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• In-Store Tracking Gets a Little Harder

  - by David Dorf

  Remember how Nordstrom was tracking shopper movements within their stores using the unique number, called a MAC, emitted by the WiFi radio in smartphones?  The phones didn't need to connect to the network, only have their WiFi enabled, as most people do by default.  They did this, presumably, to track shoppers' path to purchase and better understand traffic patterns.  Although there were signs explaining this at the entrances, people didn't like the notion of being tracked.  (Nevermind that there are cameras in the ceiling watching them.)  Nordstrom stopped the program. To address this concern the Future of Privacy, a Washington think tank, created Smart Store Privacy, a do-not-track service that allows consumers to register their MAC address in much the same way people register their phone numbers in the national do-not-call list.  A group of companies agreed to respect consumers' wishes and ignore smartphones listed in the database.  The database includes Bluetooth identifiers as well.  Of course you could simply turn your bluetooth and WiFi off when shopping as well. Most know that Apple prefers to use BLE beacons to contact and track smartphones within their stores.  This feature extends the typical online experience to also work in physical stores.  By identifying themselves, shoppers can expect a more tailored shopping experience much like what we've come to expect from Amazon's website, with product recommendations and offers that are (usually) relevant. But the upcoming release of iOS8 is purported to have a new feature that randomizes the WiFi MAC address of smartphones during the "probing" phase.  That is, before connecting to the WiFi network, a random MAC number is used so as to keep the smartphone's real MAC address secret.  Unless you actually connect to the store's WiFi, they won't recognize the MAC address. The details on this are still sketchy, but if the random MAC is consistent for a short period, retailers will still be able to track movements anonymously, but they won't recognize repeat visitors.  That may be sufficient for traffic analytics, but it will stymie target marketing.  In the case of marketing, using iBeacons with opt-in permission from consumers will be the way forward. There is always a battle between utility and privacy, so I expect many more changes in this area.  Incidentally, if you'd like to see where beacons are being used this site tracks them around the world.

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• WHERE x = @x OR @x IS NULL

  - by steveh99999

  Every SQL DBA and developer should read the blog of MVP Erland Sommarskog – but particularly  his article on dynamic search conditions in T-SQL. I’ve linked above to his SQL 2005 article but his 2008 version is also a must-read. I seem to regularly come across uses of the SQL in the title above… Erland’s article explains in detail why this is inefficient, but I came across a nice example recently… A stored procedure contained the following code :- WHERE @Name is null or [Name] like @Name as a nonclustered index exists on the Name column, you might assume this would be handled efficiently by SQL Server. However, I got the following output from SET STATISTICS IO Table 'xxxxx'. Scan count 15, logical reads 47760, physical reads 9, read-ahead reads 13872, lob logical reads 0, lob physical reads 0, lob read-ahead reads 0. Note the high number of logical reads… After a bit of investigation, we found that @Name could never actually be set to NULL in this particular example. ie the @x IS NULL was spurious… So, we changed the call to WHERE  [Name] like @Name Now, how much more efficient is this code ? Table 'xxxxx'. Scan count 3, logical reads 24, physical reads 0, read-ahead reads 0, lob logical reads 0, lob physical reads 0, lob read-ahead reads 0 A nice easy win in this case…… a full index scan has been replaced by a significantly more efficient index seek. I managed to recreate the same behaviour on Adventureworks – here’s a quick query to demonstrate :- USE adventureworks SET STATISTICS IO ON DECLARE @id INT = 51721 SELECT * FROM Sales.SalesOrderDetail WHERE @id IS NULL OR salesorderid = @id SELECT * FROM Sales.SalesOrderDetail WHERE salesorderid = @id Take a look at the STATISTICS IO output and compare the actual query plans used to prove the impact of  WHERE @id IS NULL. And just to follow some of Erland’s advice – here’s how you could get similar performance if it was possible that @id could actually sometimes contain NULL. DECLARE @sql NVARCHAR(4000), @parameterlist NVARCHAR(4000) DECLARE @id INT = 51721 – or change to NULL to prove query is functionally correct SET @sql = 'SELECT * FROM Sales.SalesOrderDetail WHERE 1 = 1' IF @id IS NOT NULL SET @sql = @sql + ' AND salesorderid = @id' IF @id IS NULL SET @sql = @sql + ' AND salesorderid IS NULL' SET @parameterlist = '@id INT' EXEC sp_executesql @sql, @parameterlist,@id Sometimes I think we focus too much on hardware and SQL Server configuration – when really the answer is focus on writing efficient SQL.

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• Practices for domain models in Javascript (with frameworks)

  - by AndyBursh

  This is a question I've to-and-fro'd with for a while, and searched for and found nothing on: what're the accepted practices surrounding duplicating domain models in Javascript for a web application, when using a framework like Backbone or Knockout? Given a web application of a non-trivial size with a set of domain models on the server side, should we duplicate these models in the web application (see the example at the bottom)? Or should we use the dynamic nature to load these models from the server? To my mind, the arguments for duplicating the models are in easing validation of fields, ensuring that fields that expected to be present are in fact present etc. My approach is to treat the client-side code like an almost separate application, doing trivial things itself and only relying on the server for data and complex operations (which require data the client-side doesn't have). I think treating the client-side code like this is akin to separation between entities from an ORM and the models used with the view in the UI layer: they may have the same fields and relate to the same domain concept, but they're distinct things. On the other hand, it seems to me that duplicating these models on the server side is a clear violation of DRY and likely to lead to differing results on the client- and server-side (where one piece gets updated but the other doesn't). To avoid this violation of DRY we can simply use Javascripts dynamism to get the field names and data from the server as and when they're neeed. So: are there any accepted guidelines around when (and when not) to repeat yourself in these situations? Or this a purely subjective thing, based on the project and developer(s)? Example Server-side model class M { int A DateTime B int C int D = (A*C) double SomeComplexCalculation = ServiceLayer.Call(); } Client-side model function M(){ this.A = ko.observable(); this.B = ko.observable(); this.C = ko.observable(); this.D = function() { return A() * C(); } this.SomeComplexCalculation = ko.observalbe(); return this; }l M.GetComplexValue = function(){ this.SomeComplexCalculation(Ajax.CallBackToServer()); }; I realise this question is quite similar to this one, but I think this is more about almost wholly untying the web application from the server, where that question is about doing this only in the case of complex calculation.

