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  • Navigation for ASP.NET Web Forms project published on codeplex

    Navigation for ASP.NET Web Forms manages movement and data passing between aspx Pages in a unit testable manner. There is no Client-side logic, so it works in all browsers, and no Server-side cache, so it works with the browser back button.Features include loosely coupled Pages, typed data passing, empty code-behinds, context-sensitive bread crumb trail, ASP.NET Data binding integration, automatic ASP.NET Ajax history navigation and many more.The source code, binaries and comprehensive documentation...Did you know that DotNetSlackers also publishes .net articles written by top known .net Authors? We already have over 80 articles in several categories including Silverlight. Take a look: here.

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  • Adding image to navigation bar

    - by 4thSpace
    I'd like an image to take up all of a navigation bar. This is the navigation that comes with a navigation based app. It appears on the RootViewController with the accompanying UITableView. I've seen some examples of how this might work. Set navigation bar title: UIImage *image = [UIImage imageNamed:@"TableviewCellLightBlue.png"]; UIImageView *imageView = [[UIImageView alloc] initWithImage:image]; [self.navigationController.navigationBar.topItem setTitleView:imageView]; The problem there is it only covers the title rather than the entire navigation bar. There is also this thread: http://discussions.apple.com/message.jspa?messageID=9254241#9254241. Towards the end, the solution looks to use a tab bar, which I'm not using. It is that complicated to set a navigation bar background? Is there some other simpler technique? I'd like to have a background for the navigation and still be able to use title text.

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  • What is the best way to handle navigation with PRISM?

    - by stiank81
    Using Prism - what is the best way to handle navigation in a WPF application? And how do you apply this? Are there any best practices? In my application I'm currently using Event Aggregation. Any menu item or other item that should result in navigation in the program will publish an event, and the module responsible for opening the view represented by the published event will do so. This works just fine, but I have a feeling this is not the best way to handle navigation with Prism. Is it?

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  • Return the difference between the lowest and highest key

    - by stan
    This is a past exam paper i am attempting and have no way to check if the out put is correct as i am not capable of building one of these things the question is in the title class Tree{ Tree left; Tree right; int key; public static int span(Tree tree) { if ( tree == null ){ return null; } if( tree.left != null) int min = span(tree.left); } if( tree.right != null){ int max = span(tree.right); } return max - min; } } Could anyone suggest what i need to change to get 5/5 marks :D - the only thing we have to do is write the span method, the header was given for us Thanks

