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• How can I start any application with Guest permissions by default?

  - by Tom Wijsman

  Here are my two questions: How can I start any application with Guest permissions by default? How can I set certain applications not to launch with Guest permissions? For the first bullet, any non-Microsoft signed application I launch should run as the Guest account. For the second bullet, I'm imagining adding menu entries like this would be a nice approach: Set to run as Guest (= default selected entry) Set to run as User Set to run as Admin But how do I do this?

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• UNIX tool to dump a selection of HTML?

  - by jldugger

  I'm looking to monitor changes on websites and my current approach is being defeated by a rotating top banner. Is there a UNIX tool that takes a selection parameter (id attribute or XPath), reads HTML from stdin and prints to stdout the subtree based on the selection? For example, given an html document I want to filter out everything but the subtree of the element with id="content". Basically, I'm looking for the simplest HTML/XML equivalent to grep.

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• Building a video wall with devices

  - by machunter

  I am entertaining building a video wall made out of many android devices. But I have to say I have no clue about how to go about it? The fact that these are android devices is not very important I am curious about the general approach to doing video walls with many separated devices. At best the desktop of one machine should be displayed on all the devices. If not I would be also interested in just showing just a video on that wall.

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• Is Flash a secure content delivery technology for password protected digital content?

  - by Merkel Fastia

  We are working on a project that would be a competitor to Yudu for online publishing and what we are debating is whether to use Flash for content security protection as Yudu does. See for example "The Testicle Cookbok" for which a limited (3-frame) preview is available before a password is requested by the Flash application running in the browser. Do you see any problems with this approach or could you recommend an alternative technology for password proected digital content?

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• UI Acclerometer refrence

  - by sid

  I am new to iPhone development. I want to make a simple iPhone application which when launched computes the distance travelled by the user,calories burnt,postion of the user,movement.Can anybody provide me the details or approach to follow to develop this application.

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• Cooling Server Rack with Water? Sensible? Reuse energy for small installation?

  - by TomTom

  First - this is not a shopping question, this is not so much about concrete prices but about general feasibility. Makes no sense to get looking fo ra manufacturer it the approach is bad. I am moving my company to new Offices in September, and among them we will expand and consolidate our number crunch cluster. It is so far in a data center. I have a nice room in the basement prepared now. I think about cooling. We will likely run up a power usage of around 10kw by end of the year. That is a LOT of stuff, and cooling will be expensive. I am located in south Poland, close to the German border. This is an area where water is available for relatively cheap price - "wasting water" is not a concern here. My situation is thus a lot different for example than in Spain ;) Physics tells me that to heat 1 liter of water by 1 degree I use 1 Calorie (1KCal), and a kwh power is (and we can assume 100% efficiency - water heaters are pretty efficient) 750 Calories. That means that 1 KWH is 750 liter by 1 degree. 10kw and a 20 degree heat would mean that per hour I need 375 liters. That is 6.25 liters per minute and not WHAT much ;) We talk 270 cubic meters here. Even in summer, the significant underground pipes really cool down the water a LOT more ;) Question: This such an approach feasible? Anyone done that? We talk of a 10kw installation for now. Is it feasible to reuse that heat? The alternative is a decent cooling system that WILL use around 2.5kwh for running. Dropping the water would basically (a) get me a quite cold input compared to the outside air even in summer (I.e. a lower temperature medium to drop the heat in) and (b) replace the need to actually have the outside cooling (which may b problematic - if the air is 22 degree, that is a LOT to fight off, but OTOH the water will be quite cold). I also would possibly save the investment for the outside part of the cooling circuit. Now, second question - is there a feasible way to heat a house with that? ;) After all, brutally speaking, it is a LOT of energy in that water ;) If it is a bad idea, I stop here - if it is not, I start looking for suppliers. Maybe my math is wrong?

