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  • base pointer to derived class

    - by Jay
    Suppose there are Base class and Derived class. Base *A = new Base; Here A is a pointer point to Base class, and new constructs one that A points to. I also saw Base *B = new Derived; How to explain this? B is a pointer to Base Class, and a Derived class constructed and pointed by B? If there is a function derived from Base class, say, Virtual void f(), and it's been overridden in Derived class, then B->f() will invoke which version of the function? version in Base class, or version that overridden in Derived Class. What if there is a new function void g()in Derived, is B->g() going to invoke this function properly? One more is, is int *a = new double; or int *a = new int; legal?

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  • MySQL query with JOINS and GROUP BY

    - by user1854049
    I'm building a MySQL query but I can't seem to get it right. I have four tables: - customers - orders - sales_rates - purchase_rates There is a 1:n relation 'customernr' between customers and orders. There is a 1:n relation 'ordernr' between orders and sales_rates. There is a 1:n relation 'ordernr' between orders and purchase_rates. What I would like to do is produce an output of all customers with their total purchase and sales amounts. So far I have the following query. SELECT c.customernr, c.customer_name, SUM(sr.sales_price) AS sales_price, SUM(pr.purchase_price) AS purchase_price FROM orders o, customers c, sales_rates sr, purchase_rates pr WHERE o.customernr = c.customernr AND o.ordernr = sr.ordernr AND o.ordernr = pr.ordernr GROUP BY k.bedrijfsnaam The result of the sales_price and purchase_price is far too high. I seem to be getting double counts. What am I doing wrong? Is it possible to perform this in a single query? Thank for your response!

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  • deleting dynamically allocated object that contains vector in C++ STL

    - by kobac
    I have a class class ChartLine{ protected: vector<Point> line; // points connecting the line CString name; //line name for legend CPen pen; //color, size and style properties of the line }; where Point is a structure struct Point{ CString x; double y; }; In main() I dynamically allocate objects of type ChartLine with new operator. If I use delete afterwards, will default destructor ~ChartLine() properly dealocate (or clear) member ChartLine::line(which is vector btw) or I would have to clear that vector in ~ChartLine() manually? Thanks in advance. Cheers.

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  • Fast ceiling of an integer division in C / C++

    - by andand
    Given integer values x and y, C and C++ returns as the quotient q = x/y the floor of the floating point valued equivalent. I'm interestd in a method of returning the ceiling instead? For example, ceil(10/5) = 2 and ceil(11/5) = 3. The obvious approach involves something like: q = x / y; if (q * y < x) ++q; This requires an extra comparison and multiplication; and other methods I've seen (used in fact) involve casting as a float or double. Is there a more direct method that avoids the additional multiplication (or a second division) and branch, and that also avoids casting as a floating point number?

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  • How to get the right row in a sorted DataView?

    - by ZeissS
    Hi, I have a DataGrid containing a small table. Until now, I had a double click handler on this grid which iterated over all rows to find the selected one: DataTable table = (DataTable)this.dataGrid.DataSource; int selectedRow = -1; for (int i=0; i<table.Rows.Count; i++) if (this.dataGrid.IsSelected(i)) selectedRow = i; break; } if ( selectedRow != -1 ) { DataRow row = table.Rows[selectedRow]; // More code ... } Problem: When the user clicks on a column header and sort the table, table.Rows does not return the right rows. It still contains the unsorted rows. How can I get the right column?

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  • Permissions for Large Variables to Be Sent Via Stored Procedures (SQL Server)

    - by Joe Majewski
    I can't figure out a way to allow more than 4000 bytes to be received at once via a call to a stored procedure. I am storing images in the table that are around 15 - 20 kilobytes each, but upon getting them and displaying them to the page, they are always exactly 3.91 KB in size (or 4000 bytes). Do stored procedures have a limit on how much data can be sent at once? I double-checked my data, and I am indeed only receiving the first 4000 characters from the varbinary(MAX) field. Is there a permission setting to allow more than 4k bytes at once?

