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  • What do I need to know to design a language and write a interpreter for it?

    - by alFReD NSH
    I know this question has been asked and even there are thousands of books and articles about it. But the problem is that there are too many, and I don't know are they good enough, I have to design a language and write a interpreter for it. The base language is javascript (using nodejs) but it's ok if the compiler was written in another language that I can use from node. I had done a research about compiler compilers in JS, there is jison (Bison implementaion in JS), waxeye, peg.js. I decided to give jison a try, due to the popularity and its being used by coffee script, so it should be able to cover my language too. The grammar definition syntax is similar to bison. But when I tried read the bison manual it seemed very hard to understand for me. And I think it's because I don't know a lot of things about what I'm doing. Like I don't what is formal language theory. I am experienced in Javascript (I'm more talented in JS than most average programmers). And also know basic C and C++ (not much experience but can write a working code for basic things). I haven't had any formal education, so I may not be familiar with some software engineering and computer science principles. Though everyday I try to grasp a lot of articles and improve. So I'm asking if you know any good book or article that can help me. Please also write why the resource you're suggesting is good. --update-- The language I'm trying to create, is not really complicated. All it has is expressions (with or without units), comparisons and logical operators. There are no functions, loops, ... The goal is to create a language that non-programmers can easily learn. And to write customized validations and calculations.

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  • Is having functionality in DB a road block to scalability?

    - by Estefany Velez
    I may not be able to give the right title to the question. But here it is, We are developing financial portal for wealth management. We are expecting over 10000 clients to use the application. The portal calculates various performance analytics based on the the technical analysis of the stock market. We developed lot of the functionality through Stored procedures, user defined functions, triggers etc. through Database. We thought we can gain huge performance boost doing stuff directly in database than through C# code. And we actually did get a huge performance boost. When I tried to brag about the achievement to our CTO, he counter questioned my decision of having functionality implemented in database rather than code. According to him such applications suffer scalability problems. In his words "These days things are kept in memory/cache. Clustered data is hard to manage over time. Facebook, Google have nothing in database. It is the era of thin servers and thick clients. DB is used only to store plain data and functionality should be completely decoupled from the database." Can you guys please give me some suggestions as to whether what he says is right. How to go about architect such an application?

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  • Confused about javascript module pattern implementation

    - by Damon
    I have a class written on a project I'm working on that I've been told is using the module pattern, but it's doing things a little differently than the examples I've seen. It basically takes this form: (function ($, document, window, undefined) { var module = { foo : bar, aMethod : function (arg) { className.bMethod(arg); }, bMethod : function (arg) { console.log('spoons'); } }; window.ajaxTable = ajaxTable; })(jQuery, document, window); I get what's going on here. But I'm not sure how this relates to most of the definitions I've seen of the module (or revealing?) module pattern. like this one from briancray var module = (function () { // private variables and functions var foo = 'bar'; // constructor var module = function () { }; // prototype module.prototype = { constructor: module, something: function () { } }; // return module return module; })(); var my_module = new module(); Is the first example basically like the second except everything is in the constructor? I'm just wrapping my head around patterns and the little things at the beginnings and endings always make me not sure what I should be doing.

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  • Is this project Structure Valid?

    - by rafuru
    I have a dilemma: In the university we learn to create modular software (on java), but this modularity is explained using a single project with packages (a package for business, another one for DAOS and another one for the model, oh and a last package for frontend). But in my work we use the next structure: I will try to explain: First we create a java library project where the model (entities classes) are created in a package. Next we create an EJB named DAOS and using the netbeans wizard we store the DAOS interfaces in the library project in another package , these interfaces are implemented in the DAOS bean. So the next part is the business logic, we create a business EJB for each group of functions , again using the wizard we store the interface in the java library project in another package then is implemented on the business bean. The final part (for the backend) is a bean that I have suggested: a Facade bean who will gather every method of the business beans in a single bean and this has an interface too that is created in our library project and implemented in the bean. So the next part is call the facade module on the web project. But I don't know how valid or viable is this, maybe I'm doing everything wrong and I don't even know! so I want to ask your opinion about this.

