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Hello, I have a strange problem, but probably it is because i am lacking knowledge, but what?
When debugging this:
double dTryThis = 1.23456789;
the debuggers variable watch shows this value for dTryThis:
1.234567889999999
instead of the expected 1.234567890000000!  And so is the wrong value used for further calculations! Is my computer sick or am I or what? I am on Visual Studio 2005 C++.
Thanks a lot for your help!
Martin...
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Floating point[^] numbers are represented as a fixed part (the mantissa) raised to an exponent. Both parts of the representation are necessarily binary numbers (i.e. every floating point number is the mantissa raised closest power of two ) As such, floating point numbers are always an approximation, with small values being closer together than large values (every time you increase the exponent, each bit in the mantissa becomes worth more).
What you are seeing is normal behavior for floating point numbers (double or single precision).
If you need a fixed precision, then you must use either integers (with a constant scaling factor),decimal[^] or currency, or some other exact numeric data type.
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Base10 numbers can't store all fractional values exactly without infinite repitition (1/3, 1/7, etc). Your computer uses base2 math internally and only converts to base10 for output. base2 can't store all numbers without repeating either. The thing you need to remember is that different bases have different sets of repeaters. In base3 1/3 is written as 0.1 (zero ones and one third), while in base10 1/3 is 0.3333333...... The base2/base10 one that causes the most confusion is 1/10 is a repeater in base2. You can work it out by hand if you want to see it with your own eyes. For financial transactions fixed point datatypes or types that store the number in a base10 format directly are typically used, but they have significant penalty over native base2 math. When precision identical to base10 hand work is not needed as long as it's good enough, native floating point types are used and a comparisons are made in a way that reflects the rounding issues. Instead of testinf equality by (f1-f2) == 0 you use Abs(f1-f2) < epsilon where epsilon is a delta smaller than your allowed error tollerance. If you're doing very extensive computations it's sometimes neccesary to order them in a way that minimizes total error, but normal applications generally don't need to worry about this.
for more detail see below. It's probably more detail than you need but is the best web reference I'm aware of.
http://docs.sun.com/source/806-3568/ncg_goldberg.html[^]
--
Rules of thumb should not be taken for the whole hand.
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Aaaah! Trying six hours on that issue, then waiting five minutes for your excellent answer! Thank you very much!  Martin...
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Hi all
I have a problem with scaling a bitmap in different DPI situations .
The problem is : I have a dialog box where a bitmap is statically present . So during runtime without calling LoadBitmap () this bitmap is loaded into the dialog with the default size which is same you see in dialog editor . But problem comes when I change system DPI from 96 to 120.
Now the dialog and all the controls behind the bitmap are resized while the bitmap remains the same. I tried to implement StretchBlt () to scale the bitmap to new size - I do not succeed as I do not know how to map it to new DPI . To pictorise it ...
................. <---- The parent dialog
. .
. |---------| .
. | |<-- Bitmap with original static size when DPI=96
. | | .
. | | .
. | | .
. | | .
. | | .
. |---------| .
. .
.................
Now what I want is , when I change DPI to 120 then it should resize itself *from* the top,left of original size to the new sized bitmap .
After implementing StretchBlt as below ..I got it stretched fully to windows limits not as I want ...
pBitmap->LoadBitmap(IDB_BITMAP_ADDON_10_NOE);
POINT ptSize;
GetClientRect(hDlg,&rect);
pBitmap->GetObject(sizeof(BITMAP), &bitmap);
ptSize.x = bitmap.bmWidth;
ptSize.y = bitmap.bmHeight;
fxFactor = ((float)ptSize.x/(float)(rect.right-rect.left)),
fyFactor = ((float)ptSize.y/(float)(rect.bottom-rect.top));
xOffs = ((long)rect.Width()-(long)(ptSize.x/fxFactor))/2;
yOffs = ((long)rect.Height()-(long)(ptSize.y/fyFactor))/2;
dc->StretchBlt(xOffs,
yOffs,
(long)(ptSize.x/fxFactor),
(long)(ptSize.y/fyFactor),
&dcTemp,
0, 0,
ptSize.x,
ptSize.y,
SRCCOPY);
Now we have the real width,height of the bitmap + the windows dimensions . I need the bitmap to be scaled evenly to the new dimension of dialog keeping this bitmap in the center of the dialog . So I need to calculate the coordinates of the new bitmap with following points
1) Coordinates of the windows( = Center point of window)
2) Height,Width of bitmap
Can anyone please advise me ?
redindian
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I think you're better off posting this in the MFC forum. I've seen people asking questions about rendering graphics there before with good results.
--
Larva-Tested, Pupa-Approved
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So, I've been studying Bresenhams algorithm for drawing lines. I understand how it works, mainly because I've executed the algorithm on paper. The algorithm is quite beautiful.
However, I fail to understand why it works. Well, I kind of sort of understand, but it's more of a gut feeling than anything else. I have a book titled "Computer Graphics: Principles and Practice, Second Edition in C". It states that a line can be desribed as
1) F(x, y) = a*x + b*y + c = 0 It also says
2) dy = y1 - y0
dx = x1 - x1 and goes on to state that the slope intercept form can be written as:
3) y = dy/dx * x + B It then concludes that
4) F(x, y) = dy * x - dx * y + B * dx = 0
I understand how 1), 2), 3) and 4) fit together. What I don't understand is where 1) comes from. I don't think I've ever seen an equation describing a line that way. I am unsure what it represents. I *think* it represents all values of x and y which are on the line. Is this the case? My gut feeling tells me that F(x, y) is a union of sorts of the functions f(y) and g(x), each describing the line from both axis. I would appreciate it if someone could help me understand this mystery of mine, or give me pointers to where I can find out.
