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• What are the relative merits for implementing an Erlang-style "Continuation" pattern in C#

  - by JoeGeeky

  What are the relative merits (or demerits) for implementing an Erlang-style "Continuation" pattern in C#. I'm working on a project that has a large number of Lowest priority threads and I'm wondering if my approach may be all wrong. It would seem there is a reasonable upper limit to the number of long-running threads that any one Process 'should' spawn. With that said, I'm not sure what would signal the tipping-point for too many thread or when alternate patterns such as "Continuation" would be more suitable. In this case, many of the threads do a small amount of work and then sleep until woken to go again (Ex. Heartbeat, purge caches, etc...). This continues for the life of the Process.

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• how to write high quality GUI software with qt?

  - by Opetmar

  I want to write a project using QT library, so after learning the library and mastering it how should I start, what other libraries or things that I should learn? are there any other tools that will help me during the development or tools well help the end user to install the software and using it? What are the things that I should be aware? what are the things that I should avoid so it can run efficiently?

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• Why not expose a primary key

  - by Angelo Neuschitzer

  In my education I have been told that it is a flawed idea to expose actual primary keys (not only DB keys, but all primary accessors) to the user. I always thought it to be a security problem (because an attacker could attempt to read stuff not their own). Now I have to check if the user is allowed to access anyway, so is there a different reason behind it? Also, as my users have to access the data anyway I will need to have a public key for the outside world somewhere in between. Now that public key has the same problems as the primary key, doesn't it?

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• Which data structure you will use to for a witness list?

  - by mateen

  I'm making a game where the plot is a bank robbery. Lots of people witness that robbery. The game will load a list of suspects, while the players (witnesses) will have to identify the suspects of this robbery. The game should load a list of suspects to identify the one as quickly as possible. Admin can add/remove suspects in the lists and two or more lists of suspects can also be merged into one (to show it to the player). The question is which data structure will be suitable to develop the lists?

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• Preffered lambda syntax?

  - by Roger Alsing

  I'm playing around a bit with my own C like DSL grammar and would like some oppinions. I've reserved the use of "(...)" for invocations. eg: foo(1,2); My grammar supports "trailing closures" , pretty much like Ruby's blocks that can be passed as the last argument of an invocation. Currently my grammar support trailing closures like this: foo(1,2) { //parameterless closure passed as the last argument to foo } or foo(1,2) [x] { //closure with one argument (x) passed as the last argument to foo print (x); } The reason why I use [args] instead of (args) is that (args) is ambigious: foo(1,2) (x) { } There is no way in this case to tell if foo expects 3 arguments (int,int,closure(x)) or if foo expects 2 arguments and returns a closure with one argument(int,int) - closure(x) So thats pretty much the reason why I use [] as for now. I could change this to something like: foo(1,2) : (x) { } or foo(1,2) (x) -> { } So the actual question is, what do you think looks best? [...] is somewhat wrist unfriendly. let x = [a,b] { } Ideas?

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• Balancing game difficulty against player progression

  - by Raven Dreamer

  It seems that the current climate of games seems to cater to an obvious progression of player power, whether that means getting a bigger, more explosive gun in Halo, leveling up in an RPG, or unlocking new options in Command and Conquer 4. Yet this concept is not exclusive to video or computer games -- even in Dungeons and Dragons players can strive to acquire a +2 sword to replace the +1 weapon they've been using. Yet as a systems designer, the concept of player progression is giving me headache after headache. Should I balance around the players exact capabilities and give up on a simple linear progression? (I think ESIV:Oblivion is a good example of this) Is it better to throw the players into an "arms race" with their opponents, where if the players don't progress in an orderly manner, it is only a matter of time until gameplay is unbearably difficult? (4th Edition DnD strikes me as a good example of this) Perhaps it would make most sense to untether the core gameplay mechanics from progression at all -- give them flashier, more interesting (but not more powerful!) ways to grow?

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• Switch vs Polymorphism when dealing with model and view

  - by Raphael Oliveira

  I can't figure out a better solution to my problem. I have a view controller that presents a list of elements. Those elements are models that can be an instance of B, C, D, etc and inherit from A. So in that view controller, each item should go to a different screen of the application and pass some data when the user select one of them. The two alternatives that comes to my mind are (please ignore the syntax, it is not a specific language) 1) switch (I know that sucks) //inside the view controller void onClickItem(int index) { A a = items.get(index); switch(a.type) { case b: B b = (B)a; go to screen X; x.v1 = b.v1; // fill X with b data x.v2 = b.v2; case c: go to screen Y; etc... } } 2) polymorphism //inside the view controller void onClickItem(int index) { A a = items.get(index); Screen s = new (a.getDestinationScreen()); //ignore the syntax s.v1 = a.v1; // fill s with information about A s.v2 = a.v2; show(s); } //inside B Class getDestinationScreen(void) { return Class(X); } //inside C Class getDestinationScreen(void) { return Class(Y); } My problem with solution 2 is that since B, C, D, etc are models, they shouldn't know about view related stuff. Or should they in that case?

