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• Implementing AS 2.0 with FSM?

  - by Up2u

  i have seen many of references of AI and FSM like : http://www.richardlord.net/blog/fini...n-actionscript and sadly im still can't understand the point of the FSM on AS2.0 is it a must to create a class of each state ? i have a project of game and also it has an AI, the AI has 3 state n i said the state is distanceCheck, ChaseTarget, and Hit the target, the game that i create is FPS game and play via by mouse so what i mean is i have create an AI ( and is success ) but i want to convert it to FSM method ... i create : function of CheckDistanceState() and in that function i have to locked the target with an array, and sort it with the nearest distance and locked it and it trigger the function ChaseState(), and in the ChaseState() i insert the Hit() function to destroy the enemy, the 3 function that i created , i call it in the AI_cursor.onEnterframe, ( FPS game that only have a cursor in stage ) is there any chance to implement FSM to my code without to create a class ?? from what i read before , to create a class mean to create an external code outside of the frame ( i used to code in frame) and i stil dont understand about it. sorry if my explaination not clear ...

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• What is a 'good number' of exceptions to implement for my library?

  - by Fuzz

  I've always wondered how many different exception classes I should implement and throw for various pieces of my software. My particular development is usually C++/C#/Java related, but I believe this is a question for all languages. I want to understand what is a good number of different exceptions to throw, and what the developer community expect of a good library. The trade-offs I see include: More exception classes can allow very fine grain levels of error handling for API users (prone to user configuration or data errors, or files not being found) More exception classes allows error specific information to be embedded in the exception, rather than just a string message or error code More exception classes can mean more code maintenance More exception classes can mean the API is less approachable to users The scenarios I wish to understand exception usage in include: During 'configuration' stage, which might include loading files or setting parameters During an 'operation' type phase where the library might be running tasks and doing some work, perhaps in another thread Other patterns of error reporting without using exceptions, or less exceptions (as a comparison) might include: Less exceptions, but embedding an error code that can be used as a lookup Returning error codes and flags directly from functions (sometimes not possible from threads) Implemented an event or callback system upon error (avoids stack unwinding) As developers, what do you prefer to see? If there are MANY exceptions, do you bother error handling them separately anyway? Do you have a preference for error handling types depending on the stage of operation?

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• Particle trajectory smoothing: where to do the simulation?

  - by nkint

  I have a particle system in which I have particles that are moving to a target and the new targets are received via network. The list of new target are some noisy coordinates of a moving target stored in the server that I want to smooth in the client. For doing the smoothing and the particle I wrote a simple particle engine with standard euler integration model. So, my pseudo code is something like that: # pseudo code class Particle: def update(): # do euler motion model integration: # if the distance to the target is more than a limit # add a new force to the accelleration # seeking the target, # and add the accelleration to velocity # and velocity to the position positionHistory.push_back(position); if history.length > historySize : history.pop_front() class ParticleEngine: particleById = dict() # an associative array # where the keys are the id # and particle istances are sotred as values # this method is called each time a new tcp packet is received and parsed def setNetTarget(int id, Vec2D new_target): particleById[id].setNewTarget(new_target) # this method is called each new frame def draw(): for p in particleById.values: p.update() beginVertex(LINE_STRIP) for v in p.positionHistory: vertex(v.x, v.y) endVertex() The new target that are arriving are noisy but setting some accelleration/velocity parameters let the particle to have a smoothed trajectories. But if a particle trajectory is a circle after a while the particle position converge to the center (a normal behaviour of euler integration model). So I decided to change the simulation and use some other interpolation (spline?) or smooth method (kalman filter?) between the targets. Something like: switch( INTERPOLATION_MODEL ): case EULER_MOTION: ... case HERMITE_INTERPOLATION: ... case SPLINE_INTERPOLATION: ... case KALMAN_FILTER_SMOOTHING: ... Now my question: where to write the motion simulation / trajectory interpolation? In the Particle? So I will have some Particle subclass like ParticleEuler, ParticleSpline, ParticleKalman, etc..? Or in the particle engine?

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• Strategies for avoiding SQL in your Controllers... or how many methods should I have in my Models?

