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  • What is "sentry object" in C++?

    - by Romain Hippeau
    I answered this question, and Potatoswatter answered too as The modern C++ equivalent would be a sentry object: construct it at the beginning of a function, with its constructor implementing call(), and upon return (or abnormal exit), its destructor implements I am not familiar with using sentry objects in C++. I thought they were limited to input and output streams. Could somebody explain to me about C++ sentry objects as well as how to use them as an around interceptor for one or more methods in a class ? i.e. How to do this ? Sentry objects are very similar indeed. On the one hand they require explicit instantiation (and being passed this) but on the other hand you can add to them so that they check not only the invariants of the class but some pre/post conditions for the function at hand.

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  • Only Integrating Box2D collision detection in my 2d engine?

    - by Mr.Gando
    I have integrated box2d in my engine, ( Debug Draw, etc. ) and with a world I can throw in some 2d squares/rectangles etc. I saw this post, where the user is basically not using a world for collision detection, however the user doesn't explain anything about how he's using the manifold (b2Manifold), etc. Another post, is in the cocos2d forum, ( scroll down to the user Lam in the third reply ) Could anyone help me a bit with this?, basically want to add collision detection without the need of using b2World ,etc etc. Thanks a lot!

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  • Using slime's C-x C-e (Eval the form under the point) with swank-clojure in emacs

    - by hiheelhottie
    Hi, I'm using swank-clojure in emacs on OSX. I'm able to run a slime session. When I use C-x C-e on a simple form in a .clj file like (+ 7 7) I get an sldb buffer with Unable to resolve symbol: + in this context [Thrown class java.lang.Exception] I'm able to evaluate that form in the slime session directly. I was hoping the form in the clj file would get evaluated in the running slime session. Can someone explain how C-x C-e works in swank-clojure and how I can get the form to be evaluated in the running slime session? Thanks, hhh

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  • How to transfer binary data through multiple http server?

    - by solotim
    Well, the question is not intended to be that big. Let me explain the scenario: I have two http servers. server A is accessible to end user by web browser, while server B is internal server which can only be accessed by server A. If server B generate some big jpeg image in local disk, obviously we can't just delivery those path to image to server A and eventually to end user. Then, how to let end user see those image without firstly storing those image data in server A temporarily? I run PHP on server A and perl on server B, but this should not matter. I need a general pattern for implementing this.

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  • Type patterns and generic classes in Haskell

    - by finnsson
    I'm trying to understand type patterns and generic classes in Haskell but can't seem to get it. Could someone explain it in laymen's terms? In [1] I've read that "To apply functions generically to all data types, we view data types in a uniform manner: except for basic predefined types such as Float, IO, and ?, every Haskell data type can be viewed as a labeled sum of possibly labeled products." and then Unit, :*: and :+: are mentioned. Are all data types in Haskell automatically versions of the above mentioned and if so how do I figure out how a specific data type is represented in terms of :*:, etc? The users guide for generic classes (ch. 7.16) at haskell.org doesn't mention the predefined types but shouldn't they be handled in every function if the type patterns should be exhaustive? [1] Comparing Approaches to Generic Programming in Haskell, Ralf Hinze, Johan Jeuring, and Andres Löh

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  • System::IDisposable woes

    - by shadeMe
    public ref class ScriptEditor : public Form { public: typedef map<UInt32, ScriptEditor^> AlMap; static AlMap AllocationMap; Form^ EditorForm; RichTextBox^ EditorBox; StatusBar^ EditorStatusBar; StatusBarPanel^ StatusBarLineNo; void Destroy() { EditorForm->Close(); } ScriptEditor(unsigned int PosX, unsigned int PosY); }; The above code throws an Error C2039: '{dtor}' : is not a member of 'System::IDisposable'. I'm quite lost after having looked into articles that explain how the CLR manages memory. Any advice on getting rid of it would be appreciated. My first dabble in C+++/CLI isn't going too well.

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  • How to use a different assembly name for different configurations?