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  • Visual Tree Enumeration

    - by codingbloke
    I feel compelled to post this blog because I find I’m repeatedly posting this same code in silverlight and windows-phone-7 answers in Stackoverflow. One common task that we feel we need to do is burrow into the visual tree in a Silverlight or Windows Phone 7 application (actually more recently I found myself doing this in WPF as well).  This allows access to details that aren’t exposed directly by some controls.  A good example of this sort of requirement is found in the “Restoring exact scroll position of a listbox in Windows Phone 7”  question on stackoverflow.  This required that the scroll position of the scroll viewer internal to a listbox be accessed. A caveat One caveat here is that we should seriously challenge the need for this burrowing since it may indicate that there is a design problem.  Burrowing into the visual tree or indeed burrowing out to containing ancestors could represent significant coupling between module boundaries and that generally isn’t a good idea. Why isn’t this idea just not cast aside as a no-no?  Well the whole concept of a “Templated Control”, which are in extensive use in these applications, opens the coupling between the content of the visual tree and the internal code of a control.   For example, I can completely change the appearance and positioning of elements that make up a ComboBox.  The ComboBox control relies on specific template parts having set names of a specified type being present in my template.  Rightly or wrongly this does kind of give license to writing code that has similar coupling. Hasn’t this been done already? Yes it has.  There are number of blogs already out there with similar solutions.  In fact if you are using Silverlight toolkit the VisualTreeExtensions class already provides this feature.  However I prefer my specific code because of the simplicity principle I hold to.  Only write the minimum code necessary to give all the features needed.  In this case I add just two extension methods Ancestors and Descendents, note I don’t bother with “Get” or “Visual” prefixes.  Also I haven’t added Parent or Children methods nor additional “AndSelf” methods because all but Children is achievable with the addition of some other Linq methods.  I decided to give Descendents an additional overload for depth hence a depth of 1 is equivalent to Children but this overload is a little more flexible than simply Children. So here is the code:- VisualTreeEnumeration public static class VisualTreeEnumeration {     public static IEnumerable<DependencyObject> Descendents(this DependencyObject root, int depth)     {         int count = VisualTreeHelper.GetChildrenCount(root);         for (int i = 0; i < count; i++)         {             var child = VisualTreeHelper.GetChild(root, i);             yield return child;             if (depth > 0)             {                 foreach (var descendent in Descendents(child, --depth))                     yield return descendent;             }         }     }     public static IEnumerable<DependencyObject> Descendents(this DependencyObject root)     {         return Descendents(root, Int32.MaxValue);     }     public static IEnumerable<DependencyObject> Ancestors(this DependencyObject root)     {         DependencyObject current = VisualTreeHelper.GetParent(root);         while (current != null)         {             yield return current;             current = VisualTreeHelper.GetParent(current);         }     } }   Usage examples The following are some examples of how to combine the above extension methods with Linq to generate the other axis scenarios that tree traversal code might require. Missing Axis Scenarios var parent = control.Ancestors().Take(1).FirstOrDefault(); var children = control.Descendents(1); var previousSiblings = control.Ancestors().Take(1)     .SelectMany(p => p.Descendents(1).TakeWhile(c => c != control)); var followingSiblings = control.Ancestors().Take(1)     .SelectMany(p => p.Descendents(1).SkipWhile(c => c != control).Skip(1)); var ancestorsAndSelf = Enumerable.Repeat((DependencyObject)control, 1)     .Concat(control.Ancestors()); var descendentsAndSelf = Enumerable.Repeat((DependencyObject)control, 1)     .Concat(control.Descendents()); You might ask why I don’t just include these in the VisualTreeEnumerator.  I don’t on the principle of only including code that is actually needed.  If you find that one or more of the above  is needed in your code then go ahead and create additional methods.  One of the downsides to Extension methods is that they can make finding the method you actually want in intellisense harder. Here are some real world usage scenarios for these methods:- Real World Scenarios //Gets the internal scrollviewer of a ListBox ScrollViewer sv = someListBox.Descendents().OfType<ScrollViewer>().FirstOrDefault(); // Get all text boxes in current UserControl:- var textBoxes = this.Descendents().OfType<TextBox>(); // All UIElement direct children of the layout root grid:- var topLevelElements = LayoutRoot.Descendents(0).OfType<UIElement>(); // Find the containing `ListBoxItem` for a UIElement:- var container = elem.Ancestors().OfType<ListBoxItem>().FirstOrDefault(); // Seek a button with the name "PinkElephants" even if outside of the current Namescope:- var pinkElephantsButton = this.Descendents()     .OfType<Button>()     .FirstOrDefault(b => b.Name == "PinkElephants"); //Clear all checkboxes with the name "Selector" in a Treeview foreach (CheckBox checkBox in elem.Descendents()     .OfType<CheckBox>().Where(c => c.Name == "Selector")) {     checkBox.IsChecked = false; }   The last couple of examples above demonstrate a common requirement of finding controls that have a specific name.  FindName will often not find these controls because they exist in a different namescope. Hope you find this useful, if not I’m just glad to be able to link to this blog in future stackoverflow answers.

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  • How do I optimize searching for the nearest point?

    - by Rootosaurus
    For a little project of mine I'm trying to implement a space colonization algorithm in order to grow trees. The current implementation of this algorithm works fine. But I have to optimize the whole thing in order to make it generate faster. I work with 1 to 300K of random attraction points to generate one tree, and it takes a lot of time to compute and compare distances between attraction points and tree node in order to keep only the closest treenode for an attraction point. So I was wondering if some solutions exist (I know they must exist) in order to avoid the time loss looping on each tree node for each attraction point to find the closest... and so on until the tree is finished.

