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  • Do preconditions ALWAYS have to be checked?

    - by Pin
    These days I'm used to checking every single precondition for every function since I got the habit from an OS programming course back at uni. On the other hand, at the software engineering course we were taught that a common precondition should only be checked once, so for example, if a function is delegating to another function, the first function should check them but checking them again in the second one is redundant. I do see the redundancy point, but I certainly feel it's safer to always check them, plus you don't have to keep track of where they were checked previously. What's the best practice here?

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  • SQL Server Replication

    - by Serge
    I have a device that continuously collects data and stores it on a local database. I would like to also replicate that data to a second computer over the network every 10 seconds to ensure data reliability. Should I use transaction replication to achieve this? What if the network connection is temporarily unavailable, will the replication service automatically transmit all the backlogged data once the connection is restored? Can the computer that collects the data be SQL Server Compact or does it have to be at least Workgroup edition to be a Publisher. The second PC will run SQL Server Express and would be a subscriber. Thanks.

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  • How to address thread-safety of service data used for maintaining static local variables in C++?

    - by sharptooth
    Consider the following scenario. We have a C++ function with a static local variable: void function() { static int variable = obtain(); //blahblablah } the function needs to be called from multiple threads concurrently, so we add a critical section to avoid concurrent access to the static local: void functionThreadSafe() { CriticalSectionLockClass lock( criticalSection ); static int variable = obtain(); //blahblablah } but will this be enough? I mean there's some magic that makes the variable being initialized no more than once. So there's some service data maintained by the runtime that indicates whether each static local has already been initialized. Will the critical section in the above code protect that service data as well? Is any extra protection required for this scenario?

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  • Restrict confirm message on page reload with f5

    - by Max
    In my JSP page I am using post method while submitting the page. So once I go from Page 1 to page 2. In Page 2, If I press F5 I am getting alert as "To display this page, Firefox must send information that will repeat any action (such as a search or order confirmation) that was performed earlier." I knew this question is a bit sarcastic but please give me an Idea. I can't change my method from POST to GET because I need to send large amount of data. Thanks in advance... Edited: In my Page1.JSP I call onClick function in that function I call action as "/page2servlet.do". Now, In Java side I use Spring Framework. With MVC Object I return to page2.jsp. So where do the response.sendRedirect Fit.

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  • Configure WCF Service Behavior using database

    - by Achhar
    We use database to centralize our configuration. As part of it, I want to store the standard service behaviors configuration like expose service metatdata, service debug, service throttling for a service inside database rather than in web/app.config. I was planing to store the configuration for a behavior in database as XML. For e.g. <serviceDebug includeExceptionDetailsinFault=true / What I am struggling with is once I read this XML from database how do I create ServiceDebugBehavior instance from it and apply it to my service host? I have tried using XML Serializer but didn't had success. Any thoughts on how this could be achieved or any alternate solutions?

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  • How do stop form posting to mysql if database contains a specific ID?

    - by user342391
    I have a form that I am using to post data to mysql. Before submitting the form I want to check the database and see if there are any fields in the column 'customerid' that equal 'userid' and if so not to post the form. Basically, I am trying to limit my users from posting more than once. Users will be able to login to my system and make ONE post. They will be able to delete and modify their post but are only limited to one post. How would I do this??? Code so far: <?php include '../login/dbc.php'; page_protect(); $userid = $_SESSION['user_id']; $sql="INSERT INTO content (customerid, weburl, title, description) VALUES ('$_POST[userid]','$_POST[webaddress]','$_POST[pagetitle]','$_POST[pagedescription]')"; if (!mysql_query($sql)) { die('Error: ' . mysql_error()); } echo "1 record added"; ?>

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  • What does -setPropagatesDeletesAtEndOfEvent: actually do?

    - by dontWatchMyProfile
    Let me try it: If I don't set this, then the default value is YES. So when I delete an managed object from the context, the context propagates this immediately to the persistent store so the object is gone? And when I set this to NO, then objects are deleted from the persistent store only when calling -save? Is that really true? I mean: If it was true, then the default behavior is that once you call the context to delete an object, the object is gone. Lets assume you're not using an undo manager. So... gone. Right? No rollback possible? Or can it still be recovered with a rollback?

