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• Distributed Lock Service over MySql/GigaSpaces/Netapp

  - by ripper234

  Disclaimer: I already asked this question, but without the deployment requirement. I got an answer that got 3 upvotes, and when I edited the question to include the deployment requirement the answer then became irrelevant. The reason I'm resubmitting is because SO considers the original question 'answered', even though I got no meaningful upvoted answer. I opened a uservoice submission about this problem. The reason I reposted is so StackOverflow consider the original question answered, so it doesn't show up on the 'unanswered questions' tab. Which distributed lock service would you use? Requirements are: A mutual exclusion (lock) that can be seen from different processes/machines lock...release semantics Automatic lock release after a certain timeout - if lock holder dies, it will automatically be freed after X seconds Java implementation Easy deployment - must not require complicated deployment beyond either Netapp, MySql or GigaSpaces. Must play well with those products (especially GigaSpaces - this is why TerraCotta was ruled out). Nice to have: .Net implementation If it's free: Deadlock detection / mitigation I'm not interested in answers like "it can be done over a database", or "it can be done over JavaSpaces" - I know. Relevant answers should only contain a ready, out-of-the-box, proven implementation.

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• Detecting a Dispose() from an exception inside using block

  - by Augusto Radtke

  I have the following code in my application: using (var database = new Database()) { var poll = // Some database query code. foreach (Question question in poll.Questions) { foreach (Answer answer in question.Answers) { database.Remove(answer); } // This is a sample line that simulate an error. throw new Exception("deu pau"); database.Remove(question); } database.Remove(poll); } This code triggers the Database class Dispose() method as usual, and this method automatically commits the transaction to the database, but this leaves my database in an inconsistent state as the answers are erased but the question and the poll are not. There is any way that I can detect in the Dispose() method that it being called because of an exception instead of regular end of the closing block, so I can automate the rollback? I don´t want to manually add a try ... catch block, my objective is to use the using block as a logical safe transaction manager, so it commits to the database if the execution was clean or rollbacks if any exception occured. Do you have some thoughts on that?

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• Is there a library that can decompile a method into an Expression tree, with support for CLR 4.0?

  - by Daniel Earwicker

  Previous questions have asked if it is possible to turn compiled delegates into expression trees, for example: http://stackoverflow.com/questions/767733/converting-a-net-funct-to-a-net-expressionfunct The sane answers at the time were: It's possible, but very hard and there's no standard library solution. Use Reflector! But fortunately there are some greatly-insane/insanely-great people out there who like reverse engineering things, and they make difficult things easy for the rest of us. Clearly it is possible to decompile IL to C#, as Reflector does it, and so you could in principle instead target CLR 4.0 expression trees with support for all statement types. This is interesting because it wouldn't matter if the compiler's built-in special support for Expression<> lambdas is never extended to support building statement expression trees in the compiler. A library solution could fill the gap. We would then have a high-level starting point for writing aspect-like manipulations of code without having to mess with raw IL. As noted in the answers to the above linked question, there are some promising signs but I haven't succeeded in finding if there's been much progress since by searching. So has anyone finished this job, or got very far with it? Note: CLR 4.0 is now released. Time for another look-see.

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• Interface Builder caching bad data (voodoo)

  - by Ryan Townshend

  Sometimes IB will hold onto old or bad references, and I cannot seem to remove or edit them. EDIT I have made this a wiki question with the intention of gathering more data on the phenomenon. Answers involving situations where other coders have encountered this are welcome. This happened to me again last night with a table controller. When I created a spike project to try and reproduce the error, the system worked the way I anticipated. Then back in the actual project the bad behavior continued, even if I remove the xib file and all controllers involved. Creating a whole new project with none of the original (problematic) xib and nib files worked correctly. This question is not about the specifics of this incident but about this type of incident in IB. Does anyone know more about this type of bad IB behaviour, and possibly a more stylish way to to eliminate it than nuking the project? Note, removing the offending IB files and recreating them in the same project has not solved this for me in the past, only whole new projects. Answers regarding examples of when/how this glitch has been observed/created are welcome as well.

