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• Android Camera without Preview

  - by eyurdakul

  I am writing an android 1.5 application which starts just after boot-up. This is a service and should take a picture without preview. This app will log the light density in some areas whatever. I was able to take a picture but the picture was black. After googling like crazy, i came across a bug thread about it. If you don't generate a preview, the image will be black since android camera needs preview to setup exposure and focus. I've created a surfaceview and listener but the onSurfaceCreated event never gets fired. I guess the reason is, the surface is not being created visually. I've also seen some examples of calling the camera statically with MediaStore.CAPTURE_OR_SOMETHING which takes a picture and saves in the desired folder with two lines of code but it doesn't take a picture too. Do i need to use ipc and bindservice to call this function or do you have any suggestion to achieve my goal (taking a picture without preview) and if so, would you give me a small piece of code as example?

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• onPause/onResume activity issues

  - by Josh

  I have a small test application I am working on which has a timer that updates a textview to countdown from 100 to 0. That works fine, but now I am trying to pause the application if the user presses the back button on the phone and then restart the timer from where they left off when they reopen the app. Here is the code I am using: @Override public void onPause() { if(this._timer_time_remaining > 0) { this.timer.cancel(); } super.onPause(); Log.v("Pausing", String.format("Pausing with %d", this._timer_time_remaining)); } @Override public void onResume() { super.onResume(); Log.v("Resuming", String.format("Resuming with %d", this._timer_time_remaining)); if(this._timer_time_remaining > 0) { setContentView(R.layout.in_game); start_timer(this._timer_time_remaining); } } The start_timer() method creates a CountDownTimer which updates the textview in the onTick method and updates the this._timer_time_remaining int variable. CountDownTimer and _timer_time_remaining are both declared at the class level like this: private CountDownTimer timer; private int _timer_time_remaining; From the Log.v() prints I see that the _timer_time_remaining variable has the correct number of seconds stored when onPause is called, but it is set back to 0 when onResume starts. Why does the variable get reset? I thought that the application would continue to run in the background with the same values. Am I missing something? This is all declared in a class that extends Activity. Thanks in advance!

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• MATLAB Builder NE (.NET Assembly) Data type question

  - by Brett

  Hi coders, I am using MATLAB Builder NE (MATLAB's integrated .NET assmebly builder), but I am having an issue with data types. I have compiled a small, very simple, function in matlab and build it for .NET. I am able to call the namespace and even the function just fine. However, my function returns a value, and MATLAB defaults to returning it as an "object[]" data type. However, I know that the value is an integer, but I can't figure out how to cast it. My MATLAB function looks like this: function addValue = Myfunction(value1, value2) addValue=value1+value2; end Pretty simple right? And then in .NET I can call it as: xClass.addValue (1, 3, 4); where xClass is the name of the MATLAB built class but when I try: int x = xClass.addValue (1, 3, 4); C# errors out. Typical .NET casting (int) doesn't work. The compiler states it cannot convert object[] to int. Does anyone have experience with the .NET builder in MATLAB that can help me with this? It is really throwing me for a loop. I have scanned through most of the MATLAB BUILDER doc (484 pages!) with zero help. Thank you, Brett

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• Configuring ASP.NET MVC ActionLink format with GoDaddy shared hosting

  - by Maxim Z.

  Background I have a GoDaddy shared Windows hosting plan and I'm running into a small issue with multiple domains. Many people have previously reported such an issue, but I am not interested in trying to resolve that problem altogether; all I want to accomplish is to change the format of my ActionLinks. Issue Let's say the domain that is mapped to my root hosting directory is example.com. GoDaddy forces mapping of other domains to subdirectories of the root. For example, my second domain, example1.com, is mapped to example.com/example1. I uploaded my ASP.NET MVC site to such a subdirectory, only to find that ActionLinks that are for navigation have the following format: http://example1.com/example1/Controller/Action In other words, even when I use the domain that is mapped to the subdirectory, the subdirectory is still used in the URL. However, I noticed that I can also access the same path by going to: http://example1.com/Controller/Action (leaving out the subdirectory) What I want to achieve I want to have my ActionLinks automatically drop the subdirectory, as it is not required. Is this possible without changing the ActionLinks into plain-old URLs?

