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• How to associate application with existing file types using WiX installer?

  - by Marek

  related to this: http://stackoverflow.com/questions/138550/how-to-register-file-types-extensions-with-a-wix-installer but not a duplicate. I need to handle existing file types (.jpg files). I do not want to be the default handler for .jpg, I would just like to extend the "Open with" menu with a link to my app. I see HKCR\.jpg\OpenWithList\ and HKCR\.jpg\OpenWithProgIds\ in the registry but I am not sure whether to write to these and how to do it correctly with WiX. Should I use something like this? <ProgId Id='??what here?' Description='Jpeg handled by my App'> <Extension Id='jpg' ContentType='image/jpeg'> <Verb Id='openwithmyapp' Sequence='10' Command='OpenWithMyApp' Target='[!FileId]' Argument='"%1"' /> </Extension> </ProgId> There are many ways how to fail here (like Photo Mechanics did, the HKCR for image file types is a real mess after I have installed this software) How to do this correctly with WiX?

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• Thread-safety of read-only memory access

  - by Edmund

  I've implemented the Barnes-Hut gravity algorithm in C as follows: Build a tree of clustered stars. For each star, traverse the tree and apply the gravitational forces from each applicable node. Update the star velocities and positions. Stage 2 is the most expensive stage, and so is implemented in parallel by dividing the set of stars. E.g. with 1000 stars and 2 threads, I have one thread processing the first 500 stars and the second thread processing the second 500. In practice this works: it speeds the computation by about 30% with two threads on a two-core machine, compared to the non-threaded version. Additionally, it yields the same numerical results as the original non-threaded version. My concern is that the two threads are accessing the same resource (namely, the tree) simultaneously. I have not added any synchronisation to the thread workers, so it's likely they will attempt to read from the same location at some point. Although access to the tree is strictly read-only I am not 100% sure it's safe. It has worked when I've tested it but I know this is no guarantee of correctness! Questions Do I need to make a private copy of the tree for each thread? Even if it is safe, are there performance problems of accessing the same memory from multiple threads?

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• What do you mean by the expressiveness in programming lanuguage?

  - by prosseek

  I see a lot of the word 'expressiveness' when people want to stress one language is better than the other. But I don't see exactly what they mean by it. Is it the verboseness/succinctness? I mean, if one language can write down something shorter than the other, does that mean expressiveness? Please refer to my other question - http://stackoverflow.com/questions/2411772/article-about-code-density-as-a-measure-of-programming-language-power Is it the power of the language? Paul Graham says that one language is more powerful than the other language in a sense that one language can do that the other language can't do (for example, LISP can do something with macro that the other language can't do). Is it just something that makes life easier? Regular expression can be one of the examples. Is it a different way of solving the same problem: something like SQL to solve the search problem? What do you think about the expressiveness of a programming lanuage? Can you show the expressiveness using some code? What's the relationship with the expressiveness and DSL? Do people come up with DSL to get the expressiveness?

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• ASP.NET GridView "Client-Side Confirmation when Deleting" stopped working on ie - how come?

  - by tarnold

  A few months ago, I have programmed an ASP.NET GridView with a custom "Delete" LinkButton and Client-Side JavaScript Confirmation according to this msdn article: http://msdn.microsoft.com/en-us/library/bb428868.aspx (published in April 2007) or e.g. http://stackoverflow.com/questions/218733/javascript-before-aspbuttonfield-click The code looks like this: <ItemTemplate> <asp:LinkButton ID="deleteLinkButton" runat="server" Text="Delete" OnCommand="deleteLinkButtonButton_Command" CommandName='<%# Eval("id") %>' OnClientClick='<%# Eval("id", "return confirm(\"Delete Id {0}?\")") %>' /> </ItemTemplate> Surprisingly, "Cancel" doesn't work no more with my ie (Version: 6.0.2900.2180.xpsp_sp2_qfe.080814-1242) - it always deletes the row. With Opera (Version 9.62) it still works as expeced and described in the msdn article. More surprisingly, on a fellow worker's machine with the same ie version, it still works ("Cancel" will not delete the row). The generated code looks like <a onclick="return confirm(...);" href="javascript:__doPostBack('...')"> As confirm(...) returns false on "Cancel", I expect the __doPostBack event in the href not to be fired. Are there any strange ie settings I accidentally might have changed? What else could be the cause of this weird behaviour? Or is this a "please reinstall WinXP" issue?

