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• Convert String value format of YYYYMMDDHHMMSS to C# DateTime

  - by SARAVAN

  I have a need to convert a string value in the form "YYYYMMDDHHMMSS" to a DateTime. But not sure on how, may be a DateTime.Tryparse can be used to make this happen. Or is there any other way to do it. I can do this using some string operations to take "YYYYMMDD" alone, convert to a datetime and then add HH, MM, SS separately to that DateTime. But is there any DateTime.TryParse() methods that I can use in one line to convert a "YYYYMMDDHHMMSS" format string value to a DateTime value?

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• Measuring the performance of classification algorithm

  - by Silver Dragon

  I've got a classification problem in my hand, which I'd like to address with a machine learning algorithm ( Bayes, or Markovian probably, the question is independent on the classifier to be used). Given a number of training instances, I'm looking for a way to measure the performance of an implemented classificator, with taking data overfitting problem into account. That is: given N[1..100] training samples, if I run the training algorithm on every one of the samples, and use this very same samples to measure fitness, it might stuck into a data overfitting problem -the classifier will know the exact answers for the training instances, without having much predictive power, rendering the fitness results useless. An obvious solution would be seperating the hand-tagged samples into training, and test samples; and I'd like to learn about methods selecting the statistically significant samples for training. White papers, book pointers, and PDFs much appreciated!

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• Add a listener inside or outside get method

  - by James P.

  I'm learning Swing and have composed an interface using a series of get methods to add components. Is it a good practise to add a Listener inside a get method as follows? I'd like to make things as decoupled as possible. private JButton getConnectButton() { if (connectButton == null) { connectButton = new JButton(); connectButton.setText("Connect"); connectButton.setSize(new Dimension(81, 16)); connectButton.setLocation(new Point(410, 5)); connectButton.addActionListener(new ActionListener() { public void actionPerformed(ActionEvent e) { // actionPerformed code goes here } }); } return connectButton; }

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• Resetting Objects vs. Constructing New Objects

  - by byronh

  Is it considered better practice and/or more efficient to create a 'reset' function for a particular object that clears/defaults all the necessary member variables to allow for further operations, or to simply construct a new object from outside? I've seen both methods employed a lot, but I can't decide which one is better. Of course, for classes that represent database connections, you'd have to use a reset method rather than constructing a new one resulting in needless connecting/disconnecting, but I'm talking more in terms of abstraction classes. Can anyone give me some real-world examples of when to use each method? In my particular case I'm thinking mostly in terms of ORM or the Model in MVC. For example, if I would want to retrieve a bunch of database objects for display and modify them in one operation.

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• C++ visitor pattern handling templated string types?

  - by Steve the Plant

  I'm trying to use the visitor pattern to serialize the contents of objects. However one snag I'm hitting is when I'm visiting strings. My strings are of a templated type, similar to STL's basic_string. So something like: basic_string<char_type, memory_allocator, other_possible_stuff> \\ many variations possible! Since I can have very many different templated string types, I can't go and add them to my visitor interface. It would be ridiculous. But I can't add templates to my VisitString method because C++ prevents using templates parameters in virtual methods. So what are my options to work around this?

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• Limiting method access in protected section to few classes

  - by Bharat

  Hi, I want to limit the access of protected methods to certain inherited classes only. For example there is a base class like TBase = Class Protected Method1; Method2; Method3; Method4; End; I have two classes derived from TBase TDerived1 = Class(TBase) //Here i must access only Method1 and Method2 End; TDerived2 = Class(TBase) //Here i must access only Method3 and Method4 End; Then is it possible to access only Method1 and Method2 when i use objects of TDerived1 and Method3 and Method4 when i use objects of TDerived2

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• Read binary data from a MDB-file running under LAMP

  - by BusterX

  I need to be able to connect to an MDB-file in a LAMP-environment (running on Linux) and ultimately insert converted data into a Mysql db. The data I need to access is stored as a BLOB (Long Binary Data according to Access) in the MDB file. I have not yet been able to actually have a look at the data but I have been told that the BLOB consists of byte strings. Something along the lines of: 0x1c 0x10 0x27 0x00 0x00 I need to parse the byte strings and convert these to a format that is human readable. I do have access to the documentation that explains the various byte strings. So this is really two questions: How do a get access to the MDB file via PHP* (running under LAMP) and read the BLOB (I do not have access to a Windows-platform)? What would be the best way to parse the binary data (in PHP*) once I am able to connect to the MDB-file? *Or are there other methods/languages that are more appropriate?

