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  • Best intro to C++ static metaprogramming?

    - by jwfearn
    Static metaprogramming (aka "template metaprogramming") is a great C++ technique that allows the execution of programs at compile-time. A light bulb went off in my head as soon as I read this canonical metaprogramming example: #include <iostream> using namespace std; template< int n > struct factorial { enum { ret = factorial< n - 1 >::ret * n }; }; template<> struct factorial< 0 > { enum { ret = 1 }; }; int main() { cout << "7! = " << factorial< 7 >::ret << endl; // 5040 return 0; } If one wants to learn more about C++ static metaprogramming, what are the best sources (books, websites, on-line courseware, whatever)?

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  • How do I properly display all content in a JTabbedPane?

    - by maleki
    I am nesting a JPanel inside a JTabbedPane. I am having trouble displaying all the content inside of the JTabbedPane. The outside borders of the internal content get chopped off. I am currently not using a Layout Manager for my JTabbedPane or dummy Panel because it stretches my content automatically. How do I add a JPanel inside the JTabbedPane so that I can have an even border around all the content.My attempts to create a dummy panel and setting a border for the inner panel using BorderFactory haven't worked. Is there a convention that I need to know to do this correctly? JTabbedPane tabPane = new JTabbedPane(); GridPane tab1 = new GridPane(); GridPane tab2 = new GridPane(); tabPane.add("My Pieces",tab1); tabPane.add("Opponent Pieces",tab2); public class GridPane extends JPanel { public GridPane() { this.setPreferredSize(new Dimension(400,160)); this.setLayout(new GridLayout(4,10)); this.setComponentOrientation(ComponentOrientation.LEFT_TO_RIGHT); for (int i = 0; i < 4; i++) { for (int j = 0; j < 10; j++) { boardSquares[i][j] = new JPanel(); boardSquaresArr.add(boardSquares[i][j]); this.add(boardSquares[i][j]); } } } }

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  • How to TDD Asynchronous Events?

    - by Padu Merloti
    The fundamental question is how do I create a unit test that needs to call a method, wait for an event to happen on the tested class and then call another method (the one that we actually want to test)? Here's the scenario if you have time to read further: I'm developing an application that has to control a piece of hardware. In order to avoid dependency from hardware availability, when I create my object I specify that we are running in test mode. When that happens, the class that is being tested creates the appropriate driver hierarchy (in this case a thin mock layer of hardware drivers). Imagine that the class in question is an Elevator and I want to test the method that gives me the floor number that the elevator is. Here is how my fictitious test looks like right now: [TestMethod] public void TestGetCurrentFloor() { var elevator = new Elevator(Elevator.Environment.Offline); elevator.ElevatorArrivedOnFloor += TestElevatorArrived; elevator.GoToFloor(5); //Here's where I'm getting lost... I could block //until TestElevatorArrived gives me a signal, but //I'm not sure it's the best way int floor = elevator.GetCurrentFloor(); Assert.AreEqual(floor, 5); } Edit: Thanks for all the answers. This is how I ended up implementing it: [TestMethod] public void TestGetCurrentFloor() { var elevator = new Elevator(Elevator.Environment.Offline); elevator.ElevatorArrivedOnFloor += (s, e) => { Monitor.Pulse(this); }; lock (this) { elevator.GoToFloor(5); if (!Monitor.Wait(this, Timeout)) Assert.Fail("Elevator did not reach destination in time"); int floor = elevator.GetCurrentFloor(); Assert.AreEqual(floor, 5); } }

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  • Trouble with __VA_ARGS__

