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• Why are (almost) all the on-line games written in ActionScript (Flash) not Java?

  - by MasterPeter

  I absolutely love good defender games (e.g. Gemcraft, Protector: reclaiming the throne) as they can be intellectually quite challenging; it's like playing chess but a little less thinking a bit more action. Sadly, there are not that many good ones out there and I thought I would create one myself and share it with the rest of the world by making it available on-line. I have never worked with ActionScript but when it comes to on-line games, this is the main choice. I have tried to find a decent 2D game in the form of a Java applet but to no avail. Why is this so? I could write the game, most comfortably, in Delphi for Win32 but then people would need to download the executable, which could deter some form downloading it, and also it would only work on Windows. I am also familiar with Java, having worked with Java for the last four years or so. Although I don't have much experience with games programming. Should I note be deterred by the fact that all online games are written for in Flash and create my defender game as a Java applet, or should I consider learning ActionScript and games development for the ActionScript Virtual Machine (AS3 looks very much like Java... but still, it's an entirely new technology to me and I might never use it professionally.) Could you, please, just answer the the question in the title? Why Flash, not Java applets? Is it only 'politics'?

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• Why do I get errors when using unsigned integers in an expression with C++?

  - by neuviemeporte

  Given the following piece of (pseudo-C++) code: float x=100, a=0.1; unsigned int height = 63, width = 63; unsigned int hw=31; for (int row=0; row < height; ++row) { for (int col=0; col < width; ++col) { float foo = x + col - hw + a * (col - hw); cout << foo << " "; } cout << endl; } The values of foo are screwed up for half of the array, in places where (col - hw) is negative. I figured because col is int and comes first, that this part of the expression is converted to int and becomes negative. Unfortunately, apparently it doesn't, I get an overflow of an unsigned value and I've no idea why. How should I resolve this problem? Use casts for the whole or part of the expression? What type of casts (C-style or static_cast<...)? Is there any overhead to using casts (I need this to work fast!)? EDIT: I changed all my unsigned ints to regular ones, but I'm still wondering why I got that overflow in this situation.

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• Why does this ActionFilterAttribute not import data to the ViewModel?

  - by Tomas Lycken

  I have the following attribute public class ImportStatusAttribute : ActionFilterAttribute { public override void OnActionExecuted(ActionExecutedContext filterContext) { var model = (IHasStatus)filterContext.Controller.ViewData.Model; model.Status = (StatusMessageViewModel)filterContext.Controller.TempData["status"]; filterContext.Controller.ViewData.Model = model; } } which I test with the following test method (the first of several I'll write when this one passes...) [TestMethod] public void OnActionExecuted_ImportsStatusFromTempDataToModel() { // Arrange Expect(new { Status = new StatusMessageViewModel() { Subject = "The test", Predicate = "has been tested" }, Key = "status" }); var filterContext = new Mock<ActionExecutedContext>(); var model = new Mock<IHasStatus>(); var tempData = new TempDataDictionary(); var viewData = new ViewDataDictionary(model.Object); var controller = new FakeController() { ViewData = viewData, TempData = tempData }; tempData.Add(expected.Key, expected.Status); filterContext.Setup(c => c.Controller).Returns(controller); var attribute = new ImportStatusAttribute(); // Act attribute.OnActionExecuted(filterContext.Object); // Assert Assert.IsNotNull(model.Object.Status, "The status was not exported"); Assert.AreEqual(model.Object.Status.ToString(), ((StatusMessageViewModel)expected.Status).ToString(), "The status was not the expected"); } (Expect() is a method that saves some expectations in the expected object...) When I run the test, it fails on the first assertion, and I can't get my head around why. Debugging, I can see that model is populated correctly, and that (StatusMessageViewModel)filterContext.Controller.TempData["status"] has the correct data. But after model.Status = (StatusMessageViewModel)filterContext.Controller.TempData["status"]; model.Status is still null in my watch window. Why can't I do this?

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• Why does Ruby have Rails while Python has no central framework?