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• Granting Read-Only access to an existing Oracle Schema

  - by Andrew

  Hi, we've got an Oracle 11g Schema that our application uses to select, insert and update, but we've had a request from one of our customers to provide read-only access to the same base tables and views owned by the application. Other than synonym'ing all of the application owned tables into a new account (or making the synonyms public), how would I go about doing this? Any help or pointers to the approach or Oracle feature I should be looking at would be most appreciated, thank you!

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• How i can apply database changes and application changes to my live ap.net mvc3 web application

  - by john G

  i have published my asp.net mvc3 that uses entity framewrok with database-first approach to the live server using IIS 7. then i modify the database any update some views, models and controllers in the vesion at my development environment also i have fixed some defects. So which tools I should use to update my live version to be similar to the version at the development environment, while not loosing any of the data already stored in the database, and is there any tutorials that can help me in implementing similar tasks. BR

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• Architectural advice - web camera remote access

  - by Alan Hollis

  I'm looking for architectural advice. I have a client who I've built a website for which essentially allows users to view their web cameras remotely. The current flow of data is as follows: User opens page to view web camera image. Javascript script polls url on server ( appended with unique timestamp ) every 1000ms Ftp connection is enabled for the cameras ftp user. Web camera opens ftp connection to server. Web camera begins taking photos. Web camera sends photo to ftp server. On image url request: Server reads latest image on hard drive uploaded via ftp for camera. Server deleted any older images from the server. This is working okay at the moment for a small amount of users/cameras ( about 10 users and around the same amount of cameras), but we're starting to worrying about the scalability of this approach. My original plan was instead of having the files read from the server, the web server would open up an ftp connection to the web server and read the latest images directly from there meaning we should have been able to scale horizontally fairly easily. But ftp connection establishment times were too slow ( mainly due to the fact that PHP out of the ox is unable to persist ftp connections ) and so we abandoned this approach and went straight for reading from the hard drive. The firmware provider for the cameras state they're able to build a http client which instead of using ftp to upload the image could post the image to a web server. This seems plausible enough to me, but I'm looking for some architectural advice. My current thought is a simple Nginx/PHP/Redis stack. Web camera issues post requests of latest image to Nginx/PHP and the latest image for that camera is stored in Redis. The clients can then pull the latest image from Redis which should be extremely quick as the images will always be stored in memory. The data flow would then become: User opens page to view web camera image. Javascript script polls url on server ( appended with unique timestamp ) every 1000ms Camera is sent an http request to start posting images to a provided url Web camera begins taking photos. Web camera sends post requests to server as fast as it can On image url request: Server reads latest image from redis Server tells redis to delete later image My questions are: Are there any greater overheads of transferring images via HTTP instead of FTP? Is there a simple way to calculate how many potential cameras we could have streaming at once? Is there any way to prevent potentially DOS'ing our own servers due to web camera requests? Is Redis a good solution to this problem? Should I abandon PHP/Ngix combination and go for something else? Is this proposed solution actually any good? Will adding HTTPs to the mix cause posting the image to become too slow? Thanks in advance Alan

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• Restoring MySQL dump - ERROR 2006 (HY000)

  - by matcheek

  I am just trying to restore a mysql dump. Below are the command and error message. Can anybody give me some clues how to approach this? 10:54:16 Restoring C:\Users\matcheek\Documents\dumps\Dump20120405-1.sql Running: mysql.exe "--defaults-extra-file="d:\temp\tmpbvhy4i.cnf" " --host=127.0.0.1 --user=root --port=3306 --default-character-set=utf8 --comments < "C:\\Users\\matcheek\\Documents\\dumps\\Dump20120405-1.sql" ERROR 2006 (HY000) at line 271: MySQL server has gone away

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• How can I create my own Android Home Screen Launcher

  - by Sam_k

  I want to know how I can create my own customised home screen for Android. I have used Viewpager to add and remove screens from the home screen, creating 5 screens as default, and then adding and removing further pages in with ViewPager. I have tried both Viewpager and PagerAdapter, as per this link. Is this the best approach so that in future I can add widgets and shortcuts with viewpager and make a launcher icon?

