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• Replacing a C++ ActiveX component with a .NET implementation?

  - by Leon Breedt

  I have existing managed and unmanaged software using an ActiveX component supplied by a third party to perform some communications, but it is now required that this communication be routed through my application. Ideally I'd be able to install a .NET component which will expose exactly the same interface, and will be usable as a drop-in replacement. However, I am running into the limits of my understanding of COM, which admittedly is quite minimal. How best to ensure that my implementation of the interface is 100% binary compatible with the existing object? How do I ensure that applications use my implementation of the interface instead of the legacy implementation? Is it simply a matter of registering my implementation, and unregistering the legacy one? How do I ensure it's a "drop-in" replacement, and requires no changes to existing software? How do I ensure unmanaged code can use it without issue? Note: I am able to require that .NET 4.0 be used, if that will make things simpler.

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• Multiple things at once (Threads?)

  - by Jonathan

  All, What is a really simple way of having a program do more than one thing at once, even if the computer does not necessarily have multiple 'cores'. Can I do this by creating more than one Thread? My goal is to be able to have two computers networked (through Sockets) to respond to each-other's requests, while my program will at the same time be able to be managing a UI. I want the server to potentially handle more than one client at the same time as well. My understanding is that the communication is done with BufferedReader.readLine() and PrintWriter.println(). My problem is that I want the server to be waiting on multiple readLine() requests, and also be doing other things. How do I handle this? Many thanks, Jonathan

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• UITableViewController setting delegates and datasource

  - by the_great_monkey

  Hi iOS gurus, I'm a little bit confused about UITableViewController... As far as I concern they are typically the delegate and datasource of the UITableView (although it can be made such that they are different). However in some cases, like when embedding a UITableViewController in a UITabBarViewController in Interface Builder, we initiate our table view controller in IB. Therefore in my understanding, the default initialiser is being called. But in this case, I have this piece of code: @interface Settings : UITableViewController { } And in the IB I see that the delegate and datasource of the UITableView is hooked up to this class. My question is, why is it that we don't need to explicitly say that it is following: @interface Settings : UITableViewController <UITableViewDelegate, UITableViewDataSource> { } And in the .m file: - (void)viewDidLoad { [super viewDidLoad]; [tableView setDelegate:self]; [tableView setDataSource:self]; } I have indeed stumbled upon some cases where I have to explicitly code the above a few times to make something work. Although it is still a mystery for me as of why it is needed...

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• How to start coding the "Dining Philosophers" simulation?

  - by GrizzlyGuru

  I'm not a beginner at C# but I really need to increase my understanding, so I've picked a classic deadlock problem to code to help teach myself some of the more advanced concepts of C#. The Dining Philosophers Problem seems like a good one, but I need a little help to get started. I know I need to approach the "diners" as objects, but to simulate the random delays between eating, should I look to threading with each diner in a separate thread? Do I need some kind of "master" to monitor all the actions? Any general design concept advice is welcome, but I'd like to do the grunt programming as an exercise. Thanks!

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• Does importing of packages change visibility of classes?

  - by Roman

  I jsut learned that A class may be declared with the modifier public, in which case that class is visible to all classes everywhere. If a class has no modifier (the default, also known as package-private), it is visible only within its own package. This is a clear statement. But this information interfere with my understanding of importing of packages (which easily can be wrong). I thought that importing a package I make classes from the imported package visible to the importing class. So, how does it work? Are public classes visible to all classes everywhere under condition that the package containing the public class is imported? Or there is not such a condition? What about the package-private classes? They are invisible no mater if the containing package was imported or not? ADDED: It seems to me that I got 2 answers which are marked as good (up-voted) and which contradict eachother.

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• Setting a form field's value during validation

  - by LaundroMat

  I read about this issue already, but I'm having trouble understanding why I can't change the value of a form's field during validation. I have a form where a user can enter a decimal value. This value has to be higher than the initial value of the item the user is changing. During clean(), the value that was entered is checked against the item's previous value. I would like to be able to re-set the form field's value to the item's initial value when a user enters a lower value. Is this possible from within the clean() method, or am I forced to do this in the view? Somehow, it doesn't feel right to do this in the view... (To make matters more complicated, the form's fields are built up dynamically, meaning I have to override the form's clean() method instead of using the clean_() method).