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• Thread safe lazy contruction of a singleton in C++

  - by pauldoo

  Is there a way to implement a singleton object in C++ that is: Lazily constructed in a thread safe manner (two threads might simultaneously be the first user of the singleton - it should still only be constructed once). Doesn't rely on static variables being constructed beforehand (so the singleton object is itself safe to use during the construction of static variables). (I don't know my C++ well enough, but is it the case that integral and constant static variables are initialized before any code is executed (ie, even before static constructors are executed - their values may already be "initialized" in the program image)? If so - perhaps this can be exploited to implement a singleton mutex - which can in turn be used to guard the creation of the real singleton..) Excellent, it seems that I have a couple of good answers now (shame I can't mark 2 or 3 as being the answer). There appears to be two broad solutions: Use static initialisation (as opposed to dynamic initialisation) of a POD static varible, and implementing my own mutex with that using the builtin atomic instructions. This was the type of solution I was hinting at in my question, and I believe I knew already. Use some other library function like pthread_once or boost::call_once. These I certainly didn't know about - and am very grateful for the answers posted.

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• Problem with Railscast #197 - Nested Model Form Part 2

  - by sscirrus

  I'm trying to implement Ryan's Railscast #197 in a system with Questions, Answers, and (multiple choice) Options. http://railscasts.com/episodes/197-nested-model-form-part-2. I have successfully implemented the nesting among these forms/partials. The simpler 'check box' way to delete records works properly. The problem occurs when I try to add/delete records. I have copied the code exactly as it appears in his Railscast: #new.html.erb <%= javascript_include_tag :defaults, :cache => true %> <% f.fields_for :in_options do |builder| %> <%= render "option_fields", :f => builder %> <% end %> #_option_fields.html.erb partial <%= f.hidden_field :_destroy %> <%= link_to_function "remove", "remove_fields(this)" %> #application_helper.rb (exact same as #197) def link_to_remove_fields(name, f) f.hidden_field(:_destroy) + link_to_function(name, "remove_fields(this)") end def link_to_add_fields(name, f, association) new_object = f.object.class.reflect_on_association(association).klass.new fields = f.fields_for(association, new_object, :child_index => "new_#{association}") do |builder| render(association.to_s.singularize + "_fields", :f => builder) end link_to_function(name, h("add_fields(this, \"#{association}\", \"#{escape_javascript(fields)}\")")) end #application.js (exact same as #197. I have an Event.addbehavior below this code.) function remove_fields(link) { $(link).previous("input[type=hidden]").value = "1"; $(link).up(".fields").hide(); } function add_fields(link, association, content) { var new_id = new Date().getTime(); var regexp = new RegExp("new_" + association, "g") $(link).up().insert({ before: content.replace(regexp, new_id) }); } 2 problems: When I click on the 'remove' link it doesn't remove - it just shifts the page up or down. When I include link_to_add_fields "Add Answer", f, :answers, I get undefined method `klass' for nil:NilClass. Thanks everyone.

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• C# internal VS VBNET Friend

  - by Will Marcouiller

  To this SO question: What is the C# equivalent of friend?, I would personally have answered "internal", just like Ja did among the answers! However, Jon Skeet says that there is no direct equivalence of VB Friend in C#. If Jon Skeet says so, I won't be the one telling otherwise! ;P I'm wondering how can the keyword internal (C#) not be the equivalent of Friend (VBNET) when their respective definitions are: Friend VBNET The Friend (Visual Basic) keyword in the declaration statement specifies that the elements can be accessed from within the same assembly, but not from outside the assembly. [...] internal C# Internal: Access is limited to the current assembly. To my understanding, these definitions mean quite the same to me. Then, respectively, when I'm coding in VB.NET, I use the Friend keyword to specify that a class or a property shall be accessible only within the assembly where it is declared. The same in C#, I use the internal keyword to specify the same. Am I doing something or anything wrong from this perspective? What are the refinements I don't get? Might someone please explain how or in what Friend and internal are not direct equivalences? Thanks in advance for any of your answers!

