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• Using Delegates in C# (Part 1)

  - by rajbk

  This post provides a very basic introduction of delegates in C#. Part 2 of this post can be read here. A delegate is a class that is derived from System.Delegate.  It contains a list of one or more methods called an invocation list. When a delegate instance is “invoked” with the arguments as defined in the signature of the delegate, each of the methods in the invocation list gets invoked with the arguments. The code below shows example with static and instance methods respectively: Static Methods 1: using System; 2: using System.Linq; 3: using System.Collections.Generic; 4: 5: public delegate void SayName(string name); 6: 7: public class Program 8: { 9: [STAThread] 10: static void Main(string[] args) 11: { 12: SayName englishDelegate = new SayName(SayNameInEnglish); 13: SayName frenchDelegate = new SayName(SayNameInFrench); 14: SayName combinedDelegate =(SayName)Delegate.Combine(englishDelegate, frenchDelegate); 15: 16: combinedDelegate.Invoke("Tom"); 17: Console.ReadLine(); 18: } 19: 20: static void SayNameInFrench(string name) { 21: Console.WriteLine("J'ai m'appelle " + name); 22: } 23: 24: static void SayNameInEnglish(string name) { 25: Console.WriteLine("My name is " + name); 26: } 27: } We have declared a delegate of type SayName with return type of void and taking an input parameter of name of type string. On line 12, we create a new instance of this delegate which refers to a static method - SayNameInEnglish.  SayNameInEnglish has the same return type and parameter list as the delegate declaration.  Once a delegate is instantiated, the instance will always refer to the same target. Delegates are immutable. On line 13, we create a new instance of the delegate but point to a different static method. As you may recall, a delegate instance encapsulates an invocation list. You create an invocation list by combining delegates using the Delegate.Combine method (there is an easier syntax as you will see later). When two non null delegate instances are combined, their invocation lists get combined to form a new invocation list. This is done in line 14.  On line 16, we invoke the delegate with the Invoke method and pass in the required string parameter. Since the delegate has an invocation list with two entries, each of the method in the invocation list is invoked. If an unhandled exception occurs during the invocation of one of these methods, the exception gets bubbled up to the line where the invocation was made (line 16). If a delegate is null and you try to invoke it, you will get a System.NullReferenceException. We see the following output when the method is run: My name is TomJ'ai m'apelle Tom Instance Methods The code below outputs the same results as before. The only difference here is we are creating delegates that point to a target object (an instance of Translator) and instance methods which have the same signature as the delegate type. The target object can never be null. We also use the short cut syntax += to combine the delegates instead of Delegate.Combine. 1: public delegate void SayName(string name); 2: 3: public class Program 4: { 5: [STAThread] 6: static void Main(string[] args) 7: { 8: Translator translator = new Translator(); 9: SayName combinedDelegate = new SayName(translator.SayNameInEnglish); 10: combinedDelegate += new SayName(translator.SayNameInFrench); 11:  12: combinedDelegate.Invoke("Tom"); 13: Console.ReadLine(); 14: } 15: } 16: 17: public class Translator { 18: public void SayNameInFrench(string name) { 19: Console.WriteLine("J'ai m'appelle " + name); 20: } 21: 22: public void SayNameInEnglish(string name) { 23: Console.WriteLine("My name is " + name); 24: } 25: } A delegate can be removed from a combination of delegates by using the –= operator. Removing a delegate from an empty list or removing a delegate that does not exist in a non empty list will not result in an exception. Delegates are invoked synchronously using the Invoke method. We can also invoke them asynchronously using the BeginInvoke and EndInvoke methods which are compiler generated.

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• How to make creating viewmodels at runtime less painful

  - by Mr Happy

  I apologize for the long question, it reads a bit as a rant, but I promise it's not! I've summarized my question(s) below In the MVC world, things are straightforward. The Model has state, the View shows the Model, and the Controller does stuff to/with the Model (basically), a controller has no state. To do stuff the Controller has some dependencies on web services, repository, the lot. When you instantiate a controller you care about supplying those dependencies, nothing else. When you execute an action (method on Controller), you use those dependencies to retrieve or update the Model or calling some other domain service. If there's any context, say like some user wants to see the details of a particular item, you pass the Id of that item as parameter to the Action. Nowhere in the Controller is there any reference to any state. So far so good. Enter MVVM. I love WPF, I love data binding. I love frameworks that make data binding to ViewModels even easier (using Caliburn Micro a.t.m.). I feel things are less straightforward in this world though. Let's do the exercise again: the Model has state, the View shows the ViewModel, and the ViewModel does stuff to/with the Model (basically), a ViewModel does have state! (to clarify; maybe it delegates all the properties to one or more Models, but that means it must have a reference to the model one way or another, which is state in itself) To do stuff the ViewModel has some dependencies on web services, repository, the lot. When you instantiate a ViewModel you care about supplying those dependencies, but also the state. And this, ladies and gentlemen, annoys me to no end. Whenever you need to instantiate a ProductDetailsViewModel from the ProductSearchViewModel (from which you called the ProductSearchWebService which in turn returned IEnumerable<ProductDTO>, everybody still with me?), you can do one of these things: call new ProductDetailsViewModel(productDTO, _shoppingCartWebService /* dependcy */);, this is bad, imagine 3 more dependencies, this means the ProductSearchViewModel needs to take on those dependencies as well. Also changing the constructor is painful. call _myInjectedProductDetailsViewModelFactory.Create().Initialize(productDTO);, the factory is just a Func, they are easily generated by most IoC frameworks. I think this is bad because Init methods are a leaky abstraction. You also can't use the readonly keyword for fields that are set in the Init method. I'm sure there are a few more reasons. call _myInjectedProductDetailsViewModelAbstractFactory.Create(productDTO); So... this is the pattern (abstract factory) that is usually recommended for this type of problem. I though it was genius since it satisfies my craving for static typing, until I actually started using it. The amount of boilerplate code is I think too much (you know, apart from the ridiculous variable names I get use). For each ViewModel that needs runtime parameters you'll get two extra files (factory interface and implementation), and you need to type the non-runtime dependencies like 4 extra times. And each time the dependencies change, you get to change it in the factory as well. It feels like I don't even use a DI container anymore. (I think Castle Windsor has some kind of solution for this [with it's own drawbacks, correct me if I'm wrong]). do something with anonymous types or dictionary. I like my static typing. So, yeah. Mixing state and behavior in this way creates a problem which don't exist at all in MVC. And I feel like there currently isn't a really adequate solution for this problem. Now I'd like to observe some things: People actually use MVVM. So they either don't care about all of the above, or they have some brilliant other solution. I haven't found an in-depth example of MVVM with WPF. For example, the NDDD-sample project immensely helped me understand some DDD concepts. I'd really like it if someone could point me in the direction of something similar for MVVM/WPF. Maybe I'm doing MVVM all wrong and I should turn my design upside down. Maybe I shouldn't have this problem at all. Well I know other people have asked the same question so I think I'm not the only one. To summarize Am I correct to conclude that having the ViewModel being an integration point for both state and behavior is the reason for some difficulties with the MVVM pattern as a whole? Is using the abstract factory pattern the only/best way to instantiate a ViewModel in a statically typed way? Is there something like an in depth reference implementation available? Is having a lot of ViewModels with both state/behavior a design smell?

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• Polite busy-waiting with WRPAUSE on SPARC

  - by Dave

  Unbounded busy-waiting is an poor idea for user-space code, so we typically use spin-then-block strategies when, say, waiting for a lock to be released or some other event. If we're going to spin, even briefly, then we'd prefer to do so in a manner that minimizes performance degradation for other sibling logical processors ("strands") that share compute resources. We want to spin politely and refrain from impeding the progress and performance of other threads — ostensibly doing useful work and making progress — that run on the same core. On a SPARC T4, for instance, 8 strands will share a core, and that core has its own L1 cache and 2 pipelines. On x86 we have the PAUSE instruction, which, naively, can be thought of as a hardware "yield" operator which temporarily surrenders compute resources to threads on sibling strands. Of course this helps avoid intra-core performance interference. On the SPARC T2 our preferred busy-waiting idiom was "RD %CCR,%G0" which is a high-latency no-nop. The T4 provides a dedicated and extremely useful WRPAUSE instruction. The processor architecture manuals are the authoritative source, but briefly, WRPAUSE writes a cycle count into the the PAUSE register, which is ASR27. Barring interrupts, the processor then delays for the requested period. There's no need for the operating system to save the PAUSE register over context switches as it always resets to 0 on traps. Digressing briefly, if you use unbounded spinning then ultimately the kernel will preempt and deschedule your thread if there are other ready threads than are starving. But by using a spin-then-block strategy we can allow other ready threads to run without resorting to involuntary time-slicing, which operates on a long-ish time scale. Generally, that makes your application more responsive. In addition, by blocking voluntarily we give the operating system far more latitude regarding power management. Finally, I should note that while we have OS-level facilities like sched_yield() at our disposal, yielding almost never does what you'd want or naively expect. Returning to WRPAUSE, it's natural to ask how well it works. To help answer that question I wrote a very simple C/pthreads benchmark that launches 8 concurrent threads and binds those threads to processors 0..7. The processors are numbered geographically on the T4, so those threads will all be running on just one core. Unlike the SPARC T2, where logical CPUs 0,1,2 and 3 were assigned to the first pipeline, and CPUs 4,5,6 and 7 were assigned to the 2nd, there's no fixed mapping between CPUs and pipelines in the T4. And in some circumstances when the other 7 logical processors are idling quietly, it's possible for the remaining logical processor to leverage both pipelines. Some number T of the threads will iterate in a tight loop advancing a simple Marsaglia xor-shift pseudo-random number generator. T is a command-line argument. The main thread loops, reporting the aggregate number of PRNG steps performed collectively by those T threads in the last 10 second measurement interval. The other threads (there are 8-T of these) run in a loop busy-waiting concurrently with the T threads. We vary T between 1 and 8 threads, and report on various busy-waiting idioms. The values in the table are the aggregate number of PRNG steps completed by the set of T threads. The unit is millions of iterations per 10 seconds. For the "PRNG step" busy-waiting mode, the busy-waiting threads execute exactly the same code as the T worker threads. We can easily compute the average rate of progress for individual worker threads by dividing the aggregate score by the number of worker threads T. I should note that the PRNG steps are extremely cycle-heavy and access almost no memory, so arguably this microbenchmark is not as representative of "normal" code as it could be. And for the purposes of comparison I included a row in the table that reflects a waiting policy where the waiting threads call poll(NULL,0,1000) and block in the kernel. Obviously this isn't busy-waiting, but the data is interesting for reference. _table { border:2px black dotted; margin: auto; width: auto; } _tr { border: 2px red dashed; } _td { border: 1px green solid; } _table { border:2px black dotted; margin: auto; width: auto; } _tr { border: 2px red dashed; } td { background-color : #E0E0E0 ; text-align : right ; } th { text-align : left ; } td { background-color : #E0E0E0 ; text-align : right ; } th { text-align : left ; } Aggregate progress T = #worker threads Wait Mechanism for 8-T threadsT=1T=2T=3T=4T=5T=6T=7T=8 Park thread in poll() 32653347334833483348334833483348 no-op 415 831 124316482060249729303349 RD %ccr,%g0 "pause" 14262429269228623013316232553349 PRNG step 412 829 124616702092251029303348 WRPause(8000) 32443361333133483349334833483348 WRPause(4000) 32153308331533223347334833473348 WRPause(1000) 30853199322432513310334833483348 WRPause(500) 29173070315032223270330933483348 WRPause(250) 26942864294930773205338833483348 WRPause(100) 21552469262227902911321433303348

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• Cardinality Estimation Bug with Lookups in SQL Server 2008 onward

