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• [Zend Framework] Forms and success output

  - by rasouza

  Well, It's a beginer's question but I really don't know what is the best way. I have a basic CRUD (Create, Retrieve, Update and Delete) in my project and I'd like to output some message if succeded or not in a div inside the same page. So, basically, I have a form which action is setted to the same page and I have a div #statusDiv below this same form which I'd like to output something like Register included with success. What is the best way for doing this? Set a flag in the controller $this->view->flagStatus = 'message' then call it in the view? Just to make it more clear. It's my code: //IndexController.php indexAction() ... //Check if there's submitted data if ($this->getRequest()->isPost()) { ... $registries->insert($data); $this->view->flagStatus = 'message'; $this->_redirect('/'); } Then my view: .... <?php if ($this->flagStatus) { ?> <div id="divStatus" class="success span-5" style="display: none;"> <?php echo $this->flagStatus; ?> </div> <?php } ?> ....

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• C vs C++ function questions

  - by james

  I am learning C, and after starting out learning C++ as my first compiled language, I decided to "go back to basics" and learn C. There are two questions that I have concerning the ways each language deals with functions. Firstly, why does C "not care" about the scope that functions are defined in, whereas C++ does? For example, int main() { donothing(); return 0; } void donothing() { } the above will not compile in a C++ compiler, whereas it will compile in a C compiler. Why is this? Isn't C++ mostly just an extension on C, and should be mostly "backward compatible"? Secondly, the book that I found (Link to pdf) does not seem to state a return type for the main function. I check around and found other books and websites and these also commonly do not specify return types for the main function. If I try to compile a program that does not specify a return type for main, it compiles fine (although with some warnings) in a C compiler, but it doesn't compile in a C++ compiler. Again, why is that? Is it better style to always specify the return type as an integer rather than leaving it out? Thanks for any help, and just as a side note, if anyone can suggest a better book that I should buy that would be great!

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• Weird send() problem (with Wireshark log)

  - by Meta

  I had another question about this issue, but I didn't ask properly, so here I go again! I'm sending a file by sending it in chunks. Right now, I'm playing around with different numbers for the size of that chunk, to see what size is the most efficient. When testing on the localhost, any chunk size seems to work fine. But when I tested it over the network, it seems like the maximum chunk size is 8191 bytes. If I try anything higher, the transfer becomes extremely, painfully, slow. To show what happens, here are the first 100 lines of Wireshark logs when I use a chunk size of 8191 bytes, and when I use a chunk size of 8192 bytes: (the sender is 192.168.0.102, and the receiver is 192.168.0.100) 8191: http://pastebin.com/E7jFFY4p 8192: http://pastebin.com/9P2rYa1p Notice how in the 8192 log, on line 33, the receiver takes a long time to ACK the data. This happens again on line 103 and line 132. I believe this delay is the root of the problem. Note that I have not modified the SO_SNDBUF option nor the TCP_NODELAY option. So my question is, why am I getting delayed ACKs when sending files in chunks of 8192 bytes, when everything works fine when using chunks of 8191 bytes? Edit: As an experiment, I tried to do the file transfer in the other direction (from 192.168.0.100 to 192.168.0.102), and surprisingly, any number worked! (Although numbers around 8000 seemed to perform the smoothest). So then the problem is with my computer! But I'm really not sure what to check for. Edit 2: Here is the pseudocode I use to send and receive data.

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• Fastest method to define whether a number is a triangular number

