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  • Java for loop with multiple incrementers

    - by user2517280
    Im writing a program which combines the RGB pixel values for 3 images, e.g. red pixel of image 1, green pixel of image 2 and blue pixel of image 3 and I want to then create a final image of it. Im using the code below, but this seems to be incrementing x2 and x3 whilst x1 is the same, i.e. not giving the right pixel value for same co-ordinate for each image. for (int x = 0; x < image.getWidth(); x++) { for (int x2 = 0; x2 < image2.getWidth(); x2++) { for (int x3 = 0; x3 < image3.getWidth(); x3++) { for (int y = 0; y < image.getHeight(); y++) { for (int y2 = 0; y2 < image2.getHeight(); y2++) { for (int y3 = 0; y3 < image3.getHeight(); y3++) { So I was wondering if anyone can tell me how to iterate through each of the 3 images on the same co-ordinate, so for example read 1, 1 of each image and record the red, green and blue value accordingly. Apologies if it doesnt make complete sense, its a bit hard to explain. I can iterate the values for one image fine but when I add in another, things start to go a bit wrong as obviously its quite a bit more complicated! I was thinking it might be easier to create an array and replace the according values in that just not sure how to do that effectively either. Thanks

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  • Retrieve POST data without knowing exact number of fields

    - by James
    Hi all! I'm creating an online poll from scratch which will be held in a database. I'm working on getting a system set up so someone can create a new poll. I will be having the user fill out a simple HTML form with the Questions and Answers (there may be several answers). The user will be able to add multiple questions and multiple answers for each question. As the total number of questions and answers will be decided by the user, I need to create some clever PHP to cater for this - however many there are. When dealing with a static number of questions, it's simple. But I'm having trouble thinking of a way to get all the POST data into individual PHP variables so I can process them. I was thinking of using a foreach loop, anyone got any ideas? Sorry for the long winded description! If anyone needs anything clarified, I'd be happy to do so. My problem is that I can't get my head around how to deal with the POST values when I don't know exactly which element of the array will contain what. If things were static with a set number of questions and answers, I'd know $_POST[0] was Question1, etc Thank you! =)

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  • "Permission denied" with Internet Explorer and jQuery

    - by rallex
    I try to do an AJAX call with jQuery and $.post in Internet Explorer, but all I get is an error saying "Permission denied". The problem is kinda weird since it occurs only when I access a page after I was on any other page. For instance I type the URL in the adress line and let IE load the page. Then I click on a button so the script should start loading JSON data. (The script providing the data lies on the same server and I access it with a relative URL, so using a different domain is not the problem here. Even tried to use a absolute URL with the same host part.) But when I refresh the page then and try it again it works! Same thing when I come to that page from another page. At first nothing works, but when I click "refresh" everything is fine. IE gives me the error message "Permission denied" while in every other browser I don't notice this behaviour. Since I have tried many things and still cannot imagine where the problem lies I'd like to ask you what you think the problem might be?

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  • How to be a better software designer

    - by Bmw
    I feel as if I am a hack programmer. I do things over and over again until they finally work. I copy/paste code. I don't think about why something makes sense, if it works I go with it. I have my undergraduate in computer science, and I've done this the entire time. Somehow I made it through the degree by doing this and now I'm in my second year of programming professionally and I am still able to do this and get away with it. Here's the thing, I don't want to be this way anymore. I am not proud of the work I do, I feel like I'm just a copy/paste programmer. How do I become better? I want to be able to design something on my own without copying code. Have you ever been in this situation, if so how did you move beyond it to become a better programmer? To add some background about myself, I started as an asp.net c# programmer, now I'm doing vbscript (which actually makes my tendency to copy/paste/hack a lot worse I must say!) with classic asp…

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  • Displaying count for current_user 'likes' on a 'question' in questions/show.html.erb view

