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• clone() only partially doable; how to react?

  - by hllnll

  Suppose we have a class-hierarchy whose base class B requires a clone() method to be defined in its derivations. Whilst this works perfectly for most of them there is this one derivation X that holds an optional reference to a resource/object that can only be referenced from one instance of X. Whilst the rest of X can be cloned without problems this reference would have to be set to null/nil/nullptr. What is the correct way to handle this situation? X::clone() could throw an UncloneableException. Though this would be correct, it is not satisfying. Set the reference to null/nil/nullptr and leave no notice of it. The user of X has to know about Xs "particularities". Require derivations of B to define B::nearestClone(): the user of B has to be aware that the return value might not be a 1:1 clone. Something else?

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• How to write loosely coupled classes in node.js

  - by lortabac

  I am trying to understand how to design node.js applications, but it seems there is something I can't grasp about asynchronous programming. Let's say my application needs to access a database. In a synchronous environment I would implement a data access class with a read() method, returning an associative array. In node.js, because code is executed asynchronously, this method can't return a value, so, after execution, it will have to "do" something as a side effect. It will then contain at least 1 line of extraneous code which has nothing to do with data access. Multiply this for all methods and all classes and you will very soon have an unmanageable "code soup". What is the proper way to handle this problem? Am I approaching it the wrong way?

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• Calling a web service through a reverse proxy

  - by Ken

  I had a w/s that when I first read the WSDL in test, was http, but needed to be accessed from behind a reverse proxy with https.  Here are the steps: Change the app.config, <httpTransport> to <httpsTransport> Change the app.config and the url address in the <endpoint>to the reverse proxy address Add System.Net.ServicePointManager.ServerCertificateValidationCallback = delegate { return true; };  to disable certificate validation.  This will validate all certificates (including invalid, expired or self-signed ones).

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• Do I need the 'w' component in my Vector class?

  - by bobobobo

  Assume you're writing matrix code that handles rotation, translation etc for 3d space. Now the transformation matrices have to be 4x4 to fit the translation component in. However, you don't actually need to store a w component in the vector do you? Even in perspective division, you can simply compute and store w outside of the vector, and perspective divide before returning from the method. For example: // post multiply vec2=matrix*vector Vector operator*( const Matrix & a, const Vector& v ) { Vector r ; // do matrix mult r.x = a._11*v.x + a._12*v.y ... real w = a._41*v.x + a._42*v.y ... // perspective divide r /= w ; return r ; } Is there a point in storing w in the Vector class?

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• Should I use the factory design pattern for every class?

  - by Frog

  I've been writing a website in PHP. As the code becomes more complex, I keep finding problems that can be solved using the factory design pattern. For example: I've a got a class Page which has subclasses HTMLPage, XMLPage, etc. Depending on some input I need to return an object of either one of these classes. I use the factory design pattern to do this. But as I encounter this problem in more classes, I keep having to change code which still initiates an object using its constructor. So now I'm wondering: is it a good idea to change all code so that it uses the factory design pattern? Or are there big drawbacks? I'm currently in a position to change this, so your answers would be really helpful.

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• Wall avoidance steering

  - by Vodemki

  I making a small steering simulator using the reynolds boid algorythm. Now I want to add a wall avoidance feature. My walls are in 3D and defined using two points like that: ---------. P2 | | P1 .--------- My agents have a velocity, a position, etc... Could you tell me how to make avoidance with my agents ? Vector2D ReynoldsSteeringModel::repulsionFromWalls() { Vector2D force; vector<Wall *> wallsList = walls(); Point2D pos = self()->position(); Vector2D velocity = self()->velocity(); for (unsigned i=0; i<wallsList.size(); i++) { //TODO } return force; } Then I use all the forces returned by my boid functions and I apply it to my agent. I just need to know how to do that with my walls ? Thanks for your help.

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• How do I access column data in a previous select statement from a sub-query? [closed]

  - by payling

  PROBLEM How do I access column data in a previous select statement from a sub-query? Below is a simple mock up of what I'm attempting to do. Tables used: Quotes, Users QUOTES TABLE qid, (quote id) owner_uid, creator_uid SQL SYNTAX: SELECT q.qid, q.owner_uid, q.creator_uid, owner.fname, owner.lname FROM quotes q, (SELECT u.fname, u.lname FROM users u WHERE u.uid = q.owner_uid) AS owner WHERE q.qid = '#' SUMMARY I want to be able to use the quote table's owner_uid and specify it for the owner table so I can return all the owner info for that particular quote. The problem is, q.owner_uid is not recognized in the owner sub-query. What am I doing wrong?