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• What do you use RightScale for?

  - by npt

  I'm currently evaluating whether to use RightScale to manage a production environment in EC2. I intend to use Puppet for configuration management either way (the declarative approach seems far better than running scripts), am running a somewhat nonstandard stack (e.g. MongoDB), and am uncertain about how much value RightScale would add relative to Puppet + Amazon's auto-scaling + another hosted monitoring system. Those who use RightScale, what features do you find important? Is its auto-scaling support (including keeping single instances running) more powerful than Amazon's?

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• Mount network drive

  - by user971155

  I'm using linux(ubuntu), there's a linux(fedora) server, that I can log in with ssh, is there any possibility //server/dir /mnt/my_mount_dir cifs username=loginpassword=11111,uid=1000,iocharset=utf8,codepage=unicode,unicode 0 0 As far as I'm concerned, this construction uses SMB as primary tool. Is there any possibility to use NFS or any another approach, because in case of SMB it tends to have permission, symlink collisions. PS It would be great if you also provide some links. Thanks.

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• Ajax, Lizard Brain Web Design, JSF, Struts, JavaScript, Mobile Web, Flash, jQuery, GWT, Harmony at I

  - by Kim Won

  Great Indian Developer Summit 2010 – India's Biggest Polyglot Conference and Workshops for IT Software Professionals Bangalore, April 9, 2010: The GIDS.Web Conference and Workshops has announced the complete program of over 30 sessions on how browser and rich web technologies such as AJAX, DHTML, Mashups, Web 2.0, Enterprise 2.0 technologies, and Rich UI technologies are making money and gaining market-share for some of the leading businesses in the world. The GIDS.Web track at Great Indian Developer Summit takes place 21 and 23 April 2010, at the Indian Institute of Science in Bangalore. As one of the longest running independent developer conferences in India, GIDS.Web at the Great Indian Developer Summit 2010 is uniquely positioned to provide a blend of practical, pragmatic and immediately applicable knowledge and a glimpse of the future of technology. During 21 and 23 April 2010, GIDS.Web offers a multi-track conference, workshops, expo show floor, and networking opportunities. The first keynote at GIDS.Web is led by the leading Java EE and Ajax developer, speaker, and author Marty Hall. The best of India's Java and RIA programmers have learnt the subject from Marty's seminal books Core Servlets and JavaServer Pages (first and second editions), More Servlets and JavaServer Pages, and Core Web Programming (first and second editions) from Prentice Hall and Sun Microsystems Press. Marty's keynote address is a comparison of approaches to building rich Internet applications with Ajax. Marty says Ajax development is difficult, and there are several fundamentally different strategies to building Ajaxified Web applications. The keynote address will survey the three most important of these approaches: using an Ajax-enabled JavaScript library such as jQuery, Prototype, Scriptaculous, Dojo, or Ext/JS; using a Web framework such as JSF 2.0 or Struts 2 that has integrated Ajax support; using the Google Web Toolkit (GWT) to build "pure Java" Ajax applications. The talk will compare and contrast these three approaches, discussing the types of applications that fit best for each option. Over the course of the summit Marty will conduct several more sessions on "Choosing an Ajax/JavaScript Toolkit: A Comparison of the Most Popular JavaScript Libraries", "Pure Java Ajax: An Overview of GWT 2.0", "Integrated Ajax Support in JSF 2.0" and "Ajax Support in the Prototype JavaScript Library". The second keynote by the head of Adobe's Flash initiative in India, Ramesh Srinivasaraghavan, explores the state of art in web application development and identify trends that could transform the way we create and use web applications. The talk explains how the Adobe Flash Platform has fuelled