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  • What algorithm would you use to code a parrot?

    - by Phil H
    A parrot learns the most commonly uttered words and phrases in its vicinity so it can repeat them at inappropriate moments. So how would you create a software version? Assuming it has access to a microphone and can record sound at will, how would you code it without requiring infinite resources? The best I can imagine is to divide the stream using silences in the sound, and then use some pattern recognition to encode each one as a list of tokens, storing new ones as you meet them. Hashing the token sequences and counting occurrences in a database, you could build up a picture of the most frequently uttered phrases. But given the huge variety in phrases, how do you prevent this just becoming a huge list? And the sheer number of pairs to match would surely generate lot of false positives from the combinatorial nature of matching. Would you use a neural net, since that's how a real parrot manages it? Or is there another, cleverer way of matching large-scale patterns in analogue data?

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  • CheckBox Command Behaviors for Silverlight MVVM Pattern

    - by Blake Blackwell
    I am trying to detect when an item is checked, and which item is checked in a ListBox using Silverlight 4 and the Prism framework. I found this example on creating behaviors, and tried to follow it but nothing is happening in the debugger. I have three questions: Why isn't my command executing? How do I determine which item was checked (i.e. pass a command parameter)? How do I debug this? (i.e. where can I put break points to begin stepping into this) Here is my code: View: <ListBox x:Name="MyListBox" ItemsSource="{Binding PanelItems, Mode=TwoWay}"> <ListBox.ItemTemplate> <DataTemplate> <StackPanel Orientation="Horizontal"> <CheckBox IsChecked="{Binding Enabled}" my:Checked.Command="{Binding Check}" /> <TextBlock x:Name="DisplayName" Text="{Binding DisplayName}"/> </StackPanel> </DataTemplate> </ListBox.ItemTemplate> </ListBox> ViewModel: public MainPageViewModel() { _panelItems.Add( new PanelItem { Enabled = true, DisplayName = "Test1" } ); Check = new DelegateCommand<object>( itemChecked ); } public void itemChecked( object o ) { //do some stuff } public DelegateCommand<object> Check { get; set; } Behavior Class public class CheckedBehavior : CommandBehaviorBase<CheckBox> { public CheckedBehavior( CheckBox element ) : base( element ) { element.Checked +=new RoutedEventHandler(element_Checked); } void element_Checked( object sender, RoutedEventArgs e ) { base.ExecuteCommand(); } } Command Class public static class Checked { public static ICommand GetCommand( DependencyObject obj ) { return (ICommand) obj.GetValue( CommandProperty ); } public static void SetCommand( DependencyObject obj, ICommand value ) { obj.SetValue( CommandProperty, value ); } public static readonly DependencyProperty CommandProperty = DependencyProperty.RegisterAttached( "Command", typeof( CheckBox ), typeof( Checked ), new PropertyMetadata( OnSetCommandCallback ) ); public static readonly DependencyProperty CheckedCommandBehaviorProperty = DependencyProperty.RegisterAttached( "CheckedCommandBehavior", typeof( CheckedBehavior ), typeof( Checked ), null ); private static void OnSetCommandCallback( DependencyObject dependencyObject, DependencyPropertyChangedEventArgs e ) { CheckBox element = dependencyObject as CheckBox; if( element != null ) { CheckedBehavior behavior = GetOrCreateBehavior( element ); behavior.Command = e.NewValue as ICommand; } } private static CheckedBehavior GetOrCreateBehavior( CheckBox element ) { CheckedBehavior behavior = element.GetValue( CheckedCommandBehaviorProperty ) as CheckedBehavior; if( behavior == null ) { behavior = new CheckedBehavior( element ); element.SetValue( CheckedCommandBehaviorProperty, behavior ); } return behavior; } public static CheckedBehavior GetCheckCommandBehavior( DependencyObject obj ) { return (CheckedBehavior) obj.GetValue( CheckedCommandBehaviorProperty ); } public static void SetCheckCommandBehavior( DependencyObject obj, CheckedBehavior value ) { obj.SetValue( CheckedCommandBehaviorProperty, value ); } } I used this article to get me started, but I'll readily admit this is over my head.

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  • Box2d: Set active and inactive

    - by Rosarch
    I'm writing an XNA game in C# using the XNA port of Box2d - Box2dx. Entities like trees or zombies are represented as GameObjects. GameObjectManager adds and removes them from the game world: /// <summary> /// Does the work of removing the GameObject. /// </summary> /// <param name="controller">The GameObject to be removed.</param> private void removeGameObjectFromWorld(GameObjectController controller) { controllers.Remove(controller); worldState.Models.Remove(controller.Model); controller.Model.Body.SetActive(false); } public void addGameObjectToWorld(GameObjectController controller) { controllers.Add(controller); worldState.Models.Add(controller.Model); controller.Model.Body.SetActive(true); } controllers is a collection of GameObjectController instances. worldState.Models is a collection of GameObjectModel instances. When I remove GameObjects from Box2d this way, this method gets called: void IContactListener.EndContact(Contact contact) { GameObjectController collider1 = worldQueryUtils.gameObjectOfBody(contact.GetFixtureA().GetBody()); GameObjectController collider2 = worldQueryUtils.gameObjectOfBody(contact.GetFixtureB().GetBody()); collisionRecorder.removeCollision(collider1, collider2); } worldQueryUtils: // this could be cached if we know bodies never change public GameObjectController gameObjectOfBody(Body body) { return worldQueryEngine.GameObjectsForPredicate(x => x.Model.Body == body).Single(); } This method throws an error: System.InvalidOperationException was unhandled Message="Sequence contains no elements" Source="System.Core" StackTrace: at System.Linq.Enumerable.Single[TSource](IEnumerable`1 source) at etc Why is this happening? What can I do to avoid it? This method has been called many times before the body.SetActive() was called. I feel that this may be messing it up.