  - by Keith Palmer

  So a situation I run into reasonably often is one where my models start to either: Grow into monsters with tons and tons of methods OR Allow you to pass pieces of SQL to them, so that they are flexible enough to not require a million different methods For example, say we have a "widget" model. We start with some basic methods: get($id) insert($record) update($id, $record) delete($id) getList() // get a list of Widgets That's all fine and dandy, but then we need some reporting: listCreatedBetween($start_date, $end_date) listPurchasedBetween($start_date, $end_date) listOfPending() And then the reporting starts to get complex: listPendingCreatedBetween($start_date, $end_date) listForCustomer($customer_id) listPendingCreatedBetweenForCustomer($customer_id, $start_date, $end_date) You can see where this is growing... eventually we have so many specific query requirements that I either need to implement tons and tons of methods, or some sort of "query" object that I can pass to a single -query(query $query) method... ... or just bite the bullet, and start doing something like this: list = MyModel-query(" start_date X AND end_date < Y AND pending = 1 AND customer_id = Z ") There's a certain appeal to just having one method like that instead of 50 million other more specific methods... but it feels "wrong" sometimes to stuff a pile of what's basically SQL into the controller. Is there a "right" way to handle situations like this? Does it seem acceptable to be stuffing queries like that into a generic -query() method? Are there better strategies?

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• Do cross reference database tables have a place in domain driven design?

  - by Mike Cellini

  First some background. Let's say we have a system where a customer is placing an order in a web interface. The items that customer is ordering can priced in various ways. Sometimes including the cost of delivery and sometimes not at all. That pricing effectively depends on a variety of factors including the vendor's own pricing model, that vendor's individual contracts with customers as well as that vendor's contracts with its own suppliers. Let's assume that once a customer places an order for a particular item and chooses a contract if any, the method of delivery can be determined by variables on those contracts. Those delivery methods also live in their own table in the database and have various properties consumed downstream. It makes sense that a cross reference or lookup table would store that information. That table would be loaded into the domain and could then be used to apply the appropriate delivery method while processing the order. Does this make sense in the context of domain driven design? Or is my thinking too relational? Is this logic that should be built into it's own class/method (I mean beyond apply the cross reference table data)?

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• How to make backlight work on Acer 5732z?

  - by Dude Random21

  I want to run 12.04 on my Acer Aspire 5732z. I know from research that these computers have issues with the backlight on Ubuntu. So I tried a couple of solutions: The sudo lightdm restart method. I get no change at all. The sudo setpci -s 00:02.0 F4.B=30 method. This so far has been the most effective. I first tried it in the F1 console, right away I get the screen back, problem is going back to the desktop it goes back to being black. So I tried it from a terminal window and it works as well but as soon as I unplug my external monitor the screen turns black again and doesn't come back. If I plug the monitor back in the screen stays black and the only thing I see is the mouse pointer. From here I go back into console (which I am able to see) and reboot from there. The sudo sed -i 's/GRUB_CMDLINE_LINUX=""/GRUB_CMDLINE_LINUX="acpi_osi=Linux"/g /etc/default/grub method. This one I got no instant change and after reboot still no change. I'm open to pretty much any suggestions you may have.

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• Rotate a vector

  - by marc wellman

  I want my first-person camera to smoothly change its viewing direction from direction d1 to direction d2. The latter direction is indicated by a target position t2. So far I have implemented a rotation that works fine but the speed of the rotation slows down the closer the current direction gets to the desired one. This is what I want to avoid. Here are the two very simple methods I have written so far: // this method initiates the direction change and sets the parameter public void LookAt(Vector3 target) { _desiredDirection = target - _cameraPosition; _desiredDirection.Normalize(); _rotation = new Matrix(); _rotationAxis = Vector3.Cross(Direction, _desiredDirection); _isLooking = true; } // this method gets execute by the Update()-method if _isLooking flag is up. private void _lookingAt() { dist = Vector3.Distance(Direction, _desiredDirection); // check whether the current direction has reached the desired one. if (dist >= 0.00001f) { _rotationAxis = Vector3.Cross(Direction, _desiredDirection); _rotation = Matrix.CreateFromAxisAngle(_rotationAxis, MathHelper.ToRadians(1)); Direction = Vector3.TransformNormal(Direction, _rotation); } else { _onDirectionReached(); _isLooking = false; } } Again, rotation works fine; camera reaches its desired direction. But the speed is not equal over the course of movement - it slows down. How to achieve a rotation with constant speed ?

