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• Can I make Puppet's module-to-file mapping to start searching at the top of the modules tree?

  - by John Siracusa

  Consider these two Puppet module files: # File modules/a/manifests/b/c.pp class a::b::c { include b::c } # File modules/b/manifests/c.pp class b::c { notify { "In b::c": } } It seems that when Puppet hits the include b::c directive in class a::b::c, it searches for the corresponding *.pp file by looking backwards from the current class and decides that it find the correct file located at ../../b/c.pp. In other words, it resolves b::c to the same *.pp file that the include b::c statement appears in: modules/a/manifests/b/c.pp I expected it (and would like it) to instead find and load the file modules/b/manifests/c.pp. Is there a way to make Puppet do this? If not, it seems to me that module names may not contain any other module names anywhere within them, which is a pretty surprising restriction.

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• Understanding Microsoft Word Formatting Behavior. Does anyone?

  - by deemer

  This isn't a question about how to do something (well, not directly), but rather an inquiry to see if anyone understands why MS Word behaves the way it does with respect to formatting from a design perspective. This is also admittedly a rant about Word. This is a question that has plagued me, well, every time I open a document in Word, and covers a lot of individual topics, so I'll restrict the discussion here to two concrete behaviors that baffle me. 1) Backspacing over whitespace changes the format of preceding text. This seems to most often occur when the preceding text is a header or list number. The strangest thing about this is the new format of the changed text usually doesn't appear anywhere else in the document. 2) Numbered lists count almost at random. I am working on a document today where the list numbers count as follows: 1, 2, 2, 3, 3. The lettering in the sublists go like this 1: a, 2: a, 2: b c d, 3: e f g, 3: a. Clicking on each number or letter highlights the other numbers or letters that Word thinks it is related to, which are scattered around the document pretty heavily. Attempts to renumber the list have so far proven fruitless, as Word seems to maintain these associations through clipboard copies, etc. Why could this even happen?

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• How to make NumLock behavior just like in Windows?

  - by ???

  The NumLock and the keypad is so weired in Ubuntu. I have two computers, A is a desktop, with USB keyboard, B is a laptop, with laptop keyboard and another USB keyboard. On the desktop A, whether the NumLock is on or off, the number keys on the keypad just don't work. Also the NumLock LED is always off. The logs shown in xev: KeyPress event, serial 36, synthetic NO, window 0x6800001, root 0xb0, subw 0x0, time 9541332, (172,-12), root:(1846,452), state 0x0, keycode 77 (keysym 0xff7f, Num_Lock), same_screen YES, XLookupString gives 0 bytes: XmbLookupString gives 0 bytes: XFilterEvent returns: False KeyRelease event, serial 36, synthetic NO, window 0x6800001, root 0xb0, subw 0x0, time 9541412, (172,-12), root:(1846,452), state 0x0, keycode 77 (keysym 0xff7f, Num_Lock), same_screen YES, XLookupString gives 0 bytes: XFilterEvent returns: False And on the laptop B, I found that, when the NumLock is on, then many key combinations won't work. For example, generally Ctrl-A is used to select all, but it won't work when NumLock is on. The logs shown in xev: (no log when pressed Fn+NumLock on the laptop keyboard) Logs when pressed the NumLock on the USB keyboard: (Switch On) KeyPress event, serial 40, synthetic NO, window 0xb600001, root 0xac, subw 0x0, time 22187595, (102,107), root:(1198,133), state 0x10, keycode 77 (keysym 0xff7f, Num_Lock), same_screen YES, XLookupString gives 0 bytes: XmbLookupString gives 0 bytes: XFilterEvent returns: False PropertyNotify event, serial 40, synthetic NO, window 0xb600001, atom 0x1b8 (XKLAVIER_STATE), time 22187601, state PropertyNewValue KeyRelease event, serial 40, synthetic NO, window 0xb600001, root 0xac, subw 0x0, time 22187723, (102,107), root:(1198,133), state 0x10, keycode 77 (keysym 0xff7f, Num_Lock), same_screen YES, XLookupString gives 0 bytes: XFilterEvent returns: False (Switch Off) KeyPress event, serial 40, synthetic NO, window 0xb600001, root 0xac, subw 0x0, time 22187899, (102,107), root:(1198,133), state 0x0, keycode 77 (keysym 0xff7f, Num_Lock), same_screen YES, XLookupString gives 0 bytes: XmbLookupString gives 0 bytes: XFilterEvent returns: False PropertyNotify event, serial 40, synthetic NO, window 0xb600001, atom 0x1b8 (XKLAVIER_STATE), time 22187904, state PropertyNewValue KeyRelease event, serial 40, synthetic NO, window 0xb600001, root 0xac, subw 0x0, time 22188003, (102,107), root:(1198,133), state 0x10, keycode 77 (keysym 0xff7f, Num_Lock), same_screen YES, XLookupString gives 0 bytes: XFilterEvent returns: False

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• Beaglebone Black running Debian, does device tree overlay act as an api?