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  • MVVM pattern and nested view models - communication and lookup lists

    - by LostInWPF
    I am using Prism for a new application that I am creating. There are several lookup lists that will be used in several places in the application. Therefore it makes sense to define it once and use that everywhere I need that functionality. My current solution is to use typed data templates to render the controls inside a content control. <DataTemplate DataType={x:Type ListOfCountriesViewModel}> <ComboBox ItemsSource={Binding Countries} SelectedItem="{Binding SelectedCountry"/> </DataTemplate> <DataTemplate DataType={x:Type ListOfRegionsViewModel}> <ComboBox ItemsSource={Binding Countries} SelectedItem={Binding SelectedRegion} /> </DataTemplate> public class ParentViewModel { SelectedCountry get; set; SelectedRegion get; set; ListOfCountriesViewModel CountriesVM; ListOfRegionsViewModel RgnsVM; } Then in my window I have 2 content controls and the rest of the controls <ContentControl Content="{Binding CountriesVM}"></ContentControl> <ContentControl Content="{Binding RgnsVM}"></ContentControl> <Rest of controls on view> At the moment I have this working and the SelectedItems for the combo boxes are publising events via EventAggregator from the child view models which are then subscribed to in the parent view model. I am not sure that this is the best way to go as I can imagine I would end up with a lot of events very quickly and it will become unwieldy. Also if I was to use the same view model on another window it will publish the event and this parent viewmodel is subscribed to it which could have unintended consequences. My questions are :- Is this the best way to put lookup lists in a view which can be re-used across screens? How do I make it so that the combobox which is bound to the child viewmodel sets the relevant property on the parent viewmodel without using events / mediator. e.g in this case SelectedCountry for example? Any alternative implementation proposals for what I am trying to do? I have a feeling I am missing something obvious and there is so much info it is hard to know what is right so any help would be most gratefully received.

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  • Question on MVVM pattern on WPF ?

    - by Ashish Ashu
    I have a user control let say UC1 . This user control have viewmodel UC1_vm. In the usercontrol UC1 I have a canvas in which drawing curve logic is implemented. This drawing curve logic is based on the data points property in the view model ( UC1_vm). The data points property inside the view model change with different condition. The generation of data points is written in the View Model. I want to bind the data points property in the view model to the draw curve logic inside the User control (view). I want whenever the data point property is changed in the view model , the canvas calls the draw curve method. Can I set the set any property of canvas which when changed it calls the on paint logic auto matically? Please suggest me the approach of implementing this scenario!!

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  • Query on MVVM design pattern on WPF.

    - by Ashish Ashu
    I am using MVVM architecture. I have a usercontrol UC as a View Model is a ModelData class ViewModel (UCViewModel) is binded to a usercontrol. I have three more usercontrols that is inside the usercontrol UC ( discussed above). Let's say uc1, uc2 and uc3. and the visibility of uc1 , uc2 and uc3 inside UC depends on the type selected ( which ever radio button is selected ). Since UC is binded to UCViewModel and I have to do all the stuff related to uc1 , uc2 and uc3 inside UCViewModel. Can I have seperate VM to uc1 , uc2 and uc3.. if Yes how can i do that ? Please Help!!

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  • Page navigation in silverlight 4 using MVVM pattern

    - by Archie
    Hello, I have a a navigation application developed in Silverlight 4. It has a main page which contains a frame. I load a particualr view in that frame and I know that I can use NavigationService to navigate to other page which would be loaded in the same frame. But my question is how it can be done using MVVM? To get the frame do I need to pass the reference of the page? Also, as per my knowledge one view is not aware of any other views. So what is the best way to make them aware of each other? I have heard of Controller and Mediator but how shall I implement them so as to get the Frame of the mainpage? It would be very helpful if anyone can give me the example or probably sample code for this. Thanks in advance.