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  • Misconceptions about purely functional languages?

    - by Giorgio
    I often encounter the following statements / arguments: Pure functional programming languages do not allow side effects (and are therefore of little use in practice because any useful program does have side effects, e.g. when it interacts with the external world). Pure functional programming languages do not allow to write a program that maintains state (which makes programming very awkward because in many application you do need state). I am not an expert in functional languages but here is what I have understood about these topics until now. Regarding point 1, you can interact with the environment in purely functional languages but you have to explicitly mark the code (functions) that introduces them (e.g. in Haskell by means of monadic types). Also, AFAIK computing by side effects (destructively updating data) should also be possible (using monadic types?) but is not the preferred way of working. Regarding point 2, AFAIK you can represent state by threading values through several computation steps (in Haskell, again, using monadic types) but I have no practical experience doing this and my understanding is rather vague. So, are the two statements above correct in any sense or are they just misconceptions about purely functional languages? If they are misconceptions, how did they come about? Could you write a (possibly small) code snippet illustrating the Haskell idiomatic way to (1) implement side effects and (2) implement a computation with state?

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  • Go/Obj-C style interfaces with ability to extend compiled objects after initial release

    - by Skrylar
    I have a conceptual model for an object system which involves combining Go/Obj-C interfaces/protocols with being able to add virtual methods from any unit, not just the one which defines a class. The idea of this is to allow Ruby-ish open classes so you can take a minimalist approach to library development, and attach on small pieces of functionality as is actually needed by the whole program. Implementation of this involves a table of methods marked virtual in an RTTI table, which system functions are allowed to add to during module initialization. Upon typecasting an object to an interface, a Go-style lookup is done to create a vtable for that particular mapping and pass it off so you can have comparable performance to C/C++. In this case, methods may be added /afterwards/ which were not previously known and these new methods allow newer interfaces to be satisfied; while I like this idea because it seems like it would be very flexible (disregarding the potential for spaghetti code, which can happen with just about any model you use regardless). By wrapping the system calls for binding methods up in a set of clean C-compatible calls, one would also be able to integrate code with shared libraries and retain a decent amount of performance (Go does not do shared linking, and Objective-C does a dynamic lookup on each call.) Is there a valid use-case for this model that would make it worth the extra background plumbing? As much as this Dylan-style extensibility would be nice to have access to, I can't quite bring myself to a use case that would justify the overhead other than "it could make some kinds of code more extensible in future scenarios."

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  • Dynamic libraries are not allowed on iOS but what about this?

    - by tapirath
    I'm currently using LuaJIT and its FFI interface to call C functions from LUA scripts. What FFI does is to look at dynamic libraries' exported symbols and let the developer use it directly form LUA. Kind of like Python ctypes. Obviously using dynamic libraries is not permitted in iOS for security reasons. So in order to come up with a solution I found the following snippet. /* (c) 2012 +++ Filip Stoklas, aka FipS, http://www.4FipS.com +++ THIS CODE IS FREE - LICENSED UNDER THE MIT LICENSE ARTICLE URL: http://forums.4fips.com/viewtopic.php?f=3&t=589 */ extern "C" { #include <lua.h> #include <lualib.h> #include <lauxlib.h> } // extern "C" #include <cassert> // Please note that despite the fact that we build this code as a regular // executable (exe), we still use __declspec(dllexport) to export // symbols. Without doing that FFI wouldn't be able to locate them! extern "C" __declspec(dllexport) void __cdecl hello_from_lua(const char *msg) { printf("A message from LUA: %s\n", msg); } const char *lua_code = "local ffi = require('ffi') \n" "ffi.cdef[[ \n" "const char * hello_from_lua(const char *); \n" // matches the C prototype "]] \n" "ffi.C.hello_from_lua('Hello from LUA!') \n" // do actual C call ; int main() { lua_State *lua = luaL_newstate(); assert(lua); luaL_openlibs(lua); const int status = luaL_dostring(lua, lua_code); if(status) printf("Couldn't execute LUA code: %s\n", lua_tostring(lua, -1)); lua_close(lua); return 0; } // output: // A message from LUA: Hello from LUA! Basically, instead of using a dynamic library, the symbols are exported directly inside the executable file. The question is: is this permitted by Apple? Thanks.