  - by Paul White

  Cost-based optimization stands or falls on the quality of cardinality estimates (expected row counts).  If the optimizer has incorrect information to start with, it is quite unlikely to produce good quality execution plans except by chance.  There are many ways we can provide good starting information to the optimizer, and even more ways for cardinality estimation to go wrong.  Good database people know this, and work hard to write optimizer-friendly queries with a schema and metadata (e.g. statistics) that reduce the chances of poor cardinality estimation producing a sub-optimal plan.  Today, I am going to look at a case where poor cardinality estimation is Microsoft’s fault, and not yours. SQL Server 2005 SELECT th.ProductID, th.TransactionID, th.TransactionDate FROM Production.TransactionHistory AS th WHERE th.ProductID = 1 AND th.TransactionDate BETWEEN '20030901' AND '20031231'; The query plan on SQL Server 2005 is as follows (if you are using a more recent version of AdventureWorks, you will need to change the year on the date range from 2003 to 2007): There is an Index Seek on ProductID = 1, followed by a Key Lookup to find the Transaction Date for each row, and finally a Filter to restrict the results to only those rows where Transaction Date falls in the range specified.  The cardinality estimate of 45 rows at the Index Seek is exactly correct.  The table is not very large, there are up-to-date statistics associated with the index, so this is as expected. The estimate for the Key Lookup is also exactly right.  Each lookup into the Clustered Index to find the Transaction Date is guaranteed to return exactly one row.  The plan shows that the Key Lookup is expected to be executed 45 times.  The estimate for the Inner Join output is also correct – 45 rows from the seek joining to one row each time, gives 45 rows as output. The Filter estimate is also very good: the optimizer estimates 16.9951 rows will match the specified range of transaction dates.  Eleven rows are produced by this query, but that small difference is quite normal and certainly nothing to worry about here.  All good so far. SQL Server 2008 onward The same query executed against an identical copy of AdventureWorks on SQL Server 2008 produces a different execution plan: The optimizer has pushed the Filter conditions seen in the 2005 plan down to the Key Lookup.  This is a good optimization – it makes sense to filter rows out as early as possible.  Unfortunately, it has made a bit of a mess of the cardinality estimates. The post-Filter estimate of 16.9951 rows seen in the 2005 plan has moved with the predicate on Transaction Date.  Instead of estimating one row, the plan now suggests that 16.9951 rows will be produced by each clustered index lookup – clearly not right!  This misinformation also confuses SQL Sentry Plan Explorer: Plan Explorer shows 765 rows expected from the Key Lookup (it multiplies a rounded estimate of 17 rows by 45 expected executions to give 765 rows total). Workarounds One workaround is to provide a covering non-clustered index (avoiding the lookup avoids the problem of course): CREATE INDEX nc1 ON Production.TransactionHistory (ProductID) INCLUDE (TransactionDate); With the Transaction Date filter applied as a residual predicate in the same operator as the seek, the estimate is again as expected: We could also force the use of the ultimate covering index (the clustered one): SELECT th.ProductID, th.TransactionID, th.TransactionDate FROM Production.TransactionHistory AS th WITH (INDEX(1)) WHERE th.ProductID = 1 AND th.TransactionDate BETWEEN '20030901' AND '20031231'; Summary Providing a covering non-clustered index for all possible queries is not always practical, and scanning the clustered index will rarely be optimal.  Nevertheless, these are the best workarounds we have today. In the meantime, watch out for poor cardinality estimates when a predicate is applied as part of a lookup. The worst thing is that the estimate after the lookup join in the 2008+ plans is wrong.  It’s not hopelessly wrong in this particular case (45 versus 16.9951 is not the end of the world) but it easily can be much worse, and there’s not much you can do about it.  Any decisions made by the optimizer after such a lookup could be based on very wrong information – which can only be bad news. If you think this situation should be improved, please vote for this Connect item. © 2012 Paul White – All Rights Reserved twitter: @SQL_Kiwi email: [email protected]

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• Some New .NET Downloads and Resources

  - by Kevin Grossnicklaus

  Last week I was fortunate enough to spend time in Redmond on Microsoft’s campus for the 2011 Microsoft MVP Summit.  It was great to hang out with a number of old friends and get the opportunity to talk tech with the various product teams up at Microsoft.  The weather wasn’t exactly sunny but Microsoft always does a great job with the Summit and everyone had a blast (heck, I even got to run the bases at SafeCo field) While much of what we saw is covered under NDA, there a ton of great things in the pipeline from Microsoft and many things that are already available (or just became so) that I wasn’t necessarily aware of.  The purpose of this post is to share some of the info I learned on resources and tools available to .NET developers today.  Please let me know if you have any questions (or if you know of something else cool which might benefit others). Enjoy! Visual Studio 2010 SP1 Microsoft has issued the RTM release of Visual Studio 2010 SP1.  You can download the full SP1 on MSDN as of today (March 10th to the general public) and take advantage of such things as: Silverlight 4 is included in the box (as opposed to a separate install) Silverlight 4 Profiling WCF RIA Services SP1 Intellitrace for 64-bit and SharePoint ASP.NET now easily supports IIS Express and SQL CE Want a description of all that’s new beyond the above biased list (which arguably only contains items I think are important)?  Check out this KB article. Portable Library Tools CTP Without much fanfare Microsoft has released a CTP of a new add-in to Visual Studio 2010 which simplifies code sharing between projects targeting different runtimes (i.e. Silverlight, WPF, Win7 Phone, XBox).   With this Add-In installed you can add a new project of type “Portable Library” and specify which platforms you wish to target.  Once that is done, any code added to this library will be limited to use only features which are common to all selected frameworks.  Other projects can now reference this portable library and be provided assemblies custom built to their environment.  This greatly simplifies the current process of sharing linked files between platforms like WPF and Silverlight.  You can find out more about this CTP and how it works on this great blog post. Visual Studio Async CTP Microsoft has also released a CTP of a set of language and framework enhancements to provide a much more powerful asynchronous programming model.   Due to the focus on async programming in all types of platforms (and it being the ONLY option in Silverlight and Win7 phone) a move towards a simpler and more understandable model is always a good thing. This CTP (called Visual Studio Async CTP) can be downloaded here.  You can read more about this CTP on this blog post. MSDN Code Samples Gallery Microsoft has also launched new code samples gallery on their MSDN site: http://code.msdn.microsoft.com/.   This site allows you to easily search for small samples of code related to a particular technology or platform.  If a sample of code you are looking for is not found, you can request one via the site and other developers can see your request and provide a sample to the site to suit your needs.  You can also peruse requested samples and, if you find a scenario where you can provide value, upload your own sample for the benefit of others.  Samples are packaged into the VS .vsix format and include any necessary references/dependencies.  By using .vsix as the deployment mechanism, as samples are installed from the site they are kept in your Visual Studio 2010 Samples Gallery and kept for your future reference. If you get a chance, check out the site and see how it is done.  Although a somewhat simple concept, I was very impressed with their implementation and the way they went about trying to suit a need.  I’ll definitely be looking there in the future as need something or want to share something. MSDN Search Capabilities Another item I learned recently and was not aware of (that might seem trivial to some) is the power of the MSDN site’s search capabilities.  Between the Code Samples Gallery described above and the search enhancements on MSDN, Microsoft is definitely investing in their platform to help provide developers of all skill levels the tools and resources they need to be successful. What do I mean by the MSDN search capability and why should you care? If you go to the MSDN home page (http://msdn.microsoft.com) and use the “Search MSDN with Big” box at the very top of the page you will see some very interesting results.  First, the search actually doesn’t just search the MSDN library it searches: MSDN Library All Microsoft Blogs CodePlex StackOverflow Downloads MSDN Magazine Support Knowledgebase (I’m not sure it even ends there but the above are all I know of) Beyond just searching all the above locations, the results are formatted very nicely to give some contextual information based on where the result came from.  For example, if a keyword search returned results from CodePlex, each row in the search results screen would include a large amount of information specific to CodePlex such as: Looking at the above results immediately tells you everything from the page views to the CodePlex ratings.  All in all, knowing that this much information is indexed and available from a single search location will lead me to utilize this as one of my initial searches for development information.

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• Silverlight Cream Monday WP7 App Review # 2

  - by Dave Campbell

  Today's Review (alphabetic order): GooNews, Grocery Shopping List, Need for Speed, SurfCube, and United Nations News. I'm a day late if these are going to be 'Monday' posts, but there are lots of apps, lots of goodness, and lots of email, so I might try to do 2 a week, we'll see. So once again I've got a small review of 5 apps that are either on my phone or have been. Disclaimers at the end. In this Issue:   GooNews is a very cool app from Shawn Wildermuth (AgiliTrain). I don't know if he uses this as a demo during his instruction, but it definitely serves a purpose... wanna pick up the top news items from Google on a never-ending basis? ... this is it. You can add your own keyword searches, and send stories to InstaPaper or share via email. I like this because it brings me the news quickly and updated, and works great. GooNews is by AgiliTrain and is Free This was a request by the author, and actually surprised me. I'm a big one for lists, but I would have just done a OneNote list to SkyDrive and to my phone. This app is a lot more than that, but will take you some setup to make it be 'yours'. For obvious reasons, there are no unit prices on things, so you have to set that up to get some idea of the cost of what you're shopping for. But if you do that, you'll get a nice total. Lots of thought went into the various categories and you can add your own. There's a bit of animation on the category selection that's nice. He seems to have covered all the bases necessary to use this, even shopping 'plans' that can be saved, and emailing of lists. As I said, I'm more of a raw list person, but if you take the time to set this up, it should work very nicely for you. Grocery Shopping List is by Grocery Shopper and is $0.99 ($1.99 after Feb 1) with a free trial. This was my 2nd commercial game I bought, and the one I've played the most. I ran the trial, thought it worked great, and bought it. I've had a lot of fun with this... there's no gas pedal.. your foot is in the carbeurator from the GO!, and unless you wanna tap the screen and brake like a little girl, just hang onto the steering wheel (the phone), and guide your way through. Hours of fun and challenges here. I like this because it's got some challenge to it, and the cars seem to be very realistic in their reactions. Need for Speed Undercover is by Electronic Arts is $4.99 and has a free trial. SurfCube Browser is another app by the folks that did the GuitarTuner I reviewed on Monday. You have to see SurfCube to believe it. You've probably seen the YouTube video, if not check SilverlightCream number 1017. The app works very solid, and just as the video demonstrates. I downloaded and tried this, and it immediately did 2 things: bought it, and pinned it to my start page. I like this because it's fun to work with, and it works great as a browser. I'm about *this* close to replacing the IE tile on my front page with SurfCube. SurfCube Browser is by Kinabalu Innovation Limited and is $1.99 and has a free trial. Coming in with another News app is United Nations News by Justin Angel. This is definitely a news aggregator for 'grown ups'... news, photos, videos, and radio broadcsts from the international community all in one very slick app. This is an amazingly well thought-out and complete app. Even better yet, Justin has the code on CodePlex. A very well-done International news aggregator. United Nations News is by Justin Angel and is Free. A few disclaimers: Feel free to write me about your app and tell me about it. While it would be very cool to receive a whole bunch of xap files to review, at this point, for technical reasons, I'm unable to side-load my device. Since I plan on only doing this one day a week (twice if I find time), and only 5, I may never get caught up, so if you send me some info, be patient. Re: games ... remember I'm old... I'm from the era of Colossal Cave and Zork. Duke-Nukem 2D and Captain Comic were awesome. I don't own an XBOX or any other game system, so take game reviews from my perspective -- who knows, it may be refreshing :) I won't pay for an app or game just to try it. If you expect me to test-drive your app, it's going to have to have a Free Trial. I'm still playing with the format, comments are welcome. I decided I should alphabetize the list today... so there's no order implied Let me know what you think of the idea of doing reviews, or the layout/whatever, and Stay in the 'Light! Twitter SilverlightNews | Twitter WynApse | WynApse.com | Tagged Posts | SilverlightCream Join me @ SilverlightCream | Phoenix Silverlight User Group Technorati Tags: Silverlight    Silverlight 3    Silverlight 4    Windows Phone MIX10

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• When is my View too smart?

  - by Kyle Burns

  In this posting, I will discuss the motivation behind keeping View code as thin as possible when using patterns such as MVC, MVVM, and MVP.  Once the motivation is identified, I will examine some ways to determine whether a View contains logic that belongs in another part of the application.  While the concepts that I will discuss are applicable to most any pattern which favors a thin View, any concrete examples that I present will center on ASP.NET MVC. Design patterns that include a Model, a View, and other components such as a Controller, ViewModel, or Presenter are not new to application development.  These patterns have, in fact, been around since the early days of building applications with graphical interfaces.  The reason that these patterns emerged is simple – the code running closest to the user tends to be littered with logic and library calls that center around implementation details of showing and manipulating user interface widgets and when this type of code is interspersed with application domain logic it becomes difficult to understand and much more difficult to adequately test.  By removing domain logic from the View, we ensure that the View has a single responsibility of drawing the screen which, in turn, makes our application easier to understand and maintain. I was recently asked to take a look at an ASP.NET MVC View because the developer reviewing it thought that it possibly had too much going on in the view.  I looked at the .CSHTML file and the first thing that occurred to me was that it began with 40 lines of code declaring member variables and performing the necessary calculations to populate these variables, which were later either output directly to the page or used to control some conditional rendering action (such as adding a class name to an HTML element or not rendering another element at all).  This exhibited both of what I consider the primary heuristics (or code smells) indicating that the View is too smart: Member variables – in general, variables in View code are an indication that the Model to which the View is being bound is not sufficient for the needs of the View and that the View has had to augment that Model.  Notable exceptions to this guideline include variables used to hold information specifically related to rendering (such as a dynamically determined CSS class name or the depth within a recursive structure for indentation purposes) and variables which are used to facilitate looping through collections while binding. Arithmetic – as with member variables, the presence of arithmetic operators within View code are an indication that the Model servicing the View is insufficient for its needs.  For example, if the Model represents a line item in a sales order, it might seem perfectly natural to “normalize” the Model by storing the quantity and unit price in the Model and multiply these within the View to show the line total.  While this does seem natural, it introduces a business rule to the View code and makes it impossible to test that the rounding of the result meets the requirement of the business without executing the View.  Within View code, arithmetic should only be used for activities such as incrementing loop counters and calculating element widths. In addition to the two characteristics of a “Smart View” that I’ve discussed already, this View also exhibited another heuristic that commonly indicates to me the need to refactor a View and make it a bit less smart.  That characteristic is the existence of Boolean logic that either does not work directly with properties of the Model or works with too many properties of the Model.  Consider the following code and consider how logic that does not work directly with properties of the Model is just another form of the “member variable” heuristic covered earlier: @if(DateTime.Now.Hour < 12) {     <div>Good Morning!</div> } else {     <div>Greetings</div> } This code performs business logic to determine whether it is morning.  A possible refactoring would be to add an IsMorning property to the Model, but in this particular case there is enough similarity between the branches that the entire branching structure could be collapsed by adding a Greeting property to the Model and using it similarly to the following: <div>@Model.Greeting</div> Now let’s look at some complex logic around multiple Model properties: @if (ModelPageNumber + Model.NumbersToDisplay == Model.PageCount         || (Model.PageCount != Model.CurrentPage             && !Model.DisplayValues.Contains(Model.PageCount))) {     <div>There's more to see!</div> } In this scenario, not only is the View code difficult to read (you shouldn’t have to play “human compiler” to determine the purpose of the code), but it also complex enough to be at risk for logical errors that cannot be detected without executing the View.  Conditional logic that requires more than a single logical operator should be looked at more closely to determine whether the condition should be evaluated elsewhere and exposed as a single property of the Model.  Moving the logic above outside of the View and exposing a new Model property would simplify the View code to: @if(Model.HasMoreToSee) {     <div>There’s more to see!</div> } In this posting I have briefly discussed some of the more prominent heuristics that indicate a need to push code from the View into other pieces of the application.  You should now be able to recognize these symptoms when building or maintaining Views (or the Models that support them) in your applications.