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• System.Threading.Timer keep reference to it.

  - by Daniel Bryars

  According to [http://msdn.microsoft.com/en-us/library/system.threading.timer.aspx][1] you need to keep a reference to a System.Threading.Timer to prevent it from being disposed. I've got a method like this: private void Delay(Action action, Int32 ms) { if (ms <= 0) { action(); } System.Threading.Timer timer = new System.Threading.Timer( (o) => action(), null, ms, System.Threading.Timeout.Infinite); } Which I don't think keeps a reference to the timer, I've not seen any problems so far, but that's probably because the delay periods used have been pretty small. Is the code above wrong? And if it is, how to I keep a reference to the Timer? I'm thinking something like this might work: class timerstate { internal volatile System.Threading.Timer Timer; }; private void Delay2(Action action, Int32 ms) { if (ms <= 0) { action(); } timerstate state = new timerstate(); lock (state) { state.Timer = new System.Threading.Timer( (o) => { lock (o) { action(); ((timerstate)o).Timer.Dispose(); } }, state, ms, System.Threading.Timeout.Infinite); } The locking business is so I can get the timer into the timerstate class before the delegate gets invoked. It all looks a little clunky to me. Perhaps I should regard the chance of the timer firing before it's finished constructing and assigned to the property in the timerstace instance as negligible and leave the locking out.

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• Google App Engine application instance recycling and response times...

  - by Konrad

  Hi, I posted this on GAE for Java group, but I hope to get some answers here quicker :) I decided to do some long-run performance tests on my application. I created some small client hitting app every 5-30 minutes and I run 3-5 of threads with such client. I noticed huge differenced in response times and started to investigate issue. I found reason very quick. I am experiencing same issues as described in following topics: Uneven response time between connection to server to first byte sent Application instances seem to be too aggressively recycled Getting 'Request was aborted after waiting too long to attempt to service your request.' after application idle I am using Springframework, it tkes around 18-20s to start app instance, which is causing response times to take from 1s (when requests hits running app - very rare) to 22s when fresh application is created. Is there any solution for this? I was thinking about creating most basic servlet performing critical tasks (serving API call) and leave UI as is. But then I would loose all benefits of Springframework. Is there any solution for this? After solving (hacking) numerous constrains of App Engine which I hit while developing my app that is the one I think will make me move out of App Engine... that's simply to much to all the time think how to win with GAE problems than how to solve my application problems... Any help? Regards Konrad

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• Base 128 or 256 Encoding for the Binary Lexical Octet Adhoc Transport Protocol?

  - by Randolpho

  I'm in the process of implementing a network driver for the Binary Lexical Octet Adhoc Transport (BLOAT) protocols in the hopes of replacing the TCP/UDP/IP stack with a much more flexible XML structure. BLOAT is detailed in RFC 3252, so if you're unfamiliar with the protocol I highly recommend you read the entire RFC before providing any comments. Don't worry, it's short and sweet; you might even enjoy it. Anyway, my problem is this: BLOAT requires that the payload be Base64 encoded which doesn't make sense to me. I mean, sure, it's the internet standard for binary payloads, but there are better, more efficient encodings available: Base128 and Base256, for example. That the RFC requires Base64 and doesn't allow for any other payload encoding really bothers me. To that end, I'm considering a small optional change to the protocol. Embrace and extend, right? Anyway, I'd like to modify the payload element to accept an encoding attribute, which can extend the encoding to Base128 or Base256, or even to other encodings I can't conceive of at the moment. If the encoding attribute isn't present, Base64 would be assumed. So my question is this: should I? I mean, BLOAT is an accepted standard, even if it isn't exactly omnipresent. If I make this change, will there be compatibility issues? I don't foresee any, but perhaps you, oh great Stack Overflow Community, can? If I do implement this change, should I contact the original RFC author? Should I offer a supplemental RFC?

