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Articles indexed in May 2010

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  • Determine signals connected to a given slot in Qt

    - by Cody Brocious
    I've injected myself into a Qt application, and I'm attempting to figure out what signals a given slot is connected to, but can't find any information on doing this. Is there a mechanism for doing this out of the box? If so, is this exposed to QtScript? (If not, I can wrap it easily enough.) If there is no such mechanism, what would be the best way to add it? I cannot manipulate the existing application outside of simple hooking, but I could hook QObject::connect and store the connections myself, just not sure if that's the best way to go about it.

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  • Using boost locks for RAII access to a semaphore

    - by dan
    Suppose I write a C++ semaphore class with an interface that models the boost Lockable concept (i.e. lock(); unlock(); try_lock(); etc.). Is it safe/recommended to use boost locks for RAII access to such an object? In other words, do boost locks (and/or other related parts of the boost thread library) assume that the Lockable concept will only be modeled by mutex-like objects which are locked and unlocked from the same thread? My guess is that it should be OK to use a semaphore as a model for Lockable. I've browsed through some of the boost source and it "seems" OK. The locks don't appear to store explicit references to this_thread or anything like that. Moreover, the Lockable concept doesn't have any function like whichThreadOwnsMe(). It also looks like I should even be able to pass a boost::unique_lock<MySemaphore> reference to boost::condition_variable_any::wait. However, the documentation is not explicitly clear about the requirements. To illustrate what I mean, consider a bare-bones binary semaphore class along these lines: class MySemaphore{ bool locked; boost::mutex mx; boost::condition_variable cv; public: void lock(){ boost::unique_lock<boost::mutex> lck(mx); while(locked) cv.wait(lck); locked=true; } void unlock(){ { boost::lock_guard<boost::mutex> lck(mx); if(!locked) error(); locked=false; } cv.notify_one(); } // bool try_lock(); void error(); etc. } Now suppose that somewhere, either on an object or globally, I have MySemaphore sem; I want to lock and unlock it using RAII. Also I want to be able to "pass" ownership of the lock from one thread to another. For example, in one thread I execute void doTask() { boost::unique_lock<MySemaphore> lock(sem); doSomeWorkWithSharedObject(); signalToSecondThread(); waitForSignalAck(); lock.release(); } While another thread is executing something like { waitForSignalFromFirstThread(); ackSignal(); boost::unique_lock<MySemaphore>(sem,boost::adopt_lock_t()); doMoreWorkWithSameSharedObject(); } The reason I am doing this is that I don't want anyone else to be able to get the lock on sem in between the time that the first thread executes doSomeWorkWithSharedObject() and the time the second executes doMoreWorkWithSameSharedObject(). Basically, I'm splitting one task into two parts. And the reason I'm splitting the task up is because (1) I want the first part of the task to get started as soon as possible, (2) I want to guarantee that the first part is complete before doTask() returns, and (3) I want the second, more time-consuming part of the task to be completed by another thread, possibly chosen from a pool of slave threads that are waiting around to finish tasks that have been started by master threads. NOTE: I recently posted this same question (sort of) here http://stackoverflow.com/questions/2754884/unlocking-a-mutex-from-a-different-thread-c but I confused mutexes with semaphores, and so the question about using boost locks didn't really get addressed.

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  • Deployed a Zend App on EC2 and its not working

    - by Gublooo
    Hey Guys, I'm confused about the problem and not sure if I can provide enough details. I have a php app built on Zend framework which I've successfully deployed on other hosting companies. I am now trying to move to Amazon EC2 I moved all my code and set my domain to point to the IP address. So far so good. Now when I access my home page say www.example.com - everything looks good - The home page opens up which means the IndexController is being called and the index method is properly executed which pulls data from the database and displays it in the index.phtml page. So this lets me to believe that everything is working fine. But every link I click on the home page whether its a simple contact us link - or any other action that I directly try to call even through the URL results in 404 Not Found The requested URL /user/add was not found on this server. Apache/2.2.9 (Fedora) Server at www.example.com Port 80 The interesting thing is the home page opens up fine when I call www.example.com but when I give the entire path which is www.example.com/index/index - I get the same above error. I have checked the logs and there are no errors. Has anyone encountered something similar or have any idea if I'm missing a simple step or something like rewrite rule maybe. Its running on LAMP Any ideas Thanks

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  • using R to estimate finite mixture model with underlying Markov process

