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  • No Rush, Defragging that Drive can Wait [Humorous Image]

    - by Asian Angel
    That drive is only fragmented a little bit…nothing to worry about there. View a Larger Version of the Image You should defragment this volume. Ya think?! [via Fail Desk] What’s the Difference Between Sleep and Hibernate in Windows? Screenshot Tour: XBMC 11 Eden Rocks Improved iOS Support, AirPlay, and Even a Custom XBMC OS How To Be Your Own Personal Clone Army (With a Little Photoshop)

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  • Sorry about the wait.

    - by Ratman21
    In the last two days have been trying remove “Iolo System Mechanic Professional” (With anti-virus and FireWall) from 3 of the 5 pc’s we have (3 lap tops and two Desk tops) as it was going to expire on the 13th.   So I could replace them with a free anti-virus (AVG) and just use the windows fire wall. I have been using the same set up on one of my desk tops (XP Pro) for 8 months and one of the Lap tops (Vista) for 5 months.   The problem was that System Mechanic did not want to go. Even after using the uninstall option on the desk top (my main PC, well its that because has the larger of all the PC’s hard drives but, is the oldest and runs XP home) and using Ccleaner to try and remove it.  It was still showing up as there and after I went a head and tried installing AVG and ran it. I found that the TCP/IP module was missing.  So no internet, I had to restore the PC back to the 1st to get the module back and then install AVG (after making sure window firewall was back on. I didn’t check that on the first try). Got the PC back to normal, very late last night. Only one of the two lap tops was easy but, even at that there are still some parts of System Mechanic on it but, AVG and firewall are working.   I may try an hunt down parts of System Mechanic on it and delete them on this lap top. Which was what finally had to do on the one of the Lap tops (also XP Home) as it would not uninstall after I restored the PC back to the 4th. So delete, delete, delete and Ccleaner (one dl file would not delete though). And I just finish installing AVG and now running a scan on the lap top. So all of this took two days (well three counting today). I started late Friday night and just finishing up now.   I only started this switch over after I had finished my Job search for day on Friday.   As for blogging on Tuesday, Wednesday and Thursday, I was busy and by the end of the day was too tired to blog, that and was hung up still on that 2nd dare of The Love Dare. So I cleaned the house, while she was out of the house. I mean, I cleaned, not just vacuumed house I cleaned the kitchen counter tops and the sinks. Did the dishes and some of the laundry over two of the those days.   As to the third day of Love Dare which is “Love is not selfish” and the dare “Whatever you put your time, energy, and money into will become more important to you. It’s hard to care for something you are not investing in. Along with restraining from negative comments, buy your spouse something that says, I was thinking of you today.”   Being on a very limited income, a lot of normal guy buying for girls is out (for one thing, the comment why did you waste our money on flowers, etc, etc, would come up. Not from me though). So that one is on hold till money issues are not a problem (no that does not mean never). The 4th day “Love is thoughtful” and the dare “Contact your spouse sometime during the business of the day. Have no agenda other than asking how he or she is doing and if there is anything you could do for them”.   I did this dare while I was still working with census last week and trying to do the dares. Well I start my CCNA classes Monday the 15th and I move on to the next Love Dare day “Love is not rude”.

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  • SSAS: Utility to check you have the correct data types and sizes in your cube definition

    - by DrJohn
    This blog describes a tool I developed which allows you to compare the data types and data sizes found in the cube’s data source view with the data types/sizes of the corresponding dimensional attribute.  Why is this important?  Well when creating named queries in a cube’s data source view, it is often necessary to use the SQL CAST or CONVERT operation to change the data type to something more appropriate for SSAS.  This is particularly important when your cube is based on an Oracle data source or using custom SQL queries rather than views in the relational database.   The problem with BIDS is that if you change the underlying SQL query, then the size of the data type in the dimension does not update automatically.  This then causes problems during deployment whereby processing the dimension fails because the data in the relational database is wider than that allowed by the dimensional attribute. In particular, if you use some string manipulation functions provided by SQL Server or Oracle in your queries, you may find that the 10 character string you expect suddenly turns into an 8,000 character monster.  For example, the SQL Server function REPLACE returns column with a width of 8,000 characters.  So if you use this function in the named query in your DSV, you will get a column width of 8,000 characters.  Although the Oracle REPLACE function is far more intelligent, the generated column size could still be way bigger than the maximum length of the data actually in the field. Now this may not be a problem when prototyping, but in your production cubes you really should clean up this kind of thing as these massive strings will add to processing times and storage space. Similarly, you do not want to forget to change the size of the dimension attribute if your database columns increase in size. Introducing CheckCubeDataTypes Utiltity The CheckCubeDataTypes application extracts all the data types and data sizes for all attributes in the cube and compares them to the data types and data sizes in the cube’s data source view.  It then generates an Excel CSV file which contains all this metadata along with a flag indicating if there is a mismatch between the DSV and the dimensional attribute.  Note that the app not only checks all the attribute keys but also the name and value columns for each attribute. Another benefit of having the metadata held in a CSV text file format is that you can place the file under source code control.  This allows you to compare the metadata of the previous cube release with your new release to highlight problems introduced by new development. You can download the C# source code from here: CheckCubeDataTypes.zip A typical example of the output Excel CSV file is shown below - note that the last column shows a data size mismatch by TRUE appearing in the column