    - by bgadoci
    I have an application that allows for users to create questions, create answers to questions, and 'like' answers of others. When a current_user lands on the /views/questions/show.html.erb page I am trying to display the total 'likes' for all answers on that question, for the current_user. In my Likes table I am collecting the question_id, site_id and the user_id and I have the appropriate associations set up between user, question, answers and likes. I think I just need to call this information the right way, which I can't seem to figure out. All of the below is taking place in the /views/questions/show.html.erb page. I have tried the following: <% div_for current_user do %> You have liked this question <%= @question.likes.count %> times <% end %> Which returns all the 'likes' for the question but not filtered by current_user You have liked this question <%= current_user.question.likes.count %> times Which gives an error of 'undefined method `question' You have liked this question <%= @question.current_user.likes.count %> times Which gives an error of 'undefined method `current_user' I have tried a couple of other things but they don't make as much sense as the above to me. What am I missing?

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  • Does the Java Memory Model (JSR-133) imply that entering a monitor flushes the CPU data cache(s)?

    - by Durandal
    There is something that bugs me with the Java memory model (if i even understand everything correctly). If there are two threads A and B, there are no guarantees that B will ever see a value written by A, unless both A and B synchronize on the same monitor. For any system architecture that guarantees cache coherency between threads, there is no problem. But if the architecture does not support cache coherency in hardware, this essentially means that whenever a thread enters a monitor, all memory changes made before must be commited to main memory, and the cache must be invalidated. And it needs to be the entire data cache, not just a few lines, since the monitor has no information which variables in memory it guards. But that would surely impact performance of any application that needs to synchronize frequently (especially things like job queues with short running jobs). So can Java work reasonably well on architectures without hardware cache-coherency? If not, why doesn't the memory model make stronger guarantees about visibility? Wouldn't it be more efficient if the language would require information what is guarded by a monitor? As i see it the memory model gives us the worst of both worlds, the absolute need to synchronize, even if cache coherency is guaranteed in hardware, and on the other hand bad performance on incoherent architectures (full cache flushes). So shouldn't it be more strict (require information what is guarded by a monitor) or more lose and restrict potential platforms to cache-coherent architectures? As it is now, it doesn't make too much sense to me. Can somebody clear up why this specific memory model was choosen? EDIT: My use of strict and lose was a bad choice in retrospect. I used "strict" for the case where less guarantees are made and "lose" for the opposite. To avoid confusion, its probably better to speak in terms of stronger or weaker guarantees.

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  • Java Equivalent of C++ .dll?

    - by Matt D
    So, I've been programming for a while now, but since I haven't worked on many larger, modular projects, I haven't come across this issue before. I know what a .dll is in C++, and how they are used. But every time I've seen similar things in Java, they've always been packaged with source code. For instance, what would I do if I wanted to give a Java library to someone else, but not expose the source code? Instead of the source, I would just give a library as well as a Javadoc, or something along those lines, with the public methods/functions, to another programmer who could then implement them in their own Java code. For instance, if I wanted to create a SAX parser that could be "borrowed" by another programmer, but (for some reason--can't think of one in this specific example lol) I don't want to expose my source. Maybe there's a login involved that I don't want exploited--I don't know. But what would be the Java way of doing this? With C++, .dll files make it much easier, but I have never run into a Java equivalent so far. (I'm pretty new to Java, and a pretty new "real-world" programmer, in general as well)

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  • codeigniter cron job with http access

    - by user1313850
    Sorry if this is a duplicate question...I've searched around and found similar advice but nothing that helps my exact problem. And please excuse the noob questions, CRON is a new thing for me. I have a codeigniter script that scrapes the html DOM of another site and stores some of that in a database. I'd like to run this script at a regular interval. This has lead me to looking into cron jobs. The page I have is at myserver.com/index.php/update I realize I can run a cron job with curl and run this page. If I want to be a bit more secure I can put a string at the end like: myserver.com/index.php/update/asdfh2784fufds And check for that in my CI controller. This seems like it would be mostly secure, but doesn't seem like the "right" way to do things. I've looked into running CI from the command line, and can execute basic pages like: php index.php mycontroller But when I try to do: php index.php update It doesn't work. I suspect this is because it needs to use HTTP to scrape the DOM of the outside page. So, my question: How do I securely run a codeigniter script with a cron job that needs HTTP access?