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• Search and highlight html - ignoring and maintaining tags

  - by Sleepwalker

  I am looking for a good way to highlight key words in a block of html with stripping the html tags. I can regex to search for key words within html tags, but I haven't found a great way to search across tags. For example, if the key word phrase is "not bound" I want to be able to make this <p>I am not<strong>bound to please thee</strong> with my answers.</p> become wrapped in highlight tags, without breaking the "strong" tag (and making the html invalid) and become: <p>I am <span class="highlight">not</span><strong><span class="highlight">bound</span> to please thee</strong> with my answers.</p> The main issue is maintaining the html as it is AND wrapping blocks of text with highlight tags. I need to maintain the original html. Otherwise I would strip the tags. The best solution to this that I can think of right now would entail making a copy of the html and placing counter tokens where each space occurs, then stripping all tags and search for matching phrases, then looking back to the original and the tokenized strings and figuring out where to start building the highlight tags, then start walking forward, starting and ending highlight spans as needed from the beginning of the match until the end. This seems like overkill. I would like to something more elegant if possible. The solution would be written in C# or perhaps javascript, depending.

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• NOT A DUPLICATE! VS2010 - How to automatically stop compile on first compile error

  - by Ben Robbins

  {rant}First I'd like to say that this IS NOT A DUPLICATE. I've asked this question previously but it got closed as a duplicate when it isn't. This question is SPECIFIC to VS 2010 and the answers to the so-called duplicate work in VS 2008 but not in VS 2010 (at least not for me or anyone I know). So before you go closing something as a duplicate how about you read the question carefully and try the answer for yourself and see if it actually works. Apologies for the rant but there is no obvious way to contact the SO police that closed the issue or get it reopened. {/rant} At work we have a C# solution with over 80 projects. In VS 2008 we use a macro to stop the compile as soon as a project in the solution fails to build (see this question for several options for VS 2005 & VS 2008: http://stackoverflow.com/questions/134796/how-to-automatically-stop-visual-c-build-at-first-compile-error). Is it possible to do the same in VS 2010? What we have found is that in VS 2010 the macros don't work (at least I couldn't get them to work) as it appears that the environment events don't fire in VS 2010. The default behaviour is to continue as far as possible and display a list of errors in the error window. I'm happy for it to stop either as soon as an error is encountered (file-level) or as soon as a project fails to build (project-level). Answers for VS 2010 only please. If the macros do work then a detailed explanation of how to configure them for VS 2010 would be appreciated. Thanks.

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• When to choose which machine learning classifier?

  - by LM

  Suppose I'm working on some classification problem. (Fraud detection and comment spam are two problems I'm working on right now, but I'm curious about any classification task in general.) How do I know which classifier I should use? (Decision tree, SVM, Bayesian, logistic regression, etc.) In which cases is one of them the "natural" first choice, and what are the principles for choosing that one? Examples of the type of answers I'm looking for (from Manning et al.'s "Introduction to Information Retrieval book": http://nlp.stanford.edu/IR-book/html/htmledition/choosing-what-kind-of-classifier-to-use-1.html): a. If your data is labeled, but you only have a limited amount, you should use a classifier with high bias (for example, Naive Bayes). [I'm guessing this is because a higher-bias classifier will have lower variance, which is good because of the small amount of data.] b. If you have a ton of data, then the classifier doesn't really matter so much, so you should probably just choose a classifier with good scalability. What are other guidelines? Even answers like "if you'll have to explain your model to some upper management person, then maybe you should use a decision tree, since the decision rules are fairly transparent" are good. I care less about implementation/library issues, though. Also, for a somewhat separate question, besides standard Bayesian classifiers, are there 'standard state-of-the-art' methods for comment spam detection (as opposed to email spam)? [Not sure if stackoverflow is the best place to ask this question, since it's more machine learning than actual programming -- if not, any suggestions for where else?]

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• DotNetNuke and Subversion guidelines

  - by David Stratton

  I've Googled, Binged, and here at StackOverflow, looked through the related questions and searched, but I'm not finding what I'm looking for. I've also searched documentation on DNN. What I'm looking for is any guidance (tutorials, blogs, step-by-step instructions for setting up a repository) etc from people who are experienced in using DotNetNuke with SVN. We use SVN for all our source control, and have no problem with standard applications, because we pretty much built the repository and directory structure to work with our processes. This means when we do web sites, in Visual Studio, we do file based web sites, rather than setting them up in the local IIS. It just makes things easier for us. However, with DNN, it appears that even if you get the source code, it is expecting to be set up in the local IIS, which means additional headaches for us. For example, we are moving all of our source code off our local C drives, and onto a shared drive on a server. This is to enable backups in addition to our normal source control. (This was a management decision). So that means that we need to change the virtual web app when we make the move. Has anyone come up with a good way to work around this? Can DNN be set up so that the developer web server in Visual Studio can be used, so that we can treat it just like any normal web app? Am I missing something obvious? Edit - added I'm willing to accept answers like "We tried it and never got it to work", and "It can't be done" as answers. I'm always open to hearing "It can't be done the way you want. You need to change your procedures to match how it works" if necessary. I guess if you've got experience trying this and just couldn't get it to work, I can learn from your experience that way as well, but some detail would be good.

