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  • How would you code an efficient Circular Buffer in Java or C#

    - by Cheeso
    I want a simple class that implements a fixed-size circular buffer. It should be efficient, easy on the eyes, generically typed. EDIT: It need not be MT-capable, for now. I can always add a lock later, it won't be high-concurrency in any case. Methods should be: .Add and I guess .List, where I retrieve all the entries. On second thought, Retrieval I think should be done via an indexer. At any moment I will want to be able to retrieve any element in the buffer by index. But keep in mind that from one moment to the next Element[n] may be different, as the Circular buffer fills up and rolls over. This isn't a stack, it's a circular buffer. Regarding "overflow": I would expect internally there would be an array holding the items, and over time the head and tail of the buffer will rotate around that fixed array. But that should be invisible from the user. There should be no externally-detectable "overflow" event or behavior. This is not a school assignment - it is most commonly going to be used for a MRU cache or a fixed-size transaction or event log.

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  • designing an ASP.NET MVC partial view - showing user choices within a large set of choices

    - by p.campbell
    Consider a partial view whose job is to render markup for a pizza order. The desire is to reuse this partial view in the Create, Details, and Update views. It will always be passed an IEnumerable<Topping>, and output a multitude of checkboxes. There are lots... maybe 40 in all (yes, that might smell). A-OK so far. Problem The question is around how to include the user's choices on the Details and Update views. From the datastore, we've got a List<ChosenTopping>. The goal is to have each checkbox set to true for each chosen topping. What's the easiest to read, or most maintainable way to achieve this? Potential Solutions Create a ViewModel with the List and List. Write out the checkboxes as per normal. While writing each, check whether the ToppingID exists in the list of ChosenTopping. Create a new ViewModel that's a hybrid of both. Perhaps call it DisplayTopping or similar. It would have property ID, Name and IsUserChosen. The respective controller methods for Create, Update, and Details would have to create this new collection with respect to the user's choices as they see fit. The Create controller method would basically set all to false so that it appears to be a blank slate. The real application isn't pizza, and the organization is a bit different from the fakeshot, but the concept is the same. Is it wise to reuse the control for the 3 different scenarios? How better can you display the list of options + the user's current choices? Would you use jQuery instead to show the user selections? Any other thoughts on the potential smell of splashing up a whole bunch of checkboxes?

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  • C++ game designing & polymorphism question

    - by Kotti
    Hi! I'm trying to implement some sort of 'just-for-me' game engine and the problem's plot goes the following way: Suppose I have some abstract interface for a renderable entity, e.g. IRenderable. And it's declared the following way: interface IRenderable { // (...) // Suppose that Backend is some abstract backend used // for rendering, and it's implementation is not important virtual void Render(Backend& backend) = 0; }; What I'm doing right now is something like declaring different classes like class Ball : public IRenderable { virtual void Render(Backend& backend) { // Rendering implementation, that is specific for // the Ball object // (...) } }; And then everything looks fine. I can easily do something like std::vector<IRenderable*> items, push some items like new Ball() in this vector and then make a call similiar to foreach (IRenderable* in items) { item->Render(backend); } Ok, I guess it is the 'polymorphic' way, but what if I want to have different types of objects in my game and an ability to manipulate their state, where every object can be manipulated via it's own interface? I could do something like struct GameState { Ball ball; Bonus bonus; // (...) }; and then easily change objects state via their own methods, like ball.Move(...) or bonus.Activate(...), where Move(...) is specific for only Ball and Activate(...) - for only Bonus instances. But in this case I lose the opportunity to write foreach IRenderable* simply because I store these balls and bonuses as instances of their derived, not base classes. And in this case the rendering procedure turns into a mess like ball.Render(backend); bonus.Render(backend); // (...) and it is bad because we actually lose our polymorphism this way (no actual need for making Render function virtual, etc. The other approach means invoking downcasting via dynamic_cast or something with typeid to determine the type of object you want to manipulate and this looks even worse to me and this also breaks this 'polymorphic' idea. So, my question is - is there some kind of (probably) alternative approach to what I want to do or can my current pattern be somehow modified so that I would actually store IRenderable* for my game objects (so that I can invoke virtual Render method on each of them) while preserving the ability to easily change the state of these objects? Maybe I'm doing something absolutely wrong from the beginning, if so, please point it out :) Thanks in advance!