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  • CodePlex Daily Summary for Saturday, March 24, 2012

    CodePlex Daily Summary for Saturday, March 24, 2012Popular Releasesmenu4web: menu4web 0.0.3: menu4web 0.0.3Craig's Utility Library: Craig's Utility Library 3.1: This update adds about 60 new extension methods, a couple of new classes, and a number of fixes including: Additions Added DateSpan class Added GenericDelimited class Random additions Added static thread friendly version of Random.Next called ThreadSafeNext. AOP Manager additions Added Destroy function to AOPManager (clears out all data so system can be recreated. Really only useful for testing...) ORM additions Added PagedCommand and PageCount functions to ObjectBaseClass (same as M...SQL Monitor - managing sql server performance: SQLMon 4.2 alpha 14: 1. improved accuracy of logic fault checking in analysisMapWindow 6 Desktop GIS: MapWindow 6.1.1: MapWindow 6 Desktop GIS is an open source desktop GIS for Microsoft Windows that is built upon the DotSpatial Library. This release requires .Net 4 (Client Profile). Are you a software developer?Instead of downloading MapWindow for development purposes, get started with with the DotSpatial templateDotSpatial: DotSpatial 1.1: This is a Minor Release. See the changes in the issue tracker. Minimal -- includes DotSpatial core and essential extensions Extended -- includes debugging symbols and additional extensions Just want to run the software? End user (non-programmer) version available branded as MapWindow Want to add your own feature? Develop a plugin, using the template and contribute to the extension feed (you can also write extensions that you distribute in other ways). Components are available as NuGet pa...Indiefreaks Game Framework: 0.9.2.0: Feature: Added SunBurn engine v2.0.18.7 support (doesn't support versions below). Feature: Added GammaCorrection Post processor to allow developers or even players to tweak the Gamma of the game depending on their screen (courtesy of bamyazi) Feature: Added Windows, Xbox 360 & WP7 enabled StorageManager (based on Nick Gravelyn's EasyStorage) to read/write files for player or game data. Feature: Added VirtualGamePad feature for WP7 allowing developers to define Touch areas on screen and mapped...Code for Rapid C# Windows Development eBook + LINQPad and Data Tools: LLBLGen LINQPad Data Context Driver Version 2.1: Sixth release of a LLBLGen Pro Typed Data Context Driver for LINQPad. For LLBLGen Pro versions 3.1 and 3.5(coming). New features:When you switch the query language to SQL, LINQPad updates the Schema Explorer to show SQL column names rather than CLR property names Connection dialog unloads assemblies when it has closed down so they are no longer locked - this allows them to be rebuilt while LINQPad is still open Connection dialog includes a button to quickly add assemblies needed for the...People's Note: People's Note 0.40: Version 0.40 adds an option to compact the database from the profile screen. Compacting a database can make it smaller and faster by removing empty spaces left over by editing, moving, and deleting notes. To install: copy the appropriate CAB file onto your WM device and run it.Microsoft All-In-One Code Framework - a centralized code sample library: C++, .NET Coding Guideline: Microsoft All-In-One Code Framework Coding Guideline This document describes the coding style guideline for native C++ and .NET (C# and VB.NET) programming used by the Microsoft All-In-One Code Framework project team.WebDAV for WHS: Version 1.0.67: - Added: Check whether the Remote Web Access is turned on or not; - Added: Check for Add-In updates;Image 3D Viewer: Image 3D Viewer: WPF .Net 3.5 .Net 4 .Net 4.5Phalanger - The PHP Language Compiler for the .NET Framework: 3.0 (March 2012) for .NET 4.0: March release of Phalanger 3.0 significantly enhances performance, adds new features and fixes many issues. See following for the list of main improvements: New features: Phalanger Tools installable for Visual Studio 