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  • How to use UILongPressGestureRecognizer with sprite drag & wait?

    - by ganesh
    May be it's asked before also but I couldn't find any good answer. Please tell me how this can be implemented with UILongPressGestureRecognizer? A user drags a sprite from X location to Y location. Then it waits at Y location (touch is not ended yet) for 1 or 2 secs and release the touch i.e touch is ended. In this case, shouldn't following states be triggered in below order for UILongPressGestureRecognizer: UIGestureRecognizerStateBegan UIGestureRecognizerStateChanged UIGestureRecognizerStateEnded ? My problem is if UIPanGestureRecognizer is also implemented to handle drags, UILongPressGesture is never triggered even after Long waits. Any thoughts?

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  • All Link Types and SEO

    Website owners and clients alike tend to keep a close eye on forums and discussions on SEO link building, tend to have questions that about the types of links that are out there and how they are able to find acquire them. Below you will be provided information on the top 4 link types that you would want to have on your website. The natural one-way links is the one that is completely centered on good resources and content.

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  • Workflow 4.5 is Awesome, cant wait for 5.0!

    - by JoshReuben
    About 2 years ago I wrote a blog post describing what I would like to see in Workflow vnext: http://geekswithblogs.net/JoshReuben/archive/2010/08/25/workflow-4.0---not-there-yet.aspx At the time WF 4.0 was a little rough around the edges – the State Machine was on codeplex and people were simulating state machines with Flowcharts. Last year I built a near- realtime machine management system using WF 4.0.1 – its managing the internal operations of this device: http://landanano.com/products/commercial   Well WF 4.5 has come a long way – many of my gripes have been addressed: C# expressions - no more VB 'AndAlso' clauses state machine awesomeness - can query current state many designer improvements - Document Outline is so much more succinct than Designer! Separate WCF Service Contract interfaces and ability to generate activities from contract operations ability to rehydrate to updated flow definitions via DynamicUpdateMap and WorkflowIdentity you can read about the new features here: http://msdn.microsoft.com/en-us/library/hh305677(VS.110).aspx   2013 could be the year of Workflow evangelism for .NET, as it comes together as the DSL language. Eg on Azure it could be used to graphically orchestrate between WebRoles, WorkerRoles and AppFabric Queues and the ServiceBus – that would be grand.   Here’s a list of things I’d like to see in Workflow 5.0: Stronger Parallelism support for true multithreaded workflows . A Workflow executes on a single thread – wouldn’t it be great if we had the ability to model TPL DataFlow? Parallel is not really parallel, just allows AsyncCodeActivity.     support for recursion an ExpressionTree activity with an editor design surface a math activity pack return of application level protocol (3.51 WF services) – automatically expose a state machine as a WCF service with bookmark Receive activities generated from OperationContract automatically placed in state transition triggers. A new HTML5 ActivityDesigner control – support with different CSS3  skinnable hooks,  remote connectivity (had to roll my own) A data flow view – crucial to understanding the big picture Ability to refactor a Sequence to custom activity in a separate .xaml file – like Expression Blend does for UserControl state machine global error handling - if all states goto an error state, you quickly get visual spagetti. Now you could nest a state machine, but what if you want an application level protocol whereby each state exposes certain WCF ops. DSL RAD editing - Make the Document Outline into a DSL editor for adding activities  – For WF to really succeed as a higher level of abstraction, It needs to be more productive than raw coding - drag & drop on the designer is currently too slow compared to just typing code. Extensible Wizard API - for pluggable WF editor experience other execution models beyond Sequence, Flowchart & StateMachine: SSIS, Behavior Trees,  Wolfram Model tool – surprise us! improvements to Designer debugging API - SourceLocation is tied to XAML file line number and char position, and ModelService access seems convoluted - why not leverage WPF LogicalTreeHelper / VisualTreeHelper ? Workflow Team , keep on rocking!