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  • Measuring time spent in application / thread

    - by Adamski
    I am writing a simulation in Java whereby objects act under Newtonian physics. An object may have a force applied to it and the resulting velocity causes it to move across the screen. The nature of the simulation means that objects move in discrete steps depending on the time ellapsed between the current and previous iteration of the animation loop; e.g public void animationLoop() { long prev = System.currentTimeMillis(); long now; while(true) { long now = System.currentTimeMillis(); long deltaMillis = now - prev; prev = now; if (deltaMillis > 0) { // Some time has passed for (Mass m : masses) { m.updatePosition(deltaMillis); } // Do all repaints. } } } A problem arises if the animation thread is delayed in some way causing a large amount of time to ellapse (the classic case being under Windows whereby clicking and holding on minimise / maximise prevents a repaint), which causes objects to move at an alarming rate. My question: Is there a way to determine the time spent in the animation thread rather than the wallclock time, or can anyone suggest a workaround to avoid this problem? My only thought so far is to contstrain deltaMillis by some upper bound.

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  • Is there such a thing as a converter from php to html?

    - by 0plus1
    Don't think that I'm mad, I understand how php works! That being said. I develop personal website and I usually take advantage of php to avoid repetion during the development phase nothing truly dynamic, only includes for the menus, a couple of foreach and the likes. When the development phase ends I need to give the website in html files to the client. Is there a tool (crawler?) that can do this for me instead of visiting each page and saving the interpreted html?

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  • Android 2.1 address bar causes change in viewport dimensions

    - by davehumyo
    Hi, I have a page that has a 100% width and height div in it (all surrounding elements are sized accordingly so that it does actually achieve 100% width and height). Below that div I have a second div with a fixed height. In mobile safari and blackberry everything is fine, when the page loads the dimensions are applied correctly (the top div filling the viewport) and the user can scroll down to reveal the second div. Android 2.1 also applies the dimensions correctly, but with an added quirk; when the user scrolls down and removes the address bar from the page, the dimensions of the div are recalculated to fill the viewport, causing the content to jump. Ideally I would like the dimensions of the div to remain static when the page is scrolled, but remain 100% so that it will fill the viewport regardless of device size or orientation. Does anyone know of any way to disable this recalculation? Thanks for any help you can provide.

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  • C# Virtual method call in constructor - how to refactor?

    - by Cristi Diaconescu
    I have an abstract class for database-agnostic cursor actions. Derived from that, there are classes that implement the abstract methods for handling database-specific stuff. The problem is, the base class ctor needs to call an abstract method - when the ctor is called, it needs to initialize the database-specific cursor. I know why this shouldn't be done, I don't need that explanation! This is my first implementation, that obviously doesn't work - it's the textbook "wrong way" of doing it. The overridden method accesses a field from the derived class, which is not yet instantiated: public abstract class CursorReader { private readonly int m_rowCount; protected CursorReader() { m_rowCount = CreateCursor(sqlCmd); //virtual call ! } protected abstract int CreateCursor(string sqlCmd); } public class SqlCursorReader : CursorReader { private SqlConnection m_sqlConnection; public SqlCursorReader(string sqlCmd, SqlConnection sqlConnection) { m_sqlConnection = sqlConnection; //field initialized here } protected override int CreateCursor(string sqlCmd) { //uses not-yet-initialized member *m_sqlConnection* //so this throws a NullReferenceException var cursor = new CustomCursor(sqlCmd, m_sqlConnection); return cursor.Count(); } } I will follow up with an answer on my attempts to fix this...

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  • Is there anything bad in declaring static inner class inside interface in java?

    - by Roman
    I have an interface ProductService with method findByCriteria. This method had a long list of nullable parameters, like productName, maxCost, minCost, producer and so on. I refactored this method by introducing Parameter Object. I created class SearchCriteria and now method signature looks like this: findByCriteria (SearchCriteria criteria) I thought that instances of SearchCriteria are only created by method callers and are only used inside findByCriteria method, i.e.: void processRequest() { SearchCriteria criteria = new SearchCriteria () .withMaxCost (maxCost) ....... .withProducer (producer); List<Product> products = productService.findByCriteria (criteria); .... } and List<Product> findByCriteria(SearchCriteria criteria) { return doSmthAndReturnResult(criteria.getMaxCost(), criteria.getProducer()); } So I did not want to create separate public class for SearchCriteria and put it inside ProductServiceInterface: public interface ProductService { List<Product> findByCriteria (SearchCriteria criteria); static class SearchCriteria { ... } } Is there anything bad in this interface? Where whould you place SearchCriteria class?

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  • implementing type inference

    - by deepblue
    well I see some interesting discussions here about static vs. dynamic typing I generally prefer static typing, due to compile type checking, better documented code,etc. However I do agree that they do clutter up the code if done the way Java does it, for example. so Im about to start building a language of my own and type inference is one of the things that I want to implement, in a functional style language... I do understand that it is a big subject, and Im not trying to create something that has not been done before, just basic inferencing... any pointers on what to read up that will help me with this? preferably something more pragmatic/practical as oppose to more theoretical category theory/type theory texts. If there's a implementation discussion text out here, with data structures/algorithms, that would just be lovely much appreciated

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  • Messaging strategies to connect different systems

    - by n002213f
    I have a system to handle Applications online and a different system to send SMS/Email notifications to applicants on completion using web services. I can't guarantee the availability of the SMS/Email gateway. Option 1 After an application is complete, place a message on a JMS queue. A Message Driven bean receives the message and make a call for the web service, if it fails leave the message on the queue. I suspect (please correct if incorrect) that if the gate way is offline the continuosly try to send the message which might use up valuable resources. Can the above option be refined are are there any other messaging strategies that can be used?