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  • java Filter URL pattern specific to request params

    - by Rohit Desai
    Hi All, We have a situation where we want to use filter for URL's containing some specific request parameters. e.g htt://mydomain.com/?id=78&formtype=simple_form&....... htt://mydomain.com/?id=788&formtype=special_form&....... and so on , id are fetched at run time, I want configure filter in web.xml only if formtype=special_form. How should achieve the solution . Can filter be configure with regex patterns? Really appreciate your help on this. Thanks, Rohit

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  • TypeInitializeException on MVVM pattern

    - by Mohit Deshpande
    System.TypeInitializationException was unhandled Message=The type initializer for 'SmartHomeworkOrganizer.ViewModels.MainViewModel' threw an exception. Source=SmartHomeworkOrganizer TypeName=SmartHomeworkOrganizer.ViewModels.MainViewModel StackTrace: at SmartHomeworkOrganizer.ViewModels.MainViewModel..ctor() at SmartHomeworkOrganizer.App.OnStartup(Object sender, StartupEventArgs e) in C:\Users\Mohit\Documents\Visual Studio 2010\Projects\SmartHomeworkOrganizer\SmartHomeworkOrganizer\App.xaml.cs:line 21 at System.Windows.Application.OnStartup(StartupEventArgs e) at System.Windows.Application.<.ctor>b__0(Object unused) at System.Windows.Threading.ExceptionWrapper.InternalRealCall(Delegate callback, Object args, Boolean isSingleParameter) at System.Windows.Threading.ExceptionWrapper.TryCatchWhen(Object source, Delegate callback, Object args, Boolean isSingleParameter, Delegate catchHandler) at System.Windows.Threading.Dispatcher.WrappedInvoke(Delegate callback, Object args, Boolean isSingleParameter, Delegate catchHandler) at System.Windows.Threading.DispatcherOperation.InvokeImpl() at System.Windows.Threading.DispatcherOperation.InvokeInSecurityContext(Object state) at System.Threading.ExecutionContext.runTryCode(Object userData) at System.Runtime.CompilerServices.RuntimeHelpers.ExecuteCodeWithGuaranteedCleanup(TryCode code, CleanupCode backoutCode, Object userData) at System.Threading.ExecutionContext.RunInternal(ExecutionContext executionContext, ContextCallback callback, Object state) at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state) at System.Windows.Threading.DispatcherOperation.Invoke() at System.Windows.Threading.Dispatcher.ProcessQueue() at System.Windows.Threading.Dispatcher.WndProcHook(IntPtr hwnd, Int32 msg, IntPtr wParam, IntPtr lParam, Boolean& handled) at MS.Win32.HwndWrapper.WndProc(IntPtr hwnd, Int32 msg, IntPtr wParam, IntPtr lParam, Boolean& handled) at MS.Win32.HwndSubclass.DispatcherCallbackOperation(Object o) at System.Windows.Threading.ExceptionWrapper.InternalRealCall(Delegate callback, Object args, Boolean isSingleParameter) at System.Windows.Threading.ExceptionWrapper.TryCatchWhen(Object source, Delegate callback, Object args, Boolean isSingleParameter, Delegate catchHandler) at System.Windows.Threading.Dispatcher.WrappedInvoke(Delegate callback, Object args, Boolean isSingleParameter, Delegate catchHandler) at System.Windows.Threading.Dispatcher.InvokeImpl(DispatcherPriority priority, TimeSpan timeout, Delegate method, Object args, Boolean isSingleParameter) at System.Windows.Threading.Dispatcher.Invoke(DispatcherPriority priority, Delegate method, Object arg) at MS.Win32.HwndSubclass.SubclassWndProc(IntPtr hwnd, Int32 msg, IntPtr wParam, IntPtr lParam) at MS.Win32.UnsafeNativeMethods.DispatchMessage(MSG& msg) at System.Windows.Threading.Dispatcher.PushFrameImpl(DispatcherFrame frame) at System.Windows.Threading.Dispatcher.PushFrame(DispatcherFrame frame) at System.Windows.Threading.Dispatcher.Run() at System.Windows.Application.RunDispatcher(Object ignore) at System.Windows.Application.RunInternal(Window window) at System.Windows.Application.Run(Window window) at System.Windows.Application.Run() at SmartHomeworkOrganizer.App.Main() in C:\Users\Mohit\Documents\Visual Studio 2010\Projects\SmartHomeworkOrganizer\SmartHomeworkOrganizer\obj\Debug\App.g.cs:line 0 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: System.ArgumentException Message=Default value type does not match type of property 'Score'. Source=WindowsBase StackTrace: at System.Windows.DependencyProperty.ValidateDefaultValueCommon(Object defaultValue, Type propertyType, String propertyName, ValidateValueCallback validateValueCallback, Boolean checkThreadAffinity) at System.Windows.DependencyProperty.ValidateMetadataDefaultValue(PropertyMetadata defaultMetadata, Type propertyType, String propertyName, ValidateValueCallback validateValueCallback) at System.Windows.DependencyProperty.RegisterCommon(String name, Type propertyType, Type ownerType, PropertyMetadata defaultMetadata, ValidateValueCallback validateValueCallback) at System.Windows.DependencyProperty.Register(String name, Type propertyType, Type ownerType, PropertyMetadata typeMetadata, ValidateValueCallback validateValueCallback) at System.Windows.DependencyProperty.Register(String name, Type propertyType, Type ownerType, PropertyMetadata typeMetadata) at SmartHomeworkOrganizer.ViewModels.MainViewModel..cctor() in C:\Users\Mohit\Documents\Visual Studio 2010\Projects\SmartHomeworkOrganizer\SmartHomeworkOrganizer\ViewModels\MainViewModel.cs:line 72 InnerException: This bit of code throws a System.ArgumentException before the TypeInitializeException. It says: "Default value type does not match type of property Score": public static readonly DependencyProperty ScoreProperty = DependencyProperty.Register("Score", typeof(float), typeof(MainViewModel), new UIPropertyMetadata(0.0)); Here is the .NET property: public float Score { get { return (float) GetValue(ScoreProperty); } set { SetValue(ScoreProperty, value); } }