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  • Sortie des spécifications d'OpenCL 1.2 : séparation compilation/linkage, partitionnement et support de nouveaux types de périphériques

    Sortie des spécifications d'OpenCL 1.2 Séparation compilation/linkage, partitionnement et support de nouveaux types de périphérique Le groupe Khronos vient de ratifier et publier les spécifications d'OpenCL 1.2 (Open Computing Language), l'API et extension standardisée du langage C pour supporter le développement sur GPU et la programmation parallèle distribuée sur plusieurs types de processeurs compatibles. Parmi les nouveautés de cette version, citons : Le partitionnement des périphériques permet de diviser un périphérique en plusieurs sous-périphériques pour contrôler directement les tâches assignées à chaque unité de calcul ; Séparation de la compilation et ...

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  • High I/O wait after login

    - by Jackson Tan
    I've noticed that the ubuntuone-syncdaemon hogs up the hard disk every time I log in to Ubuntu (10.04). This takes up to two or three minutes, which makes Ubuntu insufferably slow. Opening Firefox is okay, but the browser is constantly greyed out and lags horribly. Given that I often shut down my laptop when I don't use it (about 3 to 4 times a day), this makes Ubuntu lose much of its lustre because of its long boot time. Is this a normal behaviour of Ubuntu One? Is it intended? Note that I've actually posted this in the forums here, but I received only few replies.

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  • So, BizTalk 2010 Beta is out &hellip; wait, no it&rsquo;s not &hellip; wait

    - by Enrique Lima
    Over the last couple of days we have seen posts and “rumors” of the Beta availability.  There was a link to the bits from the Download Center, but then they were not. Documentation for it is available now at: BizTalk Server 2010 Documentation – Beta Microsoft BizTalk Server 2010 ESB Toolkit Documentation – Beta BizTalk RFID Server 2010 and BizTalk RFID Mobile 2010 Documentation – Beta But what about the bits?!? From the Biztalk Server Team blog: “We will be announcing the public Beta of BizTalk Server 2010 at the Application Infrastructure Virtual Launch tomorrow (Thursday, May 20th, 2010 at 8:30 AM PST) with planned RTM in Q3 of 2010. BizTalk Server 2010 aligns with the latest Microsoft platform releases, including SQL Server 2008 R2, Visual Studio 2010 and SharePoint 2010, and will integrate with Windows Server AppFabric and with .NET 4. At this virtual launch event we will disclose details on new features and capabilities in BizTalk Server 2010 though presentations, whitepapers, videos and recorded demos. Please join us tomorrow for an exciting launch! The BizTalk Team” Keep your eyes and ears at the ready.

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  • Control of File Types in Ubuntu

    <b>Packt:</b> "In this article by Delan Azabani, you'll learn how Ubuntu identifies file types, how to use Assogiate to control these processes, using Ubuntu Tweak to associate types with applications and use Bless to inspect binary files."

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  • Types in Lisp and Scheme

    - by user2054900
    I see now that Racket has types. At first glance it seems to be almost identical to Haskell typing. But is Lisp's CLOS covering some of the space Haskell types cover? Creating a very strict Haskell type and an object in any OO language seems vaguely similar. It's just that I've drunk some of the Haskell kool-aid and I'm totally paranoid that if I go down the Lisp road, I'll be screwed due to dynamic typing.

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  • How to lower wait time for repository updates

    - by Luis
    When doing a aptitude update / apt-get update or using the Update Manager to update sometimes I get to a repository link that takes too long. The percent does not end and it takes quite a while before it ignores it. How can I lower the time so that if a particular repository takes more than 10 seconds to connect or finish it should ignore it and move the following ones. Here is an image explaining the problem: It is trying to connect to archive.ubuntu.com but since it is taking too long it just sits there for at least 3 to 5 minutes (Haven't measured the time) and then it shows as ignored and moves to the following. I wish to change that to seconds instead of minutes.