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• NetBeans, JSF, and MySQL Primary Keys using AUTO_INCREMENT

  - by MarkH

  I recently had the opportunity to spin up a small web application using JSF and MySQL. Having developed JSF apps with Oracle Database back-ends before and possessing some small familiarity with MySQL (sans JSF), I thought this would be a cakewalk. Things did go pretty smoothly...but there was one little "gotcha" that took more time than the few seconds it really warranted. The Problem Every DBMS has its own way of automatically generating primary keys, and each has its pros and cons. For the Oracle Database, you use a sequence and point your Java classes to it using annotations that look something like this: @GeneratedValue(strategy=GenerationType.SEQUENCE, generator="POC_ID_SEQ") @SequenceGenerator(name="POC_ID_SEQ", sequenceName="POC_ID_SEQ", allocationSize=1) Between creating the actual sequence in the database and making sure you have your annotations right (watch those typos!), it seems a bit cumbersome. But it typically "just works", without fuss. Enter MySQL. Designating an integer-based field as PRIMARY KEY and using the keyword AUTO_INCREMENT makes the same task seem much simpler. And it is, mostly. But while NetBeans cranks out a superb "first cut" for a basic JSF CRUD app, there are a couple of small things you'll need to bring to the mix in order to be able to actually (C)reate records. The (RUD) performs fine out of the gate. The Solution Omitting all design considerations and activity (!), here is the basic sequence of events I followed to create, then resolve, the JSF/MySQL "Primary Key Perfect Storm": Fire up NetBeans. Create JSF project. Create Entity Classes from Database. Create JSF Pages from Entity Classes. Test run. Try to create record and hit error. It's a simple fix, but one that was fun to find in its completeness. :-) Even though you've told it what to do for a primary key, a MySQL table requires a gentle nudge to actually generate that new key value. Two things are needed to make the magic happen. First, you need to ensure the following annotation is in place in your Java entity classes: @GeneratedValue(strategy = GenerationType.IDENTITY) All well and good, but the real key is this: in your controller class(es), you'll have a create() function that looks something like this, minus the comment line and the setId() call in bold red type:     public String create() {         try {             // Assign 0 to ID for MySQL to properly auto_increment the primary key.             current.setId(0);             getFacade().create(current);             JsfUtil.addSuccessMessage(ResourceBundle.getBundle("/Bundle").getString("CategoryCreated"));             return prepareCreate();         } catch (Exception e) {             JsfUtil.addErrorMessage(e, ResourceBundle.getBundle("/Bundle").getString("PersistenceErrorOccured"));             return null;         }     } Setting the current object's primary key attribute to zero (0) prior to saving it tells MySQL to get the next available value and assign it to that record's key field. Short and simple…but not inherently obvious if you've never used that particular combination of NetBeans/JSF/MySQL before. Hope this helps! All the best, Mark

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• MVVM - how to make creating viewmodels at runtime less painfull

  - by Mr Happy

  I apologize for the long question, it reads a bit as a rant, but I promise it's not! I've summarized my question(s) below In the MVC world, things are straightforward. The Model has state, the View shows the Model, and the Controller does stuff to/with the Model (basically), a controller has no state. To do stuff the Controller has some dependencies on web services, repository, the lot. When you instantiate a controller you care about supplying those dependencies, nothing else. When you execute an action (method on Controller), you use those dependencies to retrieve or update the Model or calling some other domain service. If there's any context, say like some user wants to see the details of a particular item, you pass the Id of that item as parameter to the Action. Nowhere in the Controller is there any reference to any state. So far so good. Enter MVVM. I love WPF, I love data binding. I love frameworks that make data binding to ViewModels even easier (using Caliburn Micro a.t.m.). I feel things are less straightforward in this world though. Let's do the exercise again: the Model has state, the View shows the ViewModel, and the ViewModel does stuff to/with the Model (basically), a ViewModel does have state! (to clarify; maybe it delegates all the properties to one or more Models, but that means it must have a reference to the model one way or another, which is state in itself) To do stuff the ViewModel has some dependencies on web services, repository, the lot. When you instantiate a ViewModel you care about supplying those dependencies, but also the state. And this, ladies and gentlemen, annoys me to no end. Whenever you need to instantiate a ProductDetailsViewModel from the ProductSearchViewModel (from which you called the ProductSearchWebService which in turn returned IEnumerable<ProductDTO>, everybody still with me?), you can do one of these things: call new ProductDetailsViewModel(productDTO, _shoppingCartWebService /* dependcy */);, this is bad, imagine 3 more dependencies, this means the ProductSearchViewModel needs to take on those dependencies as well. Also changing the constructor is painfull. call _myInjectedProductDetailsViewModelFactory.Create().Initialize(productDTO);, the factory is just a Func, they are easily generated by most IoC frameworks. I think this is bad because Init methods are a leaky abstraction. You also can't use the readonly keyword for fields that are set in the Init method. I'm sure there are a few more reasons. call _myInjectedProductDetailsViewModelAbstractFactory.Create(productDTO); So... this is the pattern (abstract factory) that is usually recommended for this type of problem. I though it was genious since it satisfies my craving for static typing, until I actually started using it. The amount of boilerplate code is I think too much (you know, apart from the ridiculous variable names I get use). For each ViewModel that needs runtime parameters you'll get two extra files (factory interface and implementation), and you need to type the non-runtime dependencies like 4 extra times. And each time the dependencies change, you get to change it in the factory as well. It feels like I don't even use an DI container anymore. (I think Castle Windsor has some kind of solution for this [with it's own drawbacks, correct me if I'm wrong]). do something with anonymous types or dictionary. I like my static typing. So, yeah. Mixing state and behavior in this way creates a problem which don't exist at all in MVC. And I feel like there currently isn't a really adequate solution for this problem. Now I'd like to observe some things: People actually use MVVM. So they either don't care about all of the above, or they have some brilliant other solution. I haven't found an indepth example of MVVM with WPF. For example, the NDDD-sample project immensely helped me understand some DDD concepts. I'd really like it if someone could point me in the direction of something similar for MVVM/WPF. Maybe I'm doing MVVM all wrong and I should turn my design upside down. Maybe I shouldn't have this problem at all. Well I know other people have asked the same question so I think I'm not the only one. To summarize Am I correct to conclude that having the ViewModel being an integration point for both state and behavior is the reason for some difficulties with the MVVM pattern as a whole? Is using the abstract factory pattern the only/best way to instantiate a ViewModel in a statically typed way? Is there something like an in depth reference implementation available? Is having a lot of ViewModels with both state/behavior a design smell?

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• Training a 'replacement', how to enforce standards?

  - by Mohgeroth

  Not sure that this is the right stack exchange site to ask this of, but here goes... Scope I work for a small company that employs a few hundred people. The development team for the company is small and works out of visual foxpro. A specific department in the company hired me in as a 'lone gunman' to fix and enhance a pre-existing invoicing system. I've successfully taken an Access application that suffered from a lot of risks and limitations and converted it into a C# application driven off of a SQL server backend. I have recently obtained my undergraduate and am no expert by any means. To help make up for that I've felt that earning microsoft certifications will force me to understand more about .net and how it functions. So, after giving my notice with 9 months in advance, 3 months ago a replacement finally showed up. Their role is to learn what I have been designing to an attempt to support the applications designed in C#. The Replacement Fresh out of college with no real-world work experience, the first instinct for anything involving data was and still is listboxes... any time data is mentioned the list box is the control of choice for the replacement. This has gotten to the point, no matter how many times I discuss other controls, where I've seen 5 listboxes on a single form. Classroom experience was almost all C++ console development. So, an example of where I have concern is in a winforms application: Users need to key Reasons into a table to select from later. Given that I know that a strongly typed data set exists, I can just drag the data source from the toolbox and it would create all of this for me. I realize this is a simple example but using databinding is the key. For the past few months now we have been talking about the strongly typed dataset, how to use it and where it interacts with other controls. Data sets, how they work in relation to binding sources, adapters and data grid views. After handing this project off I expected questions about how to implement these since for me this is the way to do it. What happened next simply floors me: An instance of an adapter from the strongly typed dataset was created in the activate event of the form, a table was created and filled with data. Then, a loop was made to manually add rows to a listbox from this table. Finally, a variable was kept to do lookups to figure out what ID the record was for updates if required. How do they modify records you ask? That was my first question too. You won't believe how simple it is, all you do it double click and they type into a pop-up prompt the new value to change it to. As a data entry operator, all the modal popups would drive me absolutely insane. The final solution exceeds 100 lines of code that must be maintained. So my concern is that none of this is sinking in... the department is only allowed 20 hours a week of their time. Up until last week, we've only been given 4-5 hours a week if I'm lucky. The past week or so, I've been lucky to get 10. Question WHAT DO I DO?! I have 4 weeks left until I leave and they fully 'support' this application. I love this job and the opportunity it has given me but it's time for me to spread my wings and find something new. I am in no way, shape or form convinced that they are ready to take over. I do feel that the replacement has the technical ability to 'figure it out' but instead of learning they just write code to do all of this stuff manually. If the replacement wants to code differently in the end, as long as it works I'm fine with that as horrifiying at it looks. However to support what I have designed they MUST to understand how it works and how I have used controls and the framework to make 'magic' happen. This project has about 40 forms, a database with over 30 some odd tables, triggers and stored procedures. It relates labor to invoices to contracts to projections... it's not as simple as it was three years ago when I began this project and the department is now in a position where they cannot survive without it. How in the world can I accomplish any of the following?: Enforce standards or understanding in constent design when the department manager keeps telling them they can do it however they want to Find a way to engage the replacement in active learning of the framework and system design that support must be given for Gracefully inform sr. management that 5-9 hours a week is simply not enough time to learn about the department, pre-existing processes, applications that need to be supported AND determine where potential enhancements to the system go... Yes I know this is a wall of text, thanks for reading through me but I simply don't know what I should be doing. For me, this job is a monster of a reference and things would look extremely bad if I left and things fell apart. How do I handle this?

