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• Choosing design method for ladder-like word game.

  - by owca

  I'm trying to build a simple application, with the finished program looking like this : I will also have to implement two different GUI layouts for this. Now I'm trying to figure out the best method to perform this task. My professor told me to introduce Element class with 4 states : - empty - invisible (used in GridLayout) - first letter - other letter I've thought about following solutions (by List I mean any sort of Collection) : 1. Element is a single letter, and each line is Element[]. Game class will be array of arrays Element[]. I guess that's the dumbest way, and the validation might be troublesome. 2. Like previously but Line is a List of Element. Game is an array of Lines. 3. Like previously but Game is a List of Lines. Which one should I choose ? Or maybe do you have better ideas ? What collection would be best if to use one ?

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• How to get components from a JFrame with a GridLayout?

  - by NlightNfotis

  I have a question about Java and JFrame in particular. Let's say I have a JFrame that I am using with a GridLayout. Supposing that I have added JButtons in the JFrame, how can I gain access to the one I want using it's position (by position, I mean a x and a y, used to define the exact place on the Grid). I have tried several methods, for instance getComponentAt(int x, int y), and have seen that those methods do not work as intended when combined with GridLayout, or at least don't work as intended in my case. So I tried using getComponent(), which seems fine. The latest method, that seems to be on a right track for me is (assuming I have a JFrame with a GridLayout with 7 rows and 7 columns, x as columns, y as rows): public JButton getButtonByXAndY(int x, int y) { return (JButton) this.getContentPane().getComponent((y-1) * 7 + x); } Using the above, say I want to get the JButton at (4, 4), meaning the 25th JButton in the JFrame, I would index through the first 21 buttons at first, and then add 4 more, finally accessing the JButton I want. Problem is this works like that in theory only. Any ideas? P.S sorry for linking to an external website, but stack overflow won't allow me to upload the image, because I do not have the required reputation.

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• Drawing an image in Java, slow as hell on a netbook.

  - by Norswap

  In follow-up to my previous questions (especially this one : http://stackoverflow.com/questions/2684123/java-volatileimage-slower-than-bufferedimage), i have noticed that simply drawing an Image (it doesn't matter if it's buffered or volatile, since the computer has no accelerated memory*, and tests shows it's doesn't change anything), tends to be very long. (*) System.out.println(GraphicsEnvironment.getLocalGraphicsEnvironment() .getDefaultScreenDevice().getAvailableAcceleratedMemory()); --> 0 How long ? For a 500x400 image, about 0.04 seconds. This is only drawing the image on the backbuffer (obtained via buffer strategy). Now considering that world of warcraft runs on that netbook (tough it is quite laggy) and that online java games seems to have no problem whatsoever, this is quite thought provoking. I'm quite certain I didn't miss something obvious, I've searched extensively the web, but nothing will do. So do any of you java whiz have an idea of what obscure problem might be causing this (or maybe it is normal, tough I doubt it) ? PS : As I'm writing this I realized this might be cause by my Linux installation (archlinux) tough I have the correct Intel driver. But my computer normally has "Integrated Intel Graphics Media Accelerator 950", which would mean it should have accelerated video memory somehow. Any ideas about this side of things ?

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• Are certain open-source licenses more suitable than others for career growth?

  - by Francisco Garcia

  As a software engineer/programmer myself, I love the possibility to download the code and learn from it. However building software is what brings food to my table. I have doubts regarding the type of license I should use for my own personal projects or when picking up one project to learn from. There are already many questions about licenses on Stackoverflow, but I would like to make this one much more specific. If your main profession and way of living is building software: which type of license do you find more useful for you? And I mean, the license that can benefit you most as a professional because it gives you more freedom to reuse the experience you gain. GPL is a great license to build communities because it forces you to give back your work. However I like BSD licenses because of their extra freedom. I know that if the code I am exploring is BSD licensed, I might be able to expand not only my skills, but also my programmer toolbox. Whenever I am working for a company, I might recall that something similar was done in another project and I will be able to copy or imitate certain part of the code. I know that there are religious wars regarding GPL vs BSD and it is not my intention to start one. Probably many companies already take snipsets from GPL projects anyway. I just want to insist in the factor of professional enrichment. I do not intend to discriminate any license. I said I prefer BSD licenses but I also use Linux because the user base is bigger and also the market demand.

