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• Specialization of template method - what's wrong with my code?

  - by Vincenzo

  What's wrong with this code? class School { public: template<typename T> size_t count() const; private: vector<Boy*> boys; vector<Girl*> girls; } template<> size_t School::count<Boy>() const { return boys.size(); } My compile says that "specialization of .. after initialization". Could you please help?

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• Is this class + constructor definition pattern overly redundant?

  - by Protector one

  I often come across a pattern similar to this: class Person { public string firstName, lastName; public Person(string firstName, string lastName) { this.firstName = firstName; this.lastName = lastName; } } This feels overly redundant (I imagine typing "firstName" once, instead of thrice could be enough…), but I can't think of a proper alternative. Any ideas? Maybe I just don't know about a certain design pattern I should be using here? Edit - I think I need to elaborate a little. I'm not asking how to make the example code "better", but rather, "shorter". In its current state, all member names appear 3 times (declaration, initialization, constructor arguments), and it feels rather redundant. So I'm wondering if there is a pattern (or semantic sugar) to get (roughly) the same behavior, but with less bloat. I apologize for being unclear initially.

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• initializer_list in the VC10

  - by user335870

  hi i wrote this program in VC++ 2010: class class1 { public: class1 (initializer_list<int> a){}; int foo; float Bar; }; void main() { class1 c = {2,3}; getchar(); } but i get this errors when i compile project: Error 1 error C2552: 'c' : non-aggregates cannot be initialized with initializer list c:\users\pswin\documents\visual studio 2010\projects\test_c++0x\test_c++0x\main.cpp 27 and 2 IntelliSense: initialization with '{...}' is not allowed for object of type "class1" c:\users\pswin\documents\visual studio 2010\projects\test_c++0x\test_c++0x\main.cpp 27 what is the problem?

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• Cannot initialize non-const reference from convertible type

  - by Julien L.

  Hi, I cannot initialize a non-const reference to type T1 from a convertible type T2. However, I can with a const reference. long l; const long long &const_ref = l; // fine long long &ref = l; // error: invalid initialization of reference of // type 'long long int&' from expression of type // 'long int' Most problems I encountered were related to r-values that cannot be assigned to a non-const reference. This is not the case here -- can someone explain? Thanks.

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• [OpenCV] cvFilter2D works very very slow in Ubuntu 9.10 amd64?

  - by Hong

  Hi, has someone tried the cvFilter2D under 64bit linux? Recently when I was trying to port some code to the amd64 version of Ubuntu 9.10, I just found that the cvFilter2D works really slow. The version is Opencv 2.0. The code is as follows: CvMat *mat_src = cvCreateMat(128, 128, CV_32FC1); CvMat *mat_dest = cvCreateMat(128, 128, CV_32FC1); CvMat* mat_kernel = cvCreateMat( 25, 25, CV_32FC1); // initialization ... cvFilter2D( (CvMat*)mat_src, (CvMat*)mat_dest, (CvMat*)mat_kernel, cvPoint( (25-1)/2, (25-1)/2)); // I needs approximately 100ms to finish that... My CPU is Intel 2.4G However, the Opencv 1.1pre only cost me 3ms for the same code...

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• Traversable => Java Iterator

  - by Andres

  I have a Traversable, and I want to make it into a Java Iterator. My problem is that I want everything to be lazily done. If I do .toIterator on the traversable, it eagerly produces the result, copies it into a List, and returns an iterator over the List. I'm sure I'm missing something simple here... Here is a small test case that shows what I mean: class Test extends Traversable[String] { def foreach[U](f : (String) => U) { f("1") f("2") f("3") throw new RuntimeException("Not lazy!") } } val a = new Test val iter = a.toIterator

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• CoreData could not fulfill a fault when adding new attribute

  - by cagreen

  I am receiving a "CoreData could not fulfill a fault for ..." error message when trying to access a new attribute in a new data model. If I work with new data I'm ok, but when I attempt to read existing data I get the error. Do I need to handle the entity differently myself if the attribute isn't in my original data? I was under the impression that Core Data could handle this for me. My new attribute is marked as optional with a default value. I have created a new .xcdatamodel (and set it to be the current version) and updated my NSPersistentStoreCoordinator initialization to take advantage of the lightweight migration as follows: NSDictionary *options = [NSDictionary dictionaryWithObjectsAndKeys: [NSNumber numberWithBool:YES], NSMigratePersistentStoresAutomaticallyOption, [NSNumber numberWithBool:YES], NSInferMappingModelAutomaticallyOption, nil]; NSError *error = nil; persistentStoreCoordinator = [[NSPersistentStoreCoordinator alloc] initWithManagedObjectModel:[self managedObjectModel]]; if (![persistentStoreCoordinator addPersistentStoreWithType:NSSQLiteStoreType configuration:nil URL:storeUrl options:options error:&error]) { NSLog(@"Unresolved error %@, %@", error, [error userInfo]); abort(); } Any help is appreciated.