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• problem configure JBoss to work with JNDI(2)

  - by Spiderman

  in continuation to the question from last week: http://stackoverflow.com/questions/2828237/problem-configure-jboss-to-work-with-jndi I'm trying to bind datasource in JBoss and use it in my application. In my struggling, I already managed to avoid the javax.naming.NameNotFoundException by: 1. using in java new InitialContext().lookup(connection); instead of new JndiObjectFactoryBean().setJndiName(connection); 2. changing the connection name from: 'jndi-name' to 'java:jndi-name' Now the problem is that the datasouce that I get from the lookup is null. I created the datsource file: <datasources> <local-tx-datasource> <jndi-name>bilby</jndi-name> <connection-url>jdbc:oracle:myURL</connection-url> <driver-class>oracle.jdbc.OracleDriver </driver-class> <user-name>myUsername</user-name> <password>myPassword</password> <exception-sorter-class- name>org.jboss.resource.adapter.jdbc.vendor.OracleExceptionSorter</exception-sorter-class-name> <metadata> <type-mapping>Oracle9i</type-mapping> </metadata> </local-tx-datasource> </datasources> and put it under \server\default\deploy\oracle-ds.xml I get during runtime the line: 18:37:56,560 INFO [ConnectionFactoryBindingService] Bound ConnectionManager 'jb oss.jca:service=DataSourceBinding,name=bilby' to JNDI name 'java:bilby' So my question is - why do I get null as my datasource???

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• JVM to ignore certificate name mismatch

  - by Heavy Bytes

  I know there were a lot of questions/answers about how to ignore SSL error in the code. On our dev region dev.domain.tld we have configured a app server over SSL. The certificate that is displayed is for somedev.domain.tld. There is no way to change the certificate, it will always be a domain mismatch. So when I deploy a web-service to https://dev.domain.tld and try to connect/call my webservice I get an exception: Caused by: java.security.cert.CertificateException: No name matching dev.domain.tld found And I have the somedev.domain.tld CERT in my trust store. Now, I saw a lot of samples how to change that in the code (using a Trust Manager that accepts all domains), but how do I specify to the JVM to ignore the domain mismatch when connecting to the server? Is there a -Djavax.net.ssl argument or something? Thank you! UPDATE: Or, since I am using Spring-WS, is there a way to set some property in Spring for that? (WebServiceTemplate) UPDATE I guess I'll have to do use something from Spring Security: http://static.springsource.org/spring-ws/sites/1.5/reference/html/security.html

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• difference between http.context.user and thread.currentprincipal and when to use them?

  - by yamspog

  I have just recently run into an issue running an asp.net web app under visual studio 2008. I get the error 'type is not resolved for member...customUserPrincipal'. Tracking down various discussion groups it seems that there is an issue with Visual Studio's web server when you assign a custom principal against the Thread.CurrentPrincipal. In my code, I now use... HttpContext.Current.User = myCustomPrincipal //Thread.CurrentPrincipal = myCustomPrincipal I'm glad that I got the error out of the way, but it begs the question "What is the difference between these two methods of setting a principal?". There are other stackoverflow questions related to the differences but they don't get into the details of the two approaches. I did find one tantalizing post that had the following grandiose comment but no explanation to back up his assertions... Use HttpConext.Current.User for all web (ASPX/ASMX) applications. Use Thread.CurrentPrincipal for all other applications like winForms, console and windows service applications. Can any of you security/dot.net gurus shed some light on this subject?