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• Caching preventing users seeing site updates

  - by Timmeh

  I'm experiencing a caching issue I can't explain. This is happening across browsers, IPs and ISPs. If a user force-refreshes, they see the new content. If they then refresh or return to the page, the old one displays. I've tried using headers via PHP such as header( 'Expires: Sat, 26 Jul 1997 05:00:00 GMT' ); header( 'Last-Modified: ' . gmdate( 'D, d M Y H:i:s' ) . ' GMT' ); header( 'Cache-Control: no-store, no-cache, must-revalidate' ); header( 'Cache-Control: post-check=0, pre-check=0', false ); header( 'Pragma: no-cache' ); Laid out correctly, at the very beginning of the file. The problem persists. A pan-ISP proxy is unlikely. Suggestions?

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• Access Control Service: Handling Errors

  - by Your DisplayName here!

  Another common problem with external authentication is how to deal with sign in errors. In active federation like WS-Trust there are well defined SOAP faults to communicate problem to a client. But with web applications, the error information is typically generated and displayed on the external sign in page. The relying party does not know about the error, nor can it help the user in any way. The Access Control Service allows to post sign in errors to a specified page. You setup this page in the relying party registration. That means that whenever an error occurs in ACS, the error information gets packaged up as a JSON string and posted to the page specified. This way you get structued error information back into you application so you can display a friendlier error message or log the error. I added error page support to my ACS2 sample, which can be downloaded here. How to turn the JSON error into CLR types The JSON schema is reasonably simple, the following class turns the JSON into an object: [DataContract] public class AcsErrorResponse {     [DataMember(Name = "context", Order = 1)]     public string Context { get; set; }     [DataMember(Name = "httpReturnCode", Order = 2)]     public string HttpReturnCode { get; set; }     [DataMember(Name = "identityProvider", Order = 3)]        public string IdentityProvider { get; set; }     [DataMember(Name = "timeStamp", Order = 4)]     public string TimeStamp { get; set; }     [DataMember(Name = "traceId", Order = 5)]     public string TraceId { get; set; }     [DataMember(Name = "errors", Order = 6)]     public List<AcsError> Errors { get; set; }     public static AcsErrorResponse Read(string json)     {         var serializer = new DataContractJsonSerializer( typeof(AcsErrorResponse));         var response = serializer.ReadObject( new MemoryStream(Encoding.Default.GetBytes(json))) as AcsErrorResponse;         if (response != null)         {             return response;         }         else         {             throw new ArgumentException("json");         }     } } [DataContract] public class AcsError {     [DataMember(Name = "errorCode", Order = 1)]     public string Code { get; set; }             [DataMember(Name = "errorMessage", Order = 2)]     public string Message { get; set; } } Retrieving the error information You then need to provide a page that takes the POST and deserializes the information. My sample simply fills a view that shows all information. But that’s for diagnostic/sample purposes only. You shouldn’t show the real errors to your end users. public class SignInErrorController : Controller {     [HttpPost]     public ActionResult Index()     {         var errorDetails = Request.Form["ErrorDetails"];         var response = AcsErrorResponse.Read(errorDetails);         return View("SignInError", response);     } } Also keep in mind that the error page is an anonymous page and that you are taking external input. So all the usual input validation applies.

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• How to automatically generate html table from image in Linux?

  - by alfish

  In Photoshop, you can easily devide the image into zones using point and click and it automatically generates the corresponding html with image slices addressed in tables. Gimp also has a Slice (Filter Web Slice) but it is so rudimentary and, as far as I can see, does not allow point and click selection of slices. I am wondering if the functionality can be added into Gimp, or there are other Linux software to do this. I hate to return to Windows jut to do this simple task which I happen to use frequently. Thanks in advance for your suggestions.

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• Backing up VPS and Database Servers for website

  - by TravisK

  I currently have an "un-managed" (no help from hosting company) windows vps server. I am working on a good backup solution to return my site back online within a few hours. I am pretty comfortable backing up and restoring my database, however what is a good solution for backing up my VPS for easy recovery? Should I just use windows backup and create an image? I'm open to suggestions. Additionally, has anyone had to restore an entire VPS before? Is it reasonable to have it back up and running in a few hours?

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• Tester/Doer pattern: Assume the caller conforms to the pattern or be defensive and repeat the check?

