C# Discussion Boards - CodeProject

myNameIsRon14-Jun-04 17:25

myNameIsRon

14-Jun-04 17:25

Hi,
I have code that subtracts two variables (type: double). The problem happends when both variables have the same value (should get 0)...
change = grandTotal - totalPayments;
but result is: 1.4210854715202E-14
(found that out with the MessageBox)

It's mucking up my if statement:
if (change > 0)

thanks,
Ron

Colin Angus Mackay14-Jun-04 23:36

Colin Angus Mackay

14-Jun-04 23:36

doubles are not accurate they will often contain rounding errors.

You should used double.Epsilon to deal with it.

For example code to test equality should do something like this:

if (Math.Abs(testValueA - testValueB) <= double.Epsilon)
{
    // Treat as equal
}

So your if statement could be something like:

if (change > double.Epsilon)
{
    // Do stuff
}

Does this help?

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myNameIsRon15-Jun-04 20:05

myNameIsRon

15-Jun-04 20:05

Thanks Colin,
I didn't realize that double would be so buggy.

Ron

Colin Angus Mackay15-Jun-04 20:30

Colin Angus Mackay

15-Jun-04 20:30

myNameIsRon wrote:
I didn't realize that double would be so buggy

Its not buggy - That how double works. As the precision of floating point operations on processors increases the problem will decrease, but it will never go away completely.

Serge Lobko-Lobanovsky15-Jun-04 1:34

Serge Lobko-Lobanovsky

15-Jun-04 1:34

Are you working with money (I can guess it from the variables)? So why use Double if you could use Decimal type for money.

Just my 1 cent Smile | :)

Regards,
Serge (Logic Software, Easy Projects .NET site)

myNameIsRon15-Jun-04 20:08

myNameIsRon

15-Jun-04 20:08

Hi Serge,
Thanks, I thought that double would be sufficient...
but I guess not! Using decimal fixes the problem Blush | :O

)

Ron

Serge Lobko-Lobanovsky15-Jun-04 21:20

Serge Lobko-Lobanovsky

15-Jun-04 21:20

Hi Ron,

As far as I know, Decimal is the replacement for Currency data type that was in COM before, and it naturally fits in SQL Server's money datatype.

Regards,
Serge (Logic Software, Easy Projects .NET site)

C# Application is Error

GuruVN14-Jun-04 17:15

GuruVN

14-Jun-04 17:15

Dir sir
+. I'm using FAXCOMLib and C#.net for developing an application.
+. In my Application I have send a fax. But when I click button SendFax
I recevice an Error: "The handle is invalid"
What should I do ?

using winuser.h

eggie514-Jun-04 16:09

14-Jun-04 16:09

I was messing around with this code to hide my taskbar

ShowWindow(FindWindow("Shell_TrayWnd", NULL), SW_HIDE);

I think it's C or C++, but I really don't know... anyways to make it work in my C# app I just put in 0, instead of SW_HIDE. I know SW_HIDE is in winuser.h and equals 0, so thats why I put 0...

So, my question... I feel like i'm cheating "hard coding" a 0. I would like to know how to use SW_HIDE and other things such as -- SW_SHOWNORMAL, SW_MAX etc. in winuser.h -- in my C# program the correct way.

/\ |_ E X E GG

Mazdak14-Jun-04 19:49

Mazdak

14-Jun-04 19:49

They are usually just int variables , so you can do it like this:

private int SW_HIDE = 0;

Mazy

"One who dives deep gets the pearls,the burning desire for realization brings the goal nearer." - Babuji

eggie514-Jun-04 19:59

14-Jun-04 19:59

yeah, that's what i'm doing right now...

/\ |_ E X E GG

Heath Stewart15-Jun-04 2:45

Heath Stewart

15-Jun-04 2:45

You should actually declare them as consts. When it comes down to it, that's all they really are in C/C++ - constants. Since they're pre-proc definitions, they can't be changed by code. The value is actually inserted.

When you declare them as consts, the value is actually used as well. Those values will never change, and using consts is faster.

You can also use enums, which is another common way (but often requires casting to an int or something). The values of the enum are also used in place of a reference (they're value types).

That's just the way it is.

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eggie515-Jun-04 5:55

15-Jun-04 5:55

t h a n k s

/\ |_ E X E GG

Dave Kreskowiak15-Jun-04 2:52

Dave Kreskowiak

15-Jun-04 2:52

Since you cant use C++ .H files in C#, you have to recode the structures and constants you need from the header files into C# code. Just like Mazy showed you...

RageInTheMachine9532
"...a pungent, ghastly, stinky piece of cheese!" -- The Roaming Gnome

eggie515-Jun-04 5:53

15-Jun-04 5:53

like sorta make a class library out of them?

/\ |_ E X E GG

Adding .wmf to an RTF file...

Dave Kreskowiak15-Jun-04 14:49

Dave Kreskowiak

15-Jun-04 14:49

You could. Then in that library, you make the function declarations static so you don't have to instantiate the class in order to use the functions.

RageInTheMachine9532
"...a pungent, ghastly, stinky piece of cheese!" -- The Roaming Gnome

sachinkalse14-Jun-04 14:54

sachinkalse

14-Jun-04 14:54

If I insert .wmf file to an RTF file programatically Or simply by 'opening that RTF file and insert picture' way, it works fine. But when I select the image and try to compress or enlarge it, the line width of the image changes. How to avoid that? I want to make the widh of lines FIX.
Please guide

Heath Stewart15-Jun-04 2:42

Heath Stewart

15-Jun-04 2:42

What do you mean by "lines"? An image - such as a .wmf - takes up a block of space, not lines. When you change the size of the image, the lines above and below it (perhaps beside it as well, if there's any wrapping) will move, too. This is true even in Word unless you change a lot of settings that aren't available in RTF.

If you want to learn about the RTF codes that you could try to fanagle, read the RTF 1.7 Specifications, available for download at http://www.microsoft.com/downloads/details.aspx?FamilyID=e5b8ebc2-6ad6-49f0-8c90-e4f763e3f04f&DisplayLang=en[^].

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sachinkalse15-Jun-04 15:06

sachinkalse

15-Jun-04 15:06

Thanks for the reply. I am reading RTF 1.8 Specification.
Let me re arrange my words, "Lines" means, lets say I draw a simple line in .wmf file and add that to RTF document. When I open the document and select .wmf image with the help of mouse and enlarge it, the size (width and height) of the rectangle (i.e. wmf image) increases that is acceptable but at the same time the line's width also increases, it becomes fat. Can we not control it at the time of creation of .wmf image?
sorry for messy description D'Oh! | :doh:

Heath Stewart16-Jun-04 3:09

Heath Stewart

16-Jun-04 3:09

That's what's supposed to happen. WMF is a vector graphic, meaning, basically, that the instructions to draw shapes is stored, not the shapes themselves. This is so that proportionally the graphic looks the same at any resolution.

Now, there may be a way to draw a rasterized shape (rendered) but I really don't know.

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