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  • Property hiding and reflection (C#)

    - by tehMick
    Declaring a property in a derived class that matches the name of a property in the base class "hides" it (unless it overrides it with the override keyword). Both the base and derived class properties will be returned by Type.GetProperties() if their types don't match. However, if their types do match, shockingly only the derived class's property is returned. For instance: class A { protected double p; public int P { get { return (int)p; } set { p = value; } } } class B : A { public new int P { get { return (int)p; } set { p = value; } } } class C : B { public new float P { get { return (float)p; } set { p = value; } } } Calling typeof(C).GetProperties() will only return B.P and C.P. Is it possible to call GetProperties() in a way that returns all three? There is almost certainly a way to do it by traversing the inheritance hierarchy, but is there a cleaner solution?

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  • Change the image height and width based on the scale?

    - by user281947
    I want to resize the image height and width after setting its scale, below is what i am doing : <Image x:Name="img" Source="sii.PNG" > <Image.RenderTransform> <ScaleTransform x:Name="scale" /> </Image.RenderTransform> </Image> below is the cs code : void Slider_ValueChanged(object sender, RoutedPropertyChangedEventArgs<double> e) { scale.ScaleX = scale.ScaleY =e.NewValue; //here i have to change the height and width of an image }

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  • Image-free, custom-styled search bar

    - by Jon
    I'm working with the designer and he sent me the following design for the search bar on our webpage: I'm very much against using images in webpage design unless completely necessary, so I'm hoping that I can recreate the whole search bar widget in CSS. I know how to do border-radius, gradients, box-shadows, etc, so that's not a problem. Question: Assuming CSS3 browser compatibility, how can I go about recreating the actual search button (the magnifying glass portion) with the double curved edge, and the slight drop shadow on the bottom left? Thoughts: My initial feeling was that the search button would be circular and free-standing, then overlap the search input div with a negative left-margin, but then I was unsure how I would get that drop shadow. Edit: I'm not completely opposed to using an image for the magnifying glass, but I've seen a similar icon created in CSS before. Would an image vs. pure CSS end up loading at the same speed, or should I do all I can do in pure CSS?

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  • Upgrading IIS web sever framework 2.0 to 3.5 considerations

    - by Grant
    Hi, i will be responcible for upgrading an IIS web server from the Microsoft .NET framework v2.0 to v3.5. I am wondering if there is anything special i need to know or any caveats i should be aware of before proceding? The site gets a fair number of hits per day and I will be taking it down and performing the upgrade at an off-peak time. Aside from double clicking the installer is there anything i need to know? Will the server need to be rebooted afterwards, does the installer handle all of the configuration changes? etc.. Thanks.

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  • visual studio C++ toggle comment ? comment while not whole line is selected ?

    - by Mr_and_Mrs_D
    2 questions actually : 1) shortcut to toggle comment on selected lines ? Available on all iDEs I used starting with notepad++ 2)the ctrl-k, ctrl-c exhibits this behavior (quoted from someplace nicely worded): C#: Each line where some text is selected is commented at the line-start with double-slash. If nothing is selected, the line where the cursor is is commented. C++: If nothing is selected or complete lines are selected, it behaves as above. However, if parts of a line are selected, and no comment is selected as part of the selection (ex. select something in the middle of a code line), then the selection is surrounded by /* and */. since I code in C++ I find this behavior annoying - I want to be able to comment out lines partially selected - any workarounds ?

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  • When is (true == x) === !!x false?

    - by Paul S.
    JavaScript has different equality comparison operators Equal == Strict equal === It also has a logical NOT ! and I've tended to think of using a double logical NOT, !!x, as basically the same as true == x. However I know this is not always the case, e.g. x = [] because [] is truthy for ! but falsy for ==. So, for which xs would (true == x) === !!x give false? Alternatively, what is falsy by == but not !! (or vice versa)?