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  • Wait for Unity 4.3? [on hold]

    - by RoarG
    We are currently in a pre-production of developing a 2d game in Unity but with the arrival of Unity 4.3 around the corner we were contemplating waiting for the release 4.3 instead of starting on 4.2, mainly since 4.3 got native 2d support. Is this something to be worried about, or do we need to start over to take use of the advantages that 4.3 brings, or does it matter at all? What benefits does one get in Unity 4.3, considering developing a 2d game? and is it a lot of tweaking to rework if we start the project before 4.3 release?

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  • Wait random number of minutes

    - by TiborKaraszi
    Why on earth would you want to do that? you ask. Say you have a job that is scheduled to start at the same time over a number of servers. This might be because you have an SQL Server Master/Target server environment (MSX/TSX) or you quite simply script a job and execute that script on several servers. You probably want to spread the load on your SAN and virtual machine host a bit. This is the exact reason I use this procedure. I frequently use MSX servers and I usually add a job step (executing this...(read more)

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  • What types of programming contest problems are there?

    - by Alex
    Basically, I want to make a great reference for use with programming contests that would have all of the algorithms that I can put together that I would need during a contest as well as sample useage for the code. I'm planning on making this into a sort of book that I could print off and take with me to competitions. I would like to do this rather than simply bringing other books (such as Algorithms books) because I think that I will learn a lot more by going over all of the algorithms myself as well as I would know exactly what I have in the book, making it more efficient to have and use. So, I've been doing research to determine what types of programming problems and algorithms are common on contests, and the only thing I can really find is this (which I have seen referenced a few times): Hal Burch conducted an analysis over spring break of 1999 and made an amazing discovery: there are only 16 types of programming contest problems! Furthermore, the top several comprise almost 80% of the problems seen at the IOI. Here they are: Dynamic Programming Greedy Complete Search Flood Fill Shortest Path Recursive Search Techniques Minimum Spanning Tree Knapsack Computational Geometry Network Flow Eulerian Path Two-Dimensional Convex Hull BigNums Heuristic Search Approximate Search Ad Hoc Problems The most challenging problems are Combination Problems which involve a loop (combinations, subsets, etc.) around one of the above algorithms - or even a loop of one algorithm with another inside it. These seem extraordinarily tricky to get right, even though conceptually they are ``obvious''. Now that's good and all, but that study was conducted in 1999, which was 13 years ago! One thing I know is that there are no BigNums problems any more (as Java has a BigInteger class, they have stopped making those problems). So, I'm wondering if anyone knows of any more recent studies of the types of problems that may be seen in a programming contest? Or what the most helpful algorithms on contests would be?

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  • Handling Types for Real and Complex Matrices in a BLAS Wrapper

    - by mga
    I come from a C background and I'm now learning OOP with C++. As an exercise (so please don't just say "this already exists"), I want to implement a wrapper for BLAS that will let the user write matrix algebra in an intuitive way (e.g. similar to MATLAB) e.g.: A = B*C*D.Inverse() + E.Transpose(); My problem is how to go about dealing with real (R) and complex (C) matrices, because of C++'s "curse" of letting you do the same thing in N different ways. I do have a clear idea of what it should look like to the user: s/he should be able to define the two separately, but operations would return a type depending on the types of the operands (R*R = R, C*C = C, R*C = C*R = C). Additionally R can be cast into C and vice versa (just by setting the imaginary parts to 0). I have considered the following options: As a real number is a special case of a complex number, inherit CMatrix from RMatrix. I quickly dismissed this as the two would have to return different types for the same getter function. Inherit RMatrix and CMatrix from Matrix. However, I can't really think of any common code that would go into Matrix (because of the different return types). Templates. Declare Matrix<T> and declare the getter function as T Get(int i, int j), and operator functions as Matrix *(Matrix RHS). Then specialize Matrix<double> and Matrix<complex>, and overload the functions. Then I couldn't really see what I would gain with templates, so why not just define RMatrix and CMatrix separately from each other, and then overload functions as necessary? Although this last option makes sense to me, there's an annoying voice inside my head saying this is not elegant, because the two are clearly related. Perhaps I'm missing an appropriate design pattern? So I guess what I'm looking for is either absolution for doing this, or advice on how to do better.

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  • Are specific types still necessary?

