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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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  • 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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  • 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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  • A more concise example that illustrates that type inference can be very costly?

    - by mrrusof
    It was brought to my attention that the cost of type inference in a functional language like OCaml can be very high. The claim is that there is a sequence of expressions such that for each expression the length of the corresponding type is exponential on the length of the expression. I devised the sequence below. My question is: do you know of a sequence with more concise expressions that achieves the same types? # fun a -> a;; - : 'a -> 'a = <fun> # fun b a -> b a;; - : ('a -> 'b) -> 'a -> 'b = <fun> # fun c b a -> c b (b a);; - : (('a -> 'b) -> 'b -> 'c) -> ('a -> 'b) -> 'a -> 'c = <fun> # fun d c b a -> d c b (c b (b a));; - : ((('a -> 'b) -> 'b -> 'c) -> ('a -> 'b) -> 'c -> 'd) -> (('a -> 'b) -> 'b -> 'c) -> ('a -> 'b) -> 'a -> 'd = <fun> # fun e d c b a -> e d c b (d c b (c b (b a)));; - : (((('a -> 'b) -> 'b -> 'c) -> ('a -> 'b) -> 'c -> 'd) -> (('a -> 'b) -> 'b -> 'c) -> ('a -> 'b) -> 'd -> 'e) -> ((('a -> 'b) -> 'b -> 'c) -> ('a -> 'b) -> 'c -> 'd) -> (('a -> 'b) -> 'b -> 'c) -> ('a -> 'b) -> 'a -> 'e = <fun> # fun f e d c b a -> f e d c b (e d c b (d c b (c b (b a))));; - : ((((('a -> 'b) -> 'b -> 'c) -> ('a -> 'b) -> 'c -> 'd) -> (('a -> 'b) -> 'b -> 'c) -> ('a -> 'b) -> 'd -> 'e) -> ((('a -> 'b) -> 'b -> 'c) -> ('a -> 'b) -> 'c -> 'd) -> (('a -> 'b) -> 'b -> 'c) -> ('a -> 'b) -> 'e -> 'f) -> (((('a -> 'b) -> 'b -> 'c) -> ('a -> 'b) -> 'c -> 'd) -> (('a -> 'b) -> 'b -> 'c) -> ('a -> 'b) -> 'd -> 'e) -> ((('a -> 'b) -> 'b -> 'c) -> ('a -> 'b) -> 'c -> 'd) -> (('a -> 'b) -> 'b -> 'c) -> ('a -> 'b) -> 'a -> 'f = <fun>

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  • SQLAuthority News – Presenting at Tech-Ed On Road – Ahmedabad – June 11, 2011 – Wait Types and Queues

    - by pinaldave
    I will be presenting in person on the subject SQL Server Wait Types and Queues at Ahmedabad on June 11, 2011. Here is the quick summary of the session. SQL Server Waits and Queues – Your Gateway to Perf. Troubleshooting Time: 11:15am – 12:15pm – June 11, 2011 Just like a horoscope, SQL Server Waits and Queues can reveal your past, explain your present and predict your future. SQL Server Performance Tuning uses the Waits and Queues as a proven method to identify the best opportunities to improve performance. A glance at Wait Types can tell where there is a bottleneck. Learn how to identify bottlenecks and potential resolutions in this fast paced, advanced performance tuning session. This session is based on my performance tuning Wait Types and Queues series. SQL SERVER – Summary of Month – Wait Type – Day 28 of 28 During the session there will be Quiz and those who gets right answer will get very interesting gifts from me. Do not miss a single minute of the event. We are also going to have two rock star speakers – Harish Vaidyanathan and Jacob Sebastian. Here is the details for the event: SQLAuthority News – Community Tech Days – TechEd on The Road – Ahmedabad – June 11, 2011 Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: About Me, Pinal Dave, PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, SQLAuthority Author Visit, T SQL, Technology

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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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  • SQL SERVER – Summary of Month – Wait Type – Day 28 of 28