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  • Repository pattern with lazying loading using POCO

    - by Simon G
    Hi, I'm in the process of starting a new project and creating the business objects and data access etc. I'm just using plain old clr objects rather than any orms. I've created two class libraries: 1) Business Objects - holds all my business objects, all this objects are light weight with only properties and business rules. 2) Repository - this is for all my data access. The majority of my objects will have child list in and my question is what is the best way to lazy load these values as I don't want to bring back unnecessary information if I dont need to. I've thought about when using the "get" on the child property to check if its "null" and if it is call my repository to get the child information. This has two problems from what I can see: 1) The object "knows" how to get itself I would rather no data access logic be held in the object. 2) This required both classes to reference each other which in visual studio throws a circular dependency error. Does anyone have any suggestions on how to overcome this issue or any recommendations on my projects layout and where it can be improved? Thanks

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  • TIBCO Designer - Active Database Error

    - by George
    Folks, I am with the following error when trying to start an instance of the Publish ActiveDatabase. I'm using Designer 5.7.2 and trying to access a database of SqlServer 2008. Someone saw this error before? I don´t find any reference in Google or other sites! Adaptador_M2M.Adaptador_M2M Error [Adapter] AEADB-910005 Startup Error. SDK Exception Code = AESDKC-0087, Category = Metadata, Severity = errorRole, Description = Class description not available for: ADB_PREREGLISTENER, File = C:/suren/workspace/Maverick/maverick-5.6.1-dev/libmaverick/MInstanceImpl.cpp, line = 71 received on starting the adapter after initialization. The Repository URL is D:\TEMP\AT_adadb_61214.dat and the Configuration URL is Corporativo/IntegracaoM2M/Adaptadores/Adaptador_M2M.

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  • Extract known pattern substring from NSString (without regex)

    - by d11wtq
    I'm really tempted to drop RegexKit (or my own libpcre wrapper) into my project in order to do this, but before I do that I want to know how Cocoa developers manage to do half of this basic stuff without really convoluted code or without linking with RegexKit or another regular expression library. I find it gobsmacking that Cocoa does not include any regular expression matching features. I've so accustomed to using regular expressions for all kinds of things that I'm lost without them. I can do what I need without them, but the code would be rather convoluted. So, Cocoa devs, I ask you, what's the "Cocoa way" to do this... The problem is an everyday problem in programming as far as I'm concerned. Cocoa must have ways of doing this with the built-in features. Note that the position of the elements I want to match changes, and sometimes "quotes" are present. Whitespace is variable. Take the following strings: Content-Type: application/xml; charset=utf-8 Content-Type: text/html; charset="iso-8859-1" Content-Type: text/plain; charset=us-ascii Content-Type: text/plain; name="example.txt"; charset=utf-8 From all of these strings, how would you go about determining the mime type (e.g. text/plain) and the charset (e.g. utf-8) using just the built-in Cocoa classes? I'd end up performing a series of -rangeOfString: and substring calls, with conditional checks to deal with the optional quotes etc. Is there a way to do this with NSScanner? The NSScanner class seems to have a pretty naive API to me. Something like C's sscanf() that works for NSString objects would be an ideal fit. Most of my string parsing needs are simple such as this example so maybe regular expressions, while I'm accustomed to them, are overkill?

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  • Active Record Validations : uniqueness of

    - by Elliot
    Hey guys, I'm using http://ar.rubyonrails.org/classes/ActiveRecord/Validations/ClassMethods.html#M000086 to validate records. My form is currently a remote form, using RJS. My question, is how to I return the :message (for errors) to the page through ajax (and I assume the create.rjs file)? Best, Elliot

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  • Active Merchant Paypal Recurring Pem Error Neither Pub Nor Priv Key

    - by Andy
    Hi, I am trying to use ActiveMerchant to make a Paypal Recurring transaction call. I used the patch here: http://blog.vuzit.com/2008/08/01/paypal-website-payments-pro-us-with-recurring-billing-and-activemerchant/ and I'm stuck on this here: ActiveMerchant::Billing::PaypalGateway.pem_file = File.read('paypal_cert.pem') I am fairly sure the pem file is correctly downloaded from paypal. The error I receive is: /Library/Ruby/Gems/1.8/gems/activemerchant-1.5.1/lib/active_merchant/lib/connection.rb:129:in initialize': Neither PUB key nor PRIV key:: nested asn1 error (OpenSSL::PKey::RSAError) from /Library/Ruby/Gems/1.8/gems/activemerchant-1.5.1/lib/active_merchant/lib/connection.rb:129:innew' from calling the commit method from line 49 of paypal_pro_recurring. I simply have 2 files - paypal_pro_recurring.rb from the tutorial and paypalTest.rb which I wrote and simply requires all files and calls the function. I hope the error isn't something stupid like I must require from an environment file or something. Thanks all!