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• Looking for Opinions and Sugestions on my Website. (General Question)

  - by MrEnder

  I am looking for general opinions and suggestions about the site in whole. Its ok I don't mind hearing where I went wrong on anything. I'm still learning. All tips and pointers on any subject relating are highly welcome. If you are going to make a suggestion and post a snippet or code please explain how it works in detail. The site was design as a interface to display the labs I have to do in my college (the labs are all basic things that I'm way beyond). So I decided to take it all to the next level with this. The link is http://opentech.durhamcollege.ca/~intn2201/brittains/labs/ It is 100% designed by me with the exception of the icons. (I could not think of anything better to draw) There is no specific area of the site I want suggestions or opinions on this is a general question. You may answer about the site in whole or an area of the coding just please specify. If you have any questions related to my site or code you may ask them as well. Thank you for your time and any comments Shelby

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• Am I doing it right?

  - by LuckySlevin

  I have situation. I have to create a Sports Club system in JAVA. There should be a class your for keeping track of club name, president name and braches the club has. For each sports branch also there should be a class for keeping track of a list of players. Also each player should have a name, number, position and salary. So, I come up with this. Three seperate classes: public class Team { String clubName; String preName; Branch []branches; } public class Branch { Player[] players; } public class Player { String name; String pos; int salary; int number; } The problems are creating Branch[] in another class and same for the Player[]. Is there any simplier thing to do this? For example, I want to add info for only the club name, president name and branches of the club, in this situation, won't i have to enter players,names,salaries etc. since they are nested in each other. I hope i could be clear. For further questions you can ask.

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• Creating a method for wrapping a loaded image in a UIImageView

  - by eco_bach

  I have the following un my applicationDidFinishLaunching method UIImage *image2 = [UIImage imageWithContentsOfFile:[[NSBundle mainBundle] pathForResource:@"image2.jpg" ofType:nil]]; view2 = [[UIImageView alloc] initWithImage:image2]; view2.hidden = YES; [containerView addSubview:view2]; I'm simply adding an image to a view. But because I need to add 30-40 images I need to wrap the above in a function (which returns a UIImageView) and then call it from a loop. This is my first attempt at creating the function -(UIImageView)wrapImageInView:(NSString *)imagePath { UIImage *image = [UIImage imageWithContentsOfFile:[[NSBundle mainBundle] pathForResource:imagePath ofType:nil]]; UIImageView *view = [[UIImageView alloc] initWithImage:image]; view.hidden = YES; } And then to invoke it I have the following so far, for simplicity I am only wrapping 3 images //Create an array and add elements to it NSMutableArray *anArray = [[NSMutableArray alloc] init]; [anArray addObject:@"image1.jpg"]; [anArray addObject:@"image2.jpg"]; [anArray addObject:@"image3.jpg"]; //Use a for each loop to iterate through the array for (NSString *s in anArray) { UIImageView *wrappedImgInView=[self wrapImage:s]; [containerView addSubview:wrappedImgInView]; NSLog(s); } //Release the array [anArray release]; I have 2 general questions 1-Is my approach correct?, ie following best practices, for what I am trying to do (load a multiple number of images(jpgs, pngs, etc.) and adding them to a container view) 2-For this to work properly with a large number of images, do I need to keep my array creation separate from my method invocation? Any other suggestions welcome!

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• Safari Web Inspector is not updating when I update an element with ajax

  - by Ashley

  I have a checkout page http://www.oipolloi.com/oipolloi/shop/viewbasket.php with multiple ajax calls after certain items update (EG look up postage cost when country is changed, then update discount boxes etc). I've asked for help in the past about the best method of making sure ALL calls have returned before allowing the form to be submitted for payment processing: http://stackoverflow.com/questions/2290372/how-do-i-prevent-form-submission-until-multiple-ajax-calls-have-finished-jquery I was fairly happy that the logic in the finished solution was correct, but I have still been receiving reports that people using Safari are able to submit the form without the ajax calls returning properly. I have tried using the Safari Web Inspector to debug but it seems that when you Inspect Element, then update an element with an ajax call, the Inspector doesn't seem to update. I am updating hidden fields, so it's hard to be able to know whether the problem lies with the DOM not being updated properly, or the Inspector itself. I'm using Safari 4.0.5 on PC and you can reproduce the problem above by looking for a div id="countryFieldsBilling" with Web Inspector. It should contain three hidden fields that are initially empty. You can try to make it update (or not) by choosing a country from the select menu at the bottom of 'Shipping Address' box, and then clicking the 'click to use Shipping Address' link at the top of the 'Billing Address' just below. The behaviour I am seeing is that the country chosen in the shipping select gets copied correctly to the country in the billing select, but the hidden inputs in the Web Inspector do not get updated. When these hidden inputs do not get updated, this causes the problem that Mac Safari users report. If you can let me know either how to get Web Inspector to work properly, or something else I may have missed in the behaviour of Mac Safari that may cause these problems, that would be great. Thanks in advance

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• how do I get a new line, after using float:left?

