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  • retrieve value from hashtable with clone of key; C#

    - by Johnny
    I would like to know if there is any possible way to retrieve an item from a hashtable using a key that is identical to the actual key, but a different object. I understand why it is probably not possible, but I would like to see if there is any tricky way to do it. My problem arises from the fact that, being as stupid as I am, I created hashtables with int[] as the keys, with the integer arrays containing indices representing spatial position. I somehow knew that I needed to create a new int[] every time I wanted to add a new entry, but neglected to think that when I generated spatial coordinate arrays later they would be worthless in retrieving the values from my hashtables. Now I am trying to decide whether to rearrange things so that I can store my values in ArrayLists, or whether to search through the list of keys in the Hashtable for the one I need every time I want to get a value, neither of the options being very cool. Unless of course there is a way to get //1 to work like //2! Thanks in advance. static void Main(string[] args) { Hashtable dog = new Hashtable(); //1 int[] man = new int[] { 5 }; dog.Add(man, "hello"); int[] cat = new int[] { 5 }; Console.WriteLine(dog.ContainsKey(cat)); //false //2 int boy = 5; dog.Add(boy, "wtf"); int kitten = 5; Console.WriteLine(dog.ContainsKey(kitten)); //true; }

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  • Is there a Scheduler/Calendar JS Widget library?

    - by Ravi Chhabra
    I am looking for some JavaScript based component to be used as a course scheduler which would be a cross between Google Calendar and the login time. I do not know if the right term for this is Course Scheduler but I shall describe this in more detail here. Course Scheduler The widget would be used to enter date and times of a course, as an example if I run a programming course 3 days a week on Mon, Tue and Wed every 7:00 am to 9:00am, 2 hours every day from 1st September to 30th November. I could answer various questions and the course data would be displayed in the calendar. It would also allow for non pattern based timings where each week is different from the other week etc. Question So would I end up creating something from scratch? Would it be sensible to use Google Calendar API for this? I did a Google search for some widgets, but I believe I need better keywords, as I could not find anything close to what I am looking for. Any tips? Commercial libraries would also work for me. Thanks.

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  • R: manipulating data.frames containing strings and booleans.

    - by Mike Dewar
    Hello. I have a data.frame in R; it's called p. Each element in the data.frame is either True or False. My variable p has, say, m rows and n columns. For every row there is strictly only one TRUE element. It also has column names, which are strings. What I would like to do is the following: For every row in p I see a TRUE I would like to replace with the name of the corresponding column I would then like to collapse the data.frame, which now contains FALSEs and column names, to a single vector, which will have m elements. I would like to do this in an R-thonic manner, so as to continue my enlightenment in R and contribute to a world without for-loops. I can do step 1 using the following for loop: for (i in seq(length(colnames(p)))) { p[p[,i]==TRUE,i]=colnames(p)[i] } but theres's no beauty here and I have totally subscribed to this for-loops-in-R-are-probably-wrong mentality. Maybe wrong is too strong but they're certainly not great. I don't really know how to do step 2. I kind of hoped that the sum of a string and FALSE would return the string but it doesn't. I kind of hoped I could use an OR operator of some kind but can't quite figure that out (Python responds to False or 'bob' with 'bob'). Hence, yet again, I appeal to you beautiful Rstats people for help!

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  • RegisterClientScriptInclude doesn't work for some reason...

    - by Andrew
    Hey, I've spent at least 2 days trying anything and googling this...but for some reason I can't get RegisterClientScriptInclude to work the way everyone else has it working? First off, I am usting .NET 3.5 Ajax,...and I am including javascript in my partial page refreshes...using this code: ScriptManager.RegisterClientScriptBlock(this, typeof(Page), "MyClientCode", script, true); It works perfectly, my javascript code contained in the script variable is included every partial refresh. The javascript in script is actually quite extensive though, and I would like to store it in a .js file,..so logically I make a .js file and try to include it using RegisterClientScriptInclude ...however i can't for the life of my get this to work. here's the exact code: ScriptManager.RegisterClientScriptInclude(this, typeof(Page), "mytestscript", "/js/testscript.js"); the testscript.js file is only included in FULL page refreshes...ie. when I load the page, or do a full postback....i can't get the file to be included in partial refreshes...have no idea why..when viewing the ajax POST in firebug I don't see a difference whether I include the file or not.... both of the ScriptManager Includes are being ran from the exact same place in "Page_Load"...so they should execute every partial refresh (but only the ScriptBlock does). anyways,..any help or ideas,..or further ways I can trouble shoot this problem, would be appreciated. Thanks, Andrew