    - by MKO
    One thing that occurred to me the other day, are specific types still necessary or a legacy that is holding us back. What I mean is: do we really need short, int, long, bigint etc etc. I understand the reasoning, variables/objects are kept in memory, memory needs to be allocated and therefore we need to know how big a variable can be. But really, shouldn't a modern programming language be able to handle "adaptive types", ie, if something is only ever allocated in the shortint range it uses fewer bytes, and if something is suddenly allocated a very big number the memory is allocated accordinly for that particular instance. Float, real and double's are a bit trickier since the type depends on what precision you need. Strings should however be able to take upp less memory in many instances (in .Net) where mostly ascii is used buth strings always take up double the memory because of unicode encoding. One argument for specific types might be that it's part of the specification, ie for example a variable should not be able to be bigger than a certain value so we set it to shortint. But why not have type constraints instead? It would be much more flexible and powerful to be able to set permissible ranges and values on variables (and properties). I realize the immense problem in revamping the type architecture since it's so tightly integrated with underlying hardware and things like serialization might become tricky indeed. But from a programming perspective it should be great no?

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  • ActionResult types in MVC2

    - by rajbk
    In ASP.NET MVC, incoming browser requests gets mapped to a controller action method. The action method returns a type of ActionResult in response to the browser request. A basic example is shown below: public class HomeController : Controller { public ActionResult Index() { return View(); } } Here we have an action method called Index that returns an ActionResult. Inside the method we call the View() method on the base Controller. The View() method, as you will see shortly, is a method that returns a ViewResult. The ActionResult class is the base class for different controller results. The following diagram shows the types derived from the ActionResult type. ASP.NET has a description of these methods ContentResult – Represents a text result. EmptyResult – Represents no result. FileContentResult – Represents a downloadable file (with the binary content). FilePathResult – Represents a downloadable file (with a path). FileStreamResult – Represents a downloadable file (with a file stream). JavaScriptResult – Represents a JavaScript script. JsonResult – Represents a JavaScript Object Notation result that can be used in an AJAX application. PartialViewResult – Represents HTML and markup rendered by a partial view. RedirectResult – Represents a redirection to a new URL. RedirectToRouteResult – Represents a result that performs a redirection by using the specified route values dictionary. ViewResult – Represents HTML and markup rendered by a view. To return the types shown above, you call methods that are available in the Controller base class. A list of these methods are shown below.   Methods without an ActionResult return type The MVC framework will translate action methods that do not return an ActionResult into one. Consider the HomeController below which has methods that do not return any ActionResult types. The methods defined return an int, object and void respectfully. public class HomeController : Controller { public int Add(int x, int y) { return x + y; }   public Employee GetEmployee() { return new Employee(); }   public void DoNothing() { } } When a request comes in, the Controller class hands internally uses a ControllerActionInvoker class which inspects the action parameters and invokes the correct action method. The CreateActionResult method in the ControllerActionInvoker class is used to return an ActionResult. This method is shown below. If the result of the action method is null, an EmptyResult instance is returned. If the result is not of type ActionResult, the result is converted to a string and returned as a ContentResult. protected virtual ActionResult CreateActionResult(ControllerContext controllerContext, ActionDescriptor actionDescriptor, object actionReturnValue) { if (actionReturnValue == null) { return new EmptyResult(); }   ActionResult actionResult = (actionReturnValue as ActionResult) ?? new ContentResult { Content = Convert.ToString(actionReturnValue, CultureInfo.InvariantCulture) }; return actionResult; }   In the HomeController class above, the DoNothing method will return an instance of the EmptyResult() Renders an empty webpage the GetEmployee() method will return a ContentResult which contains a string that represents the current object Renders the text “MyNameSpace.Controllers.Employee” without quotes. the Add method for a request of /home/add?x=3&y=5 returns a ContentResult Renders the text “8” without quotes. Unit Testing The nice thing about the ActionResult types is in unit testing the controller. We can, without starting a web server, create an instance of the Controller, call the methods and verify that the type returned is the expected ActionResult type. We can then inspect the returned type properties and confirm that it contains the expected values. Enjoy! Sulley: Hey, Mike, this might sound crazy but I don't think that kid's dangerous. Mike: Really? Well, in that case, let's keep it. I always wanted a pet that could kill me.