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• Java Desktop Application For Network users

  - by Motasem Abu Aker

  I'm developing a desktop application using Java. My application will run in a network environment where multiple users will access the same database through the application. There will be basic CRUD opreations (Insert, Update, Delete, & select), which means there will be chances of deadlock, or two users trying to update the same record at same time. I'm using the following Java Swing for Clients (MVC). MySQL Server for database (InnODB). Java Web start. Now, MySQL is centralized on the network, and all of the clients connect to it. The Application for ERP Purpose. I searched the internet to find a very good solution to ensure data integrity & to make sure that when updating one record from one client, other clients are aware of it. I read about Socket-server-client & RESTful web services. I don't want to go web application & don't want to use any extra libraries. So how can I handle this scenario: If User A updates a record: Is there a way to update User B's screen with the new value? If user A starts updating a record, how can I prevent other users from attempting to update the same record?

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• Is extensive documentation a code smell?

  - by Griffin

  Every library, open-source project, and SDK/API I've ever come across has come packaged with a (usually large) documentation file, and this seems contradictory to the wide-spread belief that good code needs little to no comments. What separates documentation from this programming methodology? a one to two page overview of a package seems reasonable, but elegant code combined with standard intelisense should have theoretically deprecated the practice of documentation by now IMO. I feel like companies only create detailed documentation and tutorials because its what they've always done. Why should developers have to constantly be searching through online documentation in order to learn how to do things when such information should be intrinsic to the classes, methods and namespaces?

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• Building a distributed system on Amazon Web Services

  - by Songo

  Would simply using AWS to build an application make this application a distributed system? For example if someone uses RDS for the database server, EC2 for the application itself and S3 for hosting user uploaded media, does that make it a distributed system? If not, then what should it be called and what is this application lacking for it to be distributed? Update Here is my take on the application to clarify my approach to building the system: The application I'm building is a social game for Facebook. I developed the application locally on a LAMP stack using Symfony2. For production I used an a single EC2 Micro instance for hosting the app itself, RDS for hosting my database, S3 for the user uploaded files and CloudFront for hosting static content. I know this may sound like a naive approach, so don't be shy to express your ideas.

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• The next next C++ [closed]

  - by Roger Pate

  It's entirely too early for speculation on what C++ will be like after C++0x, but idle hands make for wild predictions. What features would you find useful and why? Is there anything in another language that would fit nicely into the state of C++ after 0x? What should be considered for the next TC and TR? (Mostly TR, as the TC would depend more on what actually becomes the next standard.) Export was removed, rather than merely deprecated, in 0x. (It remains a keyword.) What other features carry so much baggage to also be more harmful than helpful? ISO Standards' process I'm not involved in the C++ committee, but it's also a mystery, unfortunately, to most programmers using C++. A few things worth keeping in mind: There will be 10 years between standards, barring extremely exceptional circumstances. The standard can get "bug fixes" in the form of a Technical Corrigendum. This happened to C++98 with TC1, named C++03. It fixed "simple" issues such as making the explicit guarantee that std::vector stores items contiguously, which was always intended. The committee can issue reports which can add to the language. This happened to C++98/03 with TR1 in 2005, which introduced the std::tr1 namespace.

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• Examples of Liskov Substitution

  - by james lewis

  I'm facilitating a session next week on the Liskov Substitution Principle and I was wondering if anyone had any examples of violations 'from the trenches'? I'm looking for something other than uncle Bob's rectangle - square problem and the persistent set problem he talks about in A-PPP (although that is a great example). So far I'm using the example of a (very simple) List and an IndexedList as the 'correct' use of inheritance. And the addition of a Set to this hierarchy as a violation (as a Set is distinct; strengthening the pre condition of the Add method). I've also taken this great example and it's solution from this question Both those examples are great but I'm looking for something more subtle and harder to spot. So far I've come up with nothing so if you've got a great, subtle example post it up. Also, any metaphors you've come across that helped you understand LSP would be really useful too.

