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  • Beginner += in Ruby

    - by WANNABE
    Looking at this block, I can follow the whole program until I hit, sum += square. What is he point of this line, what does it say??? sum = 0 [1, 2, 3, 4].each do |value| square = value * value sum += square end puts sum

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  • Appending javascript code piece to end of the body tag

    - by uzay95
    I am looking for a way to insert javascript code block to end of ASP.NET page. Page.ClientScript.RegisterClientScriptBlock(typeof(Page), "showVideo", sScript, true); is appending to body but js codes are always requesting some js files didn't load or some functions are below of the script. How can i append scripts that i generated dynamically to the bottom of body? Thanks for your help.

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  • Singleton issue causing a buffer overrun

    - by Rudiger
    Hi everyone, Ive created a singleton to store 2 arrays: @interface Globals : NSObject { NSMutableArray *items; NSMutableArray *extras; } + (Globals *)sharedInstance; @property (nonatomic, assign) NSMutableArray *items; @property (nonatomic, assign) NSMutableArray *extras; @end @implementation Globals @synthesize items, extras; + (Globals *)sharedInstance { static Globals *myInstance = nil; @synchronized(self) { if(!myInstance) { myInstance = [[Globals alloc] init]; } } return myInstance; } -(void)dealloc { [items release]; [extras release]; [super dealloc]; } @end When I set the Arrays in the singleton from the App delegate and then output them to NSLog it displays what is expected. But when I call it from a view controller further into the App it displays the first entry fine, some of the second entry and then garbage which is i assume a buffer overrun, sometimes it also crashes. I set the singleton array in the appDelegate like so: Globals *sharedInstance = [Globals sharedInstance]; [sharedInstance setItems:items]; and retrieve it: [[[sharedInstance items] objectAtIndex:indexPath.row] objectForKey:@"name"]; cell.description.text = [[[sharedInstance items] objectAtIndex:indexPath.row] objectForKey:@"description"]; Name works fine in both cells if there is 2, description works in the first case, never in the second case. Is it because the arrays in my singleton aren't static? If so why is it outputting the first entry fine? Cheers for any help.

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  • Do the 'up to date' guarantees provided by final field in Java's memory model extend to indirect ref

    - by mattbh
    The Java language spec defines semantics of final fields in section 17.5: The usage model for final fields is a simple one. Set the final fields for an object in that object's constructor. Do not write a reference to the object being constructed in a place where another thread can see it before the object's constructor is finished. If this is followed, then when the object is seen by another thread, that thread will always see the correctly constructed version of that object's final fields. It will also see versions of any object or array referenced by those final fields that are at least as up-to-date as the final fields are. My question is - does the 'up-to-date' guarantee extend to the contents of nested arrays, and nested objects? An example scenario: Thread A constructs a HashMap of ArrayLists, then assigns the HashMap to final field 'myFinal' in an instance of class 'MyClass' Thread B sees a (non-synchronized) reference to the MyClass instance and reads 'myFinal', and accesses and reads the contents of one of the ArrayLists In this scenario, are the members of the ArrayList as seen by Thread B guaranteed to be at least as up to date as they were when MyClass's constructor completed?

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  • Wait between tasks with SingleThreadExecutor

    - by Lord.Quackstar
    I am trying to (simply) make a blocking thread queue, where when a task is submitted the method waits until its finished executing. The hard part though is the wait. Here's my 12:30 AM code that I think is overkill: public void sendMsg(final BotMessage msg) { try { Future task; synchronized(msgQueue) { task = msgQueue.submit(new Runnable() { public void run() { sendRawLine("PRIVMSG " + msg.channel + " :" + msg.message); } }); //Add a seperate wait so next runnable doesn't get executed yet but //above one unblocks msgQueue.submit(new Runnable() { public void run() { try { Thread.sleep(Controller.msgWait); } catch (InterruptedException e) { log.error("Wait to send message interupted", e); } } }); } //Block until done task.get(); } catch (ExecutionException e) { log.error("Couldn't schedule send message to be executed", e); } catch (InterruptedException e) { log.error("Wait to send message interupted", e); } } As you can see, there's alot of extra code there just to make it wait 1.7 seconds between tasks. Is there an easier and cleaner solution out there or is this it?