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  • WebGrid Helper and Complex Types

    - by imran_ku07
        Introduction:           WebGrid helper makes it very easy to show tabular data. It was originally designed for ASP.NET Web Pages(WebMatrix) to display, edit, page and sort tabular data but you can also use this helper in ASP.NET Web Forms and ASP.NET MVC. When using this helper, sometimes you may run into a problem if you use complex types in this helper. In this article, I will show you how you can use complex types in WebGrid helper.       Description:             Let's say you need to show the employee data and you have the following classes,   public class Employee { public string Name { get; set; } public Address Address { get; set; } public List<string> ContactNumbers { get; set; } } public class Address { public string City { get; set; } }               The Employee class contain a Name, an Address and list of ContactNumbers. You may think that you can easily show City in WebGrid using Address.City, but no. The WebGrid helper will throw an exception at runtime if any Address property is null in the Employee list. Also, you cannot directly show ContactNumbers property. The easiest way to show these properties is to add some additional properties,   public Address NotNullableAddress { get { return Address ?? new Address(); } } public string Contacts { get { return string.Join("; ",ContactNumbers); } }               Now you can easily use these properties in WebGrid. Here is the complete code of this example,  @functions{ public class Employee { public Employee(){ ContactNumbers = new List<string>(); } public string Name { get; set; } public Address Address { get; set; } public List<string> ContactNumbers { get; set; } public Address NotNullableAddress { get { return Address ?? new Address(); } } public string Contacts { get { return string.Join("; ",ContactNumbers); } } } public class Address { public string City { get; set; } } } @{ var myClasses = new List<Employee>{ new Employee { Name="A" , Address = new Address{ City="AA" }, ContactNumbers = new List<string>{"021-216452","9231425651"}}, new Employee { Name="C" , Address = new Address{ City="CC" }}, new Employee { Name="D" , ContactNumbers = new List<string>{"045-14512125","21531212121"}} }; var grid = new WebGrid(source: myClasses); } @grid.GetHtml(columns: grid.Columns( grid.Column("NotNullableAddress.City", header: "City"), grid.Column("Name"), grid.Column("Contacts")))                    Summary:           You can use WebGrid helper to show tabular data in ASP.NET MVC, ASP.NET Web Forms and  ASP.NET Web Pages. Using this helper, you can also show complex types in the grid. In this article, I showed you how you use complex types with WebGrid helper. Hopefully you will enjoy this article too.  

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  • Type checking and recursive types (Writing the Y combinator in Haskell/Ocaml)

    - by beta
    When explaining the Y combinator in the context of Haskell, it's usually noted that the straight-forward implementation won't type-check in Haskell because of its recursive type. For example, from Rosettacode [1]: The obvious definition of the Y combinator in Haskell canot be used because it contains an infinite recursive type (a = a -> b). Defining a data type (Mu) allows this recursion to be broken. newtype Mu a = Roll { unroll :: Mu a -> a } fix :: (a -> a) -> a fix = \f -> (\x -> f (unroll x x)) $ Roll (\x -> f (unroll x x)) And indeed, the “obvious” definition does not type check: ?> let fix f g = (\x -> \a -> f (x x) a) (\x -> \a -> f (x x) a) g <interactive>:10:33: Occurs check: cannot construct the infinite type: t2 = t2 -> t0 -> t1 Expected type: t2 -> t0 -> t1 Actual type: (t2 -> t0 -> t1) -> t0 -> t1 In the first argument of `x', namely `x' In the first argument of `f', namely `(x x)' In the expression: f (x x) a <interactive>:10:57: Occurs check: cannot construct the infinite type: t2 = t2 -> t0 -> t1 In the first argument of `x', namely `x' In the first argument of `f', namely `(x x)' In the expression: f (x x) a (0.01 secs, 1033328 bytes) The same limitation exists in Ocaml: utop # let fix f g = (fun x a -> f (x x) a) (fun x a -> f (x x) a) g;; Error: This expression has type 'a -> 'b but an expression was expected of type 'a The type variable 'a occurs inside 'a -> 'b However, in Ocaml, one can allow recursive types by passing in the -rectypes switch: -rectypes Allow arbitrary recursive types during type-checking. By default, only recursive types where the recursion goes through an object type are supported. By using -rectypes, everything works: utop # let fix f g = (fun x a -> f (x x) a) (fun x a -> f (x x) a) g;; val fix : (('a -> 'b) -> 'a -> 'b) -> 'a -> 'b = <fun> utop # let fact_improver partial n = if n = 0 then 1 else n*partial (n-1);; val fact_improver : (int -> int) -> int -> int = <fun> utop # (fix fact_improver) 5;; - : int = 120 Being curious about type systems and type inference, this raises some questions I'm still not able to answer. First, how does the type checker come up with the type t2 = t2 -> t0 -> t1? Having come up with that type, I guess the problem is that the type (t2) refers to itself on the right side? Second, and perhaps most interesting, what is the reason for the Haskell/Ocaml type systems to disallow this? I guess there is a good reason since Ocaml also will not allow it by default even if it can deal with recursive types if given the -rectypes switch. If these are really big topics, I'd appreciate pointers to relevant literature. [1] http://rosettacode.org/wiki/Y_combinator#Haskell