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  • Single log file for multiple webapps

    - by Ashish Aggarwal
    In my tomcat there are multiple webapps deployed and they communicate with each other. Currently they all have their own log file. But when there is some issue comes from call I have to 1st check with the app to whom I made a call and check log file of respective apps involved in the call. So I want that, as all apps is deployed in same tomcat and sharing a common log4j, if a call made to any app then all logs should be in a single log file and no matters how my webapps are involved all error comes from any webapp during the call should be in a single log file. I have no idea how can I achieve this. So any help is appreciable. Edited: I think my question is not cleared so updated with use case: I have three webapps A, B, C having logs files as A.log, B.log and C.log. I made two calls. 1st one to A (that internally calls C) and 2nd to B (that internally calls C). Now logging of first call must be in A.log (with the logs of every step performed inside the webapp c) and second call must be in B.log (with the logs of every step performed inside the webapp c).

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  • Interface vs Abstract Class (general OO)

    - by Kave
    Hi, I have had recently two telephone interviews where I've been asked about the differences between an Interface and an Abstract class. I have explained every aspect of them I could think of, but it seems they are waiting for me to mention something specific, and I dont know what it is. From my experience I think the following is true, if i am missing a major point please let me know: Interface: Every single Method declared in an Interface will have to be implemented in the subclass. Only Events, Delegates, Properties (C#) and Methods can exist in a Interface. A class can implement multiple Interfaces. Abstract Class Only Abstract methods have to be implemented by the subclass. An Abstract class can have normal methods with implementations. Abstract class can also have class variables beside Events, Delegates, Properties and Methods. A class can only implement one abstract class only due non-existence of Multi-inheritance in C#. 1) After all that the interviewer came up with the question What if you had an Abstract class with only abstract methods, how would that be different from an interface? I didnt know the answer but I think its the inheritance as mentioned above right? 2) An another interviewer asked me what if you had a Public variable inside the interface, how would that be different than in Abstract Class? I insisted you can't have a public variable inside an interface. I didn't know what he wanted to hear but he wasn't satisfied either. Many Thanks for clarification, Kave See Also: When to use an interface instead of an abstract class and vice versa Interfaces vs. Abstract Classes How do you decide between using an Abstract Class and an Interface?

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  • Multiple jQuery UI buttons with same ID

    - by Mark Nolan
    There might be a really simple solution to this question, but i just don't see it! I have a page with a list of items. every item has the same jquery ui button (its inside a dialog and adds that item to a list). i identify the item via the parenting DIV holding the DB id. So far so good... The Problem is only the first button on the list works! The second, third etc. buttons don't show any reaction at all. The buttons all have the same id - as the list is dynamic and the same action is triggered with every click. Only the parenting ID changes. Heres the display part: <div id="2"> <div id="56"> <button id="add-audio-file" class="ui-button ui-state-default ui-corner-all">betty_2.mp3</button> </div> </div> <div id="2"> <div id="57"> <button id="add-audio-file" class="ui-button ui-state-default ui-corner-all">betty_3.mp3</button> </div> </div> And here comes the js Part: $('#add-audio-file').click(function() { assetID = $(this).parent('div').attr('id'); pageID = $(this).parent('div').parent('div').attr('id'); $.post( "modules/portfolio/serialize.php", {id : pageID, assetid : assetID, do : "add-audio-file"}, function(data, textStatus, xhr) { $('#dialog-add-audio').dialog('close'); } ); }); I am using jquery 1.4.2 and jquery ui 1.8rc3 Any ideas?

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  • ObjectDisposedException when .Show()'ing a form that shouldn't be disposed.