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  • Strategy pattern and "action" classes explosion

    - by devoured elysium
    Is it bad policy to have lots of "work" classes(such as Strategy classes), that only do one thing? Let's assume I want to make a Monster class. Instead of just defining everything I want about the monster in one class, I will try to identify what are its main features, so I can define them in interfaces. That will allow to: Seal the class if I want. Later, other users can just create a new class and still have polymorphism by means of the interfaces I've defined. I don't have to worry how people (or myself) might want to change/add features to the base class in the future. All classes inherit from Object and they implement inheritance through interfaces, not from mother classes. Reuse the strategies I'm using with this monster for other members of my game world. Con: This model is rigid. Sometimes we would like to define something that is not easily achieved by just trying to put together this "building blocks". public class AlienMonster : IWalk, IRun, ISwim, IGrowl { IWalkStrategy _walkStrategy; IRunStrategy _runStrategy; ISwimStrategy _swimStrategy; IGrowlStrategy _growlStrategy; public Monster() { _walkStrategy = new FourFootWalkStrategy(); ...etc } public void Walk() { _walkStrategy.Walk(); } ...etc } My idea would be next to make a series of different Strategies that could be used by different monsters. On the other side, some of them could also be used for totally different purposes (i.e., I could have a tank that also "swims"). The only problem I see with this approach is that it could lead to a explosion of pure "method" classes, i.e., Strategy classes that have as only purpose make this or that other action. In the other hand, this kind of "modularity" would allow for high reuse of stratagies, sometimes even in totally different contexts. What is your opinion on this matter? Is this a valid reasoning? Is this over-engineering? Also, assuming we'd make the proper adjustments to the example I gave above, would it be better to define IWalk as: interface IWalk { void Walk(); } or interface IWalk { IWalkStrategy WalkStrategy { get; set; } //or something that ressembles this } being that doing this I wouldn't need to define the methods on Monster itself, I'd just have public getters for IWalkStrategy (this seems to go against the idea that you should encapsulate everything as much as you can!) Why? Thanks

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  • Codeigniter active record select, left join, count

    - by sea_1987
    Hi There, I have a form that shows results from a database query, these results can have many other assets ajoined to them and I wanting to find a way of showing how many assets each elemement has. For example my table is of areas of england an other table has where the users live I current have this code, $this->db->select('*'); $this->db->from('places'); $this->db->join('users, places.place_id = user.place_id, left'); $this->db->get(); The issue I am having is getting the query to return the place name and the number of users living in that place, it is possible?

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  • Regex pattern failing

    - by Scott Chamberlain
    I am trying to strip out all things that are in a string that are not a letter number or space so I created the regex private static Regex _NonAlphaChars = new Regex("[^[A-Za-z0-9 ]]", RegexOptions.Compiled); however When I call _NonAlphaChars.Replace("Scott,", ""); it returns "Scott," What am I doing wrong that it is not matching the ,?

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  • how does data clustering help in image or pattern recognition

    - by anon
    I have been playing around with different data clustering algorithms working on finding clusters between random data points represented an nodes, I keep reading that data clustering is used for image recognition. I am failing to make the connection, how does clustering data help in recognizing an image or in facial recognition. can someone explain this?

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  • Regex one-to-one mapping pattern replace

    - by polygenelubricants
    How would you use regex to write a function that replaces all lowercase letters with uppercase and vice versa? Note: this is NOT a homework question. See also my previous explorations of regex: Regex split into overlapping strings (Alan Moore's answer is especially instructive) Can you use zero-width matching regex in String split? (my solution exploits a known Java regex bug with regards to non-obvious length lookbehind!)

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  • MVC and repository pattern data effeciency

    - by Shawn Mclean
    My project is structured as follows: DAL public IQueryable<Post> GetPosts() { var posts = from p in context.Post select p; return posts; } Service public IList<Post> GetPosts() { var posts = repository.GetPosts().ToList(); return posts; } //Returns a list of the latest feeds, restricted by the count. public IList<PostFeed> GetPostFeeds(int latestCount) { List<Post> post - GetPosts(); //CODE TO CREATE FEEDS HERE return feeds; } Lets say the GetPostFeeds(5) is supposed to return the 5 latest feeds. By going up the list, doesn't it pull down every single post from the database from GetPosts(), just to extract 5 from it? If each post is say 5kb from the database, and there is 1 million records. Wont that be 5GB of ram being used per call to GetPostFeeds()? Is this the way it happens? Should I go back to my DAL and write queries that return only what I need?

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  • MVC and repository pattern data efficiency

    - by Shawn Mclean
    My project is structured as follows: DAL public IQueryable<Post> GetPosts() { var posts = from p in context.Post select p; return posts; } Service public IList<Post> GetPosts() { var posts = repository.GetPosts().ToList(); return posts; } //Returns a list of the latest feeds, restricted by the count. public IList<PostFeed> GetPostFeeds(int latestCount) { List<Post> post - GetPosts(); //CODE TO CREATE FEEDS HERE return feeds; } Lets say the GetPostFeeds(5) is supposed to return the 5 latest feeds. By going up the list, doesn't it pull down every single post from the database from GetPosts(), just to extract 5 from it? If each post is say 5kb from the database, and there is 1 million records. Wont that be 5GB of ram being used per call to GetPostFeeds()? Is this the way it happens? Should I go back to my DAL and write queries that return only what I need?

