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• dojo parser not escaping quotation marks in attributes?

  - by peirix

  Whenever I'm using quotation marks inside an attribute value in dojo, it seems dojo's parser isn't handling it very well... <textarea name="content.locale['en']" dojoType="dijit.form.SimpleTextarea"> </textarea> Turns into: <textarea ]="" en="" name="content.locale["></textarea> With the surrounding <div>s and what not is added by the dijit widget. Any ideas? EDIT Seems this is working as it should with other elements, it's just the SimpleTextarea that's causing a problem..

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• how to stop onChange in javascript

  - by shrimpy

  in one of my selection box, i have a onChange="..." specified... coz i want to change some other form value after any selection changes. however ... in the same page, some wired case i have to manually set the value.. so i have to use some javascript to set the value of the selection combox, but in this case, i don`t want that onChange event to be fired... how can i walk around it??? Forgot to mention that i am actually using dijit.form.comboBox. for normal HTML form comboBox, it won`t cause any issue. Only i use the dijit comboBox, and i try to set the value to some other value, dojo will trigger the onChange.

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• transparently proxying a firewalled web application from a non-standard port to port 80

  - by Terrence Brannon

  I have a web application that serves on port 8088 on $server. However, the only port accessible from remote on $server is port 80. Furthermore, only CGI programs can execute on port 80. I would like to write a CGI program accessible via port 80 that allows one to use the web app running on port 8088. From my view, an ideal solution would be some sort of Java web browser that simply opened up a window and allowed me to use the program running on that port. The CGI program would simply initiate a web browser applet or something. I wrote a Perl CGI program that does it, but I really would like a more transparent solution: my $q = new CGI; print $q->header; use LWP::Simple; use HTML::Tree; my $base = "http://localhost:8088"; my $request = $base; my $qurl = $q->param('url'); if (length($qurl) > 1) { warn "long $qurl"; $request = "$base$qurl"; } else { warn "short $qurl"; } my $content = get($request); my $tree = HTML::TreeBuilder->new_from_content($content); my @a = $tree->look_down('_tag' => 'a'); for my $a (@a) { my $url = $a->attr('href'); next if index($url, '#') > -1 ; $url = "?url=$url"; $a->attr(href => $url); } print $tree->as_HTML;

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• What UI Library(widgets) are you using in your Spring MVC or Spring Web Flow Project [closed]

  - by techsjs2012

  What UI Library(widgets) are you using in your Spring MVC or Spring Web Flow Project I am working on a number of projects with Spring MVC and Spring Web Flow and we started to use Dojo(dijit) widgets for the UI Library. I would like to hear from other projects if anyone knows of anything better or what are you using?? My screens looks like the one below.. the layouts are easy but I need hightlighting, tooltips and more...

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• Treeview - Hierarchical Data Template - Binding does not update on source change?

  - by ClearsTheScreen

  Greetings! I ran into this problem in my project (Silverlight 3 with C#): I have a TreeView which is data bound to, well, a tree. This TreeView has a HierarchicalDataTamplate in a resource dictionary, that defines various controls. Now I want to hide (Visibility.Collapse) some items depending on wether a node has children or not. Other items shall be visible under the same condition. It works like charm when I first bind the source tree to the TreeView, but when I change the source tree, the visibility in the treeview does not change. XAML - page: <controls:TreeView x:Name="SankeyTreeView" ItemContainerStyle="{StaticResource expandedTreeViewItemStyle}" ItemTemplate="{StaticResource SankeyTreeTemplate}"> <controls:TreeViewItem IsExpanded="True"> <controls:TreeViewItem.HeaderTemplate> <DataTemplate> <TextBlock Text="This is just for loading and will be replaced directly after the data becomes available..."/> </DataTemplate> </controls:TreeViewItem.HeaderTemplate> </controls:TreeViewItem> </controls:TreeView> XAML - ResourceDictionary <!-- Each node in the tree is structurally identical, hence only one Hierarchical Data Template that'll use itself on the children. --> <Data:HierarchicalDataTemplate x:Key="SankeyTreeTemplate" ItemsSource="{Binding Children}"> <Grid Height="24"> <TextBlock x:Name="TextBlockName" Text="{Binding Path=Value.name, Mode=TwoWay}" VerticalAlignment="Center" Foreground="Black"/> <TextBox x:Name="TextBoxFlow" Text="{Binding Path=Value.flow, Mode=TwoWay}" Grid.Column="1" Visibility="{Binding Children, Converter={StaticResource BoxConverter}, ConverterParameter=\{box\}}"/> <TextBlock x:Name="TextBlockThroughput" Text="{Binding Path=Value.throughput, Mode=TwoWay}" Grid.Column="1" Visibility="{Binding Children, Converter={StaticResource BoxConverter}, ConverterParameter=\{block\}}"/> <Button x:Name="ButtonAddNode"/> <Button x:Name="ButtonDeleteNode"/> <Button x:Name="ButtonEditNode"/> </Grid> </Data:HierarchicalDataTemplate> Now, as you can see, the TextBoxFlow and the TextBlockThroughput share the same space. What I aim at: The "Throughput" value of a node is how much of something 'flows' through this node from its children. It can't be changed directly, so I want to display a text block. Only leaf nodes have a TextBox to let someone enter the 'flow' that is generated in this leaf node. (I.E.: Node.Throughput = Node.Flow + Sum(Children.Throughput), where Node.Flow = 0 for each non-leaf.) What the BoxConverter (silly name -.-) does: public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture) { if ((value as NodeList<TreeItem>).Count > 1) // Node has Children? { if ((parameter as String) == "{box}") { return Visibility.Collapsed; } else ((parameter as String) == "{block}") { return Visibility.Visible; } } else { /* * As above, just with Collapsed and Visible switched */ } } The structure of the tree that is bound to the TreeView is essentially stolen from Dan Vanderboom (a bit too much to dump the whole code here), except that I here of course use an ObservableCollection for the children and the value items implement INotifyPropertyChanged. I would be very grateful if someone could explain to me, why inserting items into the underlying tree does not update the visibility for box and block. Thank you in advance!

