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• Experiences with (free) embedded TCP / IP stacks?

  - by Dan

  Does anyone have especially good (or bad) experiences with any of the following embedded TCP / IP stacks? uIP lwIP Bentham's TCP/IP Lean implementation The TCP/IP stack from this book My needs are for a solid, easy-to-port stack. Code size isn't terribly important, performance is relatively important, but ease of use & porting is very important. The system will probably use an RTOS, that hasn't been decided, but in my experience most stacks can be used with or without an RTOS. Most likely the platform will be an ARM variant (ARM7 or CM3 in all likelihood). Not too concerned about bolting the stack to the Ethernet driver, so that isn't a big priority in the selection. I'm not terribly interested in extracting a stack out of an OS, such as Linux, RTEMS, etc. I'm also not interested in commercial offerings such as Interniche, Micrium, etc... The stack doesn't need all sorts of bells & whistles, doesn't need IPv6, and I don't need any stuff on top of it (web servers, FTP servers, etc..) In fact it's possible that I'll only use UDP, although I can envision a couple scenarios where TCP would be preferable. Experiences with other stacks I've missed are of course also very much of interest. Thanks for your time & input.

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• Java: Cleaning up what causes a connection reset

  - by Zombies

  There seems to be some confusion as well contradicting statements on various SO answers: http://stackoverflow.com/questions/585599/whats-causing-my-java-net-socketexception-connection-reset . You can see here that the accepted answer states that the connection was closed by other side. But this is not true, closing a connection doesn't cause a connection reset. It is cauesed by "an underlying TCP/IP error." What I want to know is if a SocketException: Connection reset means really besides "unerlying TCP/IP Error." What really causes this? As I doubt it has anything to do with the connection being closed (since closing a connection isn't an exception worthy flag, and reading from a closed connection is, but that isn't an "underlying TCP/IP error." My hypothesis is this Connection reset is caused from a server's failure to acknowledge an ACK packet (either wholly or just improperly as per TCP/IP). And that a SocketTimeoutException is generated only when no data is generated to be read (since this is thrown during a read after a certain duration, and read is waiting for data, but is not concerned with ACK packets). In other words, read() throws SocketTimeoutException if it didn't read any bytes of actual data (DATA LAYER) in its allotted time.

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• Design: Website calling a webservice on the same machine

  - by Chris L

  More of a design/conceptual question. At work the decision was made to have our data access layer be called through webservices. So our website would call the webservices for any/all data to and from the database. Both the website & the webservices will be on the same machine(so no trip across the wire), but the database is on a separate machine(so that would require a trip across the wire regardless). This is all in-house, the website, webservice, and database are all within the same company(AFAIK, the webservices won't be reused by another other party). To the best of my knowledge: the website will open a port to the webservices, and the webservices will in turn open another port and go across the wire to the database server to get/submit the data. The trip across the wire can't be avoided, but I'm concerned about the webservices standing in the middle. I do agree there needs to be distinct layers between the functionality(such as business layer, data access layer, etc...), but this seems overly complex to me. I'm also sensing there will be some performance problems down the line. Seems to me it would be better to have the (DAL)assemblies referenced directly within the solution, thus negating the first port to port connection. Any thoughts(or links) both for and against this idea would be appreciated P.S. We're a .NET shop(migrating from vb to C# 3.5)

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• Automatically install and launch a code-signed application from Safari

  - by Thomas Jung

  Is it possible and if so what are the steps necessary to package (or build) a Mac OS X application and code-sign it so that it can be downloaded with Safari and automatically launch? ... possibly after the user responds to some sort of dialog explaining that it is a signed application and the publisher has been verified. An example of the user experience I am trying to create is "installing Google Chrome for the first time on Windows", which is a 3-click, less-than-a-minute process. For the concerned among you: I am not trying to create a drive-by download. I am fine with some sort of intermittent user step approving the download. I just want to make the installation as quick and painless as possible and not require the user drag the app from a mounted DMG into the application folder. This may not 100% jibe with established Mac OS X user interaction guidelines, but it would work better for the not-power users. I only need the high-level steps or pointers to resources ... my google-fu was weak on this one.