this revolution with an integrated set of technologies for delivering the most compelling applications, content and video to the widest possible audience. The Director of Forum Nokia will explain how cloud computing coupled with mobile applications enable consumers to have access to powerful services and improved user experiences never before thought possible. IEEE's 2010 President-Elect Sorel Reisman's afternoon address steps to improve the IT profession in India. Featured talks at GID.Web also include: Web 2.0 Checklist - Deconstructing Modern Websites, Scott Davis Choosing an Ajax/JavaScript Toolkit: Comparison of Popular JavaScript Libraries, Marty Hall Lizard Brain Web Design, Scott Davis Effective Design Processes and Resources for Mobile Web Development, Arabella David NoSQL: The Shift to a Non-relational World, Nosh Petigara Open Source Web Debugging Tools, Matthew McCullough Building Line of Business Applications with Silverlight 4.0, Stephen Forte Hadoop - Divide and Conquer, Matthew McCullough Adobe Flash Catalyst for Agile Interaction Design, Harish Sivaramakrishnan Using jQuery and AJAX to Build Front-ends for ASP.NET and ASP.NET MVC, Pandurang Nayak First Steps to IT Heaven Through the Cloud. Part II: .WEB, Simone Brunozzi Building Rich Internet Applications with SL RIA Web Services, Pandurang Nayak Enriching Cloud Applications with Adobe Flash Platform, Ramesh Srinivasaraghavan Payments for the Web.future, Khurram Khan and Praveen Alavilli Longevity of Scalable Systems, Nishad Kamat Transform yourself into a Mobile App Developer Using Web Run Time, Balagopal K S Developing Multi Screen Applications on Adobe Flash Platform, Hemanth Sharma Why Harmony and For Whom?, Himanshu Goyal IIS Hosting Solution for ASP.net and PHP Web Sites, Nahas Mohammed Building Pluggable Web applications using Django, Lakshman Prasad Workshop: The 180-min AJAX and JSON Spike Class, Scott Davis Workshop: Essence of Functional Programming, Venkat Subramaniam Workshop: Agile Development, Tools, and Teams and Scrum Certification, Stephen Forte Workshop: PHP + Adobe Flex = Killer RIA, Shyamprasad P Workshop: Cloud Computing Boot Camp on the Google App Engine, Matthew McCullough Workshop: Building Data Centric Applications using Adobe Flex and Java, Prashant Singh Workshop: Building Your First Amazon App, Simone Brunozzi Workshop: Windows Azure Deep Dive, Ramaprasanna Chellamuthu Workshop: Monetizing your Apps with PayPal X Payments Platform, Khurram Khan, Praveen Alavilli Workshop: User Expereince Evaluation Model Walkthrough, Sanna Häiväläinen Sponsors of Great Indian Developer Summit 2010 include: Platinum sponsors Microsoft, Oracle Forum Nokia and Adobe; Gold sponsors Intel and SAP; Silver sponsors Quest Software, PayPal, Telerik and AMT. About Great Indian Developer Summit Great Indian Developer Summit is the gold standard for India's software developer ecosystem for gaining exposure to and evaluating new projects, tools, services, platforms, languages, software and standards. Packed with premium knowledge, action plans and advise from been-there-done-it veterans, creators, and visionaries, the 2010 edition of Great Indian Developer Summit features focused sessions, case studies, workshops and power panels that will transform you into a force to reckon with. Featuring 3 co-located conferences: GIDS.NET, GIDS.Web, GIDS.Java and an exclusive day of in-depth tutorials - GIDS.Workshops, from 20 April to 24 April at the IISc campus in Bangalore. At GIDS you'll participate in hundreds of sessions encompassing the full range of Microsoft computing, Java, Agile, RIA, Rich Web, open source/standards, languages, frameworks and platforms, practical tutorials that deep dive into technical skill and best practices, inspirational keynote presentations, an Expo Hall featuring dozens of the latest projects and products activities, engaging networking events, and the interact with the best and brightest of speakers from around the world. For further information on GIDS 2010, please visit the summit on the web http://www.developersummit.com/ A Saltmarch Media Press Release E: [email protected] Ph: +91 80 4005 1000