  - by psihodelia

  A triangular number is the sum of the n natural numbers from 1 to n. What is the fastest method to find whether a given positive integer number is a triangular one? I suppose, there must be a hidden pattern in a binary representation of such numbers (like if you need to find whether a number is even/odd you check its least significant bit). Here is a cut of the first 1200th up to 1300th triangular numbers, you can easily see a bit-pattern here (if not, try to zoom out): (720600, '10101111111011011000') (721801, '10110000001110001001') (723003, '10110000100000111011') (724206, '10110000110011101110') (725410, '10110001000110100010') (726615, '10110001011001010111') (727821, '10110001101100001101') (729028, '10110001111111000100') (730236, '10110010010001111100') (731445, '10110010100100110101') (732655, '10110010110111101111') (733866, '10110011001010101010') (735078, '10110011011101100110') (736291, '10110011110000100011') (737505, '10110100000011100001') (738720, '10110100010110100000') (739936, '10110100101001100000') (741153, '10110100111100100001') (742371, '10110101001111100011') (743590, '10110101100010100110') (744810, '10110101110101101010') (746031, '10110110001000101111') (747253, '10110110011011110101') (748476, '10110110101110111100') (749700, '10110111000010000100') (750925, '10110111010101001101') (752151, '10110111101000010111') (753378, '10110111111011100010') (754606, '10111000001110101110') (755835, '10111000100001111011') (757065, '10111000110101001001') (758296, '10111001001000011000') (759528, '10111001011011101000') (760761, '10111001101110111001') (761995, '10111010000010001011') (763230, '10111010010101011110') (764466, '10111010101000110010') (765703, '10111010111100000111') (766941, '10111011001111011101') (768180, '10111011100010110100') (769420, '10111011110110001100') (770661, '10111100001001100101') (771903, '10111100011100111111') (773146, '10111100110000011010') (774390, '10111101000011110110') (775635, '10111101010111010011') (776881, '10111101101010110001') (778128, '10111101111110010000') (779376, '10111110010001110000') (780625, '10111110100101010001') (781875, '10111110111000110011') (783126, '10111111001100010110') (784378, '10111111011111111010') (785631, '10111111110011011111') (786885, '11000000000111000101') (788140, '11000000011010101100') (789396, '11000000101110010100') (790653, '11000001000001111101') (791911, '11000001010101100111') (793170, '11000001101001010010') (794430, '11000001111100111110') (795691, '11000010010000101011') (796953, '11000010100100011001') (798216, '11000010111000001000') (799480, '11000011001011111000') (800745, '11000011011111101001') (802011, '11000011110011011011') (803278, '11000100000111001110') (804546, '11000100011011000010') (805815, '11000100101110110111') (807085, '11000101000010101101') (808356, '11000101010110100100') (809628, '11000101101010011100') (810901, '11000101111110010101') (812175, '11000110010010001111') (813450, '11000110100110001010') (814726, '11000110111010000110') (816003, '11000111001110000011') (817281, '11000111100010000001') (818560, '11000111110110000000') (819840, '11001000001010000000') (821121, '11001000011110000001') (822403, '11001000110010000011') (823686, '11001001000110000110') (824970, '11001001011010001010') (826255, '11001001101110001111') (827541, '11001010000010010101') (828828, '11001010010110011100') (830116, '11001010101010100100') (831405, '11001010111110101101') (832695, '11001011010010110111') (833986, '11001011100111000010') (835278, '11001011111011001110') (836571, '11001100001111011011') (837865, '11001100100011101001') (839160, '11001100110111111000') (840456, '11001101001100001000') (841753, '11001101100000011001') (843051, '11001101110100101011') (844350, '11001110001000111110') For example, can you also see a rotated normal distribution curve, represented by zeros between 807085 and 831405?

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• How to get an error message out of my webpage

  - by Vaccano

  I have a web page that when I run it on a remote computer I get the message saying that remote errors cannot be viewed When I go to view it on my web server machine, I get a message saying: Internet Explorer cannot display the webpage • Most likely causes: • You are not connected to the Internet. • The website is encountering problems. • There might be a typing error in the address. What you can try: Check your Internet connection. Try visiting another website to make sure you are connected. Retype the address. Go back to the previous page. I can get to google fine, so it is not the internet connection.... But this message gives me nothing to work on. How can I get more info as to why my page is not working? I tried going to IIS Mananger and right clicking on the site and selecting browse. But my site is an HTTPS site so that does not work. Any ideas would be great.

