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  • Convert color photos of documents to good black-and-white images?

    - by Norman Ramsey
    Since I don't have a copier or scanner, I'm using an 8 megapixel camera to copy documents. This works pretty well except they need a lot of processing afterward. I'd like to get from a photo to a bitmap, but using djpeg -grayscale -pnm photo.jpg | pgmtopbm -threshold -value XXX does not work so well, for two reasons: It's hard to guess what XXX should be, and XXX is different for different photos. Illumination varies, and sometimes a single threshold isn't what's right for the image. How can I do better? The ideal solution will be fully automatic command-line program that I can run on Linux. (I have already written a program to remove dark pixels from the edges of images.)

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  • How do you kill a process tree in linux?

    - by itsadok
    Sometimes, sending a SIGTERM to a process will cause it to send SIGTERM to all its child processes. However, sometimes this doesn't work. Is there a command or a utility that will allow me to kill a process and all its child processes at the same time? I usually resort to manually collecting all the pids into one kill command, but it feels stupid. This SO question asks how to do this with perl, but anything that gets the job done would be great.

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  • How to change the install path of my Linux Source tree?

    - by Sen
    I was trying to bring up my custom kernel. I did the following : make menuconfig && make modules && make modules_install && make install I would like to change the install PATH. How can i do that? I tried doing export INSTALL_PATH=<my custom path> But then it is only creating the vmlinux.bin(it is not creating the ramdisk image!!) But if i am not doing that, make install will automatically create the ramdisk image in the default /boot folder. How can i change that?? Thanks, Sen

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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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  • How can I automatically synchronize a directory tree on multiple machines?

    - by Blacklight Shining
    I have two Mac laptops and a Debian server, each with a directory that I would like to keep in sync between the three. The solution should meet the following criteria (in rough order of importance): It must not use any third-party service (e.g. Dropbox, SugarSync, Google whatever). This does not include installing additional software (as long as it's free). It must not require me to use specific directories or change my way of storing things. (Dropbox does this IIRC) It must work in all directions (changes made on /any/ machine should be pushed to the others) All data sent must be encrypted (I have ssh keypairs set up already) It must work even when not all machines are available (changes should be pushed to a machine when it comes back online) It must work even when the /directories/ on some machines are not available (they may be stored on disk images which will not always be mounted) This can be solved for Macs by using launchd to automatically launch and kill (or in some way change the behavior of) whatever daemon is used for syncing when the images are mounted and unmounted. It must be immediate (using an event-based system, not a periodic one like cron) It must be flexible (if more machines are added, I should be able to incorporate them easily) I also have some preferences that I would like to be fulfilled, but do not have to be: It should notify me somehow if there are conflicts or other errors. It should recognize symbolic and hard links and create corresponding ones. It should allow me to create a list of exceptions (subdirectories which will not be synced at all). It should not require me to set up port forwarding or otherwise reconfigure a network. This can be solved by using an ssh tunnel with reverse port forwarding. If you have a solution that meets some, but not all of the criteria, please contribute it in the comments as it might be useful in some way, and it might be possible to meet some of the criteria separately. What I tried, and why it didn't work: rsync and lsyncd do not support bidirectional synchronization csync2 is designed for server clusters and does not appear to work with machines with dynamic IPs DRBD (suggested by amotzg) involves installing a kernel module and does not appear to work on systems running OS X

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  • Ubuntu 14.04 stalling. Problem with LightDM. Plymouth (and logging out) switches over to a black screen w/ white cursor

    - by Kage
    if its a duplicate, sorry. Couldn't find anything that fits my issue, much less that was on 14.04. I changed a few things recently. Switched to the Numix theme (from PPA), installed lm-sensors and psensor (ran all the I/O probes), Ubuntu Tweak, Pinta, and well, Team Fortress 2 on Steam. :P The system will get to the Plymouth 'ubuntu' screen, load load, all dots filled, switches over to LightDM, but wait! No LightDM. :I Just a blank screen with that white cursor. Can't switch out to tty1-6 - not sure if the Ctrl-Alt-F1 is disabled in 14.04 or if its literally just locked down. If I change any files, I have access to the filesystem from my Windows 8 partition. That's it. :/ I'm pretty familiar with Linux, especially Ubuntu, but I think I'm still at the point I know just enough to break things and not always how to fix 'em. Any help would be greatly appreciated. Thanks! UPDATE I was just able to get into my desktop briefly. I booted Ubuntu. When the black screen froze, I hit Ctrl-Alt-Del. When it started switching off, I hit Ctrl-Alt-Backspace. It rebooted. I plugged the second monitor in I had been using before the issue ever came about. Plymouth displayed on both. LightDM came up, displayed on both (it used to show only the ubuntu logo on the unfocused monitor though). I logged in just fine. Even ran some pending software updates. I logged out of the desktop though, and LightDM refused to show again. xP

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  • Emails not arriving to client's inbox. Server not on black list.