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• Removing Left Recursion in ANTLR

  - by prosseek

  As is explained in http://stackoverflow.com/questions/2652060/removing-left-recursion , there are two ways to remove the left recursion. Modify the original grammar to remove the left recursion using some procedure Write the grammar originally not to have the left recursion What people normally use for removing (not having) the left recursion with ANTLR? I've used flex/bison for parser, but I need to use ANTLR. The only thing I'm concerned about using ANTLR (or LL parser in genearal) is left recursion removal. In practical sense, how serious of removing left recursion in ANTLR? Is this a showstopper in using ANTLR? Or, nobody cares about it in ANTLR community? I like the idea of AST generation of ANTLR. In terms of getting AST quick and easy way, which method (out of the 2 removing left recursion methods) is preferable?

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• Loading Separate Pages With Animation in JQTouch

  - by Donovan Keith

  I'm trying to convert a database-driven multiple-choice-style study website (written in JSP) into an iPhone app using JQTouch. If I load all of the Q&A's into their own divs in the same file I can easily link and animate between them using links to hashtags, like: a class="button" href="#question22" Unfortunately this isn't practical. The logic of the website as it currently works requires calls to a number of dynamically generated pages; I can't include every question in its own div in the same flat file. How would I go about dynamically (pre)loading the next question (a JSP page like AskQuestion.jsp?questionId=Kzhctand ) then serving that up within the app after the user presses a button? Thanks for any help you might offer. -Donovan

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• SAAS architecture and salesforce database architecture

  - by Farax

  Hello all, I am architecting a software project and I want to create a SAAS (Software As a service) one. I want to model my application along the lines of Salesforce. I really like there customization features but I am not sure how they really go about it. I read that they create an ID for every field that is required and then store the corresponding data too. Can anyone guide me as to how this is possible. For example, if I want to store an employee record. 2 fields (firstname, lastname) are already given and the user adds a third field(say DOB), how is data going to be stored? I would also appreciate if someone could give me some resources to practical examples of implementing a SAAS architecture. Thanks

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• Load ActiveX DLL in Internet Explorer with elevated privileges

  - by adum

  I have an ActiveX control that I'm loading with JavaScript in Internet Explorer. It needs to run as medium integrity under UAC in Vista and Win7. This is written in C/C++, compiled in Visual Studio. One way to elevate privileges is to create a broker process that can request a medium integrity level. However, for this project, this is not a practical solution. I really need the ActiveX control itself to run elevated. My question is: what's the easiest way to do this? Can I change the build options on the project to be an exe, and use the COM interprocess connect system to automatically handle the communications, or do I need to be more sophisticated? Do I need to do anything complicated like manually call CreateProcess and make some kind of broker, or can it just work as an ActiveX exe that elevates itself?

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• Would the MSFT Report Viewer (rdlc) Work with MVC

  - by Mike Thomas

  I am interested in learning MVC, and have experimented with a couple of the sample apps. As a project, I'd like to move part or all of my own office app to MVC. An important part of this app, and of ALL of my apps for customers, is the printing of invoices, purchase orders, inventory lists and so forth. In fact, one of their main criteria for judging what we do is the appearance of these documents and their incorporation into the app in a practical, intuitive way. It's impossible for me to get by without a report writer. The MSFT report viewer used to produce rdlc reports has been sufficient, and even comes up better than the competition in a couple of key areas. Does this control work with an ASP.NET MVC application?

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• Is That REST API Really RPC? Roy Fielding Seems to Think So.