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  • reconstructing a tree from its preorder and postorder lists.

    - by NomeN
    Consider the situation where you have two lists of nodes of which all you know is that one is a representation of a preorder traversal of some tree and the other a representation of a postorder traversal of the same tree. I believe it is possible to reconstruct the tree exactly from these two lists, and I think I have an algorithm to do it, but have not proven it. As this will be a part of a masters project I need to be absolutely certain that it is possible and correct (Mathematically proven). However it will not be the focus of the project, so I was wondering if there is a source out there (i.e. paper or book) I could quote for the proof. (Maybe in TAOCP? anybody know the section possibly?) In short, I need a proven algorithm in a quotable resource that reconstructs a tree from its pre and post order traversals. Note: The tree in question will probably not be binary, or balanced, or anything that would make it too easy. Note2: Using only the preorder or the postorder list would be even better, but I do not think it is possible. Note3: A node can have any amount of children. Note4: I only care about the order of siblings. Left or right does not matter when there is only one child.

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  • What is the most efficient/elegant way to parse a flat table into a tree?

    - by Tomalak
    Assume you have a flat table that stores an ordered tree hierarchy: Id Name ParentId Order 1 'Node 1' 0 10 2 'Node 1.1' 1 10 3 'Node 2' 0 20 4 'Node 1.1.1' 2 10 5 'Node 2.1' 3 10 6 'Node 1.2' 1 20 What minimalistic approach would you use to output that to HTML (or text, for that matter) as a correctly ordered, correctly intended tree? Assume further you only have basic data structures (arrays and hashmaps), no fancy objects with parent/children references, no ORM, no framework, just your two hands. The table is represented as a result set, which can be accessed randomly. Pseudo code or plain English is okay, this is purely a conceptional question. Bonus question: Is there a fundamentally better way to store a tree structure like this in a RDBMS? EDITS AND ADDITIONS To answer one commenter's (Mark Bessey's) question: A root node is not necessary, because it is never going to be displayed anyway. ParentId = 0 is the convention to express "these are top level". The Order column defines how nodes with the same parent are going to be sorted. The "result set" I spoke of can be pictured as an array of hashmaps (to stay in that terminology). For my example was meant to be already there. Some answers go the extra mile and construct it first, but thats okay. The tree can be arbitrarily deep. Each node can have N children. I did not exactly have a "millions of entries" tree in mind, though. Don't mistake my choice of node naming ('Node 1.1.1') for something to rely on. The nodes could equally well be called 'Frank' or 'Bob', no naming structure is implied, this was merely to make it readable. I have posted my own solution so you guys can pull it to pieces.

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  • What data is actually stored in a B-tree database in CouchDB?

    - by Andrey Vlasovskikh
    I'm wondering what is actually stored in a CouchDB database B-tree? The CouchDB: The Definitive Guide tells that a database B-tree is used for append-only operations and that a database is stored in a single B-tree (besides per-view B-trees). So I guess the data items that are appended to the database file are revisions of documents, not the whole documents: +---------|### ... | | +------|###|------+ ... ---+ | | | | +------+ +------+ +------+ +------+ | doc1 | | doc2 | | doc1 | ... | doc1 | | rev1 | | rev1 | | rev2 | | rev7 | +------+ +------+ +------+ +------+ Is it true? If it is true, then how the current revision of a document is determined based on such a B-tree? Doesn't it mean, that CouchDB needs a separate "view" database for indexing current revisions of documents to preserve O(log n) access? Wouldn't it lead to race conditions while building such an index? (as far as I know, CouchDB uses no write locks).