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  • C# Object Array CopyTo links both arrays' values?

    - by Dutchie432
    Okay, I have what I think is a simple question.. or just a case of me being a C# beginner. I have an array of custom objects (clsScriptItem) that I am populating from a database. Once the items are loaded, I want to back them up to "backup" array so I can revert the information back after changing the main array. However, when I use CopyTo to copy the array and then alter the original array, the backup array is also being altered... I though CopyTo merely copied values + structure from one array to another. private void backupItems() { lastSavedItems = new clsScriptItem[items.Length]; items.CopyTo(lastSavedItems, 0); //items[0].nexts[0] is 2 //lastSavedItems[0].nexts[0] is 2 items[0].nexts[0] = "-1"; //items[0].nexts[0] is -1 //lastSavedItems[0].nexts[0] is also -1 } How do I backup this data without having the two arrays be 'linked'??

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  • Communication between c++ objects.

    - by Pradyot
    This is an issue, that I have come acrosss earlier. Basically a c++ object has a member object that does some work, once the work is done , a notification needs to made to the parent. What is the most elegant solution to allow this communication. Does being in this position indicate a flaw with the design to begin with? To elaborate. class A { B member; void do_something(); } class B{ void talk_to_network(); }; void do_something() { //Conditional wait on a variable that will change when talk to network completes. //So need a way for B to inform A, that it is done. }

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  • Iterate over the lines of a string

    - by Space_C0wb0y
    I have a multi-line string defined like this: foo = """ this is a multi-line string. """ I need an iterator that iterates over the individual lines of that string. I could of course do it like this: lineiterator = iter(foo.splitlines()) Is there a more direct way of doing this? In this scenario the string has to traversed once for the splitting, and then again by the parser. It doesn't matter in my test-case, since the string is very short there, I am just asking out of curiosity. Python has so many useful and efficient built-ins for such stuff, but I could find nothing that suits this need.

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  • Why is writeSTRef faster than if expression?

    - by wenlong
    writeSTRef twice for each iteration fib3 :: Int -> Integer fib3 n = runST $ do a <- newSTRef 1 b <- newSTRef 1 replicateM_ (n-1) $ do !a' <- readSTRef a !b' <- readSTRef b writeSTRef a b' writeSTRef b $! a'+b' readSTRef b writeSTRef once for each iteration fib4 :: Int -> Integer fib4 n = runST $ do a <- newSTRef 1 b <- newSTRef 1 replicateM_ (n-1) $ do !a' <- readSTRef a !b' <- readSTRef b if a' > b' then writeSTRef b $! a'+b' else writeSTRef a $! a'+b' a'' <- readSTRef a b'' <- readSTRef b if a'' > b'' then return a'' else return b'' Benchmark, given n = 20000: benchmarking 20000/fib3 mean: 5.073608 ms, lb 5.071842 ms, ub 5.075466 ms, ci 0.950 std dev: 9.284321 us, lb 8.119454 us, ub 10.78107 us, ci 0.950 benchmarking 20000/fib4 mean: 5.384010 ms, lb 5.381876 ms, ub 5.386099 ms, ci 0.950 std dev: 10.85245 us, lb 9.510215 us, ub 12.65554 us, ci 0.950 fib3 is a bit faster than fib4.

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  • How to play an mp3 using fancybox

    - by user2980783
    I am adding fancybox to my page and to display different types of formats. I was able to implement video, text, and images seamlessly but when it doesn't load the audio. Once I click on the audio file on the gallery it opens on a blank page. I am trying to play the track as iframe if possible. Can anyone help with this. Thank you. <a class="hover-wrap" data-fancybox-type="iframe" data-fancybox-group="music" title="Breathin'" href="_include/download/Breathin'.mp3"> <span class="overlay-img"></span> <span class="overlay-img-thumb font-icon-plus"></span> <p class="description"> <span class="title">Song</span> </p> </a>

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  • WMI instrinsic events. Resources