    - by Mark Ingram
    In Visual Studio 2008 (and others) when creating a .NET or silverlight application if you look at your project properties, it seems like you can only have one assembly name - across all configurations. I would like to compile my application as: MyAppDebug - in debug mode and just MyApp - in release mode Does anyone know if this is possible? Edit: It seems some people are questioning the reasoning behind the question, so I'll explain a little further: I'm working on a Silverlight application which gets automatically uploaded to our test site when I to a "build solution". The trouble is, the test team are now testing the online version, whilst I work on a new one. So, I want to have a url like .\MyApp.html for the regular version that the QA team will test and then .\MyApp.html?version=debug for the current version that I'm working on.

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  • Java: How do you access a sub-object of an object with no "getXXX" method to that sub-object

    - by Daxon
    I'll explain with pictures from Eclipse Debugger I have an Class called "FieldContext", (I can't edit it, it's compiled in the Java OVal API) Within "FieldContext" on the eclipse variable tab are "CompileTimeType" and "field" Q1 Is there a legend for the icons in the variables tab? like what the red box with the "F" means + yellow diamond boxes? Now I want to access the fields inside the "field" object (RedBox) .. preferably "name" But the "FieldContext" does not have a "getField()" method, yet it has a "getCompileTimeType()" method. Q2 So is there anyway to get that field object being a "SerializableField" Class from the "FieldContext"? If eclipse debugger can see/get/edit them then I hope I can do the same in Java.

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  • Declaring a function inside a function?

    - by nunos
    I have came across the following code, and being a c beginner, I came here for your help. This function is from a c implmentation of a queue. Bool queuePut(Queue *q, char c) { void beep(); if (queueFull(q)) { beep(); return false; } //do stuff return true; } So, I am getting a strange error with gcc on the void beep(). Can someone please explain me what is this, declaring a function inside a function. Or is it the void beep() simply out of place? I was given this code and there's always the possibility that it isn't correct. Thanks.

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  • What's the ROI of using a build tool like ant or nant?

    - by leeand00
    To me this sounds like a really stupid question. Why would you not use a build tool? However, I need to explain my co-worker why he should be using a build tool of some sort. He's getting really into the idea of working as a team with more programmers, but he isn't understanding the bigger picture of what needs to change in the build process in order to work with a larger team; (i.e. defensive programming/unit testing your code, having a bug database, programming modular libraries, and using sub-repositories to store modules in version control. This is a rather large stack of technologies that I need to prove the ROI of...so I figured I'd start with the ROI of using a build tool rather than just...say...clicking compile.

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  • [C#] Async threaded tcp server

    - by mark_dj
    I want to create a high performance server in C# which could take about ~10k clients. Now i started writing a TcpServer with C# and for each client-connection i open a new thread. I also use one thread to accept the connections. So far so good, works fine. The server has to deserialize AMF incoming objects do some logic ( like saving the position of a player ) and send some object back ( serializing objects ). I am not worried about the serializing/deserializing part atm. My main concern is that I will have a lot of threads with 10k clients and i've read somewhere that an OS can only hold like a few hunderd threads. Are there any sources/articles available on writing a decent async threaded server ? Are there other possibilties or will 10k threads work fine ? I've looked on google, but i couldn't find much info about design patterns or ways which explain it clearly

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  • flex custom events bubbling

    - by Rajeshbabu TRC
    Dear Richard Szalay, i go through your answers regarding bubbling, i want explore bubbling more. Please see my sample below <mx:Application xmlns:mx="http://www.adobe.com/2006/mxml" layout="absolute" xmlns:view="com.view.*" > } ]] In my custom event class i set bubbling=true, cancelable=true I can understand from previous answer that bubbling only affects UI components; events fired from custom classes will not bubble, even if the bubbles argument is set to true. My question is how can i prevent panelClickHandler function got fired when i click button in the "Load" (custom component)?? pleas explain bubbling with good example ( like to have with custom event classes)?

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  • What do you do when you feel you need a variatic list comprehension?