  - by yar

  This is a(n) historical question, not a comparison-between-languages question: This article from 2005 talks about the lack of a single, central framework for Python. For Ruby, this framework is clearly Rails. Why, historically speaking, did this happen for Ruby but not for Python? (or did it happen, and that framework is Django?) Also, the hypothetical questions: would Python be more popular if it had one, good framework? Would Ruby be less popular if it had no central framework? [Please avoid discussions of whether Ruby or Python is better, which is just too open-ended to answer.] Edit: Though I thought this is obvious, I'm not saying that other frameworks do not exist for Ruby, but rather that the big one in terms of popularity is Rails. Also, I should mention that I'm not saying that frameworks for Python are not as good (or better than) Rails. Every framework has its pros and cons, but Rails seems to, as Ben Blank says in the one of the comments below, have surpassed Ruby in terms of popularity. There are no examples of that on the Python side. WHY? That's the question.

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• Why does an authorized OAuth request token need to be exchanged for an access token?

  - by Joe Shaw

  I'm wondering what the reasons are for OAuth to require a round-trip to the data provider to exchange an authorized request token for an access token. My understanding of the OAuth workflow is: Requesting site (consumer) gets a request token from the data provider site (service provider). Requesting site asks the data provider site to authenticate the user, passing in a callback. Once the user has been authenticated and authorized the requesting site, the user is directed back to the requesting site (consumer) via the callback provided which passes back the now-authorized request token and a verification code. The requesting site exchanges the request token for an access token. The requesting site uses the access token to get data from the data provider site. Assuming I got that right, why couldn't the callback simply provide the access token to the requesting site directly in step 3, eliminating step 4? Why is the request to exchange the request token for the access token necessary? Does it exist solely for consumers that require users to enter the verification code manually, with the thought that it would be shorter and simpler than the access token itself?

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• Why does Python sometimes upgrade a string to unicode and sometimes not?

  - by samtregar

  I'm confused. Consider this code working the way I expect: >>> foo = u'Émilie and Juañ are turncoats.' >>> bar = "foo is %s" % foo >>> bar u'foo is \xc3\x89milie and Jua\xc3\xb1 are turncoats.' And this code not at all working the way I expect: >>> try: ... raise Exception(foo) ... except Exception as e: ... foo2 = e ... >>> bar = "foo2 is %s" % foo2 ------------------------------------------------------------ Traceback (most recent call last): File "<ipython console>", line 1, in <module> UnicodeEncodeError: 'ascii' codec can't encode characters in position 0-1: ordinal not in range(128) Can someone explain what's going on here? Why does it matter whether the unicode data is in a plain unicode string or stored in an Exception object? And why does this fix it: >>> bar = u"foo2 is %s" % foo2 >>> bar u'foo2 is \xc3\x89milie and Jua\xc3\xb1 are turncoats.' I am quite confused! Thanks for the help! UPDATE: My coding buddy Randall has added to my confusion in an attempt to help me! Send in the reinforcements to explain how this is supposed to make sense: >>> class A: ... def __str__(self): return "string" ... def __unicode__(self): return "unicode" ... >>> "%s %s" % (u'niño', A()) u'ni\xc3\xb1o unicode' >>> "%s %s" % (A(), u'niño') u'string ni\xc3\xb1o' Note that the order of the arguments here determines which method is called!

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• There is a Default instance of form in VB.Net but not in C#, WHY?

  - by Shekhar_Pro

  I'm just curious to know that there is The (Name) property, which represents the name of the Form class.This property is used within the namespace to uniquely identify the class that the Form is an instance of and, in the case of Visual Basic, is used to access the default instance of the form. Now where this Default Instance come from, why can't C# have a equivalent method to this. Also for example to show a form in C# we do something like this: //Only method Form1 frm = new Form1(); frm.Show(); But in VB.Net we have both ways to do it: //'First common method (used slash because editor wouldn't format it properly) Form1.Show(); //'Second method Dim frm as New Form1(); frm.Show(); My question comes from this first method. What is this Form1, is it an instance of Form1 or the Form1 class itself. Now as i mentioned above the Form name is the Default instance in VB.Net. But we also know that Form1 is a class defined in Designer so how can the names be same for both the Instance and class name. If Form1 is Class then there is no (Static\Shared) method named Show(). So where does this method come from. And finally why C# can't have an equivalent of this. If there some mistake in my question Please let me know *I've checked this on stackoverflow, but couldn't find an answer to this.If you do find then please give a link to it.*

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• Why do you need "extern C" for in C++ callbacks to C functions?