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• Best way to determine surface normal for a group of pixels?

  - by Paul Renton

  One of my current endeavors is creating a 2D destructible terrain engine for iOS Cocos2D (See https://github.com/crebstar/PWNDestructibleTerrain ). It is in an infant stages no doubt, but I have made significant progress since starting a couple weeks ago. However, I have run into a bit of a performance road block with calculating surface normals. Note: For my destructible terrain engine, an alpha of 0 is considered to not be solid ground. The method posted below works just great given small rectangles, such as n < 30. Anything above 30 causes a dip in the frame rate. If you approach 100x100 then you might as well read a book while the sprite attempts to traverse the terrain. At the moment this is the best I can come up with for altering the angle on a sprite as it roams across terrain (to get the angle for a sprite's orientation just take dot product of 100 * normal * (1,0) vector). -(CGPoint)getAverageSurfaceNormalAt:(CGPoint)pt withRect:(CGRect)area { float avgX = 0; float avgY = 0; ccColor4B color = ccc4(0, 0, 0, 0); CGPoint normal; float len; for (int w = area.size.width; w >= -area.size.width; w--) { for (int h = area.size.height; h >= -area.size.height; h--) { CGPoint pixPt = ccp(w + pt.x, h + pt.y); if ([self pixelAt:pixPt colorCache:&color]) { if (color.a != 0) { avgX -= w; avgY -= h; } // end inner if } // end outer if } // end inner for } // end outer for len = sqrtf(avgX * avgX + avgY * avgY); if (len == 0) { normal = ccp(avgX, avgY); } else { normal = ccp(avgX/len, avgY/len); } // end if return normal; } // end get My problem is I have sprites that require larger rectangles in order for their movement to look realistic. I considered doing a cache of all surface normals, but this lead to issues of knowing when to recalculate the surface normals and these calculations also being quite expensive (also how large should the blocks be?). Another smaller issue is I don't know how to properly treat the case when length is = 0. So I am stuck... Any advice from the community would be greatly appreciated! Is my method the best possible one? Or should I rethink the algorithm? I am new to game development and always looking to learn new tips and tricks.

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• Website directory structure regarding subdomains, www, and "global" content

  - by Pawnguy7

  I am trying to make a homemade HTTP server. It occurs to me, though, I never fully understood what you might call "relativity" among web pages. I have come across that www. is a subdomain, and I understand its original purpose. IT sounds like, in general, you would redirect (is that 301 or 302?) it to a... non-subdomain, sort of. As in, redirecting www.example.com to example.com. I am not entirely sure how to make this work when retrieving files for an HTTP server though. I would assume that example.com would be the root, and www manifests as a folder within it. I am unsure. There is also the question of multi-level subdomains, e.g. subdomain2.subdomain1.example.com. It seems to me they are structured "backwards", where you go from the root left in folder structure. In this situation, subdomain2 is a directory within subdomain1, which is a directory in the root. Finally, it occurs to me I might want a sort of global location. For example, maybe all subdomains still use an image as a logo. It makes more sense to me that there is one image, rather than each having a copy. In the same way, albiet more doubtfully, you might have global CSS (though that is a bit contrary to the idea of a subdomain in the first place), or a javascript that is commonly used. (more efficient than each having its copy and better for organization purposes). Finally, mabye you have a global 404 page. I think this might be the case where you have user-created subdomains (say bloggername.example.com), where example.com still has a default 404 when either a subdomain does not exist or page does not exists under a valid blogger. I am confused on what the directory structure for this should be. To summarize: Should and how it have a global files not in a subdirectory, how should www. be handled, (or how a now www or other subdomain should be handled), and the pattern for root/subdomain, as well as subdomain within subdomains (order-wise). Sorry this is multiple questions, but I feel at the root they are all related to the directory.

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• URL slugs: ideal length, and the real SEO effects of these slugs

  - by tattvamasi

  this question is addressed widely on SO and outside it, but for some reason, instead of taking it as a good load of great advice, all this information is confusing me. ** Problem ** I already had, on one of my sites, "prettified" urls. I had taken out the query strings, rewritten the URLS, and the link was short enough for me, but had a problem: the ID of the item or post in the URL isn't good for users. One of the users asked is there's a way to get rid of numbers, and I thought it was better for users to just see a clue of the page content in the URL. ** Solution ** With this in mind, I am trying with a section of the site.Armed with 301 redirects, some parsing work, and a lot of patience, I have added the URL slugs to some blog entries, and the slug of the URL reports the title of the article (something close to http://example.com/my-news/terribly-boring-and-long-url-that-replaces-the-number-I-liked-so-much/ ** Problems after Solution ** The problem, as I see it, is that now the URL of those blog articles is very descriptive for sure, but it is also impossible to remember. So, this brings me to the same issue I had with my previous problem: if numbers say nothing and can't be remembered, what's the use of these slugs? I prefer to see http://example.com/my-news/1/ than http://example.com/my-news/terribly-boring-and-long-url-that-replaces-the-number-I-liked-so-much/ To avoid forcing my user to memorize my URLS, I have added a script that finds the closest match to the URL you type, and redirects there. This is something I like, because the page now acts as a sort of little search engine, and users can play with the URLS to find articles. ** Open questions ** I still have some open questions, and don't seem to be able to find an answer, because answers tend to contradict one another. 1) How many characters should an URL ideally be long? I've read the magic number 115 and am sticking to that, but am not sure. 2) Is this really good for SEO? One of those blog articles I have redirected, with ID number in the URL and all, ranked second on Google. I've just found this question, and the answer seems to be consistent with what I think URL slug and SEO - structure (but see this other question with the opposite opinion) 3) To make a question with a specific example, would this URL risk to be penalized? Is it acceptable? Is it too long? StackOverflow seems to have comparably long URLs, but I'm not sure it's a winning strategy in my case. I just wanted to facilitate my users without running into Google's algorithms.

