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• Learning Algorithms and Data Structures Fundamentals

  - by valya

  Can you recommend me a book or (better!) a site with many hard problems and exercises about data structures? I'm already answering project Euler questions, but these questions are about interesting, but uncommon algorithms. I hardly used even a simple tree. Maybe there is a site with exercises like: hey, you need to calculate this: ... . Do it using a tree. Now do it using a zipper. Upload your C (Haskell, Lisp, even Pascal or Fortress go) solution. Oh, your solution is so slow! Self-education is very hard then you trying to learn very common, fundamental things. How can I help myself with them without attending to courses or whatever?

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• File private variables in PHP

  - by kayahr

  Is it possible to define private variables in a PHP script so these variables are only visible in this single PHP script and nowhere else? I want to have an include file which does something without polluting the global namespace. It must work with PHP 5.2 so PHP namespaces are not an option. And no OOP is used here so I'm not searching for private class members. I'm searching for "somewhat-global" variables which are global in the current script but nowhere else. In C I could do it with the static keyword but is there something similar in PHP? Here is a short example of a "common.php" script: $dir = dirname(__FILE__); set_include_path($dir . PATH_SEPARATOR . get_include_path()); // Do more stuff with the $dir variable When I include this file in some script then the $dir variable is visible in all other scripts as well and I don't want that. So how can I prevent this?

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• Cannot get mysql gem to work in Snow Leopard, unable to setup ruby on rails environment

  - by user325020

  I am having some serious problems, however this seems to be a common thing. I have Snow Leopard 10.6.3 and here are my other version info: MySQL mysql Ver 14.14 Distrib 5.1.46, for apple-darwin10.2.0 (i386) using readline 5.1 gem 1.3.6 ruby 1.8.7 (2009-06-08 patchlevel 173) [universal-darwin10.0] My problem is that no matter what I do to try and install the mysql gem, i still get the error every time i do rake db:migrate uninitialized constant MysqlCompat::MysqlRes I have installed the mysql gem based on instructions around the web that say to use export ARCHFLAGS="-arch i386 -arch x86_64" ; sudo gem install --no-rdoc --no-ri mysql -- -v 2.7 --with-mysql-dir=/usr/local --with-mysql-config=/usr/local/mysql/bin/mysql_config This DOES work, as it gives this output: Building native extensions. This could take a while... Successfully installed mysql-2.8.1 1 gem installed Any help would be greatly appreciated

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• Can I create a UITableViewController that inherits from a custom subclass of UIViewController?

  - by prendio2

  I have common functionality that I need to access from all screens of my app: a right bar button item and associated action. So as not to repeat the code I would like to set this up in a custom UIViewController and have all my view controllers inherit from it. - (void)viewDidLoad { UIBarButtonItem *rightBarButton = [[UIBarButtonItem alloc] initWithBarButtonSystemItem:UIBarButtonSystemItemPlay target:self action:@selector(lightsCamera)]; self.navigationItem.rightBarButtonItem = rightBarButton; } - (void)lightsCamera { … } However, I have a number of UITableViewControllers however and I would like to know if it is possible for them to inherit the functionality too?

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• How to make .NET WebForm Routing work with Authorization

  - by jakmas

  I have routes that are being registered from the database into an asp.net website (non MVC). The routes register fine, they all work when I am logged in. What I am trying to do is create a landing page based on some route data: Page is [site]/landing/dell The route looks like: "landing/{client}" and it routes to my page Login.aspx, in there I get the client out of the route, then display some custom brand data based on the value. In my web.config, I have my authentication mode set to forms, with my loginUrl = "Login.aspx" When the user does not have the authorization cookie, it redirects the user to: [site]/Login.aspx?ReturnUrl=%2flanding%2fdell instead of keeping the route url, and displaying the correct data. The IIS server actually does not even process the route at all, just sends the user to the Login.aspx page. I have tried several additions to my web.config: etc, and many variations, but nothing seems to work. Ideas anyone? I assume this is a common issue, and it is just not well documented.

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• javascript: execute a bunch of asynchronous method with one callback

  - by Samuel Michelot

  I need to execute a bunch of asynchronous methods (client SQLite database), and call only one final callback. Of course, the ugly way is: execAll : function(callBack) { asynch1(function() { asynch2(function() { ... asynchN(function() { callBack(); }) }) }); } But I know there are better ways to do it. Intuitively I would detect when all call back has been called with a counter to call the final callback. I think this is a common design-pattern, so if someone could point me in the right direction... Thanks in advance !