  - by codeman73

  What I am trying to do is have rows of images, 6 images in each row. Some of these images need to have another image floating on top of them (flush with the lower-right corner). I was able to get that to work from this thread: http://stackoverflow.com/questions/48474/how-do-i-position-one-image-on-top-of-another-in-html However, now I'm unable to get the new row after the 6th image. Neither <BR> or <P> create a new line. They simply push the next image down several pixels, but the image is still in the same line. It seems like the float style is interfering with the <BR> and/or <P>. I tried using different styles for the image that starts a new row, like float:none and display:block, but neither worked. The odd thing is that the new line starts after the 7th image. Here's what I'm using so far: <style type="text/css"> .containerdiv { float: left; position: relative; } .containerdivNewLine { float: none; display: block; position: relative; } .cornerimage { position: absolute; bottom: 0; right: 0; } </style> <div class="containerdiv"> <img border="0" height="188" src="myImg" width="133" /> <img class="cornerimage" height="140" src="imageOnTop" width="105" /> </div> For the 7th image, when I'm trying to start a new row, I'm simply replacing the 'containerdiv' class with 'containerdivNewLine'.

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• asp.net Can I force every page to inherit from a base page? Also should some of this logic be in my master page?

  - by Bex

  Hi! I have a web app that has a base page. Each page needs to inherit from this base page as it contains properties they all need as well as dealing with the login rights. My base page has some properties, eg: IsRole1, IsRole2, currentUserID, Role1Allowed, Role2Allowed. On the init of each page I set the properties "Role1Allowed" and "Role2Allowed" Private Sub Page_Init(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Init Role1Allowed = True Role2Allowed= False End Sub The basepage then decides if the user needs redirecting. 'Sample code so not exactly what is going to be, bug gives the idea Protected Overridable Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) If Role1Allowed And Not Role1 Then 'Redirect somewhere End If End Sub The page then must override this pageload if they need anything else in it, but making sure they call the base pageload first. Protected Overrides Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load MyBase.Page_Load(sender, e) If Not IsPostBack Then BindGrid() End If End Sub The other properties (IsRole1, IsRole, currentUserID) are also accessible by the page so it can be decided if certain things need doing based on the user. (I hope this makes sense) Ok so I have 2 questions Should this functionality be in the base page or should it somehow be in the master, and if so how would I get access to all the properties if it was? As there are multiple people working on this project and creating pages some are forgetting to inherit from this basepage, or call the base pageload when overriding it. Is there any way to force them to do this? Thanks for any help. bex

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• Sync two SqlExpress using NHibernate

  - by Christian

  Hello, I am creating a simple project management system which uses NHibernate for object storage. The underlying database is SQL express (at least currently for development). The client runs on either the desktop or laptop. I know I could use web-services and store the DB only on the desktop, but this would force the desktop to be available all the time. I am currently thinking about duplicating the DB, having two instances with "different data". To clarify, we are not talking about a productive app here, its a prototype. One way to achieve this very simple would be the following process: Client: Check if desktop DB is available (through web service) Client: If yes, use desktop storage, no problem here Client: If not, use own DB as storage Client: Poll desktop regulary, as soon as it comes on, sync Client: Switch to desktop storage ... Desktop: Do not attempt any DB operation before checking for required sync Desktop: If sync needed, do it... My question is now, how would you sync? Assume 4 or 5 types of objects, all have GUID as identifiers. Would you always manually "lazy load" all objects of a certain type and feed them to the DB. Would you always drop the whole desktop DB in case the client DB may be newer and out of sync? Again, I want to stress out, I am not assuming any conflicts or stale data, I basically just want to "copy the whole DB from the client". Would you use NHibernate for this? Or would you separate the copy process? When I think about it, my questions comes down to this: Is there any function from NHibernate: SyncDBs_SourceWins_(SourceDB, TargetDB) Thanks for help, Chris