  - by Artyom

  Hello, I find such examples in Boost code. namespace boost { namespace { extern "C" void *thread_proxy(void *f) { .... } } // anonymous void thread::thread_start(...) { ... pthread_create(something,0,&thread_proxy,something_else); ... } } // boost Why do you actually need this extern "C"? It is clear that thread_proxy function is private internal and I do not expect that it would be mangled as "thread_proxy" because I actually do not need it mangled at all. In fact in all my code that I had written and that runs on may platforms I never used extern "C" and this had worked as-as with normal functions. Why extern "C" is added? My problem is that extern "C" function pollute global name-space and they do not actually hidden as author expects. This is not duplicate! I'm not talking about mangling and external linkage. It is obvious in this code that external linkage is unwanted!

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• byte + byte = int... why?

  - by Robert C. Cartaino

  Looking at this C# code... byte x = 1; byte y = 2; byte z = x + y; // ERROR: Cannot implicitly convert type 'int' to 'byte' The result of any math performed on byte (or short) types is implicitly cast back to an integer. The solution is to explicitly cast the result back to a byte, so... byte z = (byte)(x + y); // works What I am wondering is why? Is it architectural? Philosophical? We have: int + int = int long + long = long float + float = float double + double = double So why not: byte + byte = byte short + short = short ? A bit of background: I am performing a long list of calculations on "small numbers" (i.e. < 8) and storing the intermediate results in a large array. Using a byte array (instead of an int array) is faster (because of cache hits). But the extensive byte-casts spread through the code make it that much more unreadable.

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• Why does this program require MSVCR80.dll and what's the best solution for this kinda problem?

  - by Runner

  #include <gtk/gtk.h> int main( int argc, char *argv[] ) { GtkWidget *window; gtk_init (&argc, &argv); window = gtk_window_new (GTK_WINDOW_TOPLEVEL); gtk_widget_show (window); gtk_main (); return 0; } I tried putting various versions of MSVCR80.dll under the same directory as the generated executable(via cmake),but none matched. Is there a general solution for this kinda problem? UPDATE Some answers recommend install the VS redist,but I'm not sure whether or not it will affect my installed Visual Studio 9, can someone confirm? Manifest file of the executable <assembly xmlns="urn:schemas-microsoft-com:asm.v1" manifestVersion="1.0"> <trustInfo xmlns="urn:schemas-microsoft-com:asm.v3"> <security> <requestedPrivileges> <requestedExecutionLevel level="asInvoker" uiAccess="false"></requestedExecutionLevel> </requestedPrivileges> </security> </trustInfo> <dependency> <dependentAssembly> <assemblyIdentity type="win32" name="Microsoft.VC90.DebugCRT" version="9.0.21022.8" processorArchitecture="x86" publicKeyToken="1fc8b3b9a1e18e3b"></assemblyIdentity> </dependentAssembly> </dependency> </assembly> It seems the manifest file says it should use the MSVCR90, why it always reporting missing MSVCR80.dll? FOUND After spending several hours on it,finally I found it's caused by this setting in PATH: D:\MATLAB\R2007b\bin\win32 After removing it all works fine.But why can that setting affect my running executable from using msvcr90 to msvcr80 ???

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• Why does setting the margin on a div not affect the position of child content?

  - by DanM

  I'd like to understand a little more clearly how css margins work with divs and child content. If I try this... <div style="clear: both; margin-top: 2em;"> <input type="submit" value="Save" /> </div> ...the Save button is right up against the User Role (margin fail): If I change it to this... <div style="clear: both;"> <input style="margin-top: 2em;" type="submit" value="Save" /> </div> ...there is a gap between the Save button and the User Role (margin win): Questions: Can someone explain what I'm observing? Why doesn't putting a margin on the div cause the input to move down? Why must I put the margin on the input itself? There must be some fundamental law of css I am not grasping.

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• Why don't I need to bind my vertex buffer object before calling glDrawArrays?