    - by Nickolodeon
    Hi. I subscribe to usb inserted event like this select * FROM __INSTANCECREATIONEVENT WITHIN 3 WHERE TARGETINSTANCE ISA Win32_DiskDrive After inserting usb flash it blinks every 3 seconds. This is polling interval and intrinsic events work by polling object that's in query. Now, we know these types of events may be resource expensive. (Putting value greater then 3 sometimes chokes these events and client program doesn't get notified). Are there other ways to do that, so that usb doesn't get scanned all the time? May be there some extrinsic events available? Right now the only solution I see is to unsubscribe from event above once it trigerred and resubscribe to it in __INSTANCEDELETIONEVENT handler. Hm, althought deletionevent will also poll diskdrive controllers(

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  • What is wrong with my loop?

    - by user3966541
    I have the following loop and don't understand why it only runs once: std::vector<sf::RectangleShape> shapes; const int res_width = 640; const int res_height = 480; for (int x = 0; x < res_width / 50; x += 50) { for (int y = 0; y < res_height / 50; y += 50) { sf::RectangleShape shape(sf::Vector2f(50, 50)); shape.setPosition(x * 50, y * 50); sf::Color color = (x % 2 == 0) ? sf::Color::Green : sf::Color::Red; shape.setFillColor(sf::Color::Green); shapes.push_back(shape); } }

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  • Problem with $.get while submitting form

    - by bradenkeith
    I'm trying to verify that an Account Name is not already in use once a user fills out a form. The code looks like: $("#add_account").submit( function () { $.get( "'.url::site("ajax/check_account_name").'", {account_name: "t"}, function(data){ alert( data ); }); }); I get a $.get response if the statement sits like this: $(document).ready( function () { $.get( "'.url::site("ajax/check_account_name").'", {account_name: "t"}, function(data){ alert( data ); }); }); Which leads me to believe that my $.get statement is correct. Is there some jQuery rule I'm not familiar with that would cause this to fail in on submit scenario? In code block 1, I get values returned like they should. Block 2 gives me a blank response. Any ideas? Thanks for your time, I know you have better things to be doing.

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  • Is there any difference in the implementation of these three validation methods?

    - by dontWatchMyProfile
    Core Data is calling these methods in certain situations: - (BOOL)validateForInsert:(NSError **)outError; - (BOOL)validateForUpdate:(NSError **)outError; - (BOOL)validateForDelete:(NSError **)outError; I wonder if they're doing anything different, or if they're essentially doing the exact same things. As far as I know, these methods call the -validateValue:forKey:error: method once for every property. The only difference I can imagine is in the .validateForDelete: method. I see no reason why to validate an object when it shall be deleted, except for applying delete rules, probably only in the case of the DENY rule.

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  • How does linq decide between inner & outer joins

    - by user287795
    Hi Usually linq is using an left outer join for its queries but on some cases it decides to use inner join instead. I have a situation where that decision results in wrong results since the second table doesn't always have suitable records and that removes the records from the first table. I'm using a linqdatasource over a dbml where the relevant tables are identical but one holds historical records removed from the first. both have the same primary key. and I'm using a dataloadoption to load both tables at once with out round trips. Would you explain why linq decided to use an inner join here? Thanks

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  • PHP, better to set the variable before if or use if/else?

    - by DssTrainer
    So a simple one that I just never could find a straight answer on. What is better (performance or otherwise): $var = false; If ($a == $b) { $var = true; } or If ($a == $b) { $var = true; } else { $var = false; } I've heard arguments for both ways. I find the first cleaner to ensure I have it set, and a little less code too. The pro being that you may only need to set it once without conditional. But the con being that if the argument is true, it gets set twice. I am assuming the second way is probably best practice

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  • Best way to integrate searching with pagination

    - by Vijay Choudhary
    I have a web application build on cakephp 2.x. I have integrated pagination on my data. Now i want to implement searching on that data also, and pagination should work according to search result. Now my question is: Should i use a form to post my search string. If so, then which method should i use, GET or POST. OR, should i use javascript window.location method, and append the search string to it. If we use this method then search string can append more than once to url. Or any other best way to implement this. Can anybody give the best solution for this as it is a common task for each application to have.