    - by user320781
    ive checked out some of the other questions and obviously the best solution is to prevent the behavior that causes this issue in the first place, but the problem is very intermittent, and very un-reproduceable. I basically have a main form, with sub forms. The sub forms are shown from menus and/or buttons from the main form like so: private void myToolStripMenuItem_Click(object sender, EventArgs e) { try { xDataForm.Show(); xDataForm.Activate(); } catch (ObjectDisposedException) { MessageBox.Show("ERROR 10103"); ErrorLogging newLogger = new ErrorLogging("10103"); Thread errorThread = new Thread(ErrorLogging.writeErrorToLog); errorThread.Start(); } } and the sub forms are actually in the main form(for better or worse. i would actually like to change this but would be a considerable amount of time to do so): public partial class FormMainScreen : Form { Form xDataForm = new xData(); ...(lots more here) public FormMainScreen(int pCount, string pName) { InitializeComponent(); ... } ... } The Dispose function for the sub form is modified so that, the 'close' and 'X' buttons actually hide the form so we dont have to re-create it every time. When the main screen closes, it sets a "flag" to 2, so the other forms know that it is actually ok to close; protected override void Dispose(bool disposing) { if (FormMainScreen.isExiting == 2) { if (disposing && (components != null)) { components.Dispose(); } base.Dispose(disposing); } else { if (xData.ActiveForm != null) { xData.ActiveForm.Hide(); } } } So, the question is, why would this work over and over and over again flawlessly, but, literally, about every 1/1000 of the time, cause an exception, or rather, why is my form being disposed? I had a suspicion that the garbage collector was getting confused, because it occurs slightly more frequently after it has been running for many hours.

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  • How should I secure my webapp written using Wicket, Spring, and JPA?

    - by Martin
    So, I have an web-based application that is using the Wicket 1.4 framework, and it uses Spring beans, the Java Persistence API (JPA), and the OpenSessionInView pattern. I'm hoping to find a security model that is declarative, but doesn't require gobs of XML configuration -- I'd prefer annotations. Here are the options so far: Spring Security (guide) - looks complete, but every guide I find that combines it with Wicket still calls it Acegi Security, which makes me think it must be old. Wicket-Auth-Roles (guide 1 and guide 2) - Most guides recommend mixing this with Spring Security, and I love the declarative style of @Authorize("ROLE1","ROLE2",etc). I'm concerned about having to extend AuthenticatedWebApplication, since I'm already extending org.apache.wicket.protocol.http.WebApplication, and Spring is already proxying that behind org.apache.wicket.spring.SpringWebApplicationFactory. SWARM / WASP (guide) - This looks the newest (though the main contributor passed away years ago), but I hate all of the JAAS-styled text files that declare permissions for principals. I also don't like the idea of making an Action class for every single thing a user might want to do. Secure models also aren't immediately obvious to me. Plus, there isn't an Authn example. Additionally, it looks like lots of folks recommend mixing the first and second options. I can't tell what the best practice is at all, though.

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  • The Implications of Modern Day Software Development Abstractions

    - by Andreas Grech
    I am currently doing a dissertation about the implications or dangers that today's software development practices or teachings may have on the long term effects of programming. Just to make it clear: I am not attacking the use abstractions in programming. Every programmer knows that abstractions are the bases for modularity. What I want to investigate with this dissertation are the positive and negative effects abstractions can have in software development. As regards the positive, I am sure that I can find many sources that can confirm this. But what about the negative effects of abstractions? Do you have any stories to share that talk about when certain abstractions failed on you? The main concern is that many programmers today are programming against abstractions without having the faintest idea of what the abstraction is doing under-the-covers. This may very well lead to bugs and bad design. So, in you're opinion, how important is it that programmers actually know what is going below the abstractions? Taking a simple example from Joel's Back to Basics, C's strcat: void strcat( char* dest, char* src ) { while (*dest) dest++; while (*dest++ = *src++); } The above function hosts the issue that if you are doing string concatenation, the function is always starting from the beginning of the dest pointer to find the null terminator character, whereas if you write the function as follows, you will return a pointer to where the concatenated string is, which in turn allows you to pass this new pointer to the concatenation function as the *dest parameter: char* mystrcat( char* dest, char* src ) { while (*dest) dest++; while (*dest++ = *src++); return --dest; } Now this is obviously a very simple as regards abstractions, but it is the same concept I shall be investigating. Finally, what do you think about the issue that schools are preferring to teach Java instead of C and Lisp ? Can you please give your opinions and your says as regards this subject? Thank you for your time and I appreciate every comment.