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• Can someone look over the curriculum for this major & give me your thoughts? Computing & Security Te

  - by scottsharpejr

  My goal is to become a good web developer. I'm interested in learning how to build complex websites as well as how to write web applications. I want skills that will enable me to write apps for <--insert hottest web trend here-- (Facebook & iphone apps for example) This is one of my goals as far as Tech. is concerned. I'd also like to have a brod knowledge of different areas of IT. I'm looking into majoring in "Computing & Security Technology". The program is offered by Drexel in conjunction with my CC. It's a 4 year degree. Can someone take a look @ the pdf below. It outlines every course I must take. http://www.drexelatbcc.org/academics/PDF/CST_CT.pdf For degree requirments w/ links to course descriptiongs see drexel.edu/catalog/degree/ct.htm With electives I can go up to Web Development 4. Based on my goals of Web development & wanting a well rounding education in information technology, what do you think of the curriculum? How will I fare entering the job market with this degree? My goals here are a little different. I'd like to work for 2 to 3 companies over the course of 6-7 years. Working with and learning different areas of IT. I'd like to stay with a company an average of 2-3 years before moving on. My end goal is to go into business for myself (IT related). I appreciate any and all advice the community here can give me! :) Could someone also explain to me their interpretation of this major? thanks! P.S. I already know XHTML & CSS. I am just now starting to experiment with PHP.

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• PostgreSQL: BYTEA vs OID+Large Object?

  - by mlaverd

  I started an application with Hibernate 3.2 and PostgreSQL 8.4. I have some byte[] fields that were mapped as @Basic (= PG bytea) and others that got mapped as @Lob (=PG Large Object). Why the inconsistency? Because I was a Hibernate noob. Now, those fields are max 4 Kb (but average is 2-3 kb). The PostgreSQL documentation mentioned that the LOs are good when the fields are big, but I didn't see what 'big' meant. I have upgraded to PostgreSQL 9.0 with Hibernate 3.6 and I was stuck to change the annotation to @Type(type="org.hibernate.type.PrimitiveByteArrayBlobType"). This bug has brought forward a potential compatibility issue, and I eventually found out that Large Objects are a pain to deal with, compared to a normal field. So I am thinking of changing all of it to bytea. But I am concerned that bytea fields are encoded in Hex, so there is some overhead in encoding and decoding, and this would hurt the performance. Are there good benchmarks about the performance of both of these? Anybody has made the switch and saw a difference?

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• Advice on improving programming skills, learning capabilities?

  - by anonymous-coward1234

  Hi all, After 2,5 years of professional Java programing, I still have problems that make my job difficult and, more importantly - more times that I would like to admit - not enjoyable. I would like to ask for advice by more experienced people on ways that would help me overcome them. These are the problems I have: I do not absorb new knowledge easily. Even when I understand something, after a couple of days I easily forget even basic stuff. Other co-workers, even with the same working experience, when reading new technologies put things easily into "context", and are able to compare in "real time| similar technologies they already have used. I always try to address all the issues to whatever I am doing at one go, which results in me trying to resolve too many problems at the same time, losing completely control. I find it difficult to make my mind on a single problem that I should address first, and even when I do, and find myself throwing away code that I wrote because I started addressing the wrong issue first. As far as architecture and data modeling is concerned, I have difficulty making decisions on what objects must be created, with what hierarchy, interfaces, abstraction etc. I imagine that - to a certain degree - these things come with experience. But after 2,5 years of Java programming, I would expect myself to have come much farther that I have come, both in terms of absorption and experience. Is there a way to improve my learning speed? Any books, methods, advice is welcome.

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• zend_captcha always fails isValid()

  - by Grant Collins

  Hi, I've got an issue with Zend_Captcha always returning false when the page is submitted and the captcha's isValid() method is being called. It's driving my nuts because this as far as I am concerned should work. I start by declaring this at the top of the action function of the controller $captcha = new Zend_Captcha_Image('captcha', array( 'captcha' => array( 'name' => 'graduatesignupcaptcha', 'wordlen' => 6, 'font' => $this->config->captcha->font, 'imgDir' => $baseUrl.'/images/captcha/', 'imgUrl' => $this->config->webserver->name.'/images/captcha/', ) ) ); $captcha->setHeight(80) ->setTimeout(300); I do usual form validation and that all works, however it is when I come to validate that the value entered into form for the captcha it always returns false. //next we check the captcha text to ensure that the form is a person not a script $captchaText = $form->getElement('captchainput')->getValue(); $captchaId = $form->getElement('captchaid')->getValue(); //$captchaSession = new Zend_Session_Namespace('Zend_Form_Captcha_'.$captchaId); $captchaArray = array( 'id' => $captchaId, 'input' => $captchaText ); if(!$captcha->isValid($captchaArray)){ $log->log(implode(",",$captcha->getErrors()), Zend_Log::DEBUG); $form->getElement('captchainput')->setErrors(array('messages' => 'Bad security code')); $formFailed = true; } I've check to ensure that the id that I am getting and storing as a hidden element in my form match the image that is being generated but no matter what I do this always fails. Am I missing something simple here?? Or is there a better way of dealing with this?? Thanks,