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• By what features and qualities are "free" and "premium" themes differentiated

  - by Sinthia V

  I have a lot of time invested in creating Wordpress templates. I want to release combinations of these templates along with different styles and Fancy Front pages as "Premium Wordpress Themes". What I need to know is what does "Premium" mean? What do people expect of a GPL theme vs. a Premium theme? Are there features that are considered required to be premium? Are there features that are in demand but considered "exceptional" i.e. not part of every premium theme? How can I tell the difference? I have heard tounge-in-cheek answers that say that any theme that makes money is premium, but I mean to ask about what gives an outstanding theme it's quality. Why is it worth more? I am technically able to do many things, but as a lone developer with a family to feed, I can't afford to spend time on features that no one cares about. I have to try to isolate the things that people want. This is serious food and rent to me. How can I get this kind of info so I can make my project successful?

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• CUDA 4.1 Particle Update

  - by N0xus

  I'm using CUDA 4.1 to parse in the update of my Particle system that I've made with DirectX 10. So far, my update method for the particle systems is 1 line of code within a for loop that makes each particle fall down the y axis to simulate a waterfall: m_particleList[i].positionY = m_particleList[i].positionY - (m_particleList[i].velocity * frameTime * 0.001f); In my .cu class I've created a struct which I copied from my particle class and is as follows: struct ParticleType { float positionX, positionY, positionZ; float red, green, blue; float velocity; bool active; }; Then I have an UpdateParticle method in the .cu as well. This encompass the 3 main parameters my particles need to update themselves based off the initial line of code. : __global__ void UpdateParticle(float* position, float* velocity, float frameTime) { } This is my first CUDA program and I'm at a loss to what to do next. I've tried to simply put the particleList line in the UpdateParticle method, but then the particles don't fall down as they should. I believe it is because I am not calling something that I need to in the class where the particle fall code use to be. Could someone please tell me what it is I am missing to get it working as it should? If I am doing this completely wrong in general, the please inform me as well.

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• Slightly off topic - How to Fix Sky Go Error [t6013-c1501] (and [t6000-c1501])

  - by bconlon

  Sky doesn't seem to understand what their own errors mean, so I cobbled together an understanding from some other posts and managed to get it working.When you see the error [t6013-c1501] instead of your TV programme in Sky Go, it seems to mean:'You registered a device, but then changed the hardware, so now I'm confused!'In other words, the Digital rights management (DRM) used between Sky Go and Silverlight stored an old fingerprint of your PC, but rather than recognising this and allowing you to remove the device, it just disappears from the 'Manage Devices' page.DISCLAIMER: Perform the following steps at your own risk. It worked for me, but I didn't care if it broke stuff. If you care....don't do it!So, to fix this I did the following:1. Login to Sky Go and click 'Watch live TV' from the home page. It will attempt to show Sky News and fail with the error [t6013-c1501].2. Right click on the error and you should see the Menu option 'Silverlight'. Select this and a dialog should appear. Click the 'Application Storage' tab and delete any entry that relates to sky go. Clcik OK to close the dialog.3. Open explorer and navigate to the folder C:\ProgramData\Microsoft\PlayReady4. Rename the file mspr.hds to mspr.hds.OLD5. Go back to the browser and click F5. You may need to logout/login (not sure).Note: Don't rename/delete the folder C:\ProgramData\Microsoft\PlayReady or you will get the error [t6000-c1501]. The folder must exist in order for the new file to be created by Silverlight. Techie talk:So whoever wrote the code to create a new mspr.hds file didn't write code to check the folder existed causing what I assume is a generic error t6000, probably something like:catch (Exception ex) { WriteToLog("Oops, something broke!"); }#

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• Using texture() in combination with JBox2D

  - by Valentino Ru

  I'm getting some trouble using the texture() method inside beginShape()/endShape() clause. In the display()-method of my class TowerElement (a bar which is DYNAMIC), I draw the object like following: void display(){ Vec2 pos = level.getLevel().getBodyPixelCoord(body); float a = body.getAngle(); // needed for rotation pushMatrix(); translate(pos.x, pos.y); rotate(-a); fill(temp); // temp is a color defined in the constructor stroke(0); beginShape(); vertex(-w/2,-h/2); vertex(w/2,-h/2); vertex(w/2,h-h/2); vertex(-w/2,h-h/2); endShape(CLOSE); popMatrix(); } Now, according to the API, I can use the texture() method inside the shape definition. Now when I remove the fill(temp) and put texture(img) (img is a PImage defined in the constructor), the stroke gets drawn, but the bar isn't filled and I get the warning texture() is not available with this renderer What can I do in order to use textures anyway? I don't even understand the error message, since I do not know much about different renderers.