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• Reverse wildcard search in codeigniter

  - by Andy Platt

  I am implementing a snippet-based content management system into my current project. Snippets can be associated with a page either by exact match of the full url falling back to a wildcard match on a partial url or finally a default snippet. To implement this I have a created table of page associations with a wildcard flag, the system first checks the current url against the non-wildcard associations and if it doesn't find a match it checks against the partial url's where the wildcard flag is set. In order to achieve this I am getting all the partial url's from the database and putting them into an array then walking the array to check for a match against the current url: protected function _check_wildcard($url = NULL) { if($url) { $q = $this->db->where('wildcard' ,'Y') ->from('content') ->get(); $wildcards = $q->result_array(); foreach($wildcards AS $wildcard) { if(strpos($url,$wildcard['url']) > 0) { return $wildcard['snipppet_id']; } } } else { return NULL; } } Can anyone suggest a better way to do this - preferably one that doesn't involve having to constantly download the full list of all the wildcards each time I load a page as I am afraid that this will have a negative effect on the scalability of the system down the line?

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• Virtualmin - Domain / Subdomain confusion

  - by Dan

  Hi, I've just purchased a new VPS and setup Virtualmin on it. I pointed my domain at the IP of the server and set up a new virtual server through Virtualmin. I uploaded a simple php script to check it was working and it seemed to be fine. I then created a subserver and also pointed test.mydomain.com to my IP, with the intension of having mydomain.com and test.mydomain.com both pointing to different directories on my VPS. However, once I added the subserver, I received a 403 Forbidden message if I tried to access either the new subdomain OR the existing site. I uploaded a similar php script to the subfolder and it then displayed correctly. However, I now get sent to the same script regardless of what URL I type in. I did try posting this message on the Virtualmin forum, but their filters picked it up as spam and wouldn't allow it. Can anyone help me? I'm sure it's just something simple, but this is driving me crazy! Any advice appreciated. Thanks.

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• PHP SDK Requires two logins...doesn't recognize first

  - by Jay Konieczny

  I am using the following code to authenticate whether users are logged in or not. While users can log in, they have to click the login button twice. Additionally, sometimes even after they click the log-in button twice, my "user info" part of the page (earlier in the page than the content) shows them as logged out while the actual page shows them as logged in. Here is the code. Could someone suggest a better way of handling log-ins? function isLoggedIn($facebook) { if (isset($facebook) and $facebook->getUser() != 0) { // UserID exists, but user may still not be logged in. Let's check: try { $facebook->api('/me', 'GET'); // If this succeeds, then they are logged in. return true; } catch(FacebookApiException $e) { // Some kind of error, so not logged in. if(session_id() === '') session_destroy(); return false; } } else { if(session_id() === '') session_destroy(); return false; } } Thanks!

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• [SOLVED]Django - Passing variables to template based on db

  - by George 'Griffin

  I am trying to add a feature to my app that would allow me to enable/disable the "Call Me" button based on whether or not I am at [home|the office]. I created a model in the database called setting, it looks like this: class setting(models.Model): key = models.CharField(max_length=200) value = models.CharField(max_length=200) Pretty simple. There is currently one row, available, the value of it is the string True. I want to be able to transparently pass variables to the templates like this: {% if available %} <!-- Display button --> {% else %} <!-- Display grayed out button --> {% endif %} Now, I could add logic to every view that would check the database, and pass the variable to the template, but I am trying to stay DRY. What is the best way to do this? UPDATE I created a context processor, and added it's path to the TEMPLATE_CONTEXT_PROCESSORS, but it is not being passed to the template def available(request): available = Setting.objects.get(key="available") if open.value == "True": return {"available":True} else: return {} UPDATE TWO If you are using the shortcut render_to_response, you need to pass an instance of RequestContext to the function. from the django documentation: If you're using Django's render_to_response() shortcut to populate a template with the contents of a dictionary, your template will be passed a Context instance by default (not a RequestContext). To use a RequestContext in your template rendering, pass an optional third argument to render_to_response(): a RequestContext instance. Your code might look like this: def some_view(request): # ... return render_to_response('my_template.html', my_data_dictionary, context_instance=RequestContext(request)) Many thanks for all the help!