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• Objective-c class initializer executes multiple times

  - by apisip

  Unless I misunderstood it, this LINK from Apple's documentation clearly states that the class initializer, "+ (void)initialize)", only executes once per class. Here is the excerpt: Special Considerations initialize it is invoked only once per class. If you want to perform independent initialization for the class and for categories of the class, you should implement load methods. However, I'm getting a weird behavior on my project and the initializer is being executed twice. So I have to check if _classContext is null. I only got one class that has this method. What are the possible reasons why this is happening? I'm using XCode 4.5.2 and OS X 10.8.2. I got multiple iOS simulators, iPhone 5.1 and 6.0. + (void) initialize { num++; NSLog([NSString stringWithFormat:@"Times: %i", num]); if(_classContext == nil) _classContext = [[myClass alloc] init]; }

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• Custom CallOut not displayed correctly in ios6?

  - by balu

  As i want to implement the custom call out in the mkmapview i am using these classes CalloutMapAnnotationView.h and CalloutMapAnnotationView.m I have extracted these classes from the following links https://github.com/asalom/Custom-Map-Annotation-Callouts/blob/master/Classes/CalloutMapAnnotationView.h https://github.com/asalom/Custom-Map-Annotation-Callouts/blob/master/Classes/CalloutMapAnnotationView.m These work fine in ios5 but in ios6 when i am clicking on the call out the map view is moving and call out is not showing correctly as shown in the below figures while i was zooming also its not coming correctly i have tried several ways to get rid out of this problem by checking the version of os and tried to change the some of the methods in the classes but of not use. After implementing these in ios5 map view coming like this In Ios6 This one not coming properly as like in ios5. for example

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• Why make anything internal?

  - by c-charp N00b

  I don't really see the point of making methods or classes internal. In my very limited understanding, all it does is make working with your code very difficult for other programmers. Say I write Big_Important_Class for Project A and make said class internal. Then Bob, working on Project B needs to use my class to have project B work with Project A, but since its internal he can't. As of now this is the only thing I have seen internals do, make things really complicated for the guy working on Project B. I know there has to be a good reason to use internals, but I don't see any. Could someone please explain how they can be a good thing?

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• Log RuntimeException thrown from thread created by Spring via the @Async annotation

  - by Eugen

  I'm having some difficulty logging RuntimeException from a thread. My system is: Java 7 (b118), Spring 3.0.5. The threads are not created by hand, but via Spring's @Async annotation, which creates it's own executor behind the scenes, so I don't really have the option of overriding any methods of the thread, FutureTask or anything low level. So my question is if Spring has any support or if there are any best practices for handling (logging) these type of exceptions? Any suggestions are appreciated. Thanks.

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• C++: Create abstract class with abstract method and override the method in a subclass

  - by Martijn Courteaux

  Hi, How to create in C++ an abstract class with some abstract methods that I want to override in a subclass? How should the .h file look? Is there a .cpp, if so how should it look? In Java it would look like this: abstract class GameObject { public abstract void update(); public abstract void paint(Graphics g); } class Player extends GameObject { @Override public void update() { // ... } @Override public void paint(Graphics g) { // ... } } // In my game loop: for (int i = 0; i < objects.size(); i++) { objects.get(i).update(); } for (int i = 0; i < objects.size(); i++) { objects.get(i).paint(g); } Translating this code to C++ is enough for me.

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• How to keep the popup menu of a JComboBox open on populating it ?

  - by Stormshadow

  I have a JComboBox on my Panel. One of the popup menu items is 'More' and when I click that I fetch more menu items and add them to the existing list. After this, I wish to keep the popup menu open so that the user realizes that more items have been fetched however, the popup closes. The event handler code I am using is as follows public void actionPerformed(ActionEvent e) { if (e.getSource() == myCombo) { JComboBox selectedBox = (JComboBox) e.getSource(); String item = (String) selectedBox.getSelectedItem(); if (item.toLowerCase().equals("more")) { fetchItems(selectedBox); } selectedBox.showPopup(); selectedBox.setPopupVisible(true); } } private void fetchItems(JComboBox box) { box.removeAllItems(); /* code to fetch items and store them in the Set<String> items */ for (String s : items) { box.addItem(s); } } I do not understand why the showPopup() and setPopupVisible() methods are not functioning as expected.