  - by user3953989

  This maybe more of a Linux specific question but... I've been reading many tutorials and it seems that you can use JavaScript, Python, and C++ to write code for the Beaglebone Black(BBB). It looks like the way C++ interfaces with the BBB hardware is via reading/writing text files on the OS while Python has it's own library. All the C++ examples out there control the GPIO and PWM via reading/writing to text files. Is this the only way to access the hardware or just how Linux does drivers?

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• What is the proper query to get all the children in a tree?

  - by Nathan Adams

  Lets say I have the following MySQL structure: CREATE TABLE `domains` ( `id` INT(10) UNSIGNED NOT NULL AUTO_INCREMENT, `domain` CHAR(50) NOT NULL, `parent` INT(11) DEFAULT NULL, PRIMARY KEY (`id`) ) ENGINE=MYISAM AUTO_INCREMENT=10 DEFAULT CHARSET=latin1 insert into `domains`(`id`,`domain`,`parent`) values (1,'.com',0); insert into `domains`(`id`,`domain`,`parent`) values (2,'example.com',1); insert into `domains`(`id`,`domain`,`parent`) values (3,'sub1.example.com',2); insert into `domains`(`id`,`domain`,`parent`) values (4,'sub2.example.com',2); insert into `domains`(`id`,`domain`,`parent`) values (5,'s1.sub1.example.com',3); insert into `domains`(`id`,`domain`,`parent`) values (6,'s2.sub1.example.com',3); insert into `domains`(`id`,`domain`,`parent`) values (7,'sx1.s1.sub1.example.com',5); insert into `domains`(`id`,`domain`,`parent`) values (8,'sx2.s2.sub1.example.com',6); insert into `domains`(`id`,`domain`,`parent`) values (9,'x.sub2.example.com',4); In my mind that is enough to emulate a simple tree structure: .com | example / \ sub1 sub2 ect My problem is that give sub1.example.com I want to know all the children of sub1.example.com without using multiple queries in my code. I have tried joining the table to itself and tried to use subqueries, I can't think of anything that will reveal all the children. At work we are using MPTT to keep in hierarchal order a list of domains/subdomains however, I feel that there is an easier way to do it. I did some digging and someone did something similar but they required the use of a function in MySQL. I don't think for something simple like this we would need a whole function. Maybe I am just dumb and not seeing some sort of obvious solution. Also, feel free to alter the structure.

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• Anybody seen this behavior with Sql Server Reporting Services, a 64bit OS and an Oracle datasource?

  - by dkackman

  I'm working on a Sql Server Reporting Services solution that queries across both a Sql Server data source and an Oracle 10g data source. My dev box is Windows 7 64bit with Sql Server 2008R2 and I'm hosting IIS7 and SSRS on that system for development; using VS.NET for designing the reports. I have been having errors when running the report where SSRS complains about loading the 32 bit Oracle client in a 64bit process. There a number of threads out there about how to solve that. The thing is, they all come down to making sure you have the 64bit Oracle, client which I do. The weird chain of events I have goes like this: Create initial Oracle datasource and wire up report (it works) Edit Oracle datasource connection (it stops working with BadImageFormatException 32bit/64bit error message) uninstall and reinstall Oracle client (it works) Edit Oracle connection again (it stops working with BadImageFormatException 32bit/64bit error message) So short of reinstalling the client every time I change the connection string I am at a complete loss. Has anybody seen this sort of behavior? And if so what the heck am I doing wrong?

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• Is there any way to access files in your source tree in Android?

