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• Should I learn VB.NET or C#?

  - by Ravi

  Background I have decided to do my graduation project (yet to start) in .NET. Regarding it, I am bit confused about: what language should I learn: VB.NET or C#? What I have learnt from those who know it that both VB.NET and C# have: The same concepts VB.NET is simpler as it is more like English statements but also C# is simple too if you already know C (Which I do know) Question So considering some factors, e.g. career point of view, newness, challenging and beneficial, etc., what language should I choose? Please help me out. And clearly do justify your answer (whatever reason you have.) References (Extra) A little information about what project I am doing: It is a database file system. Technologies I'll be using are SQL Server, WPF, etc. I just love the concept of Database file system.So those who want to know more about Database file system, here are the links DBFS (This one is really good.Serves as primary reference for me) Towards A Single Folder Filesystem stackoverflow-What is a database file system? UPDATE1 : After some really good explained answers (actually all are good at their place), I have finally decided to go with C# for myself. Thank you all. Still, you are requested to put your opinion (Once it is reopened,of course) UPDATE2 : Question reopened and made community wiki.Thank you all.

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• Distributed Lock Service over MySql/GigaSpaces/Netapp

  - by ripper234

  Disclaimer: I already asked this question, but without the deployment requirement. I got an answer that got 3 upvotes, and when I edited the question to include the deployment requirement the answer then became irrelevant. The reason I'm resubmitting is because SO considers the original question 'answered', even though I got no meaningful upvoted answer. I opened a uservoice submission about this problem. The reason I reposted is so StackOverflow consider the original question answered, so it doesn't show up on the 'unanswered questions' tab. Which distributed lock service would you use? Requirements are: A mutual exclusion (lock) that can be seen from different processes/machines lock...release semantics Automatic lock release after a certain timeout - if lock holder dies, it will automatically be freed after X seconds Java implementation Easy deployment - must not require complicated deployment beyond either Netapp, MySql or GigaSpaces. Must play well with those products (especially GigaSpaces - this is why TerraCotta was ruled out). Nice to have: .Net implementation If it's free: Deadlock detection / mitigation I'm not interested in answers like "it can be done over a database", or "it can be done over JavaSpaces" - I know. Relevant answers should only contain a ready, out-of-the-box, proven implementation.

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• Find all cycles in graph, redux

  - by Shadow

  Hi, I know there are a quite some answers existing on this question. However, I found none of them really bringing it to the point. Some argue that a cycle is (almost) the same as a strongly connected components (s. http://stackoverflow.com/questions/546655/finding-all-cycles-in-graph/549402#549402) , so one could use algorithms designed for that goal. Some argue that finding a cycle can be done via DFS and checking for back-edges (s. boost graph documentation on file dependencies). I now would like to have some suggestions on whether all cycles in a graph can be detected via DFS and checking for back-edges? My opinion is that it indeed could work that way as DFS-VISIT (s. pseudocode of DFS) freshly enters each node that was not yet visited. In that sense, each vertex exhibits a potential start of a cycle. Additionally, as DFS visits each edge once, each edge leading to the starting point of a cycle is also covered. Thus, by using DFS and back-edge checking it should indeed be possible to detect all cycles in a graph. Note that, if cycles with different numbers of participant nodes exist (e.g. triangles, rectangles etc.), additional work has to be done to discriminate the acutal "shape" of each cycle.