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  • Applying fine-grained security to an existing application

    - by Mark
    I've inherited a reasonably large and complex ASP.NET MVC3 web application using EF Code First on SQL Server. It uses ASP.NET Membership roles with database authentication. The controller actions are secured with attributes derived from AuthorizeAttribute that map roles to actions. There are extension methods for the finer points, such as showing a particular widget to particular roles. This is works great and I have a good understanding of the current security model. I've been asked to provide finer grained security at the data level. For example a 'Customer' user can only see data (throughout the database) associated with themselves and not other Customers. The problem is that 'Customer' is only 1 of 5 different types with their own specific restrictions (each of the 9 roles is one of these 5 types). The best thing I can think of is to go through all the data repositories and extend each and every LINQ statements/query with a filter for every user type. Even if I had time for that it doesn't seem like the most elegant way. Any suggestions? I really don't know where to start with this so anything could be helpful. Many thanks.

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  • LNK 1104 error to lib file - Continues despite removing includes and links

    - by user1556594
    A link error to a lib file popped up out of the blue in a c++ application of mine after code was working fine in my last session. Error 1 error LNK1104: cannot open file '..........\Program Files (x86)\FMOD SoundSystem\FMOD Programmers API Windows\api\lib\fmodex_vc.lib' I triple checked my project directories were set up correctly to link to the lib file, that the file existed in said directory and that it was a working version of the .lib. My next step was to remove the includes to the file and the links to bypass the error and work on the rest of my code until the problem was solved. The error remains, however, despite: Commenting out absolutely every include relating to the lib. Commenting out absolutely every line of code dependant on the includes. Removing the directory from VC++ Directories in the project properties. Checking the Additional Library Directories field was also clear of references. To my understanding this should have made the library and related code virtually non-existant to the compiler. What am I missing? The library itself is fmodex_vc.lib - part of the FMOD API for providing sound to interactive applications. Again, the application was working one session, but failed to compile the next. I hadn't touched the code since so this led me to believe some aspect of VS is at fault. I'd like to avoid the time involded in re-installing if possible as I'm on the clock for a review tomorrow evening and there are a few more things I'd like to smooth out before then. If necessary, however, I won't hesitate. Very much appreciate the help.

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  • Possible to capture all events in a web browser?

    - by David
    I am working on a pet project and am at the research stage. Quick summary I am trying to intercept all form submits, onclick, and every single keydown. My library of choice is either jquery, or jquery + prototypejs. I figure I can batch up the events into a queue/stack and send it back to the server in time interval batches to keep performance relatively stable. Concerns Form submits and change's would be relatively simple.. Something like $("form :inputs").bind("change", function() { ... record event... }); But how to ensure I get precedence over the applications handlers as I have a habit of putting return false on a lot of my form handlers when there is a validation issue. As I understand it, that effectively stops the event in its tracks. My project For my smaller remote clients I will put their products onto a VPS or run it in my home data center. Currently I use a basic authentication system, given a username/password they see the website and then hopefully send me somewhat sane notes on what is broken or should be tweaked. As a better solution, I've written a simple proxy web server that does the above but allows me to have one DNS entry and then depending on credentials it makes an internal request relaying headers and re-writing URLS as needed. Every single html/text or application/* request is compressed and shoved into a sqlite table so I can partially replay what they've done. Now I am shifting to the frontend and would like to capture clicks, keydown's, and submits on everything on the page.

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  • IIS URL Rewrite rule - Default document for subdirectories

    - by Antonio Bakula
    I would like create URL rewrite rule that will set default document for my virtual folders. eg. someting like this www.domain.com/en/ -> www.domain.com/en/index.aspx www.domain.com/hr/ -> www.domain.com/hr/index.aspx www.domain.com/de/ -> www.domain.com/de/index.aspx directories en, hr, de doesn't really exists on web server they are just markers for languange used in site used by home grown http module that will rewrite path with query params. Quick solution was define rule for every single lang, something like this : <rewrite> <rewriteMaps> <rewriteMap name="Langs"> <add key="/en" value="/en/index.aspx" /> <add key="/hr" value="/hr/index.aspx" /> <add key="/de" value="/de/index.aspx" /> </rewriteMap> </rewriteMaps> <rules> But I would really like solution that would not require changes in web.config and adding rewrite rule for every languange used on particular site. Thanks !

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  • TFS: Choose which Team Project to add a solution too.