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• How can I resolve gstreamer dependencies in Ubuntu

  - by michael

  Hi, Can you please tell me how can I resolve these dependencies on ubuntu: checking for GSTREAMER... configure: error: Package requirements (gstreamer-0.10 >= 0.10 gstreamer-app-0.10 gstreamer-base-0.10 gstreamer-pbutils-0.10 gstreamer-plugins-base-0.10 >= 0.10.25 gstreamer-video-0.10) were not met: No package 'gstreamer-app-0.10' found No package 'gstreamer-pbutils-0.10' found No package 'gstreamer-plugins-base-0.10' found No package 'gstreamer-video-0.10' found I have tried: $ sudo apt-get install *gstreamer-video* Reading package lists... Done Building dependency tree Reading state information... Done E: Regex compilation error - Invalid preceding regular expression $ sudo apt-get install *gstreamer-app* Reading package lists... Done Building dependency tree Reading state information... Done E: Regex compilation error - Invalid preceding regular expression $ sudo apt-get install *gstreamer-base* Reading package lists... Done Building dependency tree Reading state information... Done E: Regex compilation error - Invalid preceding regular expression

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• Keyboard Navigation of File Open Dialog in Windows 7

  - by dkusleika

  In Windows XP standard File - Open dialog, the top has a "Look In" box. I can press Alt+I to drop down a tree of the disks folders and easily navigate to other folders or network shares. In Windows 7, I can't seem to navigate the File - Open dialog as easily. The best I've been able to muster is to tab 5 times (in Excel 2007, but I assume it's a windows standard), then use arrow keys or use Alt+arrow keys like a browser to get around. It's simply not as good because I can't see the whole tree at once. Is there a way to see the whole folder tree? If not, do you have any other tips for keyboard navigation of the file open dialog in Windows 7?

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• How Can I Close the Leftmost Window in Vim?

  - by msutherl

  I'm trying to write a command that will close a tree-browser (vim-tree) window and resize the other windows. ,to opens the window and adjusts the window size so that all open windows retain a normal size (using :set columns+=30CTRL-W =). ,tc should close the tree window (full-length, far left) and resize the main window (:set columns-=30). How can I write a command that closes the leftmost window so that I can type ,tc to close the window and resize in one shot? I can navigate to it with CTRL-W h, but it is inelegant and potentially annoying (audible bell!) to use 10CTRL-W h in the command. :topleft c unfortunately doesn't work. Can you think of an elegant way to do this?

