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• How can I write System preferences with Java? Can I invoke UAC?

  - by Jonas

  How can I write system preferences with Java, using Preferences.systemRoot()? I tried with: Preferences preferences = Preferences.systemRoot(); preferences.put("/myapplication/databasepath", pathToDatabase); But I got this error message: 2010-maj-29 19:02:50 java.util.prefs.WindowsPreferences openKey VARNING: Could not open windows registry node Software\JavaSoft\Prefs at root 0x80000002. Windows RegOpenKey(...) returned error code 5. Exception in thread "AWT-EventQueue-0" java.lang.SecurityException: Could not open windows registry node Software\JavaSoft\Prefs at root 0x80000002: Access denied at java.util.prefs.WindowsPreferences.openKey(Unknown Source) at java.util.prefs.WindowsPreferences.openKey(Unknown Source) at java.util.prefs.WindowsPreferences.openKey(Unknown Source) at java.util.prefs.WindowsPreferences.putSpi(Unknown Source) at java.util.prefs.AbstractPreferences.put(Unknown Source) at biz.accountia.pos.install.Setup$2.actionPerformed(Setup.java:43) I would like to do this, because I want to install an embedded JavaDB database, and let multiple users on the computer to use the same database with the application. How to solve this? Can I invoke UAC and do this as Administrator from Java? And if I log in as Administrator when writing, can I read the values with my Java application if I'm logged in as a User?

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• Ways to gain a deeper understanding of programming concepts?

  - by MrPlow

  I'm a marketer and have been messing around in PHP/MySQL for years. Recently (the last several months) I've been making my own scripts/programs in Python and I've really enjoyed the whole problem solving process. I've read(skimmed) some books and understand the basics of OOP, polymorphism, etc.. I have a general interest in AI and Natural Language in particular but it seems these things require a masters in Computer Science. My knowledge of math is poor. The last class I took was calculus, and I've forgotten the majority of it. Basically I'm looking for things to learn that will help me think in a more analytic way, and maybe see solutions where I didn't before. Improving my ability to program in Python would be nice too. I don't need to learn a specific language or something for employment, just enjoyment. Although my work often involves web development so some utility would be nice. I don't like learning concepts by just reading them. I need to apply them, even if the examples are contrived. A recommendation of a couple good books or other resources would be nice. :) Apologies if this is too vague/misplaced...

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• Generate a set of strings with maximum edit distance

  - by Kevin Jacobs

  Problem 1: I'd like to generate a set of n strings of fixed length m from alphabet s such that the minimum Levenshtein distance (edit distance) between any two strings is greater than some constant c. Obviously, I can use randomization methods (e.g., a genetic algorithm), but was hoping that this may be a well-studied problem in computer science or mathematics with some informative literature and an efficient algorithm or three. Problem 2: Same as above except that adjacent characters cannot repeat; the i'th character in each string may not be equal to the i+1'th character. E.g., 'CAT', 'AGA' and 'TAG' are allowed, 'GAA', 'AAT', and 'AAA' are not. Background: The basis for this problem is bioinformatic and involves designing unique DNA tags that can be attached to biologically derived DNA fragments and then sequenced using a fancy second generation sequencer. The goal is to be able to recognize each tag, allowing for random insertion, deletion, and substitution errors. The specific DNA sequencing technology has a relatively low error rate per base (~1%), but is less precise when a single base is repeated 2 or more times (motivating the additional constraints imposed in problem 2).

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• Java: Exception in thread main java.lang.NoClassDefFoundError