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• HOW TO: Change Internet Expenses Cost Center Prompt

  - by rveliche

  The cost center segment on the General Information page in Oracle Internet Expenses derives its label from the Prompt entered on the KFF setup. Changing this is not possible with the simple personalization, the details below provide the instructions to change the Prompt. Create a custom class, I call it CustomHeaderKffCO.java in the package oracle.apps.ap.oie.entry.header.webui  (or any other). This class will have to extend from oracle.apps.ap.oie.entry.header.webui.HeaderKffCO. Add the following logic to your custom class. package oracle.apps.ap.oie.entry.header.webui; import oracle.apps.fnd.framework.webui.OAPageContext; import oracle.apps.fnd.framework.webui.beans.OAWebBean; import oracle.apps.fnd.framework.webui.beans.message.OAMessageLayoutBean; import oracle.apps.fnd.framework.webui.OAControllerImpl; public class CustomHeaderKffCO extends HeaderKffCO {   public void processRequest(OAPageContext pageContext, OAWebBean webBean)   {      super.processRequest(pageContext, webBean);     OAMessageLayoutBean layoutBean = (OAMessageLayoutBean) webBean.findChildRecursive("KffSEGMENT2MessageLayout");    if(layoutBean != null)   {     // You should use messages/lookups to avoid translation issues.     layoutBean.setLabel("Cost Center");   }   } } KffSEGMENT2MessageLayout is for illustration only, my Chart Of Accounts has SEGMENT2 as the cost center segment. Please change this to a segment being used eg.Segment6 should be KFFSEGMENT6MessageLayout Note that super.processRequest(pageContext, webBean); is a must and should always be the first statement. Once the class is compiled, copy the class to an appropriate directory, in my case I used $JAVA_TOP/oracle/apps/ap/oie/entry/header/webui. Navigate to the General Information page, click on "Personalize General Information Page".Click on Personalize icon next to Message Component Layout: (OIEGeneralInformationMsgCLayout)In the controller class section update the new controller at the appropriate levelIf the Link "Personalize General Information Page" is not visible on your instance, check your personalization profiles.

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• Upgrades from Beta or CTP SQL Server Software is NOT Supported

  - by BuckWoody

  As of this writing, SQL Server 2008 R2 has released, and just like every release, I get e-mails and calls from folks with this question: “Can I upgrade from Customer Technical Preview (CTP) x or Beta #x or Release Candidate (RC) to the “Released to Manufacturing” (RTM) version?” No. Right up until the last minute, things are changing in the code – and you want that to happen. Our internal testing runs right up until the second we lock down for release, and we watch the CTP/RC/Beta reports to make sure there are no show-stoppers, and fix what we find. And it’s not just “big” changes you need to worry about – a simple change in one line of code can have a massive effect. I know, I know – you’ve possibly upgraded an RC or CTP to the RTM version and it worked “just fine”. But hear this tale: I’ve dealt with someone who faced this exact situation in SQL Server 2008. They upgraded (which is clearly prohibited in the documentation) from a CTP to the RTM version over a year ago. Everything was working fine. But then…one day they had an issue. Couldn’t fix it themselves, we took a look, days went by, and we finally had to call in the big guns for support. Turns out, the upgrade was the problem. So we had to come up with some elaborate schemes to get the system migrated over while they were in production. This was painful for everyone involved. So the answer is still no. Just don’t do it. There is one caveat to this story – if you are a “TAP” customer (you’ll know if you are), we help you move from the CTP products to RTM, but that’s a special case that we track carefully and send along special instructions and tools to help you along. That level of effort isn’t possible on a large scale, so it’s not just a magic tool that we run to upgrade from CTP to RTM. So again, unless you’re a TAP customer, it’s a no-no. Share this post: email it! | bookmark it! | digg it! | reddit! | kick it! | live it!

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• Damaged external NTFS hard disk

  - by Thanos

  A few days ago, I used my external hard disk (a 2TB Seagate) in order to transfer some files on Windows Vista. During that, I noticed some malfunctions on my system (it was running too slow, Windows Explorer crashed). When Explorer crashed, file transportation stopped. I was afraid, but I tried to access my files and it seemed to be working. I tried to open a movie (from the external disk) but it couldn't load. I thought of restarting, but this took sooo long... So I unplugged the hard disk and at that time it managed to shut down. I logged on to Windows Vista but the hard disk couldn't be mounted. I plugged it but nothing happened. I unplugged it and I heard this specific sound that notifies that something has been unplugged. I thought of logging to Ubuntu 10.04 and see what I can do. I plugged the hard disk, but I couldn't see it. I opened GParted but I couldn't see it either. I tried with Disc Utility and there it was! I tried to mount it but a got an error message stating that an error occured with Windows, there is a file (0,0) that has problem or something like that. It suggested to log into Windows and run chkdsk /f and reboot twice. The thing is that I am somehow afraid to do so because I don't really know the impact on that. Plus I don't trust doing even a check on Vista... I finally risked it and I typed chkdsk/f on a cmd. I cannot, however, actually run it because I don't have admin privileges. So from search I found chkdsk, I right cliked and selected “run as administrator”. It run but I got a message like NTFS file system. It should check at the coming restart. At that point I am mistaken. I thought that f meant F but this is not the case here... Does anyone have any suggestions and advice?

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• What is a useful pattern to maintaining an object state in a one to many relationship?

  - by ahenderson

  I am looking for a design for my application, here are the players(classes) involved. struct Transform { // Uses a matrix to transform the position. // Also acts acts as the state of a Dialog. Position transform(Position p); //other methods. }; struct Dialog { // There are multiple dialog for the user to transform the output. Transform& t; void ChangeTranformation(){t.rotate(360);} } struct Algorithm { //gives us a position based on an implementation. For example this can return points on a circle or line. Transform& t; Position m_p; Dialog& d; Position GetCurrentPosition(){ return t.transform(m_p);} //other methods. } Properties I need: Each algorithms has one dialog and each dialog can have many algorithms associated with it. When the user selects an algorithm a dialog associated with that algorithm is displayed. If the user selects a different algorithm then re-selects back the state is restored in the dialog. Basically I want a good design pattern to maintain the state of the dialog given that many algorithms use it and they can be switched back and forth. Does anyone have any suggestions? Here is a use case: Dialog1 has a single edit box to control the radius. Algorithm1 generates points on a unit circle. Algorithm2 is the same as Algorithm1. The user has selected Algorithm1 and entered 2 into the edit box. This will generate points on a circle of radius 2. The user then selects Algorithm2 and enters 10 into the edit box of Dialog1. This will generate points on a circle of radius 10. Finally Algorithm1 is selected again. The edit box of Dialog1 should show 2 and points on a circle of radius 2 should be generated.