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• Error with `Thread.Sleep` during automatic testing on TeamCity 5

  - by yeyeyerman

  Hello, I'm having some problems executing the tests of the application I'm developing. All the tests execute normally with ReSharper and in NCover. However, the execution of one of these tests in TeamCity is generating an error. This test initializes two objects, the object under test and a simulator of a real object. Both objects will communicate throug a serial link in a representation of the real scenario. ObjectSimulator r_simulator = new ObjectSimulator(...); ObjectDriver r_driver = new ObjectDriver(...); Assert.IsTrue(r_driver.Connect() == ErrorCode.Success); The simulator just do the following in the constructor public class ObjectSimulator { ... public ObjectSimulator() { // serial port configuration m_port = new SerialPort(); m_port.DataReceived += DataReceivedEvent; } ... } The main object has two threads. The main thread of the application and a timer to refresh a watchdog timer in the real object. public ErrorCode Connect() { ... StartSynchroTimer(); Thread.Sleep(4); // to check if the timer is working properly ... } The problem seems to be comming from the Thread.Sleep() call, as when I remove it everything works. The ObjectSimulator somehow doesn't execute the DataReceived event callback. How can I resolve this issue?

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• generate k distinct number less then n

  - by davit-datuashvili

  hi i have following question task is this generate k distinct positive numbers less then n without duplication my method is following first create array size of k where we should write these numbers int a[]=new int[k]; //now i am going to cretae another array where i check if (at given number position is 1 then generate number again else put this number in a array and continue cycle i put here a piece of code and explanations int a[]=new int[k]; int t[]=new int[n+1]; Random r=new Random(); for (int i==0;i<t.length;i++){ t[i]=0;//initialize it to zero } int m=0;//initialize it also for (int i=0;i<a.length;i++){ m=r.nextInt(n);//random element between 0 and n if (t[m]==1){ //i have problem with this i want in case of duplication element occurs repeats this steps afain until there will be different number else{ t[m]=1; x[i]=m; } } so i fill concret my problem if t[m]==1 it means that this element occurs already so i want to generate new number but problem is that number of generated numbers will not be k beacuse if i==0 and occurs duplicate element and we write continue then it will switch at i==1 i need like goto for repeat step or for (int i=0;i<x.length;i++){ loop: m=r.nextInt(n); if ( x[m]==1){ continue loop; } else{ x[m]=1; a[i]=m; continue;//continue next step at i=1 and so on } } i need this code in java please help

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• Is it possible in SQLAlchemy to filter by a database function or stored procedure?

  - by Rico Suave

  We're using SQLalchemy in a project with a legacy database. The database has functions/stored procedures. In the past we used raw SQL and we could use these functions as filters in our queries. I would like to do the same for SQLAlchemy queries if possible. I have read about the @hybrid_property, but some of these functions need one or more parameters, for example; I have a User model that has a JOIN to a bunch of historical records. These historical records for this user, have a date and a debit and credit field, so we can look up the balance of a user at a specific point in time, by doing a SUM(credit) - SUM(debit) up until the given date. We have a database function for that called dbo.Balance(user_id, date_time). I can use this to check the balance of a user at a given point in time. I would like to use this as a criterium in a query, to select only users that have a negative balance at a specific date/time. selection = users.filter(coalesce(Users.status, 0) == 1, coalesce(Users.no_reminders, 0) == 0, dbo.pplBalance(Users.user_id, datetime.datetime.now()) < -0.01).all() This is of course a non-working example, just for you to get the gist of what I'd like to do. The solution looks to be to use hybrd properties, but as I mentioned above, these only work without parameters (as they are properties, not methods). Any suggestions on how to implement something like this (if it's even possible) are welcome. Thanks,

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• Ways to prevent multiple email notification with php&mysql

  - by Louis Loudog Trottier

  My 1st post, but i got many great answers and tips from stackoverflow so far. This one was a close call- How does facebook, gmail send the real time notification? but not exactly, so let brainstorm this together. I have CMS system with mail notification when a change is made on the site. Everything wotk very well but i want to prevent multiple notification if somene make another quick change to, let say, fix a typo. Using php mail(), obviously. I've tough of 2 ways, one simple, and one.... let just say, pretty heavy... cough. the 3rd one was inspired by Implementing Email Notification but really doesn't look appealing to me to send bunch of email at once. Use a timestamp to check if another change was made in the 'let say' last 5 minutes. Record the last change, and compare it to the new one. Could be usefull for backup at the same time since i'll have to save the change somewhere, but text can be long and making an sql search would be painfull. Wouldn't it? Use cron to send changes every x minutes... convince me if you ythink it is a suitable solution. Any ideas, comment or suggestion of your own? Looking forward for your inputs, and since i now registered, i'll do my best to help around. Cheers, all llt

