C / C++ / MFC Discussion Boards

Jon Hulatt20-Jan-02 21:58

20-Jan-02 21:58

ok. saying "n5 -=" is equivalent to saying "n5=n5-". the rest of it is down to operator precedence. see "operator presecence" in MSDN.

but, you can make that expression clearer by writing it like this:

n5=n5- 7 + (2 / (3 *10)) ;

why? because in VC++, / has higher precedence that +

the second expression:

f2= 10.0 - (18.0 / (-3.0 * 2.5e-1));

In both cases, i suspect you're getting a different answer than you intended, due to operator precedence. It's good practise to always specify precedence with ()'s.

Sorry to dissapoint you all with my lack of a witty or poignant signature.

Re: Arithmetic Expression

Christian Graus20-Jan-02 22:08

Christian Graus

20-Jan-02 22:08

Jon Hulatt wrote:
n5=n5- 7 + (2 / (3 *10)) ;

This is wrong. It evaluates as I said in the lounge - 2 gets divided by 3 and the result multiplied by 10, so that part comes to zero ( because 2 and 3 are not floats ), but if it gets made 2.0 and 3.0, you get 6.666(10 * .66666), not 0.0666 (2/30). / and * have equal precedence, left to right.

So the correct way to use brackets to show order of operation is

7 + ((2/3)*10)

and the 2 and 3 should be floats in order to get an answer other than 7.

Also, are you recommending not using -= here, or am I misreading you ?

Jon Hulatt wrote:
f2= 10.0 - (18.0 / (-3.0 * 2.5e-1));

Again, this is wrong - put it into a console application and see for yourself. The result is 11.5, not 34 as your bracketing would evaluate to.

Christian

I have come to clean zee pooollll. - Michael Martin Dec 30, 2001

Sonork ID 100.10002:MeanManOzI live in Bob's HungOut now

Re: Arithmetic Expression

Jon Hulatt21-Jan-02 1:54

Jon Hulatt

21-Jan-02 1:54

That'll teach me to read the doc's more carefully. I forgot that * and / had equal precedence, in left-to-right order.

I wasn't recommending not using -= at all. from the guys original post it wasn't clear exactly what he was having trouble with.

Anyway, my incorrect answer to the question highlights why it's a good idea to always enforce your own precedence using ()'s. Especially if you use different languages frequently where precedence varies.

Smile | :)

Sorry to dissapoint you all with my lack of a witty or poignant signature.

Re: Arithmetic Expression

Christian Graus21-Jan-02 5:45

Christian Graus

21-Jan-02 5:45

Jon Hulatt wrote:
Anyway, my incorrect answer to the question highlights why it's a good idea to always enforce your own precedence using ()'s. Especially if you use different languages frequently where precedence varies.

Absolutely - I use a lot of brackets especially in the case mentioned, where a multiply happens after a divide. It's always better to have brackets show what you assume will happen, just in case your assumption is wrong.

Christian

I have come to clean zee pooollll. - Michael Martin Dec 30, 2001

Sonork ID 100.10002:MeanManOzI live in Bob's HungOut now

Arithmetic

Geoffrey20-Jan-02 17:36

Geoffrey

20-Jan-02 17:36

Could anyone help me with the following expressions?

n5-=7+2/3*10

and also

f2=10.0-18.0/-3.0*2.5e-1

Geoffrey A Overley

Re: Arithmetic

Christian Graus20-Jan-02 17:47

Christian Graus

20-Jan-02 17:47

Geoffrey, while this question is probably better off here than in the lounge, it was general enough that I answered it there. Either way, please don't ask the same questions over and over, once here is enough.

Christian

I have come to clean zee pooollll. - Michael Martin Dec 30, 2001

Sonork ID 100.10002:MeanManOzI live in Bob's HungOut now

Best wat to download a file with http?

Jay Beckert20-Jan-02 16:35

Jay Beckert

20-Jan-02 16:35

What is the best way to download a file with http protocol and actually test to see if that file really does exist? I have looked and looked to no avail. Any help will be greatly appreciated. Smile | :)

Bill? Who's this guy called Bill?

Re: Best wat to download a file with http?