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  • jQuery UI Calendar displays too large, would like the demo size???

    - by Phill Pafford
    So I downloaded a custom themed UI for jQuery and added the calendar control to my sight (Example: link text). In the example it shows/displays the size I would like but on my webpage it's about twice the size. why??? I do have a ton of other CSS but I don't have control over the look and feel of the page (Can't touch current CSS, MEH!!). Is there a way to get the demo look on my site? I think this is the code that jQuery UI has that might be complicating things /* Component containers ----------------------------------*/ .ui-widget { font-family: Arial, Helvetica, Verdana, sans-serif; font-size: 1.1em; } .ui-widget input, .ui-widget select, .ui-widget textarea, .ui-widget button { font-family: Arial, Helvetica, Verdana, sans-serif; font-size: 1em; } .ui-widget-content { border: 1px solid #B9C4CE; background: #ffffff url(../images/ui-bg_flat_75_ffffff_40x100.png) 50% 50% repeat-x; color: #616161; } .ui-widget-content a { color: #616161; } .ui-widget-header { border: 1px solid #467AA7; background: #467AA7 url(../images/ui-bg_highlight-soft_75_467AA7_1x100.png) 50% 50% repeat-x; color: #fff; font-weight: bold; } .ui-widget-header a { color: #fff; } It's part of the Custom UI CSS

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  • Is a web-server (e.g servlets) a good solution for an IM server?

    - by John
    I'm looking at a new app, broadly speaking an IM application with a strong client-server model - all communications go through a server so they can be logged centrally. The server will be Java in some form, clients could at this point be anything from a .NET Desktop app to Flex/Silverlight, to a simple web-interface using JS/AJAX. I had anticipated doing the server using standard J2EE so I get a thread-safe, multi-user server for 'free'... to make things simple let's say using Servlets (but in practice SpringMVC would be likely). This all seemed very neat but I'm concerned if the stateless nature of Servlets is the best approach. If my memory of servlets (been a year or two) is right, each time a client sent a HTTP request, typically a new message entered by the user, the servlet could not assume it had the user/chat in memory and might have to get it from the DB... regardless it has to look it up. Then it either has to use some PUSH system to inform other members of the chat, or cache that there are new messages, for other clients who poll the server using AJAX or similar - and when they poll it again has to lookup the chat, including new messages, and send the new data. I'm wondering if a better system would be the server is running core Java, and implements a socket-based communication with clients. This allows much more immediate data transfer and is more flexible if say the IM client included some game you could play. But then you're writing a custom server and sockets don't sound very friendly to a browser-based client on current browsers. Am I missing some big piece of the puzzle here, it kind of feels like I am? Perhaps a better way to ask the question would simply be "if the client was browser-based using HTML/JS and had to run on IE7+,FF2+ (i.e no HTML5), how would you implement the server?" edit: if you are going to suggest using XMPP, I have been trying to get my head around this in another question, so please consider if that's a more appropriate place to discuss this specifically.

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  • Sharing code between two or more rails apps... alternatives to git submodules?

    - by jtgameover
    We have two separate rails_app, foo/ and bar/ (separate for good reason). They both depend on some models, etc. in a common/ folder, currently parallel to foo and bar. Our current svn setup uses svn:externals to share common/. This weekend we wanted to try out git. After much research, it appears that the "kosher" way to solve this is using git submodule. We got that working after separating foo,bar,common into separate repositories, but then realized all the strings attached: Always commit the submodule before committing the parent. Always push the submodule before pushing the parent. Make sure that the submodule's HEAD points to a branch before committing to it. (If you're a bash user, I recommend using git-completion to put the current branch name in your prompt.) Always run 'git submodule update' after switching branches or pulling changes. All these gotchas complicate things further than add,commit,push. We're looking for simpler ways to share common in git. This guy seems to have success using the git subtree extension, but that deviates from standard gitand still doesn't look that simple. Is this the best we can do given our project structure? I don't know enough about rails plugins/engines, but that seems like a possible RoR-ish way to share libraries. Thanks in advance.