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  • How do you make the script wait for the status of an Ajax get request before continuing?

    - by codeninja
    Basically what I'm doing is checking for the existence of an object, if it's not found, the script will try to load the source file using getScript. I only want to check this once though then return true or false to the function that calls fetch() fetch:function(obj){ ... isReady = false; $.getScript(obj.srcFile,function(){ isReady=true; warn("was able to load object "+key); }); return isReady; } but return kicks in before the script loads =/ later the script is loaded but the function returned false. This is the beauty of asynchronous I suppose... What's the best way to handle this... Maybe I could check again at some other point if the object exists? Or maybe there's a better way to do this where I dont have to potentially lock the browser?

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  • Dynamic Types and DynamicObject References in C#

    - by Rick Strahl
    I've been working a bit with C# custom dynamic types for several customers recently and I've seen some confusion in understanding how dynamic types are referenced. This discussion specifically centers around types that implement IDynamicMetaObjectProvider or subclass from DynamicObject as opposed to arbitrary type casts of standard .NET types. IDynamicMetaObjectProvider types  are treated special when they are cast to the dynamic type. Assume for a second that I've created my own implementation of a custom dynamic type called DynamicFoo which is about as simple of a dynamic class that I can think of:public class DynamicFoo : DynamicObject { Dictionary<string, object> properties = new Dictionary<string, object>(); public string Bar { get; set; } public DateTime Entered { get; set; } public override bool TryGetMember(GetMemberBinder binder, out object result) { result = null; if (!properties.ContainsKey(binder.Name)) return false; result = properties[binder.Name]; return true; } public override bool TrySetMember(SetMemberBinder binder, object value) { properties[binder.Name] = value; return true; } } This class has an internal dictionary member and I'm exposing this dictionary member through a dynamic by implementing DynamicObject. This implementation exposes the properties dictionary so the dictionary keys can be referenced like properties (foo.NewProperty = "Cool!"). I override TryGetMember() and TrySetMember() which are fired at runtime every time you access a 'property' on a dynamic instance of this DynamicFoo type. Strong Typing and Dynamic Casting I now can instantiate and use DynamicFoo in a couple of different ways: Strong TypingDynamicFoo fooExplicit = new DynamicFoo(); var fooVar = new DynamicFoo(); These two commands are essentially identical and use strong typing. The compiler generates identical code for both of them. The var statement is merely a compiler directive to infer the type of fooVar at compile time and so the type of fooExplicit is DynamicFoo, just like fooExplicit. This is very static - nothing dynamic about it - and it completely ignores the IDynamicMetaObjectProvider implementation of my class above as it's never used. Using either of these I can access the native properties:DynamicFoo fooExplicit = new DynamicFoo();// static typing assignmentsfooVar.Bar = "Barred!"; fooExplicit.Entered = DateTime.Now; // echo back static values Console.WriteLine(fooVar.Bar); Console.WriteLine(fooExplicit.Entered); but I have no access whatsoever to the properties dictionary. Basically this creates a strongly typed instance of the type with access only to the strongly typed interface. You get no dynamic behavior at all. The IDynamicMetaObjectProvider features don't kick in until you cast the type to dynamic. If I try to access a non-existing property on fooExplicit I get a compilation error that tells me that the property doesn't exist. Again, it's clearly and utterly non-dynamic. Dynamicdynamic fooDynamic = new DynamicFoo(); fooDynamic on the other hand is created as a dynamic type and it's a completely different beast. I can also create a dynamic by simply casting any type to dynamic like this:DynamicFoo fooExplicit = new DynamicFoo(); dynamic fooDynamic = fooExplicit; Note that dynamic typically doesn't require an explicit cast as the compiler automatically performs the cast so there's no need to use as dynamic. Dynamic functionality works at runtime and allows for the dynamic wrapper to look up and call members dynamically. A dynamic type will look for members to access or call in two places: Using the strongly typed members of the object Using theIDynamicMetaObjectProvider Interface methods to access members So