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  • Grams to Pounds: A Domino Chain Reaction [Video]

    - by Jason Fitzpatrick
    Most of us have seen a domino knock down or two in our day, but this demonstration video shows how a series of increasingly larger dominoes allow a tiny domino to knock over a 100 pound domino. A domino can knock over another domino about 50% larger than itself. A chain of dominos of increasing size makes a kind of mechanical chain reaction that starts with a tiny push and knocks down an impressively large domino. The only question we have after watching the video is: where can we find 29 appropriately sized dominoes? [via Neatorama] HTG Explains: What Is Windows RT and What Does It Mean To Me? HTG Explains: How Windows 8′s Secure Boot Feature Works & What It Means for Linux Hack Your Kindle for Easy Font Customization

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  • Safe project development - free repositories

    - by friko
    Some time ago we started a private hobby project. We made a project on javaforge.com, created an svn repository and started developing our app. Right now we are really far with our project, but somehow we never worried if our project is really safe on such free development tool like javaforge ? I mean, what if our project would earn some money and the source code become valuable ? Could it be stolen or could somebody take it over ? We want to be sure that we are not wasting our time and want to be really sure about our project safety. Is it possible to safely develop a project in such free repository ? We would like also to start using redmine, so if you know any safe place for moving our project, please take this under consideration. Thanks a lot.

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  • Is Windows 7 written in Xaml? [closed]

    - by Jordan
    Is Windows 7 written using Xaml? Edit Wow, so much hate for such a little question. I'm not an idiot. I know what XAML is. I use it every day. I was just curious whether some of the visual features were laid out with XAML, or if XAML was incorporated in some way to the product. I'm sorry if it is a programming sin not to know what Windows 7 was written in. I mean, I know Windows XP et al used C++/C, I've used Win32 quite a lot (and MFC and .NET).

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  • Do first impressions really count?

    - by Matt
    So, i am currently writing something up for a college class. Problem is everything is hypothetical. I need some proof. I believe a first impression on a website is imperative so that people actually use it and in my case, buy your product or services as well. Basically I'm wondering has there been any studies that shows how a better web design will increase revenue for any kind of services? I don't just mean selling products like a T-shirt, but labor services as well. If someone wanted their computer fixed and searched for companies that can do so, will a first impression on the website help them make their decision to use your company? Are there any studies like this? White papers maybe? Thanks!

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  • Amazon Web Services Free Trial: query about get and put requests

    - by abel
    Amazon recently introduced a free tier for its cloud offering. I signed up for AWS and while signing up for the free tier of S3, i found this As part of AWS Free Usage Tier, you can get started with Amazon S3 for free. Upon sign-up, new AWS customers receive 5 GB of Amazon S3 storage, 20,000 Get Requests, 2,000 Put Requests, 15GB of bandwidth in and 15GB of bandwidth out each month for one year. source:aws.amazon.com , emphasis mine. 20,000 GET requests & 2000 puts mean , 20,000 page views(max) and 2000 file uploads per month. Isn't that lower than what App Engine offers 43,200,000 requests per day.Am I missing some thing, please help.

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  • Breadcrumb for multiple categories

    - by Damodar Bashyal
    I post in multiple categories, so is it better to have: Consulting Services Implementation Service A Consulting Services Optimization Service A Consulting Services Upgrade Service A or, Consulting Services Implementation, Optimization, Upgrade Service A I was doing second way, the problem is google doesn't show 3rd set of crumbs. ie it only displays: Consulting Services on search result. But having multiple breadcrumbs on the page doesn't look good. any suugestions? Update For @PatomaS 's question I mean 3 lines of breadcrumbs, see above i have posted same article (Service A) in 3 categories (Implementation, Optimization, Upgrade). So you can reach same article through 3 categories. So whats the best breadcrumb to display on article 'Service A'?

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  • Cheerp -- C++ for web: advance or regression?