2011 Beta "filter" extension with several most used filters implemented DomDocument HTML parser, loadHTML() method mail() PHP compatible function PHP 5.4 T_CALLABLE token PHP 5.4 "callable" type hint PCRE: UTF32 characters in range support configuration supports <c...Nearforums - ASP.NET MVC forum engine: Nearforums v8.0: Version 8.0 of Nearforums, the ASP.NET MVC Forum Engine, containing new features: Internationalization Custom authentication provider Access control list for forums and threads Webdeploy package checksum: abc62990189cf0d488ef915d4a55e4b14169bc01 Visit Roadmap for more details.BIDS Helper: BIDS Helper 1.6: This beta release is the first to support SQL Server 2012 (in addition to SQL Server 2005, 2008, and 2008 R2). Since it is marked as a beta release, we are looking for bug reports in the next few months as you use BIDS Helper on real projects. In addition to getting all existing BIDS Helper functionality working appropriately in SQL Server 2012 (SSDT), the following features are new... Analysis Services Tabular Smart Diff Tabular Actions Editor Tabular HideMemberIf Tabular Pre-Build ...Json.NET: Json.NET 4.5 Release 1: New feature - Windows 8 Metro build New feature - JsonTextReader automatically reads ISO strings as dates New feature - Added DateFormatHandling to control whether dates are written in the MS format or ISO format, with ISO as the default New feature - Added DateTimeZoneHandling to control reading and writing DateTime time zone details New feature - Added async serialize/deserialize methods to JsonConvert New feature - Added Path to JsonReader/JsonWriter/ErrorContext and exceptions w...SCCM Client Actions Tool: SCCM Client Actions Tool v1.11: SCCM Client Actions Tool v1.11 is the latest version. It comes with following changes since last version: Fixed a bug when ping and cmd.exe kept running in endless loop after action progress was finished. Fixed update checking from Codeplex RSS feed. The tool is downloadable as a ZIP file that contains four files: ClientActionsTool.hta – The tool itself. Cmdkey.exe – command line tool for managing cached credentials. This is needed for alternate credentials feature when running the HTA...WebSocket4Net: WebSocket4Net 0.5: Changes in this release fixed the wss's default port bug improved JsonWebSocket supported set client access policy protocol for silverlight fixed a handshake issue in Silverlight fixed a bug that "Host" field in handshake hadn't contained port if the port is not default supported passing in Origin parameter for handshaking supported reacting pings from server side fixed a bug in data sending fixed the bug sending a closing handshake with no message which would cause an excepti...SuperWebSocket, a .NET WebSocket Server: SuperWebSocket 0.5: Changes included in this release: supported closing handshake queue checking improved JSON subprotocol supported sending ping from server to client fixed a bug about sending a closing handshake with no message refactored the code to improve protocol compatibility fixed a bug about sub protocol configuration loading in Mono improved BasicSubProtocol added JsonWebSocketSessionSurvey™ - web survey & form engine: Survey™ 2.0: The new stable Survey™ Project 2.0.0.1 version contains many new features like: Technical changes: - Use of Jquery, ASTreeview, Tabs, Tooltips and new menuprovider Features & Bugfixes: Survey list and search function Folder structure for surveys New Menustructure Library list New Library fields User list and search functions Layout options for a survey with CSS, page header and footer New IP filter security feature Enhanced Token Management New Question fields as ID, Alias...Speed up Printer migration using PrintBrm and it's configuration files: BRMC.EXE: Run the tool from the extracted directory of the printbrm backup. You can use the following command to extract a backup file to a directory - PRINTBRM.EXE -R -D C:\TEMP\EXPAND -F C:\TEMP\PRINTERBACKUP.PRINTEREXPORTNew ProjectsAsp.NET Url Router: 1.Url rewritting. 