    - by Noah Roberts
    C++ preprocessor __VA_ARGS__ number of arguments The accepted answer there doesn't work for me. I've tried with MSVC++ 10 and g++ 3.4.5. I also crunched the example down into something smaller and started trying to get some information printed out to me in the error: template < typename T > struct print; #include <boost/mpl/vector_c.hpp> #define RSEQ_N 10,9,8,7,6,5,4,3,2,1,0 #define ARG_N(_1,_2,_3,_4,_5,_6,_7,_8,_9,_10,N,...) N #define ARG_N_(...) ARG_N(__VA_ARGS__) #define XXX 5,RSEQ_N #include <iostream> int main() { print< boost::mpl::vector_c<int, ARG_N_( XXX ) > > g; // ARG_N doesn't work either. } It appears to me that the argument for ARG_N ends up being 'XXX' instead of 5,RSEQ_N and much less 5,10,...,0. The error output of g++ more specifically says that only one argument is supplied. Having trouble believing that the answer would be proposed and then accepted when it totally fails to work, so what am I doing wrong? Why is XXX being interpreted as the argument and not being expanded? In my own messing around everything works fine until I try to pass off VA_ARGS to a macro containing some names followed by ... like so: #define WTF(X,Y,...) X , Y , __VA_ARGS__ #define WOT(...) WTF(__VA_ARGS__) WOT(52,2,5,2,2) I've tried both with and without () in the various macros that take no input.

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  • Trying to Create a ToolBar with an ImageList, not working.

    - by blaquee
    Im trying to get my toolbar to work, with an imagelist. The images are png's and are individual So i was adding them in the ImageList in succession. But it wasnt working, Here is the code to add the Image to the ImageList HIMAGELIST CreateToolBarImages( HINSTANCE hInst) { HIMAGELIST v_ImageList = NULL; //IMAGE_LIST v_Img; HICON hIcon; HBITMAP hBit; COLORMAP cMap; COLORREF fromColor = RGB( 0,0,0 ); InitCommonControls(); v_ImageList = ImageList_Create( 32,32, ILC_MASK, 1,1 ); cMap.from = fromColor; cMap.to = ::GetSysColor ( COLOR_BTNFACE ); hBit = CreateMappedBitmap( hInst, IDB_CONSOLE, 0, &cMap, 1 ); //hBit = LoadBitmap( hInst, MAKEINTRESOURCE(IDB_CONSOLE) ); consoleImg = ImageList_Add( v_ImageList, hBit, 0 ); if( consoleImg == -1 ) return NULL; DeleteObject( hBit ); Then i create The ToolBar, but it fails at the Image function. HWND CreateToolBarButton( HWND hWndParent ) { const int ImageID = 0; const int numB = 1; COLORREF iColor; HWND hToolBar = CreateWindowEx( 0, TOOLBARCLASSNAME, NULL, WS_CHILD |TBSTYLE_LIST |TBSTYLE_FLAT | WS_VISIBLE, 0,0,0,0, hWndParent, NULL, g_hInst, NULL ); if( hToolBar == NULL ) return NULL; HIMAGELIST ImgList = CreateToolBarImages ( g_hInst); if( ImgList == NULL ) MessageBox( hWndParent, L"No Tool Images", L"BOB", MB_OK ); return NULL; Is there something im missing? or not doing?

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  • How can I work around SQL Server - Inline Table Value Function execution plan variation based on par

    - by Ovidiu Pacurar
    Here is the situation: I have a table value function with a datetime parameter ,lest's say tdf(p_date) , that filters about two million rows selecting those with column date smaller than p_date and computes some aggregate values on other columns. It works great but if p_date is a custom scalar value function (returning the end of day in my case) the execution plan is altered an the query goes from 1 sec to 1 minute execution time. A proof of concept table - 1K products, 2M rows: CREATE TABLE [dbo].[POC]( [Date] [datetime] NOT NULL, [idProduct] [int] NOT NULL, [Quantity] [int] NOT NULL ) ON [PRIMARY] The inline table value function: CREATE FUNCTION tdf (@p_date datetime) RETURNS TABLE AS RETURN ( SELECT idProduct, SUM(Quantity) AS TotalQuantity, max(Date) as LastDate FROM POC WHERE (Date < @p_date) GROUP BY idProduct ) The scalar value function: CREATE FUNCTION [dbo].[EndOfDay] (@date datetime) RETURNS datetime AS BEGIN DECLARE @res datetime SET @res=dateadd(second, -1, dateadd(day, 1, dateadd(ms, -datepart(ms, @date), dateadd(ss, -datepart(ss, @date), dateadd(mi,- datepart(mi,@date), dateadd(hh, -datepart(hh, @date), @date)))))) RETURN @res END Query 1 - Working great SELECT * FROM [dbo].[tdf] (getdate()) The end of execution plan: Stream Aggregate Cost 13% <--- Clustered Index Scan Cost 86% Query 2 - Not so great SELECT * FROM [dbo].[tdf] (dbo.EndOfDay(getdate())) The end of execution plan: Stream Aggregate Cost 4% <--- Filter Cost 12% <--- Clustered Index Scan Cost 86%