  - by Daniel Hilgarth

  Assume a simple class that implements the Tester/Doer pattern: public class FooCommandHandler : ICommandHandler { public bool CanHandle(object command) { return command is FooCommand; } public void Handle(object command) { var fooCommand = (FooCommand)command; // Do something with fooCommand } } Now, if someone doesn't conform to the pattern and calls Handle without verifying the command via CanHandle, the code in Handle throws an exception. However, depending on the actual implementation of Handle this can be a whole range of different exceptions. The following implementation would check CanHandle again in Handle and throw a descriptive exception: public void Handle(object command) { if(!CanHandle(command)) throw new TesterDoerPatternUsageViolationException("Please call CanHandle first"); // actual implementation of handling the command. } This has the advantage that the exception is very descriptive. It has the disadvantage that CanHandle is called twice for "good" clients. Is there a consensus on which variation should be used?

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• Clone User Profile with Encrypted Home Folder

  - by doublerainbow64

  I'd like to clone my user profile on my local machine. I'd like to do so, just to keep all the preferences and not to have to redefine all of them manually. I've tried this, but when I login, it will just return to KDM login screen. BTW I'm using Kubuntu 14.04. What might be interesting: I have encrypted my home folder. Does this make any difference? I've also tried to copy the contents of .kde folder into /etc/skel, but this had no effect. Thank you very much in advance, doublerainbow64

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• What is the correct way to implement hit detection with non-rectangular sprites?

  - by hogni89

  What is the correct way to implement hit or touch detection for non-rectangular sprites in Cocos2d? I am working on a jigsaw puzzle, so our sprites have some strange forms (jigsaw puzzle bricks). As of now, we have implemented the "detection" this way: - (void)selectSpriteForTouch:(CGPoint)touchLocation { CCSprite * newSprite = nil; // Loop array of sprites for (CCSprite *sprite in movableSprites) { // Check if sprite is hit. // TODO: Swap if with something better. if (CGRectContainsPoint(sprite.boundingBox, touchLocation)) { newSprite = sprite; break; } } if (newSprite != selSprite) { // Move along, nothing to see here // Not the problem } } - (BOOL)ccTouchBegan:(UITouch *)touch withEvent:(UIEvent *)event { CGPoint touchLocation = [self convertTouchToNodeSpace:touch]; [self selectSpriteForTouch:touchLocation]; return TRUE; } I know that the problem is in the keyword "sprite.boundingBox". Is there a better way of implementing this, or is it a limitation when using sprites based on .png's? If so, how should I proceed?

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• Progressbar patterns (Eclipse)

  - by JesperE

  I've struggled quite a bit with Eclipse and progress-monitors to try to have good progressbars which report useful progress information to the user. Inevitably the code gets cluttered with lots of things like if (monitor.isCancelled()) return; ... lengthyMethodCall(monitor.newChild(10)); and all over the place I need to pass a IProgressMonitor as an argument to my methods. This is bad, for several reasons: The code gets cluttered with lots of code which is not relevant to what the function actually does. I need to manually guesstimate which parts of the code takes time, and which parts do not. It interacts badly with automated tests; where much of the information which goes into a progressbar instead should be logged for later inspection. Is there a way out of this? Are there tools which can help me out with one or more of these problems? Should I be looking at Aspect-Oriented Programming tools, or are there other alternatives?

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• What to do when blocked

  - by darkcminor

  I began to code different for 3 different projects, and it is alright, I have done it for 5 months, some php, some c, some matlab, but for some reason I got stucked... Usually when I pass through this I leave a while or go to sleep (and while sleeping I'm thinking on a solution to the problem I´m currently facing, the most important or urgent), and usually when I return (If I slept well) I have the solution and code comes easily, I don not know what you think, but I have like 10 consecutive days! I can't get out of the hole, I only see how time is going... What do you do when you lose the inspiration (I know leave it a while works), I mean, when all seems like it is not working, no matter what you do. Some friends say Go get some air, do sports, well I have tried... I know lot of you have passed this stage but How...

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• Graphical Mode breaks after suspend/ returning from Console

  - by Jack G

  When I try to go to a virtual console (ctrl alt f1) and return to f7, my screen freaks out. Its black with frequent white 'lightning bolts' flashing across the screen. Nothing works, but to force shutdown. Same when trying to resume from suspend. This doesnt happen every time, but very often. I dont know what information might be useful but: Ubuntu 12.10 ATI RS880M [Mobility Radeon HD 4200 Series] Gallium 0.4 on AMD RS880 this line in xsession-errors might be pertinent: (gnome-settings-daemon:1825): color-plugin-WARNING **: Done switch to new account, reload devices p.s. Ive tried the fglrx drivers but need the legacy drivers as described here, but nothing past a black screen.