  - by Chris Thompson

  Hi all, This is a bit unorthodox but I'm trying to figure out if there's a way to access files stored in the src tree of my applications apk in Android. I'm trying to use i-Jetty (Jetty implementation for Android) and rather than use it as a separate application and manually download my war file, I'd rather just bake i-jetty in. However, in order to use (easily) standard html/jsp I need to be able to give it a document root, preferably within my application's apk file. I know Android specifically works to prevent you from accessing (freely) the stuff on the actual system so this may not be possible, but I'm thinking it might be possible to access something within the apk. One option to work around this would be to have all of the files stored in the res directory and then copy them to the sdcard on startup but this wouldn't allow me to automatically remove the files on uninstall. To give you an idea of what I've tried, currently, the html files are stored in org.webtext.android Context rootContext = new Context(server_, "/", Context.SESSIONS); rootContext.setResourceBase("org/webtext/webapp"); Returns a 404 error. final URL url = this.getClassLoader().getResource("org/webtext/webapp"); Context html = new WebAppContext(url.toExternalForm(), "/"); Blows up with a NullPointerException because no URL is returned from the getResource call. Any thoughts would be greatly appreciated! Thanks, Chris

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• Is a red-black tree my ideal data structure?

  - by Hugo van der Sanden

  I have a collection of items (big rationals) that I'll be processing. In each case, processing will consist of removing the smallest item in the collection, doing some work, and then adding 0-2 new items (which will always be larger than the removed item). The collection will be initialised with one item, and work will continue until it is empty. I'm not sure what size the collection is likely to reach, but I'd expect in the range 1M-100M items. I will not need to locate any item other than the smallest. I'm currently planning to use a red-black tree, possibly tweaked to keep a pointer to the smallest item. However I've never used one before, and I'm unsure whether my pattern of use fits its characteristics well. 1) Is there a danger the pattern of deletion from the left + random insertion will affect performance, eg by requiring a significantly higher number of rotations than random deletion would? Or will delete and insert operations still be O(log n) with this pattern of use? 2) Would some other data structure give me better performance, either because of the deletion pattern or taking advantage of the fact I only ever need to find the smallest item? Update: glad I asked, the binary heap is clearly a better solution for this case, and as promised turned out to be very easy to implement. Hugo

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• Implementation question involving implementing an interface

  - by Vivin Paliath

  I'm writing a set of collection classes for different types of Trees. I'm doing this as a learning exercise and I'm also hoping it turns out to be something useful. I really want to do this the right way and so I've been reading Effective Java and I've also been looking at the way Joshua Bloch implemented the collection classes by looking at the source. I seem to have a fair idea of what is being done, but I still have a few things to sort out. I have a Node<T> interface and an AbstractNode<T> class that implements the Node interface. I then created a GenericNode<T> (a node that can have 0 to n children, and that is part of an n-ary tree) class that extends AbstractNode<T> and implements Node<T>. This part was easy. Next, I created a Tree<T> interface and an AbstractTree<T> class that implements the Tree<T> interface. After that, I started writing a GenericTree<T> class that extends AbstractTree<T> and implements Tree<T>. This is where I started having problems. As far as the design is concerned, a GenericTree<T> can only consist of nodes of type GenericTreeNode<T>. This includes the root. In my Tree<T> interface I have: public interface Tree<T> { void setRoot(Node<T> root); Node<T> getRoot(); List<Node<T>> postOrder(); ... rest omitted ... } And, AbstractTree<T> implements this interface: public abstract class AbstractTree<T> implements Tree<T> { protected Node<T> root; protected AbstractTree() { } protected AbstractTree(Node<T> root) { this.root = root; } public void setRoot(Node<T> root) { this.root = root; } public Node<T> getRoot() { return this.root; } ... rest omitted ... } In GenericTree<T>, I can have: public GenericTree(Node<T> root) { super(root); } But what this means is that you can create a generic tree using any subtype of Node<T>. You can also set the root of a tree to any subtype of Node<T>. I want to be able to restrict the type of the node to the type of the tree that it can represent. To fix this, I can do this: public GenericTree(GenericNode<T> root) { super(root); } However, setRoot still accepts a parameter of type Node<T>. Which means a user can still create a tree with the wrong type of root node. How do I enforce this constraint? The only way I can think of doing is either: Do an instanceof which limits the check to runtime. I'm not a huge fan of this. Remove setRoot from the interface and have the base class implement this method. This means that it is not part of the contract and anyone who wants to make a new type of tree needs to remember to implement this method. Is there a better way? The second question I have concerns the return type of postOrder which is List<Node<T>>. This means that if a user is operating on a GenericTree<T> object and calls postOrder, he or she receives a list that consists of Node<T> objects. This means when iterating through (using a foreach construct) they would have perform an explicit cast to GenericNode<T> if they want to use methods that are only defined in that class. I don't like having to place this burden on the user. What are my options in this case? I can only think of removing the method from the interface and have the subclass implement this method making sure that it returns a list of appropriate subtype of Node<T>. However, this once again removes it from the contract and it's anyone who wants to create a new type of tree has to remember to implement this method. Is there a better way?