    - by cspyr0
    I would like to make a method where I could give it a list of lengths and it would return all combinations of cartesian coordinates up to those lengths. Easier to explain with an example: cart [2,5] Prelude> [ [0,0],[0,1],[0,2],[0,3],[0,4],[1,0],[1,1],[1,2],[1,3],[1,4] ] cart [2,2,2] Prelude> [ [0,0,0],[0,0,1],[0,1,0],[0,1,1],[1,0,0],[1,0,1],[1,1,0],[1,1,1] ] A simple list comprehension won't work because I don't know how long the lists are going to be. While I love Haskell's simplicity for many problems, this is one that I could write procedurally (in C or something) in 5 minutes whereas Haskell gives me an aneurysm! A solution to this specific problem would help me out a lot; I'd also love to hear about your thought processes when tackling stuff like this.

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  • Explanation of contribute_to_class

    - by anon.
    I'm attempted to extend code, and have come across an issue, I don't understand a line of code. I know the outcome of it - but I don't understand how it happens and am naturally enough scared to change it. The line of code I've come across is this: MyGenericRelation().contribute_to_class(model, 'field_name') The result of this code is a field with 'field_name' is added to the 'model' and from what I gather the objects inside the field are a list of type X (part of MyGenericRelation). I'm wondering if anyone can explain how this works. As in, why do I get a list of X objects attached to 'field_name' and if does it have to be generic relations prior to contribute_to_class or would using an actual model type, say 'Y' just give me a list of Y's. To be honest, I am more interested in the affect and functionality of the contribute_to_class method.

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  • DDD: Trying to code sorting and filtering as it pertains to Poco, Repository, DTO, and DAO using C#?

    - by Dr. Zim
    I get a list of items from my Repository. Now I need to sort and filter them, which I believe would be done in the Repository for efficiency. I think there would be two ways of doing this in a DDD way: Send a filter and a sort object full of conditions to the Repository (What is this called)? Repository result would produce an object with .filter and .sort methods? (This wouldn't be a POJO/POCO because it contains more than one object?). So is the answer 1, 2, or other? Could you explain why? I am leaning toward #1 because the Repository would be able to only send the data I want (or will #2 be able to delay accessing data like a LazyList?) A code example (or website link) would be very helpful. Example: Product product = repo.GetProducts(mySortObject, myFilterObject); // List of Poco product.AddFilter("price", "lessThan", "3.99"); product.AddSort("price", "descending");

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  • Python nested dict comprehension with sets

    - by Jasie
    Can someone explain how to do nested dict comprehensions? >> l = [set([1, 2, 3]), set([4, 5, 6])] >> j = dict((a, i) for a in s for i, s in enumerate(l)) >> NameError: name 's' is not defined I would have liked: >> j >> {1:0, 2:0, 3:0, 4: 1, 5: 1, 6: 1} I just asked a previous question about a simpler dict comprehension where the parentheses in the generator function were reduced. How come the s in the leftmost comprehension is not recognized?

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  • JavaScript - Textarea Selection

    - by brad
    The Problem I am working on an in-browser editor within a textarea. I have started looking for some information on dealing with textarea selection and found this jQuery plugin that does some simple manipulation. However, it doesn't explain what's going on. The Question Where can I find a good resource on Textarea Selection in JavaScript, preferably with a description of both pre-DOM3 and post-DOM30 scenarios? [Edit] In a great answer from Borgar, I have found several different places to start with contentEditable, selectionStart, and selectionEnd. I'll be looking into these things and posting any good tutorials I might find.

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  • JTable custom cell renderer to create row header

    - by hhj
    Can somebody please explain how I would create row headers? I already have the data and header texts set in the JTable: all I want to know is how I can use a cell renderer to take that first column (i.e. the row header column) and make it look like the column headers (i.e. the first row). Right now its background is white, so it looks like regular data. I want it to appear gray (or non-opaque I guess??). Oh and it should also not be selectable. Thanks.

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  • Does the order I declare pointers really matter in C? getcwd() problem...