    - by Henrique Barcelos
    Recently I've run into Cheerp, a C++ to Javascript compiler, which uses a modified version of clang to generate Javascript code from C++ sources. That makes me wonder: why in the seven kingdoms would someone do this in their right mind? I mean: why would you take a language that is not designed for web at all, that is far more convoluted and bureaucratic, write your code and then compile it into Javascript itself? Can anybody see any advantages in doing so? We surely can discard performance as a reason, because in the end it generates pure Javascript code. Is there anyone here that have real experience with this? P.S.: I'm not sure if this is an on topic question, but this is the most general forum about programming that I could find in the StackExchange network. Edit Although this seems like a subjective question, it is not. I am asking for reasons that this tool could be useful. I got interested at first, but started wondering why would someone use it.

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  • Software design methods for Java or any other programming language

    - by IkerB
    I'm junior programmer and I would like to know how professionals write their code or which steps they follow when they are creating new software. I mean, which steps they follow, which programming methodology, software architecture design application software, etc. I would like to find a tutorial where they explain from the beginning which steps I have to follow from The Idea I have in my mind to the final version of the application in any language. Or perhaps how is your programming steps or rules that you used to follow. Because everytime I want to create the an application I spend few time on the design and a lot of time coding (I know, that's not good).

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  • How to evaluate SEO/prominence improvement [on hold]

    - by Rober
    I will work on a website SEO and before starting with it I would like to "take a snapshot" of the present status so that I will be able to compare it with the new situation in a few months and evaluate my work and the real improvement. I don't mean whether the website is well implemented or not, but how well it is seen by Google and others. What prominence it has. I am taking some variables from Google Analytics (average day visits...), from Google Webmaster Tools (Search traffic and average position...) and some other indicators, like automatic SEO audit figures (website estimated worth, real pagerank...). What would you look at before starting SEO improvement?

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  • How can I install the Unity Photo Lens

    - by Chuqui
    I can't install the Photo Lens. After running these commands: sudo add-apt-repository ppa:scopes-packagers/ppa sudo apt-get update && sudo apt-get install unity-lens-photo unity-scope-shotwell unity-scope-flickr I get this: Package unity-lens-photo is not available, but is referred to by another package. This may mean that the package is missing, has been obsoleted, or is only available from another source E: Package 'unity-lens-photo' has no installation candidate Is there a fix for that? Thank you very much.

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  • How are you using the Managed Extensibility Framework?

    - by dboarman
    I have been working with MEF for about 2 weeks. I started thinking about what MEF is for, researching to find out how to use MEF, and finally implementing a Host with 3 modules. The contracts are proving to be easy to grasp and the modules are easily managed. Although MEF has a very practical use, I am wondering to what extent? I mean, is everyone going to be rewriting existing applications for extensibility? Yes, that sounds, and is insanely impractical. Rhetorically speaking: how is MEF affecting the current trends in programming? have you begun looking for opportunities to use MEF? have you begun planning a major re-write of an existing app that may benefit from extensibility? That said, my questions are: how do I know when I should plan a new project with extensibility? how will I know if an existing project needs to be re-written for extensibility? Is anyone using MEF?

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  • partitioning in ubuntu with gparted cant resize

    - by user288830
    I opened gparted and as i can see i have 3 partitions(or i think so) first one sda1 (236 mb) its ext2 type file and its booting point, second one is sda2(rest of the hdd 1.36 tb) extended ntfs type file and i have third one that is within the sda2 called sda5 it takes the same space as sda 2 and its file type is crypt luks, so when i try to resize the sda2 i cant resize it not for even 1 mb, i dont know if that crypt luks file is causing the problem, so i dont know what to do, by the way i can format the crypt luks(sda5) file that in inside sda 2 but i dont know if i should.Can anyone help me please? here are the pictures when i open gparted when i try to resize sda 2 i think i did use encryption i mean while it is booting i type password and its says sda5/scrypt set up succefully or something like that and then it goes to my login screen where i type username and pass that is it

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  • Cannot execute binary file