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• Why boost property tree write_json saves everything as string? Is it possible to change that?

  - by pprzemek

  I'm trying to serialize using boost property tree write_json, it saves everything as strings, it's not that data are wrong, but I need to cast them explicitly every time and I want to use them somewhere else. (like in python or other C++ json (non boost) library) here is some sample code and what I get depending on locale: boost::property_tree::ptree root, arr, elem1, elem2; elem1.put<int>("key0", 0); elem1.put<bool>("key1", true); elem2.put<float>("key2", 2.2f); elem2.put<double>("key3", 3.3); arr.push_back( std::make_pair("", elem1) ); arr.push_back( std::make_pair("", elem2) ); root.put_child("path1.path2", arr); std::stringstream ss; write_json(ss, root); std::string my_string_to_send_somewhare_else = ss.str(); and my_string_to_send_somewhere_else is sth. like this: { "path1" : { "path2" : [ { "key0" : "0", "key1" : "true" }, { "key2" : "2.2", "key3" : "3.3" } ] } } Is there anyway to save them as the values, like: "key1" : true or "key2" : 2.2 ?

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• Conventions for the behavior of double or triple "click to select text" features?

  - by John Sullivan

  Almost any mature program that involves text implements "double click to select the word" and, in some cases, "triple click to select additional stuff like an entire line" as a feature. I find these features useful but they are often inconsistent between programs. Example - some programs' double clicks do not select the ending space after a word, but most do. Some recognize the - character as the end of a word, others do not. SO likes to select the entire paragraph as I write this post when I triple click it, VS web developer 2005 has no triple click support, and ultra-edit 32 will select one line upon triple clicking. We could come up with innumerable inconsistencies about how double and triple click pattern matching is implemented across programs. I am concerned about how to implement this behavior in my program if nobody else has achieved a convention about how the pattern matching should work. My question is, does a convention (conventions? maybe an MS or Linux convention?) exist that dictates how these features are supposed to behave to the end user? What, if any, are they?

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• How can I SETF an element in a tree by an accessor?

  - by Willi Ballenthin

  We've been using Lisp in my AI course. The assignments I've received have involved searching and generating tree-like structures. For each assignment, I've ended up writing something like: (defun initial-state () (list 0 ; score nil ; children 0 ; value 0)) ; something else and building my functions around these "states", which are really just nested lists with some loosely defined structure. To make the structure more rigid, I've tried to write accessors, such as: (defun state-score ( state ) (nth 2 state)) This works for reading the value (which should be all I need to do in a nicely functional world. However, as time crunches, and I start to madly hack, sometimes I want a mutable structure). I don't seem to be able to SETF the returned ...thing (place? value? pointer?). I get an error with something like: (setf (state-score *state*) 10) Sometimes I seem to have a little more luck writing the accessor/mutator as a macro: (defmacro state-score ( state ) `(nth 2 ,state)) However I don't know why this should be a macro, so I certainly shouldn't write it as a macro (except that sometimes it works. Programming by coincidence is bad). What is an appropriate strategy to build up such structures? More importantly, where can I learn about whats going on here (what operations affect the memory in what way)?

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• Apache HttpClient 4.0. Weird behavior.

  - by Mikhail T

  Hello. I'm using Apache HttpClient 4.0 for my web crawler. The behavior i found strange is: i'm trying to get page via HTTP GET method and getting response about 404 HTTP error. But if i try to get that page using browser it's done successfully. Details: 1. I upload multipart form to server this way: HttpPost httpPost = new HttpPost("http://[host here]/in.php"); MultipartEntity entity = new MultipartEntity(HttpMultipartMode.BROWSER_COMPATIBLE); entity.addPart("method", new StringBody("post")); entity.addPart("key", new StringBody("223fwe0923fjf23")); FileBody fileBody = new FileBody(new File("photo.jpg"), "image/jpeg"); entity.addPart("file", fileBody); httpPost.setEntity(entity); HttpResponse response = httpClient.execute(httpPost); HttpEntity result = response.getEntity(); String responseString = ""; if (result != null) { InputStream inputStream = result.getContent(); byte[] buffer = new byte[1024]; while(inputStream.read(buffer) > 0) responseString += new String(buffer); result.consumeContent(); } Uppload succefully ends. I'm getting some results from web server: HttpGet httpGet = new HttpGet("http://[host here]/res.php?key="+myKey+"&action=get&id="+id); HttpResponse response = httpClient.execute(httpGet); HttpEntity entity = response.getEntity(); I'm getting ClientProtocolException while execute method run. I was debugging this situation with log4j. Server answers "404 Not Found". But my browser loads me that page with no problem. Can anybody help me? Thank you.