  - by cath

  I am trying to get the Red5 Flash Media Server working on my computer. I have installed it, but when I run the server I get this error Exception in thread "main" java.lang.NoClassDefFoundError: org/red5/server/Bootstrap Caused by: java.lang.ClassNotFoundException: org.red5.server.Bootstrap at java.net.URLClassLoader$1.run(URLClassLoader.java:217) at java.security.AccessController.doPrivileged(Native Method) at java.net.URLClassLoader.findClass(URLClassLoader.java:205) at java.lang.ClassLoader.loadClass(ClassLoader.java:321) at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:294) at java.lang.ClassLoader.loadClass(ClassLoader.java:266) at java.lang.ClassLoader.loadClassInternal(ClassLoader.java:334) Could not find the main class: org.red5.server.Bootstrap. Program will exit. I came across this link where someone had the same issue: http://trac.red5.org/ticket/762 It looks like they ran this command: export CLASSPATH=3D$RED5_HOME/lib/slf4j-api-1.5.10.jar:$RED5_HOME/lib/logback- core-0.9.18.jar:$RED5_HOME/lib/logback-classic-0.9.18.jar I have red5 installed in /usr/share/red5, so I ran this: export CLASSPATH=3D$/usr/share/red5/lib/slf4j-api-1.5.10.jar:$/usr/share/red5/lib/logback-core-0.9.18.jar:$/usr/share/red5/lib/logback-classic-0.9.18.jar Yet despite all this I am still seeing the same error message.

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• CrystalDecisions.Web reference version changes suddenly when run the webapp

  - by Somebody

  I'm breaking my head with this issue, I have a webapp that has a report using crystal report, in the development pc it works fine, but when copy the same project to another pc, when I load the project (VS 2003) the following msg appears: One or more projects in solution need to be updated to use Crystal Reports XI Release 2. If you choose "Yes", the update will be applied permanently... I choose "Yes" and after that I can see that CrystalDecisions.Web reference has the correct version, and location according to the develpment machine, in this case: 11.5.3300.0. But when run the webapp, I can see when the version and path suddenly changes to: 11.0.3300.0. And when trying to see the report the following error appears: Parser Error Message: The base class includes the field 'CrystalReportViewer1', but its type (CrystalDecisions.Web.CrystalReportViewer) is not compatible with the type of control (CrystalDecisions.Web.CrystalReportViewer). the asp.net has the following: <%@ Register TagPrefix="cr" Namespace="CrystalDecisions.Web" Assembly="CrystalDecisions.Web, Version=11.5.3300.0, Culture=neutral, PublicKeyToken=692fbea5521e1304" %> How is this possible? what's happening here? EDIT This is what I did: the wrong version (11.0.3300.0) was located at: C:\Program Files\Common Files\Business Objects\3.0\managed and the right version (11.5.3300.0) is located at: C:\Program Files\Business Objects\Common\3.5\managed So I just deleted the files of the wrong solution, and I made it work in my new computer, no more errors when running the webapp, the report shows fine. But when try to do the same thing in production server, a different error came out, now an exception: This report could not be loaded due to the following issue: The type initializer for 'CrystalDecisions.CristalReports.Engine.ReportDocument' threw an exception. Any idea what could be causing this error now? Here is the code: Try Dim cr As New ReportDocument cr.Load(strpath) cr.SetDatabaseLogon("usring", "pwding") Select Case rt Case 1 cr.SummaryInfo.ReportTitle = "RMA Ticket" Case 2 cr.SummaryInfo.ReportTitle = "Service Ticket" End Select 'cr.SummaryInfo.ReportTitle = tt cr.SetParameterValue("TicketNo", tn) 'cr.SummaryInfo.ReportComments = comment CrystalReportViewer1.PrintMode = CrystalDecisions.Web.PrintMode.ActiveX CrystalReportViewer1.ReportSource = cr CrystalReportViewer1.ShowFirstPage() 'cr.Close() 'cr.Dispose() Catch ex As Exception MsgBox1.alert("This report could not be loaded due to the following issue: " & ex.Message) End Try

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• Warning in image_graphviz

  - by garcon1986

  Hello, I have got a warning in image_graphviz, i have viewed a post, who has a similar error. I have installed pear image_graphviz package(Image_GraphViz-1.2.1), I also installed graphviz.msi(Graphviz2.25.msi) in windows(But i don't know if does something with image_graphviz and if it does have some effects when i use image_graphviz). Do i need to do something else? Here is my code from pear image_graphviz site. <?php require_once 'Image/GraphViz.php'; error_reporting(E_ALL ^ E_NOTICE); //Added E_NOTICE $gv = new Image_GraphViz(); $gv->addEdge(array('wake up' => 'visit bathroom')); $gv->addEdge(array('visit bathroom' => 'make coffee')); $gv->image(); ?> This is the warning: Warning: fopen(C:\WINDOWS\Temp\gra50.tmp.svg) [function.fopen]: failed to open stream: No such file or directory in C:\wamp\bin\php\php5.3.0\PEAR\Image\GraphViz.php on line 210 Notice: Undefined variable: data in C:\wamp\bin\php\php5.3.0\PEAR\Image\GraphViz.php on line 218 Thanks Pekka Gaiser, I used error_reporting(E_ALL ^ E_NOTICE);. I don't know how to change the temp directory, but c:/windows/temp exists in my computer. I haven't solve the problem. Thanks all for advice.