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• How to customise the TextView inside a Spinner?

  - by Janusz

  I have a Spinner with an ArrayAdapter that feeds Values into it. The Problem is that the text is to long for the view and the result is a very very ugly spinner. As can be seen in the screenshot: I tried to pass the Id of my own TextView into the Adapter but everytime the spinner should be shown I get an Exception that the Id I supplied is not valid: 04-26 17:38:39.695: ERROR/AndroidRuntime(4276): android.content.res.Resources$NotFoundException: Resource ID #0x7f09003a type #0x12 is not valid Where do I have to define the TextView? In a separate xml file? With a surrounding viewgroup? It would help me a lot if I could see an example of the adapter initialization and the textview definition?

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• When is it appropriate to use C++ exceptions?

  - by krebstar

  I'm trying to design a class that needs to dynamically allocate some memory.. I had planned to allocate the memory it needs during construction, but how do I handle failed memory allocations? Should I throw an exception? I read somewhere that exceptions should only be used for "exceptional" cases, and running out of memory doesn't seem like an exceptional case to me.. Should I allocate memory in a separate initialization routine instead and check for failures and then destroy the class instance gracefully? Or should I use exceptions instead? The class won't have anything useful to do if these memory allocations should fail.. EDIT: The consensus seems to be that running out of memory IS an exceptional case. Will see how to go about this.. Thanks.. :)

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• Contents after &amp; cannot be retrieved by xml parsing in iphone?

  - by Warrior

  I am new to iphone development.I am parsing a You tube rss feed to display its content in the table view. While retrieving the content of link tag, i am able to retrieve only half of the url and the string after & cannot be retrieved. I want to retrieve the full url so that i can use the url to load in a webview. How can i retrieve the full url ? Please help me out.The parsing is done same as Lazy tables . The orginal url is "http:www.youtube.xxxxxxxx&amp;xxxxxgdata"; The retrieved Url is "http:www.youtube.xxxxxxxx" Thanks.

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• Can we you the attached properties in C# class library?

  - by Manas Agarwal

  Hi I have implemented the Observer Pattern with lazy load. The class that requests the data from the database is a singleton class. Now I am able to load the data from one database (located in one datacenter) very easily. But I need to get the data from other data centers too and display on the same UI. I can somehow pass the address of second data center and fetch the data from there also. But once I will get the data from second data center, it will be added to earlier list only. So later it will be thought for me to distinguish between the data. So I thought of attaching a property with the result set, so that while displaying the output I can show the data for both the data centers separately but on the same UI. I thought of attached property as an option where I can attach the data center name with the list of the data obtained. How is it possible to do in C#? Thanks Manas

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• Backbone collection's URL depends on initialize function

  - by egidra

  I have a Backbone collection whose URL depends on the initialize function. When I create an instance of this Backbone collection, I pass in an ID to filter which instances of the model appear. Here is what the collection's code looks like: var GoalUpdateList = Backbone.Collection.extend({ // Reference the Goal Update model model: GoalUpdate, // Do HTTP requests on this endpoint url: "http://localhost:8000/api/v1/goal_update/?goal__id=" + this.goal_id + "&format=json", // Set the goal ID that the goal update list corresponds to initialize: function(goal_id) { this.goal_id = goal_id; console.log(this.goal_id); console.log(this.url); }, }); Of course, this doesn't work. this.goal_id is seen as being undefined. I guess because the URL is set before the initialization function is run.

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• Not loading the object caused EF4 (code first) to remove the relationship

  - by Lavinski

  Firstly this is a EF4: Code First - Property Loading question. I'm loading an object like so var item = Context.Table.Find( update.Identifier ); This object has a property Relationship so a table has a Relationship object. Now i'm updating my item but my Relationship object is not toched (and therefore not lazy loaded). Now here's the problem .. I save my item and my relationship to the Relationship object is deleted, apparently the model thinks i set it to null. However it all works if I look at the property before saving. So I'm looking into LoadProperty or doing a query and using Include. Has anyone else come across this issue and how did you get around it?

