have to use unsigned char, to keep the struct variables sizes. Otherwise the application gives wrong output.

I appreciate your help all the time...
Eranga Smile | :)

Re: Correct &quot;Window Data Types&quot;

Nelek15-Nov-07 23:59

Nelek

15-Nov-07 23:59

then... why dont you make your own typedef? I think unsigned short is standard and portable to all platforms. About the other types... read the answers below, they speak with more knowledge than me

Greetings.

--------
M.D.V. Wink | ;)

Re: Correct "Window Data Types"

BadKarma14-Nov-07 22:40

BadKarma

14-Nov-07 22:40

There is no such thing as Windows Data Types.

There are only the c++ data types (when working in c++ Poke tongue | ;-P

) which are
char, short, int, long, long long. All of them can be signed, unsigned or undefined (which means signed).
char = 1 byte ( 8 bit)
short = 2 byte (16 bit)
long = 4 byte (32 bit)
long long = 8 byte (64 bit)
int = natural size of adressing on 32 bit platforms this will be 4 byte. on other platforms this could be smaller or larger. Alsoo this size can change from compiler to compiler. Apperantly MS has defined that a int will always be 32 bit.

From basetsd.h

//
// The following types are guaranteed to be unsigned and 32 bits wide.
//

typedef unsigned int ULONG32, *PULONG32;
typedef unsigned int DWORD32, *PDWORD32;

When using struct especialy use known size type, which means never use int! That way this piece of code can work cross-platform, cross-compiler.

codito ergo sum

Re: Correct "Window Data Types"

CodingLover14-Nov-07 22:51

CodingLover

14-Nov-07 22:51

Yep, thats what I really want. I want to use this code on any Windows platform without any use, but the develop based on 32 bit system.

BadKarma wrote:
There is no such thing as Windows Data Types.

Say I have two variables,

<br />
int32 i = 10;<br />
<br />
DWORD32 j = 12;<br />

Can I use both i and j on Windows?
My answer is "yes"

Can I use both i and j on Linux?
My answer is "no". Because DWORD32 is a Windows Data Type

Is that correct.

I appreciate your help all the time...
Eranga Smile | :)

Re: Correct "Window Data Types"

BadKarma14-Nov-07 23:35

BadKarma

14-Nov-07 23:35

Eranga Thennakoon wrote:
My answer is "no". Because DWORD32 is a Windows Data Type

Is that correct.

No.

I Repeat :

BadKarma wrote:
There is no such thing as Windows Data Types.

DWORD32 is typedefed as an unsigned 32bit integer. This means one thing: the compiler treats the variables the same. You can simply make your own aliasses to known types, like this:

typedef unsigned long MYLONG;

DWORD32 is defined in basetds.h as

typedef unsigned int DWORD32;

this means you can either use:

struct A
{
  unsigned int data;
};

struct A
{
  DWORD32 data;
};

there will be no difference for the compiler.
This means that you should be able to use this struct also on a unix compiler. However MS has set the size of theire int to be fixed 4 bytes (IMHO a mistake). So this could break your cross-platform, cross-compiler compatibility. Use a long instead of an int. It is always better to use the full names of the datatypes then the Typedefed ones.

codito ergo sum

Re: Correct "Window Data Types"

jhwurmbach14-Nov-07 23:35

jhwurmbach

14-Nov-07 23:35

DWORD32 is a datatype typedefed (or preprocessor-defined) in Windows.
In linux, you may or may not have those types defined.
So, the best thing you could do is add a header to your code where you define the types you need for every platform you support.

Re: Correct "Window Data Types"

Iain Clarke, Warrior Programmer14-Nov-07 23:46

Iain Clarke, Warrior Programmer

14-Nov-07 23:46

You're still missing a pretty obvoious point.

int 32 = 10;
DWORD32 j = 32;

Look at the definition for DWORD32, and you'll end up with the keyword unsigned.

Try
int32 i = -10;
DWORD32 j = -32;

As for the structure sizes, BadKarma already told you the definition of them.

The only thing that hasn't been fully explained is packing sizes.

Compilers usually space out variables in a structure to make it easier to address them. So the individual variables of your structure may have the same size, but you'll have gaps in between them.

Do a search for
#pragma pack (push, 1)
and
#pragma pack (pop)

for more detail.

Iain.
in a program and see the results.

Use Ctrl+Left/Right to switch messages, Ctrl+Up/Down to switch threads, Ctrl+Shift+Left/Right to switch pages.