    - by pinaldave
    I am glad to announce that the month of Wait Types and Queues very successful. I am glad that it was very well received and there was great amount of participation from community. I am fortunate to have some of the excellent comments throughout the series. I want to dedicate this series to all the guest blogger – Jonathan, Jacob, Glenn, and Feodor for their kindness to take a participation in this series. Here is the complete list of the blog posts in this series. I enjoyed writing the series and I plan to continue writing similar series. Please offer your opinion. SQL SERVER – Introduction to Wait Stats and Wait Types – Wait Type – Day 1 of 28 SQL SERVER – Signal Wait Time Introduction with Simple Example – Wait Type – Day 2 of 28 SQL SERVER – DMV – sys.dm_os_wait_stats Explanation – Wait Type – Day 3 of 28 SQL SERVER – DMV – sys.dm_os_waiting_tasks and sys.dm_exec_requests – Wait Type – Day 4 of 28 SQL SERVER – Capturing Wait Types and Wait Stats Information at Interval – Wait Type – Day 5 of 28 SQL SERVER – CXPACKET – Parallelism – Usual Solution – Wait Type – Day 6 of 28 SQL SERVER – CXPACKET – Parallelism – Advanced Solution – Wait Type – Day 7 of 28 SQL SERVER – SOS_SCHEDULER_YIELD – Wait Type – Day 8 of 28 SQL SERVER – PAGEIOLATCH_DT, PAGEIOLATCH_EX, PAGEIOLATCH_KP, PAGEIOLATCH_SH, PAGEIOLATCH_UP – Wait Type – Day 9 of 28 SQL SERVER – IO_COMPLETION – Wait Type – Day 10 of 28 SQL SERVER – ASYNC_IO_COMPLETION – Wait Type – Day 11 of 28 SQL SERVER – PAGELATCH_DT, PAGELATCH_EX, PAGELATCH_KP, PAGELATCH_SH, PAGELATCH_UP – Wait Type – Day 12 of 28 SQL SERVER – FT_IFTS_SCHEDULER_IDLE_WAIT – Full Text – Wait Type – Day 13 of 28 SQL SERVER – BACKUPIO, BACKUPBUFFER – Wait Type – Day 14 of 28 SQL SERVER – LCK_M_XXX – Wait Type – Day 15 of 28 SQL SERVER – Guest Post – Jonathan Kehayias – Wait Type – Day 16 of 28 SQL SERVER – WRITELOG – Wait Type – Day 17 of 28 SQL SERVER – LOGBUFFER – Wait Type – Day 18 of 28 SQL SERVER – PREEMPTIVE and Non-PREEMPTIVE – Wait Type – Day 19 of 28 SQL SERVER – MSQL_XP – Wait Type – Day 20 of 28 SQL SERVER – Guest Posts – Feodor Georgiev – The Context of Our Database Environment – Going Beyond the Internal SQL Server Waits – Wait Type – Day 21 of 28 SQL SERVER – Guest Post – Jacob Sebastian – Filestream – Wait Types – Wait Queues – Day 22 of 28 SQL SERVER – OLEDB – Link Server – Wait Type – Day 23 of 28 SQL SERVER – 2000 – DBCC SQLPERF(waitstats) – Wait Type – Day 24 of 28 SQL SERVER – 2011 – Wait Type – Day 25 of 28 SQL SERVER – Guest Post – Glenn Berry – Wait Type – Day 26 of 28 SQL SERVER – Best Reference – Wait Type – Day 27 of 28 SQL SERVER – Summary of Month – Wait Type – Day 28 of 28 Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: Pinal Dave, PostADay, SQL, SQL Authority, SQL Optimization, SQL Query, SQL Scripts, SQL Server, SQL Tips and Tricks, SQL Wait Stats, SQL Wait Types, SQLServer, T SQL, Technology

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  • SQL SERVER – Best Reference – Wait Type – Day 27 of 28

    - by pinaldave
    I have great learning experience to write my article series on Extended Event. This was truly learning experience where I have learned way more than I would have learned otherwise. Besides my blog series there was excellent quality reference available on internet which one can use to learn this subject further. Here is the list of resources (in no particular order): sys.dm_os_wait_stats (Book OnLine) – This is excellent beginning point and official documentations on the wait types description. SQL Server Best Practices Article by Tom Davidson – I think this document goes without saying the BEST reference available on this subject. Performance Tuning with Wait Statistics by Joe Sack – One of the best slide deck available on this subject. It covers many real world scenarios. Wait statistics, or please tell me where it hurts by Paul Randal – Notes from real world from SQL Server Skilled Master Paul Randal. The SQL Server Wait Type Repository… by Bob Ward – A thorough article on wait types and its resolution. A MUST read. Tracking Session and Statement Level Waits by by Jonathan Kehayias – A unique article on the subject where wait stats and extended events are together. Wait Stats Introductory References By Jimmy May – Excellent collection of the reference links. Great Resource On SQL Server Wait Types by Glenn Berry – A perfect DMV to find top wait stats. Performance Blog by Idera – In depth article on top of the wait statistics in community. I have listed all the reference I have found in no particular order. If I have missed any good reference, please leave a comment and I will add the reference in the list. Read all the post in the Wait Types and Queue series. Reference: Pinal Dave (http://blog.SQLAuthority.com) Tracking Session and Statement Level Waits Filed under: Pinal Dave, PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, SQL Wait Stats, SQL Wait Types, T SQL, Technology

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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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  • 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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  • "Meld requires pygtk 2.8.0 or higher."