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• How to organize code using an optional assembly reference?

  - by apoorv020

  I am working on a project and want to optionally use an assembly if available. This assembly is only available on WS 2008 R2, and my ideal product whould be a common binary for both computers with and without the assembly. However, I'm primarily developing on a Windows 7 machine, where I cannot install the assembly. How can I organize my code so that I can (with minimum changes) build my code on a machine without the assembly and secondly, how do I ensure that I call the assembly functions only when it is present. (NOTE : The only use of the optional assembly is to instantiate a class in the library and repeatedly call a (single) function of the class, which returns a boolean. The assembly is fsrmlib, which exposes advanced file system management operations on WS08R2.) I'm currently thinking of writing a wrapper class, which will always return true if the assembly is not present. Is this the right way to go about doing this?

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• How to make sure web services are kept stable from one release to the next?

  - by Tor Hovland

  The company where I work is a software vendor with a suite of applications. There are also a number of web services, and of course they have to be kept stable even if the applications change. We haven't always succeeded with this, and sometimes a customer finds that a service is not behaving as before after upgrading. We now want to handle this better. In general, web services shouldn't change, and if they have to, at least we will know about it and document the change. But how do we ensure this? One idea is to compare the WSDL files with the previous versions at every release. That will make sure the interfaces don't change, but it won't detect that the behavior changes, for example if a bug is introduced in some common library. Another idea is to build up a suite of service tests, for example using soapUI. But then we'll never know if we have covered enough cases. What are some best practices regarding this?

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• disable text drag and drop

  - by maniek

  There is a common feature of modern browsers where a user can select some text and drag it to an input field. Within the same field it causes moving of text, between different fields it does copying. How do I disable that? If there is no portable way, I am mostly interested in firefox. This is an intranet webapp, so I am also interested in modifying the browser/getting a plugin to do this. Maybe some system-level settings (I`m on windows XP)? I need to keep the default select-copy-paste functionality. The background is I have multiple-field data entry forms, and users often drag something by mistake.

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• PDO::ATTR_EMULATE_PREPARES => false

  - by user264058

  I'm new to php and PDO ,so i read this response to a similar post- Does PDO really not use prepared statements with mysql? Yes, by default (at least with version I tested) but native mode can be turned on manually. If not, can it be forced to do so By employing PDO::ATTR_EMULATE_PREPARES setting, the name is pretty self-explanatory. $dbh-setAttribute( PDO::ATTR_EMULATE_PREPARES, false ); should you do that? That's hardest question of them all. Well, I'd say - yes, you should. If you choose PDO as your db driver, there is no point in using it in the emulation mode. by YOUR COMMON SENSE Aren't prepared statements secure from SQL injection, why change if from 'true'-false?? what is native mode??

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• How to Command Query Responsibility Segregation (CQRS) with ASP.NET MVC?

  - by Jeffrey

  I have been reading about Command Query Responsibility Segregation (CQRS). I sort of wonder how would this work with ASP.NET MVC? I get the idea of CQRS conceptually it sounds nice and sure does introduce some complexities (event and messaging pattern) compared to the "normal/common" approach . Also the idea of CQRS sort of against the use of ORM in some ways. I am trying to think how I could use this pattern in the coming projects so if anyone has experience in combining CQRS with ASP.NET MVC and NHibernate please give some concrete examples to help me better understand CQRS and use with ASP.NET MVC. Thanks!

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• Can a binary tree or tree be always represented in a Database as 1 table and self-referencing?

  - by Jian Lin

  I didn't feel this rule before, but it seems that a binary tree or any tree (each node can have many children but children cannot point back to any parent), then this data structure can be represented as 1 table in a database, with each row having an ID for itself and a parentID that points back to the parent node. That is in fact the classical Employee - Manager diagram: one boss can have many people under him... and each person can have n people under him, etc. This is a tree structure and is represented in database books as a common example as a single table Employee.