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• Data management in unexpected places

  - by Ashok_Ora

  Normal 0 false false false EN-US X-NONE X-NONE Data management in unexpected places When you think of network switches, routers, firewall appliances, etc., it may not be obvious that at the heart of these kinds of solutions is an engine that can manage huge amounts of data at very high throughput with low latencies and high availability. Consider a network router that is processing tens (or hundreds) of thousands of network packets per second. So what really happens inside a router? Packets are streaming in at the rate of tens of thousands per second. Each packet has multiple attributes, for example, a destination, associated SLAs etc. For each packet, the router has to determine the address of the next “hop” to the destination; it has to determine how to prioritize this packet. If it’s a high priority packet, then it has to be sent on its way before lower priority packets. As a consequence of prioritizing high priority packets, lower priority data packets may need to be temporarily stored (held back), but addressed fairly. If there are security or privacy requirements associated with the data packet, those have to be enforced. You probably need to keep track of statistics related to the packets processed (someone’s sure to ask). You have to do all this (and more) while preserving high availability i.e. if one of the processors in the router goes down, you have to have a way to continue processing without interruption (the customer won’t be happy with a “choppy” VoIP conversation, right?). And all this has to be achieved without ANY intervention from a human operator – the router is most likely to be in a remote location – it must JUST CONTINUE TO WORK CORRECTLY, even when bad things happen. How is this implemented? As soon as a packet arrives, it is interpreted by the receiving software. The software decodes the packet headers in order to determine the destination, kind of packet (e.g. voice vs. data), SLAs associated with the “owner” of the packet etc. It looks up the internal database of “rules” of how to process this packet and handles the packet accordingly. The software might choose to hold on to the packet safely for some period of time, if it’s a low priority packet. Ah – this sounds very much like a database problem. For each packet, you have to minimally · Look up the most efficient next “hop” towards the destination. The “most efficient” next hop can change, depending on latency, availability etc. · Look up the SLA and determine the priority of this packet (e.g. voice calls get priority over data ftp) · Look up security information associated with this data packet. It may be necessary to retrieve the context for this network packet since a network packet is a small “slice” of a session. The context for the “header” packet needs to be stored in the router, in order to make this work. · If the priority of the packet is low, then “store” the packet temporarily in the router until it is time to forward the packet to the next hop. · Update various statistics about the packet. In most cases, you have to do all this in the context of a single transaction. For example, you want to look up the forwarding address and perform the “send” in a single transaction so that the forwarding address doesn’t change while you’re sending the packet. So, how do you do all this? Berkeley DB is a proven, reliable, high performance, highly available embeddable database, designed for exactly these kinds of usage scenarios. Berkeley DB is a robust, reliable, proven solution that is currently being used in these scenarios. First and foremost, Berkeley DB (or BDB for short) is very very fast. It can process tens or hundreds of thousands of transactions per second. It can be used as a pure in-memory database, or as a disk-persistent database. BDB provides high availability – if one board in the router fails, the system can automatically failover to another board – no manual intervention required. BDB is self-administering – there’s no need for manual intervention in order to maintain a BDB application. No need to send a technician to a remote site in the middle of nowhere on a freezing winter day to perform maintenance operations. BDB is used in over 200 million deployments worldwide for the past two decades for mission-critical applications such as the one described here. You have a choice of spending valuable resources to implement similar functionality, or, you could simply embed BDB in your application and off you go! I know what I’d do – choose BDB, so I can focus on my business problem. What will you do? /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-qformat:yes; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin-top:0in; mso-para-margin-right:0in; mso-para-margin-bottom:10.0pt; mso-para-margin-left:0in; line-height:115%; mso-pagination:widow-orphan; font-size:11.0pt; font-family:"Calibri","sans-serif"; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin;}

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• Most Innovative IDM Projects: Awards at OpenWorld

  - by Tanu Sood

  On Tuesday at Oracle OpenWorld 2012, Oracle recognized the winners of Innovation Awards 2012 at a ceremony presided over by Hasan Rizvi, Executive Vice President at Oracle. Oracle Fusion Middleware Innovation Awards recognize customers for achieving significant business value through innovative uses of Oracle Fusion Middleware offerings. Winners are selected based on the uniqueness of their business case, business benefits, level of impact relative to the size of the organization, complexity and magnitude of implementation, and the originality of architecture. This year’s Award honors customers for their cutting-edge solutions driving business innovation and IT modernization using Oracle Fusion Middleware. The program has grown over the past 6 years, receiving a record number of nominations from customers around the globe. The winners were selected by a panel of judges that ranked each nomination across multiple different scoring categories. Congratulations to both Avea and ETS for winning this year’s Innovation Award for Identity Management. Identity Management Innovation Award 2012 Winner – Avea Company: Founded in 2004, AveA is the sole GSM 1800 mobile operator of Turkey and has reached a nationwide customer base of 12.8 million as of the end of 2011 Region: Turkey (EMEA) Products: Oracle Identity Manager, Oracle Identity Analytics, Oracle Access Management Suite Business Drivers: ·         To manage the agility and scale required for GSM Operations and enable call center efficiency by enabling agents to change their identity profiles (accounts and entitlements) rapidly based on call load. ·         Enhance user productivity and call center efficiency with self service password resets ·         Enforce compliance and audit reporting ·         Seamless identity management between AveA and parent company Turk Telecom Innovation and Results: ·         One of the first Sun2Oracle identity management migrations designed for high performance provisioning and trusted reconciliation built with connectors developed on the ICF architecture that provides custom user interfaces for  dynamic and rapid management of roles and entitlements along with entitlement level attestation using closed loop remediation between Oracle Identity Manager and Oracle Identity Analytics. ·         Dramatic reduction in identity administration and call center password reset tasks leading to 20% reduction in administration costs and 95% reduction in password related calls. ·         Enhanced user productivity by up to 25% to date ·         Enforced enterprise security and reduced risk ·         Cost-effective compliance management ·         Looking to seamlessly integrate with parent and sister companies’ infrastructure securely. Identity Management Innovation Award 2012 Winner – Education Testing Service (ETS)       See last year's winners here --Company: ETS is a private nonprofit organization devoted to educational measurement and research, primarily through testing. Region: U.S.A (North America) Products: Oracle Access Manager, Oracle Identity Federation, Oracle Identity Manager Business Drivers: ETS develops and administers more than 50 million achievement and admissions tests each year in more than 180 countries, at more than 9,000 locations worldwide.  As the business becomes more globally based, having a robust solution to security and user management issues becomes paramount. The organizations was looking for: ·         Simplified user experience for over 3000 company users and more than 6 million dynamic student and staff population ·         Infrastructure and administration cost reduction ·         Managing security risk by controlling 3rd party access to ETS systems ·         Enforce compliance and manage audit reporting ·         Automate on-boarding and decommissioning of user account to improve security, reduce administration costs and enhance user productivity ·         Improve user experience with simplified sign-on and user self service Innovation and Results: 1.    Manage Risk ·         Centralized system to control user access ·         Provided secure way of accessing service providers' application using federated SSO. ·         Provides reporting capability for auditing, governance and compliance. 2.    Improve efficiency ·         Real-Time provisioning to target systems ·         Centralized provisioning system for user management and access controls. ·         Enabling user self services. 3.    Reduce cost ·         Re-using common shared services for provisioning, SSO, Access by application reducing development cost and time. ·         Reducing infrastructure and maintenance cost by decommissioning legacy/redundant IDM services. ·         Reducing time and effort to implement security functionality in business applications (“onboard” instead of new development). ETS was able to fold in new and evolving requirement in addition to the initial stated goals realizing quick ROI and successfully meeting business objectives. Congratulations to the winners once again. We will be sure to bring you more from these Innovation Award winners over the next few months.

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• How to make creating viewmodels at runtime less painfull

  - by Mr Happy

  I apologize for the long question, it reads a bit as a rant, but I promise it's not! I've summarized my question(s) below In the MVC world, things are straightforward. The Model has state, the View shows the Model, and the Controller does stuff to/with the Model (basically), a controller has no state. To do stuff the Controller has some dependencies on web services, repository, the lot. When you instantiate a controller you care about supplying those dependencies, nothing else. When you execute an action (method on Controller), you use those dependencies to retrieve or update the Model or calling some other domain service. If there's any context, say like some user wants to see the details of a particular item, you pass the Id of that item as parameter to the Action. Nowhere in the Controller is there any reference to any state. So far so good. Enter MVVM. I love WPF, I love data binding. I love frameworks that make data binding to ViewModels even easier (using Caliburn Micro a.t.m.). I feel things are less straightforward in this world though. Let's do the exercise again: the Model has state, the View shows the ViewModel, and the ViewModel does stuff to/with the Model (basically), a ViewModel does have state! (to clarify; maybe it delegates all the properties to one or more Models, but that means it must have a reference to the model one way or another, which is state in itself) To do stuff the ViewModel has some dependencies on web services, repository, the lot. When you instantiate a ViewModel you care about supplying those dependencies, but also the state. And this, ladies and gentlemen, annoys me to no end. Whenever you need to instantiate a ProductDetailsViewModel from the ProductSearchViewModel (from which you called the ProductSearchWebService which in turn returned IEnumerable<ProductDTO>, everybody still with me?), you can do one of these things: call new ProductDetailsViewModel(productDTO, _shoppingCartWebService /* dependcy */);, this is bad, imagine 3 more dependencies, this means the ProductSearchViewModel needs to take on those dependencies as well. Also changing the constructor is painfull. call _myInjectedProductDetailsViewModelFactory.Create().Initialize(productDTO);, the factory is just a Func, they are easily generated by most IoC frameworks. I think this is bad because Init methods are a leaky abstraction. You also can't use the readonly keyword for fields that are set in the Init method. I'm sure there are a few more reasons. call _myInjectedProductDetailsViewModelAbstractFactory.Create(productDTO); So... this is the pattern (abstract factory) that is usually recommended for this type of problem. I though it was genious since it satisfies my craving for static typing, until I actually started using it. The amount of boilerplate code is I think too much (you know, apart from the ridiculous variable names I get use). For each ViewModel that needs runtime parameters you'll get two extra files (factory interface and implementation), and you need to type the non-runtime dependencies like 4 extra times. And each time the dependencies change, you get to change it in the factory as well. It feels like I don't even use an DI container anymore. (I think Castle Windsor has some kind of solution for this [with it's own drawbacks, correct me if I'm wrong]). do something with anonymous types or dictionary. I like my static typing. So, yeah. Mixing state and behavior in this way creates a problem which don't exist at all in MVC. And I feel like there currently isn't a really adequate solution for this problem. Now I'd like to observe some things: People actually use MVVM. So they either don't care about all of the above, or they have some brilliant other solution. I haven't found an indepth example of MVVM with WPF. For example, the NDDD-sample project immensely helped me understand some DDD concepts. I'd really like it if someone could point me in the direction of something similar for MVVM/WPF. Maybe I'm doing MVVM all wrong and I should turn my design upside down. Maybe I shouldn't have this problem at all. Well I know other people have asked the same question so I think I'm not the only one. To summarize Am I correct to conclude that having the ViewModel being an integration point for both state and behavior is the reason for some difficulties with the MVVM pattern as a whole? Is using the abstract factory pattern the only/best way to instantiate a ViewModel in a statically typed way? Is there something like an in depth reference implementation available? Is having a lot of ViewModels with both state/behavior a design smell?

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• How can I implement a database TableView like thing in C++?

  - by Industrial-antidepressant

  How can I implement a TableView like thing in C++? I want to emulating a tiny relation database like thing in C++. I have data tables, and I want to transform it somehow, so I need a TableView like class. I want filtering, sorting, freely add and remove items and transforming (ex. view as UPPERCASE and so on). The whole thing is inside a GUI application, so datatables and views are attached to a GUI (or HTML or something). So how can I identify an item in the view? How can I signal it when the table is changed? Is there some design pattern for this? Here is a simple table, and a simple data item: #include <string> #include <boost/multi_index_container.hpp> #include <boost/multi_index/member.hpp> #include <boost/multi_index/ordered_index.hpp> #include <boost/multi_index/random_access_index.hpp> using boost::multi_index_container; using namespace boost::multi_index; struct Data { Data() {} int id; std::string name; }; struct row{}; struct id{}; struct name{}; typedef boost::multi_index_container< Data, indexed_by< random_access<tag<row> >, ordered_unique<tag<id>, member<Data, int, &Data::id> >, ordered_unique<tag<name>, member<Data, std::string, &Data::name> > > > TDataTable; class DataTable { public: typedef Data item_type; typedef TDataTable::value_type value_type; typedef TDataTable::const_reference const_reference; typedef TDataTable::index<row>::type TRowIndex; typedef TDataTable::index<id>::type TIdIndex; typedef TDataTable::index<name>::type TNameIndex; typedef TRowIndex::iterator iterator; DataTable() : row_index(rule_table.get<row>()), id_index(rule_table.get<id>()), name_index(rule_table.get<name>()), row_index_writeable(rule_table.get<row>()) { } TDataTable::const_reference operator[](TDataTable::size_type n) const { return rule_table[n]; } std::pair<iterator,bool> push_back(const value_type& x) { return row_index_writeable.push_back(x); } iterator erase(iterator position) { return row_index_writeable.erase(position); } bool replace(iterator position,const value_type& x) { return row_index_writeable.replace(position, x); } template<typename InputIterator> void rearrange(InputIterator first) { return row_index_writeable.rearrange(first); } void print_table() const; unsigned size() const { return row_index.size(); } TDataTable rule_table; const TRowIndex& row_index; const TIdIndex& id_index; const TNameIndex& name_index; private: TRowIndex& row_index_writeable; }; class DataTableView { DataTableView(const DataTable& source_table) {} // How can I implement this? // I want filtering, sorting, signaling upper GUI layer, and sorting, and ... }; int main() { Data data1; data1.id = 1; data1.name = "name1"; Data data2; data2.id = 2; data2.name = "name2"; DataTable table; table.push_back(data1); DataTable::iterator it1 = table.row_index.iterator_to(table[0]); table.erase(it1); table.push_back(data1); Data new_data(table[0]); new_data.name = "new_name"; table.replace(table.row_index.iterator_to(table[0]), new_data); for (unsigned i = 0; i < table.size(); ++i) std::cout << table[i].name << std::endl; #if 0 // using scenarios: DataTableView table_view(table); table_view.fill_from_source(); // synchronization with source table_view.remove(data_item1); // remove item from view table_view.add(data_item2); // add item from source table table_view.filter(filterfunc); // filtering table_view.sort(sortfunc); // sorting // modifying from source_able, hot to signal the table_view? // FYI: Table view is atteched to a GUI item table.erase(data); table.replace(data); #endif return 0; }