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  • log (1-var) operation in C

    - by heike
    I am trying to code this algorithm. I am stuck in the part of log((1.0-u)/u))/beta; As I understand, I can not get the result of this in C, as it will always return me with negative value log (returning imaginary value). Tried to print the result of log(1-5) for instance, it gives me with Nan. How can I get the result of double x = (alpha - log((1.0-u)/u))/beta then? Would appreciate for any pointers to solve this problem. Thank you

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  • problem with sql statement using vb.net

    - by newBie
    hi i got some problem i got this 3 line statement: Dim infoID As Integer = objCommand1.ExecuteScalar() Dim strSQL2 As String = "insert into feedBackHotel (infoID, feedBackView) values(" + infoID + ",'" + FeedBack + "')" Dim objCommand2 As New SqlCommand(strSQL2, conn) objCommand2.ExecuteNonQuery() the problem here is..the strSQL2 can capture the infoID from previous statement, but it didnt insert into the database. it will pop out this error "Conversion from string "insert into feedBackHotel (infoI" to type 'Double' is not valid." in both table related, use same data type (int) but for the feedBackHotel's infoID i allow it to be null..bcoz if i make it not null, it will show another error.. im using vb.net ..can anyone help?

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  • [C++] Why am I not getting the same values?

    - by xbonez
    I am using Bode's formuala to calculate distance of nth planet from sun dist = (4 + 3*(2^(n-2)))/10 If I calculate the distance this way, I get the right values: dist[2] = ((4 + 3*1)/10.0) ; dist[3] = ((4 + 3*2)/10.0) ; dist[4] = ((4 + 3*4)/10.0) ; But doing it this way, gives me incorrect values: vector double> dist(5); for (unsigned int i = 2; i < 5; i++) { dist[i] = ((4 + 3*(2^(3-2)))/10.0) ; } ` Why so?

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  • OnSize() Problem in VC++

    - by Anu
    Hi, In my VC++ MFC applcaiton,i have different views.And in each view,when i maximize it,i changed the size and position to new thing(Normally it fully get maximixed to screen size).But i dont want tht.So in OnSize() i coded like this. void CChildFrame::OnSize(UINT nType, int cx, int cy) { CMDIChildWnd::OnSize(nType, cx, cy); int XBorder = GetSystemMetrics(SM_CXMAXIMIZED); int YBorder = GetSystemMetrics(SM_CYMAXIMIZED); switch (nType) { case SIZE_MAXIMIZED: SetWindowPos(NULL,0,60,XBorder-45,YBorder-60,SWP_NOZORDER ); break; } } But what happened is?When i maximize the view,its get maximized to above mention size only.But in that blue bar,there si no minimize,maximize,close button. When i double click in the blue bar,its get to resumed to previous postion with all buttons. How can i get that?

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  • Why is this C or C++ macro not expanded by the preprocessor?

    - by Atul
    Can someone points me the problem in the code when compiled with gcc 4.1.0. #define X 10 int main() { double a = 1e-X; return 0; } I am getting error:Exponent has no digits. When i replace X with 10, it works fine. Also i checked with g++ -E command to see the file with preprocessors applied, it has not replaced X with 10. I was under the impression that preprocessor replaces every macro defined in the file with the replacement text with applying any intelligence. Am I wrong? I know this is a really silly question but I am confused and I would rather be silly than confused :). Any comments/suggestions.

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  • Multithreaded SDL error in C++

    - by wyatt
    I'm building a program in C++, using SDL, and am occasionally receiving this error: * glibc detected * ./assistant: double free or corruption (!prev) It's difficult to replicate, so I can't find exactly what's causing it, but I just added a second thread to the program, and neither thread run on its own seems to cause the error. The threads don't share any variables, though they both run the functions SDL_BlitSurface and SDL_Flip. Could running these concurrently throw up such an error, or am I barking up the wrong tree? If this is the cause, should I simply throw a mutex around all SDL calls? Thanks

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  • C++ stringstream reads all zero's

    - by user69514
    I have a file which contains three integers per line. When I read the line I use a stringstream to separate the values, but it only reads the first value as it is. The other two are read as zero's. ifstream inputstream(filename.c_str()); if( inputstream.is_open() ){ string line; stringstream ss; while( getline(inputstream, line) ){ //check line and extract elements int id; double income; int members; ss.clear(); ss.str(line); ss >> id >> income >> members; In the case above, id is extracted correctly, but income, and members get assigned zero instead of the actual value.