  - by valmo

  I'm a bit confused why this still renders. I thought you need to bind a vertex buffer object so that glDrawArrays knows which vertex buffer to use. Here is my initialisation code.. // Create and bind vertex array to store vertex attribute states. glGenVertexArraysOES(NUM_VERTEX_ARRAYS, &m_vertexArray); glBindVertexArrayOES(m_vertexArray); // Create and bind vertex buffer to store vertex data. glGenBuffers(NUM_VERTEX_BUFFERS, &m_vertexBuffer); glBindBuffer(GL_ARRAY_BUFFER, m_vertexBuffer); glBufferData(GL_ARRAY_BUFFER, sizeof(Vertex) * 36, &m_vertices[0], GL_STATIC_DRAW); glEnableVertexAttribArray(VertexAttribPosition); glVertexAttribPointer(VertexAttribPosition, 3, GL_FLOAT, GL_FALSE, 24, BUFFER_OFFSET(0)); glEnableVertexAttribArray(VertexAttribNormal); glVertexAttribPointer(VertexAttribNormal, 3, GL_FLOAT, GL_FALSE, 24, BUFFER_OFFSET(12)); glBindBuffer(GL_ARRAY_BUFFER, 0); glBindVertexArrayOES(0); Here is my render code. I'm confused why glDrawArrays still works when I bind 0 to GL_ARRAY_BUFFER. glBindVertexArrayOES(m_vertexArray); glBindBuffer(GL_ARRAY_BUFFER, 0); glDrawArrays(GL_TRIANGLES, 0, 36); glBindVertexArrayOES(0);

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• Why would using a Temp table be faster than a nested query?

  - by Mongus Pong

  We are trying to optimise some of our queries. One query is doing the following: SELECT t.TaskID, t.Name as Task, '' as Tracker, t.ClientID, (<complex subquery>) Date, INTO [#Gadget] FROM task t SELECT TOP 500 TaskID, Task, Tracker, ClientID, dbo.GetClientDisplayName(ClientID) as Client FROM [#Gadget] order by CASE WHEN Date IS NULL THEN 1 ELSE 0 END , Date ASC DROP TABLE [#Gadget] (I have removed the complex subquery, cos I dont think its relevant other than to explain why this query has been done as a two stage process.) Now I would have thought it would be far more efficient to merge this down into a single query using subqueries as : SELECT TOP 500 TaskID, Task, Tracker, ClientID, dbo.GetClientDisplayName(ClientID) FROM ( SELECT t.TaskID, t.Name as Task, '' as Tracker, t.ClientID, (<complex subquery>) Date, FROM task t ) as sub order by CASE WHEN Date IS NULL THEN 1 ELSE 0 END , Date ASC This would give the optimiser better information to work out what was going on and avoid any temporary tables. It should be faster. But it turns out it is a lot slower. 8 seconds vs under 5 seconds. I cant work out why this would be the case as all my knowledge of databases imply that subqueries would always be faster than using temporary tables. Can anyone explain what could be going on!?!?

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• Why is it that an int in C++ that isnt initialized (then used) doesn't return an error?

  - by omizzle

  I am new to C++ (just starting). I come from a Java background and I was trying out the following piece of code that would sum the numbers between 1 and 10 (inclusive) and then print out the sum: /* * File: main.cpp * Author: omarestrella * * Created on June 7, 2010, 8:02 PM */ #include <cstdlib> #include <iostream> using namespace std; int main() { int sum; for(int x = 1; x <= 10; x++) { sum += x; } cout << "The sum is: " << sum << endl; return 0; } When I ran it it kept printing 32822 for the sum. I knew the answer was supposed to be 55 and realized that its print the max value for a short (32767) plus 55. Changing int sum; to int sum = 0; would work (as it should, since the variable needs to be initialized!). Why does this behavior happen, though? Why doesnt the compiler warn you about something like this? I know Java screams at you when something isnt initialized. Thank you.

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• Are background threads a bad idea? Why?