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• How to create closed areas (convex polygons) from set of line segments ?

  - by Marten

  The following problem is in 2D, so some simplifications can be made when suggesting answers. I need to create closed areas (defined either by line segments or just set of points - convex polygon) from a set of points/line segments. Basically I used Voronoi to generate "roads". Then I changed some of the data. Now I need a way to loop through that data (which is still line segments but doesn't comply with Voronoi anymore) and generate "neigbourhoods" that are bordered with the "roads". I looked at some graph diagrams and shortest path theories, but I could not figure it out. Logically it could be done by starting at left edge from one point, finding the way back to that point using the shortest path with available lines (using only clockwise directions). Then mark this line set down and remove from the data. Then you can repeat the same process and get all the areas like that. I tried to implement that but it did not get me anywhere as I could not figure out a way to write a C++ code that could do that. Problem was with choosing the most counterclockwise line from available lines from a specific point. All angle based math I did gave wrong answers because the way sin/cos are implemented in c++. So to summarize - if you can help me with a totally new approach to the problem its good, if not could you help me find a way to write the part of the code that finds the shortest clockwise path back to the beginning point using the line segment set as paths back. Thank you for your help!

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• How are you using C++0x today? [closed]

  - by Roger Pate

  This is a question in two parts, the first is the most important and concerns now: Are you following the design and evolution of C++0x? What blogs, newsgroups, committee papers, and other resources do you follow? Even where you're not using any new features, how have they affected your current choices? What new features are you using now, either in production or otherwise? The second part is a follow-up, concerning the new standard once it is final: Do you expect to use it immediately? What are you doing to prepare for C++0x, other than as listed for the previous questions? Obviously, compiler support must be there, but there's still co-workers, ancillary tools, and other factors to consider. What will most affect your adoption? Edit: The original really was too argumentative; however, I'm still interested in the underlying question, so I've tried to clean it up and hopefully make it acceptable. This seems a much better avenue than duplicating—even though some answers responded to the argumentative tone, they still apply to the extent that they addressed the questions, and all answers are community property to be cleaned up as appropriate, too.

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• why MVC instead of good old asp.net? Still not grasping why I should go this route??

  - by RJ

  I know this question has been asked before and I read all the answers but they still don't give me the answers I am looking for. I need something concrete. I volunteered to give a presentation on MVC to other developers in our group which forces me to learn it. The big question everyone has is: "What can MVC bring to the table that we can't do in asp.net or MVC can do faster. I have just gone through Nerd Dinner and actually created a complete website that sort of mimics Nerd Dinner. But as great a job that Scott Guthrie did on it, there are big gaps that aren't answered such as, how do I throw a textbox on the listing page with a button and do a simple search. In asp.net, I would throw a textbox, button and grid on the page and bind it to a sproc and away I go. What is the equivalent in MVC. I guess I need a really good tutorial on how to use MVC without using Linq-to-Sql. I know I am sort of babbling on about this but it is a very serious question that still seems to go unanswered. On a side note, the View page of MVC brings back nightmares of classic asp with all the in-line code that we got away from way back when with code behind pages. Yes, MVC has Controller and Model classes which are great but I still don't like the classic asp tags in the html. Help me out here, I really like the concept of MVC and want it to be successful but I need more!

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• Is there any reason to use C instead of C++ for embedded development?