    - by EBroker
    Hi, I'm sending emails to my clients who are hosted on GoDaddy for both their website and email. For some reason, my system's emails are no longer reaching their inbox. My email server sends them alerts when an action is completed. These alerts are posted in my system and my email server is sending these out, but there are no bounceback emails. There have been no issues in the past year, but in the past two weeks the problem started cropping up. My clients were forced to switched to a web-based email provider like Gmail, Hotmail, Yahoo to receive their alerts. This is a temporary solution that works in the interim. I contacted GoDaddy and they are indicating that I am not being blocked. I also have a GoDaddy account and can confirm that my alerts aren't arriving in the inbox regardless of whatever safe sender items I employ in the webmail interface. I even switched all the system's outbound emails to Plain Text, no luck. Can anyone provide some insight and point me in the right direction? Thank you in advance.

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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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  • 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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  • 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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  • 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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  • 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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  • Editting CSS in iframe that sets Select tag's text color to black?

    - by Corey Ogburn
    This is a very specific question for a Google Chrome extension. http://www.meebo.com/mobile/ This page is where you're kicked to when you go to Meebo.com on an iPhone or Droid phone. But if you notice, the Status box where you can set yourself away or what you want your status to be has white text on a white background. In order to get a website to appear in a Google Chrome extension's popup window (the one that drops down when you click the icon next to the address bar) that isn't an included html file in the extension, I need to use an iFrame. I know that there's security measures about Cross-Site stuff like javascript and I'm not surprised I'm having trouble accessing the CSS. But there's a class, status, and it's color is white and I need to change that to black. I've tested it with Chrome's Inspect Element window and if I change that, I'll be fine. I've tried changing the manifest.json file to inject a CSS file using Content-Scripts, but nothing... I'm new to Chrome Extensions but I have experience doing web development.

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  • Converting image to Black & White image on iPhone SDK issues.

    - by KfirS
    Hello, I've used a familiar code to convert image to Black & White which I've founded on several forums. The code is: CGColorSpaceRef colorSapce = CGColorSpaceCreateDeviceGray(); CGContextRef context = CGBitmapContextCreate(nil, originalImage.size.width, originalImage.size.height, 8, originalImage.size.width, colorSapce, kCGImageAlphaNone); CGContextSetInterpolationQuality(context, kCGInterpolationHigh); CGContextSetShouldAntialias(context, NO); CGContextDrawImage(context, CGRectMake(0, 0, originalImage.size.width, originalImage.size.height), [originalImage CGImage]); CGImageRef bwImage = CGBitmapContextCreateImage(context); CGContextRelease(context); CGColorSpaceRelease(colorSapce); UIImage *resultImage = [UIImage imageWithCGImage:bwImage]; // This is result B/W image. CGImageRelease(bwImage); return resultImage; When I'm using this code with on Horizontal image it's work fine, but when I'm trying a to use this code on Vertical image, the result is disproportionate image and rotate 90 degree left. Can anyone know what could be the problem? Thanks, Kfir.

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  • How to have screen revert to BLACK between pages?

    - by user340667
    0 Hi - I tried out the Background Image Scaling script and with Cybr's update it works like magic. It SCALES the image perfectly. No distortion. BUT, my image isn't "computer friendly". I.e.: Not 1024 X 768 or even close to that. (Heck, my monitor has a wide screen, so it isn't 1024 X 768 either! Is anybody's anymore?) Anyhow, this creates a problem inasmuch as, unless I size the window from the bottom up it ends up with a white "stripe" beneath it. What I would REALLY like for it to do is have that white to be BLACK. My "usual" BG color/text etc. code is like: ""body bgcolor="#000000" text="#fcba1e" link="#0000ff" vlink="#800080" alink="#ff0000"" (Site won't let me add the arrows here.) I've tried inserting this in various places with no success. Any ideas for a workaround would surely be appreciated ! Thanks ! Bill

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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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  • 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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  • How do I transition from WUBI to a native installation?

    - by Sammy Black
    I have Ubuntu 10.04 Lucid installed through wubi on my laptop (it came with Windows 7 preinstalled). This was my first foray into Linux, and I'm here to stay. I have no use for Windows, and yet I must manually choose not to boot into it! Should I shrink the Windows partition to something negligible and grow the Linux one using something like gparted or fdisk, and just be content that everything runs? In that case, I need to understand the filesystems. Which is which? Here's the output of $ df -h: Filesystem Size Used Avail Use% Mounted on /dev/loop0 17G 11G 4.5G 71% / none 1.8G 300K 1.8G 1% /dev none 1.8G 376K 1.8G 1% /dev/shm none 1.8G 316K 1.8G 1% /var/run none 1.8G 0 1.8G 0% /var/lock none 1.8G 0 1.8G 0% /lib/init/rw /dev/sda3 290G 50G 240G 18% /host I would prefer to start over with a clean install of 10.10 Maverick, but I fear what I may lose. Certainly, I will backup my home directory tree (gzip?), but what about various pieces of software that I've acquired from the repositories? Can I keep a record of them? By the way, I asked a similar question over on Ubuntu forums.

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