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• split video (avi/h264) on keyframe

  - by m.sr

  Hallo. I have a big video file. ffmpeg, tcprobe and other tool say, it is an h264-stream in an AVI-container. Now i'd like to cut out small chunks form the video. Problem: The index of the video seam corrupted/destroyed. I kind of fixed this via mplayer -forceidx -saveidx <IndexFile> <BigVideoFile>. The Problem here is, that I'm now stuck with mplayer/mencoder which can use this index file via -loadidx <IndexFile>. I have tried correcting the index like described in man aviindex (mplayer -frames 0 -saveidx mpidx broken.avi ; aviindex -i mpidx -o tcindex ; avimerge -x tcindex -i broken.avi -o fixed.avi), but this didn't fix my video - meaning that most tools i've tested couldn't search in the video file. Problem: I sut out parts of the video via following command: mencoder -loadidx in.idx -ss 8578 -endpos 20 -oac faac -ovc x264 -sws 9 -lavfopts format=mp4 -x264encopts <LotsOfOpts> -of lavf -vf scale=800:-10,harddup in.avi -o out.mp4. Now here the problem is, that some videos are corrupted at the beginning. I think this is because the fact, that i do not necessarily cut at keyframe. Questions: What is the best way to fix the index of an avi "inline" so that every tool can again work as expected with it? How can i split at the keyframes? Is there an mencoder-option for this? Are Keyframes coming in a frequency? How to find out this frequency? (So with a bit of math it should be possible to calculate the next keyframe and cut there) Is ther perhaps some completely other way to split this movie? Doing it by hand is no option, i've to cut out 1000+ chunks ... Thanks a lot!

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• Python for a hobbyist programmer ( a few questions)

  - by Matt

  I'm a hobbyist programmer (only in TI-Basic before now), and after much, much, much debating with myself, I've decided to learn Python. I don't have a ton of free time to teach myself a hundred languages and all programming I do will be for personal use or for distributing to people who need them, so I decided that I needed one good, strong language to be good at. My questions: Is python powerful enough to handle most things that a typical programmer might do in his off-time? I have in mind things like complex stat generators based on user input for tabletop games, making small games, automate install processes, and build interactive websites, but probably a hundred things along those lines Does python handle networking tasks fairly well? Can python source be obscufated (mispelled I think), or is it going to be open-source by nature? The reason I ask this is because if I make something cool and distribute it, I don't want some idiot script kiddie to edit his own name in and say he wrote it And how popular is python, compared to other languages. Ideally, my language would be good and useful with help found online without extreme difficulty, but not so common that every idiot with computer knows python. I like the idea of knowing a slightly obscure language. Thanks a ton for any help you can provide.

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• Informix, NHibernate, TransactionScope interaction difficulties

  - by John Prideaux

  I have a small program that is trying to wrap an NHibernate insert into an Informix database in a TransactionScope object using the Informix .NET Provider. I am getting the error specified below. The code without the TransactionScope object works -- including when the insert is wrapped in an NHibernate session transaction. Any ideas on what the problem is? BTW, without the EnterpriseServicesInterop, the Informix .NET Provider will not participate in a TransactionScope transaction (verified without NHibernate involved). Code Snippet: public static void TestTScope() { Employee johnp = new Employee { name = "John Prideaux" }; using (TransactionScope tscope = new TransactionScope( TransactionScopeOption.Required, new TransactionOptions() { Timeout = new TimeSpan(0, 1, 0), IsolationLevel = IsolationLevel.ReadCommitted }, EnterpriseServicesInteropOption.Full)) { using (ISession session = OpenSession()) { session.Save(johnp); Console.WriteLine("Saved John to the database"); } } Console.WriteLine("Transaction should be rolled back"); } static ISession OpenSession() { if (factory == null) { Configuration c = new Configuration(); c.AddAssembly(Assembly.GetCallingAssembly()); factory = c.BuildSessionFactory(); } return factory.OpenSession(); } static ISessionFactory factory; Stack Trace: NHibernate.ADOException was unhandled Message="Could not close IBM.Data.Informix.IfxConnection connection" Source="NHibernate" StackTrace: at NHibernate.Connection.ConnectionProvider.CloseConnection(IDbConnection conn) at NHibernate.Connection.DriverConnectionProvider.CloseConnection(IDbConnection conn) at NHibernate.Tool.hbm2ddl.SuppliedConnectionProviderConnectionHelper.Release() at NHibernate.Tool.hbm2ddl.SchemaMetadataUpdater.GetReservedWords(Dialect dialect, IConnectionHelper connectionHelper) at NHibernate.Tool.hbm2ddl.SchemaMetadataUpdater.Update(ISessionFactory sessionFactory) at NHibernate.Impl.SessionFactoryImpl..ctor(Configuration cfg, IMapping mapping, Settings settings, EventListeners listeners) at NHibernate.Cfg.Configuration.BuildSessionFactory() at HelloNHibernate.Employee.OpenSession() in D:\Development\ScratchProject\HelloNHibernate\Employee.cs:line 73 at HelloNHibernate.Employee.TestTScope() in D:\Development\ScratchProject\HelloNHibernate\Employee.cs:line 53 at HelloNHibernate.Program.Main(String[] args) in D:\Development\ScratchProject\HelloNHibernate\Program.cs:line 19 at System.AppDomain._nExecuteAssembly(Assembly assembly, String[] args) at System.AppDomain.ExecuteAssembly(String assemblyFile, Evidence assemblySecurity, String[] args) at Microsoft.VisualStudio.HostingProcess.HostProc.RunUsersAssembly() at System.Threading.ThreadHelper.ThreadStart_Context(Object state) at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state) at System.Threading.ThreadHelper.ThreadStart() InnerException: IBM.Data.Informix.IfxException Message="ERROR - no error information available" Source="IBM.Data.Informix" ErrorCode=-2147467259 StackTrace: at IBM.Data.Informix.IfxConnection.HandleError(IntPtr hHandle, SQL_HANDLE hType, RETCODE retcode) at IBM.Data.Informix.IfxConnection.DisposeClose() at IBM.Data.Informix.IfxConnection.Close() at NHibernate.Connection.ConnectionProvider.CloseConnection(IDbConnection conn) InnerException:

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• Efficient Context-Free Grammar parser, preferably Python-friendly

  - by Max Shawabkeh

  I am in need of parsing a small subset of English for one of my project, described as a context-free grammar with (1-level) feature structures (example) and I need to do it efficiently . Right now I'm using NLTK's parser which produces the right output but is very slow. For my grammar of ~450 fairly ambiguous non-lexicon rules and half a million lexical entries, parsing simple sentences can take anywhere from 2 to 30 seconds, depending it seems on the number of resulting trees. Lexical entries have little to no effect on performance. Another problem is that loading the (25MB) grammar+lexicon at the beginning can take up to a minute. From what I can find in literature, the running time of the algorithm used to parse such a grammar (Earley or CKY) should be linear to the size of the grammar and cubic to the size of the input token list. My experience with NLTK indicates that ambiguity is what hurts the performance most, not the absolute size of the grammar. So now I'm looking for a CFG parser to replace NLTK. I've been considering PLY but I can't tell whether it supports feature structures in CFGs, which are required in my case, and the examples I've seen seem to be doing a lot of procedural parsing rather than just specifying a grammar. Can anybody show me an example of PLY both supporting feature structs and using a declarative grammar? I'm also fine with any other parser that can do what I need efficiently. A Python interface is preferable but not absolutely necessary.

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• Get JVM to grow memory demand as needed up to size of VM limit?

  - by Ira Baxter

  We ship a Java application whose memory demand can vary quite a lot depending on the size of the data it is processing. If you don't set the max VM (virtual memory) size, quite often the JVM quits with an GC failure on big data. What we'd like to see, is the JVM requesting more memory, as GC fails to provide enough, until the total available VM is exhausted. e.g., start with 128Mb, and increase geometrically (or some other step) whenever the GC failed. The JVM ("Java") command line allows explicit setting of max VM sizes (various -Xm* commands), and you'd think that would be designed to be adequate. We try to do this in a .cmd file that we ship with the application. But if you pick any specific number, you get one of two bad behaviors: 1) if your number is small enough to work on most target systems (e.g., 1Gb), it isn't big enough for big data, or 2) if you make it very large, the JVM refuses to run on those systems whose actual VM is smaller than specified. How does one set up Java to use the available VM when needed, without knowing that number in advance, and without grabbing it all on startup?