  - by Matt Grande

  So I've been told what I'm doing here is wrong, but I'm not sure why. I have a webpage that imports a CSV file with document numbers to perform an expensive operation on. I've put the expensive operation into a background thread to prevent it from blocking the application. Here's what I have in a nutshell. protected void ButtonUpload_Click(object sender, EventArgs e) { if (FileUploadCSV.HasFile) { string fileText; using (var sr = new StreamReader(FileUploadCSV.FileContent)) { fileText = sr.ReadToEnd(); } var documentNumbers = fileText.Split(new[] {',', '\n', '\r'}, StringSplitOptions.RemoveEmptyEntries); ThreadStart threadStart = () => AnotherClass.ExpensiveOperation(documentNumbers); var thread = new Thread(threadStart) {IsBackground = true}; thread.Start(); } } (obviously with some error checking & messages for users thrown in) So my three-fold question is: a) Is this a bad idea? b) Why is this a bad idea? c) What would you do instead?

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• Why might this work on my server but not my schools?

  - by Doug

  I created a captcha just now, and it works PERFECTLY on my own server. On the school's server, it doesn't generate an image. Why might this be? The difference in code is one line. *Edit:*Originally, it was working, but I deleted the directory by mistake and I do not know why did it suddenly work in the first place. Source code on school server: <?php session_save_path("/ichanged/this/path/for/this/post/"); session_start(); $img=imagecreatefromjpeg("bg.jpg"); if( empty($_SESSION['captcha_numbers']) ) { $captcha_numbers = 'error'; } else { $captcha_numbers = $_SESSION['captcha_numbers']; } $image_numbers=$captcha_numbers; $red=rand(100,150); $green=rand(100,255); $blue=rand(100,255); $color=imagecolorallocate($img,255-$red,255-$green,255-$blue); $text=imagettftext($img,12,rand(-7,7),rand(10,20),rand(20,30),$color,"fonts/M04.TTF",$image_numbers); header("Content-type:image/jpeg"); header("Content-Disposition:inline ; filename=secure.jpg"); imagejpeg($img); ?> Source code on my server: <?php session_start(); $img=imagecreatefromjpeg("bg.jpg"); if( empty($_SESSION['captcha_numbers']) ) { $captcha_numbers = 'error'; } else { $captcha_numbers = $_SESSION['captcha_numbers']; } $image_numbers=$captcha_numbers; $red=rand(100,150); $green=rand(100,255); $blue=rand(100,255); $color=imagecolorallocate($img,255-$red,255-$green,255-$blue); $text=imagettftext($img,12,rand(-7,7),rand(10,20),rand(20,30),$color,"fonts/M04.TTF",$image_numbers); header("Content-type:image/jpeg"); header("Content-Disposition:inline ; filename=secure.jpg"); imagejpeg($img); ?>

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• Why is Excel's 'Evaluate' method a general expression evaluator?

  - by jtolle

  A few questions have come up recently involving the Application.Evaluate method callable from Excel VBA. The old XLM macro language also exposes an EVALUATE() function. Both can be quite useful. Does anyone know why the evaluator that is exposed can handle general expressions, though? My own hunch is that Excel needed to give people a way to get ranges from string addresses, and to get the value of named formulas, and just opening a portal to the expression evaluator was the easiest way. (The help for the VBA version does say its purpose it to "convert a Microsoft Excel name to an object or a value".) But of course you don't need the ability to evaluate arbitrary expressions just to do that. (That is, Excel could provide a Name.Evaluate method or something instead.) Application.Evaluate seems kind of...unfinished. It's full behavior isn't very well documented, and there are quite a few quirks and limitations (as described by Charles Williams here: http://www.decisionmodels.com/calcsecretsh.htm) with what is exposed. I suppose the answer could be simply "why not expose it?", but I'd be interested to know what design decisions led to this feature taking the form that it does. Failing that, I'd be interested to hear other hunches.

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• Why do you need "extern C" for C++ callbacks to C functions?