--
LOADING...
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Hi,
ax+by+c=0 and y=dx+e are both formulas describing (all points belonging to) a straight line.
The former is fully symmetrical in x and y.
For both, you can introduce a new independent variable t, and then express both x and y as
a function of t, e.g.
x(t) = alpha * t + beta
y(t) = gamma * t + delta
this may make it easier to traverse the line: simply let t move from t0 to t1 (t0 and t1
corresponding to the known points (x0,y0) and (x1,y1).
Greetings,
Luc Pattyn
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Heh. if ax + by + c = 0, then y = (ax + c) / b, right? Hum.. could it be that easy? Talk about not seeing the forrest for all the trees. 
--
Not Y3K Compliant
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y = ax + b ⇒ y = dx + e (change of letters) ⇒ y - dx - e = 0 ⇒ ax + by + c = 0. The last is the definition of any function in n variable (F(a1, ..., an) = 0.
"I know which side I want to win regardless of how many wrongs they have to commit to achieve it." - Stan Shannon
Web - Blog - RSS - Math - LinkedIn - BM
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The equation for a line that you're probably familiar with is
5) y = mx + b where m is the slope and b is the Y-intercept. You can get from 1) to 5) with algebra:
ax + by + c = 0
ax/b + y + c/b = 0 [divide both sides by b]
y = -ax/b - c/b [subtract the same term from both sides]
y = Mx + B [substitute M = -a/b, B = -c/b] You can prove that B = -c/b is the Y-intercept by evaluating 1) for x=0.
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i want to see code for Nearest neighbour algorithm
-for example
if i have 3 classes each one have X1 .X2,X3
and i have afile contain 100 pattren i choose 50 raqndomly to know in witch class
If I HaD OnE sInglE wIsh IwIll gO back for thE fIrst tIme i sEE yOu
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Could you please explain this a bit more ?
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i want an example of how this algorithm can be implement
in c#
If I HaD OnE sInglE wIsh IwIll gO back for thE fIrst tIme i sEE yOu
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can somebody give me the source code of this problem (TSP travelling salesman problem) in java ?? or somewhere similar ???
please ???
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I SHOULD NOT reply because I'm SO BAD at Math.. but I had to!
I found one Open Source program.. There are MANY out on the NET.
http://sourceforge.net/projects/jcconvenant
I only responded to this because this is the only Math subject I ever got a 'A' in.. I had the C# code I used for the grade but I cannot find it. (You would be more than welcome to it BUT.. I'm affraid it's lost) It has been been awhile since it was made. Sorry! As I remember it took me forever to get it right.
If it helps, I found a book at the time which 'at least made me understand the subject'
Algorithms In C, Third addition, Graphic algorithms, Part 5, by Robert Sedgewick, Addison-Wesley
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Just me at will_george...something wrote: Algorithms In C, Third addition, Graphic algorithms, Part 5, by Robert Sedgewick, Addison-Wesley
Excellent choice. There are C++ versions available as well, with parts 1-4 (in a single volume), and part 5.
Steve S
Developer for hire
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There are C++ versions available as well.. That is what I have! I really did not fing <<< (I thought I typed FIND) it hard to translate it to C# Well, the graphic part was a bit of a problem though. I only mentioned this book because I'm sort of stupid at math (but I love to try!) and this book at least made me think I knew what I was doing!
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Hi, iam the mathematics person.can anyone give me the problem so i can sure help on it.
please give me the problem then i will think on it.
mehata sheetal
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Hi, iam the mathematics person.can anyone give me the problem so i can sure help on it. please give me the problem then i will think on it......
Hi, I'm the mathematics person. Can anyone give me a problem? I'm sure I can help you with it.
I changed some of the English... LOL.. Not that I am a expert on it. I have been doing it for only 65+ years. I still get it all wrong!
Really! There is NO HATE HERE toward anybody.. I just thought it was funny from my point of view. I have a strange mind and had a good laugh. Good way to start a day. Thank You!
By the way, I know no other language except my Chicago style English. I'm in wonder of people that speak or write in other languages! Amazing! I have a 'TIN' ear and cannot get the 'words' spoken in my brain.
I'm about as poor at Math as my English!
Anyway... My question, which I'm sure is stupid. (I have no shame so I'll ask it anyway.)
I hope I can explain what I am thinking of....
Using Trig in a C# program or other (I mention C# because it is what I usually use now) I see strange results on what I try to do. (I would assume it is me) BUT I had this thought in my little old brain. The way I see it, Trig. is based on a true circle. However when I make a picturebox, panel or other it is always some sort of square or rectangle with my bitmap or Draw object within it. (Does Microsoft have a true circle Control?) If I want a theta, I 'think' it is sort of based on the mouse/joystick input from the picturebox/panel/whatever which is a square/rectangle..
What am I missing? I'm lost.
Bless YOU!
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 HI,
i m transportation engg. M.tech student. i want to learn matlab. how to start it from the begining????
i want to solve genetic algorithm for my project work. is matlab will be simple or c programme???????
REPLY ME
HAVE A NICE DAY
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leckey wrote: Nuff said.
Yeppers.
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