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  • How do I determine if a terminal is color-capable?

    - by asjo
    I would like to change a program to automatically detect whether a terminal is color-capable or not, so when I run said program from within a non-color capable terminal (say M-x shell in (X)Emacs), color is automatically turned off. I don't want to hardcode the program to detect TERM={emacs,dumb}. I am thinking that termcap/terminfo should be able to help with this, but so far I've only managed to cobble together this (n)curses-using snippet of code, which fails badly when it can't find the terminal: #include <stdlib.h> #include <curses.h> int main(void) { int colors=0; initscr(); start_color(); colors=has_colors() ? 1 : 0; endwin(); printf(colors ? "YES\n" : "NO\n"); exit(0); } I.e. I get this: $ gcc -Wall -lncurses -o hep hep.c $ echo $TERM xterm $ ./hep YES $ export TERM=dumb $ ./hep NO $ export TERM=emacs $ ./hep Error opening terminal: emacs. $ which is... suboptimal.

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  • Objective-C autorelease pool not releasing object

    - by Chris
    Hi I am very new to Objective-C and was reading through memory management. I was trying to play around a bit with the NSAutoreleasePool but somehow it wont release my object. I have a class with a setter and getter which basically sets a NSString *name. After releasing the pool I tried to NSLog the object and it still works but I guess it should not? @interface TestClass : NSObject { NSString *name; } - (void) setName: (NSString *) string; - (NSString *) name; @end @implementation TestClass - (void) setName: (NSString *) string { name = string; } - (NSString *) name { return name; } @end int main (int argc, const char * argv[]) { NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init]; TestClass *var = [[TestClass alloc] init]; [var setName:@"Chris"]; [var autorelease]; [pool release]; // This should not be possible? NSLog(@"%@",[var name]); return 0; }

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  • boost::lambda bind expressions can't get bind to string's empty() to work

    - by navigator
    Hi, I am trying to get the below code snippet to compile. But it fails with: error C2665: 'boost::lambda::function_adaptor::apply' : none of the 8 overloads could convert all the argument types. Sepcifying the return type when calling bind does not help. Any idea what I am doing wrong? Thanks. #include <boost/lambda/lambda.hpp> #include <boost/lambda/bind.hpp> #include <string> #include <map> int main() { namespace bl = boost::lambda; typedef std::map<int, std::string> types; types keys_and_values; keys_and_values[ 0 ] = "zero"; keys_and_values[ 1 ] = "one"; keys_and_values[ 2 ] = "Two"; std::for_each( keys_and_values.begin(), keys_and_values.end(), std::cout << bl::constant("Value empty?: ") << std::boolalpha << bl::bind(&std::string::empty, bl::bind(&types::value_type::second, _1)) << "\n"); return 0; }

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  • Objective-C basics: subclassing and member variable accessability

