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• How do I get every nth row in a table, or how do I break up a subset of a table into sets or rows of

  - by Jherico

  I have a table of heterogeneous pieces of data identified by a primary key (ID) and a type identifier (TYPE_ID). I would like to be able to perform a query that returns me a set of ranges for a given type broken into even page sizes. For instance, if there are 10,000 records of type '1' and I specify a page size of 1000, I want 10 pairs of numbers back representing values I can use in a BETWEEN clause in subsequent queries to query the DB 1000 records at a time. My initial attempt was something like this select id, rownum from CONTENT_TABLE where type_id = ? and mod(rownum, ?) = 0 But this doesn't work.

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• Archiving rows dynamically

  - by Serge

  I was wondering what would be the best solution to dynamically archive rows. For instance when a user marks a task as completed, that task needs to be archived yet still accessible. What would be the best practices for achieving this? Should I just leave it all in the same table and leave out completed tasks from the queries? I'm afraid that over time the table will become huge (1,000,000 rows in a year or less). Or should I create another table ie task_archive and query that row whenever data is needed from it? I know similar questions have been asked before but most of them where about archiving thousands of rows simultaneously, I just need to know what would be the best method (and why) to archive 1 row at a time once it's been marked completed

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• How do i make a copy of an object? Javascript

  - by acidzombie24

  I have a class in json format. I would like to make two instance. Right now (its pretty obvious why) when i 'make' two objects i really have 2 vars pointing to one. (b.blah = 'z' will make a.blah=='z') How do i make a copy of an object? var template = { blah: 0, init: function (storageObj) { blah = storageObj; return this; //problem here }, func2: function (tagElement) { }, } a = template.init($('form [name=data]').eq(0)); b = template.init($('form [name=data2]').eq(0));

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• ASP.NET null reference exception

  - by nanek

  Please help me to figure out what is wrong with this code: I have ASP.NET page with one button visible. When user clicks it - it instances MyClass (its implementation is in AppCode directory) and turns invisible (button2 becomes visible). When I click button2 it raises "Object reference not set to an instance of an object" Exception. What seems to be the problem? { public MyClass noviTest; protected void Page_Load(object sender, EventArgs e) { } protected void Button1_Click(object sender, EventArgs e) { noviTest = new MyClass(TextBox1.Text); Button1.Visible = false; Button2.Visible = true; } protected void Button2_Click(object sender, EventArgs e) { Label1.Text=noviTest.getID; //this is the critical line } } Thank You in advance, Regards

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• Unboxing object containing a value which is known to be assignable to an integer variable

  - by Wim Coenen

  If I have an object instance and I know it is actually a boxed integer, then I can simply cast it back to int like this: object o = GetSomethingByName("foo"); int i = (int)o; However, I don't actually know that the value is an integer. I only know that it can be assigned to an integer. For example, it could be a byte, and the above code would throw InvalidCastException in that case. Instead I would have to do this: object o = GetSomethingByName("foo"); int i = (int)(byte)o; The value could also be a short, or something else which can be assigned to an int. How do I generalize my code to handle all those cases (without handling each possibility separately)?

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• What is dbReferenceProperty?

  - by user246114

  Hi, In the python app engine docs, I see something called dbReferenceProperty. I can't understand what it is, or how it's used. I'm using the java interface to app engine, so I'm not sure if there's an equivalent. I'm interested in it because it sounds like some sort of pseudo-join, where we can point a property of a class to some other object's value - something like if we had: class User { private String mPhotoUrl; private String mPhone; private String mState; private String mCountry; .. etc .. } class UserLite { @ReferenceProperty User.mPhotoUrl; private String mPhotoUrl; } then if we had to update a User object's mPhotoUrl value, the change would somehow propagate out to all UserLite instances referencing it, rather than having to update every UserLite object instance manually, Thanks

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• How do I search for values in a dictionary

  - by fishhead

  what would be the best way to search for a value in a dictionary. for instance I would like to search for modified objects, would going through the entire collection be the only way to do this? c#, .net 2.0 class RecA { public bool modified {get;set:} public string{get;set;} } class RecA_Dic : Dictionary<int,Rec_A> { public bool GetItemByKey(int key,out obj) { return this.TryGetValue(key, out obj); } public List<Rec_A> getModifiedItems() { List<Rec_A> li = new List<Rec_A>(); for(int i=0;i<this.count;i++) if (((Rec_A)this[i]).modified == true) li.Add((Rec_A)this[i]); return li; } }

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• Why need to call NSTimer again in this code?