    - by Patricker
    I have a solution which I developed in VS2008 and which I am trying to add to Source Control (TFS 2010, though the issue happened in TFS 2008 as well). I have several TFS workspaces on my computer and I have access to several Team Projects. When I right click the solution in my Solution Explorer and choose the "Add Solution to Source Control" option I am never given an option of choosing which Workspace or which Team Project to add the existing solution too. VS2008 then proceeds to add it to the same team project every time. I have tried selecting an alternate workspace/team project in every window where I can see an option for it but it always adds it back to the same one. I even tried changing the name of my new workspace so that alphabetically it was the first thinking that it might be somehow related to that... no luck. I then tried goign to the Change Source Control window where you can add/remove bindings on a solution/project but that window also defaults to the same Team Project as trying to add the solution directly does... Any help would be greatly appreciated with this, maybe I'm just missing something?

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  • Is there such a thing as IMAP for podcasts?

    - by Gerrit
    Is there such a thing as IMAP for podcasts? I own a desktop, laptop, iPod, smartphone and a web-client all downloading StackOverflow Podcasts. (among others) They all tell me which episodes are available and which are already played. Everything is a horrible mess, ofcourse. My iPod is somewhat in sync with my desktop, but everything else is a random jungle. The same problem with e-mail is solved by IMAP. Every device gets content and meta-information from one server, and stays in sync with it. Per device, I can set preferences (do or do not download the complete archive including junkmail). Can we implement the IMAP approach for podcasts? Or is there a better metaphore/standard to solve this problem? How will the adoption-strategy look like? (by the way: except for the Windows smartphone, I own a full Apple-stack of products. Even then, I run into this problem) UPDATE The RSS-to-Imap link to sourceforge looks promesting, but very alpha/experimental. UPDATE 2 The one thing RSS is missing is the command/method/parameter/attribute to delete/unread items. RSS can only add, not remove. If RSS(N+1) (3?) could add a value for unread="true|false", it would be solved. If I cache all my RSS-feeds on my own server, and add the attribute myself, I only would have to convince iTunes and every other client to respect that.

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  • Glassfish 3: How do I get and use a developers build so I can navigate a stack trace including Glas

    - by Thorbjørn Ravn Andersen
    I am migrating a JSF 1.1 application to JEE 6 Web profile, and doing it in steps. I am in the process of moving from JSP with JSF 1.1 to Facelets under JSF 1.2 using the jsf-facelets.jar for JSF 1.2, and received an "interesting" stack trace when trying to lookup a key in a Map using a "{Bean.foo.map.key}" where the stacktrace complained about "key" not being a valid integer. (After code introspection I am workarounding it using a number as the key). That bug is not what this question is about. In such a situation it is essential to be able to navigate the source of every line in the stack trace. In Eclipse I normally attach a source jar to every jar on the build path, but in this particular case the Glassfish server adapter creates a library automatically containing the jars. Also there is to my knowledge no debug build of Glassfish where sources are included in the bundle. Glassfish is a non-trivial Maven project, and a bit picky too. I am not very familiar with maven, but have managed to checkout the code from Subversion and build it for the 3.0 tag according to http://wiki.glassfish.java.net/Wiki.jsp?page=V3FullBuildInstructions#section-V3FullBuildInstructions-CheckoutTheWorkspace - it appears to be the code corresponding to the official released 3.0 version. After finishing the "mvn -U install" part, I have then tried to create Eclipse projects by first using "mvn -DdownloadSources=true eclipse:eclipse" and then import them in Eclipse JEE 3.5.2 and specifying the M2_REPO variable but many of the projects still have compilation errors, and I cannot locate any instructions from Oracle about how to do this. I'd appreciate some help in just getting a functional IDE workspace reflecting the 3.0 version of Glassfish. I have Eclipse 3.5.2, Netbeans 6.8 and 6.9 beta, and IntelliJ IDEA 9, and Linux/Windows/OS X do do it on.

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  • How to get to the key name of a referenced entity property from an entity instance without a datastore read in google app engine?