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• Visual Studio 2008: Can't connect to known good TFS 2010 beta 2

  - by p.campbell

  A freshly installed TFS 2010 Beta 2 is at http://serverX:8080/tfs. A Windows 7 developer machine with VS 2008 Pro SP1 and the VS2008 Team Explorer (no SP). The TFS 2008 Service Pack 1 didn't work for me - "None of the products that are addressed by this software update are installed on this computer." The developer machine is able to browse the TFS site at the above URL. The Issue is around trying to add the TFS server into the Team Explorer window in Visual Studio 2008. Here's a screenshot showing the error: unable to connect to this Team Foundation Server. Possible reasons for failure include: The Team Foundation Server name, port number or protocol is incorrect. The Team Foundation Server is offline. Password is expired or incorrect. The TFS server is up and running properly. Firewall ports are open, and is accessible via the browser on the dev machine!! larger image Question: how can you connect from VS 2008 Pro to a TFS 2010 Beta 2 server? Resolution Here's how I solved this problem: installed VS 2008 Team Explorer as above. re-install VS 2008 Service Pack 1 when adding a TFS server to Team Explorer, you MUST specify the URL as such: http://[tfsserver]:[port]/[vdir]/[projectCollection] in my case above, it was http://serverX:8080/tfs/AppDev-TestProject you cannot simply add the TFS server name and have VS look for all Project Collections on the server. TFS 2010 has a new URL (by default) and VS 2008 doesn't recognize how to gather that list.

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• How to allow the user to select an input file for my SQL AdventureWorks web application?

  - by salvationishere

  I have a SQL and VS 2008 web application that I need to capture the full file path (directories and file name) from the selected file on the client computer. So user selects a file and then clicks on one of the buttons which transfers control to my code for processing. So how do I get its file path? I can get the file name, but not the path. Maybe problem is that while testing this web app, I am using the server instead of client machine. And I learned that on a server you cannot read the full file path due to security concerns. Is this true? If I just want this to work on client machine, which method/class do you recommend? And then how can I test it? My web app allows the user to select an input file and then map columns from the input .MDF file with columns from the selected Adventureworks table. Finally, after they click on the "Append" button, it adds rows from the input file to that table. So I want to capture the path info after they click this button.

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• Good mobile oriented GWT widget library alternatives

  - by Michael Donohue

  I've been developing a travel planning site - tripgrep.com - which is built on appengine, GWT and smartgwt, among other technologies. It is still early days, and the site is now working well on my development environment, which is either a windows or mac computer. However, I am frequently talking up the website to my friends when we are at a bar or other venue, so I am standing there while they try to access the site via an iPhone, Android or Blackberry - I've witnessed all three. It has been painfully obvious that the browser based frontend takes a long time to download on a mobile device. I am pretty sure this is because of the javascript download for SmartGWT. So, I would like to look at alternatives to SmartGWT. What I like about SmartGWT is that it has a reasonable look and feel out of the box - I don't need to learn any design or css and it has an office application look. This is considerably better than the GWT built-in widgets, which just get a blue border. The better look-and-feel is why I went with SmartGWT early on. However, the slow load times are killing me on these mobile demos. So now I want a fast loading widget alternative that has good look-and-feel out of the box. The features I care about are: tabs, good form layout, Google maps API integration, grid data viewing. If those are all available in a library that loads quickly on a mobile device, then that's the library I want.