    - by stevejb
    Hello, My apologies if this is more of a statistics question than an R question. I am trying to estimate the following model in R. y_t = mu0 (1 - S_t) + mu1 S_t + e_t e_t ~ N(0, sigma_t^2) sigma_t^2 = sigma_0^2 (1 - S_t) + sigma_1^2 S_t where mu_t = mu0 if S_t = 0, mu_t = mu1 if S_t = 1, and S_t is a Markov process, either 0 or 1, with transition probabilities P(S_t = 1 | S_t-1 = 1 ) = p and P(S_t = 0 | S_t-1 = 0 ) = q. Would 'flexmix' be a good library to use for this? I am new to this kind of statistics so any pointer to the right library would be appreciated. Thanks,

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  • Posting source code in blogger- fails with C# containers

    - by Lirik
    I tried the solutions that are posted in this related SO question and for the most part the code snippets are working, but there are some cases that are still getting garbled by Blogger when it publishes the blog. In particular, declaring generic containers seems to be most troublesome. Please see the code examples on my blog and in particular the section where I define the dictionary (http://mlai-lirik.blogspot.com/). I want to display this: static Dictionary<int, List<Delegate>> _delegate = new Dictionary<int,List<Delegate>>(); But blogger publishes this: static Dictionary<int, list=""><delegate>> _delegate = new Dictionary<int, list=""><delegate>>(); And it caps the end of my code section with this: </delegate></delegate></int,></delegate></int,> Apparently blogger thinks that the <int and <delegate> portion of the dictionary are some sort of HTML tags and it automatically attempts to close them at the end of the code snippet. Does anybody know how to get around this problem?

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  • Returning a users lat lng as a string iPhone

    - by Joshmattvander
    Is there a way to return the users location as a string from a model? I have a model thats job is to download same JSON data from a web service. When sending in my request I need to add ?lat=LAT_HERE&lng=LNG_HERE to the end of the string. I have seen tons of examples using the map or constantly updating a label. But I cant find out how to explicitly return the lat and lng values. Im only 2 days into iPhone dev so go easy on me :)

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  • Multiple forms using Rails & jQuery & AJAX

    - by biggie8199
    I have multiple coupons on a page and I'm trying to get comments to work on each coupon. So for each coupon i have a comments form. Im using jQuery + Ajax to accomplish this. Here's what my code looks like. Coupon Page <p>Comments:</p> <% form_for(@comment) do |f| %> <%= f.label :body %><br /><%= f.text_field :body, :size => "24" %> <%= f.hidden_field :coupon_id, :value => coupon.id %> <%= f.submit "Save" %> <% end %> Application.js jQuery.ajaxSetup({ 'beforeSend': function(xhr) {xhr.setRequestHeader("Accept", "text/javascript")} }) jQuery.fn.submitWithAjax = function() { this.submit(function() { $.post(this.action, $(this).serialize(), null, "script"); return false; }) return this; }; $(document).ready(function() { $("#new_comment").submitWithAjax(); }) I tried changing the jQuery selector to a class $(".new_comment").submitWithAjax(); Thinking that would work, now all the submit buttons work, however it posts only the first form on the page. What can I change to make it so ajax submits the correct form and not the first one?

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  • PHP Form POST to external URL with Redirect to another URL

    - by Marlon
    So, what I am trying to accomplish is have a self-posting PHP form, POST to an external page (using CURL) which in turn redirects to another page. Currently, what is happening is that once I click "Submit" on the form (in contact.php) it will POST to itself (as it is a self-posting form). The script then prepares the POST using CURL and performs the post. The external page does its processing and then, the external page is supposed to redirect back to another page, in a referring domain. However, what happens instead, is that it seems like the contact.php page loads the HTML from the page the external page redirected to, and then, the contact.php's HTML loads after that, ON THE SAME PAGE. The effect, is what looks like two separate pages rendered as one page. Naturally, I just want to perform the POST and have the browser render the page it is supposed to redirect to as specified by the external page. Here is the code I have so far: <?php if(isset($_POST['submit'])) { doCURLPost(); } function doCURLPost() { $emailid = "2, 4"; $hotel = $_POST['hotel']; //you will need to setup an array of fields to post with //then create the post string $data = array ( "recipient" => $emailid, "subject" => "Hotel Contact Form", "redirect" => "http://www.localhost.com/thanx.htm", "Will be staying in hotel: " => $_POST['hotel'], "Name" => $_POST['Name'], "Phone" => $_POST['Phone'], "Comments" => $_POST['Comments']); $ch = curl_init(); curl_setopt($ch, CURLOPT_URL, "http://www.externallink.com/external.aspx"); curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1); curl_setopt($ch, CURLOPT_FOLLOWLOCATION, true); curl_setopt($ch, CURLOPT_POST, true); curl_setopt($ch, CURLOPT_POSTFIELDS, $data); curl_setopt($ch, CURLOPT_HTTPHEADER, array("Referer: http://www.localhost.com/contact.php")); $output = curl_exec($ch); $info = curl_getinfo($ch); curl_close($ch); } ?>