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• How can I (is there a way to) convert an HRESULT into a system specific error message?

  - by Billy ONeal

  According to this, there's no way to convert a HRESULT error code into a Win32 error code. Therefore (at least to my understanding), my use of FormatMessage in order to generate error messages (i.e. std::wstring Exception::GetWideMessage() const { using std::tr1::shared_ptr; shared_ptr<void> buff; LPWSTR buffPtr; DWORD bufferLength = FormatMessageW( FORMAT_MESSAGE_FROM_SYSTEM | FORMAT_MESSAGE_ALLOCATE_BUFFER | FORMAT_MESSAGE_IGNORE_INSERTS, NULL, GetErrorCode(), 0, reinterpret_cast<LPWSTR>(&buffPtr), 0, NULL); buff.reset(buffPtr, LocalFreeHelper()); return std::wstring(buffPtr, bufferLength); } ) does not work for HRESULTs. How do I generate these kinds of system-specific error strings for HRESULTs?

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• How Matlab calculates the camera view angle?

  - by iman

  I am using matlab to visualise a scene. In order to zoom in the scene, I can do that by eather: - Fix the cameraposition and the cameratarget and change the cameraviewangle.or - Fix the cameratarget and the cameraview angle and moving the camera along the viewing line (defined by the cameraPosition and the cameraTarget). I know how to set the values of cameraposition CameraTarget and viewangle, but I do not how to define the optimal view angle. In auto mode of cameraviewangle, matlab calculate the smalest view angle that capture all the scene from the specefied camera position. I appreciate any help in understanding this. Iman

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• Encog 3.0 backpropagation

  - by Mohamed Shouman

  I have a question...I am using Encog framework to train a network using BP. I am training the network using images that has some object say a cat, telling the network which images are cats and which are not. Bellow are my Neural Network results actual=0.1545868370551181 ideal=0.0,actual=0.797896306829758 ideal=1.0,actual=0.1545868370551181 ideal=0.0,actual=0.797896306829758 ideal=1.0 It is my understanding that since different pictures are presented to network some look like cat for example then they should have higher percentage...but i keep getting same percentage for any pic that has a cat which is 0.79 and for other pics i get 0.15...how can i solve this issue!, what is the intuition behind whats going on! Many thanks

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• Can't edit IORegistryEntry

  - by yangumi

  Hi, I am creating a software on Mac and I would like to change the value of an IORegistryEntry. I can view it on the IORegistryExplorer, but I can't edit it. So it's my understanding that I have to edit it via code. Here is my code: CFMutableDictionaryRef matchingDict = IOServiceNameMatching("AppleUSBMultitouchDriver"); io_service_t service = IOServiceGetMatchingService(kIOMasterPortDefault, matchingDict); if(service) { CFStringRef manufacturer = IORegistryEntryCreateCFProperty(service, CFSTR("Manufacturer"), kCFAllocatorDefault,0); NSLog(@"%@", (NSString*)manufacturer); kern_return_t err = IORegistryEntrySetCFProperty(service, CFSTR("Manufacturer"), CFSTR("test")); NSLog(@"error = %d", err); } This will output 2010-04-10 16:09:09.015 Test[41548:a0f] Apple Inc. 2010-04-10 16:09:09.015 Test[41548:a0f] error = 0 But after I check the value in the IORegistryExplorer, it still doesn't change. Does anybody have any suggestions? Thank you

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• Implementing Clonable in Java

  - by Artium

  In which cases should I use this way: public A clone() throws CloneNotSupportedException { A clone = (A)super.clone(); clone.x= this.x; return clone; } And in which cases should I use that way: public ShiftedStack clone() throws CloneNotSupportedException { return new A(this.x); } What should I do if x is final and I want to use the first way? Regarding the first way, I understand it like this: we clone the super class and up-cast it, leading to some members uninitialized. After this initialize these members. Is my understanding correct? Thank you.

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• Is the offical Sun Java EE tutorial the best way to learn how to make Java web apps?