  - by Tattat

  - (void) applicationDidFinishLaunching:(UIApplication *)application { //set up main loop [NSTimer scheduledTimerWithTimeInterval:0.033 target:self selector:@selector(gameLoop:) userInfo:nil repeats:NO]; //create instance of the first GameState [self doStateChange:[gsMain class]]; } - (void) gameLoop: (id) sender { [((GameState*)viewController.view) Update]; [((GameState*)viewController.view) Render]; [NSTimer scheduledTimerWithTimeInterval:0.033 target:self selector:@selector(gameLoop:) userInfo:nil repeats:NO]; } This code is from a iPhone game development book. I don't know why the gameLoop method need to call the NSTimer again? in the applicationDidFinishLaunching, it set the NSTimer to do, why don't let it do every 0.033s, why add the same NSTimer code in the gameLoop method? thz.

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• std::out_of_range error?

  - by vette982

  I'm dealing with a file with a linked list of lines with each node looking like this: struct TextLine{ //The actual text string text; //The line number of the document int line_num; //A pointer to the next line TextLine * next; }; and I'm writing a function that adds spaces at the beginning of the lines found in the variable text, by calling functions like linelist_ptr->text.insert(0,1,'\t'); The program compiles, but when I run it I get this error: terminate called after throwing an instance of 'std::out_of_range' what(): basic_string::at Aborted Any ideas?

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• Multi-threading does not work correctly using std::thread (C++ 11)

  - by user1364743

  I coded a small c++ program to try to understand how multi-threading works using std::thread. Here's the step of my program execution : Initialization of a 5x5 matrix of integers with a unique value '42' contained in the class 'Toto' (initialized in the main). I print the initialized 5x5 matrix. Declaration of std::vector of 5 threads. I attach all threads respectively with their task (threadTask method). Each thread will manipulate a std::vector<int> instance. I join all threads. I print the new state of my 5x5 matrix. Here's the output : 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 It should be : 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 0 0 0 0 0 1 1 1 1 1 2 2 2 2 2 3 3 3 3 3 4 4 4 4 4 Here's the code sample : #include <iostream> #include <vector> #include <thread> class Toto { public: /* ** Initialize a 5x5 matrix with the 42 value. */ void initData(void) { for (int y = 0; y < 5; y++) { std::vector<int> vec; for (int x = 0; x < 5; x++) { vec.push_back(42); } this->m_data.push_back(vec); } } /* ** Display the whole matrix. */ void printData(void) const { for (int y = 0; y < 5; y++) { for (int x = 0; x < 5; x++) { printf("%d ", this->m_data[y][x]); } printf("\n"); } printf("\n"); } /* ** Function attached to the thread (thread task). ** Replace the original '42' value by another one. */ void threadTask(std::vector<int> &list, int value) { for (int x = 0; x < 5; x++) { list[x] = value; } } /* ** Return the m_data instance propertie. */ std::vector<std::vector<int> > &getData(void) { return (this->m_data); } private: std::vector<std::vector<int> > m_data; }; int main(void) { Toto toto; toto.initData(); toto.printData(); //Display the original 5x5 matrix (first display). std::vector<std::thread> threadList(5); //Initialization of vector of 5 threads. for (int i = 0; i < 5; i++) { //Threads initializationss std::vector<int> vec = toto.getData()[i]; //Get each sub-vectors. threadList.at(i) = std::thread(&Toto::threadTask, toto, vec, i); //Each thread will be attached to a specific vector. } for (int j = 0; j < 5; j++) { threadList.at(j).join(); } toto.printData(); //Second display. getchar(); return (0); } However, in the method threadTask, if I print the variable list[x], the output is correct. I think I can't print the correct data in the main because the printData() call is in the main thread and the display in the threadTask function is correct because the method is executed in its own thread (not the main one). It's strange, it means that all threads created in a parent processes can't modified the data in this parent processes ? I think I forget something in my code. I'm really lost. Does anyone can help me, please ? Thank a lot in advance for your help.

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• Displaying message if no photo present...