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• Predicted target location

  - by user3256944

  I'm having an issue with calculating the predicted linear angle a projectile needs to move in to intersect a moving enemy ship for my 2D game. I've tried following the document here, but what I've have come up with is simply awful. protected Vector2 GetPredictedPosition(float angleToEnemy, ShipCompartment origin, ShipCompartment target) { // Below obviously won't compile (document wants a Vector, not sure how to get that from a single float?) Vector2 velocity = target.Thrust - 25f; // Closing velocity (25 is example projectile velocity) Vector2 distance = target.Position - origin.Position; // Range to close double time = distance.Length() / velocity.Length(); // Time // Garbage code, doesn't compile, this method is incorrect return target.Position + (target.Thrust * time); } I would be grateful if the community can help point out how this is done correctly.

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• Results stored in a session - good idea?

  - by Nick

  To give a bit of background, lets say it's a generic results page, which is paginated so there are X results per page. Generally to do this, I have two queries on the page: to get the total number of results to get the results, limiting by the correct page's resultset However, recently I've been trying to cut down on the queries the site is making, and I thought one way to do this would be to only do the query if any parameters to the page have changed (except of course the page number)? This would then cache all the result id's in a session, which can be sliced when I need to return the correct resultset for that page. I was trying to look around the net to see if there are downsides of this method, but I've found very little information about it. Has anyone done this before? Is it a good idea?

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• Override a static library's global function

  - by Jason Madux

  Not sure if this question belongs here or on SO, but posting here for now :) I'm trying to override a global function defined in "StaticLib" for my iOS application but the compiler keeps giving me the duplicate symbol error. Relevant code: #import "MyApplication.h" #import "StaticLib.h" NSData* getAllData() { NSLog(@"myGetAllData"); return nil; } @implementation MyApplication ... @end I've looked into Apple's runtime library but that all seems to be class-oriented. Any suggestions or is it just not possible to override global functions from static libraries?

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• Music player that uses an alarm function with multiple time settings

  - by Mat

  I have tried many different players searching for one with a specific feature that I would think would be easy. Simply, I want to play MP3 primarily. I would like to play a radio stream on Thursdays from 11:00 am until 12:00 pm, then return to playing MP3. Also, because I am in the Husker state, I would like to program another stream to start at game time on Saturdays and end several hours later, resuming my MP3 play until 11:00 am Thursday. Does anyone have a simple solution for me?

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• Best method in PHP for the Error Handling ? Convert all PHP errors (warnings notices etc) to exceptions?

  - by user1179459

  What is the best method in PHP for the Error Handling ? is there a way in PHP to Convert all PHP errors (warnings notices etc) to exceptions ? what the best way/practise to error handling ? again: if we overuse exceptions (i.e. try/catch) in many situations, i think application will be halted unnecessary. for a simple error checking we can use return false; but it may be cluttering the coding with many if else conditions. what do you guys suggest ?

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• Performance Driven Manufacturing

  Manufacturers are searching for new, creative ways to address growing demands of global manufacturing. They want the latest tools and technologies to boost performance from their operations, suppliers, partners, distributors, and extended ecosystem, and they need global views for better visibility - both internally and across the extended supply chain. In addition, operations must move information more effectively to gain real-time insight into manufacturing shop floor status. Whether it's inside the plant or outside the traditional factory walls, manufacturers are searching for solutions to help them produce more for less, lower their total cost of ownership (TCO), and improve their return on investment (ROI).

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• Flowchart with subroutine

  - by Jordy

  I am not really sure how to correctly describe my question, so please forgive me if this is a duplicate. I am creating a flowchart for my program where I implement a method. Let's assume I call this method someMethod. The C code could look something like this: bool someMethod(int Foo, int Bar) { foo += 5; bar -= 5; return (foo == bar); } This means that my flowchart will have a subroutine block where I call this function. But how do I correctly show the reader which integers I pass? And when I create the flowchart of "someMethod", I face a similar problem: how do I correctly show the reader that Foo and Bar are passed parameters?

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• Alps touchpad detected as a mouse, can't enable/disable multitouch

  - by Shota Bakuradze

  Now I know that this has been asked several times here but I couldn't find any decent solution to it. I am running Ubuntu 12.04 on my DELL N5110 and my touchpad is detected as a mouse, So I don't have the touchpad options availiable. Can't use multitouch and can't disable it either. I have tried the dkms driver from this link. But when I tried to install it with dpkg -i command, dpkg returns the following error: ERROR (dkms apport): unable to determine source package for psmouse-alps-dkms Error! Bad return status for module build on kernel: 3.2.0-25-generic-pae (i686) Consult /var/lib/dkms/psmouse-alps/0.10/build/make.log for more information. I have installed all the updates as well. Can someone help me out with this issue?

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