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• DQL delete from multiple tables (doctrine)

  - by singer

  Need to perform DQL delete from multple related tables. In SQL it is something like this: DELETE r1,r2 FROM ComRealty_objects r1, com_realty_objects_phones r2 WHERE r1.id IN (10,20) AND r2.id_object IN (10,20) I need to perform this statement using DQL, but I'm stuck on this :( <?php $dql = Doctrine_Query::create() ->delete('phones, comrealtyobjects') ->from('ComRealtyObjects comrealtyobjects') ->from('ComRealtyObjectsPhones phones') ->whereIn("comrealtyobjects.id", $ids) ->whereIn("phones.id_object", $ids); echo($dql->getSqlQuery()); ?> But DQL parser gives me this result: DELETE FROM `com_realty_objects_phones`, `ComRealty_objects` WHERE (`id` IN (?) AND `id_object` IN (?)) Searching google and stack overflow I found this(useful) topic: http://stackoverflow.com/questions/2247905/what-is-the-syntax-for-a-multi-table-delete-on-a-mysql-database-using-doctrine But this is not exactly my case - there was delete from single table. If there is a way to override dql parser behaviour? Or maybe some other way to delete records from multiple tables using doctrine. Note: If you are using doctrine behaviours(Doctrine_Record_Generator) you need first to initialize those tables using Doctrine_Core::initializeModels() to perform DQL operations on them.

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• Why is Lua considered a game language?

  - by Hoffmann

  I have been learning about Lua in the past month and I'm absolutely in love with the language, but all I see around that is built with lua are games. I mean, the syntax is very simple, there is no fuss, no special meaning characters that makes code look like regex, has all the good things about a script language and integrates so painlessly with other languages like C, Java, etc. The only down-side I saw so far is the prototype based object orientation that some people do not like (or lack of OO built-in). I do not see how ruby or python are better, surely not in performance ( http://shootout.alioth.debian.org/gp4/benchmark.php?test=all&lang=lua&lang2=python ). I was planning on writting a web app using lua with the Kepler framework and Javascript, but the lack of other projects that use lua as a web language makes me feel a bit uneasy since this is my first try with web development. Lua is considered a kids language, most of you on stackoverflow probably only know the language because of the WoW addons. I can't really see why that is... http://lua-users.org/wiki/LuaVersusPython this link provides some insights on Lua against Python, but this is clearly biased.

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• Can protobuf-net serialize this combination of interface and generic collection?

  - by tsupe

  I am trying to serialize a ItemTransaction and protobuf-net (r282) is having a problem. ItemTransaction : IEnumerable<KeyValuePair<Type, IItemCollection>></code> and ItemCollection is like this: FooCollection : ItemCollection<Foo> ItemCollection<T> : BindingList<T>, IItemCollection IItemCollection : IList<Item> where T is a derived type of Item. ItemCollection also has a property of type IItemCollection. I am serializing like this: IItemCollection itemCol = someService.Blah(...); ... SerializeWithLengthPrefix<IItemCollection>(stream, itemCol, PrefixStyle.Base128); My eventual goal is to serialize ItemTransaction, but am snagged with IItemCollection. Item and it's derived types can be [de]serialized with no issues, see [1], but deserializing an IItemCollection fails (serializing works). ItemCollection has a ItemExpression property and when deserializing protobuf can't create an abstract class. This makes sense to me, but I'm not sure how to get through it. ItemExpression<T> : ItemExpression, IItemExpression ItemExpression : Expression ItemExpression is abstract as is Expression How do I get this to work properly? Also, I am concerned that ItemTransaction will fail since the IItemCollections are going to be differing and unknown at compile time (an ItemTransaction will have FooCollection, BarCollection, FlimCollection, FlamCollection, etc). What am I missing (Marc) ? [1] http://stackoverflow.com/questions/2276104/protobuf-net-deserializing-across-assembly-boundaries

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• are there code signing certificates cheaper than US $99 per year? [closed]

  - by gerryLowry

  ksoftware discounts Commodo code signing certificates to US $99 per year. in the past, I've seen Commodo code signing certificates for US $80. I'm excluding CAcert which AFAIK are FREE but are not covered by browsers like IE AFAIK. QUESTION: What is the best price per year for a code signing certificate? Thank you ~~ gerry (lowry) Edit: **THIS SHOULD NOT HAVE BEEN CLOSED** from the FAQ: http://stackoverflow.com/faq ---------------------------- What kind of questions can I ask here? Programming questions, of course! As long as your question is: * detailed and specific <====== YES! * written clearly and simply <====== YES! * of interest to other programmers <====== YES! I've been programming for over 40 years. http://gerrylowryprogrammer.com/ I've taught computer programming at the community college level. I'm a Star level contributer to forums.asp.net. http://forums.asp.net/members/gerrylowry.aspx imo, I've a very good idea what is of interest to other programmers. MORE INFORMATION Ensuring the integrity of code and executables that one distributes is just as much about programming as is knowing how to flip bits in assembler, use delegates in c#, and use the BDD context/specification still of "test first testing".