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• Static / Shared Helper Functions vs Built-In Methods

  - by Nathan

  This is a simple question but a design consideration that I often run across in my day to day development work. Lets say that you have a class that represents some kinds of collection. Public Class ModifiedCustomerOrders Public Property Orders as List(Of ModifiedOrders) End Class Within this class you do all kinds of important work, such as combining many different information sources and, eventually, build the Modified Customer Orders. Now, you have different processes that consume this class, each of which needs a slightly different slice of the ModifiedCustomerOrders items. To enable this, you want to add filtering functionality. How do you go about this? Do you: Add Filtering calls to the ModifiedCustomerOrders class so that you can say: MyOrdersClass.RemoveCanceledOrders() Create a Static / Shared "tooling" class that allows you to call: OrdersFilters.RemoveCanceledOrders(MyOrders) Create an extension method to accomplish the same feat as #2 but with less typing: MyOrders.RemoveCanceledOrders() Create a "Service" method that handles the getting of Orders as appropriate to the calling function, while using one of the previous approaches "under the hood". OrdersService.GetOrdersForProcessA() Others? I tend to prefer the tooling / extension method approaches as they make testing a little bit simpler. Although I dependency inject all my sourcing data into the ModifiedCustomerOrders, having it as part of the class makes it a little bit more complicated to test. Typically, I choose to use extension methods where I am doing parameterless transformations / filters. As they get more complex, I will move it into a static class instead. Thoughts on this approach? How would you approach it?

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• I am confused between PHP and ASP.NET to choose as a career in Indian software development context

  - by Confused_Guy

  I need your help(specially from the software professionals of India). I have completed MCA in 2009. After that instead of joining software company I did a Teaching job nearby by home. In the mean time I prepared myself for public sector jobs(bank). I continued my job for 1 year more and left it in 2010. Now in 2012 ,I feel that I should have done the software jobs,so that I could earn my bread and butter and in the mean time I could have prepared for the job.Because,according to my qualification it will give me the best salary. Now I want to go back in software industries. Now all of them are asking for experiences.And I don't have any.....So which language should I learn? And what should I do,because I have two year gap. Some of my friends suggested me to go with PHP as its easier and quicker to get job in India. But Here the PHP guys are getting less salary as compared to ASP.NET. I am planning to begin with PHP and but is it possible to switch to ASP.NET after two years experience. JAVA: I know upto servlet & JSP. Which is nothing in current market. ASP.NET: I know the basics of asp.net upto database connection ie(Gridview). PHP: Only the basics. So what should I do now. Which is most demanding. Does PHP is good, I feel its more like JSP pages. Please guide me, All your suggestions are needed for me.

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• OpenXML error “file is corrupt and cannot be opened.”

  - by nmgomes

  From time to time I ear some people saying their new web application supports data export to Excel format. So far so good … but they don’t tell the all story … in fact almost all the times what is happening is they are exporting data to a Comma-Separated file or simply exporting GridView rendered HTML to an xls file. Ok … it works but it’s not something I would be proud of. So … yesterday I decided to take a look at the Office Open XML File Formats Specification (Microsoft Office 2007+ format) based on well-known technologies: ZIP and XML. I start by installing Open XML SDK 2.0 for Microsoft Office and playing with some samples. Then I decided to try it on a more complex web application and the “file is corrupt and cannot be opened.” message start happening. Google show us that many people suffer from the same and it seems there are many reasons that can trigger this message. Some are related to the process itself, others with encodings or even styling. Well, none solved my problem and I had to dig … well not that much, I simply change the output file extension to zip and extract the zip content. Then I did the same to the output file from my first sample, compare both zip contents with SourceGear DiffMerge and found that my problem was Culture related. Yes, my complex application sets the Thread.CurrentThread.CurrentCulture  to a non-English culture. For sample purposes I was simply using the ToString method to convert numbers and dates to a string representation but forgot that XML is culture invariant and thus using a decimal separator other than “.” will result in a deserialization problem. I solve the “file is corrupt and cannot be opened.” by using Convert.ToString(object, CultureInfo.InvariantCulture) method instead of the ToString method. Hope this can help someone.