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• Battery life if using GPS and background program

  - by StealthRT

  I was wondering if anyone has created an app that starts in the background and utilizes the GPS to gather the current Lat and Long every minute or so? If you have, would you please provide your battery times? As in, how long does your phone last until its all out of juice from just running that background app with standard cell phone programs. I'm trying to see if it would be worth the time to create an app for myself but if i work for 8 hours and dont have a way of charging my phone during that time then i dont want to be going home and it shut down on me since my app i would create works at my house. I need the app to work since it will see when i am in range of my home (from the GPS) and then send commands to my server at the house from my phone. So thats why it would need to be able to stay in the background doing a check every 1 minute or so. Or only turn on the GPS (Is is doable with iOS? & Android?) whenever its after 5pm each day so that it will minimize the load on the battery?!? Any help or suggestions would be great! Thanks!

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• How does a java compiler resolve a non-imported name

  - by gexicide

  Consider I use a type X in my java compilation unit from package foo.bar and X is not defined in the compilation unit itself nor is it directly imported. How does a java compiler resolve X now efficiently? There are a few possibilities where X could reside: X might be imported via a star import a.b.* X might reside in the same package as the compilation unit X might be a language type, i.e. reside in java.lang The problem I see is especially (2.). Since X might be a package-private type, it is not even required that X resides in a compilation unit that is named X.java. Thus, the compiler must look into all entries of the class path and search for any classes in a package foo.bar, it then must read every class that is in package foo.bar to check whether X is included. That sounds very expensive. Especially when I compile only a single file, the compiler has to read dozens of class files only to find a type X. If I use a lot of star imports, this procedure has to be repeated for a lot of types (although class files won't be read twice, of course). So is it advisable to import also types from the same package to speed up the compilation process? Or is there a faster method for resolving an unimported type X which I was not able to find?

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• Mystery: How does Google do cross-domain iframe communication?

  - by Shraga

  Hi everyone, When you host Googles web search element on a page, a div is created which incorporates an iframe which points to a Google adsense ads page. However, if there are no ads for the specific query, Google somehow changes the class on YOUR domain to render the div (and iframe) invisible. They are NOT using postMessage, as it also works in IE7. They are also not using the fragment identifier method, as no hash appears in the url. So how do they do it? To check what I'm saying just put the following into a regular html page: <!-- Google Custom Search Element --> <div id="cse" style="width:100%;">Loading</div> <script src="http://www.google.com/jsapi" type="text/javascript"></script> <script type="text/javascript"> google.load('search', '1'); google.setOnLoadCallback(function(){ new google.search.CustomSearchControl().draw('cse'); }, true); </script> and then do a search for "cars" (or anything else that will definitely have ads) and then for "wzxv", which has no ads...

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• Joomla User Login Question

  - by user277127

  I would like to enable users of my existing web app to login to Joomla with the credentials already stored in my web app's database. By using the Joomla 1.5 authentication plugin system -- http://docs.joomla.org/Tutorial:Creating_an_Authentication_Plugin_for_Joomla_1.5 -- I would like to bypass the Joomla registration process and bypass creating users in the Joomla database altogether. My thought had been that I could simply populate a User object, which would be stored in the Session, and that this would replace the need to store a user in the Joomla database. After looking through the code surrounding user management in Joomla, it seems like any time you interact with the User object, the database is being queried. It therefore seems like my initial idea won't work. Is that right? It looks like, in order to achieve the effect I want, I will have to actually register a user from within the authentication plugin at the time they first login. This is not ideal, so before I go forward with it, I wanted to check with Joomla developers whether it is possible to do what I described above. Thanks in advance -- I am new to Joomla and greatly appreciate your help!