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• Updating a DLL in a Production ASP.NET Web Site bin folder

  - by Josh Stodola

  I want to update a class library (a single DLL file) in a production web application. This web app is pre-compiled (published). I read an answer on StackOverflow (sorry, can't seem to find it anymore because the Search function does not work very well), that led me to believe that I could just paste the new DLL in the bin folder and it would be picked up without problems (this would cause the WP to recycle, which is fine with me because we do not use InProc session state). However, when I tried this, my site blows up and gives a FileLoadException saying that the assembly manifest definition does not match the assembly reference. What in the world is this?! Updating the DLL in Visual Studio and re-deploying the entire site works just fine, but it is a huge pain in the rear. What is the point of having a separate DLL if you have to re-deploy the entire site to implement any changes? Here's the question: How can I update a DLL on a production web site without breaking the app and without re-deploying all of the files?

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• Java JSP/Servlet: controller servlet throwing the famous stack overflow

  - by NoozNooz42

  I've read several docs and I don't get it: I know I'm doing something wrong but I don't understand what. I've got a website that is entirely dynamically generated: there's hardly any static content at all. So, trying to understand JSP/Servlet, I've written my own "front controller" intercepting every single query, it looks like this: <servlet-mapping> <servlet-name>defaultservlet</servlet-name> <url-pattern>/*</url-pattern> </servlet-mapping> Basically I want any user request, like: example.org example.org/bar example.org/foo.html to all go through a default servlet which I've written. The servlet then examines the URI and find to which .jsp the request must be dispatched, and then does, after having set all the attributes correctly, a: RequestDispatcher dispatcher = getServletContext().getRequestDispatcher("/WEB-INF/jsp/index.jsp"); dispatcher.forward(req, resp); When I'm using a url-pattern (in web.xml) like, say, *.html, everything works fine. But when I change it to /* (to really intercept everything), I enter an endless loop and it ends up with a... StackOverflow :) When the request is dispatched, is the URI ".../WEB-INF/jsp/index.jsp" itself matched by the web.xml filter /* that I set? How should I do if I want to intercept everything using a /* url-pattern and yet be able to dispatch/forward/? I'm not asking about specs/Javadocs here: I'm really confused about the bigger picture and I'd need some explanation as to what could be going on. Am I not supposed to intercept really everything? If I can intercept everything, what should I be aware of regarding forwarding/dispatching?

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• Windows Batch file to echo a specific line number

  - by Lee

  So for the second part of my current dilemma, I have a list of folders in c:\file_list.txt. I need to be able to extract them (well, echo them with some mods) based on the line number because this batch script is being called by an iterative macro process. I'm passing the line number as a parameter. @echo off setlocal enabledelayedexpansion set /a counter=0 set /a %%a = "" for /f "usebackq delims=" %%a in (c:\file_list.txt) do ( if "!counter!"=="%1" goto :printme & set /a counter+=1 ) :printme echo %%a which gives me an output of %a. Doh! So, I've tried echoing !a! (result: ECHO is off.); I've tried echoing %a (result: a) I figured the easy thing to do would be to modify the head.bat code found here: http://stackoverflow.com/questions/130116/dos-batch-commands-to-read-first-line-from-text-file except rather than echoing every line - I'd just echo the last line found. Not as simple as one might think. I've noticed that my counter is staying at zero for some reason; I'm wondering if the set /a counter+=1 is doing what I think it's doing.