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• Accessing Static Methods on a Generic class in c#

  - by mrlane

  Hello, I have the following situation in code, which I suspect may be a bit dodgey: I have a class: abstract class DataAccessBase<T> : IDataAccess where T : AnotherAbstractClass This class DataAccessBase also has a static factory method which creates instances of derived classes of itself using an enum value in a which statement to decide which derived type to create: static IDataAccess CreateInstance(TypeToCreateEnum) Now, the types derived from DataAccessBase<T> are themselves NOT generic, they specify a type for T: class PoLcZoneData : DataAccessBase<PoLcZone> // PoLcZone is derived from AnotherAbstractClass So far I am not sure if this is pushing the limits of good use of generics, but what I am really concerned about is how to access the static CreateInstance() method in the first place: The way I am doing this at the moment is to simply pass any type T where T : AnotherAbstractClass. In particular I am passing AnotherAbstractClass itself. This allows compilation just fine, but it does seem to me that passing any type to a generic class just to get at the statics is a bit dodgey. I have actually simplified the situation somewhat as DataAccessBase<T> is the lower level in the inheritance chain, but the static factory methods exists in a middle tier with classes such as PoLcZoneData being the most derived on the only level that is not generic. What are peoples thoughts on this arrangement?

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• Object created in Interface Builder getting dealloc'ed too soon

  - by Collin Allen

  The Project I'm working on a relatively simple iPhone OS project that's navigation controller based, with a root table view and a detail table view. Tap an item in the main list to see its details in a pushed table view. The Setup I broke out the data source for both views into their own objects so as not to muddy the purpose of a view controller. Having done this, the table views no longer have data sources since those methods are now in separate files, so I created an instance of each data source class in the appropriate XIB files with the Object item (dragged it in, then set its class). Then, to actually connect the tableviews to their data sources, I set the dataSource outlet of each tableview to the yellow data source object in Interface Builder. The table view delegates are still set to their view controllers. The Problem The root table view works just fine, but when you tap a row to push to the detail view, the data source object gets instantiated as expected, then immediately dealloc'ed, causing a crash (numberOfSectionsInTableView: gets called on the freed object). I can't figure out why the data source is getting automatically dealloc-ed when I need it right then and there for the detail view, as indicated by my data source object creation and tableview connection in Interface Builder. What's more perplexing is that the very approach works fine for the root tableview! The Question Is there anything obvious I'm missing that would cause this to happen? Or, is this even the right way to instantiate a data source for a table view controller? It seems like poor object oriented programming to do it from within the view controller, which should only be concerned with the view. I could cram everything in two table view controller classes and it would probably work, but it would not be as modular as I'd like. Thanks!

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• Documentation and Build system for Mono/C#

  - by dcolish

  I'm starting out on a new project and a team member has decided to use C# as the implementation language. I don't have a lot of experience in C#, but a brief reading shows that it's very capable of being a complete cross-platform vm. Beyond the language, I've been having trouble selecting tools and workflows for managing the code as the project grows. It should be fairly small (<10K lines) but I would like to have the ability to generate documentation as the project grows, manage any external dependencies that we decide to use, and automate builds and testing. I am wondering what tools are commonly used or considered best practices for this language. I am mainly concerned with how would a build system potentially work on *nix as well as windows? Are there C# specific tools or is Make more common? In addition, I'd like to use a dvcs, but it doesn't look like Visual Studio and MonoDevelop support the same ones. What's the common vcs of choice for C#? For testing sort of Unit testing is available for C#/Mono? Finally, I know that there are good doc generators, but with the question of the build system, I would really like to have that just be a single step in the build similar to how testing is a step. Normally I'd automate with Hudson, but I am wondering if there is something more specific to the platform. Overall, I'd love to see a solution that provides a decent workflow on both windows and *nix without a heavy admin burden. I am pretty sure this is the holy grail of project management, so anything that puts me on that path is awesome.