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• Displaying Query Results Horizontally

  - by AndyD273

  I am wondering if it is possible to take the results of a query and return them as a CSV string instead of as a column of cells. Basically, we have a table called Customers, and we have a table called CustomerTypeLines, and each Customer can have multiple CustomerTypeLines. When I run a query against it, I run into problems when I want to check multiple types, for instance: Select * from Customers a Inner Join CustomerTypeLines b on a.CustomerID = b.CustomerID where b.CustomerTypeID = 14 and b.CustomerTypeID = 66 ...returns nothing because a customer can't have both on the same line, obviously. In order to make it work, I had to add a field to Customers called CustomerTypes that looks like ,14,66,67, so I can do a Where a.CustomerTypes like '%,14,%' and a.CustomerTypes like '%,66,%' which returns 85 rows. Of course this is a pain because I have to make my program rebuild this field for that Customer each time the CustomerTypeLines table is changed. It would be nice if I could do a sub query in my where that would do the work for me, so instead of returning the results like: 14 66 67 it would return them like ,14,66,67, Is this possible?

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• Javascript for disabling dropdown in ASP.NET

  - by Lijo

  Hi Team, I am using JScript in ASP.NET 2005. I have a page with a checkbox and a dropdown list. When the checkbox is checked the dropdown is to be disabled. During Postback of the page this should be retained. I am using a javascript function as follows if((chkOwner[1].checked==true)) { document.getElementById(ddlClientID).disabled=true; document.getElementById(ddlClientID).className = "form-disabled"; document.getElementById(ddlClientID).selectedIndex = 0; } else { document.getElementById(ddlClientID).disabled=false; document.getElementById(ddlClientID).className = "form-input"; document.getElementById(ddlClientID).selectedIndex = 0; } This works, almost. However, the dropdown selection is not retained after postback (when checkbox is not selected). Apprently the solution is to remove the last line, i.e, in the else part, remove the selectedIndex =0 setting. But, when I do that the disabling of dropdown (when check box is selected) is not working after post back. Could you please help on this? Thanks Lijo

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• Win conditions for a connect-4 like game

  - by FrozenWasteland

  I have an 5x10 array that is populated with random values 1-5. I want to be able to check when 3 numbers, either horizontally, or vertically, match. I can't figure out a way to do this without writing a ton of if statements. Here is the code for the randomly populated array int i; int rowincrement = 10; int row = 0; int col = 5; int board[10][5]; int randomnum = 5; int main(int argc, char * argv[]) { srand(time(NULL)); cout << "============\n"; while(row < rowincrement) { for(i = 0; i < 5; i++) { board[row][col] = rand()%5 + 1; cout << board[row][col] << " "; } cout << endl; cout << "============\n"; row++; } cout << endl; return 0; }

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• I can not navigate to the next page in windows phone 7

  - by Vijay

  I am trying to navigate form one page to another page depends upon the login. If already user logged in, Welcome page should open. Else Log in Page should open. I am trying like this. The Splash Page is the start up page. This is a Splash Screen Xaml.cs: namespace NewExample.Views { public partial class SplashPage : PhoneApplicationPage { public SplashPage() { InitializeComponent(); this.DataContext = new SplashPageViewModel(); } } } This is Splash Screen View Model: Here I am check the user already logged in or not. namespace NewExample.ViewModel { public class SplashPageViewModel { public static bool isLogin = false; public SplashPageViewModel() { var rootFrame = (App.Current as App).RootFrame; if (isLogin) rootFrame.Navigate(new Uri("/Views/WelcomePage.xaml", UriKind.Relative)); else rootFrame.Navigate(new Uri("/Views/LoginPage.xaml", UriKind.Relative)); } } } But it is not working. The Splash Page only showing. This is not navigating to another page. Please help me to resolve this problem.