    - by user291727
    I am new to Ubuntu and I'm trying to install Popcorn Time. I downloaded 32 bit version and tried to install it but that's where the problem started showing. I duble clicked the executable file and well, nothing happened. It's a official download from their web-site but it doesn't work. Maybe I'm doing something wrong.....Anyway, I found out that you can insatll it from a script, but people keep talking in ubuntu terms and I don't understand it, so I have a few questions: 1.How to make a script? (witch I'm suppose to run in terminal using bash comand), 2.Is it normal that i cannot run the installer, and if that is an installer or just files for the program. 3.If it is an installer, how do I make it work? 4.What does " Cannot execute binary file" mean? Thank you in advance, hope I'm not asking too many questions(please understand that I'm new to ubuntu) and sorry about my English. xD

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  • HTML 5, Fluid Pages and Google Mobile Index

    - by Bob
    I am currently migrating my site to HTML5, at the same time designing pages so that they are "fluid" and are equally presentable for a mobile or a large screen. I took the fluid approach so as not to have to develop a separate application for mobile devices and I'm pleasantly surprised with the results that look equally as good on an iPhone as they do on a large screen. Then I went into the Google Webmaster Tools facility and became aware of the Google Mobile Index. I'm confused now as HTML5 doesn't seem to be supported by Google Mobile Indexing. Does this mean that when I go live with my new "pride and joy" HTML5 site on a mobile it won't appear on any Google searches as it's not in the Google Mobile Index?

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  • How can I get a list of installed programs and corresponding size of each in Ubuntu?

    - by Philip Baker
    I would like to have a list of the installed software on my machine, with the disk space consumed by them. A previous answer here says "you can do this via GUI in Synaptic". This doesn't mean anything to me. I don't know what GUI is, and when I click on Synaptic, I do not get anything like the display shown in the answer, i.e. with "Settings ? Preferences" and "Columns and Fonts". In Windows, you just select 'Programs and Applications' in the Control Panel, and the list comes up immediately, with sizes. Is there something similar and simple with Ubuntu? Could the size of each program be included on the list of installed software? This would be the most obvious place to put it.

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  • Should data structures be integrated into the language (as in Python) or be provided in the standard library (as in Java)?

    - by Anto
    In Python, and most likely many other programming languages, common data structures can be found as an integrated part of the core language with their own dedicated syntax. If we put LISP's integrated list syntax aside, I can't think of any other languages that I know which provides some kind of data structure above the array as an integrated part of their syntax, though all of them (but C, I guess) seem to provide them in the standard library. From a language design perspective, what are your opinions on having a specific syntax for data structures in the core language? Is it a good idea, and does the purpose of the language (etc.) change how good this could be of a choice? Edit: I'm sorry for (apparently) causing some confusion about which data structures I mean. I talk about the basic and commonly used ones, but still not the most basic ones. This excludes trees (too complex, uncommon), stacks (too seldom used), arrays (too simple) but includes e.g. sets, lists and hashmaps.

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  • Linux repository contains latest tools for synaptic

    - by William.Ebe
    I'm using backTrack5R3. And I 've installed Synaptic as well as ubuntu Software center. Synaptic is very easy to use and gives wide range of details for the packages that I'm going to download. But the problem is it lack of lot of new files and information. Like vlc or adobe reader. The latest stable version of vlc is 2.0. but synaptic only installs, 1.1. And it don't find adobe. I would like to get new versions of them. What is the best way/source to update new files? EDIT: I mean after performing update & upgrade synaptic still contains vlc 1.0.6 which is outdated. I'm looking for a way to get new/best source.

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  • what does composition example vs aggregation

    - by meWantToLearn
    Composition and aggregation both are confusion to me. Does my code sample below indicate composition or aggregation? class A { public static function getData($id) { //something } public static function checkUrl($url) { // something } class B { public function executePatch() { $data = A::getData(12); } public function readUrl() { $url = A::checkUrl('http/erere.com'); } public function storeData() { //something not related to class A at all } } } Is class B a composition of class A or is it aggregation of class A? Does composition purely mean that if class A gets deleted class B does not works at all and aggregation if class A gets deleted methods in class B that do not use class A will work?