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• localhost not going to desired VirtualHost

  - by ladaghini

  I have several VirtalHosts set up on my computer. I'd like to visit the site I'm currently working on from a different PC using the my comp's ip address, but every config i've tried keeps taking me to a different virtual host (in fact the first virtualhost I set up on my comp). How do I set up the apache virtualhost configs to ensure that the ip address takes me to the site I want it to. /etc/apache2/sites-available/site-i-want-to-show-up-with-ip-address.conf contains: <VirtualHost *:80> ServerAdmin webmaster@localhost ServerAlias currentsite.com DocumentRoot /path/to/root/of/site-i-want-to-show-up ServerName localhost ScriptAlias /awstats/ /usr/lib/cgi-bin/ CustomLog /var/log/apache2/current-site-access.log combined </VirtualHost> And /etc/apache2/sites-available/site-that-keeps-showing-up.conf contains: <VirtualHost *:80> ServerAdmin webmaster@localhost ServerAlias theothersite.com DocumentRoot /path/to/it <Directory /> Options FollowSymLinks AllowOverride None </Directory> </VirtualHost> I'd appreciate anyone's help. Also, I don't know too much about configuring web servers, and I used tutorials to get the above code.

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• Templates, and C++ operator for logic: B contained by set A

  - by James Morris

  In C++, I'm looking to implement an operator for selecting items in a list (of type B) based upon B being contained entirely within A. In the book "the logical design of digital computers" by Montgomery Phister jr (published 1958), p54, it says: F11 = A + ~B has two interesting and useful associations, neither of them having much to do with computer design. The first is the logical notation of implication... The second is notation of inclusion... This may be expressed by a familiar looking relation, B < A; or by the statement "B is included in A"; or by the boolean equation F11= A + ~B = 1. My initial implementation was in C. Callbacks were given to the list to use for such operations. An example being a list of ints, and a struct containting two ints, min and max, for selection purposes. There, selection would be based upon B = A-min && B <= A-max. Using C++ and templates, how would you approach this after having implemented a generic list in C using void pointers and callbacks? Is using < as an over-ridden operator for such purposes... <ugh> evil? </ugh> (or by using a class B for the selection criteria, implementing the comparison by overloading ?)

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• How do I create a good evaluation function for a new board game?

  - by A. Rex

  I write programs to play board game variants sometimes. The basic strategy is standard alpha-beta pruning or similar searches, sometimes augmented by the usual approaches to endgames or openings. I've mostly played around with chess variants, so when it comes time to pick my evaluation function, I use a basic chess evaluation function. However, now I am writing a program to play a completely new board game. How do I choose a good or even decent evaluation function? The main challenges are that the same pieces are always on the board, so a usual material function won't change based on position, and the game has been played less than a thousand times or so, so humans don't necessarily play it enough well yet to give insight. (PS. I considered a MoGo approach, but random games aren't likely to terminate.) Any ideas? Game details: The game is played on a 10-by-10 board with a fixed six pieces per side. The pieces have certain movement rules, and interact in certain ways, but no piece is ever captured. The goal of the game is to have enough of your pieces in certain special squares on the board. The goal of the computer program is to provide a player which is competitive with or better than current human players.

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• Which book should I choose?

  - by sebastianlarsson

  Hi guys, I'm looking for a good read on object oriented design. The two books I'm currently looking Head First Design Patterns and Head First Object object-oriented analysis & design. They seem very similar when looking at the contents and browsing through available sample text. Which one would be the best choice? About myself: I have a bachelor in computer science and I am currently studying Msc. Software Quality Engineering (read Software Engineering with focus on Quality). I am already confident in object-oriented design and have a lot of programming courses in my backpack. I have done games in c++, courses in advanced java programming (I am SCJP certified), but my preferred language is C#. I have also worked with Java for the last 7 months while studying. I am currently also studying for certificates in C# (apart from my usual studies). So I believe I have the prerequisites of actually understanding the contents of both books. Reason: I just want to be better and keep evolving as a programmer. I think it is fun. I believe Bert Bates and Kathy Sierra are involved in both these books and I have previously read their SCJP preparation book in java. I really do enjoy their style of writing. Other books which I am considering are: Clean Code: A Handbook Of Agile Software Craftsmanship Thx in advance Sebastian

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• std::locale breakage on MacOS 10.6 with LANG=en_US.UTF-8