  - by Artyom

  Hello, I find such examples in Boost code. namespace boost { namespace { extern "C" void *thread_proxy(void *f) { .... } } // anonymous void thread::thread_start(...) { ... pthread_create(something,0,&thread_proxy,something_else); ... } } // boost Why do you actually need this extern "C"? It is clear that thread_proxy function is private internal and I do not expect that it would be mangled as "thread_proxy" because I actually do not need it mangled at all. In fact in all my code that I had written and that runs on may platforms I never used extern "C" and this had worked as-as with normal functions. Why extern "C" is added? My problem is that extern "C" function pollute global name-space and they do not actually hidden as author expects. This is not duplicate! I'm not talking about mangling and external linkage. It is obvious in this code that external linkage is unwanted! Answer: Calling convention of C and C++ functions are not necessary the same, so you need to create one with C calling convention. See 7.5 (p4) of C++ standard.

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• Why do I get this exception? {An item with the same key has already been added."})

  - by Alan

  Aknittel NewSellerID is the result of a lookup on tblSellers. These tables (tblSellerListings and tblSellers) are not "officially" joined with a foreign key relationship, either in the model or in the database, but I want some referential integrity maintained for the future. So my issue remains. Why do I get the exception ({"An item with the same key has already been added."}) with this code, if I don't begin each iteration of the foreach loop with a new ObjectContext and end it with SaveChanges, which I think will affect performance. Also, could you tell me why ORCSolutionsDataService.tblSellerListings (An ADO.NET DataServices/WCF object is not IDisposable, like LINQ to Entities?? ============================================== // Add listings to previous seller int NewSellerID = 0; // Look up existing Seller key using SellerUniqueEBAYID var qryCurrentSeller = from s in service.tblSellers where s.SellerEBAYUserID == SellerUserID select s; foreach (var s in qryCurrentSeller) NewSellerID = s.SellerID; // Save the selected listings for this seller foreach (DataGridViewRow dgr in dgvRows) { ORCSolutionsDataService.tblSellerListings NewSellerListing = new ORCSolutionsDataService.tblSellerListings(); NewSellerListing.ItemID = dgr.Cells["txtSellerItemID"].Value.ToString(); NewSellerListing.Title = dgr.Cells["txtSellerItemTitle"].Value.ToString(); NewSellerListing.CurrentPrice = Convert.ToDecimal(dgr.Cells["txtSellerItemPrice"].Value); NewSellerListing.QuantitySold = Convert.ToInt32(dgr.Cells["txtSellerItemSold"].Value); NewSellerListing.EndTime = Convert.ToDateTime(dgr.Cells["txtSellerItemEnds"].Value); NewSellerListing.CategoryName = dgr.Cells["txtSellerItemCategory"].Value.ToString(); NewSellerListing.ExtendedPrice = Convert.ToDecimal(dgr.Cells["txtExtendedReceipts"].Value); NewSellerListing.RetrievedDtime = Convert.ToDateTime(dtSellerDataRetrieved.ToString()); NewSellerListing.SellerID = NewSellerID; service.AddTotblSellerListings(NewSellerListing); } service.SaveChanges(); } catch (Exception ex) { MessageBox.Show("Unable to add a new case. Exception: " + ex.Message); }

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• Why do I need to give my options a value attribute in my dropdown? JQuery related.

  - by Alex

  So far in my web developing experiences, I've noticed that almost all web developers/designers choose to give their options in a select a value like so: <select name="foo"> <option value="bar">BarCheese</option> // etc. // etc. </select> Is this because it is best practice to do so? I ask this because I have done a lot of work with jQuery and dropdown's lately, and sometimes I get really annoyed when I have to check something like: $('select[name=foo]').val() == "bar"); To me, many times that seems less clear than just being able to check the val() against BarCheese. So why is it that most web developers/designers specify a value paramater instead of just letting the options actual value be its value? And yes, if the option has a value attribute I know I can do something like this: $('select[name=foo] option:contains("BarCheese")').attr('selected', 'selected'); But I would still really like to know why this is done. Thanks!!

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• C++ -- Why should we use operator -> to access member functions of a SmartPtr?

  - by q0987

  Hello all, The question is given in the last two lines of code. template<class T> // template class for smart class SmartPtr { // pointers-to-T objects public: SmartPtr(T* realPtr = 0); T* operator->() const; T& operator*() const; T* Detach( void ) { T* pData = pointee; pointee = NULL; return pData; } private: T *pointee; ... }; class TestClass {} SmartPtr<TestClass> sPtr(new TestClass); TestClass* ptrA = sPtr->Detach(); // why I always see people use this method to access member functions of a Smart pointer. We can use sPtr-> b/c we have defined operator->() in SmartPtr. TestClass* ptrB = sPtr.Detach(); // Question: Is this a valid C++ way? If not, why? Thank you

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• Why do we need Audit Columns in Database Tables?