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• Access Control Service v2: Registering Web Identities in your Applications [code]

  - by Your DisplayName here!

  You can download the full solution here. The relevant parts in the sample are: Configuration I use the standard WIF configuration with passive redirect. This kicks automatically in, whenever authorization fails in the application (e.g. when the user tries to get to an area the requires authentication or needs registration). Checking and transforming incoming claims In the claims authentication manager we have to deal with two situations. Users that are authenticated but not registered, and registered (and authenticated) users. Registered users will have claims that come from the application domain, the claims of unregistered users come directly from ACS and get passed through. In both case a claim for the unique user identifier will be generated. The high level logic is as follows: public override IClaimsPrincipal Authenticate( string resourceName, IClaimsPrincipal incomingPrincipal) {     // do nothing if anonymous request     if (!incomingPrincipal.Identity.IsAuthenticated)     {         return base.Authenticate(resourceName, incomingPrincipal);     } string uniqueId = GetUniqueId(incomingPrincipal);     // check if user is registered     RegisterModel data;     if (Repository.TryGetRegisteredUser(uniqueId, out data))     {         return CreateRegisteredUserPrincipal(uniqueId, data);     }     // authenticated by ACS, but not registered     // create unique id claim     incomingPrincipal.Identities[0].Claims.Add( new Claim(Constants.ClaimTypes.Id, uniqueId));     return incomingPrincipal; } User Registration The registration page is handled by a controller with the [Authorize] attribute. That means you need to authenticate before you can register (crazy eh? ;). The controller then fetches some claims from the identity provider (if available) to pre-fill form fields. After successful registration, the user is stored in the local data store and a new session token gets issued. This effectively replaces the ACS claims with application defined claims without requiring the user to re-signin. Authorization All pages that should be only reachable by registered users check for a special application defined claim that only registered users have. You can nicely wrap that in a custom attribute in MVC: [RegisteredUsersOnly] public ActionResult Registered() {     return View(); } HTH

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• Is return-type-(only)-polymorphism in Haskell a good thing?

  - by dainichi

  One thing that I've never quite come to terms with in Haskell is how you can have polymorphic constants and functions whose return type cannot be determined by their input type, like class Foo a where foo::Int -> a Some of the reasons that I do not like this: Referential transparency: "In Haskell, given the same input, a function will always return the same output", but is that really true? read "3" return 3 when used in an Int context, but throws an error when used in a, say, (Int,Int) context. Yes, you can argue that read is also taking a type parameter, but the implicitness of the type parameter makes it lose some of its beauty in my opinion. Monomorphism restriction: One of the most annoying things about Haskell. Correct me if I'm wrong, but the whole reason for the MR is that computation that looks shared might not be because the type parameter is implicit. Type defaulting: Again one of the most annoying things about Haskell. Happens e.g. if you pass the result of functions polymorphic in their output to functions polymorphic in their input. Again, correct me if I'm wrong, but this would not be necessary without functions whose return type cannot be determined by their input type (and polymorphic constants). So my question is (running the risk of being stamped as a "discussion quesion"): Would it be possible to create a Haskell-like language where the type checker disallows these kinds of definitions? If so, what would be the benefits/disadvantages of that restriction? I can see some immediate problems: If, say, 2 only had the type Integer, 2/3 wouldn't type check anymore with the current definition of /. But in this case, I think type classes with functional dependencies could come to the rescue (yes, I know that this is an extension). Furthermore, I think it is a lot more intuitive to have functions that can take different input types, than to have functions that are restricted in their input types, but we just pass polymorphic values to them. The typing of values like [] and Nothing seems to me like a tougher nut to crack. I haven't thought of a good way to handle them. I doubt I am the first person to have had thoughts like these. Does anybody have links to good discussions about this Haskell design decision and the pros/cons of it?

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• MySQL Connector/Net 6.6.4 RC1 has been released

  - by fernando

  MySQL Connector/Net 6.6.4, a new version of the all-managed .NET driver  for MySQL has been released.  This is the Release Candidate intended to introduce users to the new features in the release.  This release is feature complete it should be stable enough for users to understand the new features and how we expect them to work.  As is the case with all non-GA releases, it should not be used in any production environment.  It is appropriate for use with MySQL server versions 5.0-5.6 It is now available in source and binary form from http://dev.mysql.com/downloads/connector/net/#downloads and mirror sites (note that not all mirror sites may be up to date at this point-if you can't find this version on some mirror, please try again later or choose another download site.) The 6.6 version of MySQL Connector/Net brings the following new features:   * Stored routine debugging   * Entity Framework 4.3 Code First support   * Pluggable authentication (now third parties can plug new authentications mechanisms into the driver).   * Full Visual Studio 2012 support: everything from Server Explorer to Intellisense&  the Stored Routine debugger. The following specific fixes are addressed in this version: - Fixed Entity Framework + mysql connector/net in partial trust throws exceptions (MySql bug #65036, Oracle bug #14668820). - Added support in Parser for Datetime and Time types with precision when using Server 5.6 (No bug Number). - Fix for bug TIMESTAMP values are mistakenly represented as DateTime with Kind = Local (Mysql bug #66964, Oracle bug #14740705). The release is available to download athttp://dev.mysql.com/downloads/connector/net/6.6.html Documentation ------------------------------------- You can view current Connector/Net documentation at http://dev.mysql.com/doc/refman/5.5/en/connector-net.html For specific topics: Stored Routine Debugger:http://dev.mysql.com/doc/refman/5.5/en/connector-net-visual-studio-debugger.html Authentication plugin:http://dev.mysql.com/doc/refman/5.5/en/connector-net-programming-authentication-user-plugin.html You can find our team blog at http://blogs.oracle.com/MySQLOnWindows. You can also post questions on our forums at http://forums.mysql.com/. Enjoy and thanks for the support!