  - by Nick

  I've been a web developer for almost a decade. I've mostly used classic ASP/JavaScript and I'd like to move into Java based apps. I have a decent understanding of Java itself (enough to know how to lookup what I don't know) and I spent some time doing minor work on a JSF/Spring/Hibernate app, but from what a trusted coworker told me, this application is the example of what not to do. I want to learn the really hardcore stuff (EJBs, HA Clustering, etc), but I know I have to walk before I can run. Is the Sun Tutorial the best place to start? Or is there an definitive book (like K&R for C or Gang of Four for design patterns) that I should buy?

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• How the websocket bi-directional concept work?

  - by GMsoF

  I think the main difference between websocket and http streaming (I am not refering to polling and long polling) is websocket allows bi-directional communication which is similar to usual raw socket programming. (above is my understanding, could be wrong, feel free to correct me.) My question is how the web client (browser) continue to send another request in the already-opened websocket? Usual http request will treat another request as new socket connection, but websocket does not, that is why I am confused, how it achieve that? It should be handled in Server side or Client (browser) side?

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• javasrcipt asyncronous function

  - by Ben

  Hi there, i have a problem understanding how this could/should be solved. I have two functions. In the first function ( I call it loadData() ) I'm doing an asyncronous request to the server to load some data. In the second function ( saveData() ) I'm also doing an asyn request to the server to write some data. In the callback of this request I'm callin loadData() to refresh the data. Now the problem: In the saveData() function I want to wait for loadData() to be finished bevore I show a dialog (like alert('Data saved')) I guess this is a common problem, but I couldn't find the solution for it (if there is one..) A solution would be to make the requests syncronous, but the framework I'm using doesn't offer that and I hope there's a better solution.. Thanks to all!

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• How to manage different form contexts of same form element in single DOM tree

  - by nimp

  Hi, As my question title could be bit unclear to you (I tried best), following is what I'm exactly trying to do. I'm having a form element (say a user_info form), where such form elements will be generated for different users by java script and displayed in different js tabs (example: dojo tabs). once form elements are generated, later I need to react on user actions performed on different html elements defined inside user_info form. In this case I need to identify what is the context (in which user_info form element) in which user is working on. The simplest example would be how to retrieve form id of the form in which user actions are being performed. According to my understanding, I can not simply retrieve from by form id, because now DOM tree contains duplicate form instances of the same from element. So, IS there anyway, I could identify form context based on the user actions on its input elements. Thank You.

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• PHP no wait sem_acquire?

  - by SerEnder

  Not a specific code question, but more of a general coding question. I'm trying to use a semaphore in a work project to limit the number of users that can access certain processes at a concurrent time. From my understanding the following: $iKey = ftock($sSomeFileLocation,'sOneCharacterString'); //Generate the key if($sem_id = sem_get($iKey){ //1 user allowed if(sem_acquire($sem_id)){ //Do the limited process here sem_release($sem_id); } } The problem that I see here is that if there is already one user who has the semaphore key, then the next user just waits until the first user is done rather than just faulting out. Anyone know of a way that if the max_acquire number has been reached, sem_acquire (or similar) will just return false? Thanks

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• Hibernate entities stored as HttpSession attribute values

  - by njudge

  I'm dealing with a legacy Java application with a large, fairly messy codebase. There's a fairly standard 'User' object that gets stored in the HttpSession between requests, so the servlets do stuff like this at the top: HttpSession session = request.getSession(true); User user = (User)session.getAttribute("User"); The old user authentication layer (which I won't describe; suffice to say, it did not use a database) is being replaced with code mapped to the DB with Hibernate. So 'User' is now a Hibernate entity. My understanding of Hibernate object life cycles is a little fuzzy, but it seems like storing 'User' in the HttpSession now becomes a problem, because it will be retrieved in a different transaction during the next request. What is the right thing to be doing here? Can I just use the Hibernate Session object's update() method to reattach the User instance the next time around? Do I need to?

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• using time() to measure how long a function takes

  - by hap497

  Hi, I am trying to use time() to measure various points of my program. http://www.cplusplus.com/reference/clibrary/ctime/time/ What I don't understand is why the values in the before and after are Different? I understanding this is not the best way to profile my program, I just want to see how long does something take. printf ("**MyProgram::before time= %ld\n", time(NULL)); doSomthing(); doSomthingLong(); printf ("**MyProgram::after time= %ld\n", time(NULL)); Thank you.