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• C++ strongly typed typedef

  - by Kian

  I've been trying to think of a way of declaring strongly typed typedefs, to catch a certain class of bugs in the compilation stage. It's often the case that I'll typedef an int into several types of ids, or a vector to position or velocity: typedef int EntityID; typedef int ModelID; typedef Vector3 Position; typedef Vector3 Velocity; This can make the intent of code more clear, but after a long night of coding one might make silly mistakes like comparing different kinds of ids, or adding a position to a velocity perhaps. EntityID eID; ModelID mID; if ( eID == mID ) // <- Compiler sees nothing wrong { /*bug*/ } Position p; Velocity v; Position newP = p + v; // bug, meant p + v*s but compiler sees nothing wrong Unfortunately, suggestions I've found for strongly typed typedefs include using boost, which at least for me isn't a possibility (I do have c++11 at least). So after a bit of thinking, I came upon this idea, and wanted to run it by someone. First, you declare the base type as a template. The template parameter isn't used for anything in the definition, however: template < typename T > class IDType { unsigned int m_id; public: IDType( unsigned int const& i_id ): m_id {i_id} {}; friend bool operator==<T>( IDType<T> const& i_lhs, IDType<T> const& i_rhs ); }; Friend functions actually need to be forward declared before the class definition, which requires a forward declaration of the template class. We then define all the members for the base type, just remembering that it's a template class. Finally, when we want to use it, we typedef it as: class EntityT; typedef IDType<EntityT> EntityID; class ModelT; typedef IDType<ModelT> ModelID; The types are now entirely separate. Functions that take an EntityID will throw a compiler error if you try to feed them a ModelID instead, for example. Aside from having to declare the base types as templates, with the issues that entails, it's also fairly compact. I was hoping anyone had comments or critiques about this idea? One issue that came to mind while writing this, in the case of positions and velocities for example, would be that I can't convert between types as freely as before. Where before multiplying a vector by a scalar would give another vector, so I could do: typedef float Time; typedef Vector3 Position; typedef Vector3 Velocity; Time t = 1.0f; Position p = { 0.0f }; Velocity v = { 1.0f, 0.0f, 0.0f }; Position newP = p + v*t; With my strongly typed typedef I'd have to tell the compiler that multypling a Velocity by a Time results in a Position. class TimeT; typedef Float<TimeT> Time; class PositionT; typedef Vector3<PositionT> Position; class VelocityT; typedef Vector3<VelocityT> Velocity; Time t = 1.0f; Position p = { 0.0f }; Velocity v = { 1.0f, 0.0f, 0.0f }; Position newP = p + v*t; // Compiler error To solve this, I think I'd have to specialize every conversion explicitly, which can be kind of a bother. On the other hand, this limitation can help prevent other kinds of errors (say, multiplying a Velocity by a Distance, perhaps, which wouldn't make sense in this domain). So I'm torn, and wondering if people have any opinions on my original issue, or my approach to solving it.

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• Fluent NHibernate Mapping and Formulas/DatePart

  - by Alessandro Di Lello

  Hi There, i have a very simple table with a Datetime column and i have this mapping in my domain object. MyDate is the name of the datetime column in the DB. public virtual int Day { get; set; } public virtual int Month { get; set; } public virtual int Year { get; set; } public virtual int Hour { get; set; } public virtual int Minutes { get; set; } public virtual int Seconds { get;set; } public virtual int WeekNo { get; set; } Map(x => x.Day).Formula("DATEPART(day, Datetime)"); Map(x => x.Month).Formula("DATEPART(month, Datetime)"); Map(x => x.Year).Formula("DATEPART(year, Datetime)"); Map(x => x.Hour).Formula("DATEPART(hour, Datetime)"); Map(x => x.Minutes).Formula("DATEPART(minute, Datetime)"); Map(x => x.Seconds).Formula("DATEPART(second, Datetime)"); Map(x => x.WeekNo).Formula("DATEPART(week, Datetime)"); This is working all great .... but Week Datepart. I saw with NHProf the sql generating for a select and here's the problem it's generating all the sql correctly but for week datepart.. this is part of the SQL generated: ....Datepart(day, MyDate) ... ....Datepart(month, MyDate) ... ....Datepart(year, MyDate) ... ....Datepart(hour, MyDate) ... ....Datepart(minute, MyDate) ... ....Datepart(second, MyDate) ... ....Datepart(this_.week, MyDate) ... where this_ is the alias for the table that nhibernate uses. so it's treating the week keyword for the datepart stuff as a column or something like that. To clarify there's no column or properties that is called week. some help ? cheers Alessandro

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• InteropServices COMException when executing a .net app from a web CGI script on Windows Server 2003

  - by Kurt W. Leucht

  Disclaimer: I'm completely clueless about .net and COM. I have a vendor's application that appears to be written in .net and I'm trying to wrap it with a web form (a cgi-bin Perl script) so I can eventually launch this vendor's app from a separate computer. I'm on a Windows Server 2003 R2 SE SP1 system and I'm using Apache 2.2 for the web server and ActivePerl 5.10.0.1004 for the cgi script. My cgi script calls the vendor's app that resides on the same machine using the Perl backtick operator. ... $result = "Result: " . `$vendorsPath/$vendorsExecutable $arg1 $arg2`; ... Right now I'm just running IE web browser locally on the server machine and accessing "http://localhost/cgi-bin/myPerlScript.pl". The vendor's app fails and logs a debug message that includes the following stack trace (I changed a couple names so as to not give away the vendor's identity): ... System.Reflection.TargetInvocationException: Exception has been thrown by the target of an invocation. ---> System.Runtime.InteropServices.COMException (0x80043A1D): 0x80040154 - Class not registered --- End of inner exception stack trace --- at System.RuntimeType.InvokeDispMethod(String name, BindingFlags invokeAttr, Object target, Object[] args, Boolean[] byrefModifiers, Int32 culture, String[] namedParameters) at System.RuntimeType.InvokeMember(String name, BindingFlags invokeAttr, Binder binder, Object target, Object[] args, ParameterModifier[] modifiers, CultureInfo culture, String[] namedParameters) at VendorsTool.Engine.Core.VendorsEngine.LoadVendorsServices(String fileName, String& projectCommPath) ... When I run the vendors app from the Windows command line on the server machine with the exact same arguments that the cgi script is passing it runs just fine, so there's something about invoking their app via the web script that is causing a problem. This problem is likely security related because the whole thing runs just fine on a Windows XP Pro machine (both command line and web invocation). I actually developed my web script there and got it completely working there before I tried moving it to the Windows Server 2003 machine. So what's different about the Windows Server 2003 machine that would keep the vendor's .net app from being executed successfully by a web cgi script? Can I fix this problem somehow to make it work on my server or will the vendor have to make a change to their .net app and ship out a new version? I'm probably the only person in the world who is trying to execute this vendor's app from a separate program, so I hate to bother the vendor with the issue if there's a workaround that I can implement myself here on my server machine. Plus, I'm in kind of a hurry and I don't want to wait 4 or 6 months for the vendor to put in a fix and deploy a new version. Thanks for any advise you can give.

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• Extracting pair member in lambda expressions and template typedef idiom

  - by Nazgob

  Hi, I have some complex types here so I decided to use nifty trick to have typedef on templated types. Then I have a class some_container that has a container as a member. Container is a vector of pairs composed of element and vector. I want to write std::find_if algorithm with lambda expression to find element that have certain value. To get the value I have to call first on pair and then get value from element. Below my std::find_if there is normal loop that does the trick. My lambda fails to compile. How to access value inside element which is inside pair? I use g++ 4.4+ and VS 2010 and I want to stick to boost lambda for now. #include <vector> #include <algorithm> #include <boost\lambda\lambda.hpp> #include <boost\lambda\bind.hpp> template<typename T> class element { public: T value; }; template<typename T> class element_vector_pair // idiom to have templated typedef { public: typedef std::pair<element<T>, std::vector<T> > type; }; template<typename T> class vector_containter // idiom to have templated typedef { public: typedef std::vector<typename element_vector_pair<T>::type > type; }; template<typename T> bool operator==(const typename element_vector_pair<T>::type & lhs, const typename element_vector_pair<T>::type & rhs) { return lhs.first.value == rhs.first.value; } template<typename T> class some_container { public: element<T> get_element(const T& value) const { std::find_if(container.begin(), container.end(), bind(&typename vector_containter<T>::type::value_type::first::value, boost::lambda::_1) == value); /*for(size_t i = 0; i < container.size(); ++i) { if(container.at(i).first.value == value) { return container.at(i); } }*/ return element<T>(); //whatever } protected: typename vector_containter<T>::type container; }; int main() { some_container<int> s; s.get_element(5); return 0; }

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• Delphi - TPerlRegEx / RegExBuddy Problem