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• SoundManager2 has irregular latency

  - by Stefan Monov

  I'm playing some notes at regular intervals. Each one is delayed by a random number of milliseconds, creating a jarring irregular effect. How do I fix it? Note: I'm OK with some latency, just as long as it's consistent. Answers of the type "implement your own small SoundManager2 replacement, optimized for timing-sensitive playback" are OK, if you know how to do that :) but I'm trying to avoid rewriting my whole app in flash for now. For an example of app with zero audible latency see the flash-based ToneMatrix. Testcase (see it here live or get it in an zip): <head> <title></title> <script type="text/javascript" src="http://www.schillmania.com/projects/soundmanager2/script/soundmanager2.js"> </script> <script type="text/javascript"> soundManager.url = '.' soundManager.flashVersion = 9 soundManager.useHighPerformance = true soundManager.useFastPolling = true soundManager.autoLoad = true function recur(func, delay) { window.setTimeout(function() { recur(func, delay); func(); }, delay) } soundManager.onload = function() { var sound = soundManager.createSound("test", "test.mp3") recur(function() { sound.play() }, 300) } </script> </head> <body> </body> </html>

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• iPhone SDK 3.2 Universal App issue with .xib files

  - by Wesley

  Hello! So I am finding this process of universalizing my iPhone app to be a big headache! Am I alone in this? I sure hope not. Anyway, my question is regarding the .xib files for my universal application. I had my iPhone OS 3.1 running app all ready to make the universal switch. I went up to Project/Upgrade Current Target for iPad/Universal Application and it supposedly made my app have all the necessary iPad settings... So when I went to test it in 3.2 SDk, the screen was big, meaning the toolbar was sized correctly for the iPad, but the image that was being displayed was for the OS 3.1, meaning it was way small. So I then went to the iPad Source folder, changed the name of my MainViewController.xib file to MainViewController-iPad.xib, and inserted the bigger image I had prepared for the iPad, and it still didn't work correctly. Then, I went into my MainViewController.m file and changed the nib reference from MainViewController to MainViewController-iPad, and it worked! My only concern is that being that I had to "hard-code" it in, or force it to read from my -iPad file, is that going to present issues for the OS3.1 version? I can't go back and test the 3.1 version now for some reason, the option was removed from the Active SDK menu... If there is anyone out there that has experienced this, or has insight into what I am doing wrong, your help would be greatly appreciated. Thank you!

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• Authlogic, logout, credential capture and security

  - by Paddy

  Ok this is something weird. I got authlogic-oid installed in my rails app today. Everything works perfectly fine but for one small nuisance. This is what i did: I first register with my google openid. Successful login, redirection and my email, along with my correct openid is stored in my database. I am happy that everything worked fine! Now when i logout, my rails app as usual destroys the session and redirects me back to my root url where i can login again. Now if i try to login it still remembers my last login id. Not a big issue as i can always "Sign in as a different user" but i am wondering if there is anyway to not only logout from my app but also logout from google. I noticed the same with stack overflow's openid authentication system. Why am i so bothered about this, you may ask. But is it not a bad idea if your web apps end user, who happens to be in a cyber cafe, thinks he has logged out from your app and hence from his google account only to realize later that his google account had got hacked by some unworthy loser who just happened to notice that the one before him had not logged out from google and say.. changed his password!! Should i be paranoid? Isn't this a major security lapse while implementing the openid spec? Probably today someone can give me a workaround for this issue and the question is solved for me. But what about the others who have implemented openid in their apps and not implemented a workaround?

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• ASP.NET Projects with Two Versions of AjaxControlToolkit

  - by Chris

  In my Solution I have three projects. Project A is a web app and uses version 1.0.10618.0 of the AjaxControlToolkit. I would love to upgrade it to the latest but unfortunately any newer release completely breaks a portion of my site. Project B is also a web app but is a completely new software product and so it uses (and relies on) the latest version of the AjaxControlToolkit. Everything works great. Thought A and B are totally different products they use the same DB and rely on the same ClassLibrary. Project C is a small web app that ties A and B together with certain functionality like forgot password pages. The pages in this app reside in a virtual directory of both A and B. Project C currently uses v1.0.10618.0 of the toolkit so it works with Project A but it fails with project B because the manifest definitions of the dlls don't match (to be expected). What I've done is built a new dll of the toolkit and changed the assembly and namespace to AjaxControlToolkit_v1 and then changed all v1 references to this new dll so the old version and new versions can sit side by side in the same bin folder and nobody complains. I then changed my web.config controls tag to look like this: <add tagPrefix="ajaxToolkit" namespace="AjaxControlToolkit_v1" assembly="AjaxControlToolkit_v1, Version=1.0.10618.0, Culture=neutral, PublicKeyToken=28f01b0e84b6d53e"/> This all works except I get a runtime error of: Unknown server tag 'ajaxToolkit:AnimationExtender'. I can't figure out why this is, any ideas on how to remedy it?