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  • Simple Navigation In Windows Phone 7

    - by PeterTweed
    Take the Slalom Challenge at www.slalomchallenge.com! When moving to the mobile platform all applications need to be able to provide different views.  Navigating around views in Windows Phone 7 is a very easy thing to do.  This post will introduce you to the simplest technique for navigation in Windows Phone 7 apps. Steps: 1.     Create a new Windows Phone Application project. 2.     In the MainPage.xaml file copy the following xaml into the ContentGrid Grid:             <StackPanel Orientation="Vertical" VerticalAlignment="Center"  >                 <TextBox Name="ValueTextBox" Width="200" ></TextBox>                 <Button Width="200" Height="30" Content="Next Page" Click="Button_Click"></Button>             </StackPanel> This gives a text box for the user to enter text and a button to navigate to the next page. 3.     Copy the following event handler code to the MainPage.xaml.cs file:         private void Button_Click(object sender, RoutedEventArgs e)         {             NavigationService.Navigate(new Uri( string.Format("/SecondPage.xaml?val={0}", ValueTextBox.Text), UriKind.Relative));         }   The event handler uses the NavigationService.Navigate() function.  This is what makes the navigation to another page happen.  The function takes a Uri parameter with the name of the page to navigate to and the indication that it is a relative Uri to the current page.  Note also the querystring is formatted with the value entered in the ValueTextBox control – in a similar manner to a standard web querystring. 4.     Add a new Windows Phone Portrait Page to the project named SecondPage.xaml. 5.     Paste the following XAML in the ContentGrid Grid in SecondPage.xaml:             <Button Name="GoBackButton" Width="200" Height="30" Content="Go Back" Click="Button_Click"></Button>   This provides a button to navigate back to the first page. 6.     Copy the following event handler code to the SecondPage.xaml.cs file:         private void Button_Click(object sender, RoutedEventArgs e)         {             NavigationService.GoBack();         } This tells the application to go back to the previously displayed page. 7.     Add the following code to the constructor in SecondPage.xaml.cs:             this.Loaded += new RoutedEventHandler(SecondPage_Loaded); 8.     Add the following loaded event handler to the SecondPage.xaml.cs file:         void SecondPage_Loaded(object sender, RoutedEventArgs e)         {             if (NavigationContext.QueryString["val"].Length > 0)                 MessageBox.Show(NavigationContext.QueryString["val"], "Data Passed", MessageBoxButton.OK);             else                 MessageBox.Show("{Empty}!", "Data Passed", MessageBoxButton.OK);         }   This code pops up a message box displaying either the text entered on the first page or the message “{Empty}!” if no text was entered. 9.     Run the application, enter some text in the text box and click on the next page button to see the application in action:   Congratulations!  You have created a new Windows Phone 7 application with page navigation.

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  • How to automate detection of out of order tab navigation in Qt dialogs?

    - by WilliamKF
    Typically, a dialog wishes to have tab navigation proceed in an orderly fashion through a dialog that roughly corresponds to the order of reading a book. When new fields are added to a dialog by engineers on a team, the new widgets can often not be inserted in tab correct order. Can anyone think of a way to automate the detection of out of tab navigation order widgets within a dialog?

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  • Project Navigation and File Nesting in ASP.NET MVC Projects