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• Scratch the screen to display an image in android

  - by user1008497

  i am working on a android project for my assignment. i am trying to make a scratch image application, you know it's like we scratch the screen to get rid the blocking layer to display the image. but the problem is i don't know where to start. i have searching in stackoverflow's questions that related to this but that's not help. from my search there, i found a clue for this project is using Bitmap.getPixel(int x, int y). so, in my thought i have to get pixel from bitmap and paint it to canvas. but i don't know how to implement it? or anyone has a better method for this? Could anyone please help me? Any tutorials on this kind of thing or related topics? Thanks in advance! here's my sample code: @Override protected void onSizeChanged(int w, int h, int oldw, int oldh) { super.onSizeChanged(w, h, oldw, oldh); tw = w; th = h; eraseableBitmap = Bitmap.createBitmap(w, h, Bitmap.Config.ARGB_8888); mCanvas = new Canvas(eraseableBitmap); Bitmap muteableBitmap = Bitmap.createBitmap(eraseableBitmap.getWidth(), eraseableBitmap.getHeight(), Bitmap.Config.ARGB_8888); } @Override public boolean onTouchEvent(MotionEvent event) { static_x = event.getX(); static_y = event.getY(); if (event.getAction() == MotionEvent.ACTION_DOWN) { touch_start(static_x, static_y); } if (event.getAction() == MotionEvent.ACTION_MOVE) { touch_move(static_x, static_y); } if (event.getAction() == MotionEvent.ACTION_UP) { touch_up(); } return true; }

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• Big-O for calculating all routes from GPS data

  - by HH

  A non-critical GPS module use lists because it needs to be modifiable, new routes added, new distances calculated, continuos comparisons. Well so I thought but my team member wrote something I am very hard to get into. His pseudo code int k =0; a[][] <- create mapModuleNearbyDotList -array //CPU O(n) for(j = 1 to n) // O(nlog(m)) for(i =1 to n) for(k = 1 to n) if(dot is nearby) adj[i][j]=min(adj[i][j], adj[i][k] + adj[k][j]); His ideas transformations of lists to tables His worst case time complexity is O(n^3), where n is number of elements in his so-called table. Exception to the last point with Finite structure: O(mlog(n)) where n is number of vertices and m is the amount of neighbour vertices. Questions about his ideas why to waste resources to transform constantly-modified lists to table? Fast? only point where I to some extent agree but cannot understand the same upper limits n for each for-loops -- perhaps he supposed it circular why does the code take O(mlog(n)) to proceed in time as finite structure? The term finite may be wrong, explicit?

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• Timer appears to be pausing when screen becomes inactive

  - by elchuppa

  So I have a very simple android activity that starts a timer when you hit a button. Timer timer = new Timer(); timer.schedule(new TimerTask() { @Override public void run() { doStuff(); } }, 15 * 60 * 1000); So this worked reasonably well for me when I was testing but as it turns out when the screen becomes inactive so does the timer. I was a bit surprised by this. I understand you need to create a service to have anything running in the background but I hadn't realized this is required for an activity in the foreground when the phone has inactivated the screen due to lack of activity. What confuses me is I think this worked as I expected originally and just in the last few weeks or so has the timer been affected by the phone saving power. I could be wrong though.. So basically my questions are: am I seeing expected behavior? Do I need to create all timers as services or somehow disallow powersaving? thanks for any advice, Patrick

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• I can learn either C or Java, which one should I choose first? Should I take them concurrently?