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  • Would you use (a dialect of) LISP for a real-world application? Where and why?

    - by Anto
    LISP (and dialects such as Scheme, Common LISP and Clojure) haven't gained much industry support even though they are quite decent programming languages. (At the moment though it seems like they are gaining some traction). Now, this is not directly related to the question, which is would you use a LISP dialect for a production program? What kind of program and why? Usages of the kind of being integrated into some other code (e.g. C) are included as well, but note that it is what you mean in your answer. Broad concepts are preferred but specific applications are okey as well.

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  • How to disallow indexing but allow crawling?

    - by John Doe
    In the front page of my website, I have some previews to articles (with a small introduction to them) that link to the full articles. I want to disallow the front page to prevent duplicate content. But if I do this (in robots.txt), would it still be crawled? I mean, the full articles would be still reached by the crawler even though I disallowed the only page that links to them? I don't want the webcrawler not to access the page and enter the links in them, but I just don't want it to save the information (that will be repeated in the full articles).

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  • Naming conventions used for variables and functions in C

    - by Zel
    While coding a large project in C I came upon a problem. If I keep on writing more code then there will be a time when it will be difficult for me to organize the code. I mean that the naming for functions and variables for different parts of the program may seem to be mixed up. So I was thinking whether there are useful naming conventions that I can use for C variables and functions? Most languages suggest a naming convention. But for C the only thing I have read so far is the names should be descriptive for code readability. EDIT: Examples of some examples of suggested naming conventions: Python's PEP 8 Java Tutorial I read some more naming conventions for java somewhere but couldn't remember where.

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  • how to label a cuboid using open gl?