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• why unsigned int 0xFFFFFFFF is equal to int -1?

  - by conejoroy

  perhaps it's a very stupid question but I'm having a hard time figuring this out =) in C or C++ it is said that the maximum number a size_t (an unsigned int data type) can hold is the same as casting -1 to that data type. for example see http://stackoverflow.com/questions/1420982/invalid-value-for-sizet Why?? I'm confused.. I mean, (talking about 32 bit ints) AFAIK the most significant bit holds the sign in a signed data type (that is, bit 0x80000000 to form a negative number). then, 1 is 0x00000001.. 0x7FFFFFFFF is the greatest positive number a int data type can hold. then, AFAIK the binary representation of -1 int should be 0x80000001 (perhaps I'm wrong). why/how this binary value is converted to anything completely different (0xFFFFFFFF) when casting ints to unsigned?? or.. how is it possible to form a binary -1 out of 0xFFFFFFFF? I have no doubt that in C: ((unsigned int)-1) == 0xFFFFFFFF or ((int)0xFFFFFFFF) == -1 is equally true than 1 + 1 == 2, I'm just wondering why. thanks!

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• Django: Serving Media Behind Custom URL

  - by TheLizardKing

  So I of course know that serving static files through Django will send you straight to hell but I am confused on how to use a custom url to mask the true location of the file using Django. http://stackoverflow.com/questions/2681338/django-serving-a-download-in-a-generic-view but the answer I accepted seems to be the "wrong" way of doing things. urls.py: url(r'^song/(?P<song_id>\d+)/download/$', song_download, name='song_download'), views.py: def song_download(request, song_id): song = Song.objects.get(id=song_id) fsock = open(os.path.join(song.path, song.filename)) response = HttpResponse(fsock, mimetype='audio/mpeg') response['Content-Disposition'] = "attachment; filename=%s - %s.mp3" % (song.artist, song.title) return response This solution works perfectly but not perfectly enough it turns out. How can I avoid having a direct link to the mp3 while still serving through nginx/apache? EDIT 1 - ADDITIONAL INFO Currently I can get my files by using an address such as: http://www.example.com/music/song/1692/download/ But the above mentioned method is the devil's work. How can I accomplished what I get above while still making nginx/apache serve the media? Is this something that should be done at the webserver level? Some crazy mod_rewrite? http://static.example.com/music/Aphex%20Twin%20-%20Richard%20D.%20James%20(V0)/10%20Logon-Rock%20Witch.mp3

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• Use of var keyword in C#

  - by kronoz

  After discussion with colleagues regarding the use of the 'var' keyword in C# 3 I wondered what people's opinions were on the appropriate uses of type inference via var? For example I rather lazily used var in questionable circumstances, e.g.:- foreach(var item in someList) { // ... } // Type of 'item' not clear. var something = someObject.SomeProperty; // Type of 'something' not clear. var something = someMethod(); // Type of 'something' not clear. More legitimate uses of var are as follows:- var l = new List<string>(); // Obvious what l will be. var s = new SomeClass(); // Obvious what s will be. Interestingly LINQ seems to be a bit of a grey area, e.g.:- var results = from r in dataContext.SomeTable select r; // Not *entirely clear* what results will be here. It's clear what results will be in that it will be a type which implements IEnumerable, however it isn't entirely obvious in the same way a var declaring a new object is. It's even worse when it comes to LINQ to objects, e.g.:- var results = from item in someList where item != 3 select item; This is no better than the equivilent foreach(var item in someList) { // ... } equivilent. There is a real concern about type safety here - for example if we were to place the results of that query into an overloaded method that accepted IEnumerable<int> and IEnumerable<double> the caller might inadvertently pass in the wrong type. Edit - var does maintain strong typing but the question is really whether it's dangerous for the type to not be immediately apparent on definition, something which is magnified when overloads mean compiler errors might not be issued when you unintentionally pass the wrong type to a method. Related Question: http://stackoverflow.com/questions/633474/c-do-you-use-var