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• Concurrent cartesian product algorithm in Clojure

  - by jqno

  Is there a good algorithm to calculate the cartesian product of three seqs concurrently in Clojure? I'm working on a small hobby project in Clojure, mainly as a means to learn the language, and its concurrency features. In my project, I need to calculate the cartesian product of three seqs (and do something with the results). I found the cartesian-product function in clojure.contrib.combinatorics, which works pretty well. However, the calculation of the cartesian product turns out to be the bottleneck of the program. Therefore, I'd like to perform the calculation concurrently. Now, for the map function, there's a convenient pmap alternative that magically makes the thing concurrent. Which is cool :). Unfortunately, such a thing doesn't exist for cartesian-product. I've looked at the source code, but I can't find an easy way to make it concurrent myself. Also, I've tried to implement an algorithm myself using map, but I guess my algorithmic skills aren't what they used to be. I managed to come up with something ugly for two seqs, but three was definitely a bridge too far. So, does anyone know of an algorithm that's already concurrent, or one that I can parallelize myself?

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• RelayCommand sender from ItemsControl item

  - by Padu Merloti

  I've been using MVVM's RelayCommand with success to bind actions to XAML, but I'm having a small problem with my ItemsControl. <ItemsControl ItemsSource="{Binding Devices}" > <ItemsControl.ItemTemplate> <DataTemplate> <Grid Width="100" Margin="4" > <Button Command="{Binding Path=SelectDeviceCommand}" > <Grid> <Image Source="img_small.png"></Image> <Image Source="{Binding Path=Logo}" /> </Grid> </Button> </Grid> </DataTemplate> </ItemsControl.ItemTemplate> </ItemsControl> In my view model: public RelayCommand SelectDeviceCommand { get; set; } private ObservableCollection<Device> Devices; Devices = CreateListOfDevices(); private void InitializeCommands() { SelectDeviceCommand = new RelayCommand((s) => MessageBox.Show(s.ToString())); } How do I define my SelectDeviceCommand in my view model in order to receive object that is bound to that item? My SelectDeviceCommand is not even being called... (but that I guess is because I need to make my Device a mini-viewmodel and implement the SelectDeviceCommand in it, is that correct?)

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• Prism - loading modules causes activation error

  - by Noich

  I've created a small Prism application (using MEF) with the following parts: - Infrastructure project, that contains a global file of region names. - Main project, that has 2 buttons to load other modules. - ModulesInterfaces project, where I've defined an IDataAccess interface for my DataAccess module. - DataAccess project, where there are several files but one main DataAccess class that implements both IDataAccess and IModule. When the user click a button, I want to show him a list of employees, so I need the DataAccess module. My code is as follows: var namesView = new EmployeesListView(); var namesViewModel = new EmployeesListViewModel(employeeRepository); namesView.DataContext = namesViewModel; namesViewModel.EmployeeSelected += EmployeeSelected; LocateManager(); manager.Regions["ContentRegion"].Add(new NoEmployeeView(), "noEmployee"); manager.Regions["NavigationRegion"].Add(namesView); I get an exception in my code when I'm trying to get DataAccess as a service (via ServiceLocator). I'm not sure if that's the right way to go, but trying to get it from the ModuleCatalog (as a type IDataAccess returns an empty enumeration). I'd appreciate some directions. Thanks. The problematic code line: object instance = ServiceLocator.Current.GetInstance(typeof(DataAccess.DataAccess)); The exact exception: Activation error occured while trying to get instance of type DataAccess, key "" The inner exception is null, the stack trace: at Microsoft.Practices.Prism.MefExtensions.MefServiceLocatorAdapter.DoGetInstance(Type serviceType, String key) in c:\release\WorkingDir\PrismLibraryBuild\PrismLibrary\Desktop\Prism.MefExtensions\MefServiceLocatorAdapter.cs:line 76 at Microsoft.Practices.ServiceLocation.ServiceLocatorImplBase.GetInstance(Type serviceType, String key) Edit The same exception is thrown for: container = (CompositionContainer)ServiceLocator.Current.GetInstance(typeof(CompositionContainer));

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• Worse is better. Is there an example?