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• Check if folders exist in Git repository... testing if a sub-string exists in bash with NULL as a separator

  - by Craig Francis

  I have a common git "post-receive" script for several projects, and it needs to perform different actions if an /app/ or /public/ folder exists in the root. Using: FOLDERS=`git ls-tree -d --name-only -z master`; I can see the directory listing, and I would like to use the RegExp support in bash to run something like: if [[ "$FOLDERS" =~ app ]]; then ... fi But that won't work if there was something like an "app lication" folder... I specified the "-z" option in the git "ls-tree" command so I could use the \0 (null) character as a separator, but not sure how to test for that in the bash RegExp. Likewise I know there is support for specifying a particular path in the ls-tree command, and could then pipe that to "wc -l", but I'd have thought it was quicker to get a full directory listing of the root (not recursive) then test for the 2 (or more) folders with the returned output. Possibly related to: http://stackoverflow.com/questions/7938094/git-how-to-check-which-files-exist-and-their-content-in-a-shared-bare-repos

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• One Exception to Aggregate Them All

  - by João Angelo

  .NET 4.0 introduced a new type of exception, the AggregateException which as the name implies allows to aggregate several exceptions inside a single throw-able exception instance. It is extensively used in the Task Parallel Library (TPL) and besides representing a simple collection of exceptions can also be used to represent a set of exceptions in a tree-like structure. Besides its InnerExceptions property which is a read-only collection of exceptions, the most relevant members of this new type are the methods Flatten and Handle. The former allows to flatten a tree hierarchy removing the need to recur while working with an aggregate exception. For example, if we would flatten the exception tree illustrated in the previous figure the result would be: The other method, Handle, accepts a predicate that is invoked for each aggregated exception and returns a boolean indicating if each exception is handled or not. If at least one exception goes unhandled then Handle throws a new AggregateException containing only the unhandled exceptions. The following code snippet illustrates this behavior and also another scenario where an aggregate exception proves useful – single threaded batch processing. static void Main() { try { ConvertAllToInt32("10", "x1x", "0", "II"); } catch (AggregateException errors) { // Contained exceptions are all FormatException // so Handle does not thrown any exception errors.Handle(e => e is FormatException); } try { ConvertAllToInt32("1", "1x", null, "-2", "#4"); } catch (AggregateException errors) { // Handle throws a new AggregateException containing // the exceptions for which the predicate failed. // In this case it will contain a single ArgumentNullException errors.Handle(e => e is FormatException); } } private static int[] ConvertAllToInt32(params string[] values) { var errors = new List<Exception>(); var integers = new List<int>(); foreach (var item in values) { try { integers.Add(Int32.Parse(item)); } catch (Exception e) { errors.Add(e); } } if (errors.Count > 0) throw new AggregateException(errors); return integers.ToArray(); }

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• Allen for Umbraco with location EXIF meta data

  - by Vizioz Limited

  The latest version of Allen for Umbraco has now hit the Apple App store, we have managed to add some nice improvements to this version that include:Storing location and direction information when photos are taken within the AppEmbedding EXIF data into the images when they are uploadBackground UploadingPull to refresh the media tree Location and DirectionBy default when the camera is used within an application the location and direction that the camera is pointing is not stored within the image meta data. We have now added full support so that this data is now added. We have added a setting which allows you to prevent this data from being uploaded to your website if you do not want the location data to be sent you can turn it off within Allen, Note: Please don't forget that location services do need to be turned on to allow the app to access the images in the phone's asset library.We have had quite a few ideas from users already for using this location data, including logging free parking in Denmark to geo-tagging holiday photos and linking the photos to Google street view. Embedding EXIF dataWe now embed all the meta data available on the iPhone into the image when it is uploaded to your server, this allows you to pull the data out and use it within your site. Have a look at Cultiv's Photo Meta Data package for great example code that allows you to automatically pull this data out and populate properties on your Umbraco media item.We slightly modified the source code of this package to allow the package to always extract the image data, as the default package requires a property to allow the data to be extracted, it's an easy change, if you get stuck add a comment to this post. Background UploadingIf you try to upload multiple images and need to start doing something else on your phone, you can now click the home button and the application will continue to upload your images in the background. As soon as it has finished you will receive a standard Apple notification. Pull to RefreshOur final enhancement has been to add "Pull to refresh" to the media trees, just pull the tree downwards with your finger and it will refresh, this is useful if you are adding items to your media tree while testing your site with Allen for Umbraco. Future enhancements.. your ideas?If you have any ideas for future enhancement feel free to add a comment below!

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• Why are some checkboxes in Software Updater disabled?

  - by Drew Noakes

  In Ubuntu 13.04, the Software Updater shows some apps as having updates, but they're non-selectable: It's not clear why they're greyed out. On the command line: $ sudo apt-get upgrade Reading package lists... Done Building dependency tree Reading state information... Done The following packages have been kept back: gnuplot-nox gnuplot-x11 nvidia-current 0 upgraded, 0 newly installed, 0 to remove and 3 not upgraded. Note too that running apt-get dist-upgrade does not cause them to be installed either, as it sometimes does with packages that are kept back. Here's the output: $ sudo apt-get dist-upgrade Reading package lists... Done Building dependency tree Reading state information... Done Calculating upgrade... Done The following packages have been kept back: gnuplot-nox gnuplot-x11 nvidia-current 0 upgraded, 0 newly installed, 0 to remove and 3 not upgraded. I took @quidage's suggestion, which gives the following. However subsequent upgrades show the same message: $ sudo apt-get install -f Reading package lists... Done Building dependency tree Reading state information... Done 0 upgraded, 0 newly installed, 0 to remove and 3 not upgraded.