    - by Krumelur
    Hi, Code below is pseudo code. Imagine a class "Fruit" which has a factory method to create a fruit. interface Fruit { } +(Fruit*) createFruit: { return [[Fruit alloc] init autorelease]; } Now I want to subclass the Fruit to get an Apple: interface Apple : Fruit { int iSeeds; } +(Apple*) createAppleWithColor: (int) iSeeds { Apple* oApple = [Apple createFruit:]; oApple.iSeeds = iSeeds; return oApple; } Questions: How can I make "iSeeds" private so it cannot be changed from outside? If I add a "private" keyword it does not build anymore. Still I want to set iSeeds from inside my Apple's factory method. I want users allow to READ the content of iSeeds. So I suppose I should have a getter but I can't get it to work. I always get some error about "LValue assignment". The Fruit's createFruit is making use of autorelease. Does the Apple have to reatin/release anything? René

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  • DataTable won't DataBind with a DataTable.NewRow()

    - by David
    Is DataRow.NewRow() insufficient as the only row in a DataTable? I would expect this to work, but it doesn't. It's near the end of my Page_Load inside my If(!Postback) block. gridCPCP is GridView DataTable dt = new DataTable(); dt.Columns.Add("ID", int.MinValue.GetType()); dt.Columns.Add("Code", string.Empty.GetType()); dt.Columns.Add("Date", DateTime.MinValue.GetType()); dt.Columns.Add("Date2", DateTime.MinValue.GetType()); dt.Columns.Add("Filename", string.Empty.GetType()); //code to add rows if (dt.Rows.Count > 0) { gridCPCP.DataSource = dt; gridCPCP.DataBind(); } else { dt.Rows.Add(dt.NewRow()); gridCPCP.DataSource = dt; gridCPCP.DataBind(); //EXCEPTION int TotalColumns = gridCPCP.Rows[0].Cells.Count; gridCPCP.Rows[0].Cells.Clear(); gridCPCP.Rows[0].Cells.Add(new TableCell()); gridCPCP.Rows[0].Cells[0].ColumnSpan = TotalColumns; gridCPCP.Rows[0].Cells[0].Text = "No Record Found"; } The exception throws on gridCPCP.DataBind() and only when execution reaches the else block. If there were rows added above via dt.Rows.Add(new object[] { ... } binding works. System.ArgumentOutOfRangeException: Length cannot be less than zero. Parameter name: length

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  • Inverted colours in tiff to PDF conversion

    - by spiderdijon
    I'm sure I'm making some kind of silly mistake here, but when converting a tiff file to PDF, the colours become reversed. I can't figure out why. Here's my code: PdfWriter writer = PdfWriter.GetInstance(document, new FileStream("Image.pdf", FileMode.Create)); System.Drawing.Bitmap bm = new System.Drawing.Bitmap(@"C:\Temp\338814-00.tif"); int total = bm.GetFrameCount(FrameDimension.Page); document.Open(); PdfContentByte cb = writer.DirectContent; for (int k = 0; k < total; ++k) { bm.SelectActiveFrame(FrameDimension.Page, k); MemoryStream ms = new MemoryStream(); bm.Save(ms, ImageFormat.Tiff); Image img = Image.GetInstance(ms.ToArray()); img.ScalePercent(72f / (float)img.DpiX * 100); img.SetAbsolutePosition(0, 0); cb.AddImage(img); document.NewPage(); } document.Close(); Thanks.

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  • Advantages/Disadvantages of different implementations for Comparing Objects using .NET

    - by Kevin Crowell
    This questions involves 2 different implementations of essentially the same code. First, using delegate to create a Comparison method that can be used as a parameter when sorting a collection of objects: class Foo { public static Comparison<Foo> BarComparison = delegate(Foo foo1, Foo foo2) { return foo1.Bar.CompareTo(foo2.Bar); }; } I use the above when I want to have a way of sorting a collection of Foo objects in a different way than my CompareTo function offers. For example: List<Foo> fooList = new List<Foo>(); fooList.Sort(BarComparison); Second, using IComparer: public class BarComparer : IComparer<Foo> { public int Compare(Foo foo1, Foo foo2) { return foo1.Bar.CompareTo(foo2.Bar); } } I use the above when I want to do a binary search for a Foo object in a collection of Foo objects. For example: BarComparer comparer = new BarComparer(); List<Foo> fooList = new List<Foo>(); Foo foo = new Foo(); int index = fooList.BinarySearch(foo, comparer); My questions are: What are the advantages and disadvantages of each of these implementations? What are some more ways to take advantage of each of these implementations? Is there a way to combine these implementations in such a way that I do not need to duplicate the code? Can I achieve both a binary search and an alternative collection sort using only 1 of these implementations?