  - by fixermark

  I have a C++ application that I am porting to MacOSX (specifically, 10.6). The app makes heavy use of the C++ standard library and boost. I recently observed some breakage in the app that I'm having difficulty understanding. Basically, the boost filesystem library throws a runtime exception when the program runs. With a bit of debugging and googling, I've reduced the offending call to the following minimal program: #include <locale> int main ( int argc, char *argv [] ) { std::locale::global(std::locale("")); return 0; } This program fails when I run this through g++ and execute the resulting program in an environment where LANG=en_US.UTF-8 is set (which on my computer is part of the default bash session when I create a new console window). Clearing the environment variable (setenv LANG=) allows the program to run without issues. But I'm surprised I'm seeing this breakage in the default configuration. My questions are: Is this expected behavior for this code on MacOS 10.6? What would a proper workaround be? I can't really re-write the function because the version of the boost libraries we are using executes this statement internally as part of the filesystem library. For completeness, I should point out that the program from which this code was synthesized crashes when launched via the 'open' command (or from the Finder) but not when Xcode runs the program in Debug mode. edit The error given by the above code on 10.6.1 is: $ ./locale terminate called after throwing an instance of 'std::runtime_error' what(): locale::facet::_S_create_c_locale name not valid Abort trap

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• OpenGL Colour Interpolation

  - by Will-of-fortune

  I'm currently working on an little project in C++ and OpenGL and am trying to implement a colour selection tool similar to that in photoshop, as below. However I am having trouble with interpolation of the large square. Working on my desktop computer with a 8800 GTS the result was similar but the blending wasn't as smooth. This is the code I am using: GLfloat swatch[] = { 0,0,0, 1,1,1, mR,mG,mB, 0,0,0 }; GLint swatchVert[] = { 400,700, 400,500, 600,500, 600,700 }; glVertexPointer(2, GL_INT, 0, swatchVert); glColorPointer(3, GL_FLOAT, 0, swatch); glDrawArrays(GL_QUADS, 0, 4); Moving onto my laptop with Intel Graphics HD 3000, this result was even worse with no change in code. I thought it was OpenGL splitting the quad into two triangles, so I tried rendering using triangles and interpolating the colour in the middle of the square myself but it still doesnt quite match the result I was hoping for. Any help would be appreciated. Thanks.

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• BackgroundWorker might be causing my application to hang

  - by alexD

  I have a Form that uses a BackgroundWorker to execute a series of tests. I use the ProgressChanged event to send messages to the main thread, which then does all of the updates on the UI. I've combed through my code to make sure I'm not doing anything to the UI in the background worker. There are no while loops in my code and the BackgroundWorker has a finite execution time (measured in seconds or minutes). However, for some reason when I lock my computer, often times the application will be hung when I log back in. The thing is, the BackgroundWorker isn't even running when this happens. The reason I believe it is related to the BackgroundWorker though is because the form only hangs when the BackgroundWorker has been executed since the application was loaded (it only runs when given a certain user input). I pass this thread a List of TreeNodes from a TreeView in my UI through the RunWorkerAsync method, but I only read those nodes in the worker thread..any modifications I make to them is done in the UI thread through the progressChanged event. I do use Thread.Sleep in my worker thread to execute tests at timed intervals (which involves sending messages over a TCP socket, which was not created in the worker thread). I am completely perplexed as to why my application might be hanging. I'm sure I'm doing something 'illegal' somewhere, I just don't know what.

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• Weird Qt SSL issue -- error "No Error" shows up, nothing else, and if I ignore it, everything works

  - by houbysoft

  The issue is as follows : in my Qt app, I have a QWebView, which I use to load a HTTPS page. Everything worked fine on my development machine, so I'm now trying to get it to run on a test machine. I ran the app, but the page didn't load (the QWebView was blank). After much debugging, I found the problem is that an SSL error shows up, and the sslErrors() signal is fired. Here is my sslErrors() handling code: void blah::sslErrors(QNetworkReply *reply, const QList<QSslError> &errors) { foreach(QSslError error, errors) { qDebug() << error.errorString() << endl; } reply->ignoreSslErrors(); } The only thing the above code prints is: "No error" So there's no error, but unless I call reply->ignoreSslErrors(), the page doesn't load (on the test machine, on my developer computer no error is reported). Huh? Is this a bug? Is it safe to ignore the error, if I make sure it's of the type "No error"?