    - by usha
    hi this is how my 3dcuboid looks ,i have attached complete code , i want to label this cuboid using different name across sides how is it possible using opengl in android...plz help me out public class MyGLRenderer implements Renderer { Context context; Cuboid rect; private float mCubeRotation; // private static float angleCube = 0; // Rotational angle in degree for cube (NEW) // private static float speedCube = -1.5f; // Rotational speed for cube (NEW) public MyGLRenderer(Context context) { rect = new Cuboid(); this.context = context; } public void onDrawFrame(GL10 gl) { // TODO Auto-generated method stub gl.glClear(GL10.GL_COLOR_BUFFER_BIT | GL10.GL_DEPTH_BUFFER_BIT); gl.glLoadIdentity(); // Reset the model-view matrix gl.glTranslatef(0.2f, 0.0f, -8.0f); // Translate right and into the screen gl.glScalef(0.8f, 0.8f, 0.8f); // Scale down (NEW) gl.glRotatef(mCubeRotation, 1.0f, 1.0f, 1.0f); // gl.glRotatef(angleCube, 1.0f, 1.0f, 1.0f); // rotate about the axis (1,1,1) (NEW) rect.draw(gl); mCubeRotation -= 0.15f; //angleCube += speedCube; } public void onSurfaceChanged(GL10 gl, int width, int height) { // TODO Auto-generated method stub if (height == 0) height = 1; // To prevent divide by zero float aspect = (float)width / height; // Set the viewport (display area) to cover the entire window gl.glViewport(0, 0, width, height); // Setup perspective projection, with aspect ratio matches viewport gl.glMatrixMode(GL10.GL_PROJECTION); // Select projection matrix gl.glLoadIdentity(); // Reset projection matrix // Use perspective projection GLU.gluPerspective(gl, 45, aspect, 0.1f, 100.f); gl.glMatrixMode(GL10.GL_MODELVIEW); // Select model-view matrix gl.glLoadIdentity(); // Reset } public void onSurfaceCreated(GL10 gl, EGLConfig config) { // TODO Auto-generated method stub gl.glClearColor(0.0f, 0.0f, 0.0f, 1.0f); // Set color's clear-value to black gl.glClearDepthf(1.0f); // Set depth's clear-value to farthest gl.glEnable(GL10.GL_DEPTH_TEST); // Enables depth-buffer for hidden surface removal gl.glDepthFunc(GL10.GL_LEQUAL); // The type of depth testing to do gl.glHint(GL10.GL_PERSPECTIVE_CORRECTION_HINT, GL10.GL_NICEST); // nice perspective view gl.glShadeModel(GL10.GL_SMOOTH); // Enable smooth shading of color gl.glDisable(GL10.GL_DITHER); // Disable dithering for better performance }} public class Cuboid{ private FloatBuffer mVertexBuffer; private FloatBuffer mColorBuffer; private ByteBuffer mIndexBuffer; private float vertices[] = { //width,height,depth -2.5f, -1.0f, -1.0f, 1.0f, -1.0f, -1.0f, 1.0f, 1.0f, -1.0f, -2.5f, 1.0f, -1.0f, -2.5f, -1.0f, 1.0f, 1.0f, -1.0f, 1.0f, 1.0f, 1.0f, 1.0f, -2.5f, 1.0f, 1.0f }; private float colors[] = { // R,G,B,A COLOR 0.0f, 1.0f, 0.0f, 1.0f, 0.0f, 1.0f, 0.0f, 1.0f, 1.0f, 0.5f, 0.0f, 1.0f, 1.0f, 0.5f, 0.0f, 1.0f, 1.0f, 0.0f, 0.0f, 1.0f, 1.0f, 0.0f, 0.0f, 1.0f, 0.0f, 0.0f, 1.0f, 1.0f, 1.0f, 0.0f, 1.0f, 1.0f }; private byte indices[] = { // VERTEX 0,1,2,3,4,5,6,7 REPRESENTATION FOR FACES 0, 4, 5, 0, 5, 1, 1, 5, 6, 1, 6, 2, 2, 6, 7, 2, 7, 3, 3, 7, 4, 3, 4, 0, 4, 7, 6, 4, 6, 5, 3, 0, 1, 3, 1, 2 }; public Cuboid() { ByteBuffer byteBuf = ByteBuffer.allocateDirect(vertices.length * 4); byteBuf.order(ByteOrder.nativeOrder()); mVertexBuffer = byteBuf.asFloatBuffer(); mVertexBuffer.put(vertices); mVertexBuffer.position(0); byteBuf = ByteBuffer.allocateDirect(colors.length * 4); byteBuf.order(ByteOrder.nativeOrder()); mColorBuffer = byteBuf.asFloatBuffer(); mColorBuffer.put(colors); mColorBuffer.position(0); mIndexBuffer = ByteBuffer.allocateDirect(indices.length); mIndexBuffer.put(indices); mIndexBuffer.position(0); } public void draw(GL10 gl) { gl.glFrontFace(GL10.GL_CW); gl.glVertexPointer(3, GL10.GL_FLOAT, 0, mVertexBuffer); gl.glColorPointer(4, GL10.GL_FLOAT, 0, mColorBuffer); gl.glEnableClientState(GL10.GL_VERTEX_ARRAY); gl.glEnableClientState(GL10.GL_COLOR_ARRAY); gl.glDrawElements(GL10.GL_TRIANGLES, 36, GL10.GL_UNSIGNED_BYTE, mIndexBuffer); gl.glDisableClientState(GL10.GL_VERTEX_ARRAY); gl.glDisableClientState(GL10.GL_COLOR_ARRAY); } } public class Draw3drect extends Activity { private GLSurfaceView glView; // Use GLSurfaceView // Call back when the activity is started, to initialize the view @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); glView = new GLSurfaceView(this); // Allocate a GLSurfaceView glView.setRenderer(new MyGLRenderer(this)); // Use a custom renderer this.setContentView(glView); // This activity sets to GLSurfaceView } // Call back when the activity is going into the background @Override protected void onPause() { super.onPause(); glView.onPause(); } // Call back after onPause() @Override protected void onResume() { super.onResume(); glView.onResume(); } }