    - by chucknelson
    On a Solaris 5.8 machine, I have the following code: [non-working code] char *buf; char *dir; size_t psize; psize = (size_t) 1024; dir = getcwd(buf, psize); On this unix machine, the above does not work and I get a segmentation fault when trying to run the program. It only works if I declare dir before buf: [working code] char *dir; char *buf; ... dir = getcwd(buf, psize); When using another flavor of Unix, such as Mac OS X, I don't get any of these what seem to be very strict rules on how to write the code. Can anyone explain what's going on with the above example? Thanks!

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  • Restoring web session in struts2

    - by bozo
    Hi, I have a classical scenario of a website and payment gateway integration, where the request for payment is sent to payment processor, and the payment processor calls back my application once it's done with some parameters I passed to it in the original request. Among parameters, we pass jsessionid and we expect that when the remote server makes request to our server (via customer browser redirect to our server) that the session will be the same as the session used to send the initial payment request. This does not happen, we have two different sessions, although the payment processor includes our original jsessionid in the request to us (https://blabla/?jsessionid=something). How should we go about recreating a session in struts2, in the only thing that connects the 'OLD' and 'NEW' session is the jsessionid in the request URL? Any ideas? Is this possible at all or is the 'OLD' session data deleted when the user moves away from our server onto a completely different domain of a payment processor with their data-entry form? This would explain our innability to recreate the session. Thanks a lot for your replies.

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  • How to download Google Cloud Messaging (GCM) from Google Code?

    - by Dennis
    I'm trying to learn how to use GCM and I want download the simple app. I'm following the instructions here: http://developer.android.com/google/gcm/server.html. Using App Engine for Java To set up the server using a standard App Engine for Java: Get the files from the open source site, as described above. I entered the link - https://code.google.com/p/gcm/ but there is no download there, and I don't have Git (and I don't know how to use it..). Can someone please explain how to download it or give me a link or something? Thank you in advance!

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  • Application loses authentication when performing redirect to a virtual directory

    - by nuhusky2003
    I have the following setup: http://www.example.com/dir1/ and http://www.example.com/dir2/ Each virtual directory is configured on IIS6.0 as an application with own AppPool. When redirecting authenticated user from dir1 to dir2 using response.redirect I lose authentication information for the user and the user is being redirected to the login page. This issue was not coming up with each app (dir1 and dir2) were configured under subdomain, ex: http://dir1.example.com and http://dir2.example.com. I have resolved the issue by adding a machine key to the machine.config file. Can someone explain to me why it's not working on a http://www.example.com/dir1 configuration?

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  • In Django, why is user.is_authenticated a method and not a member variable like is_staff

    - by luc
    Hello all, I've lost some time with a bug in my app due to user authentication. I think that it's a bit confusing but maybe someone can explain the reason and it will appear to me very logical. The user.is_staff is a member variable while user.is_authenticated is a method. However is_authenticated only returns True or False depending if the class is User or AnonymousUser (see http://docs.djangoproject.com/en/dev/topics/auth/) Is there a reason for that? Why user.is_authenticated is a method? Thanks in advance

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  • javascript constructor reset: What is it ?

    - by Sake
    I came across this slide: http://www.slideshare.net/stoyan/javascript-patterns#postComment at page 35: Option 5 + super + constructor reset function inherit(C, P) { var F = function(){}; F.prototype = P.prototype; C.prototype = new F(); C.uber = P.prototype; C.prototype.constructor = C; // WHY ??? } I don't get it. Can anybody please explain what the last line for ? C.prototype.constructor = C; // WHY ??? Thanks

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  • Error "E_UNEXPECTED(0x8000FFFF)" when using CDec/CInt/IsNumeric

    - by Marc vB
    I have encountered a strange problem, which I could solve but don't understand why it did occur. I have build a DLL with COM enabled. In this DLL I have classes that did use the functions CInt, CDec and IsNumeric. If I test these classes from a .NET application then it works ok. But when I called/run these classes from a Win32 application (with COM) then I did get an "E_UNEXPECTED(0x8000FFFF)" error. After some debugging I found out that the problem would go away if I: - replaced IsNumeric with Integer.TryParse or Decimal.TryParse - replaced CInt with Integer.Parse - replaced CDec with Decimal.Parse Can anyone explain this? Again, I could solve it by doing this but I would like to know why.

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