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• How to fix a dpkg broken by the Brother MFC-7340 deb driver

  - by Roman A. Taycher

  I'm getting an apt-get error that says E: The package brmfc7340lpr needs to be reinstalled, but I can't find an archive for it. (the brmfc7340lpr is a printer driver) its a local deb file, doing an dpkg or apt-get purge doesn't work, neither does apt-get install -f How do I reinstall a package from a local deb file? P.S. box-name% sudo apt-get upgrade [sudo] password for username: Reading package lists... Done Building dependency tree Reading state information... Done E: The package brmfc7340lpr needs to be reinstalled, but I can't find an archive for it. box-name% sudo apt-get purge brmfc7340lpr Reading package lists... Done Building dependency tree Reading state information... Done E: The package brmfc7340lpr needs to be reinstalled, but I can't find an archive for it. box-name% sudo dpkg --purge brmfc7340lpr dpkg: error processing brmfc7340lpr (--purge): Package is in a very bad inconsistent state - you should reinstall it before attempting a removal. Errors were encountered while processing: brmfc7340lpr box-name% sudo dpkg --install brmfc7340lpr-2.0.2-1.i386.deb Selecting previously deselected package brmfc7340lpr. (Reading database ... 725204 files and directories currently installed.) Preparing to replace brmfc7340lpr 2.0.2-1 (using .../brmfc7340lpr-2.0.2-1.i386.deb) ... Unpacking replacement brmfc7340lpr ... start: Unknown job: lpd dpkg: warning: subprocess old post-removal script returned error exit status 1 dpkg - trying script from the new package instead ... start: Unknown job: lpd dpkg: error processing brmfc7340lpr-2.0.2-1.i386.deb (--install): subprocess new post-removal script returned error exit status 1 start: Unknown job: lpd dpkg: error while cleaning up: subprocess new post-removal script returned error exit status 1 Errors were encountered while processing: brmfc7340lpr-2.0.2-1.i386.deb box-name% sudo apt-get install -f Reading package lists... Done Building dependency tree Reading state information... Done E: The package brmfc7340lpr needs to be reinstalled, but I can't find an archive for it. box-name%

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• Finding a way to simplify complex queries on legacy application

  - by glenatron

  I am working with an existing application built on Rails 3.1/MySql with much of the work taking place in a JavaScript interface, although the actual platforms are not tremendously relevant here, except in that they give context. The application is powerful, handles a reasonable amount of data and works well. As the number of customers using it and the complexity of the projects they create increases, however, we are starting to run into a few performance problems. As far as I can tell, the source of these problems is that the data represents a tree and it is very hard for ActiveRecord to deterministically know what data it should be retrieving. My model has many relationships like this: Project has_many Nodes has_many GlobalConditions Node has_one Parent has_many Nodes has_many WeightingFactors through NodeFactors has_many Tags through NodeTags GlobalCondition has_many Nodes ( referenced by Id, rather than replicating tree ) WeightingFactor has_many Nodes through NodeFactors Tag has_many Nodes through NodeTags The whole system has something in the region of thirty types which optionally hang off one or many nodes in the tree. My question is: What can I do to retrieve and construct this data faster? Having worked a lot with .Net, if I was in a similar situation there, I would look at building up a Stored Procedure to pull everything out of the database in one go but I would prefer to keep my logic in the application and from what I can tell it would be hard to take the queried data and build ActiveRecord objects from it without losing their integrity, which would cause more problems than it solves. It has also occurred to me that I could bunch the data up and send some of it across asynchronously, which would not improve performance but would improve the user perception of performance. However if sections of the data appeared after page load that could also be quite confusing. I am wondering whether it would be a useful strategy to make everything aware of it's parent project, so that one could pull all the records for that project and then build up the relationships later, but given the ubiquity of complex trees in day to day programming life I wouldn't be surprised if there were some better design patterns or standard approaches to this type of situation that I am not well versed in.