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• nhibernate - mapping with contraints

  - by Tobias Müller

  Hello everybody, I am having a Problem with my nhibernate-mapping and I can't find a solution by searching on stackoverflow/google/documentation. The database I am using has (amongst others) two tables. One is unit with the following fields: id enduring_id starts ends damage_enduring_id [...] The other one is damage, which has the following fields: id enduring_id starts ends [...] The units are assigned to a damage and one damage can have zero, one or more units working on it. Every time a unit moves to annother damage, the dataset is copied. The field "ends" of the old record and "starts" of the new record are set to the current time stamp, enduring_id stays the same. So if I want to know which units were working on a damage at a certain time, I do the following select: select * from unit join damage on damage.enduring_id = unit.damage_enduring_id where unit.starts <= 'time' and unit.ends = 'time' (This is not an actualy query from the database, I made it up to make clear what I mean. The the real database is a little more complex) Now I want to map it that way, so I can load all the damages which are valid at one time (starts <= wanted time <= ends) and that each of them has a Bag with all the attached units at that time (again starts <= wanted time <= ends). Is this possible within the mapping? Sorry if this is a stupid question, but I am pretty new to nhibernate and I have no clue how to do it. Thanks a lot for reading my post! Bye, Tobias

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• iPhone: objc_class_name_TTTabStrip symbol not found build error

  - by user187532

  Hello friends, I am trying to implement 'scrollview' effect in 'Tabbar' which has 'TabItems'. I found that the good example is from 'facebook' open source 'TTCatlog' project 'Tabs' section. So i included all the source from it to my project and trying to build it. I have followed the following links to go ahead on this: http://stackoverflow.com/questions/822792/how-to-create-a-horizontal-scrolling-view-on-iphone source: http://github.com/facebook/three20/tree/master/samples/ My calling code is like below: _tabBar1 = [[TTTabStrip alloc] initWithFrame:CGRectMake(10, 68, 300, 28)]; _tabBar1.tabItems = [NSArray arrayWithObjects: [[[TTTabItem alloc] initWithTitle:@"Item 1"] autorelease], [[[TTTabItem alloc] initWithTitle:@"Item 2"] autorelease], [[[TTTabItem alloc] initWithTitle:@"Item 3"] autorelease], [[[TTTabItem alloc] initWithTitle:@"Item 4"] autorelease], [[[TTTabItem alloc] initWithTitle:@"Item 5"] autorelease], [[[TTTabItem alloc] initWithTitle:@"Item 6"] autorelease], [[[TTTabItem alloc] initWithTitle:@"Item 7"] autorelease], [[[TTTabItem alloc] initWithTitle:@"Item 8"] autorelease], [[[TTTabItem alloc] initWithTitle:@"Item 9"] autorelease], [[[TTTabItem alloc] initWithTitle:@"Item 10"] autorelease], nil]; [self.navigationController.view addSubview:_tabBar1]; My project folder as like below: ..../iphone/MyProgram/MyProgram.xcodeproj ..../iphone/Three20/src/Three20.... In my project settings for header search path, I have ../Three20/src But when i try to build it, it throws the following error: "objc_class_name_TTTabStrip symbol not found" "objc_class_name_TTTabItem symbol not found" I see there, all these files (.h and .m) are availbale there. Could someone please help what's wrong there and how do i get rid of this issue and continue working with it?