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  • Speed/expensive of SQLite query vs. List.contains() for "in-set" icon on list rows

    - by kpdvx
    An application I'm developing requires that the app main a local list of things, let's say books, in a local "library." Users can access their local library of books and search for books using a remote web service. The app will be aware of other users of the app through this web service, and users can browse other users' lists of books in their library. Each book is identified by a unique bookId (represented as an int). When viewing books returned through a search result or when viewing another user's book library, the individual list row cells need to visually represent if the book is in the user's local library or not. A user can have at most 5,000 books in the library, stored in SQLite on the device (and synchronized with the remote web service). My question is, to determine if the book shown in the list row is in the user's library, would it be better to directly ask SQLite (via SELECT COUNT(*)...) or to maintain, in-memory, a List or int[] array of some sort containing the unique bookIds. So, on each row display do I query SQLite or check if the List or int[] array contains the unique bookId? Because the user can have at most 5,000 books, each bookId occupies 4 bytes so at most this would use ~ 20kB. In thinking about this, and in typing this out, it seems obvious to me that it would be far better for performance if I maintained a list or int[] array of in-library bookIds vs. querying SQLite (the only caveat to maintaining an int[] array is that if books are added or removed I'll need to grow or shrink the array by hand, so with this option I'll most likely use an ArrayList or Vector, though I'm not sure of the additional memory overhead of using Integer objects as opposed to primitives). Opinions, thoughts, suggestions?

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  • Easy way to keep counting up infinitely

    - by Andrew Alexander
    What's a good way to keep counting up infinitely? I'm trying to write a condition that will keep going until there's no value in a database, so it's going to iterate from 0, up to theoretically infinity (inside a try block, of course). How would I count upwards infinitely? Or should I use something else? I am looking for something similar to i++ in other languages, where it keeps iterating until failure.

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  • Determine asymmetric latencies in a network

    - by BeeOnRope
    Imagine you have many clustered servers, across many hosts, in a heterogeneous network environment, such that the connections between servers may have wildly varying latencies and bandwidth. You want to build a map of the connections between servers my transferring data between them. Of course, this map may become stale over time as the network topology changes - but lets ignore those complexities for now and assume the network is relatively static. Given the latencies between nodes in this host graph, calculating the bandwidth is a relative simply timing exercise. I'm having more difficulty with the latencies - however. To get round-trip time, it is a simple matter of timing a return-trip ping from the local host to a remote host - both timing events (start, stop) occur on the local host. What if I want one-way times under the assumption that the latency is not equal in both directions? Assuming that the clocks on the various hosts are not precisely synchronized (at least that their error is of the the same magnitude as the latencies involved) - how can I calculate the one-way latency? In a related question - is this asymmetric latency (where a link is quicker in direction than the other) common in practice? For what reasons/hardware configurations? Certainly I'm aware of asymmetric bandwidth scenarios, especially on last-mile consumer links such as DSL and Cable, but I'm not so sure about latency. Added: After considering the comment below, the second portion of the question is probably better off on serverfault.

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  • Android: Scheduling application to start with repeating alarms not working