  - by GR1000

  I realize this is a subject of hot debate, but I'm interested in opinions that relate to my specific situation. I want to learn the basics and fundamentals of programming, so I'm already taking a college course in general programming concepts. It isn't covering a specific language, but it's giving me a solid foundation that I can build upon when I move on to a class that teaches a specific language. My two options for a specific language are Java and C because those are the two languages taught at the college I want to take classes from. What I want to do is learn a complex language so that I can apply that knowledge to languages that I use, or will eventually use, in my current job building web pages: XHTML, CSS, JavaScript, PHP, XML, ActionScript. I'm not necessariy interested in becoming a Java developer or a C developer in the immediate future, but I do have aspirations of developing web applications and iPod/iPhone applications. So, basically, I'm looking for answers to these questions and the reasoning behind them: Do I take the introductory course in Java first, and then take the intro course in C, or Do I take C first and then take Java? Is there any reason not to take them concurrently? Should I skip C altogether as Java covers everything I need to know? EDIT: Thanks everyone for your thoughtful and insightful responses.

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• Avoiding mass propagation of properties and events for exposure to ViewModels.

  - by firoso

  I have an MVVM application I am developing that is to the point where I'm ready to start putting together a user interface (my client code is largely functional) I'm now running into the issue that I'm trying to get my application data to where I need it so that it can be consumed by the view model and then bound to the view. Unfortunately, it seems that I've either got a few structural oversights, or I'm just going to have to face the reality that I need to be propogating events and raising excessive amounts of errors to notify view models that thier properties have changed. Let me go into some examples of my issue: I have a class "Unit" contained in a class "Test", contained in a class "Session" contained in a class "TestManager" which is contained in "TestDataModel" which is utilized by "TestViewModel" which is databound to by my "TestView" .... WHOA. Now, consider that Unit (the bottom of the heiarchy) has a property called "Results" that is updated periodically, I want to expose that to my viewmodel and then databind it to my view, trouble is, the only way I can really think to do this is to perpetuate events WAY up a chain that say "I've been updated!" and then request the new value... This seems like an aweful way to do this. Alternatively, I could register a static event and raise it, and have the appropriate "Unit view model" grab the event and request the update. This SEEMS better... but... static events? Is that a taboo idea? Also, having an expression like: TestDataModel.TestManager.Session.Test.Unit.Results[i] Seems REALLY gross to have on a View Model. I know this all reeks of a bad design issue, but I can't figure out what I did wrong? Should I be using more singleton/container controlled lifetimes type objects? Register object instances with static helper containers? Obviously these are hard questions to answer without being intimate with the existing structure, but if you've run into situations like this, what did you do to refactor? Should I just live with this, add mass events, and propogate them?

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• How to detect column conflicts with Hibernate?

  - by Slim

  So let's say I have an ArrayList full of Products that need to be committed to the database via Hibernate. There are already a large number of Products in the database. Each product has an ID. Note this is NOT the PK that is autogenerated by Hibernate. My questions is: what is the best way to detect conflicts with this ID? I am looking for a relatively efficient method of obtaining, from the the database, a List of Products that share an ID with any of the Products in my ArrayList. This is all in a single table called Products and the ID attribute is in column ProductID. The way I've done it is grabbing a list of all Products in the database, and compared each one with each entry in my ArrayList - but that is seriously inefficient and I don't think it would work well with a larger database. How should it be done? Thanks. I say "relatively" efficient because efficiency is not the primary concern, but it shouldn't take noticeably long to test against a table of ~1000-5000 rows. Help? EDIT* I'm very new to hibernate and below is the best I've come up with. How does this look? for(long id : idList){ //idList just holds the IDs of each Product in my ArrayList Query query = session.createQuery("select product from Product product where product.id = :id"); query.setLong("id", id); for(int i = 0; i < query.list().size(); i++){ listOfConflictingProducts.add((Product) query.list().get(i)); } }

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• Code promotion: Enforcing the rules

  - by jbarker7

  So here is our problem: We have a small team of developers with their own ways of doing things-- I am trying to formalize a process in which we are required to promote our code in the following order: Local sandbox Dev UAT Staging Live Developers develop/test as they go on their own sandbox, Dev is its own box that we would use for continuous integration, UAT is another site in IIS on the dev box, which uses our dev database. We then promote to staging, which is a site in IIS on the Live box and using live data (just like the live, hence staging). Then, finally, we promote to live. Here are a few of my questions: 1.) Does this seem to be best practice? If not, what needs to be done differently? 2.) How do I enforce the rules to the developers? Often developers skip steps in order to save time... this should not be tolerated and would be great if it could be physically enforced. 3.) How do I enforce these rules to the business group? The business group just wants to get features out FAST. Do we promote only on certain days? Thanks! Josh