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• Valueurl Binding On Large Arrays Causes Sluggish User Interface

  - by Hooligancat

  I have a large data set (some 3500 objects) that returns from a remote server via HTTP. Currently the data is being presented in an NSCollectionView. One aspect of the data is a path pack to the server for a small image that represents the data (think thumbnail for simplicity). Bindings works fantastically for the data that is already returned, and binding the image via a valueurl binding is easy to do. However, the user interface is very sluggish when scrolling through the data set - which makes me think that the NSCollectionView is retrieving all the image data instead of just the image data used to display the currently viewable images. I was under the impression that Cocoa controls were smart enough to only retrieve data for the information that is actually being output to the user interface through lazy loading. This certainly seems to be the case with NSTableView - but I could be misguided on this thought. Should valueurl binding act lazily and, moreover, should it act lazily in an NSCollectionView? I could create a caching mechanism (in fact I already have such a thing in place for another application - see my post here if you are interested http://stackoverflow.com/questions/1740209/populating-nsimage-with-data-from-an-asynchronous-nsurlconnection) but I really don't want to go this route if I don't have to for this specific implementation as the user could potentially change data sets often and may only want small sub-sets of the data. Any suggested approaches? Thanks!

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• After rewrite Model sales/order_collection it works except in Admin section, why?

  - by latvian

  Hi, I rewrite the sales/order_collection Model or, perhaps, correctly said the Resource. I did that to add filter that filters orders by store_ids. Please see my post to see how i did it http://stackoverflow.com/questions/2426986/how-to-rewrite-collection My new model works and here is how i tested $path = '../magento'; require_once('app/Mage.php'); umask(0); $app = Mage::app('base','website'); $col = Mage::getResourceModel('sales/order_collection')->addAttributeToSelect('*'); echo "<br>Size of the colletion: ".$col->getSize(); This new Model filters and returns # of orders just like i want. It returns # of orders also when i run it inside any of my created modules, but not in Admin section then it returns 0 orders In Admin section the same line is called as above ( Mage::getResourceModel('sales/order_collection')-addA....) from Mage_Adminhtml_Block_Sales_Order_Grid class (line 50) . It can be initiated when going Admin-Sales-Orders. However, it is returning 0 orders instead of # of orders How is it that the new Model returns orders anywhere else but from Admin section? What is done differently in Admin section?..please help. I have spent hours and hours and any pointers will help Thank you, Margots

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• How can I start using twill?

  - by brilliant

  I am sorry I have already asked this question on "Superuser", but nobody answers there, so I deleted it from "Superuser" and decided to post it here. Hope it's not a big crime, especially given the fact that I was firstly advised to use twill here on "StackOverflow" (not on "SuperUser") How do I start using twill? I have just downloaded it, unpacked it and clicked on the setup .py file in the folder. The black window (terminal) appeared for a moment and vanished. (I do have Python 2.5 installed on my computer - along with SDK from Google App Engine) In the twill documentation section it says: Downloading twill The latest release of twill is twill 0.9, released Thursday, December 27th, 2007; it is available for download at http://darcs.idyll.org/~t/projects/twill-0.9.tar.gz. You can also use Python's easy_install to install or upgrade twill. twill works with Python 2.3 or later. To start using twill, install it and then type twill-sh. At the prompt type: go http://www.slashdot.org/ show showforms showhistory I am not clear from this passage what I am supposed to type (only "twill-sh" or "twill-sh" and all the words under that line) and where (I tried typing it in the command prompt window of my computer - to no avail) Can, anyone, please, help me out here? Thank You in advance.

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• Use auto_ptr in VC6 dll cause crash

  - by Yan Cheng CHEOK

  // dll #include <memory> __declspec(dllexport) std::auto_ptr<int> get(); __declspec(dllexport) std::auto_ptr<int> get() { return std::auto_ptr<int>(new int()); } // exe #include <iostream> #include <memory> __declspec(dllimport) std::auto_ptr<int> get(); int main() { { std::auto_ptr<int> x = get(); } std::cout << "done\n"; getchar(); } The following code run perfectly OK under VC9. However, under VC6, I will experience an immediate crash with the following message. Debug Assertion Failed! Program: C:\Projects\use_dynamic_link\Debug\use_dynamic_link.exe File: dbgheap.c Line: 1044 Expression: _CrtIsValidHeapPointer(pUserData) Is it exporting auto_ptr under VC6 is not allowed? It is a known problem that exporting STL collection classes through DLL. http://stackoverflow.com/questions/2451714/access-violation-when-accessing-an-stl-object-through-a-pointer-or-reference-in-a However, I Google around and do not see anything mention for std::auto_ptr. Any workaround?