  - by bgadoci

  I am using the code: <%= image_tag site.photo.url(:small) if site.photo.file? %> to tell my app to display nothing if there is no photo associated with a particular post (site in this case). Is there a way to render a message along w/ this. For instance "no image with the post". I tried simply doing <%= if site.photo.file? %> <p> no image with this site </p> <% end %> But that doesn't seem to work. New to ruby and rails if you can't tell.

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• Start a thread using a method pointer

  - by Michael

  Hi ! I'm trying to develop a thread abstraction (POSIX thread and thread from the Windows API), and I would very much like it to be able to start them with a method pointer, and not a function pointer. What I would like to do is an abstraction of thread being a class with a pure virtual method "runThread", which would be implanted in the future threaded class. I don't know yet about the Windows thread, but to start a POSIX thread, you need a function pointer, and not a method pointer. And I can't manage to find a way to associate a method with an instance so it could work as a function. I probably just can't find the keywords (and I've been searching a lot), I think it's pretty much what Boost::Bind() does, so it must exist. Can you help me ?

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• Rails 2.3.5: flash[:notice] disappears after redirect_to call

  - by xyzman

  Here I've got two controller methods: def invite if request.post? begin email = AccountMailer.create_invite(@user,url) AccountMailer.deliver(email) flash[:notice] = "Invitation email sent to #{@user.email}" rescue #mail delivery failed flash[:error] = "Failed to deliver invitation" end redirect_to :action => :show, :id => @user.id end end and def show @title = "User #{@user.full_name}" end The problem is, when I send an invitation, and get redirected to ./show, I see no messages at all. If I change redirect_to to render, the message appears. Still, isn't it intended for flash to work in the immediate subsequent requests? BTW, I'm using Rails+Passenger setup, could it be so that redirected request goes to another application instance?

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• What advantage does Monad give us over an Applicative?

  - by arrowdodger

  I've read this article, but didn't understand last section. The author says that Monad gives us context sensitivity, but it's possible to achieve the same result using only an Applicative instance: let maybeAge = (\futureYear birthYear -> if futureYear < birthYear then yearDiff birthYear futureYear else yearDiff futureYear birthYear) <$> (readMay futureYearString) <*> (readMay birthYearString) It's uglier for sure, but beside that I don't see why we need Monad. Can anyone clear this up for me?

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• Where is the rand php function located? localhost php running, path of default functions?

  - by Bona Chon

  I have a local server installed on my Mac (MAMP). My question is, where I can find the php functions in my computer? What is the path to the functions folder? For instance, rand() time() isset() explode(). I would like to se the code to learn of it. I have a while looking for it, but I can't find it. Or is it that is already compiled? Can someone help me here? I'm kind of lost. Thanks people. EDIT: can you be a little bit more positive? I;m trying to learn here, forgive me if I'm not to smart for you. Thanks again. Explanations would help better than giving links I guess?

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• How to get the app a Django model is from?

  - by e-satis

  I have a model with a generic relation: TrackedItem --- genericrelation ---> any model I would like to be able to generically get, from the initial model, the tracked item. I should be able to do it on any model without modifying it. To do that I need to get the content type and the object id. Getting the object id is easy since I have the model instance, but getting the content type is not: ContentType.object.filter requires the model (which is just content_object.__class__.__name__) and the app_label. I have no idea of how to get in a reliable way the app in which a model is. For now I do app = content_object.__module__.split(".")[0], but it doesn't work with django contrib apps.

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• How do you extend a Ruby module with macro-like metaprogramming methods?

  - by Ian Terrell

  Consider the following extension (the pattern popularized by several Rails plugins over the years): module Extension def self.included(recipient) recipient.extend ClassMethods recipient.class_eval { include InstanceMethods } end module ClassMethods def macro_method puts "Called macro_method within #{self.name}" end end module InstanceMethods def instance_method puts "Called instance_method within #{self.object_id}" end end end If you wished to expose this to every class, you can do the following: Object.send :include, Extension Now you can define any class and use the macro method: class FooClass macro_method end #=> Called macro_method within FooClass And instances can use the instance methods: FooClass.new.instance_method #=> Called instance_method within 2148182320 But even though Module.is_a?(Object), you cannot use the macro method in a module: module FooModule macro_method end #=> undefined local variable or method `macro_method' for FooModule:Module (NameError) This is true even if you explicitly include the original Extension into Module with Module.send(:include, Extension). How do you add macro like methods to Ruby modules?