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• Django: Determining if a user has voted or not

  - by TheLizardKing

  I have a long list of links that I spit out using the below code, total votes, submitted by, the usual stuff but I am not 100% on how to determine if the currently logged in user has voted on a link or not. I know how to do this from within my view but do I need to alter my below view code or can I make use of the way templates work to determine it? I have read http://stackoverflow.com/questions/1528583/django-vote-up-down-method but I don't quite understand what's going on ( and don't need any ofjavascriptery). Models (snippet): class Link(models.Model): category = models.ForeignKey(Category, blank=False, default=1) user = models.ForeignKey(User) created = models.DateTimeField(auto_now_add=True) modified = models.DateTimeField(auto_now=True) url = models.URLField(max_length=1024, unique=True, verify_exists=True) name = models.CharField(max_length=512) def __unicode__(self): return u'%s (%s)' % (self.name, self.url) class Vote(models.Model): link = models.ForeignKey(Link) user = models.ForeignKey(User) created = models.DateTimeField(auto_now_add=True) def __unicode__(self): return u'%s vote for %s' % (self.user, self.link) Views (snippet): def hot(request): links = Link.objects.select_related().annotate(votes=Count('vote')).order_by('-created') for link in links: delta_in_hours = (int(datetime.now().strftime("%s")) - int(link.created.strftime("%s"))) / 3600 link.popularity = ((link.votes - 1) / (delta_in_hours + 2)**1.5) if request.user.is_authenticated(): try: link.voted = Vote.objects.get(link=link, user=request.user) except Vote.DoesNotExist: link.voted = None links = sorted(links, key=lambda x: x.popularity, reverse=True) links = paginate(request, links, 15) return direct_to_template( request, template = 'links/link_list.html', extra_context = { 'links': links, }) The above view actually accomplishes what I need but in what I believe to be a horribly inefficient way. This causes the dreaded n+1 queries, as it stands that's 33 queries for a page containing just 29 links while originally I got away with just 4 queries. I would really prefer to do this using Django's ORM or at least .extra(). Any advice?

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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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• Pointer arithmetic.

  - by Knowing me knowing you

  Having code: int** a = new int*[2]; a[0] = new int(1); a[1] = new int(2); cout << "a[0] " << a[0] << '\n'; cout << "a[1] " << a[1] << '\n'; cout << "a[2] " << a[2] << '\n'; cout << "a[0] + 1 " << a[0] + 1 << '\n';//WHY THIS ISN'T == a[1] ? cout << "*(a + 1): " << *(a + 1) << '\n'; //WHY THIS IS == a[1] ? cout << "a[0] - a[1] " << static_cast<int>(a[0] - a[1])<< '\n';//WHY THIS IS == 16 not 4? cout << sizeof(int**); Questions are included right next to relevant lines in code.

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• What exactly does this PHP code do?

  - by Rob

  Alright, my friend gave me this code for requesting headers and comparing them to what the header should be. It works perfectly, but I'm not sure why. Here is the code: $headers = apache_request_headers(); $customheader = "Header: 7ddb6ffab28bb675215a7d6e31cfc759"; foreach ($headers as $header => $value) { // 1 $custom .= "$header: $value"; // 2 } $mystring = $custom; // 3 $findme = $customheader; // 4 $pos = strpos($mystring, $findme); if ($pos !== false) { // Do something } else{ exit(); } //If it doesn't match, exit. I commented with some numbers relating to the following questions: 1: What exactly is happening here? Is it setting the $headers as $header AND $value? 2: Again, don't have any idea what is going on here. 3: Why set the variable to a different variable? This is the only area where the variable is getting used, so is there a reason to set it to something else? 4: Same question as 3. I'm sorry if this is a terrible question, but its been bothering me, and I really want to know WHY it works. Well, I understand why it works, I guess I just want to know more specifically. Thanks for any insight you can provide.

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