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• Desktop PC Raid 5 or JBOD?

  - by Sean Lim

  I have a desktop PC and I want to get alot of space for movies, music, and pictures. I probably will not be deleting files. I am running Windows 7 on my system. It is kind of silly I just want the physical drives to be labeled as a single letter drive. And probably map my video, documents, pictures and music on that single drive. The main reason I considered RAID 5 because I would be lazy to get the data I lost and hopefully that if I get a new drive, it would rebuild it. So my question is which would be better? A second question is can I get RAID card that has only 2 internal connectors and still do RAID 5? or do I have to get a RAID card that has 4 internal connectors.

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• What is XcvPort (used in OpenPrinter function)

  - by RiskX

  I'm usin the OpenPrinter function and the first parameter the function gets called "pPrinterName" and that's it's MSDN description: [in] Pointer to a null-terminated string that specifies the name of the printer or print server, the printer object, the XcvMonitor, or the XcvPort. For a printer object use: PrinterName,Job xxxx. For an XcvMonitor, use: ServerName,XcvMonitor MonitorName. For an XcvPort, use: ServerName,XcvPort PortName. Obviously I'm interested in the bold part. What exactly is XcvPort? I know it seems like a question of lazy person but I really couldn't find info abou this concept. If I would like to open a printer on port ABC I should write: "\\MySrever,XcvPort ABC"? Thank you for your answers!

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• Can getAttribute() method of Tomcat ServletContext implementation be called without synchronization?

  - by oo_olo_oo

  I would like to read some parameters during servlet initializtion (in init() method), and store them among servlet context attributes (using getServletContext().setAttribute()). I would like to read these parameters later - during some request processing (using getServletContext().getAttribute()). So, the multiple threads could do this simultaneously. My question is if such an attempt is safe? Could I be sure that multi threaded calls to the getAttribute() don't mess up any internal state of the servlet context? Please take into account that I'm not going to call the setAttribute() anywhere besides the initialization. So, only calls to the getAttribute() are going to be done from multiple threads. But depending on the internal implementation, this also could be dangerous. So, any information about Tomcat's implementation would be appreciated.

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• iPhone - Create non-persistent entities in core data

  - by ncohen

  Hi everyone, I would like to use entity objects but not store them... I read that I could create them like this: myElement = (Element *)[NSEntityDescription insertNewObjectForEntityForName:@"Element" inManagedObjectContext:managedObjectContext]; And right after that remove them: [managedObjectContext deleteObject:myElement]; then I can use my elements: myElement.property1 = @"Hello"; This works pretty well even though I think this is probably not the most optimal way to do it... Then I try to use it in my UITableView... the problem is that the object get released after the initialization. My table becomes empty when I move it! Thanks edit: I've also tried to copy the element ([myElement copy]) but I get an error...

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• Cannot use String.Empty as a default value for an optional parameter in C# - then what's the point?

  - by Mikeyg36

  I am reading Effective C# by Bill Wagner. In Item 14 - Minimize Duplicate Initialization Logic, he shows the following example of using the new optional parameters feature in a constructor: public MyClass(int initialCount = 0, string name = "") Notice that he used "" instead of string.Empty. He comments: You'll note [in an example above] that the second constructor specified "" for the default value on the name parameter, rather than the more customary string.Empty. That's because string.Empty is not a compile-time constant. It is a static property defined in the string class. Because it is not a compile constant, you cannot use it for the default value for a parameter. If we cannot use the string.Empty static in all situations, then doesn't that defeat the purpose of it? I thought that we would use it to be sure that we have a system-independent means of referring to the empty string. Is my understanding wrong? Thanks.

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• Extracting startup errors from Spring contexts

  - by sehugg

  Consider the following output from a Tomcat server under Eclipse: INFO: Initializing Coyote HTTP/1.1 on http-8080 INFO: Initialization processed in 634 ms INFO: Starting service Catalina INFO: Starting Servlet Engine: Apache Tomcat/6.0.20 SEVERE: Error listenerStart SEVERE: Context [/MyServlet] startup failed due to previous errors I would like to figure out what exception caused "Error listenerStart", but Spring seems to be preventing me from finding the error via Eclipse. I'd love to start Catalina manually, but that doesn't seem to do anything. What's the best way to find the hidden exception? I'm not afraid to use torture methods.