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• Layering Cocoa WebView - Drawing on top?

  - by Josh

  http://stackoverflow.com/questions/1618498/webview-in-core-animation-layer The only other thread I can find is the above which doesn't necessarily fit my needs. Is there a reliable way to simply draw a view on top of a webview? I've tried to layer a regular NSView on top of WebView, and it draws right at first, but any movement in the webview (scrolling the page etc) appears to invalidate the view and produces visual artifacts. I've tried: [[[NSApp mainWindow] contentView] addSubview:view positioned:NSWindowAbove relativeTo:webView]; No luck there, same problems -- z-ordering doesn't seem to work unless I'm missing something. Is this just a limitation of webviews? I also tried implementing the view above as a window, which worked much better (just controlled the location of the window programmatically). However, the desired behavior is for the user to enter some text into this window, but for it not to steal "focus" -- ie the main window goes inactive (the x - + go gray) when the user clicks on the text field in the new window. Any way to avoid that? I've tried subclassing NSWindow and overriding canBecomeKey (return YES) and canBecomeMain (return NO) but the window still steals focus. Josh

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• What is optimal hardware configuration for heavy load LAMP application

  - by Piotr Kochanski

  I need to run Linux-Apache-PHP-MySQL application (Moodle e-learning platform) for a large number of concurrent users - I am aiming 5000 users. By concurrent I mean that 5000 people should be able to work with the application at the same time. "Work" means not only do database reads but writes as well. The application is not very typical, since it is doing a lot of inserts/updates on the database, so caching techniques are not helping to much. We are using InnoDB storage engine. In addition application is not written with performance in mind. For instance one Apache thread usually occupies about 30-50 MB of RAM. I would be greatful for information what hardware is needed to build scalable configuration that is able to handle this kind of load. We are using right now two HP DLG 380 with two 4 core processors which are able to handle much lower load (typically 300-500 concurrent users). Is it reasonable to invest in this kind of boxes and build cluster using them or is it better to go with some more high-end hardware? I am particularly curious how many and how powerful servers are needed (number of processors/cores, size of RAM) what network equipment should be used (what kind of switches, network cards) any other hardware, like particular disc storage solutions, etc, that are needed Another thing is how to put together everything, that is what is the most optimal architecture. Clustering with MySQL is rather hard (people are complaining about MySQL Cluster, even here on Stackoverflow).

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• PySide Qt script doesn't launch from Spyder but works from shell

  - by Maxim Zaslavsky

  I have a weird bug in my project that uses PySide for its Qt GUI, and in response I'm trying to test with simpler code that sets up the environment. Here is the code I am testing with: http://stackoverflow.com/a/6906552/130164 When I launch that from my shell (python test.py), it works perfectly. However, when I run that script in Spyder, I get the following error: Traceback (most recent call last): File "/home/test/Desktop/test/test.py", line 31, in <module> app = QtGui.QApplication(sys.argv) RuntimeError: A QApplication instance already exists. If it helps, I also get the following warning: /usr/lib/pymodules/python2.6/matplotlib/__init__.py:835: UserWarning: This call to matplotlib.use() has no effect because the the backend has already been chosen; matplotlib.use() must be called *before* pylab, matplotlib.pyplot, or matplotlib.backends is imported for the first time. Why does that code work when launched from my shell but not from Spyder? Update: Mata answered that the problem happens because Spyder uses Qt, which makes sense. For now, I've set up execution in Spyder using the "Execute in an external system terminal" option, which doesn't cause errors but doesn't allow debugging, either. Does Spyder have any built-in workarounds to this?