Michael Dunn20-Jan-02 16:55

Michael Dunn

20-Jan-02 16:55

Use URLDownloadToFile().

--Mike--
"Why you keep calling me Jesús? I look Puerto Rican to you?"
-- Samuel L. Jackson in Die Hard 3
My really out-of-date homepage
Sonork - 100.10414 AcidHelm
Big fan of Alyson Hannigan.

Re: Best wat to download a file with http?

Jay Beckert20-Jan-02 16:59

Jay Beckert

20-Jan-02 16:59

lol Why is it always the obvious things we overlook?
I used OpenURL() but no real way of checking if it exist or not; Unless I make it a complicated task.

Thanks Mike Smile | :)

CopyMemory problems

alex.barylski20-Jan-02 12:59

alex.barylski

20-Jan-02 12:59

Can some one tell me what the problems is...?

LPCTSTR GetBuffer()
{
LPSTR buff = "";
CopyMemory(buff, GlobalLock(m_hBuffer), m_nSize);
GlobalUnlock(m_hBuffer);
return buff;
}

CopyMemory fails!!! I've managed to use similar code for the SetBuffer function.

CopyMemory(GlobalLock(m_hBuffer), buff, m_nSize);

Why does the one work and not the other...?

TIA Confused | :confused:

"An expert is someone who has made all the mistakes in thier field" - Niels Bohr

Re: CopyMemory problems

alex.barylski20-Jan-02 13:28

alex.barylski

20-Jan-02 13:28

I've fixed the problem, but i dunno if it's a proper fix.

LPCTSTR buff = (LPCTSTR)GlobalLock(m_hBuffer);
GlobalUnlock(m_hBuffer);
return buff;

I'm assuming the prob was that the temp buff is destroyed when outta scope...? So the CopyMemory had no effect. ultimately all i wanted returned was an address to the buffer and the above does this. However Locking the handle returns a pointer, doesn't Unlocking invalidate the handle...?

The above code works, but isn't it set up for failure, i'm kinda lost as to why it does work...? Confused | :confused:

Each Lock increments a counter kinda like COM objects right..? as the Unlock does the opposite, as long as the lock count is zero shouldn't it fail...?

Thanx again!

"An expert is someone who has made all the mistakes in thier field" - Niels Bohr

put images on GDI

DiegoValdevino20-Jan-02 12:54

DiegoValdevino

20-Jan-02 12:54

How can I put a array that represents an image on my window. Have I to create a DC or something? Name of functions and explanations would be very nice.

Re: put images on GDI

Christian Graus20-Jan-02 13:03

Christian Graus

20-Jan-02 13:03

DO you mean an array of pixel values ? You can create a DIBSection and copy the data directly onto the bitmap if you want to. Any decent DIBSection wrapper will also have a draw function, so all you need to do is pass in the DC you get in OnPaint.

Christian

I have come to clean zee pooollll. - Michael Martin Dec 30, 2001

Sonork ID 100.10002:MeanManOzI live in Bob's HungOut now

TopMost Maximized Window?

DiegoValdevino20-Jan-02 12:50

DiegoValdevino

20-Jan-02 12:50

I have just started today with dirctx8 and I want to make a window in full screen mode. The DX SDK says to create a "topmost" window with WS_EX_TOPMOST.
I had my window topmost , but not Maximized.

How can I do it ?

ps: Without window borders!!!

Re: TopMost Maximized Window?

Andrew Peace20-Jan-02 14:39

Andrew Peace

20-Jan-02 14:39

I think you need to look in the SetCooperateLevel function (I think that's the name, anyway, or something like it). Also, it would be good advice to look at the DirectX sample progras, they are a gold mine.

--
Andrew.

create an owned popup window

20-Jan-02 12:18

How does one create an owned popup window?

If I use

CreateEx(NULL,
        AfxRegisterWndClass(CS_HREDRAW | CS_VREDRAW, 0, (HBRUSH)(COLOR_WINDOW + 1), 0),
        NULL,
        WS_POPUP | WS_VISIBLE | WS_BORDER,
        rect,
        pParent,
        1,
        NULL);

CreateEx fails to create a window

but, if I use

CreateEx(NULL,
        AfxRegisterWndClass(CS_HREDRAW | CS_VREDRAW, 0, (HBRUSH)(COLOR_WINDOW + 1), 0),
        NULL,
        WS_CHILD | WS_VISIBLE | WS_BORDER,
        rect,
        pParent,
        1,
        NULL);

CreateEx successfully creates a window, but it's visibility is limited to it's parent's client area.