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• Programatically create web application & sub site

  - by Tejas

  I am using the following code to programatically create a web application & sub site, try { SPWebApplicationBuilder webAppBuilder = new SPWebApplicationBuilder(SPFarm.Local); SPWebApplication newApplication; int myPort = 3333; webAppBuilder.Port = myPort; //Port No. webAppBuilder.RootDirectory = new System.IO.DirectoryInfo("C:\\Inetpub\\wwwroot\\wss\\VirtualDirectories\\" + myPort); webAppBuilder.CreateNewDatabase = true; // Create new database webAppBuilder.DatabaseName = "WSS_Content_372772890a5a4a04abb460cd9ea3bd22"; // Database name webAppBuilder.DatabaseServer = webAppBuilder.DefaultZoneUri.Host; // DatabaseServer Host name/computer name webAppBuilder.UseNTLMExclusively = true; // Use NTLM authentication newApplication = webAppBuilder.Create(); // Create new web application newApplication.Provision(); // Provision it into web farm using (var mySiteCollection = newApplication.Sites.Add("/", "Site 3", "Site 3 Decscription", 1033, "STS#1", "In-Wai-Svr2\\Administrator", "Administrator", "[email protected]")) { using (var rootWeb = mySiteCollection.RootWeb) { // Code customizing root site goes here using (var subSite = rootWeb.Webs.Add("Site3.1", "Site 3.1", "Site 3.1 Description", 1033, "STS#1", true, false)) { // Code customizing sub site goes here } } } } catch(Exception ex) { ; } It works fine i.e. it creates the web application on the specified port with sub site but this sub site will not be shown under Sites menu of Quick launch bar also it will not be shown as a separate tab on the Home Page. Is it possible to do it programatically?

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• How do you program a windows service in C# to start an application for a user?

  - by Swoop

  Is it possible to start a program so that it is available to a user with a windows service? I have been working with the Process.Start() in C#. I can get the service to kickoff some sort of process that appears in the Task Manager list under processes. However, the program nevers appears on the screen. By default, it runs under the user name "SYSTEM". I have adjusted the "Log On" option in the service manager to match the person logged into the computer, but this does not cause a window to appear either. I feel like I am either missing a simple setting, or need to take a different direction for this. Below is the code I have been working with to start up Firefox as a test app. private void startRunDap() { ProcessStartInfo startInfo = new ProcessStartInfo(); startInfo.FileName = "Firefox"; startInfo.WindowStyle = ProcessWindowStyle.Normal; startInfo.UseShellExecute = true; Process.Start(startInfo); //Process.Start("Firefox"); }

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• Time Machine for Windows?

  - by Blub

  Finally got convinced to start using some kind of version control for my code instead of zipping down a copy of the project at the end of each day. Downloaded Tortoise SVN and used it to create a repository localy on my hdd. I've been using it for 2 days now but I have to say that using it is actually more hassle than just copying the project manually in explorer. Sure, you only store incremental changes but with the cheap disks of today I can't really say that's an argument when you only have small projects. I haven't realy found a quick way to browse the older versions of my files eighter. What I want is an infinite undo that is completely transparent while I code, if I save the file I want a backup. I don't want to check out, check in and don't even get me started on moving files. I haven't tried Time Machine for OS X but it looks like it's exactly what I'm looking for. Does such a program exist for windows? Preferably free and with some kind of tagging-system so I can tag a timestamp when the project is working etc. Maybe should add that I mostly work alone on a single computer. Update: Some of you asked why I want backup. Since I work alone it's mostly to allow me to quickly hack up a solution without worrying that something will screw up.

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• How to associate Wi-Fi beacon info with a virtual "location"?