  - by Brad

  I've got a problem with RegEx and Delphi 2k9 (Win32). I get the following Error: First chance exception at $7C812AFB. Exception class Exception with message 'TPerlRegEx.Compile() - Please specify a regular expression in RegEx first'. I've got the latest version of TPerlRegEx from the website. Using its defualt settings (Using DLL) I'm including demo source code. It's using the code generated by RegExBuddy, latest version. http://www.4shared.com/file/236428923/97478b61/googleresultstestdata.html http://www.4shared.com/file/236439483/e0acbe6d/Unit2.html Delphi FORM http://www.4shared.com/file/236439473/6734a2a2/Unit2.html Delphi PAS Thanks for any help -Brad Data is from Google External Keyword Tool RegEx could use some refinement... but works in RegExBuddy not in Delphi unit Unit2; interface uses Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms, Dialogs, StdCtrls, PerlRegEx; type TForm2 = class(TForm) Memo1: TMemo; Memo2: TMemo; Button1: TButton; procedure Button1Click(Sender: TObject); private { Private declarations } public { Public declarations } end; var Form2: TForm2; implementation {$R *.dfm} procedure TForm2.Button1Click(Sender: TObject); var Regex: TPerlRegEx; GroupIndex: Integer; begin Regex := TPerlRegEx.Create(nil); Regex.RegEx := 'criteria\.push\(new kpCriterion\(&#39;(?P<keyword>(.*?))&#39;, (?P<number1>(.*?)),'#13#10'''(?P<localsearch>(.*?))'', ''(?P<globalsearch>(.*?))'', (?P<localsearchnum>(.*?)), (?P<globalsearchnum>(.*?)), (.*+)'#13#10','#13#10'&#39;\$(?P<price>(.*?))&#39;, (?P<number2>(.*?)),'#13#10'&#39;(?P<range>(.*?))&#39;, (?P<number3>(.*+))'; Regex.Options := [preMultiLine]; Regex.Subject := memo1.text; if Regex.Match then begin memo2.Lines.Add('Matches Found'); repeat for GroupIndex := 0 to Regex.SubExpressionCount do begin memo2.lines.add( Regex.SubExpressions[GroupIndex]); //Add Results to memo // backreference text: Regex.SubExpressions[GroupIndex]; // backreference start: Regex.SubExpressionOffsets[GroupIndex]; // backreference length: Regex.SubExpressionLengths[GroupIndex]; end; until not Regex.MatchAgain; end else memo2.Lines.Add('No-Matches Found'); end; end. DFM object Form2: TForm2 Left = 0 Top = 0 Caption = 'Form2' ClientHeight = 247 ClientWidth = 480 Color = clBtnFace Font.Charset = DEFAULT_CHARSET Font.Color = clWindowText Font.Height = -11 Font.Name = 'Tahoma' Font.Style = [] OldCreateOrder = False PixelsPerInch = 96 TextHeight = 13 object Memo1: TMemo Left = 8 Top = 8 Width = 185 Height = 89 Lines.Strings = ( 'var showImpressions = false; var ' 'criteriaSuggestor = ' '&#39;sensei_keyword&#39;; var ' 'historicalTimePeriod = &#39;Mar ' '2009 - Feb 2010&#39;; var ' 'historicalStartMonth = 2; var ' 'impressionTimePeriod = ' '&#39;February&#39;; var ' 'criteriaGroupsArray = new Array(); ' 'var captchaError = false; var ' 'quotaExceeded = false;' 'var criteria = new Array();' 'var monthlyVariation = new ' 'Array();' 'monthlyVariation.push(new ' 'kpMonthlyPopularity(' '0.52' ')); monthlyVariation.push(new ' 'kpMonthlyPopularity(' '0.67' ')); monthlyVariation.push(new ' 'kpMonthlyPopularity(' '0.82' ')); monthlyVariation.push(new ' 'kpMonthlyPopularity(' '1.0' ')); monthlyVariation.push(new ' 'kpMonthlyPopularity(' '0.73' ')); monthlyVariation.push(new ' 'kpMonthlyPopularity(' '0.5' ')); monthlyVariation.push(new ' 'kpMonthlyPopularity(' '0.45' ')); monthlyVariation.push(new ' 'kpMonthlyPopularity(' '0.45' ')); monthlyVariation.push(new ' 'kpMonthlyPopularity(' '0.43' ')); monthlyVariation.push(new ' 'kpMonthlyPopularity(' '0.4' ')); monthlyVariation.push(new ' 'kpMonthlyPopularity(' '0.47' ')); monthlyVariation.push(new ' 'kpMonthlyPopularity(' '0.45' '));' 'criteria.push(new ' 'kpCriterion(&#39;thunderstorm&#3' '9;, 1.9117305278778076,' #39'201,000'#39', '#39'550,000'#39', 201000, ' '550000, 0.8666667' ',' '&#39;$0.49&#39;, 493102,' '&#39;1 - 3&#39;, 2' ',' '0' ',' '0' ',' 'monthlyVariation,' '5' ',' '&#39;&#39;' ',' 'kpView.MATCH_BROAD' ',' '0' ')); var monthlyVariation = new ' 'Array();' 'monthlyVariation.push(new ' 'kpMonthlyPopularity(' '0.57' ')); monthlyVariation.push(new ' 'kpMonthlyPopularity(' '1.0' ')); monthlyVariation.push(new ' 'kpMonthlyPopularity(' '0.7' ')); monthlyVariation.push(new ' 'kpMonthlyPopularity(' '0.57' ')); monthlyVariation.push(new ' 'kpMonthlyPopularity(' '0.45' ')); monthlyVariation.push(new ' 'kpMonthlyPopularity(' '0.42' ')); monthlyVariation.push(new ' 'kpMonthlyPopularity(' '0.47' ')); monthlyVariation.push(new ' 'kpMonthlyPopularity(' '0.46' ')); monthlyVariation.push(new ' 'kpMonthlyPopularity(' '0.43' ')); monthlyVariation.push(new ' 'kpMonthlyPopularity(' '0.36' ')); monthlyVariation.push(new ' 'kpMonthlyPopularity(' '0.45' ')); monthlyVariation.push(new ' 'kpMonthlyPopularity(' '0.43' '));' 'criteria.push(new ' 'kpCriterion(&#39;[thunderstorm]&' '#39;, 1.9117305278778076,' #39'33,100'#39', '#39'90,500'#39', 33100, 90500, ' '0.8666667' ',' '&#39;$0.49&#39;, 493102,' '&#39;1 - 3&#39;, 2' ',' '0' ',' '0' ',' 'monthlyVariation,' '3' ',' '&#39;&#39;' ',' 'kpView.MATCH_EXACT' ',' '0' ')); var monthlyVariation = new ' 'Array();' 'monthlyVariation.push(new ' 'kpMonthlyPopularity(' '0.52' ')); monthlyVariation.push(new ' 'kpMonthlyPopularity(' '0.67' ')); monthlyVariation.push(new ' 'kpMonthlyPopularity(' '0.82' ')); monthlyVariation.push(new ' 'kpMonthlyPopularity(' '1.0' ')); monthlyVariation.push(new ' 'kpMonthlyPopularity(' '0.73' ')); monthlyVariation.push(new ' 'kpMonthlyPopularity(' '0.5' ')); monthlyVariation.push(new ' 'kpMonthlyPopularity(' '0.45' ')); monthlyVariation.push(new ' 'kpMonthlyPopularity(' '0.45' ')); monthlyVariation.push(new ' 'kpMonthlyPopularity(' '0.43' ')); monthlyVariation.push(new ' 'kpMonthlyPopularity(' '0.4' ')); monthlyVariation.push(new ' 'kpMonthlyPopularity(' '0.47' ')); monthlyVariation.push(new ' 'kpMonthlyPopularity(' '0.45' '));' 'criteria.push(new ' 'kpCriterion(&#39;\42thunderstorm\' '042&#39;, 1.9117305278778076,' #39'201,000'#39', '#39'450,000'#39', 201000, ' '450000, 0.8666667' ',' '&#39;$0.49&#39;, 493102,' '&#39;1 - 3&#39;, 2' ',' '0' ',' '0' ',' 'monthlyVariation,' '5' ',' '&#39;&#39;' ',' 'kpView.MATCH_PHRASE' ',' '0' ')); var monthlyVariation = new ' 'Array();' 'monthlyVariation.push(new ' 'kpMonthlyPopularity(' '0.75' ')); monthlyVariation.push(new ' 'kpMonthlyPopularity(' '0.81' ')); monthlyVariation.push(new ' 'kpMonthlyPopularity(' '1.0' ')); monthlyVariation.push(new ' 'kpMonthlyPopularity(' '0.87' ')); monthlyVariation.push(new ' 'kpMonthlyPopularity(' '0.64' ')); monthlyVariation.push(new ' 'kpMonthlyPopularity(' '0.56' ')); monthlyVariation.push(new ' 'kpMonthlyPopularity(' '0.52' ')); monthlyVariation.push(new ' 'kpMonthlyPopularity(' '0.6' ')); monthlyVariation.push(new ' 'kpMonthlyPopularity(' '0.53' ')); monthlyVariation.push(new ' 'kpMonthlyPopularity(' '0.47' ')); monthlyVariation.push(new ' 'kpMonthlyPopularity(' '0.58' ')); monthlyVariation.push(new ' 'kpMonthlyPopularity(' '0.61' '));' 'criteria.push(new ' 'kpCriterion(&#39;thunderstorms&#' '39;, 1.8268921375274658,' #39'110,000'#39', '#39'201,000'#39', 110000, ' '201000, 0.8' ',' '&#39;$0.56&#39;, 559074,' '&#39;1 - 3&#39;, 2' ',' '0' ',' '0' ',' 'monthlyVariation,' '4' ',' '&#39;&#39;' ',' 'kpView.MATCH_BROAD' ',' '0' ')); var monthlyVariation = new ' 'Array();' 'monthlyVariation.push(new ' 'kpMonthlyPopularity(' '0.83' ')); monthlyVariation.push(new ' 'kpMonthlyPopularity(' '0.82' ')); monthlyVariation.push(new ' 'kpMonthlyPopularity(' '1.0' ')); monthlyVariation.push(new ' 'kpMonthlyPopularity(' '0.67' ')); monthlyVariation.push(new ' 'kpMonthlyPopularity(' '0.42' ')); monthlyVariation.push(new ' 'kpMonthlyPopularity(' '0.41' ')); monthlyVariation.push(new ' 'kpMonthlyPopularity(' '0.47' ')); monthlyVariation.push(new ' 'kpMonthlyPopularity(' '0.56' ')); monthlyVariation.push(new ' 'kpMonthlyPopularity(' '0.47' ')); monthlyVariation.push(new ' 'kpMonthlyPopularity(' '0.39' ')); monthlyVariation.push(new ' 'kpMonthlyPopularity(' '0.5' ')); monthlyVariation.push(new ' 'kpMonthlyPopularity(' '0.51' '));' 'criteria.push(new ' 'kpCriterion(&#39;[thunderstorms]&' '#39;, 1.8268921375274658,' #39'22,200'#39', '#39'40,500'#39', 22200, 40500, ' '0.8' ',' '&#39;$0.56&#39;, 559074,' '&#39;1 - 3&#39;, 2' ',' '0' ',' '0' ',' 'monthlyVariation,' '4' ',' '&#39;&#39;' ',' 'kpView.MATCH_EXACT' ',' '0' ')); var monthlyVariation = new ' 'Array();' 'monthlyVariation.push(new ' 'kpMonthlyPopularity(' '0.75' ')); monthlyVariation.push(new ' 'kpMonthlyPopularity(' '0.81' ')); monthlyVariation.push(new ' 'kpMonthlyPopularity(' '1.0' ')); monthlyVariation.push(new ' 'kpMonthlyPopularity(' '0.87' ')); monthlyVariation.push(new ' 'kpMonthlyPopularity(' '0.64' ')); monthlyVariation.push(new ' 'kpMonthlyPopularity(' '0.56' ')); monthlyVariation.push(new ' 'kpMonthlyPopularity(' '0.52' ')); monthlyVariation.push(new ' 'kpMonthlyPopularity(' '0.6' ')); monthlyVariation.push(new ' 'kpMonthlyPopularity(' '0.53' ')); monthlyVariation.push(new ' 'kpMonthlyPopularity(' '0.47' ')); monthlyVariation.push(new ' 'kpMonthlyPopularity(' '0.58' ')); monthlyVariation.push(new ' 'kpMonthlyPopularity(' '0.61' '));' 'criteria.push(new ' 'kpCriterion(&#39;\42thunderstorms' '\042&#39;, 1.8268921375274658,' #39'110,000'#39', '#39'165,000'#39', 110000, ' '165000, 0.8' ',' '&#39;$0.56&#39;, 559074,' '&#39;1 - 3&#39;, 2' ',' '0' ',' '0' ',' 'monthlyVariation,' '4' ',' '&#39;&#39;' ',' 'kpView.MATCH_PHRASE' ',' '0' ')); var monthlyVariation = new ' 'Array();' 'monthlyVariation.push(new ' 'kpMonthlyPopularity(' '0.71' ')); monthlyVariation.push(new ' 'kpMonthlyPopularity(' '0.73' ')); monthlyVariation.push(new ' 'kpMonthlyPopularity(' '0.82' ')); monthlyVariation.push(new ' 'kpMonthlyPopularity(' '1.0' ')); monthlyVariation.push(new ' 'kpMonthlyPopularity(' '0.87' ')); monthlyVariation.push(new ' 'kpMonthlyPopularity(' '0.92' ')); monthlyVariation.push(new ' 'kpMonthlyPopularity(' '0.82' ')); monthlyVariation.push(new ' 'kpMonthlyPopularity(' '0.7' ')); monthlyVariation.push(new ' 'kpMonthlyPopularity(' '0.75' ')); monthlyVariation.push(new ' 'kpMonthlyPopularity(' '0.68' ')); monthlyVariation.push(new ' 'kpMonthlyPopularity(' '0.77' ')); monthlyVariation.push(new ' 'kpMonthlyPopularity(' '0.79' '));' 'criteria.push(new ' 'kpCriterion(&#39;lightning ' 'storm&#39;, 1.774579644203186,' #39'49,500'#39', '#39'90,500'#39', 49500, 90500, ' '0.73333335' ',' '&#39;$0.54&#39;, 535666,' '&#39;1 - 3&#39;, 2' ',' '0' ',' '0' ',' 'monthlyVariation,' '5' ',' '&#39;&#39;' ',' 'kpView.MATCH_BROAD' ',' '0' ')); var monthlyVariation = new ' 'Array();' 'monthlyVariation.push(new ' 'kpMonthlyPopularity(' '0.76' ')); monthlyVariation.push(new ' 'kpMonthlyPopularity(' '0.87' ')); monthlyVariation.push(new ' 'kpMonthlyPopularity(' '0.97' ')); monthlyVariation.push(new ' 'kpMonthlyPopularity(' '1.0' ')); monthlyVariation.push(new ' 'kpMonthlyPopularity(' '0.87' ')); monthlyVariation.push(new ' 'kpMonthlyPopularity(' '1.0' ')); monthlyVariation.push(new ' 'kpMonthlyPopularity(' '0.98' ')); monthlyVariation.push(new ' 'kpMonthlyPopularity(' '0.87' ')); monthlyVariation.push(new ' 'kpMonthlyPopularity(' '0.84' ')); monthlyVariation.push(new ' 'kpMonthlyPopularity(' '0.68' ')); monthlyVariation.push(new ' 'kpMonthlyPopularity(' '0.86' ')); monthlyVariation.push(new ' 'kpMonthlyPopularity(' '0.81' '));' 'criteria.push(new ' 'kpCriterion(&#39;[lightning ' 'storm]&#39;, 1.774579644203186,' #39'12,100'#39', '#39'22,200'#39', 12100, 22200, ' '0.73333335' ',' '&#39;$0.54&#39;, 535666,' '&#39;1 - 3&#39;, 2' ',' '0' ',' '0' ',' 'monthlyVariation,' '5' ',' '&#39;&#39;' ',' 'kpView.MATCH_EXACT' ',' '0' ')); var monthlyVariation = new ' 'Array();' 'monthlyVariation.push(new ' 'kpMonthlyPopularity(' '0.68' ')); monthlyVariation.push(new ' 'kpMonthlyPopularity(' '0.72' ')); monthlyVariation.push(new ' 'kpMonthlyPopularity(' '0.81' ')); monthlyVariation.push(new ' 'kpMonthlyPopularity(' '1.0' ')); monthlyVariation.push(new ' 'kpMonthlyPopularity(' '0.85' ')); monthlyVariation.push(new ' 'kpMonthlyPopularity(' '0.92' ')); monthlyVariation.push(new ' 'kpMonthlyPopularity(' '0.81' ')); monthlyVariation.push(new ' 'kpMonthlyPopularity(' '0.67' ')); monthlyVariation.push(new ' 'kpMonthlyPopularity(' '0.71' ')); monthlyVariation.push(new ' 'kpMonthlyPopularity(' '0.65' ')); monthlyVariation.push(new ' 'kpMonthlyPopularity(' '0.76' ')); monthlyVariation.push(new ' 'kpMonthlyPopularity(' '0.73' '));' 'criteria.push(new ' 'kpCriterion(&#39;\42lightning ' 'storm\042&#39;, ' '1.774579644203186,' #39'33,100'#39', '#39'60,500'#39', 33100, 60500, ' '0.73333335' ',' '&#39;$0.54&#39;, 535666,' '&#39;1 - 3&#39;, 2' ',' '0' ',' '0' ',' 'monthlyVariation,' '5' ',' '&#39;&#39;' ',' 'kpView.MATCH_PHRASE' ',' '0' ')); var monthlyVariation = new ' 'Array();' 'monthlyVariation.push(new ' 'kpMonthlyPopularity(' '0.69' ')); monthlyVariation.push(new ' 'kpMonthlyPopularity(' '0.69' ')); monthlyVariation.push(new ' 'kpMonthlyPopularity(' '0.71' ')); monthlyVariation.push(new ' 'kpMonthlyPopularity(' '0.66' ')); monthlyVariation.push(new ' 'kpMonthlyPopularity(' '0.68' ')); monthlyVariation.push(new ' 'kpMonthlyPopularity(' '0.7' ')); monthlyVariation.push(new ' 'kpMonthlyPopularity(' '0.75' ')); monthlyVariation.push(new ' 'kpMonthlyPopularity(' '0.79' ')); monthlyVariation.push(new ' 'kpMonthlyPopularity(' '0.74' ')); monthlyVariation.push(new ' 'kpMonthlyPopularity(' '0.72' ')); monthlyVariation.push(new ' 'kpMonthlyPopularity(' '1.0' ')); monthlyVariation.push(new ' 'kpMonthlyPopularity(' '0.7' '));' 'criteria.push(new ' 'kpCriterion(&#39;rain storm&#39;, ' '1.7464053630828857,' #39'27,100'#39', '#39'49,500'#39', 27100, 49500, ' '0.6666667' ',' '&#39;$0.53&#39;, 526334,' '&#39;1 - 3&#39;, 2' ',' '0' ',' '0' ',' 'monthlyVariation,' '0' ',' '&#39;&#39;' ',' 'kpView.MATCH_BROAD' ',' '0' ')); var monthlyVariation = new ' 'Array();' 'monthlyVariation.push(new ' 'kpMonthlyPopularity(' '1.0' ')); monthlyVariation.push(new ' 'kpMonthlyPopularity(' '0.87' ')); monthlyVariation.push(new ' 'kpMonthlyPopularity(' '0.79' ')); monthlyVariation.push(new ' 'kpMonthlyPopularity(' '0.57' ')); monthlyVariation.push(new ' 'kpMonthlyPopularity(' '0.55' ')); monthlyVariation.push(new ' 'kpMonthlyPopularity(' '0.57' ')); monthlyVariation.push(new ' 'kpMonthlyPopularity(' '0.74' ')); monthlyVariation.push(new ' 'kpMonthlyPopularity(' '0.76' ')); monthlyVariation.push(new ' 'kpMonthlyPopularity(' '0.69' ')); monthlyVariation.push(new ' 'kpMonthlyPopularity(' '0.61' ')); monthlyVariation.push(new ' 'kpMonthlyPopularity(' '0.89' ')); monthlyVariation.push(new ' 'kpMonthlyPopularity(' '0.73' '));' 'criteria.push(new ' 'kpCriterion(&#39;[rain ' 'storm]&#39;, ' '1.7464053630828857,' #39'5,400'#39', '#39'8,100'#39', 5400, 8100, ' '0.6666667' ',' '&#39;$0.53&#39;, 526334,' '&#39;1 - 3&#39;, 2' ',' '0' ',' '0' ',' 'monthlyVariation,' '2' ',' '&#39;&#39;' ',' 'kpView.MATCH_EXACT' ',' '0' ')); var monthlyVariation = new ' 'Array();' 'monthlyVariation.push(new ' 'kpMonthlyPopularity(' '0.73' ')); monthlyVariation.push(new ' 'kpMonthlyPopularity(' '0.7' ')); monthlyVariation.push(new ' 'kpMonthlyPopularity(' '0.68' ')); monthlyVariation.push(new ' 'kpMonthlyPopularity(' '0.61' ')); monthlyVariation.push(new ' 'kpMonthlyPopularity(' '0.68' ')); monthlyVariation.push(new ' 'kpMonthlyPopularity(' '0.69' ')); monthlyVariation.push(new ' 'kpMonthlyPopularity(' '0.73' ')); monthlyVariation.push(new ' 'kpMonthlyPopularity(' '0.72' ')); monthlyVariation.push(new ' 'kpMonthlyPopularity(' '0.62' ')); monthlyVariation.push(new ' 'kpMonthlyPopularity(' '0.59' ')); monthlyVariation.push(new ' 'kpMonthlyPopularity(' '1.0' ')); monthlyVariation.push(new ' 'kpMonthlyPopularity(' '0.66' '));' 'criteria.push(new ' 'kpCriterion(&#39;\42rain ' 'storm\042&#39;, ' '1.7464053630828857,' #39'14,800'#39', '#39'27,100'#39', 14800, 27100, ' '0.6666667' ',' '&#39;$0.53&#39;, 526334,' '&#39;1 - 3&#39;, 2' ',' '0' ',' '0' ',' 'monthlyVariation,' '0' ',' '&#39;&#39;' ',' 'kpView.MATCH_PHRASE' ',' '0' ')); var monthlyVariation = new ' 'Array();' 'monthlyVariation.push(new ' 'kpMonthlyPopularity(' '0.82' ')); monthlyVariation.push(new ' 'kpMonthlyPopularity(' '0.87' ')); monthlyVariation.push(new ' 'kpMonthlyPopularity(' '1.0' ')); monthlyVariation.push(new ' 'kpMonthlyPopularity(' '1.0' ')); monthlyVariation.push(new ' 'kpMonthlyPopularity(' '0.78' ')); monthlyVariation.push(new ' 'kpMonthlyPopularity(' '0.82' ')); monthlyVariation.push(new ' 'kpMonthlyPopularity(' '0.84' ')); monthlyVariation.push(new ' 'kpMonthlyPopularity(' '0.79' ')); monthlyVariation.push(new ' 'kpMonthlyPopularity(' '0.77' ')); monthlyVariation.push(new ' 'kpMonthlyPopularity(' '0.61' ')); monthlyVariation.push(new ' 'kpMonthlyPopularity(' '0.92' ')); monthlyVariation.push(new ' 'kpMonthlyPopularity(' '0.82' '));' 'criteria.push(new ' 'kpCriterion(&#39;lightning ' 'storms&#39;, ' '1.6842896938323975,' #39'14,800'#39', '#39'27,100'#39', 14800, 27100, ' '0.73333335' ',' '&#39;$0.42&#39;, 417108,' '&#39;1 - 3&#39;, 2' ',' '0' ',' '0' ',' 'monthlyVariation,' '4' ',' '&#39;&#39;' ',' 'kpView.MATCH_BROAD' ',' '0' ')); var monthlyVariation = new ' 'Array();' 'monthlyVariation.push(new ' 'kpMonthlyPopularity(' '0.9' ')); monthlyVariation.push(new ' 'kpMonthlyPopularity(' '0.9' ')); monthlyVariation.push(new ' 'kpMonthlyPopularity(' '1.0' ')); monthlyVariation.push(new ' 'kpMonthlyPopularity(' '0.84' ')); monthlyVariation.push(new ' 'kpMonthlyPopularity(' '0.7' ')); monthlyVariation.push(new ' 'kpMonthlyPopularity(' '0.81' ')); monthlyVariation.push(new ' 'kpMonthlyPopularity(' '0.88' ')); monthlyVariation.push(new ' 'kpMonthlyPopularity(' '0.77' ')); monthlyVariation.push(new ' 'kpMonthlyPopularity(' '0.76' ')); monthlyVariation.push(new ' 'kpMonthlyPopularity(' '0.57' ')); monthlyVariation.push(new ' 'kpMonthlyPopularity(' '0.75' ')); monthlyVariation.push(new ' 'kpMonthlyPopularity(' '0.63' '));' 'criteria.push(new ' 'kpCriterion(&#39;[lightning ' 'storms]&#39;, ' '1.6842896938323975,' #39'3,600'#39', '#39'8,100'#39', 3600, 8100, ' '0.73333335' ',' '&#39;$0.42&#39;, 417108,' '&#39;1 - 3&#39;, 2' ',' '0' ',' '0' ',' 'monthlyVariation,' '4' ',' '&#39;&#39;' ',' 'kpView.MATCH_EXACT' ',' '0' ')); var monthlyVariation = new ' 'Array();' 'monthlyVariation.push(new ' 'kpMonthlyPopularity(' '0.8' ')); monthlyVariation.push(new ' 'kpMonthlyPopularity(' '0.86' ')); monthlyVariation.push(new ' 'kpMonthlyPopularity(' '1.0' ')); monthlyVariation.push(new ' 'kpMonthlyPopularity(' '0.99' ')); monthlyVariation.push(new ' 'kpMonthlyPopularity(' '0.77' ')); monthlyVariation.push(new ' 'kpMonthlyPopularity(' '0.83' ')); monthlyVariation.push(new ' 'kpMonthlyPopularity(' '0.85' ')); monthlyVariation.push(new ' 'kpMonthlyPopularity(' '0.78' ')); monthlyVariation.push(new ' 'kpMonthlyPopularity(' '0.77' ')); monthlyVariation.push(new ' 'kpMonthlyPopularity(' '0.6' ')); monthlyVariation.push(new ' 'kpMonthlyPopularity(' '0.91' ')); monthlyVariation.push(new ' 'kpMonthlyPopularity(' '0.81' '));' 'criteria.push(new ' 'kpCriterion(&#39;\42lightning ' 'storms\042&#39;, ' '1.6842896938323975,' #39'12,100'#39', '#39'22,200'#39', 12100, 22200, ' '0.73333335' ',' '&#39;$0.42&#39;, 417108,' '&#39;1 - 3&#39;, 2' ',' '0' ',' '0' ',' 'monthlyVariation,' '4' ',' '&#39;&#39;' ',' 'kpView.MATCH_PHRASE' ',' '0' ')); var monthlyVariation =