    - by Rick Strahl
    More and more I’m finding myself getting lost in the files in some of my larger Web projects. There’s so much freaking content to deal with – HTML Views, several derived CSS pages, page level CSS, script libraries, application wide scripts and page specific script files etc. etc. Thankfully I use Resharper and the Ctrl-T Go to Anything which autocompletes you to any file, type, member rapidly. Awesome except when I forget – or when I’m not quite sure of the name of what I’m looking for. Project navigation is still important. Sometimes while working on a project I seem to have 30 or more files open and trying to locate another new file to open in the solution often ends up being a mental exercise – “where did I put that thing?” It’s those little hesitations that tend to get in the way of workflow frequently. To make things worse most NuGet packages for client side frameworks and scripts, dump stuff into folders that I generally don’t use. I’ve never been a fan of the ‘Content’ folder in MVC which is just an empty layer that doesn’t serve much of a purpose. It’s usually the first thing I nuke in every MVC project. To me the project root is where the actual content for a site goes – is there really a need to add another folder to force another path into every resource you use? It’s ugly and also inefficient as it adds additional bytes to every resource link you embed into a page. Alternatives I’ve been playing around with different folder layouts recently and found that moving my cheese around has actually made project navigation much easier. In this post I show a couple of things I’ve found useful and maybe you find some of these useful as well or at least get some ideas what can be changed to provide better project flow. The first thing I’ve been doing is add a root Code folder and putting all server code into that. I’m a big fan of treating the Web project root folder as my Web root folder so all content comes from the root without unneeded nesting like the Content folder. By moving all server code out of the root tree (except for Code) the root tree becomes a lot cleaner immediately as you remove Controllers, App_Start, Models etc. and move them underneath Code. Yes this adds another folder level for server code, but it leaves only code related things in one place that’s easier to jump back and forth in. Additionally I find myself doing a lot less with server side code these days, more with client side code so I want the server code separated from that. The root folder itself then serves as the root content folder. Specifically I have the Views folder below it, as well as the Css and Scripts folders which serve to hold only common libraries and global CSS and Scripts code. These days of building SPA style application, I also tend to have an App folder there where I keep my application specific JavaScript files, as well as HTML View templates for client SPA apps like Angular. Here’s an example of what this looks like in a relatively small project: The goal is to keep things that are related together, so I don’t end up jumping around so much in the solution to get to specific project items. The Code folder may irk some of you and hark back to the days of the App_Code folder in non Web-Application projects, but these days I find myself messing with a lot less server side code and much more with client side files – HTML, CSS and JavaScript. Generally I work on a single controller at a time – once that’s open it’s open that’s typically the only server code I work with regularily. Business logic lives in another project altogether, so other than the controller and maybe ViewModels there’s not a lot of code being accessed in the Code folder. So throwing that off the root and isolating seems like an easy win. Nesting Page specific content In a lot of my existing applications that are pure server side MVC application perhaps with some JavaScript associated with them , I tend to have page level javascript and css files. For these types of pages I actually prefer the local files stored in the same folder as the parent view. So typically I have a .css and .js files with the same name as the view in the same folder. This looks something like this: In order for this to work you have to also make a configuration change inside of the /Views/web.config file, as the Views folder is blocked with the BlockViewHandler that prohibits access to content from that folder. It’s easy to fix by changing the path from * to *.cshtml or *.vbhtml so that view retrieval is blocked:<system.webServer> <handlers> <remove name="BlockViewHandler"/> <add name="BlockViewHandler" path="*.cshtml" verb="*" preCondition="integratedMode" type="System.Web.HttpNotFoundHandler" /> </handlers> </system.webServer> With this in place, from inside of your Views you can then reference those same resources like this:<link href="~/Views/Admin/QuizPrognosisItems.css" rel="stylesheet" /> and<script src="~/Views/Admin/QuizPrognosisItems.js"></script> which works fine. JavaScript and CSS files in the Views folder deploy just like the .cshtml files do and can be referenced from this folder as well. Making this happen is not really as straightforward as it should be with just Visual Studio unfortunately, as there’s no easy way to get the file nesting from the VS IDE directly (you have to modify the .csproj file). However, Mads Kristensen has a nice Visual Studio Add-in that provides file nesting via a short cut menu option. Using this you can select each of the ‘child’ files and then nest them under a parent file. In the case above I select the .js and .css files and nest them underneath the .cshtml view. I was even toying with the idea of throwing the controller.cs files into the Views folder, but that’s maybe going a little too far :-) It would work however as Visual Studio doesn’t