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  • Recommendations, Asp.Net ObjectDataSource bind result of webservice call

    - by DerDres
    I need recommendations on how to solve / structure a solution to the following problem. In an asp.net web application i'll have to visualise results returned from a web service call. Im planning to use a repeater server control and bind this with an objectdatasource. The service returns a result of the form: public class SearchResult : IExtensibleDataObject { [DataMember] public Guid SearchId { get; set; } [DataMember] public DateTime Timestamp { get; set; } [DataMember] public int Offset { get; set; } [DataMember] public int TotalResults { get; set; } [DataMember] public IList<ResultDocumentData> Documents { get; set; } It is the collection of Documents that I need to visualise with a repeater which will be associated with an ObjectDataSource. The datasource should work on the type ResultDocumentData; the collection property in the class SearchResult. I think I need to wrap the call to the webservice in a dataaccess layer class, that will have a getDocuments method returning an IList, that the ObjectDataSource can use as its SelectMethod. I think I could make this work, but I would like to know how to do it in an elegant way. Can you give me general recommendations and/or recommendations for the following: WebProject Folderstructure + naming Naming conventions for the name of the service wrapper class Creating the service reference

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  • I need to implement C# deep copy constructors with inheritance. What patterns are there to choose fr

    - by Tony Lambert
    I wish to implement a deepcopy of my classes hierarchy in C# public Class ParentObj : ICloneable { protected int myA; public virtual Object Clone () { ParentObj newObj = new ParentObj(); newObj.myA = theObj.MyA; return newObj; } } public Class ChildObj : ParentObj { protected int myB; public override Object Clone ( ) { Parent newObj = this.base.Clone(); newObj.myB = theObj.MyB; return newObj; } } This will not work as when Cloning the Child only a parent is new-ed. In my code some classes have large hierarchies. What is the recommended way of doing this? Cloning everything at each level without calling the base class seems wrong? There must be some neat solutions to this problem, what are they? Can I thank everyone for their answers. It was really interesting to see some of the approaches. I think it would be good if someone gave an example of a reflection answer for completeness. +1 awaiting!

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  • Ambiguous access to base class template member function

    - by Johann Gerell
    In Visual Studio 2008, the compiler cannot resolve the call to SetCustomer in _tmain below and make it unambiguous: template <typename TConsumer> struct Producer { void SetConsumer(TConsumer* consumer) { consumer_ = consumer; } TConsumer* consumer_; }; struct AppleConsumer { }; struct MeatConsumer { }; struct ShillyShallyProducer : public Producer<AppleConsumer>, public Producer<MeatConsumer> { }; int _tmain(int argc, _TCHAR* argv[]) { ShillyShallyProducer producer; AppleConsumer consumer; producer.SetConsumer(&consumer); // <--- Ambiguous call!! return 0; } This is the compilation error: // error C2385: ambiguous access of 'SetConsumer' // could be the 'SetConsumer' in base 'Producer<AppleConsumer>' // or could be the 'SetConsumer' in base 'Producer<MeatConsumer>' I thought the template argument lookup mechanism would be smart enough to deduce the correct base Producer. Why isn't it? I could get around this by changing Producer to template <typename TConsumer> struct Producer { template <typename TConsumer2> void SetConsumer(TConsumer2* consumer) { consumer_ = consumer; } TConsumer* consumer_; }; and call SetConsumer as producer.SetConsumer<AppleConsumer>(&consumer); // Unambiguous call!! but it would be nicer if I didn't have to...