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• Ember model is gone when I use the renderTemplate hook

  - by Mickael Caruso

  I have a single template - editPerson.hbs <form role="form"> FirstName: {{input type="text" value=model.firstName }} <br/> LastName: {{input type="text" value=model.lastName }} </form> I want to render this template when the user wants to edit an existing person or create a new person. So, I set up routes: App.Router.map(function(){ this.route("createPerson", { path: "/person/new" }); this.route("editPerson", { path: "/person/:id}); // other routes not show for brevity }); So, I define two routes - one for create and one for edit: App.CreatePersonRoute = Ember.Route.extend({ renderTemplate: function(){ this.render("editPerson", { controller: "editPerson" }); }, model: function(){ return {firstName: "John", lastName: "Smith" }; } }); App.EditPersonRoute = Ember.Route.extend({ model: function(id){ return {firstName: "John Existing", lastName: "Smith Existing" }; } }); So, I hard-code the models. I'm concerned about the createPerson route. I'm telling it to render the editPersonTemplate and to use the editPerson controller (which I don't show because I don't think it matters - but I made one, though.) When I use renderTemplate, I lose the model John Smith, which in turn, won't display on the editTemplate on the web page. Why? I "fixed" this by creating a separate and identical (to editPerson.hbs) createPerson.hbs, and removing the renderTemplate hook in the CreatePerson. It works as expected, but I find it somewhat troubling to have a separate and identical template for the edit and create cases. I looked everywhere for how to properly do this, and I found no answers.

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• Grouped UITableView Footer Sometimes Hidden On Quick Scroll

  - by jdandrea

  OK, this one is a puzzler. There is one similar post but it's not similar enough to count, so I'm posting this one. :) I've got a grouped UITableView with a header and footer. The footer includes two UIButton views, side-by-side. Nothing major. Now … there is a toggle button in a UIToolbar at the bottom for more/less info in this table view. So I build my index paths to delete/insert with fade row animation, all the usual ingredients, sandwiched between beginUpdates and endUpdates calls on the UITableView … and this works fine! In also happens that my footer can sometimes be pushed off past the bottom of the display. Here's where it gets weird. If I drag my finger up the display, scrolling the view upward, I should see that footer eventually, right? Well … most of the time I do. BUT, if I flick my finger up, for a faster scroll, the footer is missing. Even if you try to tap in that area - no response. However, if I scroll back down again, just to hide that footer (or rather hide the area where the footer would normally be), and then scroll back up, it's there once again! This only happens when inserting rows. If I delete rows, the footer stays put … unless of course it was already hidden and I didn't perform the aforementioned incantation to get it back. :) I am trying to trace through this, but to no avail. I suppose tracing through scroll operations is a bit of a crazy proposition! Perhaps some creative logging … suggestions, anyone? Or is this a known issue in 3.1 where row insert/deletes are concerned? (I don't recall seeing it until 3.1.)

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• Maintaining state and data context between requests in ASP.NET + EF4

  - by Nick

  I have a EF4/ASP.NET web application that is structured to use POCOs and generic repositories, based essentially on this excellent article. The application is relatively sophisticated with one page that involves selection and linking of multiple entities to build up a complex user profile. This requires access to multiple entity types (20 or so) and associated repositories across multiple posts. When a repository is first accessed it uses the existing data context if exists, else it creates a new context. The problem is that if the lifetime of the context is only per-request (as suggested in the article) then you have to deal with multiple contexts and the complexity around detaching and attaching entities from contexts. My solution is to share the context between posts by creating a single View Model that includes all required repositories (initialised to share the same context) plus any associated data and store this model in a Session variable, retrieving from Session on subsequent page requests. Therefore maintaining the same context across all posts until the profile is saved. This works fine BUT I am concerned that I don't actually know exactly what is stored in the model session variable or more importantly the size of the Session variable. So two questions I suppose: firstly should I look for a better solution to handle the shared context across posts issue (any suggestions welcome)? And secondly what is actually stored in the Session when it includes a repository plus context? Any help appreciated!