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• apt-get failed install of libg15, all package management is failing

  - by Stifle

  I was trying to get my Logitech G510 keyboard's back-lights working so I went into the Synaptic Package Manager and marked LibG15, G15daemon, and all the other associated packages. Synaptic reported a failed install. Now all Package management is failing due to libg15 being "halfway installed." Some commands I have tried to fix the problem follow. . . root@bt:~# apt-get upgrade Reading package lists... Done Building dependency tree Reading state information... Done E: The package libg15 needs to be reinstalled, but I can't find an archive for it. root@bt:~# sudo apt-get autoremove Reading package lists... Done Building dependency tree Reading state information... Done E: The package libg15 needs to be reinstalled, but I can't find an archive for it. root@bt:~# sudo apt-get -f purge libg15 Reading package lists... Done Building dependency tree Reading state information... Done E: The package libg15 needs to be reinstalled, but I can't find an archive for it. root@bt:~# sudo dpkg --configure -a dpkg: dependency problems prevent configuration of g15macro: g15macro depends on g15daemon; however: Package g15daemon is not configured yet. dpkg: error processing g15macro (--configure): dependency problems - leaving unconfigured dpkg: dependency problems prevent configuration of g15stats: g15stats depends on g15daemon; however: Package g15daemon is not configured yet. dpkg: error processing g15stats (--configure): dependency problems - leaving unconfigured Errors were encountered while processing: g15macro g15stats I'm not too computer savvy. Any help would be much appreciated!!! Note: I'm using Ubuntu 10.04 under Backtrack 5 R3.

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• Using Behavior Trees and Events together

  - by weichsem

  I am beginning to work with behavior trees and am unsure how events should be handled within the tree. Lets say we have a space game where the player is dogfighting with a handful of other ships, some friendly some not. The player destroys a ship and the rest of the hostile ships should then start to retreat. How was should the shipWasDestroyed event effect the other ship's behavior trees so that they start running the retreat behavior? One way I could think of doing this is have all the conditions I care about be high level nodes that effectively state change the ship. This would mean I'd have to check all of these state change conditions on every frame the behavior tree was run, even if they are very rare occurrences. I'd prefer not doing this for performance and complexity reasons. From looking at the Halo papers on behavior trees it seems that they handled this by dynamically placing nodes into the tree when the event occurred. It seems like calculating where the new node should go could be problematic depending on the current state of the running behavior. How is this normally handled?

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• Installing latest version of R-base

  - by Student

  I have been unsuccessfully trying to install the latest version (2.15.2) of r-base. Apparently, R package "Rcpp" would not install for R version 2.14.1 - the version that installs for me. I am not sure what/how/where to change my installation attempts which appear below. Please note that I am using ubuntu-12.04.1-server-i386. (1) ------------ The current installed version is R version 2.14.1 (2011-12-22) sudo apt-get install r-base Reading package lists... Done Building dependency tree Reading state information... Done r-base is already the newest version. (2) ------------ Including version information doesn't help: sudo apt-get install r-base=2.15.1-5ubuntu1 Reading package lists... Done Building dependency tree Reading state information... Done E: Version '2.15.1-5ubuntu1' for 'r-base' was not found (3) ------------- Changes based on CRAN Ubuntu instructions http://cran.r-project.org/bin/linux/ubuntu/README 3.1: Added to /etc/apt/sources.list deb http://lib.stat.cmu.edu/R/CRAN/bin/linux/ubuntu quantal/ 3.2: sudo apt-get update 3.3: sudo apt-get install r-base Reading package lists... Done Building dependency tree Reading state information... Done Some packages could not be installed. This may mean that you have requested an impossible situation or if you are using the unstable distribution that some required packages have not yet been created or been moved out of Incoming. The following information may help to resolve the situation: The following packages have unmet dependencies: r-base : Depends: r-base-core (= 2.15.2-1quantal2) but it is not going to be installed Depends: r-recommended (= 2.15.2-1quantal2) but it is not going to be installed Recommends: r-base-html but it is not going to be installed E: Unable to correct problems, you have held broken packages.

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• Trouble installing gnome-shell-extensions-user-theme, dependency/PPA conflict?