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  • Does this mimic perfectly a function template specialization?

    - by zeroes00
    Since the function template in the following code is a member of a class template, it can't be specialized without specializing the enclosing class. But if the compiler's full optimizations are on (assume Visual Studio 2010), will the if-else-statement in the following code get optimized out? And if it does, wouldn't it mean that for all practical purposes this IS a function template specialization without any performance cost? template<typename T> struct Holder { T data; template<int Number> void saveReciprocalOf(); }; template<typename T> template<int Number> void Holder<T>::saveReciprocalOf() { //Will this if-else-statement get completely optimized out if(Number == 0) data = (T)0; else data = (T)1 / Number; } //----------------------------------- void main() { Holder<float> holder; holder.saveReciprocalOf<2>(); cout << holder.data << endl; }

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  • How to make Jtable column contain checkboxes?

    - by theraven
    Preface: I am horrible with java, and worse with java ui components. I have found several different tutorials on how to add buttons to tables, however I am struggling with adding checkboxes. I need to have a column that draws a text box ticked on default (cell renderer i think handles that), then on click of tickbox, unticks the box, redraws said box, and fires off an event somewhere I can track. currently I have a custom cellrenderer: public class GraphButtonCellRenderer extends JCheckBox implements TableCellRenderer { public GraphButtonCellRenderer() { } public Component getTableCellRendererComponent(JTable table, Object value, boolean isSelected, boolean hasFocus, int row, int column) { if(isSelected) setSelected(true); else setSelected(false); setMargin(new Insets(0, 16, 0, 0)); setIconTextGap(0); setBackground(new Color(255,255,255,0)); return this; }} Which currently handles drawing the tick box, but only ticks and unticks the box if that row is selected. But I don't know how to handle the events. Really what I am asking is possibly a link to a good tutorial on how to add checkboxes cleanly to a JTable. Any assist is greatly appreciated :)

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  • iPhone Core Data problem

    - by Junior B.
    This is my first project with Core Data, I followed the Event tutorial provided by Apple that helped me to understand the basic of core data in iPhone. But now, working over my project, I've a problem adding data into my database. When i create an object and set the data, if I try to get it back, the system returns me a strange sequence of characters. This is what i see in log if I try to log it: 2010-05-11 00:16:43.523 FG[2665:207] Package: ‡}00å 2010-05-11 00:16:43.525 FG[2665:207] Package: ‡}00å 2010-05-11 00:16:43.526 FG[2665:207] Package: ‡}00å 2010-05-11 00:16:43.527 FG[2665:207] Package: ‡}00å 2010-05-11 00:16:43.527 FG[2665:207] Package: ‡}00å 2010-05-11 00:16:43.527 FG[2665:207] Items: 5 What kind of problem could be this? Edit: This is the part of the code that generate the error: package = (Package *)[NSEntityDescription insertNewObjectForEntityForName:@"Package" inManagedObjectContext:moc]; theNodes = [doc nodesForXPath:@"//pack" error:&error]; for (CXMLElement *theElement in theNodes) { // Create a counter variable as type "int" int counter; // Loop through the children of the current node for(counter = 0; counter < [theElement childCount]; counter++) { if([[[theElement childAtIndex:counter] name] isEqualToString: @"id"]) [package setIdPackage:[[theElement childAtIndex:counter] stringValue]]; if([[[theElement childAtIndex:counter] name] isEqualToString: @"title"]) [package setPackageTitle:[[theElement childAtIndex:counter] stringValue]]; if([[[theElement childAtIndex:counter] name] isEqualToString: @"category"]) [package setCategory:[[theElement childAtIndex:counter] stringValue]]; if([[[theElement childAtIndex:counter] name] isEqualToString: @"lang"]) [package setLang:[[theElement childAtIndex:counter] stringValue]]; if([[[theElement childAtIndex:counter] name] isEqualToString: @"number"]) { NSNumberFormatter * f = [[NSNumberFormatter alloc] init]; [f setNumberStyle:NSNumberFormatterDecimalStyle]; NSNumber * myNumber = [f numberFromString:[[theElement childAtIndex:counter] stringValue]]; [f release]; [package setNumber:myNumber]; } } } NSLog([NSString stringWithFormat:@"=== %s ===\nID: %s\nCategory: %s\nLanguage: %s",[package packageTitle], [package idPackage] ,[package category],[package lang]]);