publish .cs files and the compiler doesn’t care where the files live. There are lots of options and if you think that would make life easier it’s another option to help group related things together. Are there any downside to this? Possibly – if you’re using automated minification/packaging tools like ASP.NET Bundling or Grunt/Gulp with Uglify, it becomes a little harder to group script and css files for minification as you may end up looking in multiple folders instead of a single folder. But – again that’s a one time configuration step that’s easily handled and much less intrusive then constantly having to search for files in your project. Client Side Folders The particular project shown above in the screen shots above is a traditional server side ASP.NET MVC application with most content rendered into server side Razor pages. There’s a fair amount of client side stuff happening on these pages as well – specifically several of these pages are self contained single page Angular applications that deal with 1 or maybe 2 separate views and the layout I’ve shown above really focuses on the server side aspect where there are Razor views with related script and css resources. For applications that are more client centric and have a lot more script and HTML template based content I tend to use the same layout for the server components, but the client side code can often be broken out differently. In SPA type applications I tend to follow the App folder approach where all the application pieces that make the SPA applications end up below the App folder. Here’s what that looks like for me – here this is an AngularJs project: In this case the App folder holds both the application specific js files, and the partial HTML views that get loaded into this single SPA page application. In this particular Angular SPA application that has controllers linked to particular partial views, I prefer to keep the script files that are associated with the views – Angular Js Controllers in this case – with the actual partials. Again I like the proximity of the view with the main code associated with the view, because 90% of the UI application code that gets written is handled between these two files. This approach works well, but only if controllers are fairly closely aligned with the partials. If you have many smaller sub-controllers or lots of directives where the alignment between views and code is more segmented this approach starts falling apart and you’ll probably be better off with separate folders in js folder. Following Angular conventions you’d have controllers/directives/services etc. folders. Please note that I’m not saying any of these ways are right or wrong  – this is just what has worked for me and why! Skipping Project Navigation altogether with Resharper I’ve talked a bit about project navigation in the project tree, which is a common way to navigate and which we all use at least some of the time, but if you use a tool like Resharper – which has Ctrl-T to jump to anything, you can quickly navigate with a shortcut key and autocomplete search. Here’s what Resharper’s jump to anything looks like: Resharper’s Goto Anything box lets you type and quick search over files, classes and members of the entire solution which is a very fast and powerful way to find what you’re looking for in your project, by passing the solution explorer altogether. As long as you remember to use (which I sometimes don’t) and you know what you’re looking for it’s by far the quickest way to find things in a project. It’s a shame that this sort of a simple search interface isn’t part of the native Visual Studio IDE. Work how you like to work Ultimately it all comes down to workflow and how you like to work, and what makes *you* more productive. Following pre-defined patterns is great for consistency, as long as they don’t get in the way you work. A lot of the default folder structures in Visual Studio for ASP.NET MVC were defined when things were done differently. These days we’re dealing with a lot more diverse project content than when ASP.NET MVC was originally introduced and project organization definitely is something that can get in the way if it doesn’t fit your workflow. So take a look and see what works well and what might benefit from organizing files differently. As so many things with ASP.NET, as things evolve and tend to get more complex I’ve found that I end up fighting some of the conventions. The good news is that you don’t have to follow the conventions and you have the freedom to do just about anything that works for you. Even though what I’ve shown here diverges from conventions, I don’t think anybody would stumble over these relatively minor changes and not immediately figure out where things live, even in larger projects. But nevertheless think long and hard before breaking those conventions – if there isn’t a good reason to break them or the changes don’t provide improved workflow then it’s not worth it. Break the rules, but only if there’s a quantifiable benefit. You may not agree with how I’ve chosen to divert from the standard project structures in this article, but maybe it gives you some ideas of how you can mix things up to make your existing project flow a little nicer and make it easier to navigate for your environment. © Rick Strahl, West Wind Technologies, 2005-2014Posted in ASP.NET  MVC   Tweet !function(d,s,id){var js,fjs=d.getElementsByTagName(s)[0];if(!d.getElementById(id)){js=d.createElement(s);js.id=id;js.src="//platform.twitter.com/widgets.js";fjs.parentNode.insertBefore(js,fjs);}}(document,"script","twitter-wjs"); (function() { var po = document.createElement('script'); po.type = 'text/javascript'; po.async = true; po.src = 'https://apis.google.com/js/plusone.js'; var s = document.getElementsByTagName('script')[0]; s.parentNode.insertBefore(po, s); })();