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• How do I swallow the dropdown behavior inside an Expander.Header?

  - by Peter Seale

  Hello, I would like to prevent an Expander from expanding/collapsing when users click inside the header area. This is basically the same question as Q 1396153, but I'd appreciate a more favorable answer :) Is there a non-invasive way to do this? I am not sure exactly how to attach behavior to the Expander.Header content to prevent mouseclicks. I'm willing to float in content outside the expander itself via a fixed grid layout, but I'm not keen on the solution. Ideas? XamlPad sample XAML: <Page xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:sys="clr-namespace:System;assembly=mscorlib" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" > <Expander> <Expander.Header><TextBlock>When I click this text, I don't want to trigger expansion/collapse! Only when I click the expander button do I want to trigger an expand/collapse!</TextBlock></Expander.Header> <Grid Background="Red" Height="100" Width="100" > </Grid> </Expander> </Page>

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• How do implement a breadth first traversal?

  - by not looking for answer

  //This is what I have. I thought pre-order was the same and mixed it up with depth first! import java.util.LinkedList; import java.util.Queue; public class Exercise25_1 { public static void main(String[] args) { BinaryTree tree = new BinaryTree(new Integer[] {10, 5, 15, 12, 4, 8 }); System.out.print("\nInorder: "); tree.inorder(); System.out.print("\nPreorder: "); tree.preorder(); System.out.print("\nPostorder: "); tree.postorder(); //call the breadth method to test it System.out.print("\nBreadthFirst:"); tree.breadth(); } } class BinaryTree { private TreeNode root; /** Create a default binary tree */ public BinaryTree() { } /** Create a binary tree from an array of objects */ public BinaryTree(Object[] objects) { for (int i = 0; i < objects.length; i++) { insert(objects[i]); } } /** Search element o in this binary tree */ public boolean search(Object o) { return search(o, root); } public boolean search(Object o, TreeNode root) { if (root == null) { return false; } if (root.element.equals(o)) { return true; } else { return search(o, root.left) || search(o, root.right); } } /** Return the number of nodes in this binary tree */ public int size() { return size(root); } public int size(TreeNode root) { if (root == null) { return 0; } else { return 1 + size(root.left) + size(root.right); } } /** Return the depth of this binary tree. Depth is the * number of the nodes in the longest path of the tree */ public int depth() { return depth(root); } public int depth(TreeNode root) { if (root == null) { return 0; } else { return 1 + Math.max(depth(root.left), depth(root.right)); } } /** Insert element o into the binary tree * Return true if the element is inserted successfully */ public boolean insert(Object o) { if (root == null) { root = new TreeNode(o); // Create a new root } else { // Locate the parent node TreeNode parent = null; TreeNode current = root; while (current != null) { if (((Comparable)o).compareTo(current.element) < 0) { parent = current; current = current.left; } else if (((Comparable)o).compareTo(current.element) > 0) { parent = current; current = current.right; } else { return false; // Duplicate node not inserted } } // Create the new node and attach it to the parent node if (((Comparable)o).compareTo(parent.element) < 0) { parent.left = new TreeNode(o); } else { parent.right = new TreeNode(o); } } return true; // Element inserted } public void breadth() { breadth(root); } // Implement this method to produce a breadth first // search traversal public void breadth(TreeNode root){ if (root == null) return; System.out.print(root.element + " "); breadth(root.left); breadth(root.right); } /** Inorder traversal */ public void inorder() { inorder(root); } /** Inorder traversal from a subtree */ private void inorder(TreeNode root) { if (root == null) { return; } inorder(root.left); System.out.print(root.element + " "); inorder(root.right); } /** Postorder traversal */ public void postorder() { postorder(root); } /** Postorder traversal from a subtree */ private void postorder(TreeNode root) { if (root == null) { return; } postorder(root.left); postorder(root.right); System.out.print(root.element + " "); } /** Preorder traversal */ public void preorder() { preorder(root); } /** Preorder traversal from a subtree */ private void preorder(TreeNode root) { if (root == null) { return; } System.out.print(root.element + " "); preorder(root.left); preorder(root.right); } /** Inner class tree node */ private class TreeNode { Object element; TreeNode left; TreeNode right; public TreeNode(Object o) { element = o; } } }

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• Which templating languages output HTML *as a tree of nodes*?