  - by Piotr Czapla

  Question I have two compilers on my hardware C++ and C89 I'm thinking about using C++ with classes but without polymorphism (to avoid vtables). The main reasons I’d like to use C++ are: I prefer to use “inline” functions instead of macro definitions. I’d like to use namespaces as I prefixes clutter the code. I see C++ a bit type safer mainly because of templates, and verbose casting. I really like overloaded functions and constructors (used for automatic casting). Do you see any reason to stick with C89 when developing for very limited hardware (4kb of RAM)? Conclusion Thank you for your answers, they were really helpful! I though the subject through and I will stick with C mainly because: It is easier to predict actual code in C and this is really important if you have only 4kb of ram. My team consists of C developers mainly so advance features of C++ won't be frequently used. I've found a way to inline functions in my C compiler (C89). It is hard to accept one answer as you provided so many good answers. Unfortunately I can't create a wiki and accept it so I will choose one answer that made me think most.

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• division with wrong result

  - by PeterK

  Hi, I am trying to divide integers but get 0 as result. I just do not understand what i am doing wrong. I am using only int's in this example but get the same result testing with float or double. The code i use is: int wrongAnswers = askedQuestions - playerResult; int percentCorrect = (playerResult / askedQuestions) * 100; int percentWrong = (wrongAnswers / askedQuestions) * 100; NSLog(@"askedQuestions: %i", askedQuestions); NSLog(@"playerResult: %i", playerResult); NSLog(@"wrongAnswers: %i", wrongAnswers); NSLog(@"percentCorrect: %i", percentCorrect); NSLog(@"percentWrong: %i", percentWrong); NSLog(@"calc: %i", (wrongAnswers + playerResult)); NSLog(@"wrong answers %: %i %%", ((wrongAnswers / askedQuestions) * 100)); The result i get is: 2011-01-09 16:45:53.411 XX[8296:207] askedQuestions: 5 2011-01-09 16:45:53.412 XX[8296:207] playerResult: 2 2011-01-09 16:45:53.412 XX[8296:207] wrongAnswers: 3 2011-01-09 16:45:53.413 XX[8296:207] percentCorrect: 0 % 2011-01-09 16:45:53.414 XX[8296:207] percentWrong: 0 % 2011-01-09 16:45:53.414 XX[8296:207] calc: 5 2011-01-09 16:45:53.415 XX[8296:207] wrong answers : 0 % I would very much appreciate help :-)

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• Use interface between model and view in ASP.NET MVC

  - by Icerman

  Hi, I am using asp.net MVC 2 to develop a site. IUser is used to be the interface between model and view for better separation of concern. However, things turn to a little messy here. In the controller that handles user sign on: I have the following: IUserBll userBll = new UserBll(); IUser newUser = new User(); newUser.Username = answers[0].ToString(); newUser.Email = answers[1].ToString(); userBll.AddUser(newUser); The User class is defined in web project as a concrete class implementing IUser. There is a similar class in DAL implementing the same interface and used to persist data. However, when the userBll.AddUser is called, the newUser of type User can't be casted to the DAL User class even though both Users class implementing the interface (InvalidCastException). Using conversion operators maybe an option, but it will make the dependency between DAL and web which is against the initial goal of using interface. Any suggestions?

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• Why doesn't java.util.Set have get(int index)?

  - by Marty Pitt

  I'm sure there's a good reason, but could someone please explain why the java.util.Set interface lacks get(int Index), or any similar get() method? It seems that sets are great for putting things into, but I can't find an elegant way of retrieving a single item from it. If I know I want the first item, I can use set.iterator().next(), but otherwise it seems I have to cast to an Array to retrieve an item at a specific index? What are the appropriate ways of retrieving data from a set? (other than using an iterator) I'm sure the fact that it's excluded from the API means there's a good reason for not doing this -- could someone please enlighten me? EDIT: Some extremely great answers here, and a few saying "more context". The specific scneario was a dbUnit test, where I could reasonalby assert that the returned set from a query had only 1 item, and I was trying to access that item. However, the question is more valid without the scenario, as it remains more focussed : What's the difference between set & list. Thanks to all for the fantastic answers below.