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• Given a 2d array sorted in increasing order from left to right and top to bottom, what is the best w

  - by Phukab

  I was recently given this interview question and I'm curious what a good solution to it would be. Say I'm given a 2d array where all the numbers in the array are in increasing order from left to right and top to bottom. What is the best way to search and determine if a target number is in the array? Now, my first inclination is to utilize a binary search since my data is sorted. I can determine if a number is in a single row in O(log N) time. However, it is the 2 directions that throw me off. Another solution I could use, if I could be sure the matrix is n x n, is to start at the middle. If the middle value is less than my target, then I can be sure it is in the left square portion of the matrix from the middle. I then move diagnally and check again, reducing the size of the square that the target could potentially be in until I have honed in on the target number. Does anyone have any good ideas on solving this problem? Example array: Sorted left to right, top to bottom. 1 2 4 5 6 2 3 5 7 8 4 6 8 9 10 5 8 9 10 11

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• memcached: which is faster, doing an add (and checking result), or doing a get (and set when returni

  - by Mike Sherov

  The title of this question isn't so clear, but the code and question is straightforward. Let's say I want to show my users an ad once per day. To accomplish this, every time they visit a page on my site, I check to see if a certain memcache key has any data stored on it. If so, don't show an ad. If not, store the value '1' in that key with an expiration of 86400. I can do this 2 ways: //version a $key='OPD_'.date('Ymd').'_'.$type.'_'.$user; if($memcache->get($key)===false){ $memcache->set($key,'1',false,$expire); //show ad } //version b $key='OPD_'.date('Ymd').'_'.$type.'_'.$user; if($memcache->add($key,'1',false,$expire)){ //show ad } Now, it might seem obvious that b is better, it always makes 1 memcache call. However, what is the overhead of "add" vs. "get"? These aren't the real comparisons... and I just made up these numbers, but let's say 1 add ~= 1 set ~= 5 get in terms of effort, and the average user views 5 pages a day: a: (5 get * 1 effort) + (1 set * 5 effort) = 10 units of effort b: (5 add * 5 effort) = 25 units of effort Would it make sense to always do the add call? Is this an unnecessary micro-optimization?

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• Singletons and constants

  - by devoured elysium

  I am making a program which makes use of a couple of constants. At first, each time I needed to use a constant, I'd define it as //C# private static readonly int MyConstant = xxx; //Java private static final int MyConstant = xxx; in the class where I'd need it. After some time, I started to realise that some constants would be needed in more than one class. At this time, I had 3 choises: To define them in the different classes that needed it. This leads to repetition. If by some reason later I need to change one of them, I'd have to check in all classes to replace them everywhere. To define a static class/singleton with all the constants as public. If I needed a constant X in ClassA, ClassB and ClassC, I could just define it in ClassA as public, and then have ClassB and ClassC refer to them. This solution doesn't seem that good to me as it introduces even more dependencies as the classes already have between them. I ended up implementing my code with the second option. Is that the best alternative? I feel I am probably missing some other better alternative. What worries me about using the singleton here is that it is nowhere clear to a user of the class that this class is using the singleton. Maybe I could create a ConstantsClass that held all the constants needed and then I'd pass it in the constructor to the classes that'd need it? Thanks

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• Multiple locking task (threading)

  - by Archeg

  I need to implement the class that should perform locking mechanism in our framework. We have several threads and they are numbered 0,1,2,3.... We have a static class called ResourceHandler, that should lock these threads on given objects. The requirement is that n Lock() invokes should be realeased by m Release() invokes, where n = [0..] and m = [0..]. So no matter how many locks was performed on single object, only one Release call is enough to unlock all. Even further if o object is not locked, Release call should perform nothing. Also we need to know what objects are locked on what threads. I have this implementation: public class ResourceHandler { private readonly Dictionary<int, List<object>> _locks = new Dictionary<int, List<object>>(); public static ResourceHandler Instance {/* Singleton */} public virtual void Lock(int threadNumber, object obj) { Monitor.Enter(obj); if (!_locks.ContainsKey(threadNumber)) {_locks.Add(new List<object>());} _locks[threadNumber].Add(obj); } public virtual void Release(int threadNumber, object obj) { // Check whether we have threadN in _lock and skip if not var count = _locks[threadNumber].Count(x => x == obj); _locks[threadNumber].RemoveAll(x => x == obj); for (int i=0; i<count; i++) { Monitor.Exit(obj); } } // ..... } Actually what I am worried here about is thread-safety. I'm actually not sure, is it thread-safe or not, and it's a real pain to fix that. Am I doing the task correctly and how can I ensure that this is thread-safe?

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