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• PHP: session isnt saving before header redirect

  - by Matt

  Hi guys, I have read through the php manual for this problem and it seems quite a common issue but i have yet to find a solution. I am saving sessions in a database. My code is as follows: // session $_SESSION['userID'] = $user->id; header('Location: /subdirectory/index.php'); Then at the top of index.php after the session_start(), i have var_dumped the $_SESSION global and the userID is not in there. As i said ive looked through the PHP manual (http://php.net/manual/en/function.session-write-close.php) and neither session_write_close or session_regenerate_id(true) worked for me. Does anybody know a solution? Edit: I have session_start() at the top of my file. When i var_dump the session global before the header redirect, i see the userID in there, but not in the other file, which is in a subdirectory of this script Thanks, Matt

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• Java Non-Blocking HTTP Server

  - by Marcus

  I have written an application using embedded Jetty that makes network calls to other services. I presume that the serving threads are idle whilst waiting for the network calls to complete. Is there any way to have a worker thread that switches between requests to perform work that can be done at the current time and then when the network calls return also handle that? A request would be returned when all work has been completed for it. I know this is a common paradigm, and I have used it for non-blocking TCP networking, but I'm unsure as to how to achieve this on a Java HTTP server whilst also waiting on external results. Any links or explanations are appreciated. Thanks

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• How can you block access form internet explorer in asp mvc

  - by Chase Aucoin

  I love microsoft development products! I hate microsoft browsers... I have made the decision to cut ties with internet explorer until they add support for some common W3 approved items. Namely 'multiple' in forms as well as about 5 other things... and as such I would like to urge my visitors to use a better browser. is there a way to setup an http handler or perhaps something in the asax file to route all ie users to a custom page? Thanks for the help! p.s. microsoft why must you make me love you and hate you.

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• asp.net-mvc feature - one css file per (view / master-page / user-control)

  - by Mendy

  I'm trying to implement the following feature: I want just one css file to be attached for any page that I rendered. For example take StackOverflow site. For the questions page, we will have questions.css file. so.com/questions ---> questions.css so.com/question/1234/title ---> question.css so.com/about ---> about.css so.com/faq ---> faq.css Now, I know that this css files share code in common, because they may have the same MasterPage(s) / UserControls. So, the solution need to take into account MasterPages, views and usercontrols as well. So, what will be the right solution for this kind of problem? I'm thinking about one solution, I'll put is as an answer, but maybe you have a better solution for this?

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• "Collection was modified; enumeration operation may not execute." on form disposal.

  - by cyclotis04

  "Collection was modified; enumeration operation may not execute." appears to be a common error with foreach loops, but I can't figure mine out. I have two classes of forms. One is begun on startup, and a button creates new instances of the second form, and displays them. When I close the secondary forms, I get an InvalidOperationException. FirstForm.cs public partial class FirstForm : Form { SecondForm frmSecond; ... private void button1_Click(object sender, EventArgs e) { frmSecond= new SecondForm (); frmSecond.Show(); } } SecondForm.designer.cs partial class SecondForm { ... protected override void Dispose(bool disposing) { if (disposing && (components != null)) { components.Dispose(); } base.Dispose(disposing); // InvalidOperationException thrown here. } }

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• New programming jargon you coined?

  - by jdk

  What programming terms have you coined that have taken off in your own circles? (i.e. have heard others repeating it?) It might be within your own team, workplace or garnered greater popularity on the Internet. Define your programming term, word or phrase in bold followed by an explanation, citation and/or usage example so we can use it in appropriate context. This question serves in the spirit of communication among programmers through sharing of terminology with each other, to benefit us by its propagation within our own teams and environments. Please no repeats of common jargon already ingrained in the programming culture like: "kludge", "automagically", "cruft", etc. (unless you coined it). Stealing from the comments: A shared vocabulary is the basis of communication, not just among programmers, Note: This Programming question has been reworded/reorganized to phrase a real question and remove ambiguity, vagueness and rhetorical device. It is not difficult to know what is being asked & question can be reasonably answered (see answers below).

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• "autotest/rails [...] doesn't [...] exist. Aborting"

  - by Ethan

  I'm finding that autotest has stopped working... $ autotest loading autotest/rails Autotest style autotest/rails doesn't seem to exist. Aborting. According to this blog post, the common reason for this error is that people don't have the autotest-rails gem installed. However, I definitely have that installed: autotest-rails (4.1.0) ZenTest (4.1.4, 4.1.3, 4.1.1, 4.0.0, 3.11.1, 3.11.0, 3.10.0, 3.9.3, 3.9.2) I haven't installed any new gems today or yesterday, though I might have done a gem update yesterday. Another issue I saw mentioned was incompatibility with Ruby 1.9, but I'm using MRI Ruby 1.8.6.