  - by J.F. Sebastian

  Is there a widely-used algorithm that has time complexity worse than that of another known algorithm but it is a better choice in all practical situations (worse complexity but better otherwise)? An acceptable answer might be in a form: There are algorithms A and B that have O(N**2) and O(N) time complexity correspondingly, but B has such a big constant that it has no advantages over A for inputs less then a number of atoms in the Universe. Examples highlights from the answers: Simplex algorithm -- worst-case is exponential time -- vs. known polynomial-time algorithms for convex optimization problems. A naive median of medians algorithm -- worst-case O(N**2) vs. known O(N) algorithm. Backtracking regex engines -- worst-case exponential vs. O(N) Thompson NFA -based engines. All these examples exploit worst-case vs. average scenarios. Are there examples that do not rely on the difference between the worst case vs. average case scenario? Related: The Rise of ``Worse is Better''. (For the purpose of this question the "Worse is Better" phrase is used in a narrower (namely -- algorithmic time-complexity) sense than in the article) Python's Design Philosophy: The ABC group strived for perfection. For example, they used tree-based data structure algorithms that were proven to be optimal for asymptotically large collections (but were not so great for small collections). This example would be the answer if there were no computers capable of storing these large collections (in other words large is not large enough in this case). Coppersmith–Winograd algorithm for square matrix multiplication is a good example (it is the fastest (2008) but it is inferior to worse algorithms). Any others? From the wikipedia article: "It is not used in practice because it only provides an advantage for matrices so large that they cannot be processed by modern hardware (Robinson 2005)."

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• Why I am getting a Heap Corruption Error?

  - by vaidya.atul

  I am new to C++. I am getting HEAP CORRUPTION ERROR. Any help will be highly appreciated. Below is my code class CEntity { //some member variables CEntity(string section1,string section2); CEntity(); virtual ~CEntity(); //pure virtual function .. virtual CEntity* create()const =0; }; I derive CLine from CEntity as below class CLine:public CEntity { // Again some variables ... // Constructor and destructor CLine(string section1,string section2); CLine(); ~CLine(); CLine* Create() const; } // CLine Implementation CLine::CLine(string section1,string section2):CEntity(section1,section2){}; CLine::CLine(); CLine* CLine::create()const{return new CLine();} I have another class CReader which uses CLine object and populates it in a multimap as below class CReader { public: CReader(); ~CReader(); multimap<int,CEntity*>m_data_vs_entity; }; //CReader Implementation CReader::CReader() { m_data_vs_entity.clear(); }; CReader::~CReader() { multimap<int,CEntity*>::iterator iter; for(iter = m_data_vs_entity.begin();iter!=m_data_vs_entity.end();iter++) { CEntity* current_entity = iter->second; if(current_entity) delete current_entity; } m_data_vs_entity.clear(); } I am reading the data from a file and then populating the CLine Class.The map gets populated in a function of CReader class. Since CEntity has a virtual destructor, I hope the piece of code in CReader's destructor should work. In fact, it does work for small files but I get HEAP CORRUPTION ERROR while working with bigger files. If there is something fundamentally wrong, then, please help me find it, as I have been scratching my head for quit some time now. Thanks in advance and awaiting reply, Regards, Atul

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• Easiest way to use speex preprocessor in C#?