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  • Google Rolls Out a New and Compact Navigation Bar

    - by Jason Fitzpatrick
    Earlier this spring Google introduced the black navigation bar; now they’ve updated the bar to take up less space and be more useful. Although the black bar is useful in-so-far as it gives you quick access to Google services (useful, of course, only if you use those services) the new navigation bar–seen in the video above–includes an improved layout. Rather than use the bar space to spread out links which the user may or may not use the service links are now tucked into a mouse-over menu accessed by hovering on the Google logo. The majority of the space previously just taken up by links and the black bar itself is now a a search box. If you don’t already see the new interface, look for it to appear in your Google account within the next few days. Hit up the link below to read the official announcement. The Next Stage In Our Redesign [The Official Google Blog] HTG Explains: Understanding Routers, Switches, and Network Hardware How to Use Offline Files in Windows to Cache Your Networked Files Offline How to See What Web Sites Your Computer is Secretly Connecting To

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  • Help me understand Inorder Traversal without using recursion

    - by vito
    I am able to understand preorder traversal without using recursion, but I'm having a hard time with inorder traversal. I just don't seem to get it, perhaps, because I haven't understood the inner working of recursion. This is what I've tried so far: def traverseInorder(node): lifo = Lifo() lifo.push(node) while True: if node is None: break if node.left is not None: lifo.push(node.left) node = node.left continue prev = node while True: if node is None: break print node.value prev = node node = lifo.pop() node = prev if node.right is not None: lifo.push(node.right) node = node.right else: break The inner while-loop just doesn't feel right. Also, some of the elements are getting printed twice; may be I can solve this by checking if that node has been printed before, but that requires another variable, which, again, doesn't feel right. Where am I going wrong? I haven't tried postorder traversal, but I guess it's similar and I will face the same conceptual blockage there, too. Thanks for your time! P.S.: Definitions of Lifo and Node: class Node: def __init__(self, value, left=None, right=None): self.value = value self.left = left self.right = right class Lifo: def __init__(self): self.lifo = () def push(self, data): self.lifo = (data, self.lifo) def pop(self): if len(self.lifo) == 0: return None ret, self.lifo = self.lifo return ret

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  • Algorithm for evaluating nested logical expression

    - by TravelingSalesman
    I have a logical expression that I would like to evaluate. The expression can be nested and consists of T (True) or F (False) and parenthesis. The parenthesis "(" means "logical OR". Two terms TF beside each others (or any other two combinations beside each others), should be ANDED (Logical AND). For example, the expression: ((TFT)T) = true I need an algorithm for solving this problem. I thought of converting the expression first to disjunctive or conjunctive normal form and then I can easily evaluate the expression. However, I couldn't find an algorithm that normalizes the expression. Any suggestions? Thank you. The problem statement can be found here: https://icpcarchive.ecs.baylor.edu/index.php?option=com_onlinejudge&Itemid=2&category=378&page=show_problem&problem=2967

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  • [BST] Deletion procedure

    - by Metz
    Hi all. Consider the deletion procedure on a BST, when the node to delete has two children. Let's say i always replace it with the node holding the minimum key in its right subtree. The question is: is this procedure commutative? That is, deleting x and then y has the same result than deleting first y and then x? I think the answer is no, but i can't find a counterexample, nor figure out any valid reasoning. Thank you. EDIT: Maybe i've got to be clearer. Consider the transplant(node x, node y) procedure: it replace x with y (and its subtree). So, if i want to delete a node (say x) which has two children i replace it with the node holding the minimum key in its right subtree: y = minimum(x.right) transplant(y, y.right) // extracts the minimum (it doesn't have left child) y.right = x.right y.left = x.left transplant(x,y) The question was how to prove the procedure above is not commutative.