My class is derived from CWnd, and I call CreateEx() in the constructor.

TIA

TA.

Re: create an owned popup window

24-Jan-02 15:18

Does noone use use CWnd::CreateEx() to create a popup window Confused | :confused:

why would CreateEx() fail when the WS_POPUP flag is used, but if I use the CreateWindowEx() API function, with the exact same parameters as above, the window is successfully created?
I am very confused, and in the 2 days since I posted the original question, I have not gotten an answer. maybe this forum is not as helpful as I have been told Cry | :((

Skin a window

The_Server20-Jan-02 12:12

The_Server

20-Jan-02 12:12

How can I skin a window?

for example: Title, Window client area, Tool Bar, Menues, Fonts, etc.

Every help needed links.

Mad | :mad:

Anything . . . Mad | :mad:

Please HELP ! ! !

A S A P.

Thanks.

Re: Skin a window

Christopher Lord20-Jan-02 12:32

Christopher Lord

20-Jan-02 12:32

You have to write a skin parser, drawing code to put it all in the right places (resize wigits, buttons, icons, etc).

After that, you have to link all these icons and buttons to actual functionality, send window-grip messages, and more.

Needless to say rewriting a UI is a lot of work.

// Rock

Re: Skin a window

Ravi Bhavnani20-Jan-02 12:44

Ravi Bhavnani

20-Jan-02 12:44

This should get you started:

/ravi

"There is always one more bug..."
http://www.ravib.com
ravib@ravib.com

Re: Skin a window ( * Explorer Window *)

The_Server20-Jan-02 13:31

The_Server

20-Jan-02 13:31

sorry 4 the mistake, guys.

But I meant: How can I skin an Explorer Window ?

Please HELP.

Thanks

Re: Skin a window ( * Explorer Window *)

Christopher Lord20-Jan-02 14:48

Christopher Lord

20-Jan-02 14:48

Window blinds....

It would be a lot of work otherwise (way WAY more than your own program) because you have to listen for draw messages from all over the place and do your own drawing once windows is done its thing.

Not prety, and not worth it since window blinds does all this for you already.

// Rock

Re: Skin a window ( * Explorer Window *)

The_Server20-Jan-02 19:20

The_Server

20-Jan-02 19:20

CLaW wrote:
window blinds does all this for you already

But I wanna do it and perfect some things...

BTW: come to #CodeProject on DalNet (mIRC)

Simple mp3 playback?

20-Jan-02 11:55

I have a program where I want an mp3 audio file played in the background at start up and repeated until the program is closed. For now though, I have a menu option which will start the playing of the mp3 (although it will still play in the background without the bar shown)

I added the following function which I got from this program here ( http://www.codeproject.com/audio/mp3player.asp#xx88328xx ), but I can't seem to get it working. I included the vfw.h and put VFW32.lib in the linker's space as well.

When I run this program I get a "memory could not be read" error.

void CChildView::OnPlay()
{
m_Video = NULL;
if(m_Video == NULL)
{
m_Video = MCIWndCreate(this->GetSafeHwnd(),
AfxGetInstanceHandle(),
WS_CHILD | WS_VISIBLE|MCIWNDF_NOMENU, m_Path);

}
else
{
MCIWndHome(m_Video);
}
MCIWndPlay(m_Video);
}

Am I using the wrong function for this or am I simply using the right function wrongly?
Confused | :confused:

Re: Simple mp3 playback?

Christian Graus20-Jan-02 11:59

Christian Graus

20-Jan-02 11:59

I dunno, but I use the mp3 playback source code in the 'simple skinnable app with mpeg playback' article for this sort of thing, it works a treat.

Christian

I have come to clean zee pooollll. - Michael Martin Dec 30, 2001

Sonork ID 100.10002:MeanManOzI live in Bob's HungOut now

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