    - by vikramagain
    I get my Broadcast receiver to set a recurring alarm, to fire up a service. Unfortunately this does not result in the service being called repeatedly (based on logcat). I've experimented with different values for the time interval too. Can someone help? (I'm testing through Eclipse on Android 3.2 Motorola xoom) Below is the code for the Broadcast receiver. alarm = (AlarmManager) arg0.getSystemService(Context.ALARM_SERVICE); Intent intentUploadService = new Intent (arg0, com.vikramdhunta.UploaderService.class); Calendar calendar = Calendar.getInstance(); calendar.setTimeInMillis(System.currentTimeMillis()); calendar.add(Calendar.SECOND, 3); PendingIntent pi = PendingIntent.getBroadcast(arg0, 0, intentUploadService , 0); alarm.setRepeating(AlarmManager.RTC_WAKEUP, calendar.getTimeInMillis(), 5, pi); Below is the code for the Service class public UploaderService() { super("UploaderService"); mycounterid = globalcounter++; } @Override protected void onHandleIntent(Intent intent) { synchronized(this) { try { for (int i = 1;i < 5;i++) { // doesn't do much right now.. but this should appear in logcat Log.i(TAG,"OK " + globalcounter++ + " uploading..." + System.currentTimeMillis()); } } catch(Exception e) { } } } @Override public void onCreate() { super.onCreate(); Log.d("TAG", "Service created."); } @Override public IBinder onBind(Intent arg0) { return null; } @Override public int onStartCommand(Intent intent, int flags, int startId) { Log.i(TAG, "Starting upload service..." + mycounterid); return super.onStartCommand(intent,flags,startId); }

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  • Implementing a kext that intercepts file system usage.

    - by UraN
    Hi, how do most of antivirus software block file system io in case of an infected file? I suppose all the magic resides in some custom kext to do that. Can anyone point me to some topics on this? Some working example would also be great. I've read apple docs about kext development, but mostly it's all about hardware drivers and i could not find what i need. Thanx.

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  • How can a client gracefully detect when a server disconnects?

    - by Ummar
    I am working on a client-server application. The client continuously reads data from server, so when a server is closed or disconnects then the client crashes. I tried a try/catch block, but it didn't work. My client application is written in C++. I want the client to display some proper message like "Server disconnected," then exit.

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  • Fold C Preprocessor in VIM

    - by Sunny
    Is it possible to fold C preprocessor in VIM. For example: #if defined(DEBUG) //some block of code myfunction(); #endif I want to fold it so that it becomes: +-- 4 lines: #if defined(DEBUG)---

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  • Exception handling in c#

    - by Lalit
    Hi all, I know how to use try...catch block in c#. Also know why it is using. but what is exact meaning of Exception handling ? see once i write the try {}.. Catch{} i handled null exception then what should happen? what are the standard for exception handling. means what should happen is normally expected if exception occur ?

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  • How do I ensure jQuery ajax call does not send a local copy of file?

    - by Tommy
    $.ajax({ type: 'GET', url: "string.txt", cache: false, success: function(str){ alert("Data is: "+ str); } }); In this example, string.txt is still sent to the cache (\Temporary Internet Files) How do I ensure that the file is not sent - read from the server only? Am I missing an option? I set cache to false but that does not block it from being sent to client. For example, ajax POST does not send a local copy..... Thanks

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  • HTTP DOM: request.use? Usage?

    - by Jim G.
    I'm looking at the following code block in javascript: var request = new Request(); if(request.Use()) // What exactly does this do? { // ...do stuff } else { // no ajax support? } I've never seen anyone invoke the request.Use() method. My Question: What exactly does request.Use() check? Does it in fact check for AJAX support? Can anyone redirect me to an online API reference?

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  • Can I display twovalues in a Silverlight TextBlock?

    - by Subhen
    Can I data bind two proporties values in a single textblock. For Example some thing like following, though this is noth the correct code: <TextBlock Margin="5" Text="{Binding property1,Binding property2}" Style="{StaticResource Style1}" /> I want to display two values in a single text block . Thanks, Subhendu

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  • How to avoid concurrent execution of a time-consuming task without blocking?