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• How to start with entity framework and service oriented architecture?

  - by citronas

  At work I need to create a new web application, that will connection to an MySql Database. (So far I only have expercience with Linq-To-Sql classes and MSSQL Servers.) My superior tells me to use the entity framework (he probably refers to Linq-To-Entity) and provide everything as a service based architecture. Unfortunatly nobody at work has experience with that framework and with a real nice server oriented architecture. (till now no customer wanted to pay for architecture that he can't see. This speficic project I'm leading will be long-term, meaning multiple years, so it would be best to design it the way, that multiple targetting plattforms like asp.net, c# wpf, ... could use it) For now, the main target plattform is ASP.net So I do have the following questions: 1) Where can I read best what's really behind service oriented architecture (but for now beginner tutorials work fine as well) and how to do it in best practise? 2) So far I can't seem a real difference between Linq-To-Sql classes and the information I've google so far on the 'entity framework'. So, whats the difference? Where do I find nice tutorials for it. 3) Is there any difference in the entity framework regarding the database server (MSSQL or MySQL). If not, does that mean that code snipperts I will stumble across will word database independent? 4) I do you Visual Studio 2010. Do I have to regard something specific?

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• CSS Experts required - problems with Z-Index stack in my page design

  - by Jack W-H

  Howdy y'all! Basically I'm having some problems with Z-Index. Although I'm not amazing at CSS I would reckon I was reasonably good, but really can't work this out. You'll see at the URL... http://howcode.com/code/ ... that my problem is that links in the returned 'Popular' results aren't clickable or anything. I've concluded this is due to their Z-Index being messed up. I had to fiddle and tweak with Z-Index to get the tabs - Popular, Top Rated, Featured etc. - to show above the codebg div. When I adjusted the Z-Index so that the results were definitely on top, they acted as normal - text could be selected, the ratings images hovered, etc. etc. However the downside to this was that my Popular, Top Rated, Featured tabs were all placed BENEATH the background image for the returned results. If anyone can post a workaround or alteration to my CSS that would be much appreciated. Please don't forget this is a test site and design and any other URLs are likely not to work, I haven't uploaded any database configs yet or whatever! Attached are a couple of screenshots to clarify what I mean: This is what I WANT to happen (not that in actual fact in this screenshots link aren't clickable, just to demo my point though): This is what DOES happen when I adjust the Z-Index properties (I don't want this!): Thanks y'all!

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• DDD: Enum like entities

  - by Chris

  Hi all, I have the following DB model: **Person table** ID | Name | StateId ------------------------------ 1 Joe 1 2 Peter 1 3 John 2 **State table** ID | Desc ------------------------------ 1 Working 2 Vacation and domain model would be (simplified): public class Person { public int Id { get; } public string Name { get; set; } public State State { get; set; } } public class State { private int id; public string Name { get; set; } } The state might be used in the domain logic e.g.: if(person.State == State.Working) // some logic So from my understanding, the State acts like a value object which is used for domain logic checks. But it also needs to be present in the DB model to represent a clean ERM. So state might be extended to: public class State { private int id; public string Name { get; set; } public static State New {get {return new State([hardCodedIdHere?], [hardCodeNameHere?]);}} } But using this approach the name of the state would be hardcoded into the domain. Do you know what I mean? Is there a standard approach for such a thing? From my point of view what I am trying to do is using an object (which is persisted from the ERM design perspective) as a sort of value object within my domain. What do you think? Question update: Probably my question wasn't clear enough. What I need to know is, how I would use an entity (like the State example) that is stored in a database within my domain logic. To avoid things like: if(person.State.Id == State.Working.Id) // some logic or if(person.State.Id == WORKING_ID) // some logic

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• Do entity collections and object sets implement IQueryable<T>?