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  • New Sample Demonstrating the Traversing of Tree Bindings

    - by Duncan Mills
    A technique that I seem to use a fair amount, particularly in the construction of dynamic UIs is the use of a ADF Tree Binding to encode a multi-level master-detail relationship which is then expressed in the UI in some kind of looping form – usually a series of nested af:iterators, rather than the conventional tree or treetable. This technique exploits two features of the treebinding. First the fact that an treebinding can return both a collectionModel as well as a treeModel, this collectionModel can be used directly by an iterator. Secondly that the “rows” returned by the collectionModel themselves contain an attribute called .children. This attribute in turn gives access to a collection of all the children of that node which can also be iterated over. Putting this together you can represent the data encoded into a tree binding in all sorts of ways. As an example I’ve put together a very simple sample based on the HT schema and uploaded it to the ADF Sample project. It produces this UI: The important code is shown here for a Region -> Country -> Location Hierachy: <af:iterator id="i1" value="#{bindings.AllRegions.collectionModel}" var="rgn"> <af:showDetailHeader text="#{rgn.RegionName}" disclosed="true" id="sdh1"> <af:iterator id="i2" value="#{rgn.children}" var="cnty">     <af:showDetailHeader text="#{cnty.CountryName}" disclosed="true" id="sdh2">       <af:iterator id="i3" value="#{cnty.children}" var="loc">         <af:panelList id="pl1">         <af:outputText value="#{loc.City}" id="ot3"/>           </af:panelList>         </af:iterator>       </af:showDetailHeader>     </af:iterator>   </af:showDetailHeader> </af:iterator>  You can download the entire sample from here:

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  • Failed to load viewstate.The control tree into which viewstate is being loaded...etc

    - by alaa9jo
    Two days ago,a colleague of mine tried to publish an asp.net website (which is built in VS2008 using framework 3.5) to our server,he configured everything in IIS (he made sure that the selected asp.net version is 2.0) and launched the website..at first it was working great but when he tried to click on a specific treeview...BOOM..: "Failed to load viewstate. The control tree into which viewstate is being loaded must match the control tree that was used to save viewstate during the previous request. For example, when adding controls dynamically, the controls added during a post-back must match the type and position of the controls added during the initial request." In that page there were these control: a TreeView and a Placeholder,when the user selects any node then it's controls will be created dynamically into that placeholder..for the first time it's working fine but when (s)he select another node then that issue appears. He called me to help him with this issue,for me this is the first time I see such an issue,scratch my head then I decided to eliminate the possibilities of this issue one by one,at the development machine it's working perfectly,he published the website at the local IIS and again..it's working perfectly,I took a copy of the website and published it into my laptop but no issues at all,so this is means that it's not an issue in the code. So there is something missing/wrong in our server [it has Windows Server 2003],we went to the server and checked on the web-config and the configurations on IIS...nothing wrong so far,so I decided to check if the framework 3.5 is installed or not and the answer: it wasn't installed Of course he assumed that it was installed and there was nothing to tell if it wasn't from the "ASP.Net version" in IIS because frameworks 3.0 and 3.5 will not be listed there [2.0 will be listed there instead],the only way to check if it was installed or not is to search for the framework in this path:[WINDOWS Folder]\Microsoft.NET\Framework or check if it was installed in Add or remove programs. The obvious solution for his case: We installed Framework 3.5 SP1 into our server,did a restart to the machine and it worked ! If anyone faced the same issue and solved it using the same solution or with a different one please post it here to share experience.

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  • How exactly is an Abstract Syntax Tree created?

    - by Howcan
    I think I understand the goal of an AST, and I've build a couple of tree structures before, but never an AST. I'm mostly confused because the nodes are text and not number, so I can't think of a nice way to input a token/string as I'm parsing some code. For example, when I looked at diagrams of AST's, the variable and its value were leaf nodes to an equal sign. This makes perfect sense to me, but how would I go about implementing this? I guess I can do it case by case, so that when I stumble upon an "=" I use that as a node, and add the value parsed before the "=" as the leaf. It just seems wrong, because I'd probably have to make cases for tons and tons of things, depending on the syntax. And then I came upon another problem, how is the tree traversed? Do I go all the way down the height, and go back up a node when I hit the bottom, and do the same for it's neighbor? I've seen tons of diagrams on ASTs, but I couldn't find a fairly simple example of one in code, which would probably help.

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