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  • Running a process at the Windows 7 Welcome Screen

    - by peelman
    So here's the scoop: I wrote a tiny C# app a while back that displays the hostname, ip address, imaged date, thaw status (we use DeepFreeze), current domain, and the current date/time, to display on the welcome screen of our Windows 7 lab machines. This was to replace our previous information block, which was set statically at startup and actually embedded text into the background, with something a little more dynamic and functional. The app uses a Timer to update the ip address, deepfreeze status, and clock every second, and it checks to see if a user has logged in and kills itself when it detects such a condition. If we just run it, via our startup script (set via group policy), it holds the script open and the machine never makes it to the login prompt. If we use something like the start or cmd commands to start it off under a separate shell/process, it runs until the startup script finishes, at which point Windows seems to clean up any and all child processes of the script. We're currently able to bypass that using psexec -s -d -i -x to fire it off, which lets it persist after the startup script is completed, but can be incredibly slow, adding anywhere between 5 seconds and over a minute to our startup time. We have experimented with using another C# app to start the process, via the Process class, using WMI Calls (Win32_Process and Win32_ProcessStartup) with various startup flags, etc, but all end with the same result of the script finishing and the info block process getting killed. I tinkered with rewriting the app as a service, but services were never designed to interact with the desktop, let alone the login window, and getting things operating in the right context never really seemed to work out. So for the question: Does anybody have a good way to accomplish this? Launch a task so that it would be independent of the startup script and run on top of the welcome screen?

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  • Bootstrap inline button dropdown within <p> jumbotron

    - by C.B.
    Currently I have a jumbotron setup with some paragraph text, and I would like to stick a button dropdown inline with the text. Dropdown button <span class="btn-group"> <button type="button" class="btn btn-default dropdown-toggle" data-toggle="dropdown"> Button... <span class="caret"></span> </button> <ul class="dropdown-menu" role="menu"> <li><a href="#">Opt 1</a></li> <li><a href="#">Opt 2</a></li> </ul> </span> Jumbotron <div class="jumbotron"> <h1>Hello!</h1> <p>Welcome</p> <p>Another paragraph <!-- dropdown is here --> </p> </div> <!-- jumbotron --> If the dropdown is within the <p> tag, it does not "dropdown" (but renders). If it is outside of the <p> tag it functions fine, but I would like it to be inline with the text and need the text to be in the <p> tag to get the style. Any ideas? Things to note -- If I replace the <span> tags with <div> tags, it will work fine within the <p> tags, but won't be inline.

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  • DCI: How to implement Context with Dependency Injection?

    - by ciscoheat
    Most examples of a DCI Context are implemented as a Command pattern. When using Dependency Injection though, it's useful to have the dependencies injected in the constructor and send the parameters into the executing method. Compare the Command pattern class: public class SomeContext { private readonly SomeRole _someRole; private readonly IRepository<User> _userRepository; // Everything goes into the constructor for a true encapsuled command. public SomeContext(SomeRole someRole, IRepository<User> userRepository) { _someRole = someRole; _userRepository = userRepository; } public void Execute() { _someRole.DoStuff(_userRepository); } } With the Dependency injected class: public class SomeContext { private readonly IRepository<User> _userRepository; // Only what can be injected using the DI provider. public SomeContext(IRepository<User> userRepository) { _userRepository = userRepository; } // Parameters from the executing method public void Execute(SomeRole someRole) { someRole.DoStuff(_userRepository); } } The last one seems a bit nicer, but I've never seen it implemented like this so I'm curious if there are any things to consider.