  - by alamar

  HTML is a tree of nodes, before all. It's not just a text. However, most templating engines handle their input and output as it was just a text; they don't care what happens around their tags, their {$foo}'s and <% bar() %>'s; also they don't care about what are they outputting. Sometimes they happen to produce a correct html, but that's just a coincidence; they didn't aim for that, all they wanted is to replace some funny marks in the text stream with their evaluation. There are a few templating engines which do treat their output as a set of nodes; XSLT and Haml come to mind. For some tasks, this has advantages: for example, you can automatically reformat (like, delete all empty text nodes; auto-indent; word-wrap). The result is guaranteed to be a correct xml/sgml unless you use a strict subset of operations that can break that. Also, such templating engine would automatically quote strings, differently in text nodes and in attributes, because it strictly knows whether you're writing an attribute or a text node. Moreover, it can conditionally remove a node from output because it knows where it does begin and end, which is useful, and do other non-trivial node operations. You might not like XSLT for its verbosiness or functionalness, but it's damn helps that your template is xmllint-able XML, and your output is a good sgml/xml. So the question is: Which template engines do you know that treat their output as a set of correct nodes, not just an unstructured text? I know XSLT, Haml and some obscure python-based one. Moar!

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• How do I add an object to a binary tree based on the value of a member variable?

  - by Max

  How can I get a specific value from an object? I'm trying to get a value of an instance for eg. ListOfPpl newListOfPpl = new ListOfPpl(id, name, age); Object item = newListOfPpl; How can I get a value of name from an Object item?? Even if it is easy or does not interest you can anyone help me?? Edited: I was trying to build a binary tree contains the node of ListOfPpl, and need to sort it in the lexicographic. Here's my code for insertion on the node. Any clue?? public void insert(Object item){ Node current = root; Node follow = null; if(!isEmpty()){ root = new Node(item, null, null); return; }boolean left = false, right = false; while(current != null){ follow = current; left = false; right = false; //I need to compare and sort it if(item.compareTo(current.getFighter()) < 0){ current = current.getLeft(); left = true; }else { current = current.getRight(); right = true; } }if(left) follow.setLeft(new Node(item, null, null)); else follow.setRight(new Node(item, null, null)); }

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• EF code first error "The specified index already exists. [ IX_Id ]" for object tree

  - by PascalN

  Using EF code first 4.3 I'm trying to model an object tree with a required-required relationships and a required-optional relationships. Here is a simple representation of those classes public class Top { public int Id { get; set; } public virtual Middle Middle { get; set; } } public class Middle { public int Id { get; set; } public virtual Child Child { get; set; } } public class Child { public int Id { get; set; } } Here is the OnModelCreating code modelBuilder.Entity<Top>().HasRequired(t => t.Middle).WithRequiredPrincipal().WillCascadeOnDelete(); modelBuilder.Entity<Middle>().HasRequired(t => t.Child).WithOptional().WillCascadeOnDelete(); This produces the error "The specified index already exists. [ IX_Id ]" on SQLCE After checking the db schema, both model binder fluent API configuration lines create an index IX_Id on the table Middles. Does anyone know how to work around that problem? Is there a way to set the index name? Thank you! Pascal

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• Can you explain this generics behavior and if I have a workaround?

  - by insta

  Sample program below: using System; using System.Collections.Generic; using System.Linq; using System.Text; namespace GenericsTest { class Program { static void Main(string[] args) { IRetrievable<int, User> repo = new FakeRepository(); Console.WriteLine(repo.Retrieve(35)); } } class User { public int Id { get; set; } public string Name { get; set; } } class FakeRepository : BaseRepository<User>, ICreatable<User>, IDeletable<User>, IRetrievable<int, User> { // why do I have to implement this here, instead of letting the // TKey generics implementation in the baseclass handle it? //public User Retrieve(int input) //{ // throw new NotImplementedException(); //} } class BaseRepository<TPoco> where TPoco : class,new() { public virtual TPoco Create() { return new TPoco(); } public virtual bool Delete(TPoco item) { return true; } public virtual TPoco Retrieve<TKey>(TKey input) { return null; } } interface ICreatable<TPoco> { TPoco Create(); } interface IDeletable<TPoco> { bool Delete(TPoco item); } interface IRetrievable<TKey, TPoco> { TPoco Retrieve(TKey input); } } This sample program represents the interfaces my actual program uses, and demonstrates the problem I'm having (commented out in FakeRepository). I would like for this method call to be generically handled by the base class (which in my real example is able to handle 95% of the cases given to it), allowing for overrides in the child classes by specifying the type of TKey explicitly. It doesn't seem to matter what parameter constraints I use for the IRetrievable, I can never get the method call to fall through to the base class. Also, if anyone can see an alternate way to implement this kind of behavior and get the result I'm ultimately looking for, I would be very interested to see it. Thoughts?