    - by Sumeet Pareek
    Consider I have the following models - class Team(db.Model): # say I have just 5 teams name = db.StringProperty() class Player(db.Model): # say I have thousands of players name = db.StringProperty() team = db.ReferenceProperty(Team, collection_name="player_set") Key name for each Team entity = 'team_' , and for each Player entity = 'player_' By some prior arrangement I have a Team entity's (key_name, name) mapping available to me. For example (team_01, United States Of America), (team_02, Russia) etc I have to show all the players and their teams on a page. One way of doing this would be - players = Player.all().fetch(1000) # This is 1 DB read for player in players: # This will iterate 1000 times self.response.out.write(player.name) # This is obviously not a DB read self.response.out.write(player.team.name) #This is a total of 1x1000 = 1000 DB reads That is a 1001 DB reads for a silly thing. The interesting part is that when I do a db.to_dict() on players, it shows that for every player in that list there is 'name' of the player and there is the 'key_name' of the team available too. So how can I do the below ?? players = Player.all().fetch(1000) # This is 1 DB read for player in players: # This will iterate 1000 times self.response.out.write(player.name) # This is obviously not a DB read self.response.out.write(team_list[player.<SOME WAY OF GETTING TEAM KEY NAME>]) # Here 'team_list' already has (key_name, name) for all 5 teams I have been struggling with this for a long time. Have read every available documentation. I could just hug the person that can help me here :-) Disclaimer: The above problem description is not a real scenario. It is a simplified arrangement that represents my problem exactly. I have run into it in a rater complex and big GAE appication.

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  • How to use Grails Spring Security Plugin to require logging in before access an action?

    - by Hoàng Long
    Hi all, I know that I can use annotation or Request mapping to restrict access to an ACTION by some specific ROLES. But now I have a different circumstance. My scenario is: every user of my site can create posts, and they can make their own post public, private, or only share to some other users. I implement sharing post by a database table PERMISSION, which specify if a user have the right to view a post or not. The problem arises here is that when a customer access a post through a direct link, how can I determine he/she have the privilege to view it? There's 3 circumstances: The post is public, so it can be viewed by anyone (include not-login user) The post is private, so only the login-owner can view it The post is sharing, it means only the login-user that is shared and the owner can view it. I want to process like this: If the requested post is public: ok. If the requested post is private/sharing: I want to redirect the customer to the login page; after logging in, the user will be re-direct to the page he wants to see. The problem here is that I can redirect the user to login controller/ auth action, but after that I don't know how to redirect it back. The link to every post is different by post_id, so I can't use SpringSecurityUtils.securityConfig.successHandler.defaultTargetUrl Could anyone know a way to do this?

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  • I would like to know how to put a "change image" layer like in facebook on a mouseover event

    - by netadictos
    Hello: I have a photo gallery I would like that every time a user does mouseover the image, there is a button on the top of this image that appears. The user can click on it. But every time that the user mouse out of the photo it must disappear. It works like the "change photo" in Facebook, with the photo of your profile. The problem I am having is that when I try to get over the button that appears (in my code is a link), it disappear because javascript understands that the mouse is just out of the image, even if this button/link is over the image. The image that I use is positioned absolutely over the image. This is my code, where you can see that I create a dom element that I append on the link of the image and then when there is a mouseout, I remove it. $('a.ftelement').mouseover(function() { var fav = $('<a></a>'); fav.attr("class","imgfavorito"); fav.attr("id","fav"+$J(this).attr("id")).html("<img src=\"/im/favorito.gif\"/>"); fav.appendTo(this); }); $('a.ftelement').mouseout(function() { $("a.imgfavorito").remove() }); The result is this graphically (http://www.freeimagehosting.net/uploads/41fbac8994.gif):

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  • How to define trees with more than one type in ML programing language

    - by user550413
    Well, I am asked to do the next thing: To define a binary tree which can contain 2 different types: ('a,'b) abtree and these are the requirements: Any inner vertex (not a leaf) must be of the type 'a or 'b and the leafs have no value. For every path in the tree all 'a values must appear before the 'b value: examples of paths: 'a->'a->'a-'b (legal) 'a->'b->'b (legal) 'a->'a->'a (legal) 'b->'b->'b (legal) 'a->'b->'a (ILLEGAL) and also I need to define another tree which is like the one described above but now I have got also 'c and in the second requirement it says that for every path I 'a values appear before the 'b values and all the 'b values appear before the 'c values. First, I am not sure how to define binary trees to have more than 1 type in them. I mean the simplest binary tree is: datatype 'a tree = leaf | br of 'a * 'a tree * 'a tree; And also how I can define a tree to have these requirements. Any help will be appreciated. Thanks.