  - by Drex

  I installed gnome tweak tool, and am trying to set up custom themes and whatnot. So, trying to install gnome-shell-extensions-user-theme. me@computer:~$ sudo apt-get install gnome-shell-extensions-user-theme [sudo] password for me: Reading package lists... Done Building dependency tree Reading state information... Done Some packages could not be installed. This may mean that you have requested an impossible situation or if you are using the unstable distribution that some required packages have not yet been created or been moved out of Incoming. The following information may help to resolve the situation: The following packages have unmet dependencies: gnome-shell-extensions-user-theme : Depends: gnome-shell-extensions-common but it is not going to be installed E: Unable to correct problems, you have held broken packages. Not going to be installed? Okay, let's see about that... me@computer:~$ sudo apt-get install gnome-shell-extensions-common Reading package lists... Done Building dependency tree Reading state information... Done gnome-shell-extensions-common is already the newest version. 0 upgraded, 0 newly installed, 0 to remove and 0 not upgraded. Wait, what? Broken packages? Ruh Roh! Seems to me it might be a PPA contradiction problem or something, but I'm tired of trashing my installs. Kinda lost here. Any ideas? Output of sudo apt-get install -f drex@U110:~$ sudo apt-get install -f Reading package lists... Done Building dependency tree Reading state information... Done 0 upgraded, 0 newly installed, 0 to remove and 0 not upgraded.

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• How should I compress a file with multiple bytes that are the same with Huffman coding?

  - by Omega

  On my great quest for compressing/decompressing files with a Java implementation of Huffman coding (http://en.wikipedia.org/wiki/Huffman_coding) for a school assignment, I am now at the point of building a list of prefix codes. Such codes are used when decompressing a file. Basically, the code is made of zeroes and ones, that are used to follow a path in a Huffman tree (left or right) for, ultimately, finding a byte. In this Wikipedia image, to reach the character m the prefix code would be 0111 The idea is that when you compress the file, you will basically convert all the bytes of the file into prefix codes instead (they tend to be smaller than 8 bits, so there's some gain). So every time the character m appears in a file (which in binary is actually 1101101), it will be replaced by 0111 (if we used the tree above). Therefore, 1101101110110111011011101101 becomes 0111011101110111 in the compressed file. I'm okay with that. But what if the following happens: In the file to be compressed there exists only one unique byte, say 1101101. There are 1000 of such byte. Technically, the prefix code of such byte would be... none, because there is no path to follow, right? I mean, there is only one unique byte anyway, so the tree has just one node. Therefore, if the prefix code is none, I would not be able to write the prefix code in the compressed file, because, well, there is nothing to write. Which brings this problem: how would I compress/decompress such file if it is impossible to write a prefix code when compressing? (using Huffman coding, due to the school assignment's rules) This tutorial seems to explain a bit better about prefix codes: http://www.cprogramming.com/tutorial/computersciencetheory/huffman.html but doesn't seem to address this issue either.

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• Seek first to understand, then to be understood

  - by BuckWoody

  One of the most important (and most difficult) lessons for a technical professional to learn is to not jump to the solution. Perhaps you’ve done this, or had it happen to you. As the person you’re “listening” to is speaking, your mind is performing a B-Tree lookup on possible solutions, and when the final node of the B-Tree in your mind is reached, you blurt out the “only” solution there is to the problem, whether they are done or not. There are two issues here – both of them fatal if you don’t factor them in. First, your B-Tree may not be complete, or correct. That of course leads to an incorrect response, which blows your credibility. People will not trust you if this happens often. The second danger is that the person may modify their entire problem with a single word or phrase. I once had a client explain a detailed problem to me – and I just KNEW the answer. Then they said at the end “well, that’s what it used to do, anyway. Now it doesn’t do that anymore.” Which of course negated my entire solution – happily I had kept my mouth shut until they finished. So practice listening, rather than waiting for your turn to speak. Let the person finish, let them get the concept out, give them your full attention. They’ll appreciate the courtesy, you’ll look more intelligent, and you both may find the right answer to the problem. Share this post: email it! | bookmark it! | digg it! | reddit! | kick it! | live it!

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• TVirtualStringTree - resetting non-visual nodes and memory consumption