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• Is this Leftist Tree piece of code from Wikipedia correct?

  - by they changed my name

  Link public Node merge(Node x, Node y) { if(x == null) return y; if(y == null) return x; // if this was a max height biased leftist tree, then the // next line would be: if(x.element < y.element) if(x.element.compareTo(y.element) > 0) { // x.element > y.element Node temp = x; x = y; y = temp; } x.rightChild = merge(x.rightChild, y); if(x.leftChild == null) { // left child doesn't exist, so move right child to the left side x.leftChild = x.rightChild; x.rightChild = null; x.s = 1; } else { // left child does exist, so compare s-values if(x.leftChild.s < x.rightChild.s) { Node temp = x.leftChild; x.leftChild = x.rightChild; x.rightChild = temp; } // since we know the right child has the lower s-value, we can just // add one to its s-value x.s = x.rightChild.s + 1; } return x; } What makes me ask this question is: if(x.element.compareTo(y.element) > 0) { // x.element > y.element Node temp = x; x = y; y = temp; } Isn't that just not gonna work, since the references are only switched inside the method?

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• How do I code a tree of objects in Haskell with pointers to parent and children?

  - by axilmar

  I've got the following problem: I have a tree of objects of different classes where an action in the child class invalidates the parent. In imperative languages, it is trivial to do. For example, in Java: public class A { private List<B> m_children = new LinkedList<B>(); private boolean m_valid = true; public void invalidate() { m_valid = false; } public void addChild(B child) { m_children.add(child); child.m_parent = this; } } public class B { public A m_parent = null; private int m_data = 0; public void setData(int data) { m_data = 0; m_parent.invalidate(); } } public class Main { public static void main(String[] args) { A a = new A(); B b = new B(); b.setData(0); //invalidates A } } How do I do the above in Haskell? I cannot wrap my mind around this, since once I construct an object in Haskell, it cannot be changed. I would be much obliged if the relevant Haskell code is posted.

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• NTFS Issues in Windows 7 and 2008 R2 - 'Is it a Bug?'

  - by renewieldraaijer

  I have been using the various versions of the Microsoft Windows product line since NT4 and I really thought I knew the ins and outs about the NTFS filesystem by now. There were always a few rules of thumb to understand what happens if you move data around. These rules were: "If you copy data, the copied data will inherit the permissions of the location it is being copied to. The same goes for moving data between disk partitions. Only when you move data within the same partition, the permissions are kept."  Recently I was asked to assist in troubleshooting some NTFS related issues. This forced me to have another good look at this theory. To my surprise I found out that this theory does not completely stand anymore. Apparently some things have changed since the release of Windows Vista / Windows 2008. Since the release of these Operating Systems, a move within the same disk partition results in the data inheriting the permissions of the location it is being copied into. A major change in the NTFS filesystem you would think!  Not quite! The above only counts when the move operation is being performed by using Windows Explorer. A move by using the 'move' command from within a cmd prompt for example, retains the NTFS permissions, just like before in Windows XP and older systems. Conclusion: The Windows Explorer is responsible for changing the ACL's of the moved data. This is a remarkable change, but if you follow this theory, the resulting ACL after a move operation is still predictable.  We could say that since Windows Vista and Windows 2008, a new rule set applies: "If you copy data, the copied data will inherit the permissions of the location it is being copied to. Same goes for moving data between disk partitions and within disk partitions. Only when you move data within the same partition by using something else than the Windows Explorer, the permissions are kept." The above behavior should be unchanged in Windows 7 / Windows 2008 R2, compared to Windows Vista / 2008. But somehow the NTFS permissions are not so predictable in Windows 7 and Windows 2008 R2. Moving data within the same disk partition the one time results in the permissions being kept and the next time results in inherited permissions from the destination location. I will try to demonstrate this in a few examples: Example 1 (Incorrect behavior): Consider two folders, 'Folder A' and 'Folder B' with the following permissions configured.                    Now we create the test file 'test file 1.txt' in 'Folder A' and afterwards move this file to 'Folder B' using Windows Explorer.                       According to the new theory, the file should inherit the permissions of 'Folder B' and therefore 'Group B' should appear in the ACL of 'test file 1.txt'. In the screenshot below the resulting permissions are displayed. The permissions from the originating location are kept, while the permissions of 'Folder B' should be inherited.                   Example 2 (Correct behavior): Again, consider the same two folders. This time we make a small modification to the ACL of 'Folder A'. We add 'Group C' to the ACL and again we create a file in 'Folder A' which we name 'test file 2.txt'.                    Next, we move 'test file 2.txt' to 'Folder B'.                       Again, we check the permissions of 'test file 2.txt' at the target location. We can now see that the permissions are inherited. This is what should be happening, and can be considered 'correct behavior' for Windows Vista / 2008 / 7 / 2008 R2. It remains uncertain why this behavior is so inconsistent. At this time, this is under investigation with Microsoft Support. The investigation has been going for the last two weeks and it is beginning to look like there is no rational reason for this, other than a bug in the Windows Explorer in Windows 7 and 2008 R2. As soon as there is any certainty on this, I will note it here in this blog.                   The examples above are harmless tests, by using my own laptop. If you would create the same set of folders and groups, and configure exactly the same permissions, you will see exactly the same behavior. Be sure to use Windows 7 or Windows 2008 R2.   Initially the problem arose at a customer site where move operations on data on the fileserver by users would result in unpredictable results. This resulted in the wrong set of people having àccess permissions on data that they should not have permissions to. Off course this is something we want to prevent at all costs.   I have also done several tests with move operations by using the move command in a cmd prompt. This way the behavior is always consistent. The inconsistent behavior is only exposed when using the Windows Explorer to initiate the move operation, and only when using Windows 7 or Windows 2008 R2 systems. It is evident that this behavior changes when the ACL of a folder has been changed, for example by adding an extra entry. The reason for this remains uncertain though. To be continued…. A dutch version of this post can be found at: http://blogs.platani.nl/?p=612