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  • How can I get Facebook Profile image from email?

    - by Forbini
    There's an outlook plugin called Xobni that has a really cool feature, if a contact has an email address, it will fetch that contact's profile picture and display it. Their FAQ states the following: Xobni sends an encrypted email address to Facebook to retrieve the Facebook profile for the person who is currently being viewed in the Xobni sidebar. Your own Facebook profile is never altered by Xobni, and all Facebook privacy settings are strictly followed when viewing other profiles. I'd like to duplicate this functionality. However, I can't figure out which API call they're using. I'm assuming when they say "encrypted email address" that's laymen's terms for the email hash. Once a username is derived, the graph api looks ideal for actually fetching the image, but I'm having trouble going from email hash to profile ID.

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  • Calling Javascript after linking to another page

    - by kratos2488
    I am doing an integration with a support system (Helpstream) and I am currently working on doing some in-app context sensitive help. I have put in a link that will send the user to a section of Helpstream that will allow them to ask a question. Problem is, there are buttons on the page that call Javascript that will bring up a lightbox where the user fills out a form to submit a question. What I need to do is have that form come up after the user goes through the link, so essentially run the Javascript once the user hits the page. The call that I have to implement is NewTopic.CreateNew({type:"Question"}) Any tips would be greatly appreciated. Thanks in advance.

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  • Why does the compiler complain "while expected" when I try to add more code?

    - by user1893578
    Write a program with a word containing @ character as an input. If the word doesn't contain @, it should prompt the user for a word with @. Once a word with @ is read, it should output the word then terminate. This is what I have done so far: public class find { public static void main(String[] args) { System.out.println(" Please enter a word with @ "); Scanner scan = new Scanner(System.in); String bad = "@"; String word = scan.next(); do if (!word.contains(bad)) System.out.println(" Please try again "); else System.out.println(" " + word); while (!word.contains(bad)); } } I can get it to terminate after a word containing "@" is given as input, but if I try to add a Scanner to the line after "please try again", it says while expected.

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  • MySQL UPDATE WHERE IN for each listed value separately?

    - by Tom
    Hi, I've got the following type of SQL: UPDATE photo AS f LEFT JOIN car AS c ON f.car_id=c.car_id SET f.photo_status=1 , c.photo_count=c.photo_count+1 WHERE f.photo_id IN ($ids) Basically, two tables (car & photo) are related. The list in $ids contains unique photo ids, such as (34, 87, 98, 12). With the query, I'm setting the status of each photo in that list to "1" in the photo table and simultaneously incrementing the photo count in the car table for the car at hand. It works but there's one snag: Because the list can contain multiple photo ids that relate to the same car, the photo count only ever gets incremented once. If the list had 10 photos associated with the same car, photo_count would become 1 .... whereas I'd like to increment it to 10. Is there a way to make the incrementation occur for each photo individually through the join, as opposed to MySQL overthinking it for me? I hope the above makes sense. Thanks.

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  • Application start in global.asax

    - by Zerotoinfinite
    Hi experts, I am developing my application in asp.net 3.5 and sql server 2005, and I want to record the visitor info into my database, like once the visitor enter my website, I'll insert his browser details to the database. [It's not necessary that visitor login my website]. Now I am confused where to put my code, If I put insert function in every page_load then on every page it will execute and I'll not be able to get the exact number of visitor, visited my website. Shall I go with application_start in Global.asax ?? Please help.

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  • What is this C function supposed to do based on description?

    - by user1261445
    unsigned int hex_c0c0c0c0(): Allowed operators: + - = & | ~ << ! >> Allowed constants: 1 2 4 8 16 Return 0xc0c0c0c0 The above is the description I have been given and I have to write the code for it. Can someone tell me what exactly the function is supposed to do? All the description says is what I have pasted above, so I'm not sure what my goal is. I'm sure it is an easy enough function to program on my own, but it would help if someone could tell me what the function is supposed to do, and maybe provide sample input/output so that I know my code is working correctly once I program this. Thanks.

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