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• Navigating through code with keyboard shortcuts

  - by MarceloRamires

  I'm starting to feel the need to run fastly through code with keyboard shortcuts, to arrive faster where I want to make any changes (avoiding use of mouse or long times holding [up], [left], [right] and [down]). I'm already using some: [home] - first position in current line [end] - last position in current line [ctrl] + [home] - first line of the entire code [ctrl] + [end] - last line of the entire code [pageup] - same vertical position, one screen above [pagedown] - same vertical position, one screen below [ctrl] + [pageup] - first line in current screen [ctrl] + [end] - last line in current screen [ctrl] + [left/right] - skipping word per word What have you got ? I use Visual Studio. (but I'm open to any answer, as I maybe can use others soon) obs: I've searched through stackoverflow and didn't find a nice question with this content, nor a list of keyboard code searching. If it's repeated, I'm sorry for not finding it, I'm here in my best intentions. This question is NOT about any shortcuts, and not only about visual studio, it's about running through code with shortcuts. Answers that suit the question so far: [Ctrl] + [-] - jumps to last cursor position [Ctrl] + [F3] - Jumps to next occurance of the word the curson is in [Shift] + [F3] - Same as the above, backwards. [F12] - Goes to definition of method/variable the cursor is in [Ctrl] + [ ] ] - Jumps to matching brace and select I'll ad more as there are answers.

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• How can you ask a sensitive work question anonymously but still inform readers of your credibility a

  - by Rob

  I would like to request opinions about my career/situation at work with a software development project. I would like to ask anonymously or created a new stackoverflow.com account because I think I may be identified by co-workers at my employer since I have referred them to (non-sensititive) technical questions I have asked here. So they might know my account and be able to follow my activity. If I create a new account it will have no reputation and some readers may ignore it, for example, because they might think that the user only wishes to take ideas from here and not contribute, i.e. not a committed stackoverflow poster. What are your thoughts? (I do feel that it is appropriate to ask such pogramming career/situational questions here as many others have and there are some good questions -and answers and it seems that the stackoverflow community accepts such questions even thought the site's strict guidelines are for specific answers and not discussion, and non-subjective questions. And thank goodness that is the case - not all problems faced by programmers are about the craft but also the human factors around it - where else would folks go?)

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• Haskell Cons Operator (:)

  - by Carson Myers

  I am really new to Haskell (Actually I saw "Real World Haskell" from O'Reilly and thought "hmm, I think I'll learn functional programming" yesterday) and I am wondering: I can use the construct operator to add an item to the beginning of a list: 1 : [2,3] [1,2,3] I tried making an example data type I found in the book and then playing with it: --in a file data BillingInfo = CreditCard Int String String | CashOnDelivery | Invoice Int deriving (Show) --in ghci $ let order_list = [Invoice 2345] $ order_list [Invoice 2345] $ let order_list = CashOnDelivery : order_list $ order_list [CashOnDelivery, CashOnDelivery, CashOnDelivery, CashOnDelivery, CashOnDelivery, CashOnDelivery, CashOnDelivery, CashOnDelivery, CashOnDelivery, CashOnDelivery, CashOnDelivery, CashOnDelivery, CashOnDelivery, CashOnDelivery, ...- etc... it just repeats forever, is this because it uses lazy evaluation? -- EDIT -- okay, so it is being pounded into my head that let order_list = CashOnDelivery:order_list doesn't add CashOnDelivery to the original order_list and then set the result to order_list, but instead is recursive and creates an infinite list, forever adding CashOnDelivery to the beginning of itself. Of course now I remember that Haskell is a functional language and I can't change the value of the original order_list, so what should I do for a simple "tack this on to the end (or beginning, whatever) of this list?" Make a function which takes a list and BillingInfo as arguments, and then return a list? -- EDIT 2 -- well, based on all the answers I'm getting and the lack of being able to pass an object by reference and mutate variables (such as I'm used to)... I think that I have just asked this question prematurely and that I really need to delve further into the functional paradigm before I can expect to really understand the answers to my questions... I guess what i was looking for was how to write a function or something, taking a list and an item, and returning a list under the same name so the function could be called more than once, without changing the name every time (as if it was actually a program which would add actual orders to an order list, and the user wouldn't have to think of a new name for the list each time, but rather append an item to the same list).

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• Is learning C++ a good idea?