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  • jQuery scrollTop() doesn't seem to work in Safari or Chrome (Windows)

    - by Pointy
    I've got a simple setup to allow a "help"-style window to be loaded and scrolled to a particular point on the page. More or less the code looks like this: var target = /* code */; target.offsetParent().scrollTop(target.offset().top - fudgeValue); The target of the scroll and the fudge value are determined by a couple of hints dropped on the page, and I'm having no problems with that part of this mechanism anywhere. In Firefox and IE8, the above code works exactly like I want: the scrolled box (in this case, the page body) correctly scrolls the contained stuff to the right point in the window when it's told to do so. In Chrome and Safari, however, the call to scrollTop() apparently does nothing at all. All the numbers are OK, and the target refers to the right thing (and the offsetParent() is indeed the body element), but nothing at all happens. As far as I can tell from googling around, this is supposed to work. Is there something funny about the renderer under Safari and Chrome? This is jQuery 1.3.2 if that matters. Test page: http://gutfullofbeer.net/scrolltop.html

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  • SQL SERVER – SHRINKFILE and TRUNCATE Log File in SQL Server 2008

    - by pinaldave
    Note: Please read the complete post before taking any actions. This blog post would discuss SHRINKFILE and TRUNCATE Log File. The script mentioned in the email received from reader contains the following questionable code: “Hi Pinal, If you could remember, I and my manager met you at TechEd in Bangalore. We just upgraded to SQL Server 2008. One of our jobs failed as it was using the following code. The error was: Msg 155, Level 15, State 1, Line 1 ‘TRUNCATE_ONLY’ is not a recognized BACKUP option. The code was: DBCC SHRINKFILE(TestDBLog, 1) BACKUP LOG TestDB WITH TRUNCATE_ONLY DBCC SHRINKFILE(TestDBLog, 1) GO I have modified that code to subsequent code and it works fine. But, are there other suggestions you have at the moment? USE [master] GO ALTER DATABASE [TestDb] SET RECOVERY SIMPLE WITH NO_WAIT DBCC SHRINKFILE(TestDbLog, 1) ALTER DATABASE [TestDb] SET RECOVERY FULL WITH NO_WAIT GO Configuration of our server and system is as follows: [Removed not relevant data]“ An email like this that suddenly pops out in early morning is alarming email. Because I am a dead, busy mind, so I had only one min to reply. I wrote down quickly the following note. (As I said, it was a single-minute email so it is not completely accurate). Here is that quick email shared with all of you. “Hi Mr. DBA [removed the name] Thanks for your email. I suggest you stop this practice. There are many issues included here, but I would list two major issues: 1) From the setting database to simple recovery, shrinking the file and once again setting in full recovery, you are in fact losing your valuable log data and will be not able to restore point in time. Not only that, you will also not able to use subsequent log files. 2) Shrinking file or database adds fragmentation. There are a lot of things you can do. First, start taking proper log backup using following command instead of truncating them and losing them frequently. BACKUP LOG [TestDb] TO  DISK = N'C:\Backup\TestDb.bak' GO Remove the code of SHRINKING the file. If you are taking proper log backups, your log file usually (again usually, special cases are excluded) do not grow very big. There are so many things to add here, but you can call me on my [phone number]. Before you call me, I suggest for accuracy you read Paul Randel‘s two posts here and here and Brent Ozar‘s Post here. Kind Regards, Pinal Dave” I guess this post is very much clear to you. Please leave your comments here. As mentioned, this is a very huge subject; I have just touched a tip of the ice-berg and have tried to point to authentic knowledge. Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: Pinal Dave, SQL, SQL Authority, SQL Backup and Restore, SQL Data Storage, SQL Query, SQL Scripts, SQL Server, SQL Tips and Tricks, T SQL, Technology

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  • Diamond square algorithm.

    - by Gabriel A. Zorrilla
    I'm trying to write the Diamond-Square algorithm in Java to generate a random map but can't figure out the implementation... Anyone with some Java code (or other language) so i can check how the loop is made would be greatly appreciated! Thanks!

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  • Vim with split frame of buffers or file listing

    - by casualcoder
    Similar in appearance to Vim as a note taking platform (SO), I would like a pane with a list of open buffers that can be used as a jump to list. This is one feature in many IDEs and other advanced editors that is missing. Having a dozen buffers or so open becomes confusing as to which buffer is where.

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