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  • Intel Assembly Programming

    - by Kay
    class MyString{ char buf[100]; int len; boolean append(MyString str){ int k; if(this.len + str.len>100){ for(k=0; k<str.len; k++){ this.buf[this.len] = str.buf[k]; this.len ++; } return false; } return true; } } Does the above translate to: start: push ebp ; save calling ebp mov ebp, esp ; setup new ebp push esi ; push ebx ; mov esi, [ebp + 8] ; esi = 'this' mov ebx, [ebp + 14] ; ebx = str mov ecx, 0 ; k=0 mov edx, [esi + 200] ; edx = this.len append: cmp edx + [ebx + 200], 100 jle ret_true ; if (this.len + str.len)<= 100 then ret_true cmp ecx, edx jge ret_false ; if k >= str.len then ret_false mov [esi + edx], [ebx + 2*ecx] ; this.buf[this.len] = str.buf[k] inc edx ; this.len++ aux: inc ecx ; k++ jmp append ret_true: pop ebx ; restore ebx pop esi ; restore esi pop ebp ; restore ebp ret true ret_false: pop ebx ; restore ebx pop esi ; restore esi pop ebp ; restore ebp ret false My greatest difficulty here is figuring out what to push onto the stack and the math for pointers. NOTE: I'm not allowed to use global variables and i must assume 32-bit ints, 16-bit chars and 8-bit booleans.

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  • concatenate string and running index into string within a loop

    - by user331706
    To use a given graphic package I need to define, book and fill histogram. How can I get the name of the histogram which is a string to concatenate with 2 integer as a string ( hts_i_j ) in 3 for loop instead. That has to be done in c++ See the exemple below to define TH1F* hts_5_53; TH1F* hts_5_54; …… TH1F* hts_5_69; to book hts_5_53= HDir.make("hts_5_53")," Title", 100,0.,100.); hts_5_54-HDir.make("hts_5_54")," Title", 100,0.,100.); …… hts_16_69-HDir.make("hts_16_69")," Title", 100,0.,100.); to fill hts_5_53-Fill(f) hts_5_54-Fill(f) …… hts_16_69-Fill(f) Instead I would like to define, book and fill in 3 for loops. e.g . for(int i=5, i<17, ++i){ for(int j=53, j<70, ++j){ hts_i_j } } how can I get the string hts to concatenate with the indices ( i,j) in a simple short way while defining, booking and filling in 3 for loop instead

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  • OpenGL particle system

    - by allan
    I'm really new with OpenGL, so bear with me. I'm trying to simulate a particle system using OpenGl but I can't get it to work, this is what I have so far: #include <GL/glut.h> int main (int argc, char **argv){ // data allocation, various non opengl stuff ............ glutInit(&argc, argv); glutInitDisplayMode(GLUT_RGB | GLUT_DOUBLE ); glutInitWindowPosition(100,100); glutInitWindowSize(size, size); glPointSize (4); glutCreateWindow("test gl"); ............ // initial state, not opengl ............ glViewport(0,0,size,size); glutDisplayFunc(display); glutIdleFunc(compute); glutMainLoop(); } void compute (void) { // change state not opengl glutPostRedisplay(); } void display (void) { glClear(GL_COLOR_BUFFER_BIT); glBegin(GL_POINTS); for(i = 0; i<nparticles; i++) { // two types of particles if (TYPE(particle[i]) == 1) glColor3f(1,0,0); else glColor3f(0,0,1); glVertex2f(X(particle[i]),Y(particle[i])); } glEnd(); glFlush(); glutSwapBuffers(); } I get a black window after a couple of seconds (the window has just the title bar before that). Where do I go wrong? Any help would be very much appreciated. Thanks. LE: the x and y coordinates of each particle are within the interval (0,size)