    - by Diego V
    I want to efficiently avoid concurrent execution of a time-consuming task in a heavily multi-threaded environment without making threads wait for a lock when another thread is already running the task. Instead, in that scenario, I want them to gracefully fail (i.e. skip its attempt to execute the task) as fast as possible. To illustrate the idea considerer this unsafe (has race condition!) code: private static boolean running = false; public void launchExpensiveTask() { if (running) return; // Do nothing running = true; try { runExpensiveTask(); } finally { running = false; } } I though about using a variation of Double-Checked Locking (consider that running is a primitive 32-bit field, hence atomic, it could work fine even for Java below 5 without the need of volatile). It could look like this: private static boolean running = false; public void launchExpensiveTask() { if (running) return; // Do nothing synchronized (ThisClass.class) { if (running) return; running = true; try { runExpensiveTask(); } finally { running = false; } } } Maybe I should also use a local copy of the field as well (not sure now, please tell me). But then I realized that anyway I will end with an inner synchronization block, that still could hold a thread with the right timing at monitor entrance until the original executor leaves the critical section (I know the odds usually are minimal but in this case we are thinking in several threads competing for this long-running resource). So, could you think in a better approach?

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  • Drupal: link to latest node of a certain content type

    - by james6848
    I have a link within a block. At the moment it goes to a list of newsletter nodes: <p><a href="<?php global $base_url; print $base_url;?>/news-events/newsletter">Read our latest newsletter</a></p> What I would prefer is to have it go to the latest node of the content type 'newsletter', is this possible?

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  • Question about array subscripting in C#

    - by Michael J
    Back in the old days of C, one could use array subscripting to address storage in very useful ways. For example, one could declare an array as such. This array represents an EEPROM image with 8 bit words. BYTE eepromImage[1024] = { ... }; And later refer to that array as if it were really multi-dimensional storage BYTE mpuImage[2][512] = eepromImage; I'm sure I have the syntax wrong, but I hope you get the idea. Anyway, this projected a two dimension image of what is really single dimensional storage. The two dimensional projection represents the EEPROM image when loaded into the memory of an MPU with 16 bit words. In C one could reference the storage multi-dimensionaly and change values and the changed values would show up in the real (single dimension) storage almost as if by magic. Is it possible to do this same thing using C#? Our current solution uses multiple arrays and event handlers to keep things synchronized. This kind of works but it is additional complexity that we would like to avoid if there is a better way.

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  • Using a Data Management Singleton

    - by Dan Ray
    Here's my singleton code (pretty much boilerplate): @interface DataManager : NSObject { NSMutableArray *eventList; } @property (nonatomic, retain) NSMutableArray *eventList; +(DataManager*)sharedDataManager; @end And then the .m: #import "DataManager.h" static DataManager *singletonDataManager = nil; @implementation DataManager @synthesize eventList; +(DataManager*)sharedDataManager { @synchronized(self) { if (!singletonDataManager) { singletonDataManager = [[DataManager alloc] init]; } } NSLog(@"Pulling a copy of shared manager."); return singletonDataManager; } So then in my AppDelegate, I load some stuff before launching my first view: NSMutableArray *eventList = [DataManager sharedDataManager].eventList; .... NSLog(@"Adding event %@ to eventList", event.title); [eventList addObject:event]; NSLog(@"eventList now has %d members", [eventList count]); [event release]; As you can see, I've peppered the code with NSLog love notes to myself. The output to the Log reads like: 2010-05-10 09:08:53.355 MyApp[2037:207] Adding event Woofstock Music Festival to eventList 2010-05-10 09:08:53.355 MyApp[2037:207] eventList now has 0 members 2010-05-10 09:08:53.411 MyApp[2037:207] Adding event Test Event for Staging to eventList 2010-05-10 09:08:53.411 MyApp[2037:207] eventList now has 0 members 2010-05-10 09:08:53.467 MyApp[2037:207] Adding event Montgomery Event to eventList 2010-05-10 09:08:53.467 MyApp[2037:207] eventList now has 0 members 2010-05-10 09:08:53.524 MyApp[2037:207] Adding event Alamance County Event For June to eventList 2010-05-10 09:08:53.524 MyApp[2037:207] eventList now has 0 members ... What gives? I have no errors getting to my eventList NSMutableArray. But I addObject: fails silently?

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