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  • Importing a Mercurial repository automatically (e.g. SVN Externals)

    - by dawmail333
    I have a project that I am developing built off CodeIgniter. The main part of the project is a private system I am creating, but I want to add it to source control, to gain all the associated goodies. Now I'm using Mercurial, so I did the whole hg init bit, so I've got the repository set up. Now, one of the things I've done is to make a library for CodeIgniter, which I use in this project. Now I want to make this library open, so I need a separate repo for that. For anyone unfamiliar with CodeIgniter library development, here's a reference: application /config <- configuration files /libraries <- library logic in here Now I will probably develop a few more libraries in the course of this project, so I can't just dump a repo in the application folder without clumping them all together. What I did was this: dev/ci/library <- library here dev/project <- project here Now in both of those folders, I have made a repository. What I want to do is make the project repository automatically reference the library repository, so I can have a private and a public repository, as I explained earlier. The main way to do this, I have read, is to use subrepositories, but I can only find examples on nested ones (which are unclear anyway, I find). How do I make it reference another repository like svn:externals?

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  • Deserialization of a DataSet... deal with column name changes? how to migrate data from one column to another?

    - by Brian Kennedy
    So, we wanted to slightly generalize a couple columns in our typed dataset... basically dropped a foreign key constraint and then wanted to change a couple column names to better reflect their new state. All that is easy. The problem is that our users may have serialized out the old version of the DataSet as XML. We want to be able to read those old XML files and deserialize them into the revised DataSet. It seems that would be a fairly common desire... but I haven't yet figured out the right thing to search the internet for. One possible solution would seem to be some way to give a DataColumn an alias or alternate name such that when it reads the old column name, it knows that data can be read into the column with the new column name. I can find no support for any such thing. Another approach would seem to be an "after deserialization" method of some sort... so, I would let it read in the old column values into a normal DataColumn with that name, and then in the "after deserialization" method I would just move the data from the obsolete column into the new column, and then delete the old columns. That would seem to generalize to many other situations... and having such events or hooks is pretty common in ADO.NET. But I have looked for such a hook and haven't yet found it. If no "after deserialization" hook, it would seem I ought to be able to override ReadXml or ReadXmlSerializable methods to call the base and then do my "after" stuff to fix up old data into new. But it does not appear that is possible. Soooo, I have to think backward compatibility with old serialized DataSets and simple data migration would be a well-solved problem... so, trying to reinvent that wheel seems silly. But so far, I haven't seemed to find any documentation on doing those things. Suggestions? What is best practice for this?

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  • Android Plugin for Eclipse problem

    - by tbneff
    I am using a laptop with Windows 7 Home Prem x64. I have installed Java JDK1.6.0_18 and Eclipse Gallileo. I have downloaded and installed the latest version of Android SDK with several Platforms loaded and a AVD defined. I can install the Android Eclipse plugin from the remote site stated in the instructions. The plugin installation performs without any errors and I can verify that the plugins are indeed installed. My problem begins when I go to Windows - Preferences, there is no Android section to configure. And when I go to File - New - Project, there is no Android Project to choose. I have uninstalled the plugin and reinstalled at least 10 times, trying different things and still no luck. I originally had the 64 bit version of the JDK installed, but removed it and installed the 32 bit version. Has anyone heard of this type of problem? Is it because I am using Windows 7? Thanks for any help. tbneff

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  • Displaying data from linked tables in netbeans JTable

    - by Darc
    I have been writing in java for a few months now and have just started using netbeans. I have spent all day today trying to work out how to connect to an SQL database and display data from 2 tables (ie display the data from from a select statement with an inner join) in a JTable. I have tried using JPQL with the following statment SELECT j, cust.name FROM Job j JOIN j.jobnumber cust where the job table has a field called customer that references id in the customer table. This throws the exception: Caused by: Exception [TOPLINK-8029] (Oracle TopLink Essentials - 2.0.1 (Build b09d-fcs (12/06/2007))): oracle.toplink.essentials.exceptions.EJBQLException Exception Description: Error compiling the query [SELECT j, cust.name FROM Job j JOIN j.jobnumber cust], line 1, column 11: invalid navigation expression [cust.name], cannot navigate expression [cust] of type [java.lang.Integer] inside a query. at oracle.toplink.essentials.exceptions.EJBQLException.invalidNavigation(EJBQLException.java:430) What am i doing wrong? Can anyone point me to some examples of how to make a linked table java application? I am still in the very early stages of development so a complete change is not out of the question if using a mysql database isnt the best way to go about things thanks