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  • JBoss Seam: In ScopeType.PAGE I get: java.lang.IllegalStateException: No conversation context active

    - by Markos Fragkakis
    Hi all, I have a page-scoped component, which has an instance variable List with data, which I display in a datatable. This datatable has pagination, sorting and filtering. The first time gate into the page, I get this appended in my URL: ?conversationId=97. The page works correctly, and when I change datatable pages no now component is created. After a minute or two, and at seamingly random time, I get an exception saying that there is no context. I have not used @Create in my code or my navigation files. So, I have two questions: Why do I get this suffix in my URL? Why did a conversation start? Why the exception? The component is scoped to PAGE. If I received an exception, it should not be related to a conversation. Right? Or is the conversation the exception is referring a temporary conversation? Cheers! UPDATE: This is the page: <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml" xmlns:ui="http://java.sun.com/jsf/facelets" xmlns:h="http://java.sun.com/jsf/html" xmlns:f="http://java.sun.com/jsf/core" xmlns:a4j="http://richfaces.org/a4j" xmlns:rich="http://richfaces.org/rich"> <body> <ui:composition template="/WEB-INF/facelets/templates/template.xhtml"> <ui:define name="content"> <!-- This method returns focus on the filter --> <script type="text/javascript"> function submitByEnter(event){ if (event.keyCode == 13) { if (event.preventDefault) { // Firefox event.preventDefault(); } else { // IE event.returnValue = false; } document.getElementById("refreshButton").click(); } } </script> <h:form prependId="false"> <h:commandButton action="Back" value="Back to home page" /> <br /> <p><h:outputText value="Applicants and Products (experimentation page)" class="page_title" /></p> <h:commandButton action="#{applicantProductListBean.showCreateApplicant}" value="Create Applicant" id="createApplicantButton"> </h:commandButton> <a4j:commandButton value="Refresh" id="refreshButton" action="#{applicantProductListBean.refreshData}" image="/images/icons/refresh48x48.gif" reRender="compositeTable, compositeScroller"> <!-- <f:setPropertyActionListener--> <!-- target="# {pageScrollerBean.applicantProductListPage}" value="1" />--> </a4j:commandButton> <rich:toolTip for="createApplicantButton" value="Create Applicant" /> <rich:dataTable styleClass="composite2DataTable" id="compositeTable" rows="1" columnClasses="col" value="#{applicantProductListBean.dataModel}" var="pageAppList"> <f:facet name="header"> <rich:columnGroup> <rich:column colspan="3"> <h:outputText styleClass="headerText" value="Applicants" /> </rich:column> <rich:column colspan="3"> <h:outputText styleClass="headerText" value="Products" /> </rich:column> <rich:column breakBefore="true"> <h:outputText styleClass="headerText" value="Applicant Name" /> <a4j:commandButton id="sortingApplicantNameButton" action="#{applicantProductListBean.toggleSorting('applicantName')}" image="/images/icons/sorting/#{sortingFilteringBean.applicantProductListSorting.sortingValues['applicantName']}.gif" reRender="sortingApplicantNameButton, sortingApplicantEmailButton, compositeTable, compositeScroller"> <!-- <f:setPropertyActionListener--> <!-- target="#{pageScrollerBean.applicantProductListPage}" value="1" />--> </a4j:commandButton> <br /> <h:inputText value="#{sortingFilteringBean.applicantProductListFiltering.filteringValues['applicantName']}" id="applicantNameFilterValue" onkeypress="return submitByEnter(event)"> </h:inputText> </rich:column> <rich:column> <h:outputText styleClass="headerText" value="Applicant Email" /> <a4j:commandButton id="sortingApplicantEmailButton" action="#{applicantProductListBean.toggleSorting('applicantEmail')}" image="/images/icons/sorting/#{sortingFilteringBean.applicantProductListSorting.sortingValues['applicantEmail']}.gif" reRender="sortingApplicantNameButton, sortingApplicantEmailButton, compositeTable, compositeScroller"> <!-- <f:setPropertyActionListener--> <!-- target="#{pageScrollerBean.applicantProductListPage}" value="1" />--> </a4j:commandButton> <br /> <h:inputText value="#{sortingFilteringBean.applicantProductListFiltering.filteringValues['applicantEmail']}" id="applicantEmailFilterValue" onkeypress="return submitByEnter(event)"> </h:inputText> </rich:column> <rich:column> <h:outputText styleClass="headerText" value="Applicant Actions" /> </rich:column> <rich:column> <h:outputText styleClass="headerText" value="Product Name" /> <a4j:commandButton id="sortingProductNameButton" action="#{applicantProductListBean.toggleSorting('productName')}" immediate="true" image="/images/icons/sorting/#{sortingFilteringBean.applicantProductListSorting.sortingValues['productName']}.gif" reRender="sortingProductNameButton, compositeTable, compositeScroller"> </a4j:commandButton> <br /> <h:inputText value="#{sortingFilteringBean.applicantProductListFiltering.filteringValues['productName']}" id="productNameFilterValue" onkeypress="return