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• Are there any design-patterns specifically useful for game-development?

  - by Baelnorn

  This question's been bugging me for a long time. I've always wondered how game developers were solving certain problems or situations that are quite common in certain genres. For example, how would one implement the quests of a typical role-playing game (e.g. BG or TES)? Or how would you implement weapons with multiple stacking effects in a first-person shooter (e.g. the Shrink-gun or Freezer from DN3D)? How would you implement multiple choice options with a possibly intricate decision tree leading to several different outcomes (e.g. the mission trees in WC)? Are there any examples or other resources for that? Blogs? Books? Sourcecode?

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• Glew in VS 2010: unresolved external symbol __imp__glewInit

  - by NoviceCai

  I am learning OpenGL by following the redbook. When I come to around page 90, I need use glGenBuffers(); Then I need install "glew". By following the steps in www.cs.uiowa.edu/~cwyman/classes/common/howto/winGLUT.html I download glew.zip from glew.sourceforge.net/ and unpack the files. I put glew.h in C:\Program Files (x86)\Microsoft SDKs\Windows\v7.0A\Include and put glew32.lib in C:\Program Files (x86)\Microsoft SDKs\Windows\v7.0A\Lib and put glew32.dll in C:\Windows\System32. After that, I build my project in VS 2010 and in Linker-input, I add dependencies glew32.lib. But when I build it, I have error unresolved external symbol _imp_glewInit I spend whole day to search solutions, but did not find one. Hope someone can help me with this.

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• Check for Existence of a Result in Linq-to-xml

  - by NateD

  I'm using Linq-to-XML to do a simple "is this user registered" check (no security here, just making a list of registered users for a desktop app). How do I handle the result from a query like this: var people = from person in currentDoc.Descendants("Users") where (string)person.Element("User") == searchBox.Text select person; I understand the most common way to use the result would be something like foreach (var line in people){ //do something here } but what do you do if person comes back empty, which is what would happen if the person isn't registered? I've looked around on this site and on MSDN and haven't found a really clear answer yet. Extra credit: Give a good explanation of what people contains.

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• MSBuild Starter Kits - i.e. Copy and just start modding...

  - by vdh_ant

  Hi guys Just wondering if anyone knows if there are any MSBuild starter kits out there. What I mean by starter kits is that from the looks of it most builds to kinda the same sort of steps with minor changes here and there (i.e. most builds would run test, coverage, zip up the results, produce a report, deploy etc). Also what most people in general want from a CI build, test build, release build is mostly the same with minor changes here and there. Now don't get me wrong i think that most scripts are fairly different in the end. But I can't help but think that most start out life being fairly similar. Hence does anyone know of any "starter kits" that have like a dev/CI/test/release build with the common tasks that most people would want that you can just start changing and modifying? Cheers Anthony

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• Flash AS3 - Scroll dynamic textfield to a specific part just like HTML anchor

  - by Aamir Mahmood

  Hi, We are building a flash website with cms at the back end, and we are allowing admin to put anchors inside a content. Later we created a smaller version of the whole content to display just a small part and then [read more] button. Which add a new layer on top of every thing acting like a popup and it is populated with complete content. Now we would like to scroll that text inside popup to that portion which [read more] button was clicked. The most common example inside HTMl is go to top link in footer on most of the sites which move the whole document to top. Happy codding.

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• Log4j - Logging to multiple log files based on the project modules

  - by Veera

  Consider this scenario: I have a project with two modules and one common module as below (the package structure): com.mysite.moduleone com.mysite.moduletwo com.mysite.commonmodule In the above, the commonmodule classes can be used by other two modules. The question: I need to configureLog4J such a way that the log messages from moduleone and moduletwo goes to different log file. I can always do this using using category. But the real problem is when I want to log the messages from the commonmodule also. So, when the commonmodule classes are called from moduleone the commonmodule log messages should go to the moduleone log file. If the commonmodule is accesse from moduletwo the commonmodule log messages should go to moduletwo log file. Is it possible to configure Log4J in this fashion? Any comments? PS: I think I made my question clear. If any confusion, leave a comment, wil try to clear it. :)

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