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• How to create a JMS durable subscriber in WebLogic Server?

  - by lmestre

  WebLogic Server Provides a set of examples that are very helpful to get started with Weblogic ServerHere you can check how to install the examples:http://docs.oracle.com/cd/E23943_01/doc.1111/e14142/prepare.htmAfter you have installed the examples, you can find the example you want to review, in this case TopicReceive, here:wlserver_10.3/samples/server/examples/src/examples/jms/topicTo review details of the specific example, you can open:wlserver_10.3/samples/server/examples/src/examples/jms/topic/instructions.htmlTo create a Durable Subscriber, you can just set the client ID  and invoke createDurableSubscriber instead of calling createSubscriber, i.e.:    tconFactory = (TopicConnectionFactory)       PortableRemoteObject.narrow(ctx.lookup(JMS_FACTORY),                                   TopicConnectionFactory.class);    tcon = tconFactory.createTopicConnection();    //Set Client ID for this Durable Subscriber    tcon.setClientID("GT2");    tsession = tcon.createTopicSession(false, Session.AUTO_ACKNOWLEDGE);    topic = (Topic)       PortableRemoteObject.narrow(ctx.lookup(topicName),                                   Topic.class);    // Create Durable Subscription    tsubscriber = tsession.createDurableSubscriber(topic, "Test");    tsubscriber.setMessageListener(this);    tcon.start(); Enjoy!   You can read more about this here:http://docs.oracle.com/cd/E23943_01/web.1111/e13727/advpubsub.htm#CHDEBABChttp://docs.oracle.com/cd/E23943_01/web.1111/e13727/manage_apps.htm#i1097671    http://docs.oracle.com/cd/E23943_01/apirefs.1111/e13943/WebLogic.Messaging.ISession.CreateDurableSubscriber_overload_2.html

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• How / Where can I host my Java web application? [closed]

  - by Huliax

  Possible Duplicate: How to find web hosting that meets my requirements? In case you want to skip to the crux of my inquiry just read the bold type. I just finished my CS degree (at 39 years old :-)). For my final project I designed and built a system that can provide local positioning / location awareness to mobile wifi devices (only have Android client thus far). The server receives data from clients, processes it, and responds to the clients with a messages containing information about their respective locations. I would like to continue the project (perhaps release as open source but that is a different discussion). Thus far my server application has been running on the CS department's hardware where I could pretty much do whatever I wanted. I'm getting kicked off that system in a few weeks so I have to find a new home for my server application. I need a host that will let me run my Java server (along w/ mySQL db) -- preferably on the cheap since I haven't yet got a job. I have very little experience with the "real world" of web development / hosting. I'm having trouble figuring out what kind of hosting service will let me run my application as is. If that turns out to be a tall order then I need to know what my options are for changing thing so that I can get up and running with some hosting. As an aside, I'm also researching whether or not I should rewrite this in a different language. Trying to figure out if there is a substantially better (for whatever reason) one for what I'm doing. This might also potentially have a bearing on my hosting needs. One possibility is to write the server in something more widely accepted by hosting services. I have been searching for answers to my question and haven't found quite what I'm looking for. Part of the problem might be that I don't know exactly what terminology to use. If there is a good answer to this question elsewhere please feel free to point me towards it. Thanks for help / advice.

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• rotating an object on an arc

  - by gardian06

  I am trying to get a turret to rotate on an arc, and have hit a wall. I have 8 possible starting orientations for the turrets, and want them to rotate on a 90 degree arc. I currently take the starting rotation of the turret, and then from that derive the positive, and negative boundary of the arc. because of engine restrictions (Unity) I have to do all of my tests against a value which is between [0,360], and due to numerical precision issues I can not test against specific values. I would like to write a general test without having to go in, and jury rig cases //my current test is: // member variables public float negBound; public float posBound; // found in Start() function (called immediately after construction) // eulerAngles.y is the the degree measure of the starting y rotation negBound = transform.eulerAngles.y-45; posBound = transform.eulerAngles.y+45; // insure that values are within bounds if(negBound<0){ negBound+=360; }else if(posBound>360){ posBound-=360; } // called from Update() when target not in firing line void Rotate(){ // controlls what direction if(transform.eulerAngles.y>posBound){ dir = -1; } else if(transform.eulerAngles.y < negBound){ dir = 1; } // rotate object } follows is a table of values for my different cases (please excuse my force formatting) read as base is the starting rotation of the turret, neg is the negative boundry, pos is the positive boundry, range is the acceptable range of values, and works is if it performs as expected with the current code. |base-|-neg-|-pos--|----------range-----------|-works-| |---0---|-315-|--45--|-315-0,0-45----------|----------| |--45--|---0---|--90--|-0-45,54-90----------|----x----| |-135-|---90--|-180-|-90-135,135-180---|----x----| |-180-|--135-|-225-|-135-180,180-225-|----x----| |-225-|--180-|-270-|-180-225,225-270-|----x----| |-270-|--225-|-315-|-225-270,270-315-|----------| |-315-|--270-|---0---|--270-315,315-0---|----------| I will need to do all tests from derived, or stored values, but can not figure out how to get all of my cases to work simultaneously. //I attempted to concatenate the 2 tests: if((transform.eulerAngles.y>posBound)&&(transform.eulerAngles.y < negBound)){ dir *= -1; } this caused only the first case to be successful // I attempted to store a opposite value, and do a void Rotate(){ // controlls what direction if((transform.eulerAngles.y > posBound)&&(transform.eulerAngles.y<oposite)){ dir = -1; } else if((transform.eulerAngles.y < negBound)&&(transform.eulerAngles.y>oposite)){ dir = 1; } // rotate object } this causes the opposite situation as indicated on the table. What am I missing here?

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• Is this a pattern? Should it be?