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  • How to encrypt/decrypt a file in Java?

    - by Petike
    Hello, I am writing a Java application which can "encrypt" and consequently "decrypt" whatever binary file. I am just a beginner in the "cryptography" area so I would like to write a very simple application for the beginning. For reading the original file, I would probably use the java.io.FileInputStream class to get the "array of bytes" byte originalBytes[] of the file. Then I would probably use some very simple cipher, for example "shift up every byte by 1" and then I would get the "encrypted" bytes byte encryptedBytes[] and let's say that I would also set a "password" for it, for example "123456789". Next, when somebody wants to "decrypt" that file, he has to enter the password ("123456789") first and after that the file could be decrypted (thus "shift down every byte by 1") and consequently saved to the output file via java.io.FileOutputStream I am just wondering how to "store" the password information to the encrypted file so that the decrypting application knows if the entered password and the "real" password equals? Probably it would be silly to add the password (for example the ASCII ordinal numbers of the password letters) to the beginning of the file (before the encrypted data). So my main question is how to store the password information to the encrypted file?

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  • Update Datatable and DatagridView with database Changes by Timer

    - by aleroot
    Scenario : i have a database table that is being updated frequently by some services. I have a c# Winforms Application that load this table in a datagridview by binding a datatable as Datasource, then i whant to add a Timer that every 10 seconds update a the content of a datatable with the last changes in the database table ... I don't need to update a database with the datatable changes, but i need to update datatable with the last changes in the database table, that is the inverse of the usually.... Is there a way to do that ? What is the best way ? i've tried with this code : private void ServiceTimer_Tick(object state) { OdbcConnection oCon = new OdbcConnection(); oCon.ConnectionString = ConnectionStrings; OdbcDataAdapter dp = new OdbcDataAdapter("SELECT * FROM table", oCon); dsProva.Tables.Clear(); dp.Fill(dsProva,"table"); dataGridViewMessaggi.DataSource = dsProva.Tables["table"]; dataGridViewMessaggi.Refresh(); } But every Timer Tick i lost the selection in DatagridView and Current Row .... Is There a better solution ?

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  • Correct way to do timer function in Python

    - by bwawok
    Hi. I have a GUI application that needs to do something simple in the background (update a wx python progress bar, but that doesn't really matter). I see that there is a threading.timer class.. but there seems to be no way to make it repeat. So if I use the timer, I end up having to make a new thread on every single execution... like : import threading import time def DoTheDew(): print "I did it" t = threading.Timer(1, function=DoTheDew) t.daemon = True t.start() if __name__ == '__main__': t = threading.Timer(1, function=DoTheDew) t.daemon = True t.start() time.sleep(10) This seems like I am making a bunch of threads that do 1 silly thing and die.. why not write it as : import threading import time def DoTheDew(): while True: print "I did it" time.sleep(1) if __name__ == '__main__': t = threading.Thread(target=DoTheDew) t.daemon = True t.start() time.sleep(10) Am I missing some way to make a timer keep doing something? Either of these options seems silly... I am looking for a timer more like a java.util.Timer that can schedule the thread to happen every second... If there isn't a way in Python, which of my above methods is better and why?

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  • How do I add code automatically to a derived function in C++

    - by Ian
    I have code that's meant to manage operations on both a networked client and a server, since there is significant overlap between the two. However, there are a few functions here and there that are meant to be exclusively called by the client or server, and accidentally calling a client function on the server (or vice versa) is a significant source of bugs. To reduce these sorts of programming errors, I'm trying to tag functions so that they'll raise a ruckus if they're misused. My current solution is a simple macro at the start of each function that calls an assert if the client or server accesses members they shouldn't. However, this runs into problems when there are multiple derived instances of classes, in that I have to tag the implementation as client or server side in EVERY child class. What I'd like to be able to do is put a tag in the virtual member's signature in the base class, so that I only have to tag it once and not run into errors by forgetting to do it repeatedly. I've considered putting a check in a base class implementation and then referring to it with something like base::functionName, but that runs into the same issue as far as needing to manually add the function call to every implementation. Ideally, I'd be able to have parent versions of the function called automatically like default constructors do. Does anybody know how to achieve something like this in C++? Is there an alternate approach I should be considering? Thanks!

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