submitByEnter(event)"> </h:inputText> </rich:column> <rich:column> <h:outputText styleClass="headerText" value="Product Email" /> <br /> <h:inputText value="#{sortingFilteringBean.applicantProductListFiltering.filteringValues['productEmail']}" id="productEmailFilterValue" onkeypress="return submitByEnter(event)"> </h:inputText> </rich:column> <rich:column> <h:outputText styleClass="headerText" value="Product Actions" /> </rich:column> </rich:columnGroup> </f:facet> <rich:subTable rowClasses="odd_applicant_row, even_applicant_row" value="#{pageAppList}" var="app"> <rich:column styleClass=" internal_cell composite2TextContainingColumn" valign="top"> <h:outputText value="#{app.name}" /> </rich:column> <rich:column styleClass="internal_cell composite2TextContainingColumn" valign="top"> <h:outputText value="#{app.receiptEmail}" /> </rich:column> <rich:column valign="top" styleClass="buttonsColumn"> <h:commandButton action="#{applicantProductListBean.showUpdateApplicant(app)}" image="/images/icons/edit.jpg"> </h:commandButton> <!-- <rich:toolTip for="editApplicantButton" value="Edit Applicant" />--> <h:commandButton action="#{applicantProductListBean.showDeleteApplicant(app)}" image="/images/icons/delete.png"> </h:commandButton> <!-- <rich:toolTip for="deleteApplicantButton" value="Delete Applicant" />--> </rich:column> <rich:column colspan="3"> <table class="productsTableTable"> <tbody> <tr> <td class="createProductButtonTableCell"><h:commandButton action="#{applicantProductListBean.showCreateProduct(app)}" value="Create Product"> </h:commandButton> <!-- <rich:toolTip for="createProductButton" value="Create Product" />--> </td> </tr> <tr> <td><rich:dataTable value="#{app.products}" var="prod" rowClasses="odd_product_row, even_product_row"> <rich:column styleClass="internal_cell composite2TextContainingColumn"> <h:outputText value="#{prod.inventedName}" /> </rich:column> <rich:column styleClass="internal_cell composite2TextContainingColumn"> <h:outputText value="#{prod.receiptEmail}" /> </rich:column> <rich:column styleClass="buttonsColumn"> <h:commandButton action="#{applicantProductListBean.showUpdateProduct(prod)}" image="/images/icons/edit.jpg"> </h:commandButton> <!-- <rich:toolTip for="editProductButton" value="Edit Product" />--> <h:commandButton action="#{applicantProductListBean.showDeleteProduct(prod)}" image="/images/icons/delete.png"> <f:setPropertyActionListener target="#{productBean.product}" value="#{prod}" /> </h:commandButton> <!-- <rich:toolTip for="deleteProductButton" value="Delete Product" />--> </rich:column> </rich:dataTable></td> </tr> </tbody> </table> </rich:column> </rich:subTable> <f:facet name="footer"> <h:panelGrid columns="1" styleClass="applicantProductListFooter"> <h:outputText value="#{msgs.no_results}" rendered="#{(empty applicantProductListBean.dataModel) || (applicantProductListBean.dataModel.rowCount==0)}"/> <rich:datascroller align="center" for="compositeTable" page="#{pageScrollerBean.applicantProductListPage}" id="compositeScroller" reRender="compositeTable" renderIfSinglePage="false" fastControls="hide"> <f:facet name="first"> <h:outputText value="#{msgs.first}" styleClass="scrollerCell" /> </f:facet> <f:facet name="first_disabled"> <h:outputText value="#{msgs.first}" styleClass="scrollerCell" /> </f:facet> <f:facet name="last"> <h:outputText value="#{msgs.last}" styleClass="scrollerCell" /> </f:facet> <f:facet name="last_disabled"> <h:outputText value="#{msgs.last}" styleClass="scrollerCell" /> </f:facet> <f:facet name="next"> <h:outputText value="#{msgs.next}" styleClass="scrollerCell" /> </f:facet> <f:facet name="next_disabled"> <h:outputText value="#{msgs.next}" styleClass="scrollerCell" /> </f:facet> <f:facet name="previous"> <h:outputText value="#{msgs.previous}" styleClass="scrollerCell" /> </f:facet> <f:facet name="previous_disabled"> <h:outputText value="#{msgs.previous}" styleClass="scrollerCell" /> </f:facet> </rich:datascroller> </h:panelGrid> </f:facet> </rich:dataTable> </h:form> </ui:define> This is the backing bean: @Name("applicantProductListBean") @Scope(ScopeType.PAGE) public class ApplicantProductListBean extends BasePagedSortableFilterableListBean { /** * Public field for ad-hoc injection to work. */ @EJB(name = "FacadeService") public ApplicantFacadeService applicantFacadeService; @Logger private static Log logger; private final int pageSize = 10; @Out(scope = ScopeType.CONVERSATION, required = false) Applicant currentApplicant; @Out(scope = ScopeType.CONVERSATION, required = false) Product product; @Create public void onCreate() { System.out.println("Create"); } @Override protected DataModel initDataModel(int pageSize) { // get filtering and sorting from session sorting = getSorting(); filtering = getFiltering(); // System.out.println("Initializing a Composite3DataModel"); // System.out.println("Pagesize: " + pageSize); // System.out.println("Filtering: " + filtering.getFilteringValues()); // System.out.println("Sorting: " + sorting.getSortingValues()); return new