  - by Arkadiy

  The following is more of a statement than a question - it describes something that may be a pattern. The question is: is this a known pattern? Or, if it's not, should it be? I've had a situation where I had to iterate over two dissimilar multi-layer data structures and copy information from one to the other. Depending on particular use case, I had around eight different kinds of layers, combined in about eight different combinations: A-B-C B-C A-C D-E A-D-E and so on After a few unsuccessful attempts to factor out the repetition of per-layer iteration code, I realized that the key difficulty in this refactoring was the fact that the bottom level needed access to data gathered at higher levels. To explicitly accommodate this requirement, I introduced IterationContext class with a number of get() and set() methods for accumulating the necessary information. In the end, I had the following class structure: class Iterator { virtual void iterateOver(const Structure &dataStructure1, IterationContext &ctx) const = 0; }; class RecursingIterator : public Iterator { RecursingIterator(const Iterator &below); }; class IterateOverA : public RecursingIterator { virtual void iterateOver(const Structure &dataStructure1, IterationContext &ctx) const { // Iterate over members in dataStructure1 // locate corresponding item in dataStructure2 (passed via context) // and set it in the context // invoke the sub-iterator }; class IterateOverB : public RecursingIterator { virtual void iterateOver(const Structure &dataStructure1, IterationContext &ctx) const { // iterate over members dataStructure2 (form context) // set dataStructure2's item in the context // locate corresponding item in dataStructure2 (passed via context) // invoke the sub-iterator }; void main() { class FinalCopy : public Iterator { virtual void iterateOver(const Structure &dataStructure1, IterationContext &ctx) const { // copy data from structure 1 to structure 2 in the context, // using some data from higher levels as needed } } IterationContext ctx(dateStructure2); IterateOverA(IterateOverB(FinalCopy())).iterate(dataStructure1, ctx); } It so happens that dataStructure1 is a uniform data structure, similar to XML DOM in that respect, while dataStructure2 is a legacy data structure made of various structs and arrays. This allows me to pass dataStructure1 outside of the context for convenience. In general, either side of the iteration or both sides may be passed via context, as convenient. The key situation points are: complicated code that needs to be invoked in "layers", with multiple combinations of layer types possible at the bottom layer, the information from top layers needs to be visible. The key implementation points are: use of context class to access the data from all levels of iteration complicated iteration code encapsulated in implementation of pure virtual function two interfaces - one aware of underlying iterator, one not aware of it. use of const & to simplify the usage syntax.

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• Unintentional run-in with C# thread concurrency

  - by geekrutherford

  For the first time today we began conducting load testing on a ASP.NET application already in production. Obviously you would normally want to load test prior to releasing to a production environment, but that isn't the point here.   We ran a test which simulated 5 users hitting the application doing the same actions simultaneously. The first few pages visited seemed fine and then things just hung for a while before the test failed. While the test was running I was viewing the performance counters on the server noting that the CPU was consistently pegged at 100% until the testing tool gave up.   Fortunately the application logs all exceptions including those unhandled to the database (thanks to log4net). I checked the log and low and behold the error was:   System.ArgumentException: An item with the same key has already been added. (The rest of the stack trace intentionally omitted)   Since the code was running with debug on the line number where the exception occured was also provided. I began inspecting the code and almost immediately it hit me, the section of code responsible for the exception is trying to initialize a static class. My next question was how is this code being hit multiple times when I have a rudimentary check already in place to prevent this kind of thing (i.e. a check on a public variable of the static class before entering the initializing routine). The answer...the check fails because the value is not set before other threads have already made it through.   Not being one who consistently works with threading I wasn't quite sure how to handle this problem. Fortunately a co-worker recalled having to lock a section of code in the past but couldn't recall exactly how. After a quick search on Google the solution is as follows:   Object objLock = new Object(); lock(objLock) { //logic requiring lock }   The lock statement takes an object and tells the .NET runtime that the current thread has exclusive access while the code within brackets is executing. Once the code completes, the lock is released for another thread to utilize.   In my case, I only need to execute the inner code once to initialize my static class. So within the brackets I have a check on a public variable to prevent it from being initialized again.

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• IXRepository and test problems

  - by Ridermansb

  Recently had a doubt about how and where to test repository methods. Let the following situation: I have an interface IRepository like this: public interface IRepository<T> where T: class, IEntity { IQueryable<T> Query(Expression<Func<T, bool>> expression); // ... Omitted } And a generic implementation of IRepository public class Repository<T> : IRepository<T> where T : class, IEntity { public IQueryable<T> Query(Expression<Func<T, bool>> expression) { return All().Where(expression).AsQueryable(); } } This is an implementation base that can be used by any repository. It contains the basic implementation of my ORM. Some repositories have specific filters, in which case we will IEmployeeRepository with a specific filter: public interface IEmployeeRepository : IRepository<Employee> { IQueryable<Employee> GetInactiveEmployees(); } And the implementation of IEmployeeRepository: public class EmployeeRepository : Repository<Employee>, IEmployeeRepository // TODO: I have a dependency with ORM at this point in Repository<Employee>. How to solve? How to test the GetInactiveEmployees method { public IQueryable<Employee> GetInactiveEmployees() { return Query(p => p.Status != StatusEmployeeEnum.Active || p.StartDate < DateTime.Now); } } Questions Is right to inherit Repository<Employee>? The goal is to reuse code once all implementing IRepository already been made. If EmployeeRepository inherit only IEmployeeRepository, I have to literally copy and paste the code of Repository<T>. In our example, in EmployeeRepository : Repository<Employee> our Repository lies in our ORM layer. We have a dependency here with our ORM impossible to perform some unit test. How to create a unit test to ensure that the filter GetInactiveEmployees return all Employees in which the Status != Active and StartDate < DateTime.Now. I can not create a Fake/Mock of IEmployeeRepository because I would be testing? Need to test the actual implementation of GetInactiveEmployees. The complete code can be found on Github

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• WebLogic Partner Community Newsletter September 2012