    - by Lynx
    I got this error after installing Meld on a new Karmic installation: ~$ meld No module named pygtk Meld requires pygtk 2.8.0 or higher. I installed the latest version of python-gtk with aptitude but I'm not sure what version is actually installed. My python version is 2.6. This is weird because I have another machine that runs Karmic and Meld without a problem. Any ideas?

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  • How to add higher video resolution in Ubuntu 10.4 (UNR on EEE1101HA)

    - by lexu
    I picked up an ASUS EEE 1101HA with Windows 7 and installed UBUNTU 10.4 Netbook Remix (dual boot). Ubuntu runs fine, but it doesn't recognize that the notebook LCD is 1388x768 and thus only offers 1024x768 and 800x600 as monitor resolution. So .. how can I tell it about that higher resolution? (Have root pwd & vi, una-bash-ed to use both.. )

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  • How to get higher download rate than upload rate

    - by user23950
    i'm using bandwidthplace.com to measure my internet speed. And here it is: Download Speed: 422 kbps (52.8 KB/sec transfer rate) Upload Speed: 202 kbps (25.3 KB/sec transfer rate) Can you please explain to me how did they get the 52.8 transfer rate. And how do I get to lower the upload speed in order for me to get higher download speed.

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  • Network speeds being report as 4x higher than actual in Windows 7 SP1

    - by Synetech
    Ever since installing Windows 7 SP1, I have noticed that all programs that display my network transfer rate have been exactly 4x higher than they actually are. For example, when I download something from a high-bandwidth web site or through torrents with lots of sources, the download rate indicated is is ~5MBps (~40Mbps) even though my Internet connection has a maximum of only 1.5MBps (12Mbps). It is the same situation with the upstream bandwidth: the connection maximum is 64KBps, but I’m seeing up to 256KBps. I have tried several different programs for monitoring bandwidth throughput and they all give the same results. I also tried different times and different days, and they always show the rate as being four times too high. My initial thought was that my ISP had increased the speeds (without my noticing), which they have done before. However, I checked my ISP’s site and they have not increased the speeds. Moreover, when I look at the speeds in the program actually doing the transfer (eg Chrome, µTorrent, etc.), the numbers are in line with the expected values at the same time that bandwidth monitoring programs are showing the high numbers. The only significant change (and pretty much the only change at all) that has occurred to my system since the change was the installation of SP1 for Windows 7. As such, it is my belief that some sort of change exists in SP1 whereby software that accesses the bandwidth via a specific API receives (erroneously?) high numbers while others that have access to the raw data continue to receive the correct values. I booted into Windows XP and downloaded some things via HTTP and torrent and in both cases, the numbers were as expected (like they were in Windows 7 before installing SP1). I then booted back into 7SP1 and once again, the numbers were four times higher than possible. Therefore it is definitely something in SP1 that has changed how local bandwidth is calculated/returned. There is definitely something wonky with Windows 7 SP1’s network speed calculation. I tried Googling this, but (for multiple reasons), have had a difficult time finding anything relevant. Has anybody else noticed this behavior? Does anybody know of any bugs or changes in SP1 that could account for it?

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  • How to handle value types when embedding IronPython in C#?

    - by kloffy
    There is a well known issue when it comes to using .NET value types in IronPython. This has recently caused me a headache when trying to use Python as an embedded scripting language in C#. The problem can be summed up as follows: Given a C# struct such as: struct Vector { public float x; public float y; } And a C# class such as: class Object { public Vector position; } The following will happen in IronPython: obj = Object() print obj.position.x # prints ‘0’ obj.position.x = 1 print obj.position.x # still prints ‘0’ As the article states, this means that value types are mostly immutable. However, this is a problem as I was planning on using a vector library that is implemented as seen above. Are there any workarounds for working with existing libraries that rely on value types? Modifying the library would be the very last resort, but I'd rather avoid that.

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  • What's special about currying or partial application?

    - by Vigneshwaran
    I've been reading articles on Functional programming everyday and been trying to apply some practices as much as possible. But I don't understand what is unique in currying or partial application. Take this Groovy code as an example: def mul = { a, b -> a * b } def tripler1 = mul.curry(3) def tripler2 = { mul(3, it) } I do not understand what is the difference between tripler1 and tripler2. Aren't they both the same? The 'currying' is supported in pure or partial functional languages like Groovy, Scala, Haskell etc. But I can do the same thing (left-curry, right-curry, n-curry or partial application) by simply creating another named or anonymous function or closure that will forward the parameters to the original function (like tripler2) in most languages (even C.) Am I missing something here? There are places where I can use currying and partial application in my Grails application but I am hesitating to do so because I'm asking myself "How's that different?" Please enlighten me.

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