  - by Remy Lebeau - TeamB

  I have an app that loads records from a binary log file and displays them in a virtual TListView. There are potentially millions of records in a file, and the display can be filtered by the user, so I do not load all of the records in memory at one time, and the ListView item indexes are not a 1-to-1 relation with the file record offsets (List item 1 may be file record 100, for instance). I use the ListView's OnDataHint event to load records for just the items the ListView is actually interested in. As the user scrolls around, the range specified by OnDataHint changes, allowing me to free records that are not in the new range, and allocate new records as needed. This works fine, speed is tolerable, and the memory footprint is very low. I am currently evaluating TVirtualStringTree as a replacement for the TListView, mainly because I want to add the ability to expand/collapse records that span multiple lines (I can fudge it with the TListView by incrementing/decrementing the item count dynamically, but this is not as straight forward as using a real tree). For the most part, I have been able to port the TListView logic and have everything work as I need. I notice that TVirtualStringTree's virtual paradigm is vastly different, though. It does not have the same kind of OnDataHint functionality that TListView does (I can use the OnScroll event to fake it, which allows my memory buffer logic to continue working), and I can use the OnInitializeNode event to associate nodes with records that are allocated. However, once a tree node is initialized, it sees that it remains initialized for the lifetime of the tree. That is not good for me. As the user scrolls around and I remove records from memory, I need to reset those non-visual nodes without removing them from the tree completely, or losing their expand/collapse states. When the user scrolls them back into view, I can re-allocate the records and re-initialize the nodes. Basically, I want to make TVirtualStringTree act as much like TListView as possible, as far as its virtualization is concerned. I have seen that TVirtualStringTree has a ResetNode() method, but I encounter various errors whenever I try to use it. I must be using it wrong. I also thought of just storing a data pointer inside each node to my record buffers, and I allocate and free memory, update those pointers accordingly. The end effect does not work so well, either. Worse, my largest test log file has ~5 million records in it. If I initialize the TVirtualStringTree with that many nodes at one time (when the log display is unfiltered), the tree's internal overhead for its nodes takes up a whopping 260MB of memory (without any records being allocated yet). Whereas with the TListView, loading the same log file and all the memory logic behind it, I can get away with using just a few MBs. Any ideas?

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• TVirtualStringTree - resetting non-visual nodes and memory comsumption

  - by Remy Lebeau - TeamB

  I have an app that loads records from a binary log file and displays them in a virtual TListView. There are potentially millions of records in a file, and the display can be filtered by the user, so I do not load all of the records in memory at one time, and the ListView item indexes are not a 1-to-1 relation with the file record offsets (List item 1 may be file record 100, for instance). I use the ListView's OnDataHint event to load records for just the items the ListView is actually interested in. As the user scrolls around, the range specified by OnDataHint changes, allowing me to free records that are not in the new range, and allocate new records as needed. This works fine, speed is tolerable, and the memory footprint is very low. I am currently evaluating TVirtualStringTree as a replacement for the TListView, mainly because I want to add the ability to expand/collapse records that span multiple lines (I can fudge it with the TListView by incrementing/decrementing the item count dynamically, but this is not as straight forward as using a real tree). For the most part, I have been able to port the TListView logic and have everything work as I need. I notice that TVirtualStringTree's virtual paridigm is vastly different, though. It does not have the same kind of OnDataHint functionality that TListView does (I can use the OnScroll event to fake it, which allows my memory buffer logic to continue working), and I can use the OnInitializeNode event to associate nodes with records that are allocated. However, once a tree node is initialized, it sees that it remains initialized for the lifetime of the tree. That is not good for me. As the user scrolls around and I remove records from memory, I need to reset those non-visual nodes without removing them from the tree completely, or losing their expand/collapse states. When the user scrolls them back into view, I can re-allocate the records and re-initialize the nodes. Basically, I want to make TVirtualStringTree act as much like TListView as possible, as far as its virtualization is concerned. I have seen that TVirtualStringTree has a ResetNode() method, but I encounter various errors whenever I try to use it. I must be using it wrong. I also thought of just storing a data pointer inside each node to my record buffers, and I allocate and free memory, update those pointers accordingly. The end effect does not work so well, either. Worse, my largest test log file has ~5 million records in it. If I initialize the TVirtualStringTree with that many nodes at one time (when the log display is unfiltered), the tree's internal overhead for its nodes takes up a whopping 260MB of memory (without any records being allocated yet). Whereas with the TListView, loading the same log file and all the memory logic behind it, I can get away with using just a few MBs. Any ideas?

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• What's the best way to do base36 arithmetic in perl?