  - by JuergenKress

  Dear WebLogic partner community member Happy Birthday to our WebLogic partner Community! We launched the community a year ago, it is growing fast with almost 1,000 members and with a significant impact in our business. The WebLogic partner revenue grew significant last fiscal year. I would like to thank you for your contribution. It is indeed a great opportunity for your WebLogic service revenue, like consulting, implementation or training. There will be thousands of opportunities at our joint customer base, like iAs to WebLogic migration, J2EE platform consolidation or private clouds. We will continue to highlight these opportunities in our newsletter and offer you campaign kits. Please feel free to let us know if you are interested. I would also recommend you to give us your feedback in our WebLogic Partner Community Survey 2012! Your feedback is very important for us. We continue to offer free WebLogic 12c Bootcamps across Europe. Please make sure you register asap for your local training! In addition to this we plan to offer Exalogic 2.01 Bootcamp. If you are interested to attend it then please add your details to our wiki. Our ExaLogic kit is updated with ExaLogic 2.01 ppt & training & Installation check-list & tips & Web tier roadmap. In case you want to learn more about ExaLogic, please visit Qualogy virtual demo center. We have not only released the latest version of Tuxedo 12c but Andrejus also made a Performance Audit Tool - Runtime Diagnosis for ADF Applications which is available now. We uploaded the latest WebLogic 12c and Glassfish ppt presentation for your customer meetings to the WebLogic Community Workspace (WebLogic Community membership required). Are you ready and prepared for Oracle Open World 2012? Make sure you read our tips and enjoy the conference! WebLogic Server 11gR1 Interactive Quick Reference is a wonderful online overview. Make sure you do not miss it! If you want to try WebLogic why not in the Oracle Cloud - Java Cloud Service. Our Java Guru Adam Bien published a new book Real World Java EE Patterns. If you use Java on your machine, Please make sure that you update your Java SE. Jürgen Kress Oracle WebLogic Partner Adoption EMEA To read the newsletter please visit http://tinyurl.com/WebLogicnewsSeptember2012 (OPN Account required) To become a member of the WebLogic Partner Community please register at http://www.oracle.com/partners/goto/wls-emea ( OPN account required). If you need support with your account please contact the Oracle Partner Business Center. Blog Twitter LinkedIn Mix Forum Wiki Technorati Tags: WebLogic Community newsletter,newsletter,WebLogic,WebLogic Community,Oracle,OPN,Jürgen Kress

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• Does OO, TDD, and Refactoring to Smaller Functions affect Speed of Code?

  - by Dennis

  In Computer Science field, I have noticed a notable shift in thinking when it comes to programming. The advice as it stands now is write smaller, more testable code refactor existing code into smaller and smaller chunks of code until most of your methods/functions are just a few lines long write functions that only do one thing (which makes them smaller again) This is a change compared to the "old" or "bad" code practices where you have methods spanning 2500 lines, and big classes doing everything. My question is this: when it call comes down to machine code, to 1s and 0s, to assembly instructions, should I be at all concerned that my class-separated code with variety of small-to-tiny functions generates too much extra overhead? While I am not exactly familiar with how OO code and function calls are handled in ASM in the end, I do have some idea. I assume that each extra function call, object call, or include call (in some languages), generate an extra set of instructions, thereby increasing code's volume and adding various overhead, without adding actual "useful" code. I also imagine that good optimizations can be done to ASM before it is actually ran on the hardware, but that optimization can only do so much too. Hence, my question -- how much overhead (in space and speed) does well-separated code (split up across hundreds of files, classes, and methods) actually introduce compared to having "one big method that contains everything", due to this overhead? UPDATE for clarity: I am assuming that adding more and more functions and more and more objects and classes in a code will result in more and more parameter passing between smaller code pieces. It was said somewhere (quote TBD) that up to 70% of all code is made up of ASM's MOV instruction - loading CPU registers with proper variables, not the actual computation being done. In my case, you load up CPU's time with PUSH/POP instructions to provide linkage and parameter passing between various pieces of code. The smaller you make your pieces of code, the more overhead "linkage" is required. I am concerned that this linkage adds to software bloat and slow-down and I am wondering if I should be concerned about this, and how much, if any at all, because current and future generations of programmers who are building software for the next century, will have to live with and consume software built using these practices. UPDATE: Multiple files I am writing new code now that is slowly replacing old code. In particular I've noted that one of the old classes was a ~3000 line file (as mentioned earlier). Now it is becoming a set of 15-20 files located across various directories, including test files and not including PHP framework I am using to bind some things together. More files are coming as well. When it comes to disk I/O, loading multiple files is slower than loading one large file. Of course not all files are loaded, they are loaded as needed, and disk caching and memory caching options exist, and yet still I believe that loading multiple files takes more processing than loading a single file into memory. I am adding that to my concern.

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• Understanding the SQL Server 2008 R2 Installation Center

  - by Enrique Lima

  What is available to us through those links?  Have you taken the time to explore and identify what could be useful to you? One of many gems that has come to my attention is the possibility of provisioning SQL Server to work in an image based environment (hint: Virtualization Template perhaps?!?).   Planning: Includes requirements information, documentation, how to guides, online documentation installation and other tools. Among the other tools you will find the System Configuration checker and The Upgrade Advisor. Both tools very important to ensure your deployment and installation would be successful.     Installation:  This sections focuses on getting installations going, from standalone to cluster when it comes to new instances.  Add new nodes to an existing cluster, and also perform upgrades (in this case to SQL Server 2008 R2).  Also part of this is the option to find updates available.   Maintenance: We find in this section, options that will assist us in tasks like repairing corrupt installations to removing nodes from a cluster. An option that is interesting (and we should discuss benefits later in another post) is to be able to do an Edition Upgrade, this is a feature expansion and addition based on your product installation (Developer to Enterprise, for example)   Tools:  From the System Configuration Checker to identify readiness for deployment in a successful manner, to being able to report on features installed.  And being able to run upgrades of existing packages developed in the 2005 offering to the 2008 R2 release for SSIS.   Resources: Useful and essential links to gather information and guidance.   Advanced: Here is where it gets interesting.  I break this down into 3 main groups: Installation Automation: When you install SQL Server there is a configuration file that gets dropped (ConfigurationFile.ini) that would allow for you to perform automated installations.  There are switches and options that go with this to have that process working. Cluster configuration for Sysprep: Create images that are cluster ready, 2 options, start the prep work, and then the complete once at the final destination. Stand-alone configuration for Sysprep:  Like the clustering counterpart, 2 options, prep and complete.  Giving you the option to create standard templates for your SQL Server deployments. I find it fitting that the 3 topics listed here should (and will) be additional topics I will discuss.   Options: Very clear and specific about what this means. Select the Processor Type or the Installation Media Root Path.