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• What good books are out there on program execution models? [on hold]

  - by murungu

  Can anyone out there name a few books that address the topic of program execution models?? I want a book that can answer questions such as... What is the difference between interpreted and compiled languages and what are the performance consequences at runtime?? What is the difference between lazy evaluation, eager evaluation and short circuit evaluation?? Why would one choose to use one evaluation strategy over another?? How do you simulate lazy evaluation in a language that favours eager evaluation??

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• Good free CSS Sprite for icons

  - by Saif Bechan

  I am working on a small project where I need some of the basic icons: edit, favorite, delete. You know them. Now i can download them all seperate, and put them together in a sprite, but I was wondering if there are ready to download sprites which I can use. Now I am working on an accounting app, so it would be nice if the icons were not too childish. A little but of fancy business type icons. Thanks

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• Objective C - Aggro with Images

  - by Will

  I have three UIImageViews. enemy1, enemy1AggroBox and mainSprite. What I want to do is when mainSprite and enemy1AggroBox interect, I want enemy1 to start moving towards mainSprite. Basically creating aggro for a game. if(CGRectIntersectsRect(mainSprite.frame, enemy1AggroBox.frame)){ //Code here// } My plan would be to call this method in viewDidLoad. I'm not using any sort of framework like cocos2d or OpenGLES. If you need to see any more code just ask.

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• Server-side Architecture for Online Game

  - by Draiken

  Hi, basically I have a game client that has communicate with a server for almost every action it takes, the game is in Java (using LWJGL) and right now I will start making the server. The base of the game is normally one client communicating with the server alone, but I will require later on for several clients to work together for some functionalities. I've already read how authentication server should be sepparated and I intend on doing it. The problem is I am completely inexperienced in this kind of server-side programming, all I've ever programmed were JSF web applications. I imagine I'll do socket connections for pretty much every game communication since HTML is very slow, but I still don't really know where to start on my server. I would appreciate reading material or guidelines on where to start, what architecture should the game server have and maybe some suggestions on frameworks that could help me getting the client-server communication. I've looked into JNAG but I have no experience with this kind of thing, so I can't really tell if it is a solid and good messaging layer. Any help is appreciated... Thanks !

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• Code and Slides: Techniques, Strategies, and Patterns for Structuring JavaScript Code

  - by dwahlin

  This presentation was given at the spring 2012 DevConnections conference in Las Vegas and is based on my Structuring JavaScript Code course from Pluralsight. The goal of the presentation is to show how closures combined with code patterns can be used to provide structure to JavaScript code and make it more re-useable, maintainable, and less susceptible to naming conflicts.  Topics covered include: Closures Using Object literals Namespaces The Prototype Pattern The Revealing Module Pattern The Revealing Prototype Pattern View more of my presentations here. Sample code from the presentation can be found here. Check out the full-length course on the topic at Pluralsight.com.

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• responsibility for storage

  - by Stefano Borini

  A colleague and I were brainstorming about where to put the responsibility of an object to store itself on the disk in our own file format. There are basically two choices: object.store(file) fileformatWriter.store(object) The first one gives the responsibility of serialization on the disk to the object itself. This is similar to the approach used by python pickle. The second groups the representation responsibility on a file format writer object. The data object is just a plain data container (eventually with additional methods not relevant for storage). We agreed on the second methodology, because it centralizes the writing logic from generic data. We also have cases of objects implementing complex logic that need to store info while the logic is in progress. For these cases, the fileformatwriter object can be passed and used as a delegate, calling storage operations on it. With the first pattern, the complex logic object would instead accept the raw file, and implement the writing logic itself. The first method, however, has the advantage that the object knows how to write and read itself from any file containing it, which may also be convenient. I would like to hear your opinion before starting a rather complex refactoring.

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• Object behaviour or separate class?

  - by Andrew Stephens

  When it comes to OO database access you see two common approaches - the first is to provide a class (say "Customer") with methods such as Retrieve(), Update(), Delete(), etc. The other is to keep the Customer class fairly lightweight (essentially just properties) and perform the database access elsewhere, e.g. using a repository. This choice of approaches doesn't just apply to database access, it can crop up in many different OOD scenarios. So I was wondering if one way is preferable over the other (although I suspect the answer will be "it depends")! Another dev on our team argues that to be truly OO the class should be "self-contained", i.e. providing all the methods necessary to manipulate and interact with that object. I personally prefer the repository approach - I don't like bloating the Customer class with all that functionality, and I feel it results in cleaner code having it elsewhere, but I can't help thinking I'm seriously violating core OO concepts! And what about memory implications? If I retrieve thousands of Customer objects I'm assuming those with the data access methods will take up a lot more memory than the property-only objects?