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• Duel Masters game in Java

  - by Arun Ramasubramanian

  I was trying to make a Duel Masters card game in Java using BlueJ, and came up with a lot of ideas. However, I could not exactly figure out how to sort a deck on basis of the card names in the game. I have an array of Card objects(each has, as its instance variables: String name, int cost, int civ), and I want to sort them based on name. ie: if I have the cards "Pyrofighter Magnus", "Bazagazeal Dragon" and another "Pyrofighter Magnus" in the array, the cards should be sorted on basis of their names. I know that I could use compareTo(), but is there an easier method? Anyone? Remember, the method that sorts the cards should be a modifier.

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• Android App: Proximity

  - by Eclipser

  Is there an API for Android that will find other people nearby running the same app? For instance, if you were to perform a "scan" it tries to find other people running the same app nearby. Would it be possible to perform the same task across multiple OS (Android, iPhone, Windows, etc.)? Or would the best way be to just have the app communicate to a server your location and have a server-side app that pushes a list of others nearby??? My goal is to find an easy way to eventually transmit data between two devices contigent on those that are nearby.

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• Clone a 'link' in SWT

  - by Steve

  I have a table of information that includes a username, an ip address, and a timestamp. What I wanted to do was to have the ip address contained within a link object that when the link is clicked it utilizes bgp.he.net to get information about the host/IP address. I have tried creating threads to resolve the IP addresses but it is often a large amount of IP addresses and I read that InetAddress#getByName isn't non-blocking, so I figured having links that go to this site is the next best thing. Question is: Is it possible to have links for each of my IP addresses in the table without creating a new link object for each row? I don't know how bad that would be on memory usage which is why I'm inquiring about cloning an instance of an IP and having the link open bgp.he.net/link.getText()

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• Hibernate Criteria API: get n random rows

  - by hadrien

  I can't figure out how to fetch n random rows from a criteria instance: Criteria criteria = session.createCriteria(Table.class); criteria.add(Restrictions.eq('fieldVariable', anyValue)); ... Then what? I can't find any doc with Criteria API Does it mean I should use HQL instead? Thanx! EDIT: I get the number of rows by: int max = criteria.setProjecxtion(Projections.rowCount()).uniqueResult(); How do I fetch n random rows with indexes between 0 and max? Thx again!

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• Android sql creating database once

  - by semajhan

  One thing i'm not understanding is how to create the database and data just once in an android application. I extend SQLiteOpenHelper and use a DataHelper class that to manipulate data. Now, I have addEvent() and updateEvent() within the DataHelper class. I create an instance of DataHelper in my Activity and addEvent() a couple of times to insert data. Well, now I don't know how to just do that once. If I restart the app, its just going to "addEvent()" again and so the data is being reset every time. Sorry for the probably really REALLY noob question. The only solution I found was not using the DataHelper class and just adding data "manually" within the onCreate() method in SQLiteOpenHelper.

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• How can I declare a pointer structure using {}?

  - by Y_Y

  This probably is one of the easiest question ever in C programming language... I have the following code: typedef struct node { int data; struct node * after; struct node * before; }node; struct node head = {10,&head,&head}; Is there a way I can make head to be *head [make it a pointer] and still have the availability to use '{ }' [{10,&head,&head}] to declare an instance of head and still leave it out in the global scope? For example: //not legal!!! struct node *head = {10,&head,&head};

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• Javascript - document.links.className ?

  - by Slevin

  I have a Javascript question that I am curious about. When using: var test = document.links(arrayNum).name; Is it possible to dig deeper into specifying links? For instance, if there is just a group of links from within a div with an id that you would like to target as opposed to all the links on the page could you write something like: var test = document.getElementById('divId').links(arrayNum).name; Or could I add a class to the statement to target only the links associated with it? var test = document.links.className(arrayNum).name; Is anything like this feasible?

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• Is there a need for zero-out DIV's margin and padding?

  - by ssg

  I wonder if on any browser div element comes with a preset margin/padding value other than zero. As far as I know, div and span come with zero padding and margin values by standard to make them suitable canvas for style decoration. Even better, is there a definite standard for default styles for all elements that is cross-browser which we can make assumptions upon? For instance FORM comes with top/bottom margins, OL/UL come with padding-left's. I occasionally see a * { margin: 0; padding: 0; } and this just looks like a dirty hack without knowing the reasons or consequences. Anyone has any better approach to this?

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