  - by Chevex

  I am using Entity Framework for the first time and noticed that the entities object returns entity collections. DBEntities db = new DBEntities(); db.Users; //Users is an ObjectSet<User> User user = db.Users.Where(x => x.Username == "test").First(); //Is this getting executed in the SQL or in memory? user.Posts; //Posts is an EntityCollection<Post> Post post = user.Posts.Where(x => x.PostID == "123").First(); //Is this getting executed in the SQL or in memory? Do both ObjectSet and EntityCollection implement IQueryable? I am hoping they do so that I know the queries are getting executed at the data source and not in memory. EDIT: So apparently EntityCollection does not while ObjectSet does. Does that mean I would be better off using this code? DBEntities db = new DBEntities(); User user = db.Users.Where(x => x.Username == "test").First(); //Is this getting executed in the SQL or in memory? Post post = db.Posts.Where(x => (x.PostID == "123")&&(x.Username == user.Username)).First(); // Querying the object set instead of the entity collection. Also, what is the difference between ObjectSet and EntityCollection? Shouldn't they be the same? Thanks in advance!

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• Quality of TFS 2008 merged code

  - by paologios

  Does the quality of code merged by TFS 2008 depend on the used programming language? I know merging in Java / Subversion, and merging a branch to its trunk usually does not create much conflicts. Now in my company, we use VB.NET. When I merge two files TFS does not always get code blocks right, e.g. does not find the right If..then / end if lines. To give you an example, I mean: File 2 is created as a branch of File 1. Both files were changed later, now I'm going to merge those files and am recieving conficts: The marked end-if lines (1) are detected as corresponding, meaning the added event handler Button1_Click is being deleted. Now I wonder if this behavior is by language (C# vs. VB.NET) or are other source control solutions just better than TFS? (And I really liked TFS up to now :) ) File 1: Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load If Not Page.IsPostBack Then Label1.Text = "Hello" Label2.Text = "World" End If End Sub Protected Sub Button2_Click(ByVal sender, ByVal e as System.EventArgs) Handles Button2.Click // .... If Page.IsValid Then Label3.Text = "Hello Button 2" End If // .... End Sub File 2 (Branch of File 1): Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load If Not Page.IsPostBack Then fillTableFromDatabase() End If // (1) End Sub Protected Sub Button1_Click(ByVal sender, ByVal e as System.EventArgs) Handles Button1.Click // do something here End Sub Protected Sub Button2_Click(ByVal sender, ByVal e as System.EventArgs) Handles Button2.Click // .... If Page.IsValid Then End If // (1) // .... End Sub

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• To OpenID or not to OpenID? Is it worth it?

  - by Eloff

  Does OpenID improve the user experience? Edit Not to detract from the other comments, but I got one really good reply below that outlined 3 advantages of OpenID in a rational bottom line kind of way. I've also heard some whisperings in other comments that you can get access to some details on the user through OpenID (name? email? what?) and that using that it might even be able to simplify the registration process by not needing to gather as much information. Things that definitely need to be gathered in a checkout process: Full name Email (I'm pretty sure I'll have to ask for these myself) Billing address Shipping address Credit card info There may be a few other things that are interesting from a marketing point of view, but I wouldn't ask the user to manually enter anything not absolutely required during the checkout process. So what's possible in this regard? /Edit (You may have noticed stackoverflow uses OpenID) It seems to me it is easier and faster for the user to simply enter a username and password in a signup form they have to go through anyway. I mean you don't avoid entering a username and password either with OpenID. But you avoid the confusion of choosing a OpenID provider, and the trip out to and back from and external site. With Microsoft making Live ID an OpenID provider (More Info), bringing on several hundred million additional accounts to those provided by Google, Yahoo, and others, this question is more important than ever. I have to require new customers to sign up during the checkout process, and it is absolutely critical that the experience be as easy and smooth as possible, every little bit harder it becomes translates into lost sales. No geek factor outweighs cold hard cash at the end of the day :) OpenID seems like a nice idea, but the implementation is of questionable value. What are the advantages of OpenID and is it really worth it in my scenario described above?