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  • Confused about definition of a 'median' when constructing a kd-Tree

    - by user352636
    Hi there. Im trying to build a kd-tree for searching through a set of points, but am getting confused about the use of 'median' in the wikipedia article. For ease of use, the wikipedia article states the pseudo-code of kd-tree construction as: function kdtree (list of points pointList, int depth) { if pointList is empty return nil; else { // Select axis based on depth so that axis cycles through all valid values var int axis := depth mod k; // Sort point list and choose median as pivot element select median by axis from pointList; // Create node and construct subtrees var tree_node node; node.location := median; node.leftChild := kdtree(points in pointList before median, depth+1); node.rightChild := kdtree(points in pointList after median, depth+1); return node; } } I'm getting confused about the "select median..." line, simply because I'm not quite sure what is the 'right' way to apply a median here. As far as I know, the median of an odd-sized (sorted) list of numbers is the middle element (aka, for a list of 5 things, element number 3, or index 2 in a standard zero-based array), and the median of an even-sized array is the sum of the two 'middle' elements divided by two (aka, for a list of 6 things, the median is the sum of elements 3 and 4 - or 2 and 3, if zero-indexed - divided by 2.). However, surely that definition does not work here as we are working with a distinct set of points? How then does one choose the correct median for an even-sized list of numbers, especially for a length 2 list? I appreciate any and all help, thanks! -Stephen

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  • slot function not getting called

    - by chappar
    I am learning QT and trying out some examples. I am trying to make a dialog that disappears a label when a button is pressed and makes it appear when the same button is pressed again. Below is the code. #include <QApplication> #include <QPushButton> #include <QLabel> #include <QDialog> #include <QObject> #include <QHBoxLayout> int main(int argc, char ** argv) { QApplication app(argc, argv); QDialog *dialog = new QDialog; QPushButton *testButton = new QPushButton(QObject::tr("test")); QLabel * testLabel = new QLabel (QObject::tr("test")); QHBoxLayout * layout = new QHBoxLayout; layout->addWidget(testButton); layout->addWidget(testLabel); QObject::connect(testButton, SIGNAL(toggled(bool)), testLabel, SLOT(setVisible(bool))); dialog->setLayout(layout); dialog->show(); return app.exec(); } It is not working. Whenever i press the test button nothing happens. But if i change the signal slot connections as QObject::connect(testButton, SIGNAL(clicked(bool)), testLabel, SLOT(setVisible(bool))); it makes the label disappear. So, why it is not working with signal "toggled". What i am guessing is, it is not able to find that signal. Can you guys throw some light?

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  • Proper Usage of SqlConnection in .NET

    - by Jojo
    Hi guys, I just want an opinion on the proper usage or a proper design with regards to using SqlConnection object. Which of the 2 below is the best use: A data provider class whose methods (each of them) contain SqlConnection object (and disposed when done). Like: IList<Employee> GetAllEmployees() { using (SqlConnection connection = new SqlConnection(this.connectionString)) { // Code goes here... } } Employee GetEmployee(int id) { using (SqlConnection connection = new SqlConnection(this.connectionString)) { // Code goes here... } } or SqlConnection connection; // initialized in constructor IList<Employee> GetAllEmployees() { this.TryOpenConnection(); // tries to open member SqlConnection instance // Code goes here... this.CloseConnection(); // return } Employee GetEmployee(int id) { this.TryOpenConnection(); // tries to open member SqlConnection instance // Code goes here... this.CloseConnection(); // return } Or is there a better approach than this? I have a focused web crawler type of application and this application will crawl 50 or more websites simultaneously (multithreaded) with each website contained in a crawler object and each crawler object has an instance of a data provider class (above). Please advise. Thanks.

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