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• What is best practice (and implications) for packaging projects into JAR's?

  - by user245510

  What is considered best practice deciding how to define the set of JAR's for a project (for example a Swing GUI)? There are many possible groupings: JAR per layer (presentation, business, data) JAR per (significant?) GUI panel. For significant system, this results in a large number of JAR's, but the JAR's are (should be) more re-usable - fine-grained granularity JAR per "project" (in the sense of an IDE project); "common.jar", "resources.jar", "gui.jar", etc I am an experienced developer; I know the mechanics of creating JAR's, I'm just looking for wisdom on best-practice. Personally, I like the idea of a JAR per component (e.g. a panel), as I am mad-keen on encapsulation, and the holy-grail of re-use accross projects. I am concerned, however, that on a practical, performance level, the JVM would struggle class loading over dozens, maybe hundreds of small JAR's. Each JAR would contain; the GUI panel code, necessary resources (i.e. not centralised) so each panel can stand alone. Does anyone have wisdom to share?

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• How would I make a mouse controlled physics object in Box2D / AS3?

  - by Marty Wallace

  I recently created this tennis game using my own basic physics: http://martywallace.com/sandbox/tennis/ Basically a tennis racquet sticks to your mouse and you can hit the tennis balls upward. The physics aren't that great, and I want to make a more interesting version of this game with milestones and levels in Flash. I am planning to use Box2D because I have moderate experience with it. I'm not sure how to go about creating the racquet - as far as I understand Box2D, the racquet needs a velocity to influence the velocities of the balls when you hit them (so that you can hit them harder or softer upward to keep them up). With that said, I'm assuming I can't just have a kinematic body that will have its position set to the mouse, because it won't affect the velocities of the balls as expected. I've also thought about setting the velocity to the difference between the racquet position and the mouse each frame, but I am concerned that won't provide accurate positioning and am also thinking that the velocity could end up really large if you move the mouse quickly. What is the correct way to have a physics object locked to the mouse but also to have its displacement in the last frame (from where it was to the mouse) affect the balls?

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• How to convince someone, that reading programming related books(blogs, so..) is important? [closed]

  - by hgulyan

  Dear all, please, help me to convince, that no matter what you're doing, you need to read some stuff, try to learn something new. They say, that they don't want to sit in front of computer in the end of a day and they don't have opportunity to read in working hours, or they're too tired for doing something. Have you faced this kind of situation? What did you do? What if you want to help them? What methodology you'd suggest? How to open their eyes? EDIT I'm really concerned about this people. EDIT 2 Just to be clear, I'm not talking about one person or two. Some of them, just do their job good. Company doesn't motivate them to learn something. They're not bad people, not bad developers, they just need something or someone to help, show another view, but you can't just describe this new view or say smth like "You need to learn!" and that's it, you'll start to learn or you're not a good programmer. I started to learn OOP, DB structure 6 years ago and I had someone who had guided me. He told me to learn Java and MySQL, gave me some manuals and API's. That's how I started. What if they don't have that kind person or something else?

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• Programming test for ASP.NET C# developer job - Opinions please!

  - by Indy

  Hi all, We are hiring a .NET C# developer and I have developed a technical test for the candidates to complete. They have an hour and it has two parts, some knowledge based questions covering asp.net, C# and SQL and a small practical test. I'd appreciate feedback on the test, is it sufficient to test the programmers ability? What would you change if anything? Part One. What the are events fired as part of the ASP.NET Page lifecycle. What interesting things can you do at each? How does ViewState work and why is it either useful or bad? What is a common way to create web services in ASP.NET 2.0? What is the GAC? What is boxing? What is a delegate? The C# keyword .int. maps to which .NET type? Explain the difference between a Stored Procedure and a Trigger? What is an OUTER Join? What is @@IDENTITY? Part Two: You are provided with the Northwind Database and the attached DB relationship diagram. Please create a page which provides users with the following functionality. You don’t need to be too concerned with the presentation detail of the page. Select a customer from a list, and see all the orders placed by that customer. For the same customer, find all their orders which are Beverages and the quantity is more than 5. I was aware of setting the right balance of difficulty on this as there is an hour's test. I was able to complete the practical test in under 30 mins using SQLDatasource and the query designer in visual studio and the test questions, I am looking to see how they approach it logically and whether they use the tools available. Many thanks!