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• Deploying a WAR to tomcat only using a context descriptor

  - by DanglingElse

  i need to deploy a web application in WAR format to a remote tomcat6 server. The thing is that i don't want to do that the easy way, meaning not just copy/paste the WAR file to /webapps. So the second choice is to create a unique "Context Descriptor" and pointing this out to the WAR file. (Hope i got that right till here) So i have a few questions: Is the WAR file allowed to be anywhere in the file system? Meaning can i copy the WAR file anywhere in the remote file system, except /webapps or any other folder of the tomcat6 installation? Is there an easy way to test whether the deployment was successful or not? Without using any browser or anything, since i'm reaching to the remote server only via SSH and terminal. (I'm thinking ping?) Is it normal that the startup.sh/shutdown.sh don't exist? I'm not the admin of the server and don't know how the tomcat6 is installed. But i'm sure that in my local tomcat installations these files are in /bin and ready to use. I mean you can still start/restart/stop the tomcat etc., but not with the these -standard?- scripts. Thanks a lot.

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• regressions with many nested categorical covariates

  - by eric

  I have a few hundred thousand measurements where the dependent variable is a probability, and would like to use logistic regression. However, the covariates I have are all categorical, and worse, are all nested. By this I mean that if a certain measurement has "city - Phoenix" then obviously it is certain to have "state - Arizona" and "country - U.S." I have four such factors - the most granular has some 20k levels, but if need be I could do without that one, I think. I also have a few non-nested categorical covariates (only four or so, with maybe three different levels each). What I am most interested in is prediction - given a new observation in some city, I would like to know the relevant probability/dependent variable. I am not interested as much in the related inferential machinery - standard deviations, etc - at least as of now. I am hoping I can afford to be sloppy. However, I would love to have that information unless it requires methods that are more computationally expensive. Does anyone have any advice on how to attack this? I have looked into mixed effects, but am not sure it is what I am looking for.

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• How can I build a generic dataset-handling Perl library?

  - by Pep.

  Hello, I want to build a generic Perl module for handling and analysing biomedical character separated datasets and which can, most certain, be used on any kind of datasets that contain a mixture of categorical (A,B,C,..) and continuous (1.2,3,881..) and identifier (XXX1,XXX2...). The plan is to have people initialize the module and then use some arguments to point to the data file(s), the place were the analysis reports should be placed and the structure of the data. By structure of data I mean which variable is in which place and its name/type. And this is where I need some enlightenment. I am baffled how to do this in a clean way. Obviously, having people create a simple schema file, be it XML or some other format would be the cleanest but maybe not all people enjoy doing something like this. The solutions I can think of are: Create a configuration file in XML or similar and with a prespecified format. Pass the information during initialization of the module. Use the first row of the data as headers and try to guess types (ouch) Surely there must be a "canonical" way of doing this that is also usable and efficient. Thanks p.

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• Are there any code critique sites or similar resources?

  - by Ukko

  I have noticed when people post example code illustrating some issue that they are having often they will gather a number of comments addressing the quality of the code they presented and not the actual problem asked. This is very helpful--if not well directed. Often, this is wasted effort since the asker is often not receptive and the code is often chopped down to something small to post leaving lots of rough edges. In the old days you would see people asking questions like this on comp.lang.lisp and other parts of the comp.lang hierarchy. But that bit of the net kind of sank into the sewers of neglect. Is there a comparable one-stop-shop today? I am partially asking for selfish reasons, I know how to write good idiomatic C, Lisp, O'Caml, and Java code. But I learned C++ pre-template and STL, those rusty skills are not really applicable to today's C++. I have picked up languages like Scala in a vacuum and get by, but am I really doing it correctly? There are so many ways you can abuse a language, I am currently working against a codebase of Fortran written in C, and I recognize and loathe the "that guy" who wrote it. I don't want to be someone else's "that guy" if I can help it. Just because it works does not mean that one did not totally miss the boat on how it should have been done. Do you seek out this type of critique? If so how, where and why? What types of benefits do you derive from it? How about abuse and trolls?