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• gcc 4.5 installation problem under ubuntu

  - by Claire Huang

  I tried to install gcc 4.5 on ubuntu 10.04 but failed. Here is a compile error that I don't know how to solve. Is there anyone successfully install the latest gcc on ubuntu? Following is my steps and the error message, I'd like to know where is the problem.... Step1: download these files: gcc-core-4.5.0.tar.gz gcc-g++-4.5.0.tar.gz gmp-4.3.2.tar.bz2 mpc-0.8.1.tar.gz mpfr-2.4.2.tar.gz Step2: Unzip above files Step3: move gmp, mpc, mpfr to the gcc-4.5.0/ directory. mv gmp-4.3.2 gcc-4.5.0/gmp mv mpc-0.8.1 gcc-4.5.0/mpc mv mpfr-2.4.2 gcc-4.5.0/mpfr Step4: go to gcc-4.5.0 directory and do configuration: sudo ./configure Step5: compile and install sudo make sudo make install The first 4 steps is OK, I can configure it successfully. However, when I try to compile it, following error message comes out, I cannot figure out what the problem is. Should I change the name from "gcc 4.5" to "gcc"?? It's a little strange that we need to do this by ourself. Is there anything I missed during the installation? xxx@xxx-laptop:/media/Data/Tool/linux/gcc 4.5/gcc-4.5.0$ sudo make [sudo] password for xxx: [ -f stage_final ] || echo stage3 > stage_final /bin/bash: line 2: test: /media/Data/Tool/linux/gcc: binary operator expected /bin/bash: /media/Data/Tool/linux/gcc: No such file or directory make[1]: Entering directory `/media/Data/Tool/linux/gcc 4.5/gcc-4.5.0' make[2]: Entering directory `/media/Data/Tool/linux/gcc 4.5/gcc-4.5.0' make[3]: Entering directory `/media/Data/Tool/linux/gcc 4.5/gcc-4.5.0' rm -f stage_current make[3]: Leaving directory `/media/Data/Tool/linux/gcc 4.5/gcc-4.5.0' make[2]: Leaving directory `/media/Data/Tool/linux/gcc 4.5/gcc-4.5.0' make[2]: Entering directory `/media/Data/Tool/linux/gcc 4.5/gcc-4.5.0' Configuring stage 1 in host-x86_64-unknown-linux-gnu/intl /bin/bash: /media/Data/Tool/linux/gcc: No such file or directory make[2]: *** [configure-stage1-intl] Error 127 make[2]: Leaving directory `/media/Data/Tool/linux/gcc 4.5/gcc-4.5.0' make[1]: *** [stage1-bubble] Error 2 make[1]: Leaving directory `/media/Data/Tool/linux/gcc 4.5/gcc-4.5.0' make: *** [all] Error 2