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  • Are bad data issues that common?

    - by Water Cooler v2
    I've worked for clients that had a large number of distinct, small to mid-sized projects, each interacting with each other via properly defined interfaces to share data, but not reading and writing to the same database. Each had their own separate database, their own cache, their own file servers/system that they had dedicated access to, and so they never caused any problems. One of these clients is a mobile content vendor, so they're lucky in a way that they do not have to face the same problems that everyday business applications do. They can create all those separate compartments where their components happily live in isolation of the others. However, for many business applications, this is not possible. I've worked with a few clients, one of whose applications I am doing the production support for, where there are "bad data issues" on an hourly basis. Yeah, it's that crazy. Some data records from one of the instances (lower than production, of course) would have been run a couple of weeks ago, and caused some other user's data to get corrupted. And then, a data script will have to be written to fix this issue. And I've seen this happening so much with this client that I have to ask. I've seen this happening at a moderate rate with other clients, but this one just seems to be out of order. If you're working with business applications that share a large amount of data by reading and writing to/from the same database, are "bad data issues" that common in your environment?

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  • Looking for Programming Language that allows you to change true and false.

    - by Maushu
    For my curiosity sake I'm looking for a dynamic object oriented language that allows you to change true to false and vice versa. Something like this: true = false, false = true; This should also affect any conditional statements, therefore 42 == 42 should return False. Basically, with this premise, nothing in the language would be safe from the programmer. Is there any language like this?

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  • Correct model for a database with a table for each user.

    - by BAH
    Kinda stuck here... I have an application with lets say 5000 rows of data per user and was wondering if it was right or wrong to do it this way: On user account creation a new table is created (UserData_[UserID]) or should I just have 1 table for userdata and have everything in there with a column for userid? The reason I am stuck at the moment is that it seems NHibernate isn't able to be mapped to dynamic table names without creating another ISessionFactory which has alot of overhead AFAIK. Any help would be greatly appreciated. Thanks.

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  • How to use Unique Composite Key

    - by LifeH2O
    I have a table Item(ItemName*, ItemSize*, Price, Notes) I was making composite key of (ItemName,ItemSize) to uniquely identify item. And now after reading some answers on stackoverflow suggesting the use of UNIQUE i revised it as Item(ItemID*, ItemName, ItemSize, Price, Notes) But How to apply UNIQUE constraint on ItemName and ItemSize please correct if there is something wrong in question

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  • How to export data which are mapped to enumerations

    - by Joshua
    I have a set of data which needs to be imported from a excel sheet, lets take the simplest example. Note: the data might eventually support uploading any locale. e.g. assuming one of the fields denoting a user is gender mapped to an enumeration and stored in the database as 0 for male and 1 for female. 0 and 1 being short values. If I have to import the values I cannot expect the user to punch in numbers (since they are not intuitive and is cumbersome when the enumerations are bigger), what would be the correct way to map to enumerations. Should we ask them to provide a string value in these cases (e.g. male or female) and provide the transformation to a enum in our code by wring a method public static Gender Gender.fromString(String value)

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  • How best can I extract a logical model from a physical DB model

    - by Dean
    We have made substantial changes to our physical DB, now as it is the ne dof the project I would like to abstract a logical model from this, to allow me to generate schemas for both Oracle and SQL Server. Can anyone guide me as to the best way to achieve this. I was hoping TOAD data modeller would help but I can't seem to see any options to do what I require?

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  • Delivering activity feed items in a moderately scalable way

    - by sotangochips
    The application I'm working on has an activity feed where each user can see their friends' activity (much like Facebook). I'm looking for a moderately scalable way to show a given users' activity stream on the fly. I say 'moderately' because I'm looking to do this with just a database (Postgresql) and maybe memcached. For instance, I want this solution to scale to 200k users each with 100 friends. Currently, there is a master activity table that stores the rendered html for the given activity (Jim added a friend, George installed an application, etc.). This master activity table keeps the source user, the html, and a timestamp. Then, there's a separate ('join') table that simply keeps a pointer to the person who should see this activity in their friend feed, and a pointer to the object in the main activity table. So, if I have 100 friends, and I do 3 activities, then the join table will then grow to 300 items. Clearly this table will grow very quickly. It has the nice property, though, that fetching activity to show to a user takes a single (relatively) inexpensive query. The other option is to just keep the main activity table and query it by saying something like: select * from activity where source_user in (1, 2, 44, 2423, ... my friend list) This has the disadvantage that you're querying for users who may never be active, and as your friend list grows, this query can get slower and slower. I see the pros and the cons of both sides, but I'm wondering if some SO folks might help me weigh the options and suggest one way or they other. I'm also open to other solutions, though I'd like to keep it simple and not install something like CouchDB, etc. Many thanks!