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  • 3D terrain map with Hexagon Grids (XNA)

    - by Rob
    I'm working on a hobby project (I'm a web/backend developer by day) and I want to create a 3D Tile (terrain) engine. I'm using XNA, but I can use MonoGame, OpenGL, or straight DirectX, so the answer does not have to be XNA specific. I'm more looking for some high level advice on how to approach this problem. I know about creating height maps and such, there are thousands of references out there on the net for that, this is a bit more specific. I'm more concerned with is the approach to get a 3D hexagon tile grid out of my terrain (since the terrain, and all 3d objects, are basically triangles). The first approach I thought about is to basically draw the triangles on the screen in the following order (blue numbers) to give me the triangles for terrain (black triangles) and then make hexes out of the triangles (red hex). http://screencast.com/t/ebrH2g5V This approach seems complicated to me since i'm basically having to draw 4 different types of triangles. The next approach I thought of was to use the existing triangles like I did for a square grid and get my hexes from 6 triangles as follows http://screencast.com/t/w9b7qKzVJtb8 This seems like the easier approach to me since there are only 2 types of triangles (i would have to play with the heights and widths to get a "perfect" hexagon, but the idea is the same. So I'm looking for: 1) Any suggestions on which approach I should take, and why. 2) How would I translate mouse position to a hexagon grid position (especially when moving the camera around), for example in the second image if the mouse pointer were the green circle, how would I determine to highlight that hexagon and then translating that into grid coordinates (assuming it is 0,0)? 3) Any references, articles, books, etc - to get me going in the right direction. Note: I've done hex grid's and mouse-grid coordinate conversion before in 2d. looking for some pointers on how to do the same in 3d. The result I would like to achieve is something similar to the following: http :// www. youtube .com / watch?v=Ri92YkyC3fw (sorry about the youtube link, but it will only let me post 2 links in this post... same rep problem i mention below...) Thanks for any help! P.S. Sorry for not posting the images inline, I apparently don't have enough rep on this stack exchange site.

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  • How to force a clock update using ntp?

    - by ysap
    I am running Ubuntu on an ARM based embedded system that lacks a battery backed RTC. The wake-up time is somewhere during 1970. Thus, I use the NTP service to update the time to the current time. I added the following line to /etc/rc.local file: sudo ntpdate -s time.nist.gov However, after startup, it still takes a couple of minutes until the time is updated, during which period I cannot work effectively with tar and make. How can I force a clock update at any given time? UPDATE 1: The following (thanks to Eric and Stephan) works fine from command line, but fails to update the clock when put in /etc/rc.local: $ date ; sudo service ntp stop ; sudo ntpdate -s time.nist.gov ; sudo service ntp start ; date Thu Jan 1 00:00:58 UTC 1970 * Stopping NTP server ntpd [ OK ] * Starting NTP server [ OK ] Thu Feb 14 18:52:21 UTC 2013 What am I doing wrong? UPDATE 2: I tried following the few suggestions that came in response to the 1st update, but nothing seems to actually do the job as required. Here's what I tried: Replace the server to us.pool.ntp.org Use explicit paths to the programs Remove the ntp service altogether and leave just sudo ntpdate ... in rc.local Remove the sudo from the above command in rc.local Using the above, the machine still starts at 1970. However, when doing this from command line once logged in (via ssh), the clock gets updated as soon as I invoke ntpdate. Last thing I did was to remove that from rc.local and place a call to ntpdate in my .bashrc file. This does update the clock as expected, and I get the true current time once the command prompt is available. However, this means that if the machine is turned on and no user is logged in, then the time never gets updates. I can, of course, reinstall the ntp service so at least the clock is updated within a few minutes from startup, but then we're back at square 1. So, is there a reason why placing the ntpdate command in rc.local does not perform the required task, while doing so in .bashrc works fine?