rather than statically linking and calling a method or retrieving a property, the dynamic type looks up - at runtime  - where the value actually comes from. It's essentially late-binding which allows runtime determination what action to take when a member is accessed at runtime *if* the member you are accessing does not exist on the object. Class members are checked first before IDynamicMetaObjectProvider interface methods are kick in. All of the following works with the dynamic type:dynamic fooDynamic = new DynamicFoo(); // dynamic typing assignments fooDynamic.NewProperty = "Something new!"; fooDynamic.LastAccess = DateTime.Now; // dynamic assigning static properties fooDynamic.Bar = "dynamic barred"; fooDynamic.Entered = DateTime.Now; // echo back dynamic values Console.WriteLine(fooDynamic.NewProperty); Console.WriteLine(fooDynamic.LastAccess); Console.WriteLine(fooDynamic.Bar); Console.WriteLine(fooDynamic.Entered); The dynamic type can access the native class properties (Bar and Entered) and create and read new ones (NewProperty,LastAccess) all using a single type instance which is pretty cool. As you can see it's pretty easy to create an extensible type this way that can dynamically add members at runtime dynamically. The Alter Ego of IDynamicObject The key point here is that all three statements - explicit, var and dynamic - declare a new DynamicFoo(), but the dynamic declaration results in completely different behavior than the first two simply because the type has been cast to dynamic. Dynamic binding means that the type loses its typical strong typing, compile time features. You can see this easily in the Visual Studio code editor. As soon as you assign a value to a dynamic you lose Intellisense and you see which means there's no Intellisense and no compiler type checking on any members you apply to this instance. If you're new to the dynamic type it might seem really confusing that a single type can behave differently depending on how it is cast, but that's exactly what happens when you use a type that implements IDynamicMetaObjectProvider. Declare the type as its strong type name and you only get to access the native instance members of the type. Declare or cast it to dynamic and you get dynamic behavior which accesses native members plus it uses IDynamicMetaObjectProvider implementation to handle any missing member definitions by running custom code. You can easily cast objects back and forth between dynamic and the original type:dynamic fooDynamic = new DynamicFoo(); fooDynamic.NewProperty = "New Property Value"; DynamicFoo foo = fooDynamic; foo.Bar = "Barred"; Here the code starts out with a dynamic cast and a dynamic assignment. The code then casts back the value to the DynamicFoo. Notice that when casting from dynamic to DynamicFoo and back we typically do not have to specify the cast explicitly - the compiler can induce the type so I don't need to specify as dynamic or as DynamicFoo. Moral of the Story This easy interchange between dynamic and the underlying type is actually super useful, because it allows you to create extensible objects that can expose non-member data stores and expose them as an object interface. You can create an object that hosts a number of strongly typed properties and then cast the object to dynamic and add additional dynamic properties to the same type at runtime. You can easily switch back and forth between the strongly typed instance to access the well-known strongly typed properties and to dynamic for the dynamic properties added at runtime. Keep in mind that dynamic object access has quite a bit of overhead and is definitely slower than strongly typed binding, so if you're accessing the strongly typed parts of your objects you definitely want to use a strongly typed reference. Reserve dynamic for the dynamic members to optimize your code. The real beauty of dynamic is that with very little effort you can build expandable objects or objects that expose different data stores to an object interface. I'll have more on this in my next post when I create a customized and extensible Expando object based on DynamicObject.© Rick Strahl, West Wind Technologies, 2005-2012Posted in CSharp  .NET   Tweet !function(d,s,id){var js,fjs=d.getElementsByTagName(s)[0];if(!d.getElementById(id)){js=d.createElement(s);js.id=id;js.src="//platform.twitter.com/widgets.js";fjs.parentNode.insertBefore(js,fjs);}}(document,"script","twitter-wjs"); (function() { var po = document.createElement('script'); po.type = 'text/javascript'; po.async = true; po.src = 'https://apis.google.com/js/plusone.js'; var s = document.getElementsByTagName('script')[0]; s.parentNode.insertBefore(po, s); })();

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