  - by Rich Apodaca

  A large amount of what I thought I knew about REST is apparently wrong - and I'm not alone. This question has a long lead-in, but it seems to be necessary because the information is a bit scattered. The actual question comes at the end if you're already familiar with this topic. From the first paragraph of Roy Fielding's REST APIs must be hypertext-driven, it's pretty clear he believes his work is being widely misinterpreted: I am getting frustrated by the number of people calling any HTTP-based interface a REST API. Today’s example is the SocialSite REST API. That is RPC. It screams RPC. There is so much coupling on display that it should be given an X rating. Fielding goes on to list several attributes of a REST API. Some of them seem to go against both common practice and common advice on SO and other forums. For example: A REST API should be entered with no prior knowledge beyond the initial URI (bookmark) and set of standardized media types that are appropriate for the intended audience (i.e., expected to be understood by any client that might use the API). ... A REST API must not define fixed resource names or hierarchies (an obvious coupling of client and server). ... A REST API should spend almost all of its descriptive effort in defining the media type(s) used for representing resources and driving application state, or in defining extended relation names and/or hypertext-enabled mark-up for existing standard media types. ... The idea of "hypertext" plays a central role - much more so than URI structure or what HTTP verbs mean. "Hypertext" is defined in one of the comments: When I [Fielding] say hypertext, I mean the simultaneous presentation of information and controls such that the information becomes the affordance through which the user (or automaton) obtains choices and selects actions. Hypermedia is just an expansion on what text means to include temporal anchors within a media stream; most researchers have dropped the distinction. Hypertext does not need to be HTML on a browser. Machines can follow links when they understand the data format and relationship types. I'm guessing at this point, but the first two points above seem to suggest that API documentation for a Foo resource that looks like the following leads to tight coupling between client and server and has no place in a RESTful system. GET /foos/{id} # read a Foo POST /foos/{id} # create a Foo PUT /foos/{id} # update a Foo Instead, an agent should be forced to discover the URIs for all Foos by, for example, issuing a GET request against /foos. (Those URIs may turn out to follow the pattern above, but that's beside the point.) The response uses a media type that is capable of conveying how to access each item and what can be done with it, giving rise to the third point above. For this reason, API documentation should focus on explaining how to interpret the hypertext contained in the response. Furthermore, every time a URI to a Foo resource is requested, the response contains all of the information needed for an agent to discover how to proceed by, for example, accessing associated and parent resources through their URIs, or by taking action after the creation/deletion of a resource. The key to the entire system is that the response consists of hypertext contained in a media type that itself conveys to the agent options for proceeding. It's not unlike the way a browser works for humans. But this is just my best guess at this particular moment. Fielding posted a follow-up in which he responded to criticism that his discussion was too abstract, lacking in examples, and jargon-rich: Others will try to decipher what I have written in ways that are more direct or applicable to some practical concern of today. I probably won’t, because I am too busy grappling with the next topic, preparing for a conference, writing another standard, traveling to some distant place, or just doing the little things that let me feel I have I earned my paycheck. So, two simple questions for the REST experts out there with a practical mindset: how do you interpret what Fielding is saying and how do you put it into practice when documenting/implementing REST APIs? Edit: this question is an example of how hard it can be to learn something if you don't have a name for what you're talking about. The name in this case is "Hypermedia as the Engine of Application State" (HATEOAS).

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• Experience using Yii framework for actual PHP project

  - by desireco

  I've been using Code Igniter for my PHP projects, when I start them from the beginning. It is very nice framework, saves me a lot of work and let me have low level access if I need to do something special. Code Igniter is also faster then similar frameworks by order of magnitude. I came across Yii framework which claims to be even faster and easier and prettier and whatever. I never heard of it and I was wondering if someone used it in some real life project and have practical experience that he is willing to share.

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• When to use Shift operators << >> in C# ?

  - by Junior Mayhé

  I was studying shift operators in C#, trying to find out when to use them in my code. I found an answer but for Java, you could: a) Make faster integer multiplication and division operations: *4839534 * 4* can be done like this: 4839534 << 2 or 543894 / 2 can be done like this: 543894 1 Shift operations much more faster than multiplication for most of processors. b) Reassembling byte streams to int values c) For accelerating operations with graphics since Red, Green and Blue colors coded by separate bytes. d) Packing small numbers into one single long... For b, c and d I can't imagine here a real sample. Does anyone know if we can accomplish all these items in C#? Is there more practical use for shift operators in C#?