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• Is this a good KVO-compliant way to model a mutable to-many relationship?

  - by andyvn22

  Say I'd like a mutable, unordered to-many relationship. For internal optimization reasons, it'd be best to store this in an NSMutableDictionary rather than an NSMutableSet. But I'd like to keep that implementation detail private. I'd also like to provide some KVO-compliant accessors, so: - (NSSet*)things; - (NSUInteger)countOfThings; - (void)addThings:(NSSet*)someThings; - (void)removeThings:(NSSet*)someThings; Now, it'd be convenient and less evil to provide accessors (private ones, of course, in my implementation file) for the dictionary as well, so: @interface MYClassWithThings () @property (retain) NSMutableDictionary* keyedThings; @end This seems good to me! I can use accessors to mess with my keyedThings within the class, but other objects think they're dealing with a mutable, unordered (, unkeyed!) to-many relationship. I'm concerned that several things I'm doing may be "evil" though, according to good style and Apple approval and whatnot. Have I done anything evil here? (For example, is it wrong not to provide setThings, since the things property is supposedly mutable?)

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• SignalR - Handling disconnected users

  - by guilhermeGeek

  Hy, I'm using the signalR library on a project to handle an notification and chat modules. I've a table on an database to keep a track of online users. The HUB for chat is inheriting IDisconnect where i disconnect the user. After disconnecting the user, i warm the users about that event. At this point, i check if the disconnect user is the client. If it's, then i call an method on HUB to reconnect the user (just update the table). I do this because with the current implementation, once the user closes a tab on the browser it calls the Disconnect task but he could have another tab opened. I've not tested (with larger requests) this module yet, but on my development server it could take a few seconds between the IDisconnect event, and the request from the user to connect again. I'm concerned with my implementation to handle disconnected users from the chat but i can't see another way to improve this. If possible, could someone give me a advice on this, or this is the only solution that i've?

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• Validation with State Pattern for Multi-Page Forms in ASP.NET

  - by philrabin

  I'm trying to implement the state pattern for a multi-page registration form. The data on each page will be accumulated and stored in a session object. Should validation (including service layer calls to the DB) occur on the page level or inside each state class? In other words, should the concrete implementation of IState be concerned with the validation or should it be given a fully populated and valid object? See "EmptyFormState" class below: namespace Example { public class Registrar { private readonly IState formEmptyState; private readonly IState baseInformationComplete; public RegistrarSessionData RegistrarSessionData { get; set;} public Registrar() { RegistrarSessionData = new RegistrarSessionData(); formEmptyState = new EmptyFormState(this); baseInformationComplete = new BasicInfoCompleteState(this); State = formEmptyState; } public IState State { get; set; } public void SubmitData(RegistrarSessionData data) { State.SubmitData(data); } public void ProceedToNextStep() { State.ProceedToNextStep(); } } //actual data stored in the session //to be populated by page public class RegistrarSessionData { public string FirstName { get; set; } public string LastName { get; set; } //will include values of all 4 forms } //State Interface public interface IState { void SubmitData(RegistrarSessionData data); void ProceedToNextStep(); } //Concrete implementation of IState //Beginning state - no data public class EmptyFormState : IState { private readonly Registrar registrar; public EmptyFormState(Registrar registrar) { this.registrar = registrar; } public void SubmitData(RegistrarSessionData data) { //Should Validation occur here? //Should each state object contain a validation class? (IValidator ?) //Should this throw an exception? } public void ProceedToNextStep() { registrar.State = new BasicInfoCompleteState(registrar); } } //Next step, will have 4 in total public class BasicInfoCompleteState : IState { private readonly Registrar registrar; public BasicInfoCompleteState(Registrar registrar) { this.registrar = registrar; } public void SubmitData(RegistrarSessionData data) { //etc } public void ProceedToNextStep() { //etc } } }

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• Which linear programming package should I use for high numbers of constraints and "warm starts"

  - by davidsd

  I have a "continuous" linear programming problem that involves maximizing a linear function over a curved convex space. In typical LP problems, the convex space is a polytope, but in this case the convex space is piecewise curved -- that is, it has faces, edges, and vertices, but the edges aren't straight and the faces aren't flat. Instead of being specified by a finite number of linear inequalities, I have a continuously infinite number. I'm currently dealing with this by approximating the surface by a polytope, which means discretizing the continuously infinite constraints into a very large finite number of constraints. I'm also in the situation where I'd like to know how the answer changes under small perturbations to the underlying problem. Thus, I'd like to be able to supply an initial condition to the solver based on a nearby solution. I believe this capability is called a "warm start." Can someone help me distinguish between the various LP packages out there? I'm not so concerned with user-friendliness as speed (for large numbers of constraints), high-precision arithmetic, and warm starts. Thanks!