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• ASP.NET: How can I properly redirect requests with 404 errors?

  - by Adrian Grigore

  Hi, I'd like my ASP.NET MVC application to redirect failed requests to matching action methods of a certain controller. This works fine on my development machine running Windows 7, but not on my production machine running Windows 2008 R2. I set up my web.config as follows: <customErrors mode="On" defaultRedirect="/Error/ServerError/500"> <error statusCode="403" redirect="/Error/AccessDenied" /> <error statusCode="404" redirect="/Error/FileNotFound" /> </customErrors> This customErrors section works fine on both of my machines (production and development) for 500 Internal Server errors. It also works fine for 404 errors on my development machine. However, it does not properly redirect 404 errors on the production machine. Instead of /Error/FileNotFound, I get the standard 404 page that comes with IIS 7. What could be the problem here?

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• Fast parsing of PHP in C#

  - by Jessica Shea

  Hello there, I've got a requirement for parsing PHP files in C#. We essentially require some of the devs in another country to upload PHP files and once uploaded we need to check the php files and get a list of all the methods and classes/functions etc. I thought of using a regex but I can't workout if a function belongs to a class etc, so I was wondering if theres already something 'out there' that will parse out PHP files and spit out its functions (I'm trying to avoid writing a full blow AST implementation). Does anyone have any idea? I looked at Coco/R but I couldn't find a PHP grammar file. I'm using .NET 2.0 and C#.

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• Show facebook status stream of a dedicated person on a website

  - by Pascal

  Hi all, I've been stomping at this all day :( I want to display a status feed of both twitter and facebook on my website. For twitter, this is not a problem, as my account is public, I can easily get the feed. Facebook however, is a whole different story! I can't seem to find an easy way to just get my last status updates and display it on my website. The code I currently have, needs authentication of the visitor, and I don't want that! This is my current code: $facebook = new Facebook($api_key, $secret); $stream = $facebook->api_client->fql_query("SELECT message,source,time FROM status WHERE uid = $user_id LIMIT 6"); I've seen several possible solutions, including the RSS feed, but as Facebook keeps changing the way their site works, none of the previous methods I've seen (including those from as late as januari) currently work! Is there anybody who can provide me with a currently working solution to this (simple?) problem?

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• changing a picker to table view OR having multiple table views on the same view

  - by Brodie4598

  Hello - My iPad app was rejected due to my use of a picker. The picker was used to control a table view. In my view, a picker was displaying a series of items and when one of those items was selected, it used that selection to populate a table with data. (hopefully that makes sense). Now I need to do this without the picker so I need to have the data that was in the picker be represented in a table view. My question, is how do I have multiple tableViews in the same view? I'm guessing I need to have some kind of if statement in the tableview delegate methods, but I'm not quite sure what the if statement needs to be. Or maybe i'm thinking of this the totally wrong way thanks

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• does a switch idiom make sense in this case?

  - by the ungoverned

  I'm writing a parser/handler for a network protocol; the protocol is predefined and I am writing an adapter, in python. In the process of decoding the incoming messages, I've been considering using the idiom I've seen suggested elsewhere for "switch" in python: use a hash table whose keys are the field you want to match on (a string in this case) and whose values are callable expressions: self.switchTab = { 'N': self.handleN, 'M': self.handleM, ... } Where self.handleN, etc., are methods on the current class. The actual switch looks like this: self.switchTab[selector]() According to some profiling I've done with cProfile (and Python 2.5.2) this is actually a little bit faster than a chain of if..elif... statements. My question is, do folks think this is a reasonable choice? I can't imagine that re-framing this in terms of objects and polymorphism would be as fast, and I think the code looks reasonably clear to a reader.

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• Designing constructors around type erasure in Java

  - by Internet Friend

  Yesterday, I was designing a Java class which I wanted to be initalized with Lists of various generic types: TheClass(List<String> list) { ... } TheClass(List<OtherType> list) { ... } This will not compile, as the constructors have the same erasure. I just went with factory methods differentiated by their names instead: public static TheClass createWithStrings(List<String> list) public static TheClass createWithOtherTypes(List<OtherType> list) This is less than optimal, as there isn't a single obvious location where all the different options for creating instances are available. I tried to search for better design ideas, but found surprisingly few results. What other patterns exist for designing around this problem?

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• Scala loop returns as Unit and compiler points to "for" syntax?