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• Java DAO caching

  - by santiagobasulto

  I'm developing a medium Java app, and i'm facing a small problem due to my lack of experience. I've a custom DAO, which gets "Article" objects from the Database. I've the Article class, and the DAO has a method called getArticle(int id), this method returns an Article. The Article has a Category object, and I'm using lazy loading. So, when I request for an article's category (Article a = new Article(); a.getCategory();) the Article class gets the Category from the DAO and then returns it. I'm now thinking to cache it, so when I request multiple times to an article's category, the database is only queried one time. My question is: where should I put that cache? I can put it on the Article class (in the DTO), or I can put it on the DAO class. What do you say?

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• Is there a quick way to build & install to iPhone (from XCode) without starting the app?

  - by Olie

  In XCode, I can use CMD-R to run (or CMD-Y to debug), and my app will compile, install on the phone & start-up. (I've already prepped my phone & XCode so this part works as expected.) What I'd LIKE to do is type CMD-<something else> and have my program compile & install on the phone, but NOT start-up. I realize that I can just CMD-B to build, then go through some rigamarole to deploy, but I'm hoping one of you smart-folk can tell me the lazy-man's shortcut for all of this. Thanks!

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• NHibernate, each property is filled with a different select statement

  - by Eitan

  I'm retrieving a list of nhibernate entites which have relationships to other tables/entities. I've noticed instead of NHibernate performing JOINS and populating the properties, it retrieves the entity and then calls a select for each property. For example if a user can have many roles and I retrieve a user from the DB, Nhibernate retrieves the user and then populates the roles with another select statement. The problem is that I want to retrieve oh let's say a list of products which have various many-to-many relationships and relationships to items which have their own relationships. In the end I'm left with over a thousand DB calls to retrieve a list of 30 products. Thanks. I've also set default lazy loading to false because whenever I save the list of entities to a session, I get an error when trying to retrieve it on another page: LazyInitializationException: could not initialize proxy If anybody could shed any light I would truly appreciate it. Thanks. Eitan

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• What's the proper way to use sqlite at xCode?

  - by Elliot Chen

  Hi, Experts: Can you please give some suggestions on sqlite using at xcode? Within my application, I use a sqlite DB to store all local data. Two methods can be used to retrieve those data during running time. 1, Load all the data into memory at initialization stage. (More memory used, less DB open/close operation needed) 2, Read corresponding records when necessary, free the occupied memory after using. (Good habit for memory using, but much DB open/close operations needs). I prefer to use method 2, but not sure whether too many DB opening/closing operations could affect app's efficiency. Or do you think I can 'upgrade' method 2 by opening DB when app launches and closing DB when app quits? Thanks for your suggestions very much!

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• Howto check if a object is connected to another in hibernate

  - by codevourer

  Imagine two domain object classes, A and B. A has a bidirectional one-to-many relationship to B. A is related to thousands of B. The relations must be unique, it's not possible to have a duplicate. To check if an instance of B is already connected to a given instance of A, we could perform an easy INNER JOIN but this will only ensure the already persisted relations. What about the current transient relations? class A { @OneToMany private List<B> listOfB; } If we access the listOfB and perform a check of contains() this will fetch all the connected instances of B lazy from the datasource. I only want to validate them by their primary-key. Is there an easy solution where I can do things like "Does this instance of A is connected with this instance of B?" Without loading all these data into memory and perform a based on collections?

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• emacs/Python: running python-shell in line buffered vs. block buffered mode

  - by Begbie00

  Hi all - In a related question and answer here, someone hypothesized that python-shell within emacs(23.2) was block-buffered instead of line-buffered. The recommended fix was to add sys.stdout.flush() to the spot in my script where I want stdio to flush its contents to the python-shell. Is there someway to trick python-shell (running in emacs 23.2 on Windows, not Linux) into either a) thinking it's attached to a TTY or b) using line-buffered instead of block-buffered mode? I don't see why I'd be able to do this in IDLE but not emacs. I'd rather customize emacs than add sys.stdout.flush() throughout my scripts. Call me lazy :-). Thanks, Mike

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