  - by Software Enthusiastic

  Hi I have seen many database designs having following audit columns on all the tables... Created By Create DateTime Updated By Upldated DateTime From one perspective I see tables from the following view... Entity Tables: Good candidate for Audit columns) Reference Tables: Audit columns may or may not required. In some case last update information is not at all required because record is never going to be modified.) Reference Data Tables Like Country Names, Entity State etc... Audit columns may not required because these information is created only during system installation time, and never going to be changed. I have seen many designers blindly put all audit columns to all tables, is this practice good, if yes what could be the reason... I just want to know because to me it seems illogical. It is difficult for me to figure out why do they design their db this way? I am not saying they are wrong or right, just want to know the WHY? You can also suggest me, if there is an alternative auditing patter or solution available... Thanks and Regards

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• Why does reusing arrays increase performance so significantly in c#?

  - by Willem

  In my code, I perform a large number of tasks, each requiring a large array of memory to temporarily store data. I have about 500 tasks. At the beginning of each task, I allocate memory for an array : double[] tempDoubleArray = new double[M]; M is a large number depending on the precise task, typically around 2000000. Now, I do some complex calculations to fill the array, and in the end I use the array to determine the result of this task. After that, the tempDoubleArray goes out of scope. Profiling reveals that the calls to construct the arrays are time consuming. So, I decide to try and reuse the array, by making it static and reusing it. It requires some additional juggling to figure out the minimum size of the array, requiring an extra pass through all tasks, but it works. Now, the program is much faster (from 80 sec to 22 sec for execution of all tasks). double[] tempDoubleArray = staticDoubleArray; However, I'm a bit in the dark of why precisely this works so well. Id say that in the original code, when the tempDoubleArray goes out of scope, it can be collected, so allocating a new array should not be that hard right? I ask this because understanding why it works might help me figuring out other ways to achieve the same effect, and because I would like to know in what cases allocation gives performance issues.

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• Scala XML API: Why allow NodeSeq as attribute values?

  - by Synesso

  It seems attribute values are of type Seq[Node]. scala> <a b="1"/>.attribute("b") res11: Option[Seq[scala.xml.Node]] = Some(1) This means you can assign XML as an attribute value. scala> <a b={<z><x/></z>}/>.attribute("b") res16: Option[Seq[scala.xml.Node]] = Some(<z><x></x></z>) scala> <a b={<z><x/></z>}/>.attribute("b").map(_ \ "x") res17: Option[scala.xml.NodeSeq] = Some(<x></x>) scala> new xml.PrettyPrinter(120, 2).format(<a b={<z><x/></z>}/>) res19: String = <a b="<z><x></x></z>"></a> This seems funky to me. I've never seen XML as attribute values in the real world. Why is it allowed? Why is an attribute value simply not of type String?

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• Why does the roll_out event fire in this code?

  - by user339681

  I have made this simple example to demonstrate some problems I'm having. <?xml version="1.0" encoding="utf-8"?> <mx:Application xmlns:mx="http://www.adobe.com/2006/mxml" layout="absolute"> <mx:Canvas id="buttonCanvas" x="100" y="100" opaqueBackground="#000000" width="80%" height="300" creationComplete="init(event)"> <mx:Button x="5" y="5"/> <mx:Button x="5" y="50"/> </mx:Canvas> <mx:Script> <![CDATA[ private function init(event:Event):void{ buttonCanvas.addEventListener(MouseEvent.ROLL_OUT, function(event:Event):void{ buttonCanvas.opaqueBackground=(buttonCanvas.opaqueBackground==0)? 0x666666:0; }); } ]]> </mx:Script> </mx:Application> I don't understand the following: Why doesn't the percentage nor absolute dimensions affect the canvas? Why does the roll_out event fire when the mouse leaves a button (even when it is still inside the canvas). I'm going nuts trying to figure this out. Any help would be greatly appreciated!

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