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  • Events in Classes (VB.NET)

    - by Otaku
    I find that I write a lot of code within my classes to keep properties in sync with each other. I've read about Events in Classes, but have not been able to wrap my head around how to make them work for what I'm looking for. I could use some advice here. For example, in this one I always want to keep myColor up to date with any change whatsoever in any or all of the Red, Green or Blue properties. Class myColors Private Property Red As Byte Private Property Green As Byte Private Property Blue As Byte Private Property myColor As Color Sub New() myColor = Color.FromArgb(0, 0, 0) End Sub Sub ChangeRed(ByVal r As Byte) Red = r myColor = Color.FromArgb(Red, Green, Blue) End Sub Sub ChangeBlue(ByVal b As Byte) Blue = b myColor = Color.FromArgb(Red, Green, Blue) End Sub End Class If one or more of those changes, I want myColor to be updated. Easy enough as above, but is there a way to work with events that would automatically do this so I don't have to put myColor = Color.FromArgb(Red, Green, Blue) in every sub routine?

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  • Am I trying to Implement Multiple Inheritance. How can I do this.

    - by Shantanu Gupta
    I have created a class say A which has some functions defined as protected. Now Class B inherits A and class C inherits B. Class A has private default constructor and protected parameterized constructor. I want Class B to be able to access all the protected functions defined in Class A but class C can have access on some of the functions only not all the functions and class C is inheriting class B. How can I restrict access to some of the functions of Class A from Class C ? EDIT: namespace Db { public Class A { private A(){} protected A(string con){assign this value} protected DataTable getTable(){return Table;} protected Sqlparameters setParameters(){return parameter;} } } namespace Data { public Class B:A { protected B():base("constring"){} protected DataTable output(){return getTable();} protected sqlparameter values(param IDataParameter[] parameter){} } } namespace Bsns { public Class C:B { protected C():base(){} protected DataTable show() {return values(setparameter());} } } EDIT I think what I am trying to do here is Multiple inheritance. Please check. Class A { //suppose 10 functions are declared } Class B:A { //5 functions declared which are using A's function in internal body } Class C:B { //using all functions of B but require only 4 functions of A to be accessible by C. }

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  • What technologies/tools do people use to implement live websites ?

    - by MadSeb
    Hi, I have the following situation: -I have a server A hooked up to a piece of hardware that sends values and information out of every second. Programs on the server machine can read these values. This server A is in a very remote location so Internet connection is very slow and not reliable but the connection does exist. Let's say it's a weather station in the Arctic. -Users from the home location want to monitorize the weather values somehow. Well, the users can use a remote desktop connection the server A but that would be too too slow. My idea is somehow to have a website on a web server (let's call the webserver - B and B is in a home location ) and make the server A connect to the server B and somehow send values and the web application reads the values and displays them....... but how to do such a system ?? I know I can use MySQL and have the server A connect to a SQL server on server B and send INSERT queries and have the web application running on server B constantly read from the SQL server but I think that would be way way too slow and I think there has to be a better solution. Any ideas ? BTW. The users should be able to send information to the weather station from the website as well ( so an ADMIN user should be allowed to shut down the weather station from the website or whatever) Best regards, MadSeb

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  • domain modeling naming problem

    - by cherouvim
    Hello There are some simple entities in an application (e.g containing only id and title) which rarely change and are being referenced by the more complex entities of the application. These are usually entities such as Country, City, Language etc. How are these called? I've used the following names for those in the past but I'm not sure which is the best way to call them: reference data lookup values dictionaries thanks

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  • @media queries - one rule overrides another?

    - by John
    I have multiple @media queries all working fine but as soon as i put in a higher max screen-width than 1024px the rules for the higher width gets applied to everything. @media screen and (max-width: 1400px) { #wrap { width: 72%; } } @media screen and (max-width: 1024px) { #slider h2 { width: 100%; } #slider img { margin: 60px 0.83333333333333% 0 2.08333333333333%; } .recent { width: 45.82%; margin: 10px 2.08333333333334% 0 1.875%; } } as you can see 1024px (and also the 800px max-width query) do not change the #wrap width and work fine. As soon as i add the 1400px max-width query it changes them to 72% for ALL sizes and does the same for any element - for instance if i set #slider img to have a margin of 40px it will show at ALL sizes even though it is only in the max-width of 1400px. Am i missing something really obvious? Been trying to work this out for the past 2 days! Thanks, John

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