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• Lazy Processing of Streams

  - by Giorgio

  I have the following problem scenario: I have a text file and I have to read it and split it into lines. Some lines might need to be dropped (according to criteria that are not fixed). The lines that are not dropped must be parsed into some predefined records. Records that are not valid must be dropped. Duplicate records may exist and, in such a case, they are consecutive. If duplicate / multiple records exist, only one item should be kept. The remaining records should be grouped according to the value contained in one field; all records belonging to the same group appear one after another (e.g. AAAABBBBCCDEEEFF and so on). The records of each group should be numbered (1, 2, 3, 4, ...). For each group the numbering starts from 1. The records must then be saved somewhere / consumed in the same order as they were produced. I have to implement this in Java or C++. My first idea was to define functions / methods like: One method to get all the lines from the file. One method to filter out the unwanted lines. One method to parse the filtered lines into valid records. One method to remove duplicate records. One method to group records and number them. The problem is that the data I am going to read can be too big and might not fit into main memory: so I cannot just construct all these lists and apply my functions one after the other. On the other hand, I think I do not need to fit all the data in main memory at once because once a record has been consumed all its underlying data (basically the lines of text between the previous record and the current record, and the record itself) can be disposed of. With the little knowledge I have of Haskell I have immediately thought about some kind of lazy evaluation, in which instead of applying functions to lists that have been completely computed, I have different streams of data that are built on top of each other and, at each moment, only the needed portion of each stream is materialized in main memory. But I have to implement this in Java or C++. So my question is which design pattern or other technique can allow me to implement this lazy processing of streams in one of these languages.

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• When attaching AI to a vehicle should I define all steps or try Line of Sight?

  - by ThorDivDev

  This problem is related to an intersection simulation I am building for university. I will try to make it as general as possible. I am trying to assign AI to a vehicle using the JMonkeyEngine platform. AIGama_JmonkeyEngine explains that if you wish to create a car that follows a path you can define the path in steps. If there was no physics attached whatsoever then all you need to do is define the x,y,z values of where you want the object to appear in all subsequent steps. I am attaching the vehicleControl that implements jBullet. In this case the author mentions that I would need to define the steering and accelerating behaviors at each step. I was trying to use ghost controls that represented waypoints and when on colliding the car would decide what to do next like stopping at a red light. This didn't work so well. Car doesn't face right. public void update(float tpf) { Vector3f currentPos = aiVehicle.getPhysicsLocation(); Vector3f baseforwardVector = currentPos.clone(); Vector3f forwardVector; Vector3f subsVector; if (currentState == ObjectState.Running) { aiVehicle.accelerate(-800); } else if (currentState == ObjectState.Seeking) { baseforwardVector = baseforwardVector.normalize(); forwardVector = aiVehicle.getForwardVector(baseforwardVector); subsVector = pointToSeek.subtract(currentPos.clone()); System.out.printf("baseforwardVector: %f, %f, %f\n", baseforwardVector.x, baseforwardVector.y, baseforwardVector.z); System.out.printf("subsVector: %f, %f, %f\n", subsVector.x, subsVector.y, subsVector.z); System.out.printf("ForwardVector: %f, %f, %f\n", forwardVector.x, forwardVector.y, forwardVector.z); if (pointToSeek != null && pointToSeek.x + 3 >= currentPos.x && pointToSeek.x - 3 <= currentPos.x) { aiVehicle.steer(0.0f); aiVehicle.accelerate(-40); } else if (pointToSeek != null && pointToSeek.x > currentPos.x) { aiVehicle.steer(-0.5f); aiVehicle.accelerate(-40); } else if (pointToSeek != null && pointToSeek.x < currentPos.x) { aiVehicle.steer(0.5f); aiVehicle.accelerate(-40); } } else if (currentState == ObjectState.Stopped) { aiVehicle.accelerate(0); aiVehicle.brake(40); } }

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• How should game objects be aware of each other?

  - by Jefffrey

  I find it hard to find a way to organize game objects so that they are polymorphic but at the same time not polymorphic. Here's an example: assuming that we want all our objects to update() and draw(). In order to do that we need to define a base class GameObject which have those two virtual pure methods and let polymorphism kicks in: class World { private: std::vector<GameObject*> objects; public: // ... update() { for (auto& o : objects) o->update(); for (auto& o : objects) o->draw(window); } }; The update method is supposed to take care of whatever state the specific class object needs to update. The fact is that each objects needs to know about the world around them. For example: A mine needs to know if someone is colliding with it A soldier should know if another team's soldier is in proximity A zombie should know where the closest brain, within a radius, is For passive interactions (like the first one) I was thinking that the collision detection could delegate what to do in specific cases of collisions to the object itself with a on_collide(GameObject*). Most of the the other informations (like the other two examples) could just be queried by the game world passed to the update method. Now the world does not distinguish objects based on their type (it stores all object in a single polymorphic container), so what in fact it will return with an ideal world.entities_in(center, radius) is a container of GameObject*. But of course the soldier does not want to attack other soldiers from his team and a zombie doesn't case about other zombies. So we need to distinguish the behavior. A solution could be the following: void TeamASoldier::update(const World& world) { auto list = world.entities_in(position, eye_sight); for (const auto& e : list) if (auto enemy = dynamic_cast<TeamBSoldier*>(e)) // shoot towards enemy } void Zombie::update(const World& world) { auto list = world.entities_in(position, eye_sight); for (const auto& e : list) if (auto enemy = dynamic_cast<Human*>(e)) // go and eat brain } but of course the number of dynamic_cast<> per frame could be horribly high, and we all know how slow dynamic_cast can be. The same problem also applies to the on_collide(GameObject*) delegate that we discussed earlier. So what it the ideal way to organize the code so that objects can be aware of other objects and be able to ignore them or take actions based on their type?

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