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• Database schema for Product Properties

  - by Chemosh

  As so many people I'm looking for a Products /Product Properties database schema. I'm using Ruby on Rails and (Thinking) Sphinx for faceted searches. Requirements: Adding new product types and their options should not require a change to the database schema Support faceted searches using Sphinx. Solutions I've come across: (See Bill Karwin's answer) Option 1: Single Table Inheritance Not an option really. The table would contain way to many columns. Option 2: Class Table Inheritance Ruby on Rails caches the database schema on start-up which means a restart whenever a new type of product is introduced. If you have a size able product catalog this could mean hundreds of tables. Option 3: Serialized LOB Kills being able to do faceted searches without heavy application logic. Option 4: Entity-Attribute-Value For testing purposes, EAV worked fine. However it could quickly become a mess and a maintenance hell as you add more and more options (e.g. when an option increase the prices or delivery time). What option should I go with? What other solutions are out there? Is there a silver bullet (ha) I overlooked?

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• Integer Extensions - 1st, 2nd, 3rd etc [closed]

  - by David Schiefer

  Possible Duplicate: NSNumberFormatter and ‘th’ ‘st’ ‘nd’ ‘rd’ (ordinal) number endings Hello, I'm building an application that downloads player ranks and displays them. So say for example, you're 3rd out of all the players, I inserted a condition that will display it as 3rd, not 3th and i did the same for 2nd and 1st. When getting to higher ranks though, such as 2883rd, it'll display 2883th (for obvious reasons) My question is, how can I get it to reformat the number to XXX1st, XXX2nd, XXX3rd etc? To show what I mean, here's how I format my number to add a "rd" if it's 3 if ([[container stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceAndNewlineCharacterSet]] isEqualToString:@"3"]) { NSString*badge = [NSString stringWithFormat:@"%@rd",[container stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceAndNewlineCharacterSet]]]; NSString*scoreText = [NSString stringWithFormat:@"ROC Server Rank: %@rd",[container stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceAndNewlineCharacterSet]]]; profile.badgeValue = badge; rank.text = scoreText; } I can't do this for every number up to 2000 (there are 2000 ranks in total) - what can I do to solve this problem?

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• Is there a best practice for concatenating MP3 Files, adjusting sample rates to match, while preserving original files?

  - by Scott

  Hello overflow community! Does anyone know if there is a "best practice" to concatenate mp3 files to create new files, while preserving the original files? I am working on a CentOS Linux machine, in command line. I will eventually call the command line from a PHP script. I have been doing research and I have come up with a process that I think could work. It combines general advice from different forums, blogs, and sources like this one. So here I go: Create a temporary folder Loop through files to create a new, converted copy, of file into a "raw" format (which one, I don't know. I didn't know "raw" files existed before too long ago. I could use some suggestions on this) Store the path to the temporary files, in the temporary folder, and then loop through the files to concatenate them and then put the new merged file the final "processed directory" Delete the contents of the temporary file with the temporary raw files inside. Convert the final file from "raw" to mp3 and enjoy the finished result I'm thinking that this course of action might be best because I can't necessarily control the quality of the original "source" mp3s. The only other option I could think of would be to create a script that would perform a similar process upon files being added to the system leaving only the files with the "proper" format and removing the original "erroneous" file. Hopefully you can see that I have put some thought into this and that I'm trying to leverage the collective knowledge of this community to choose the best direction. Perhaps there is a better path that I could take? By concatenate, I mean to join together in sequence to create a new audio file from the "concatenated files."

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• Handling close-to-impossible collisions on should-be-unique values

  - by balpha

  There are many systems that depend on the uniqueness of some particular value. Anything that uses GUIDs comes to mind (eg. the Windows registry or other databases), but also things that create a hash from an object to identify it and thus need this hash to be unique. A hash table usually doesn't mind if two objects have the same hash because the hashing is just used to break down the objects into categories, so that on lookup, not all objects in the table, but only those objects in the same category (bucket) have to be compared for identity to the searched object. Other implementations however (seem to) depend on the uniqueness. My example (that's what lead me to asking this) is Mercurial's revision IDs. An entry on the Mercurial mailing list correctly states The odds of the changeset hash colliding by accident in your first billion commits is basically zero. But we will notice if it happens. And you'll get to be famous as the guy who broke SHA1 by accident. But even the tiniest probability doesn't mean impossible. Now, I don't want an explanation of why it's totally okay to rely on the uniqueness (this has been discussed here for example). This is very clear to me. Rather, I'd like to know (maybe by means of examples from your own work): Are there any best practices as to covering these improbable cases anyway? Should they be ignored, because it's more likely that particularly strong solar winds lead to faulty hard disk reads? Should they at least be tested for, if only to fail with a "I give up, you have done the impossible" message to the user? Or should even these cases get handled gracefully? For me, especially the following are interesting, although they are somewhat touchy-feely: If you don't handle these cases, what do you do against gut feelings that don't listen to probabilities? If you do handle them, how do you justify this work (to yourself and others), considering there are more probable cases you don't handle, like a supernonva?