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• Rendering formatted text in a direct3d application

  - by Fire Lancer

  I need to render some formatted text (colours, different font sizes, underlines, bold, etc) however I'm not sure how to go about doing it. D3DXFont only allows text of a single font/size/weight/colour/etc to be rendered at once, and I cant see a practical way to "combine" multiple calls to ID3DXFont::DrawText to do such things... I looked around and there doesn't seem to be any existing libraries that do these things, but I have no idea how to implement such a text renderer, and I couldn't even find any documentation on how such a text render would work, only rendering simple fixed width, ASCII bitmap fonts which looking at it is probably an entirely different approach that is only suitable for rendering simple blocks of text where Unicode is not important. If there's no direct3d font renders capable of doing this, is there any other renderers (eg for use in rendering rich text in a normal window), and would rendering those to a texture in RAM, then uploading that to the video card to render onto the back buffer yield reasonable performance?

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• How to count each digit in a range of integers?

  - by Carlos Gutiérrez

  Imagine you sell those metallic digits used to number houses, locker doors, hotel rooms, etc. You need to find how many of each digit to ship when your customer needs to number doors/houses: 1 to 100 51 to 300 1 to 2,000 with zeros to the left The obvious solution is to do a loop from the first to the last number, convert the counter to a string with or without zeros to the left, extract each digit and use it as an index to increment an array of 10 integers. I wonder if there is a better way to solve this, without having to loop through the entire integers range. Solutions in any language or pseudocode are welcome. Edit: Answers review John at CashCommons and Wayne Conrad comment that my current approach is good and fast enough. Let me use a silly analogy: If you were given the task of counting the squares in a chess board in less than 1 minute, you could finish the task by counting the squares one by one, but a better solution is to count the sides and do a multiplication, because you later may be asked to count the tiles in a building. Alex Reisner points to a very interesting mathematical law that, unfortunately, doesn’t seem to be relevant to this problem. Andres suggests the same algorithm I’m using, but extracting digits with %10 operations instead of substrings. John at CashCommons and phord propose pre-calculating the digits required and storing them in a lookup table or, for raw speed, an array. This could be a good solution if we had an absolute, unmovable, set in stone, maximum integer value. I’ve never seen one of those. High-Performance Mark and strainer computed the needed digits for various ranges. The result for one millon seems to indicate there is a proportion, but the results for other number show different proportions. strainer found some formulas that may be used to count digit for number which are a power of ten. Robert Harvey had a very interesting experience posting the question at MathOverflow. One of the math guys wrote a solution using mathematical notation. Aaronaught developed and tested a solution using mathematics. After posting it he reviewed the formulas originated from Math Overflow and found a flaw in it (point to Stackoverflow :). noahlavine developed an algorithm and presented it in pseudocode. A new solution After reading all the answers, and doing some experiments, I found that for a range of integer from 1 to 10n-1: For digits 1 to 9, n*10(n-1) pieces are needed For digit 0, if not using leading zeros, n*10n-1 - ((10n-1) / 9) are needed For digit 0, if using leading zeros, n*10n-1 - n are needed The first formula was found by strainer (and probably by others), and I found the other two by trial and error (but they may be included in other answers). For example, if n = 6, range is 1 to 999,999: For digits 1 to 9 we need 6*105 = 600,000 of each one For digit 0, without leading zeros, we need 6*105 – (106-1)/9 = 600,000 - 111,111 = 488,889 For digit 0, with leading zeros, we need 6*105 – 6 = 599,994 These numbers can be checked using High-Performance Mark results. Using