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• How to get data in the servlet send via dojo.xhrPost

  - by snell

  > var xhrArgs = { > url: '/mum/proxy/http/localhost:8080/DemoProject/MyServlet', > postData:' MyDataToBeSend', > handleAs: 'text', > load: function(data) { }, > error: function(error) {alert(error);}}; var ret = > dojo.xhrGet(xhrArgs); Hi All, I have written the above code in Javascript to send data to a servlet. But I am not understanding how to get the postData in the servlet.

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• Removing the last character of a string IF it is $variable

  - by KeenLearner

  Hi there, I've made a little script to convert titles into url friendly things. ie: 'I am a title' becomes 'I_am_a_title' My script basically goes through and turns spaces, apostrophes, commas etc etc into an underscore. The problem is, sometimes my url's end up like this: 'i_am_a_title_' with a trailing underscore... So i figure, add a little bit to go through and search to see if the last character is an underscore on the final result, and if it is, then swap it. I looked into the strrchr() function but I seem to be hitting a wall of my own understanding. How is this sort of thing accomplished?

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• is putting N in front of strings in scripts considered a "best practice"?

  - by jcollum

  Let's say I have a table that has a varchar field. If I do an insert like this: INSERT MyTable SELECT N'the string goes here' Is there any fundamental difference between that and: INSERT MyTable SELECT 'the string goes here' My understanding was that you'd only have a problem if the string contained a Unicode character and the target column wasn't unicode. Other than that, SQL deals with it just fine and converts the string with the N'' into a varchar field (basically ignores the N). I was under the impression that N in front of strings was a good practice, but I'm unable to find any discussion of it that I'd consider definitive. Title may need improvement, feel free.

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• How to see contents of deployed datasource?

  - by callisto

  I've inherited a project (without a handy handover) that contains reports published to a Reporting Server (2005). MY SSRS knowledge is 4 years stale, so I need your help. I need to edit one of the published reports, is this possible? I also want to peek into the Data Source on the RS, coz that's probably where I can change stuff. I'll add more info as I get a better understanding of what exactly to ask. EDIT: I found a project for some of the reports, opened up in VS2005 BI. Still, how do see where the Data Source gets its data? It brins back 56 fields but I dont know which tables/stored procs/queries are used to get these.

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• C99 strict aliasing rules in C++ (GCC)

  - by Checkers

  As far as I understand, GCC supports all of its C99 features in C++. But how is C99 strict aliasing handled in C++ code? I know that casting with C casts between unrelated types is not strict-aliasing-safe and may generate incorrect code, but what about C++? Since strict aliasing is not part of C++ standard (is that correct?), GCC must be specifying the semantics itself. I figure const_cast and static_cast cast between related types, hence they are safe, while reinterpret_cast can break strict aliasing rules. Is this a correct understanding?

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• Why is volatile not considered useful in multithreaded C or C++ programming?

  - by Michael E

  As demonstrated in this answer I recently posted, I seem to be confused about the utility (or lack thereof) of volatile in multi-threaded programming contexts. My understanding is this: any time a variable may be changed outside the flow of control of a piece of code accessing it, that variable should be declared to be volatile. Signal handlers, I/O registers, and variables modified by another thread all constitute such situations. So, if you have a global int foo, and foo is read by one thread and set atomically by another thread (probably using an appropriate machine instruction), the reading thread sees this situation in the same way it sees a variable tweaked by a signal handler or modified by an external hardware condition and thus foo should be declared volatile (or, for multithreaded situations, accessed with memory-fenced load, which is probably a better a solution). How and where am I wrong?

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• WPF: Creating instances of resources?

  - by oakskc

  I'm brand spanking new to WPF and am trying to play around with projects to better understand what I'm reading. My understanding of a resource is that it is the instance, you can't use it like a factory and create instances of it. For example, a XAML-defined rectangle. You can reference it, but you can't have numerous instances of it all over the surface. In WPF, what would be the way to do that? If I define a Rectangle as a resource with specific properties and wanted to have multiple instances of that within a dynamically-generated grid, how should I be going about it? Or is there a different way I should be trying to do this? Purely academic exercise with no real-world application.

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