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• Correct way to inject dependencies in Business logic service?

  - by Sri Harsha Velicheti

  Currently the structure of my application is as below Web App -- WCF Service (just a facade) -- Business Logic Services -- Repository - Entity Framework Datacontext Now each of my Business logic service is dependent on more than 5 repositories ( I have interfaces defined for all the repos) and I am doing a Constructor injection right now(poor mans DI instead of using a proper IOC as it was determined that it would be a overkill for our project). Repositories have references to EF datacontexts. Now some of the methods in the Business logic service require only one of the 5 repositories, so If I need to call that method I would end up instantiating a Service which will instatiate all 5 repositories which is a waste. An example: public class SomeService : ISomeService { public(IFirstRepository repo1, ISecondRepository repo2, IThirdRepository repo3) {} // My DoSomething method depends only on repo1 and doesn't use repo2 and repo3 public DoSomething() { //uses repo1 to do some stuff, doesn't use repo2 and repo3 } public DoSomething2() { //uses repo2 and repo3 to do something, doesn't require repo1 } public DoSomething3() { //uses repo3 to do something, doesn't require repo1 and repo2 } } Now if my I have to use DoSomething method on SomeService I end up creating both IFirstRepository,ISecondRepository and IThirdRepository but using only IFirstRepository, now this is bugging me, I can seem to accept that I am un-necessarily creating repositories and not using them. Is this a correct design? Are there any better alternatives? Should I be looking at Lazy instantiation Lazy<T> ?

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• You can step over await

  - by Alex Davies

  I’ve just found the coolest feature of VS 2012 by far. I thought that being able to silence an exception from the “exception was thrown” popup was awesome, and the “reload all” button when a project file changes is amazing, but this is way beyond all of that. You can step over awaits when you debug your code!! With F10!!! Ok, so that may not sound such a big deal. You can step over ifs and whiles and no-one is celebrating. But await is different. await actually stops your method, signs up to be notified when a Task is finished,  returns, and resumes your method at some indeterminate point in the future. You could even end up continuing on a completely different thread. All that happens, and all I have to do is press F10. I used to have to painstakingly set a breakpoint on the first line of my callback before stepping over any asynchronous method. Even when we started using async, my mouse would instinctively click the margin every time I wanted to go past an await. And the times I was driven insane by my breakpoint getting hit by some other path of execution I don’t care about. I think this might have been introduced in the VS11 Beta, I’m pretty sure I tried it in the Async CTP in VS2010 and it didn’t work. Now it does! Woop!

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• How are certain analytics metrics (time on site, etc.) usually distributed?

  - by a barking spider

  I'm not sure if I've come to the right place to ask this question, but I'm gathering some information for a research project. We're trying to design an experiment that'll heavily involve web analytics, and I'm trying to figure out some sensible values of mean +/- standard deviation for the following visitor-level (i.e., visitor 1 spends 2 minutes on site, visitor 2 spends 1 minute -- mean 1.5 +/- 0.71...) metrics: time spent on site page views If time allowed, we would put up the sites and gather the information ourselves, but we have a grant deadline coming up. I realize that even though these the distributions of these quantities are probably going to be heavily skewed towards zero, we'll need some reasonable figures or estimates of these figures in order to do sample size calculations, etc. Anyway, I'm not sure where else I'd turn, and I certainly have had a difficult time finding these values in the prior literature. If someone could direct me to a paper with the right information, or if you have these figures on hand (perhaps taken directly from your logs!) -- that would be amazing, and I'd love to hear from you. Thanks in advance, and even though I'm not allowed to reveal too much, rest assured that this info'll be applied towards a good cause :)

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• What is the value of checking in failing unit tests?