Composite3DataModel(1, sorting, filtering); } // Navigation methods /** * Navigation-returning method, returns the action to follow after pressing * the "Create Applicant" button * * @return the action to be taken */ public Navigation.ApplicantProductList showCreateApplicant() { return Navigation.ApplicantProductList.SHOW_CREATE_APPLICANT; } /** * Navigation-returning method, returns the action to follow after pressing * the "Edit Applicant" button * * @return the action to be taken */ public Navigation.ApplicantProductList showUpdateApplicant( Applicant applicant) { this.currentApplicant = applicant; return Navigation.ApplicantProductList.SHOW_UPDATE_APPLICANT; } /** * Navigation-returning method, returns the action to follow after pressing * the "Delete Applicant" button * * @return the action to be taken */ public Navigation.ApplicantProductList showDeleteApplicant( Applicant applicant) { this.currentApplicant = applicant; return Navigation.ApplicantProductList.SHOW_DELETE_APPLICANT; } /** * Navigation-returning method, returns the action to follow after pressing * the "Create Product" button * * @return the action to be taken */ public Navigation.ApplicantProductList showCreateProduct(Applicant app) { this.product = new Product(); this.product.setApplicant(app); return Navigation.ApplicantProductList.SHOW_CREATE_PRODUCT; } /** * Navigation-returning method, returns the action to follow after pressing * the "Edit Product" button * * @return the action to be taken */ public Navigation.ApplicantProductList showUpdateProduct(Product prod) { this.product = prod; return Navigation.ApplicantProductList.SHOW_UPDATE_PRODUCT; } /** * Navigation-returning method, returns the action to follow after pressing * the "Delete Product" button * * @return the action to be taken */ public Navigation.ApplicantProductList showDeleteProduct(Product prod) { this.product = prod; return Navigation.ApplicantProductList.SHOW_DELETE_PRODUCT; } /** * */ @Override public Sorting getSorting() { if (sorting == null) { return (getSortingFilteringBeanFromSession() .getApplicantProductListSorting()); } return sorting; } /** * */ @Override public void setSorting(Sorting sorting) { getSortingFilteringBeanFromSession().setApplicantProductListSorting( sorting); } /** * */ @Override public Filtering getFiltering() { if (filtering == null) { return (getSortingFilteringBeanFromSession() .getApplicantProductListFiltering()); } return filtering; } /** * */ @Override public void setFiltering(Filtering filtering) { getSortingFilteringBeanFromSession().setApplicantProductListFiltering( filtering); } /** * @return the currentApplicant */ public Applicant getCurrentApplicant() { return currentApplicant; } /** * @param currentApplicant * the currentApplicant to set */ public void setCurrentApplicant(Applicant applicant) { this.currentApplicant = applicant; } /** * The model for this page * */ private class Composite3DataModel extends PagedSortableFilterableDataModel<List<Applicant>> { public Composite3DataModel(int pageSize, Sorting sorting, Filtering filtering) { super(pageSize, sorting, filtering); } @Override protected DataPage<List<Applicant>> fetchPage(int fakeStartRow, int fakePageSize) { // if (logger.isTraceEnabled()) { System.out.println("Getting page with fakeStartRow: " + fakeStartRow + " and fakePageSize " + fakePageSize); // } // to find the page size multiply the startRow and the fakePageSize // (which is 1) to the actual page size int startRow = fakeStartRow * ApplicantProductListBean.this.pageSize; int pageSize = fakePageSize * ApplicantProductListBean.this.pageSize; // if (logger.isTraceEnabled()) { System.out.println("Getting page with startRow: " + startRow + " and pageSize " + pageSize); // } List<Applicant> pageApplicants = applicantFacadeService .findPagedWithCriteria(startRow, pageSize, filtering, sorting); // List<Applicant> pageApplicants = applicantFacadeService // .findPagedWithDynamicQuery(startRow, pageSize, filtering, // sorting, true); // if (logger.isTraceEnabled()) { System.out.println("Set of applicants: " + pageApplicants.size()); // } List<List<Applicant>> pageApplicantsListContainer = new ArrayList<List<Applicant>>(); pageApplicantsListContainer.add(pageApplicants); DataPage<List<Applicant>> dataPage = new DataPage<List<Applicant>>( this.getRowCount(), fakeStartRow, pageApplicantsListContainer); return dataPage; } @Override protected int getDatasetSize() { // int size = getServiceFacade().countWithCriteria(filtering, // sorting); // int size = // applicantFacadeService.countWithDynamicQuery(filtering, sorting, // false); int size = (int) Math.ceil((double) applicantFacadeService .countWithCriteria(filtering, sorting, false) / pageSize); if (logger.isTraceEnabled()) { logger.trace("Got Dataset Size: " + size); } return size; } } /** * @return the product */ public Product getProduct() { return product; } /** * @param product * the product to set */ public void setProduct(Product product) { this.product = product; } }

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