  - by chang

  The more I hear and read about C++ (e.g. this: http://lwn.net/Articles/249460/), I get the impression, that I'd waste my time learning C++. I some wrote network routing algorithm in C++ for a simulator, and it was a pain (as expected, especially coming from a perl/python/Java background ...). I'm never happy about giving up on some technology, but I would be happy, if I could limit my knowledge of C-family languages to just C, C# and Objective-C (even OS Xs Cocoa, which is huge and takes a lot of time to learn looks like joy compared to C++ ...). Do I need to consider myself dumb or unwilling, just because I'm not partial to the pain involved learning this stuff? Technologies advance and there will be options other than C++, when deciding on implementation languages, or not? And for speed: If speed were that critical, I'd go for a plain C implementation instead, or write C extensions for much more productive languages like ruby or python ... The one-line version of the above: Will C++ stay such a relevant language that every committed programmer should be familiar with it? [ edit / thank you very much for your interesting and useful answers so far .. ] [ edit / .. i am accepting the top-rated answer; thanks again for all answers! ]

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• Why does C# not provide the C++ style 'friend' keyword?

  - by Ash

  The C++ friend keyword allows a class A to designate class B as it's friend. This allows Class B to access the private/protected members of class A. I've never read anything as to why this was left out of C# (and VB.NET). Most answers to this earlier StackOverflow question seem to be saying it is a useful part of C++ and there are good reasons to use it. In my experience I'd have to agree. Another question seems to me to be really asking how to do something similar to friend in a C# application. While the answers generally revolve around nested classes, it doesn't seem quite as elegant as using the friend keyword. The original Design Patterns book uses the friend keyword regularly throughout its examples. So in summary, why is friend missing from C#, and what is the "best practice" way (or ways) of simulating it in C#? (By the way, the "internal" keyword is not the same thing, it allows ALL classes within the entire assembly to access internal members, friend allows you to give access to a class to just one other class.)

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• Still Confused About Identifying vs. Non-Identifying Relationships

  - by Jason

  So, I've been reading up on identifying vs. non-identifying relationships in my database design, and a number of the answers on SO seem contradicting to me. Here are the two questions I am looking at: What's the Difference Between Identifying and Non-Identifying Relationships Trouble Deciding on Identifying or Non-Identifying Relationship Looking at the top answers from each question, I appear to get two different ideas of what an identifying relationship is. The first question's response says that an identifying relationship "describes a situation in which the existence of a row in the child table depends on a row in the parent table." An example of this that is given is, "An author can write many books (1-to-n relationship), but a book cannot exist without an author." That makes sense to me. However, when I read the response to question two, I get confused as it says, "if a child identifies its parent, it is an identifying relationship." The answer then goes on to give examples such as SSN (is identifying of a Person), but an address is not (because many people can live at an address). To me, this sounds more like a case of the decision between primary key and non-primary key. My own gut feeling (and additional research on other sites) points to the first question and its response being correct. However, I wanted to verify before I continued forward as I don't want to learn something wrong as I am working to understand database design. Thanks in advance.

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• HOWTO: implement a jQuery version of ASP.Net MVC "Strongly Typed Partial Views"

  - by Sam Carleton

  I am working on a multi-page assessment form where the questions/responses are database driven. Currently I the basic system working with Html.BeginForm via standard ASP.Net MVC. At this point in time, the key to the whole system is the 'Strongly Typed Partial Views'. When the question/response is read from the database, the response type determines which derived model is created and added to the collection. The main view it iterates through the collection and uses the 'Strongly Typed Partial Views' system of ASP.Net MVC to determine which view to render the correct type of response (radio button, drop down, or text box). I would like to change this process from a Html.BeginForm to Ajax.BeginForm. The problem is I don't have a clue as to how to implement the dynamic creation of the question/response in the JavaScript/jQuery world. Any thoughts and/or suggestions? Here is the current code to generate the dynamic form: @using (Html.BeginForm(new { mdsId = @Model.MdsId, sectionId = @Model.SectionId })) { <div class="SectionTitle"> <span>Section @Model.SectionName - @Model.SectionDescription</span> <span style="float: right">@Html.CheckBoxFor(x => x.ShowUnansweredQuestions) Show only unaswered questions</span> </div> @Html.HiddenFor(x => x.PrevSectionId) @Html.HiddenFor(x => x.NextSectionId) for (var i = 0; i < Model.answers.Count(); i++) { @Html.EditorFor(m => m.answers[i]); } }

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