these formulas, I improved the original algorithm. It still loops from the first to the last number in the range of integers, but, if it finds a number which is a power of ten, it uses the formulas to add to the digits count the quantity for a full range of 1 to 9 or 1 to 99 or 1 to 999 etc. Here's the algorithm in pseudocode: integer First,Last //First and last number in the range integer Number //Current number in the loop integer Power //Power is the n in 10^n in the formulas integer Nines //Nines is the resut of 10^n - 1, 10^5 - 1 = 99999 integer Prefix //First digits in a number. For 14,200, prefix is 142 array 0..9 Digits //Will hold the count for all the digits FOR Number = First TO Last CALL TallyDigitsForOneNumber WITH Number,1 //Tally the count of each digit //in the number, increment by 1 //Start of optimization. Comments are for Number = 1,000 and Last = 8,000. Power = Zeros at the end of number //For 1,000, Power = 3 IF Power 0 //The number ends in 0 00 000 etc Nines = 10^Power-1 //Nines = 10^3 - 1 = 1000 - 1 = 999 IF Number+Nines <= Last //If 1,000+999 < 8,000, add a full set Digits[0-9] += Power*10^(Power-1) //Add 3*10^(3-1) = 300 to digits 0 to 9 Digits[0] -= -Power //Adjust digit 0 (leading zeros formula) Prefix = First digits of Number //For 1000, prefix is 1 CALL TallyDigitsForOneNumber WITH Prefix,Nines //Tally the count of each //digit in prefix, //increment by 999 Number += Nines //Increment the loop counter 999 cycles ENDIF ENDIF //End of optimization ENDFOR SUBROUTINE TallyDigitsForOneNumber PARAMS Number,Count REPEAT Digits [ Number % 10 ] += Count Number = Number / 10 UNTIL Number = 0 For example, for range 786 to 3,021, the counter will be incremented: By 1 from 786 to 790 (5 cycles) By 9 from 790 to 799 (1 cycle) By 1 from 799 to 800 By 99 from 800 to 899 By 1 from 899 to 900 By 99 from 900 to 999 By 1 from 999 to 1000 By 999 from 1000 to 1999 By 1 from 1999 to 2000 By 999 from 2000 to 2999 By 1 from 2999 to 3000 By 1 from 3000 to 3010 (10 cycles) By 9 from 3010 to 3019 (1 cycle) By 1 from 3019 to 3021 (2 cycles) Total: 28 cycles Without optimization: 2,235 cycles Note that this algorithm solves the problem without leading zeros. To use it with leading zeros, I used a hack: If range 700 to 1,000 with leading zeros is needed, use the algorithm for 10,700 to 11,000 and then substract 1,000 - 700 = 300 from the count of digit 1. Benchmark and Source code I tested the original approach, the same approach using %10 and the new solution for some large ranges, with these results: Original 104.78 seconds With %10 83.66 With Powers of Ten 0.07 A screenshot of the benchmark application: If you would like to see the full source code or run the benchmark, use these links: Complete Source code (in Clarion): http://sca.mx/ftp/countdigits.txt Compilable project and win32 exe: http://sca.mx/ftp/countdigits.zip Accepted answer noahlavine solution may be correct, but l just couldn’t follow the pseudo code, I think there are some details missing or not completely explained. Aaronaught solution seems to be correct, but the code is just too complex for my taste. I accepted strainer’s answer, because his line of thought guided me to develop this new solution.

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• C# best means to store data locally when offline

  - by mickartz

  I am in the midst of writing a small program (more to experiment with vs 2010 than anything else) Despite being an experiment it has some practical use for our local athletics club. My thought was to access the DB (currently online) to download the current members and store locally on a laptop (this is a MS sql table, used to power the club's website). take the laptop to the event (yes there ARE places that don't have internet coverage), add members to that days race (also a row from a sql table (though no changes would be made to this), record results (new records in 3rd table) Once home, showered and within internet access again, upload/edit the tables as per the race results/member changes etc. So I was thinking i'd do something like write xml files locally with the data, including a field to indicate changes etc? If anyone can point me in a direction i would appreciate it...hell if anyone could tell me if this has a name!!..I'd appreciate it TIA Michael Artz

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