  - by user20194

  While there are ways of keeping unit tests from being executed, what is the value of checking in failing unit tests? I will use a simple example: Case Sensitivity. The current code is case sensitive. A valid input into the method is "Cat" and it would return an enum of Animal.Cat. However, the desired functionality of the method should not be case sensitive. So if the method described was passed "cat" it could possibly return something like Animal.Null instead of Animal.Cat and the unit test would fail. Though a simple code change would make this work, a more complex issue may take weeks to fix, but identifying the bug with a unit test could be a less complex task. The application currently being analyzed has 4 years of code that "works". However, recent discussions regarding unit tests have found flaws in the code. Some just need explicit implementation documentation (ex. case sensitive or not), or code that does not execute the bug based on how it is currently called. But unit tests can be created executing specific scenarios that will cause the bug to be seen and are valid inputs. What is the value of checking in unit tests that exercise the bug until someone can get around to fixing the code? Should this unit test be flagged with ignore, priority, category etc, to determine whether a build was successful based on tests executed? Eventually the unit test should be created to execute the code once someone fixes it. On one hand it shows that identified bugs have not been fixed. On the other, there could be hundreds of failed unit tests showing up in the logs and weeding through the ones that should fail vs. failures due to a code check-in would be difficult to find.

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• What is the correct way to install Gnome Shell 3.6 on Ubuntu 12.10?

  - by user74660

  I don't want to use Ubuntu Gnome Remix because I think it is kind of "incomplete". I prefer to install Gnome Shell on Ubuntu 12.10. I've searched the net for instructions on how to do it and found two different ways: Simply search for Gnome Shell on Ubuntu Software Center and install it. Follow the instructions from this WebUpd8's post. Now, my doubt is: what is the differecen between the two methods? Which is the correct way to do it? Does the first one lack features? If so, which ones? Is the second one better? Why? Is there a third and better method I haven't found? By the way, I have already tried (for testing purposes) the second method (WebUpd8's) and noticed that it installed some apps I really don't want to have, such as AbiWord and Gnumeric, because they are Gnome's default applications. So, "if" the second method is the way to go, I can certainly remove those apps manually, after installation, with no worries, right? Thank you very much for your attention.

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• Designing object oriented programming

  - by Pota Onasys

  Basically, I want to make api calls using an SDK I am writing. I have the following classes: Car CarData (stores input values needed to create a car like model, make, etc) Basically to create a car I do the following: [Car carWithData: cardata onSuccess: successHandler onError: errorHandler] that basically is a factory method that creates instance of Car after making an API call request and populating the new Car class with the response and passes that instance to the successHandler. So "Car" has the above static method to create that car, but also has non-static methods to edit, delete cars (which would make edit, delete API calls to the server) So when the Car create static method passes a new car to the successHandler by doing the following: successHandler([[Car alloc] initWithDictionary: dictionary) The success handler can go ahead and use that new car to do the following: [car update: cardata] [car delete] considering the new car object now has an ID for each car that it can pass to the update and delete API calls. My questions: Do I need a cardata object to store user inputs or can I store them in the car object that would also later store the response from all of the api calls? How can I improve this model? With regards to CarData, note that there might be different inputs for the different API calls. So create function might need to know model, make, etc, but find function might need to know the number of items to find, the limit, the start id, etc.

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• How to automatically mount a folder and change ownership from root in virtualbox

  - by Fiztban

  It is my first time using virtualbox and ubuntu (14.04), I am on a host Windows 7 OS. I am trying to mount a shared folder that has files I need to access both in the virtualbox and on the windows OS. I have successfully mounted them using the vboxsf from the Guest Additions installed. To mount I used the command sudo mount -t vboxsf <dir name in vbox> <directory in linux for example I used sudo mount -t vboxsf Test /home/user/Test I found several ways of mounting the directories automatically upon startup using for example the /etc/rc.local method (here) where you modify said file appending the command to it (without sudo). Or by using the fstab method (here). I prefer the rc.local method personally. Once mounted it has permissions dr-xr-xr-x however once mounted the directory is of root ownership and chown user /home/user/Test has no effect. This means I cannot make or change files in it as a normal user. In the VirtualBox the directory to be shared is not set as read-only. Is there a way to automatically mount the shared folder and assign ownership to my non root user?

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• What's the point of the Prototype design pattern?