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  • C# Open Source software that is useful for learning Design Patterns

    - by Fathom Savvy
    In college I took a class in Expert Systems. The language the book taught (CLIPS) was esoteric - Expert Systems: Principles and Programming, Fourth Edition. I remember having a tough time with it. So, after almost failing the class, I needed to create the most awesome Expert System for my final presentation. I chose to create an expert system that would calculate risk analysis for a person's retirement portfolio. In short, the system would provide the services normally performed by one's financial adviser. In other words, based on personality, age, state of the macro economy, and other factors, should one's portfolio be conservative, moderate, or aggressive? In the appendix of the book (or on the CD-ROM), there was this in-depth example program for something unrelated to my presentation. Over my break, I read and re-read every line of that program until I understood it to the letter. Even though it was unrelated, I learned more than I ever could by reading all of the chapters. My presentation turned out to be pretty damn good and I received praises from my professor and classmates. So, the moral of the story is..., by understanding other people's code, you can gain greater insight into a language/paradigm than by reading canonical examples. Still, to this day, I am having trouble with everyday design patterns such as the Factory Pattern. I would like to know if anyone could recommend open source software that would help me understand the Gang of Four design patterns, at the very least. I have read the books, but I'm having trouble writing code for the concepts in the real world. Perhaps, by studying code used in today's real world applications, it might just "click". I realize a piece of software may only implement one kind of design pattern. But, if the pattern is an implementation you think is good for learning, and you know what pattern to look for within the source, I'm hoping you can tell me about it. For example, the System.Linq.Expressions namespace has a good example of the Visitor Pattern. The client calls Expression.Accept(new ExpressionVisitor()), which calls ExpressionVisitor (VisitExtension), which calls back to Expression (VisitChildren), which then calls Expression (Accept) again - wooah, kinda convoluted. The point to note here is that VisitChildren is a virtual method. Both Expression and those classes derived from Expression can implement the VisitChildren method any way they want. This means that one type of Expression can run code that is completely different from another type of derived Expression, even though the ExpressionVisitor class is the same in the Accept method. (As a side note Expression.Accept is also virtual). In the end, the code provides a real world example that you won't get in any book because it's kinda confusing. To summarize, If you know of any open source software that uses a design pattern implementation you were impressed by, please list it here. I'm sure it will help many others besides just me. public class VisitorPatternTest { public void Main() { Expression normalExpr = new Expression(); normalExpr.Accept(new ExpressionVisitor()); Expression binExpr = new BinaryExpression(); binExpr.Accept(new ExpressionVisitor()); } } public class Expression { protected internal virtual Expression Accept(ExpressionVisitor visitor) { return visitor.VisitExtension(this); } protected internal virtual Expression VisitChildren(ExpressionVisitor visitor) { if (!this.CanReduce) { throw Error.MustBeReducible(); } return visitor.Visit(this.ReduceAndCheck()); } public virtual Expression Visit(Expression node) { if (node != null) { return node.Accept(this); } return null; } public Expression ReduceAndCheck() { if (!this.CanReduce) { throw Error.MustBeReducible(); } Expression expression = this.Reduce(); if ((expression == null) || (expression == this)) { throw Error.MustReduceToDifferent(); } if (!TypeUtils.AreReferenceAssignable(this.Type, expression.Type)) { throw Error.ReducedNotCompatible(); } return expression; } } public class BinaryExpression : Expression { protected internal override Expression Accept(ExpressionVisitor visitor) { return visitor.VisitBinary(this); } protected internal override Expression VisitChildren(ExpressionVisitor visitor) { return CreateDummyExpression(); } protected internal Expression CreateDummyExpression() { Expression dummy = new Expression(); return dummy; } } public class ExpressionVisitor { public virtual Expression Visit(Expression node) { if (node != null) { return node.Accept(this); } return null; } protected internal virtual Expression VisitExtension(Expression node) { return node.VisitChildren(this); } protected internal virtual Expression VisitBinary(BinaryExpression node) { return ValidateBinary(node, node.Update(this.Visit(node.Left), this.VisitAndConvert<LambdaExpression>(node.Conversion, "VisitBinary"), this.Visit(node.Right))); } }

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