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• javadoc and overloaded methods

  - by skrebbel

  Hi all, I'm developing an API with many identically named methods that just differ by signature, which I guess is fairly common. They all do the same thing, except that they initialize various values by defaults if the user does not want to specify. As a digestible example, consider public interface Forest { public Tree addTree(); public Tree addTree(int amountOfLeaves); public Tree addTree(int amountOfLeaves, Fruit fruitType); public Tree addTree(int amountOfLeaves, int height); public Tree addTree(int amountOfLeaves, Fruit fruitType, int height); } The essential action performed by all of these methods is the same; a tree is planted in the forest. Many important things users of my API need to know about adding trees hold for all these methods. Ideally, I would like to write one Javadoc block that is used by all methods: /** * Plants a new tree in the forest. Please note that it may take * up to 30 years for the tree to be fully grown. * * @param amountOfLeaves desired amount of leaves. Actual amount of * leaves at maturity may differ by up to 10%. * @param fruitType the desired type of fruit to be grown. No warranties * are given with respect to flavour. * @param height desired hight in centimeters. Actual hight may differ by * up to 15%. */ In my imagination, a tool could magically choose which of the @params apply to each of the methods, and thus generate good docs for all methods at once. With Javadoc, if I understand it correctly, all I can do is essentially copy&paste the same javadoc block five times, with only a slightly differing parameter list for each method. This sounds cumbersome to me, and is also difficult to maintain. Is there any way around that? Some extension to javadoc that has this kind of support? Or is there a good reason why this is not supported that I missed?

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• Dynamically loading sub-trees into YUI Treeview

  - by user319399

  When you create a YUI TreeView instance, you can pass in an object that represents an entire tree, and it will automatically build up the TextNodes for you. I'd like to send in a partial tree, such that the tree only goes, say, 2 levels deep, and anything deeper than that will invoke dynamic loading. I've got that much working. Now for the interesting part. In the dynamic loading callback I give to my tree instance, I want to again be able to just give YUI a big object representing more of the tree. I want to do something like this: // data is a array of objects organized into a tree, with some nodes requiring dynamic loading when they are navigated to tree = new YAHOO.widget.TreeView("treeDiv1", data); tree.setDynamicLoad(loadDataForNode); function loadDataForNode(node, onCompleteCallback) { if(node.children.length==0) { var subTree = { "label":"Cars", isLeaf:false, children:[ { "label":"Chevy", isLeaf:true }, { "label":"Ford", isLeaf:true }, ] }; // doesn't work, even though it has the required "label" field var tempNode = new YAHOO.widget.TextNode(subTree, node, true); } onCompleteCallback(); } Is this possible? Or do I have to iterate over all the nodes in my subtree and construct individual TextNodes for each one? Thanks much...

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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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