  - by user1905391

  So I'm learning about design patterns in school. Many of them are silly little ideas, but nevertheless solve some recurring problems(singleton, adapters, asynchronous polling, ect). But today I was told about the so called 'Prototype' design pattern. I must be missing something, because I don't see any benefits from it. I've seen people online say it's faster than using "new"' but this is doesn't make any sense, since at some point, regardless how the new object is created, memory needs to be allocated for it ect. Furthermore, doesn't this pattern run in the same circles as the 'chicken or egg' problem? By this I mean, since the prototype pattern essentially is just cloning objects, at some point the original object must be created itself (ie, not cloned). So this would mean, that I would need to have an existing copy of every object that I would ever want to clone already ready to clone? Seems stupid to me. Can anyone explain what the use of this pattern is? Original post: http://stackoverflow.com/questions/13887704/whats-the-point-of-the-prototype-design-pattern

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• multi-thread in mmorpg server

  - by jean

  For MMORPG, there is a tick function to update every object's state in a map. The function was triggered by a timer in fixed interval. So each map's update can be dispatch to different thread. At other side, server handle player incoming package have its own threads also: I/O threads. Generally, the handler of the corresponding incoming package run in I/O threads. So there is a problem: thread synchronization. I have consider two methods: Synchronize with mutex. I/O thread lock a mutex before execute handler function and map thread lock same mutex before it execute map's update. Execute all handler functions in map's thread, I/O thread only queue the incoming handler and let map thread to pop the queue then call handler function. These two have a disadvantage: delay. For method 1, if the map's tick function is running, then all clients' request need to waiting the lock release. For method 2, if map's tick function is running, all clients' request need to waiting for next tick to be handle. Of course, there is another method: add lock to functions that use data which will be accessed both in I/O thread & map thread. But this is hard to maintain and easy to goes incorrect. It needs carefully check all variables whether or not accessed by both two kinds thread. My problem is: is there better way to do this? Notice that I said map is logic concept means no interactions can happen between two map except transport. I/O thread means thread in 3rd part network lib which used to handle client request.

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• Mahout - Clustering - "naming" the cluster elements

  - by Mark Bramnik

  I'm doing some research and I'm playing with Apache Mahout 0.6 My purpose is to build a system which will name different categories of documents based on user input. The documents are not known in advance and I don't know also which categories do I have while collecting these documents. But I do know, that all the documents in the model should belong to one of the predefined categories. For example: Lets say I've collected a N documents, that belong to 3 different groups : Politics Madonna (pop-star) Science fiction I don't know what document belongs to what category, but I know that each one of my N documents belongs to one of those categories (e.g. there are no documents about, say basketball among these N docs) So, I came up with the following idea: Apply mahout clustering (for example k-mean with k=3 on these documents) This should divide the N documents to 3 groups. This should be kind of my model to learn with. I still don't know which document really belongs to which group, but at least the documents are clustered now by group Ask the user to find any document in the web that should be about 'Madonna' (I can't show to the user none of my N documents, its a restriction). Then I want to measure 'similarity' of this document and each one of 3 groups. I expect to see that the measurement for similarity between user_doc and documents in Madonna group in the model will be higher than the similarity between the user_doc and documents about politics. I've managed to produce the cluster of documents using 'Mahout in Action' book. But I don't understand how should I use Mahout to measure similarity between the 'ready' cluster group of document and one given document. I thought about rerunning the cluster with k=3 for N+1 documents with the same centroids (in terms of k-mean clustering) and see whether where the new document falls, but maybe there is any other way to do that? Is it possible to do with Mahout or my idea is conceptually wrong? (example in terms of Mahout API would be really good) Thanks a lot and sorry for a long question (couldn't describe it better) Any help is highly appreciated P.S. This is not a home-work project :)

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• How can you easily determine the textureRect for tiled maps in SFML 2.0?

  - by ThePlan

  I'm working on creating a 2d map prototype, and I've come across the rendering bit of it. I have a tilesheet with tiles, each tile is 30x30 pixels, and there's a 1px border to delimitate them. In SFML the usual method of drawing a part of a tilesheet is declaring an IntRect with the rectangle coordinates then calling the setTextureRectangle() method to a sprite. In a small game it would work, but I have well over 45 tiles and adding more every day, I can't declare 45 intRects for every material, the map is not optimized yet, it would get even worse if I would have to call the setTextureRect() method, aside from declaring 45 rectangleInts. How could I simplify this task? All I need is a very simple and flexible solution for extracting a region of the tilesheet. Basically I have a Tile class. I create multiple instances of tiles (vectors) and each tile has a position and a material. I parse a map file and as I parse it I set the materials of the map according to the parsed map file, and all I need to do is render. Basically I need to do something like this: switch(tile.getMaterial()) { case GRASS: material_sprite.setTextureRect(something); window.draw(material_sprite); break; case WATER: material_sprite.setTextureRect(something); window.draw(material_sprite); break; // handle more cases }

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