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• Beginning HTML and CSS [closed]

  - by romani

  My goal of learning HTML and CSS is to be able to modify popular scripts such as Wordpress, vBulletin, Drupal, etc. I haven't started yet learning CSS and HTML or XHTML. I see many, many books and tutorials out there so it is difficult to make a choice. I think most of web designers were like me in the past and have read many books. So, could you tell me about 1 good book for HTML and 1 good book for CSS? and if I should read the book from cover to cover or only learning the basics is enough for modifying Wordpress, for example!

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• Variable declaration versus assignment syntax

  - by rwallace

  Working on a statically typed language with type inference and streamlined syntax, and need to make final decision about syntax for variable declaration versus assignment. Specifically I'm trying to choose between: // Option 1. Create new local variable with :=, assign with = foo := 1 foo = 2 // Option 2. Create new local variable with =, assign with := foo = 1 foo := 2 Creating functions will use = regardless: // Indentation delimits blocks square x = x * x And assignment to compound objects will do likewise: sky.color = blue a[i] = 0 Which of options 1 or 2 would people find most convenient/least surprising/otherwise best?

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• 2D pathfinding - finding smooth paths

  - by Kooi Nam Ng

  I was trying to implement a simple pathfinding, but the outcome is less satisfactory than what I intended to achieve. The thing is units in games like Starcraft 2 move in all directions whereas units in my case only move in at most 8 directions (Warcraft 1 style) as these 8 directions direct to next available nodes (they move from a tile to next neighboring tile). What should I do in order to achieve the result as in Starcraft 2? Shrink the tile size? On the picture you can see a horizontal line of rock tiles being obstacles, and the found path marked as green tiles. The red line is the path I want to achieve.

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• When do you use a struct instead of a class?

  - by jkohlhepp

  What are your rules of thumb for when to use structs vs. classes? I'm thinking of the C# definition of those terms but if your language has similar concepts I'd like to hear your opinion as well. I tend to use classes for almost everything, and use structs only when something is very simplistic and should be a value type, such as a PhoneNumber or something like that. But this seems like a relatively minor use and I hope there are more interesting use cases.

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• How to refactor and improve this XNA mouse input code?

  - by Andrew Price

  Currently I have something like this: public bool IsLeftMouseButtonDown() { return currentMouseState.LeftButton == ButtonState.Pressed && previousMouseSate.LeftButton == ButtonState.Pressed; } public bool IsLeftMouseButtonPressed() { return currentMouseState.LeftButton == ButtonState.Pressed && previousMouseSate.LeftButton == ButtonState.Released; } public bool IsLeftMouseButtonUp() { return currentMouseState.LeftButton == ButtonState.Released && previousMouseSate.LeftButton == ButtonState.Released; } public bool IsLeftMouseButtonReleased() { return currentMouseState.LeftButton == ButtonState.Released && previousMouseSate.LeftButton == ButtonState.Pressed; } This is fine. In fact, I kind of like it. However, I'd hate to have to repeat this same code five times (for right, middle, X1, X2). Is there any way to pass in the button I want to the function so I could have something like this? public bool IsMouseButtonDown(MouseButton button) { return currentMouseState.IsPressed(button) && previousMouseState.IsPressed(button); } public bool IsMouseButtonPressed(MouseButton button) { return currentMouseState.IsPressed(button) && !previousMouseState.IsPressed(button); } public bool IsMouseButtonUp(MouseButton button) { return !currentMouseState.IsPressed(button) && previousMouseState.IsPressed(button); } public bool IsMouseButtonReleased(MouseButton button) { return !currentMouseState.IsPressed(button) && previousMouseState.IsPressed(button); } I suppose I could create some custom enumeration and switch through it in each function, but I'd like to first see if there is a built-in solution or a better way.. Thanks!

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• What to include in metadata?

  - by shyam

  I'm wondering if there are any general guidelines or best practices regarding when to split data into a metadata format, as oppose to directly embedding it within the data. (Specific example below). My understanding of metadata is that it describes data (without the need to actually look at the data), allowing for data to be quickly search/filtered for easy access. Let's take for example a simple 3D model format. The actual data file itself is a binary file containing vertices and colors. Things like creation date, modified data and author name would be things that describe the binary data, so I would say these belong as metadata (outside of the binary file). But what if the application had no need to search or filter by these fields? Would it be acceptable to embed these fields directly into the binary data itself? Could they be duplicated in both the binary data and the meta data, or would this be considered bad practice? What about more ambiguous fields such as the model name, which could be considered part of the data itself, but also as data describing the binary data?... How do you decide which data to embed in the actual binary file, as opposed to separating into a more flexible metadata format? Thanks!

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