  - by DeLongey

  Seems like Unit is the theme of my troubles today. I'm porting a JSON deserializer that uses Gson and when it comes to this for loop: def deserialize(json:JsonElement, typeOfT:Type, context:JsonDeserializationContext) = { var eventData = new EventData(null, null) var jsonObject = json.getAsJsonObject for(entry <- jsonObject.entrySet()) { var key = entry.getKey() var element = entry.getValue() element if("previous_attributes".equals(key)) { var previousAttributes = new scala.collection.mutable.HashMap[String, Object]() populateMapFromJSONObject(previousAttributes, element.getAsJsonObject()) eventData.setPreviousAttributes(previousAttributes) eventData } else if ("object".equals(key)) { val `type` = element.getAsJsonObject().get("object").getAsString() var cl = objectMap.get(`type`).asInstanceOf[StripeObject] var `object` = abstractObject.retrieve(cl, key) eventData.setObject(`object`) eventData } } } The compiler spits out the error type mismatch; found : Unit required: com.stripe.EventData and it points to this line here: for(entry <- jsonObject.entrySet()) Questions Confirm that it is indeed the Gson method entrySet() appearing as unit? If not, what part of the code is creating the issue? I've set return types/values for eventData class methods Is there a workaround for the Gson Unit issue? Thanks!

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• Handling auto-incrementing IDENTITY SQL Server fields with LINQ to SQL in C#

  - by Maxim Z.

  I'm building an ASP.NET MVC site that uses LINQ to SQL to connect to SQL Server, where I have a table that has an IDENTITY bigint primary key column that represents an ID. In one of my code methods, I need to create an object of that table to get its ID, which I will place into another object based on another table (FK-to-PK relationship). At what point is the IDENTITY column value generated and how can I obtain it from my code? Is the right approach to: Create the object that has the IDENTITY column Do an InsertOnSubmit() and SubmitChanges() to submit the object to the database table Get the value of the ID property of the object

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• Using Routing helpers in a Rake task

  - by trobrock

  I have a rake task that sends out the next 'x' invitations to join a beta it uses this code: desc "This will send out the next batch of invites for the beta" task :send_invites => :environment do limit = ENV['limit'] c = 0 invitation = Invitation.all(:conditions => { :sent_at => nil, :sender_id => nil }, :limit => limit).each do |i| Mailer.deliver_invitation(i, register_url(i.token)) c.increment! end puts "Sent #{c} invitations." end I need to pass in the 'register_url' to the Mailer in order for the link to show up in the email, but since this is running from a rake task and not from a request it does not have a access to the helper methods. What is the best way of achieving this?

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• link with static library vs individual object files

  - by dododo

  For a reason i want to unpack a static lib (libx.a) into individual object files (a.o b.o c.o), and specify these object files (a.o b.o c.o) in the linker input list instead of libx.a, with other linker options remaining the same. However, i have noticed the above change has resulted in quite some difference in the output executable. Basically, (a.o b.o c.o) method will result in larger output size. So what's the difference between the two methods (libx.a and individual object files)? And is there a way to work around? The GNU binutil (for and ar ld) version i'm using is 2.16.1 Thanks.

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• Why is Javascript's Math.floor the slowest way to calculate floor in Javascript?

  - by z5h

  I'm generally not a fan of microbenchmarks. But this one has a very interesting result. http://ernestdelgado.com/archive/benchmark-on-the-floor/ It suggests that Math.floor is the SLOWEST way to calculate floor in Javascript. ~~n, n|n, n&n all being faster. This seems pretty shocking as I would expect that people implementing Javascript in today's modern browsers would be some pretty smart people. Does floor do something important that the other methods fail to do? Is there any reason to use it?

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• Interface helpers or delegating interface parent

  - by Craig Peterson

  If I have an existing IInterface descendant implemented by a third party, and I want to add helper routines, does Delphi provide any easy way to do so without redirecting every interface method manually? That is, given an interface like so: IFoo = interface procedure Foo1; procedure Foo2; ... procedure FooN; end; Is anything similar to the following supported? IFooHelper = interface helper for IFoo procedure Bar; end; or IFooBar = interface(IFoo) procedure Bar; end; TFooBar = interface(TInterfacedObject, IFoo, IFooBar) private FFoo: IFoo; public procedure Bar; property Foo: IFoo implements IFoo; end; I'm specifically wondering about ways to that allow me to always refer to IFoo, IFooBar, or TFooBar, without switching between them, and without adding all of IFoo's methods to TFooBar.

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