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  • Need help optimizing this Django aggregate query

    - by Chris Lawlor
    I have the following model class Plugin(models.Model): name = models.CharField(max_length=50) # more fields which represents a plugin that can be downloaded from my site. To track downloads, I have class Download(models.Model): plugin = models.ForiegnKey(Plugin) timestamp = models.DateTimeField(auto_now=True) So to build a view showing plugins sorted by downloads, I have the following query: # pbd is plugins by download - commented here to prevent scrolling pbd = Plugin.objects.annotate(dl_total=Count('download')).order_by('-dl_total') Which works, but is very slow. With only 1,000 plugins, the avg. response is 3.6 - 3.9 seconds (devserver with local PostgreSQL db), where a similar view with a much simpler query (sorting by plugin release date) takes 160 ms or so. I'm looking for suggestions on how to optimize this query. I'd really prefer that the query return Plugin objects (as opposed to using values) since I'm sharing the same template for the other views (Plugins by rating, Plugins by release date, etc.), so the template is expecting Plugin objects - plus I'm not sure how I would get things like the absolute_url without a reference to the plugin object. Or, is my whole approach doomed to failure? Is there a better way to track downloads? I ultimately want to provide users some nice download statistics for the plugins they've uploaded - like downloads per day/week/month. Will I have to calculate and cache Downloads at some point? EDIT: In my test dataset, there are somewhere between 10-20 Download instances per Plugin - in production I expect this number would be much higher for many of the plugins.

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  • How to use Node.js to build pages that are a mix between static and dynamic content?

    - by edt
    All pages on my 5 page site should be output using a Node.js server. Most of the page content is static. At the bottom of each page, there is a bit of dynamic content. My node.js code currently looks like: var http = require('http'); http.createServer(function (request, response) { console.log('request starting...'); response.writeHead(200, { 'Content-Type': 'text/html' }); var html = '<!DOCTYPE html><html><head><title>My Title</title></head><body>'; html += 'Some more static content'; html += 'Some more static content'; html += 'Some more static content'; html += 'Some dynamic content'; html += '</body></html>'; response.end(html, 'utf-8'); }).listen(38316); I'm sure there are numerous things wrong about this example. Please enlighten me! For example: How can I add static content to the page without storing it in a string as a variable value with += numerous times? What is the best practices way to build a small site in Node.js where all pages are a mix between static and dynamic content?

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  • How do I force MyEclipse to hot-deploy a JavaScript file to my JBoss instance?

    - by Mike Cialowicz
    I'm having trouble with MyEclipse 7.1.1 hot-deployment of files to my JBoss 4 server. The problem is this: while my server is running, I can make changes to various JAVA and HTML files, which are then hot-deployed immediately (I can see the changes reflected in my browser when I refresh the page). However, while working on a particular JavaScript file, my changes are not being hot-deployed. This makes it very difficult to work on and debug this file, since I have to stop my server, redeploy, and start it again each time I make changes. This is a new problem - it didn't used to happen with this file, so I think something got screwed up in my MyEclipse configuration. I've verified that my projects (JBoss 4 instances) are all set up in "Exploded" mode for hot-deployment. I'm also 99% sure that this isn't an issue with my browser, since I always refresh with CTRL+F5, and I've tried a number of things like clearing my browser cache to get the currently deployed version of the file. I've also tried doing a "clean" on the project while the server is running, and that didn't force a deployment either. Any sort of solution would be helpful. I'd love for MyEclipse to deploy the file automatically, but I'm also open to manually forcing hot-deployment of this particular file while I work on it. Thank you.

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  • C# - Is it possible to start my project with a class instead of a form?

    - by Irro
    I want my project to be started through an class instead of a form, is there any way to do this? Or to be more precise is there any good way to make sure that the first class, except Program, that is started isn't a form-class. I tried to change to my class in Program.main() but it looks like Application.run() needs a ApplicationContext. I guess that I could change the Program-class to start another class and let that class start the form with Application.run() but I think that it will cause a lot of problem since I don't want the same form to be started first each time and Application.run() have to be used at least once and at most once. So I think it will be hard to keep track of if Application.run() has been used or not. Another question that might be even more important; Is this a good way to do things in .net? The reason I want to do so is because I want to create some sort of MVC project where the class I want to start with is the controller and all forms I'll use will be views.