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  • RSpec "undefined local variable or method `user'"

    - by Justin
    I have the following test written in RSpec: describe '#create' do ... it 'redirects users to profile page' do response.should redirect_to user_path(user) end ... ... And the following in my UsersController: def create @user = User.new(params[:user]) if @user.save redirect_to user_path(@user) end end Does anyone know why this is returning the following error: NameError: undefined local variable or method 'user' I also tried changing this to be root_url in both cases instead of user_path(user) and it gave a different error saying: Expected response to be a <:redirect>, but was <200> Does anyone know what the issue might be? I have double-checked my code and have seen similar questions posted online, but haven't been able to find a solution. Thanks in advance for any help!

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  • Speedup C++ code

    - by Werner
    Hi, I am writing a C++ number crunching application, where the bottleneck is a function that has to calculate for double: template<class T> inline T sqr(const T& x){return x*x;} and another one that calculates Base dist2(const Point& p) const { return sqr(x-p.x) + sqr(y-p.y) + sqr(z-p.z); } These operations take 80% of the computation time. I wonder if you can suggest approaches to make it faster, even if there is some sort of accuracy loss Thanks

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  • Robust Way of Selecting All Text in Textbox

    - by Emil
    I'm trying to have the content of the an HTML textbox be selected fully onFocus. I know the simple solution of putting a onfocus="this.select()" on the component but this is not a good solution because if a user double clicks into the area the selection is lost and in browsers like chrome it is rarely working like it should and just reverts into input form. I have searched on Google for a little while and can't find a good solution, most suggestions are of this simple solution. What I would like it is that the selection inside the textbox not change once selected and if possible the user should not be able to edit the content of the textbox, for example if you have used AdSense when you grab code from AdSense the selection never changes and your unable to alter the code in the textbox. Any solutions would be appreciated.

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  • TPageControl tab area OnMouseEnter OnMouseLeave events

    - by daemon_x
    Hello, I need to catch the "OnMouseEnter" and "0nMouseLeave" for a certain area of the TPageControl component. With that specific area I mean the whole "tab header" rectangle. The problem is, that the page control doesn't catch the messages (I'm catching internal control messages CM_MOUSEENTER and CM_MOUSELEAVE) in the "empty" space. The aim for me is to draw a small arrow in the right empty side when user hovers in the red framed area (and drawing is just piece of cake) and erase it when leaves this area. And I'm don't care about the overflow of the tabs (which causes to draw scrolling double button) - that will never happen.

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  • C++ vector reference parameter

    - by Archanimus
    Hello folks, let's say we have a class class MyClass { vector<vector<int > > myMatrice; public : MyClass(vector<vector<int > > &); } MyClass::MyClass(vector<vector<int > > & m) { myMatrice = m; } During the instanciation of MyClass, I pass a big vector < vector < int and I find that the object is actually copied and not only the reference, so it takes the double of the memory ... Please, can anyone help me out with this problem, I'm stuck since too many time ... And thanks a lot!

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  • Actionscript 2.0 element.text always outputs "00"

    - by Mbarry
    Hi everybody, I'm fighting against a strange behaviour with my actionscript! After setting the four integer variables from the MovieTimer sprite (hour, minute, second, mili-sec) and concate them i got always double zero: 00 stop (); delete this.onEnterFrame; var str1; var str2; var mili; var second; var minute; var hour; var timer; mili = _root.MovieTimer.txt_mili.text; second = _root.MovieTimer.txt_sec.text; minute = _root.MovieTimer.txt_min.text; hour = _root.MovieTimer.txt_heures.text; timer = hour+' : '+minute+' : '+second+' : '+mili; _root.MovieSpellFinish.TextTime.text = timer; _root.MovieSpellFinish.TextTime.text outputs: 00 is there any solutions for this??

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