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• Default template parameters with forward declaration

  - by Seth Johnson

  Is it possible to forward declare a class that uses default arguments without specifying or knowing those arguments? For example, I would like to declare a boost::ptr_list< TYPE > in a Traits class without dragging the entire Boost library into every file that includes the traits. I would like to declare namespace boost { template<class T> class ptr_list< T >; }, but that doesn't work because it doesn't exactly match the true class declaration: template < class T, class CloneAllocator = heap_clone_allocator, class Allocator = std::allocator<void*> > class ptr_list { ... }; Are my options only to live with it or to specify boost::ptr_list< TYPE, boost::heap_clone_allocator, std::allocator<void*> in my traits class? (If I use the latter, I'll also have to forward declare boost::heap_clone_allocator and include <memory>, I suppose.) I've looked through Stroustrup's book, SO, and the rest of the internet and haven't found a solution. Usually people are concerned about not including STL, and the solution is "just include the STL headers." However, Boost is a much more massive and compiler-intensive library, so I'd prefer to leave it out unless I absolutely have to.

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• Algorithm To Select Most Popular Places from Database

  - by Russell C.

  We have a website that contains a database of places. For each place our users are able to take one of the follow actions which we record: VIEW - View it's profile RATING - Rate it on a scale of 1-5 stars REVIEW - Review it COMPLETED - Mark that they've been there WISH LIST - Mark that they want to go there FAVORITE - Mark that it's one of their favorites In our database table of places each place contains a count of the number of times each action above was taken as well as the average rating given by users. views ratings avg_rating completed wishlist favorite What we want to be able to do is generate lists of the top places using the above information. Ideally, we would want to be able to generate this list using a relatively simple SQL query without needing to do any legwork to calculate additional fields or stack rank places against one another. That being said, since we only have about 50,000 places we could run a nightly cron job to calculate some fields such as rankings on different categories if it would make a meaningful difference in the overall results of our top places. I'd appreciate if you could make some suggestions on how we should think about bubbling the best places to the top, which criteria we should weight more heavily, and given that information - suggest what the MySQL query would need to look like in order to select the top 10 places. One thing to note is that at this time we are less concerned with the recency of a place being popular - meaning that looking at the aggregate information is fine and that more recent data doesn't need to be weighted more heavily. Thanks in advance for your help & advice!

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• PHPUnit - multiple stubs of same class

  - by keithjgrant

  I'm building unit tests for class Foo, and I'm fairly new to unit testing. A key component of my class is an instance of BarCollection which contains a number of Bar objects. One method in Foo iterates through the collection and calls a couple methods on each Bar object in the collection. I want to use stub objects to generate a series of responses for my test class. How do I make the Bar stub class return different values as I iterate? I'm trying to do something along these lines: $stubs = array(); foreach ($array as $value) { $barStub->expects($this->any()) ->method('GetValue')) ->will($this->returnValue($value)); $stubs[] = $barStub; } // populate stubs into `Foo` // assert results from `Foo->someMethod()` So Foo->someMethod() will produce data based on the results it receives from the Bar objects. But this gives me the following error whenever the array is longer than one: There was 1 failure: 1) testMyTest(FooTest) with data set #2 (array(0.5, 0.5)) Expectation failed for method name is equal to <string:GetValue> when invoked zero or more times. Mocked method does not exist. /usr/share/php/PHPUnit/Framework/MockObject/Mock.php(193) : eval()'d code:25 One thought I had was to use ->will($this->returnCallback()) to invoke a callback method, but I don't know how to indicate to the callback which Bar object is making the call (and consequently what response to give). Another idea is to use the onConsecutiveCalls() method, or something like it, to tell my stub to return 1 the first time, 2 the second time, etc, but I'm not sure exactly how to do this. I'm also concerned that if my class ever does anything other than ordered iteration on the collection, I won't have a way to test it.

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