  - by leander

  We have a piece of embedded hardware that will sense 802.11 beacons, and we're using this to make a map of currently visible bssid -> signalStrength. Given this map, we would like to make a determination: Is this likely to be a location I have been to before? If so, what is its ID? If not, I should remember this location: generate a new ID. Now what should I store (and how should I store it) to make future determinations easier? This is for an augmented-reality app/game. We will be using it to associate particular characters and events with "locations". The device does not have internet or cellular access, so using a geolocation service is out of consideration for the time being. (We don't really need to know where we are in reality, just be able to determine if we return there.) It isn't crucial that it be extremely accurate, but it would be nice if it was tolerant to signal strength changes or the occasional missing beacon. It should be usable in relatively low numbers of access points (e.g. rural house with one wireless router) or many (wandering around a dense metropolis). In the case of a city, it should change location every few minutes of walking (continuously-overlapping signals make this a bit more tricky in naive code). A reasonable number of false positives (match a location when we aren't actually there) is acceptable. The wrong character/event showing up just adds a bit of variety. False negatives (no location match) are a bit more troublesome: this will tend to add a better-matching new location to the saved locations, masking the old one. While we will have additional logic to ensure locations that the device hasn't seen in a while will "orphan" any associated characters or events (if e.g. you move to a different country), we'd prefer not to mask and eventually orphan locations you do visit regularly. Some technical complications: signalStrength is returned as 1-4; presumably it's related to dB, but we are not sure exactly how; in my experiments it tends to stick to either 1 or 4, but occasionally we see numbers in between. (Tech docs on the hardware are sparse.) The device completes a scan of one-quarter of the channel space every second; so it takes about 4-5 seconds to get a complete picture of what's around. The list isn't always complete. (We are making strides to fix this using some slight sampling period randomization, as recommended by the library docs. We're also investigating ways to increase the number of scans without killing our performance; the hardware/libs are poorly behaved when it comes to saturating the bus.) We have only kilobytes to store our history. We have a "working" impl now, but it is relatively naive, and flaky in the face of real-world Wi-Fi behavior. Rough pseudocode: // recordLocation() -- only store strength 4 locations m_savedLocations[g_nextId++] = filterForStrengthGE( m_currentAPs, 4 ); // determineLocation() bestPoints = -inf; foreach ( oldLoc in m_savedLocations ) { points = 0.0; foreach ( ap in m_currentAPs ) { if ( oldLoc.has( ap ) ) { switch ( ap.signalStrength ) { case 3: points += 1.0; break; case 4: points += 2.0; break; } } } points /= oldLoc.numAPs; if ( points > bestPoints ) { bestLoc = oldLoc; bestPoints = points; } } if ( bestLoc && bestPoints > 1.0 ) { if ( bestPoints >= (2.0 - epsilon) ) { // near-perfect match. // update location with any new high-strength APs that have appeared bestLoc.addAPs( filterForStrengthGE( m_currentAPs, 4 ) ); } return bestLoc; } else { return NO_MATCH; } We record a location currently only when we have NO_MATCH and the app determines it's time for a new event. (The "near-perfect match" code above would appear to make it harder to match in the future... It's mostly to keep new powerful APs from being associated with other locations, but you'd think we'd need something to counter this if e.g. an AP doesn't show up in the next 10 times I match a location.) I have a feeling that we're missing some things from set theory or graph theory that would assist in grouping/classification of this data, and perhaps providing a better "confidence level" on matches, and better robustness against missed beacons, signal strength changes, and the like. Also it would be useful to have a good method for mutating locations over time. Any useful resources out there for this sort of thing? Simple and/or robust approaches we're missing?

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• Adding an ADO.NET Entity Data Model throws build errors