  - by eselk

  I need to use the speex preprocessor, and only the preprocessor in my VOIP app (don't need to use the codec). My app is written in C#. I think I know the easiest steps, but not sure where to find these items. Easiest in my opinion, if I can find these: Windows DLL that contains only the preprocessor functions, or if small enough in size I guess the entire speex library would be OK. So far I've only found binarys in EXE format, so if I can't find the binaries I'd have to install the compiler they use to build their source and probably several other libraries (as is my experience with most open source builds). C# versions of the header files, for pinvoking the DLL functions. So my question is, does anyone know where I can find these? I'm sure people have created these before, based on the huge number of speex users, just not able to find any on-line. Hope people don't think I'm lazy, I just hate doing this kind of "busy work" if I know many others have probably already done the exact same thing :) Update: I did find http://www.rarewares.org/files/others/libspeex-dll-1.2rc1.zip which includes libspeex.dll, but the DLL has no exports so not sure how they expect that to work. The other binaries they have are also just EXEs.

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• jQuery validator not working in unit testing

  - by Dbugger

  I have this small HTML file: <html> <head></head> <body> <form id='MyForm'> <input type='text' required /> <input type='submit' /> </form> <script src="/js/jquery-1.9.0.js"></script> <script src="/js/jquery.validate.js"></script> <script> var validator = $("#MyForm").validate(); alert(validator.form()); </script> </body> </html> This alerts me with "false", which is the expected behaviour. The problem comes when I go to unit testing, with js-test-driver: TestCase("MyTests", { setUp: function() { this.myform = "<form id='MyForm'><input type='text' required /><input type='submit' /></form>"; this.validator = $(this.myform).validate(); jstestdriver.console.log("Does the form validate? " + this.validator.form()); }, test_empty: function() { }, }); This code returns me the string Does the form validate? true This is a simplified version of my project of course, but the point is that I dont seem to be able to unit test the validation module im developing, since the jQuery validate plugin doesnt seem to work. What am I missing?

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• C# File IO with Streams - Best Memory Buffer Size

  - by AJ

  Hi, I am writing a small IO library to assist with a larger (hobby) project. A part of this library performs various functions on a file, which is read / written via the FileStream object. On each StreamReader.Read(...) pass, I fire off an event which will be used in the main app to display progress information. The processing that goes on in the loop is vaired, but is not too time consuming (it could just be a simple file copy, for example, or may involve encryption...). My main question is: What is the best memory buffer size to use? Thinking about physical disk layouts, I could pick 2k, which would cover a CD sector size and is a nice multiple of a 512 byte hard disk sector. Higher up the abstraction tree, you could go for a larger buffer which could read an entire FAT cluster at a time. I realise with today's PC's, I could go for a more memory hungry option (a couple of MiB, for example), but then I increase the time between UI updates and the user perceives a less responsive app. As an aside, I'm eventually hoping to provide a similar interface to files hosted on FTP / HTTP servers (over a local network / fastish DSL). What would be the best memory buffer size for those (again, a "best-case" tradeoff between perceived responsiveness vs. performance). Thanks in advance for any ideas, Adam

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• weak or strong for IBOutlet and other

  - by Piero

  I have switched my project to ARC, and I don't understand if I have to use strong or weak for IBOutlets. Xcode do this: in interface builder, if a create a UILabel for example and I connect it with assistant editor to my ViewController, it create this: @property (nonatomic, strong) UILabel *aLabel; It uses the strong, instead I read a tutorial on RayWenderlich website that say this: But for these two particular properties I have other plans. Instead of strong, we will declare them as weak. @property (nonatomic, weak) IBOutlet UITableView *tableView; @property (nonatomic, weak) IBOutlet UISearchBar *searchBar; Weak is the recommended relationship for all outlet properties. These view objects are already part of the view controller’s view hierarchy and don’t need to be retained elsewhere. The big advantage of declaring your outlets weak is that it saves you time writing the viewDidUnload method. Currently our viewDidUnload looks like this: - (void)viewDidUnload { [super viewDidUnload]; self.tableView = nil; self.searchBar = nil; soundEffect = nil; } You can now simplify it to the following: - (void)viewDidUnload { [super viewDidUnload]; soundEffect = nil; } So use weak, instead of the strong, and remove the set to nil in the videDidUnload, instead Xcode use the strong, and use the self... = nil in the viewDidUnload. My question is: when do I have to use strong, and when weak? I want also use for deployment target iOS 4, so when do I have to use the unsafe_unretain? Anyone can help to explain me well with a small tutorial, when use strong, weak and unsafe_unretain with ARC?

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