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• Hive NR map progress inconsistent and regurlarly restart from 0%

  - by user92471

  I have a Yarn MR (with two ec2 instances to mapreduce) job on a dataset of approximately a thousand avro records, and the map phase is behaving erratically. See the progress below. Of course i checked the logs on resourcemanager and nodemanagers and saw nothing suspicious, but these logs are too verbose What is going on there ? hive> select * from nikon where qs_cs_s_aid='VIEW' limit 10; Total MapReduce jobs = 1 Launching Job 1 out of 1 Number of reduce tasks is set to 0 since there's no reduce operator Starting Job = job_1352281315350_0020, Tracking URL = http://blabla.ec2.internal:8088/proxy/application_1352281315350_0020/ Kill Command = /usr/lib/hadoop/bin/hadoop job -Dmapred.job.tracker=blabla.com:8032 -kill job_1352281315350_0020 Hadoop job information for Stage-1: number of mappers: 4; number of reducers: 0 2012-11-07 11:14:40,976 Stage-1 map = 0%, reduce = 0% 2012-11-07 11:15:06,136 Stage-1 map = 1%, reduce = 0%, Cumulative CPU 10.38 sec 2012-11-07 11:15:07,253 Stage-1 map = 1%, reduce = 0%, Cumulative CPU 12.18 sec 2012-11-07 11:15:08,371 Stage-1 map = 1%, reduce = 0%, Cumulative CPU 12.18 sec 2012-11-07 11:15:09,491 Stage-1 map = 1%, reduce = 0%, Cumulative CPU 12.18 sec 2012-11-07 11:15:10,643 Stage-1 map = 2%, reduce = 0%, Cumulative CPU 15.42 sec (...) 2012-11-07 11:15:35,441 Stage-1 map = 28%, reduce = 0%, Cumulative CPU 37.77 sec 2012-11-07 11:15:36,486 Stage-1 map = 28%, reduce = 0%, Cumulative CPU 37.77 sec here restart at 16% ? 2012-11-07 11:15:37,692 Stage-1 map = 16%, reduce = 0%, Cumulative CPU 21.15 sec 2012-11-07 11:15:38,815 Stage-1 map = 16%, reduce = 0%, Cumulative CPU 21.15 sec 2012-11-07 11:15:39,865 Stage-1 map = 16%, reduce = 0%, Cumulative CPU 21.15 sec 2012-11-07 11:15:41,064 Stage-1 map = 18%, reduce = 0%, Cumulative CPU 22.4 sec 2012-11-07 11:15:42,181 Stage-1 map = 18%, reduce = 0%, Cumulative CPU 22.4 sec 2012-11-07 11:15:43,299 Stage-1 map = 18%, reduce = 0%, Cumulative CPU 22.4 sec here restart at 0% ? 2012-11-07 11:15:44,418 Stage-1 map = 0%, reduce = 0% 2012-11-07 11:16:02,076 Stage-1 map = 1%, reduce = 0%, Cumulative CPU 6.86 sec 2012-11-07 11:16:03,193 Stage-1 map = 1%, reduce = 0%, Cumulative CPU 6.86 sec 2012-11-07 11:16:04,259 Stage-1 map = 2%, reduce = 0%, Cumulative CPU 8.45 sec (...) 2012-11-07 11:16:31,291 Stage-1 map = 22%, reduce = 0%, Cumulative CPU 35.34 sec 2012-11-07 11:16:32,414 Stage-1 map = 26%, reduce = 0%, Cumulative CPU 37.93 sec here restart at 11% ? 2012-11-07 11:16:33,459 Stage-1 map = 11%, reduce = 0%, Cumulative CPU 19.53 sec 2012-11-07 11:16:34,507 Stage-1 map = 11%, reduce = 0%, Cumulative CPU 19.53 sec 2012-11-07 11:16:35,731 Stage-1 map = 13%, reduce = 0%, Cumulative CPU 21.47 sec (...) 2012-11-07 11:16:46,839 Stage-1 map = 17%, reduce = 0%, Cumulative CPU 24.14 sec here restart at 0% ? 2012-11-07 11:16:47,939 Stage-1 map = 0%, reduce = 0% 2012-11-07 11:16:56,653 Stage-1 map = 1%, reduce = 0%, Cumulative CPU 7.54 sec 2012-11-07 11:16:57,814 Stage-1 map = 1%, reduce = 0%, Cumulative CPU 7.54 sec (...) Needless to say the job crashes after some time with an Error: java.io.IOException: java.io.IOException: java.lang.ArrayIndexOutOfBoundsException: -56

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• C# 4.0 'dynamic' and foreach statement

  - by ControlFlow

  Not long time before I've discovered, that new dynamic keyword doesn't work well with the C#'s foreach statement: using System; sealed class Foo { public struct FooEnumerator { int value; public bool MoveNext() { return true; } public int Current { get { return value++; } } } public FooEnumerator GetEnumerator() { return new FooEnumerator(); } static void Main() { foreach (int x in new Foo()) { Console.WriteLine(x); if (x >= 100) break; } foreach (int x in (dynamic)new Foo()) { // :) Console.WriteLine(x); if (x >= 100) break; } } } I've expected that iterating over the dynamic variable should work completely as if the type of collection variable is known at compile time. I've discovered that the second loop actually is looked like this when is compiled: foreach (object x in (IEnumerable) /* dynamic cast */ (object) new Foo()) { ... } and every access to the x variable results with the dynamic lookup/cast so C# ignores that I've specify the correct x's type in the foreach statement - that was a bit surprising for me... And also, C# compiler completely ignores that collection from dynamically typed variable may implements IEnumerable<T> interface! The full foreach statement behavior is described in the C# 4.0 specification 8.8.4 The foreach statement article. But... It's perfectly possible to implement the same behavior at runtime! It's possible to add an extra CSharpBinderFlags.ForEachCast flag, correct the emmited code to looks like: foreach (int x in (IEnumerable<int>) /* dynamic cast with the CSharpBinderFlags.ForEachCast flag */ (object) new Foo()) { ... } And add some extra logic to CSharpConvertBinder: Wrap IEnumerable collections and IEnumerator's to IEnumerable<T>/IEnumerator<T>. Wrap collections doesn't implementing Ienumerable<T>/IEnumerator<T> to implement this interfaces. So today foreach statement iterates over dynamic completely different from iterating over statically known collection variable and completely ignores the type information, specified by user. All that results with the different iteration behavior (IEnumarble<T>-implementing collections is being iterated as only IEnumerable-implementing) and more than 150x slowdown when iterating over dynamic. Simple fix will results a much better performance: foreach (int x in (IEnumerable<int>) dynamicVariable) { But why I should write code like this? It's very nicely to see that sometimes C# 4.0 dynamic works completely the same if the type will be known at compile-time, but it's very sadly to see that dynamic works completely different where IT CAN works the same as statically typed code. So my question is: why foreach over dynamic works different from foreach over anything else?

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• Any significant performance improvement by using bitwise operators instead of plain int sums in C#?

  - by tunnuz

  Hello, I started working with C# a few weeks ago and I'm now in a situation where I need to build up a "bit set" flag to handle different cases in an algorithm. I have thus two options: enum RelativePositioning { LEFT = 0, RIGHT = 1, BOTTOM = 2, TOP = 3, FRONT = 4, BACK = 5 } pos = ((eye.X < minCorner.X ? 1 : 0) << RelativePositioning.LEFT) + ((eye.X > maxCorner.X ? 1 : 0) << RelativePositioning.RIGHT) + ((eye.Y < minCorner.Y ? 1 : 0) << RelativePositioning.BOTTOM) + ((eye.Y > maxCorner.Y ? 1 : 0) << RelativePositioning.TOP) + ((eye.Z < minCorner.Z ? 1 : 0) << RelativePositioning.FRONT) + ((eye.Z > maxCorner.Z ? 1 : 0) << RelativePositioning.BACK); Or: enum RelativePositioning { LEFT = 1, RIGHT = 2, BOTTOM = 4, TOP = 8, FRONT = 16, BACK = 32 } if (eye.X < minCorner.X) { pos += RelativePositioning.LEFT; } if (eye.X > maxCorner.X) { pos += RelativePositioning.RIGHT; } if (eye.Y < minCorner.Y) { pos += RelativePositioning.BOTTOM; } if (eye.Y > maxCorner.Y) { pos += RelativePositioning.TOP; } if (eye.Z > maxCorner.Z) { pos += RelativePositioning.FRONT; } if (eye.Z < minCorner.Z) { pos += RelativePositioning.BACK; } I could have used something as ((eye.X > maxCorner.X) << 1) but C# does not allow implicit casting from bool to int and the ternary operator was similar enough. My question now is: is there any performance improvement in using the first version over the second? Thank you Tommaso

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• Why not .NET-style delegates rather than closures in Java?

  - by h2g2java

  OK, this is going to be my beating a dying horse for the 3rd time. However, this question is different from my earlier two about closures/delegates, which asks about plans for delegates and what are the projected specs and implementation for closures. This question is about - why is the Java community struggling to define 3 different types of closures when we could simply steal the whole concept of delegates lock, stock and barrel from our beloved and friendly neighbour - Microsoft. There are two non-technical conclusions I would be very tempted to jump into: The Java community should hold up its pride, at the cost of needing to go thro convoluted efforts, by not succumbing to borrowing any Microsoft concepts or otherwise vindicate Microsoft's brilliance. Delegates is a Microsoft patented technology. Alright, besides the above two possibilities, Q1. Is there any weakness or inadequacy in msft-styled delegates that the three (or more) forms of closures would be addressing? Q2. I am asking this while shifting between java and c# and it intrigues me that c# delegates does exactly what I needed. Are there features that would be implemented in closures that are not currently available in C# delegates? If so what are they because I cannot see what I need more than what C# delegates has adequately provided me? Q3. I know that one of the concerns about implementing closures/delegates in java is the reduction of orthogonality of the language, where more than one way is exposed to perform a particular task. Is it worth the level convolution and time spent to avoid delegates just to ensure java retains its level of orthogonality? In SQL, we know that it is advisable to break orthogonality by frequently adequately satisfying only the 2nd normal form. Why can't java be subjected to reduction of orthogonality and OO-ness for the sake of simplicity? Q4. The architecture of JVM is technically constrained from implementing .NET-styled delegates. If this reason WERE (subjunctive to emphasize unlikelihood) true, then why can't the three closures proposals be hidden behind a simple delegate keyword or annotation: if we don't like to use @delegate, we could use @method. I cannot see how delegate statement format is more complex than the three closure proposals.

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• How does mysql define DISTINCT() in reference documentation

  - by goran

  EDIT: This question is about finding definitive reference to MySQL syntax on SELECT modifying keywords and functions. /EDIT AFAIK SQL defines two uses of DISTINCT keywords - SELECT DISTINCT field... and SELECT COUNT(DISTINCT field) ... However in one of web applications that I administer I've noticed performance issues on queries like SELECT DISTINCT(field1), field2, field3 ... DISTINCT() on a single column makes no sense and I am almost sure it is interpreted as SELECT DISTINCT field1, field2, field3 ... but how can I prove this? I've searched mysql site for a reference on this particular syntax, but could not find any. Does anyone have a link to definition of DISTINCT() in mysql or knows about other authoritative source on this? Best EDIT After asking the same question on mysql forums I learned that while parsing the SQL mysql does not care about whitespace between functions and column names (but I am still missing a reference). As it seems you can have whitespace between functions and the parenthesis SELECT LEFT (field1,1), field2... and get mysql to understand it as SELECT LEFT(field,1) Similarly SELECT DISTINCT(field1), field2... seems to get decomposed to SELECT DISTINCT (field1), field2... and then DISTINCT is taken not as some undefined (or undocumented) function, but as SELECT modifying keyword and the parenthesis around field1 are evaluated as if they were part of field expression. It would be great if someone would have a pointer to documentation where it is stated that the whitespace between functions and parenthesis is not significant or to provide links to apropriate MySQL forums, mailing lists where I could raise a question to put this into reference. EDIT I have found a reference to server option IGNORE SPACE. It states that "The IGNORE SPACE SQL mode can be used to modify how the parser treats function names that are whitespace-sensitive", later on it states that recent versions of mysql have reduced this number from 200 to 30. One of the remaining 30 is COUNT for example. With IGNORE SPACE enabled both SELECT COUNT(*) FROM mytable; SELECT COUNT (*) FROM mytable; are legal. So if this is an exception, I am left to conclude that normally functions ignore space by default. If functions ignore space by default then if the context is ambiguous, such as for the first function on a first item of the select expression, then they are not distinguishable from keywords and the error can not be thrown and MySQL must accept them as keywords. Still, my conclusions feel like they have lot of assumptions, I would still be grateful and accept any pointers to see where to follow up on this.

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