  - by user3726262

  I am using Visual Studio 2013 express. I create a new project and then I add a database to that project. But, when I add an ADO.NET Entity Framework model to that project and then run the program, I get the following four build errors listed below. To try to remedy this myself, I added the namespaces 'System.Data.Entity' and 'System.Data.Entity.Design', but that didn't help. Also, I uninstalled and re-installed the Nuget package. I also uninstalled and re-installed Visual Studio 2013 Express for Windows Desktop. But these measures didn't help the situation either. Please note that I used to use the Entity Data model just fine. But it was around the time that I did a system restore on my computer, and when I updated VS 2013 with an update offered on the start page, and finally, when I signed up for MS Azure, that I started running into the problem described above. Now I would think that uninstalling and reinstalling Visual Studio 2013, and then installing the 'Nuget' Package would solve all problems. What am I missing here? The errors mentioned above are: Error 1 The type or namespace name 'Infrastructure' does not exist in the namespace 'System.Data.Entity' (are you missing an assembly reference?) C:\Users\John\documents\visual studio 2013\Projects\Riches\Riches\RichesModel.Context.cs 14 30 DataLayer Error 2 The type or namespace name 'DbContext' could not be found (are you missing a using directive or an assembly reference?) C:\Users\John\documents\visual studio 2013\Projects\Riches\Riches\RichesModel.Context.cs 16 52 DataLayer Error 3 The type or namespace name 'DbModelBuilder' could not be found (are you missing a using directive or an assembly reference?) C:\Users\John\documents\visual studio 2013\Projects\Riches\Riches\RichesModel.Context.cs 23 49 DataLayer Error 4 The type or namespace name 'DbSet' could not be found (are you missing a using directive or an assembly reference?) C:\Users\John\documents\visual studio 2013\Projects\Riches\Riches\RichesModel.Context.cs 28 16 DataLayer Thank you and I realize that my last attempt at this question was rather rough-draftish, John

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• Getting Started with Ruby & Ruby on Rails

  - by JakeTheSnake

  Some background: I'm a jack-of-all traits, one of which is programming. I learned VB6 through Excel and PHP for creating websites and so far it's worked out just fine for me. I'm not CS major or even mathematically inclined - logic is what interests me. Current status: I'm willing to learn new and more powerful languages; my first foray into such a route is learning Ruby. I went to the main Ruby website and did the interactive intro. (by the way, I'm currently getting redirected to google.com when I try the link...it's happening to other websites as well...is my computer infected?) I liked what I learned and wanted to get started using Ruby to create websites. I downloaded InstantRails and installed it; everything so far has been fine - the program starts up just fine, and I can test some Ruby code in the console. However my troubles begin when I try and view a web page with Ruby code present. Lastly, my problem: As in PHP, I can browse to the .php file directly and through using PHP tags and some simple 'echo' statements I can be on my way in making dynamic web pages. However with the InstantRails app working, accessing a .rb or .rhtml page doesn't produce similar results. I made a simple text file named 'test.rb' and put basic HTML tags in there (html, head, body) and the Ruby tags <%= and % with some ruby code inside. The web page actually shows the tags and the code - as if it's all just plain HTML. I take it Ruby isn't parsing the page before it is displayed to the user, but this is where my lack of understanding of the Ruby environment stops me short. Where do I go from here?

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• Browser-based application or stand-alone GUI app?

  - by crystalattice

  I'm sure this has been asked before, but I can't find it. What are the benefits/limitations of using a browser-based interface for a stand-alone application vs. using a normal GUI framework? I'm working on a Python program currently implement with wxPython for the GUI. The application is simply user-entry forms and dialogs. I am considering moving to PyQt because of the widgets it has (for future expansion), then I realized I could probably just use a browser to do much of the same stuff. The application currently doesn't require Internet access, though it's a possibility in the future. I was thinking of using Karrigell for the web framework if I go browser-based. Edit For clarification, as of right now the application would be browser-based, not web-based. All the information would be stored locally on the client computer; no server calls would need to be made and no Internet access required (it may come later though). It would simply be a browser GUI instead of a wxPython/PyQt GUI. Hope that makes sense.

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• How can I convert a bunch of files from ISO-8859-1 to UTF-8 using Perl?

  - by tau

  I have several documents I need to convert from ISO-8859-1 to UTF-8 (without the BOM of course). This is the issue though. I have so many of these documents (it is actually a mix of documents, some UTF-8 and some ISO-8859-1) that I need an automated way of converting them. Unfortunately I only have ActivePerl installed and don't know much about encoding in that language. I may be able to install PHP, but I am not sure as this is not my personal computer. Just so you know, I use Scite or Notepad++, but both do not convert correctly. For example, if I open a document in Czech that contains the character "ž" and go to the "Convert to UTF-8" option in Notepad++, it incorrectly converts it to an unreadable character. There is a way I CAN convert them, but it is tedious. If I open the document with the special characters and copy the document to Windows clipboard, then paste it into a UTF-8 document and save it, it is okay. This is too tedious (opening every file and copying/pasting into a new document) for the amount of documents I have. Any ideas? Thanks!!!

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