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• Perl, regex, extract data from a line

  - by perlnoob

  Im trying to extract part of a line with perl use strict; use warnings; # Set path for my.txt and extract datadir my @myfile = "C:\backups\MySQL\my.txt"; my @datadir = ""; open READMYFILE, @myfile or die "Error, my.txt not found.\n"; while (<READMYFILE>) { # Read file and extract DataDir path if (/C:\backups/gi) { push @datadir, $_; } } # ensure the path was found print @datadir . " \n"; Basically at first im trying to set the location of the my.txt file. Next im trying to read it and pull part of the line with regex. The error Im getting is: Unrecognized escape \m passed through at 1130.pl line 17. I took a look at http://stackoverflow.com/questions/1040657/how-can-i-grab-multiple-lines-after-a-matching-line-in-perl to get an idea of how to read a file and match a line within it, however im not 100% sure I'm doing this right or in the best way. I also seem to produce the error: Error, my.txt not found. But the file does exist in the folder C:\backups\MySQL\

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• How to react when asked a question you already know during an interview

  - by DevNull

  The short story:- If you are asked a tough algorithmic/puzzle question during an interview, whose solution is already known to you, do you:- Honestly tell the interviewer that you know this question already? -- this could result in bursting the interviewer's ego and him increasing the complexity level of the subsequent questions. Do an Oscar deserving performance and act as if you are thinking and trying hard and slowly getting to the solution? -- depending on your acting skills, could majorly impress the interviewer making the rest of the interview easier. Long story:- OK, this question comes as a result of what happened to me in a recent telephonic interview that I gave - the interview was supposed to be all algorithmic. The interviewer started with an algorithmic question which I had luckily already seen here on Stackoverflow. The best solution to that problem is not very intuitive and is more of a you-get-it-if-you-know-it kind. Now, just to not disappoint the interviewer too much, I took a few seconds as if I was pondering on the problem and then blurted out the answer which I knew too well having read and admired it on SO already. But I guess that gave it away to the interviewer that I already knew this question and since then, he started asking me for more efficient solutions and I kept coming up with approaches (even if not correct or more efficient, but I did touch a lot of different data structures and algos) and he kept asking for more efficient solutions and generally seemed put off by my initial salvo which was unexpected. What should I have done? Cheers!

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• Subclassing NSArrayController in order to limit size of arrangedObjects

  - by Simone Manganelli

  I'm trying to limit the number of objects in an array controller, but I still want to be able to access the full array, if necessary. A simple solution I came up with was to subclass NSArrayController, and define a new method named "limitedArrangedObjects", that returns a limited number of objects from the real set of arranged objects. (I've seen http://stackoverflow.com/questions/694493/limiting-the-number-of-objects-in-nsarraycontroller , but that doesn't address my problem.) I want this property to be observable via bindings, so I set a dependency to arrangedObjects on it. Problem is, when arrangedObjects is updated, limitedArrangedObjects seems not to be observing the value change in arrangedObjects. I've hooked up an NSCollectionView to limitedArrangedObjects, and zero objects are being displayed. (If I bind it to arrangedObjects instead, all the objects show up as expected.) What's the problem? Here's the relevant code: @property (readonly) NSArray *limitedArrangedObjects; - (NSArray *)limitedArrangedObjects; { NSArray *arrangedObjects = [super arrangedObjects]; NSUInteger upperLimit = 10000; NSUInteger count = [arrangedObjects count]; if (count > upperLimit) count = upperLimit; arrayToReturn = [arrangedObjects subarrayWithRange:NSMakeRange(0, count)]; return arrayToReturn; } + (NSSet *)keyPathsForValuesAffectingValueForKey:(NSString *)key; { NSSet *keyPaths = [super keyPathsForValuesAffectingValueForKey:key]; if ([key isEqualToString:@"limitedArrangedObjects"]) { NSSet *affectingKeys = [NSSet setWithObjects:@"arrangedObjects",nil]; keyPaths = [keyPaths setByAddingObjectsFromSet:affectingKeys]; } return keyPaths; }

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