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  • in haskell, why do I need to specify type constraints, why can't the compiler figure them out?

    - by Steve
    Consider the function, add a b = a + b This works: *Main> add 1 2 3 However, if I add a type signature specifying that I want to add things of the same type: add :: a -> a -> a add a b = a + b I get an error: test.hs:3:10: Could not deduce (Num a) from the context () arising from a use of `+' at test.hs:3:10-14 Possible fix: add (Num a) to the context of the type signature for `add' In the expression: a + b In the definition of `add': add a b = a + b So GHC clearly can deduce that I need the Num type constraint, since it just told me: add :: Num a => a -> a -> a add a b = a + b Works. Why does GHC require me to add the type constraint? If I'm doing generic programming, why can't it just work for anything that knows how to use the + operator? In C++ template programming, you can do this easily: #include <string> #include <cstdio> using namespace std; template<typename T> T add(T a, T b) { return a + b; } int main() { printf("%d, %f, %s\n", add(1, 2), add(1.0, 3.4), add(string("foo"), string("bar")).c_str()); return 0; } The compiler figures out the types of the arguments to add and generates a version of the function for that type. There seems to be a fundamental difference in Haskell's approach, can you describe it, and discuss the trade-offs? It seems to me like it would be resolved if GHC simply filled in the type constraint for me, since it obviously decided it was needed. Still, why the type constraint at all? Why not just compile successfully as long as the function is only used in a valid context where the arguments are in Num? Thank you.

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  • Managing server instance identity on EC2

    - by kikibobo
    I recently brought up a cluster on EC2, and I felt like I had to invent a lot of things. I'm wondering what kinds of tools, patterns, ideas are out there for how to deal with this. Some context: I had 3 different kinds of servers, so first I created AMIs for each of them. The first AMI had zookeeper, so step one in deploying the system was to get the zookeeper server running. My script then made a note of the mapping between EC2's completely arbitrary and unpredictable hostnames, and the zookeeper server. Then as I brought up new instances of the other 2 kinds of servers, the first thing I would do is ssh to the new server, and add the zookeeper server to its /etc/hosts file. Then as the server software on each instance starts up, it can find zookeeper. Obviously this is a problem that lots of people have to solve, and it probably works a little bit differently in different clouds. Are there products that address this concept? I was pretty surprised that EC2 didn't provide some kind of way to tie your own name to its name. Thanks for any ideas.

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  • INSERT INTO ...SELECT syntax error in join operator

    - by user1477356
    I'm trying to write a shopping basket into a order + orderline in a sql database from C# asp.net. the orderline will contain a ordernumber, total price, productid, quantity etc. for every item in the basket. The order itself will contain the ordernumber as primary key and will be linked to the different lines through it. Everything worked fine yesterday, but now as i tried to use a SELECT command in the insert into statement to get things more dynamic i'm getting the above described syntax error. Does anybody know what's wrong with this statement: INSERT INTO [order] (klant_id,totaalprijs,btw,subtotaal,verzendkosten) SELECT klant.id , SUM(orderregel.totaalprijs) , SUM(orderregel.btw) , SUM(orderregel.totaalprijs) - SUM(orderregel.btw) , 7.50 FROM orderregel INNER JOIN klant ON [order].klant_id = klant.id WHERE klant.username = 'jerry' GROUP BY id; the ordernumber in the "order" table is on autonumber, in the asp codebehind there is a for each which handles the lines being written for every product, there's an index set on 0 outside of this loop and is heightened with 1 every end of it. The executenonquery of the order is only executed once at the beginning of the first loop and the lines are added after with MAX(ordernumber) as ordernumber. I hope i have provided enough information and somebody is capable of helping me. Thanks in advance!

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