  - by DVK

  What's the best way to do base36 arithmetic in Perl? To be more specific, I need to be able to do the following: Operate on positive N-digit numbers in base 36 (e.g. digits are 0-9 A-Z) N is finite, say 9 Provide basic arithmetic, at the very least the following 3: Addition (A+B) Subtraction (A-B) Whole division, e.g. floor(A/B). Strictly speaking, I don't really need a base10 conversion ability - the numbers will 100% of time be in base36. So I'm quite OK if the solution does NOT implement conversion from base36 back to base10 and vice versa. I don't much care whether the solution is brute-force "convert to base 10 and back" or converting to binary, or some more elegant approach "natively" performing baseN operations (as stated above, to/from base10 conversion is not a requirement). My only 3 considerations are: It fits the minimum specifications above It's "standard". Currently we're using and old homegrown module based on base10 conversion done by hand that is buggy and sucks. I'd much rather replace that with some commonly used CPAN solution instead of re-writing my own bicycle from scratch, but I'm perfectly capable of building it if no better standard possibility exists. It must be fast-ish (though not lightning fast). Something that takes 1 second to sum up 2 9-digit base36 numbers is worse than anything I can roll on my own :) P.S. Just to provide some context in case people decide to solve my XY problem for me in addition to answering the technical question above :) We have a fairly large tree (stored in DB as a bunch of edges), and we need to superimpose order on a subset of that tree. The tree dimentions are big both depth- and breadth- wise. The tree is VERY actively updated (inserts and deletes and branch moves). This is currently done by having a second table with 3 columns: parent_vertex, child_vertex, local_order, where local_order is an 9-character string built of A-Z0-9 (e.g. base 36 number). Additional considerations: It is required that the local order is unique per child (and obviously unique per parent), Any complete re-ordering of a parent is somewhat expensive, and thus the implementation is to try and assign - for a parent with X children - the orders which are somewhat evenly distributed between 0 and 36**10-1, so that almost no tree inserts result in a full re-ordering.

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• How to generate and encode (for use in GA), random, strict, binary rooted trees with N leaves?

  - by Peter Simon

  First, I am an engineer, not a computer scientist, so I apologize in advance for any misuse of nomenclature and general ignorance of CS background. Here is the motivational background for my question: I am contemplating writing a genetic algorithm optimizer to aid in designing a power divider network (also called a beam forming network, or BFN for short). The BFN is intended to distribute power to each of N radiating elements in an array of antennas. The fraction of the total input power to be delivered to each radiating element has been specified. Topologically speaking, a BFN is a strictly binary, rooted tree. Each of the (N-1) interior nodes of the tree represents the input port of an unequal, binary power splitter. The N leaves of the tree are the power divider outputs. Given a particular power divider topology, one is still free to map the power divider outputs to the array inputs in an arbitrary order. There are N! such permutations of the outputs. There are several considerations in choosing the desired ordering: 1) The power ratio for each binary coupler should be within a specified range of values. 2) The ordering should be chosen to simplify the mechanical routing of the transmission lines connecting the power divider. The number of ouputs N of the BFN may range from, say, 6 to 22. I have already written a genetic algorithm optimizer that, given a particular BFN topology and desired array input power distribution, will search through the N! permutations of the BFN outputs to generate a design with compliant power ratios and good mechanical routing. I would now like to generalize my program to automatically generate and search through the space of possible BFN topologies. As I understand it, for N outputs (leaves of the binary tree), there are $C_{N-1}$ different topologies that can be constructed, where $C_N$ is the Catalan number. I would like to know how to encode an arbitrary tree having N leaves in a way that is consistent with a chromosomal description for use in a genetic algorithm. Also associated with this is the need to generate random instances for filling the initial population, and to implement crossover and mutations operators for this type of chromosome. Any suggestions will be welcome. Please minimize the amount of CS lingo in your reply, since I am not likely to be acquainted with it. Thanks in advance, Peter

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• Idiomatic use of auto_ptr to transfer ownership to a container

  - by heycam

  I'm refreshing my C++ knowledge after not having used it in anger for a number of years. In writing some code to implement some data structure for practice, I wanted to make sure that my code was exception safe. So I've tried to use std::auto_ptrs in what I think is an appropriate way. Simplifying somewhat, this is what I have: class Tree { public: ~Tree() { /* delete all Node*s in the tree */ } void insert(const string& to_insert); ... private: struct Node { ... vector<Node*> m_children; }; Node* m_root; }; template<T> void push_back(vector<T*>& v, auto_ptr<T> x) { v.push_back(x.get()); x.release(); } void Tree::insert(const string& to_insert) { Node* n = ...; // find where to insert the new node ... push_back(n->m_children, auto_ptr<Node>(new Node(to_insert)); ... } So I'm wrapping the function that would put the pointer into the container, vector::push_back, and relying on the by-value auto_ptr argument to ensure that the Node* is deleted if the vector resize fails. Is this an idiomatic use of auto_ptr to save a bit of boilerplate in my Tree::insert? Any improvements you can suggest? Otherwise I'd have to have something like: Node* n = ...; // find where to insert the new node auto_ptr<Node> new_node(new Node(to_insert)); n->m_children.push_back(new_node.get()); new_node.release(); which kind of clutters up what would have been a single line of code if I wasn't worrying about exception safety and a memory leak. (Actually I was wondering if I could post my whole code sample (about 300 lines) and ask people to critique it for idiomatic C++ usage in general, but I'm not sure whether that kind of question is appropriate on stackoverflow.)

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