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• "variable tracking" is eating my compile time!

  - by wowus

  I have an auto-generated file which looks something like this... static void do_SomeFunc1(void* parameter) { // Do stuff. } // Continues on for another 4000 functions... void dispatch(int id, void* parameter) { switch(id) { case ::SomeClass1::id: return do_SomeFunc1(parameter); case ::SomeClass2::id: return do_SomeFunc2(parameter); // This continues for the next 4000 cases... } } When I build it like this, the build time is enormous. If I inline all the functions automagically into their respective cases using my script, the build time is cut in half. GCC 4.5.0 says ~50% of the build time is being taken up by "variable tracking" when I use -ftime-report. What does this mean and how can I speed compilation while still maintaining the superior cache locality of pulling out the functions from the switch? EDIT: Interestingly enough, the build time has exploded only on debug builds, as per the following profiling information of the whole project (which isn't just the file in question, but still a good metric; the file in question takes the most time to build): Debug: 8 minutes 50 seconds Release: 4 minutes, 25 seconds

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• How do I DRY up business logic between sever-side Ruby and client-side Javascript?

  - by James A. Rosen

  I have a Widget model with inheritance (I'm using Single-Table Inheritance, but it's equally valid for Class-per-Table). Some of the subclasses require a particular field; others do not. class Widget < ActiveRecord ALL_WIDGET_TYPES = [FooWidget, BarWidget, BazWidget] end class FooWidget < Widget validates_presence_of :color end class BarWidget < Widget # no color field end class BazWidget < Widget validates_presence_of :color end I'm building a "New Widget" form (app/views/widgets/new.html.erb) and would like to dynamically show/hide the color field based on a <select> for widget_type. <% form_for @widget do |f| %> <%= f.select :type, Widget::ALL_WIDGET_TYPES %> <div class='hiddenUnlessWidgetTypeIsFooOrBaz'> <%= f.label :color %> <%= f.text_field :color %> </div> <% end %> I can easily write some jQuery to watch for onChange events on widget_type, but that would mean putting some sort of WidgetTypesThatRequireColor constant in my Javascript. Easy enough to do manually, but it is likely to get disconnected from the Widget model classes. I would prefer not to output Javascript directly in my view, though I have considered using content_for(:js) and have a yield :js in my template footer. Any better ideas?

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• Codeigniter/mySQL question. Checking if several inserts are possible before actual insertion.

  - by Ethan

  Hey SO, So I'm trying to perform a couple inserts at once that are kind of co-dependent on each other. Let's say I'm doing a dog rating website. Anyone can add a dog to my database, but in doing so they also need to add a preliminary rating of the dog. Other people can then rate the dog afterwards. The dogs to ratings is a many to one relationship: a dog has many ratings. This means for my preliminary add, since I have the person both rate and add the dog, I need to take the rating, and set a foreign key to the dog's primary key. As far as I know, this means I have to actually add the dog, then check what that new addition's primary key is, and then put that in my rating before insertion. Now suppose something were to go wrong with the rating's insert, be it a string that's too long, or something that I've overlooked somehow. If the rating's failed, the dog has already been inserted, but the rating has not. In this case, I'd like the dog to not have been added in the first place. Does this mean I have to write code that says "if the rating fails, do a remove for the dog," or is there a way to predict what the key will be for the dog should everything go as planned. Is there a way to say "hold that spot," and then if everything works, add it? Any help would be greatly appreciated. Thanks!!

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• Is there a term for this concept, and does it exist in a static-typed language?

  - by Strilanc

  Recently I started noticing a repetition in some of my code. Of course, once you notice a repetition, it becomes grating. Which is why I'm asking this question. The idea is this: sometimes you write different versions of the same class: a raw version, a locked version, a read-only facade version, etc. These are common things to do to a class, but the translations are highly mechanical. Surround all the methods with lock acquires/releases, etc. In a dynamic language, you could write a function which did this to an instance of a class (eg. iterate over all the functions, replacing them with a version which acquires/releases a lock.). I think a good term for what I mean is 'reflected class'. You create a transformation which takes a class, and returns a modified-in-a-desired-way class. Synchronization is the easiest case, but there are others: make a class immutable [wrap methods so they clone, mutate the clone, and include it in the result], make a class readonly [assuming you can identify mutating methods], make a class appear to work with type A instead of type B, etc. The important part is that, in theory, these transformations make sense at compile-time. Even though an ActorModel<T> has methods which change depending on T, they depend on T in a specific way knowable at compile-time (ActorModel<T> methods would return a future of the original result type). I'm just wondering if this has been implemented in a language, and what it's called.

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• question about MySQL transaction and trigger

  - by WilliamLou

  I quickly browsed MySQL manual but didn't find the exact information about my question. Here is my question: if I have a InnoDB table A with two triggers triggered by 'AFTER INSERT ON A' and 'AFTER UPDATE ON A'. More specifically, For example: one trigger is defined as: CREATE TRIGGER test_trigger AFTER INSERT ON A FOR EACH ROW BEGIN INSERT INTO B SELECT * FROM A WHERE A.col1 = NEW.col1 END; You can ignore the query between BEGIN AND END, basically I mean this trigger will insert several rows into table B which is also a InnoDB table. Now, if I started a transaction and then insert many rows, say: 10K rows, into table A. If there is no trigger associated with table A, all these inserts are atomic, that's for sure. Now, if table A is associated with several insert/update triggers which insert/update many rows to table B and/or table C etc.. will all these inserts and/or updates are still all atomic? I think it's still atomic, but it's kind of difficult to test and I can't find any explanations in the Manual. Anyone can confirm this? Thanks a lot!

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• How are two-dimensional arrays formatted in memory?

  - by Chris Cooper

  In C, I know I can dynamically allocate a two-dimensional array on the heap using the following code: int** someNumbers = malloc(arrayRows*sizeof(int*)); for (i = 0; i < arrayRows; i++) { someNumbers[i] = malloc(arrayColumns*sizeof(int)); } Clearly, this actually creates a one-dimensional array of pointers to a bunch of separate one-dimensional arrays of integers, and "The System" can figure you what I mean when I ask for: someNumbers[4][2]; But when I statically declare a 2D array, as in the following line...: int someNumbers[ARRAY_ROWS][ARRAY_COLUMNS]; ...does a similar structure get created on the stack, or is it of another form completely? (i.e. is it a 1D array of pointers? If not, what is it, and how do references to it get figured out?) Also, when I said, "The System," what is actually responsible for figuring that out? The kernel? Or does the C compiler sort it out while compiling?

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• Nullability (Regular Expressions)

  - by danportin

  In Brzozowski's "Derivatives of Regular Expressions" and elsewhere, the function d(R) returning ? if a R is nullable, and Ø otherwise, includes clauses such as the following: d(R1 + R2) = d(R1) + d(R2) d(R1 · R2) = d(R1) ? d(R2) Clearly, if both R1 and R2 are nullable then (R1 · R2) is nullable, and if either R1 or R2 is nullable then (R1 + R2) is nullable. It is unclear to me what the above clauses are supposed to mean, however. My first thought, mapping (+), (·), or the Boolean operations to regular sets is nonsensical, since in the base case, d(a) = Ø (for all a ? S) d(?) = ? d(Ø) = Ø and ? is not a set (nor is the return type of d, which is a regular expression). Furthermore, this mapping isn't indicated, and there is a separate notation for it. I understand nullability, but I'm lost on the definition of the sum, product, and Boolean operations in the definition of d: how are ? or Ø returned from d(R1) ? d(R2), for instance, in the definition off d(R1 · R2)?

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