2.Provider regex matcher 3.Support custom url validate handler.BC-Web: ch projectCape: Dynamically generates Capistrano recipes for Rake tasks.cstgamebgs: Project for wp7GCalculator: GCalculator for performing basic arithmetic operations. Windows Sidebar Gadget invacc: Invacc- for inventory and Account Onlineirgsh-node: Worker nodes of BlankOn Package Factory - http://irgsh.blankonlinux.or.id/irgsh-repo: Repository manager node of BlankOn Package Factory - http://irgsh.blankonlinux.or.id/irgsh-web: Web interface and task manager of BlankOn Package Factory - http://irgsh.blankonlinux.or.id/Kinect Explorer For SharePoint 2010: Kinect Explorer for SharePoint is a tool which provide Natural User Interface to browse through SharePoint sites. Use body gestures to browse, read, move, copy documents. Use Speech services to read-out the files.MCU: mcu devMVC3ShellCode: MVC3ShellCode MVC3ShellCode MVC3ShellCode MVC3ShellCode MVC3ShellCode MVC3ShellCode NetWatch: NetWatch - network watchdog Small application primary designed for network connectivity monitoring. You can configure set of network tests (ping, http, ...) and time plan for this tests. Application is running in windows notification area and notife you each problem. NMortgage: The goal of this project will be to give a prospective home buyer or an existing home owner the insight they need to explore effects of different repayment strategies or different mortgage structures. Nucleo.NET MVP: The Nucleo MVP framework provides a Model-View-Presenter approach that isn't obtrusive, can be utilized in multiple environments, and is versatile. Providing a lot of features you see in other frameworks, the Nucleo MVP framework provides many extensibility points, pretty much allowing you to rewrite most of the framework. It features dynamic injection support, presenter and view initializers (like what you see in ASP.NET MVC), model property injection, attribute- and convention-based vie...P2PShare: This project is to build a new and moden System for p2p file shearing supporting downloads from HTTP, HTTPS, FTP support for P2Pshare client list servers so files can point to a server or a host only file so no servers are used and only p2p is usedPipeLayer: proyecto de sistemas inteligentespython-irgsh: Python library for BlankOn Package Factory - http://irgsh.blankonlinux.or.id/RamGec XNA Controls - Window Elements Library for XNA Solutions: Lightweight, ultra-high performance and flexible library for displaying and managing Window Controls for XNA system. Features its own Window Designer for creating custom windows and controls.RPG Character Generators and Tools: Various tools for pen and paper style role playing games.Screen scraper: A program that can be used to download public domain MP3 and other media such as pdf documents.SharePoint Bdc request library: The given set of classes simplifies an access to the external data, which can be reached through BDC. The library allows to make simple requests for values from external data source, using a BDC Entity Instance Identifier(s) or a value of a certain BDC Entity field. Developed to interact with Business Data Connectivity of SharePoint 2010.testtom03232012git01: testtom03232012git01testtom03232012git02: testtom03232012git02the north star uc: University projectTyphon: Typhon is a role playing simulation management application, much like Nova, but written in MVC/C#.VRE LabTrove-SharePoint connector: The VRE LabTrove-SharePoint Connector provides a means of integrating the ability to view, post to, and edit posts stored in a LabTrove electronic laboratory notebook from within the familiar environment of Microsoft SharePoint. Once installed and configured, these Web Parts give SharePoint users a straightforward way to interact with any LabTrove installation that they wish to use. They also facilitate users to attach data that is stored in a SharePoint Document Library to the LabTrove posts...

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  • Generalist Languages: Dying or Alive and Well?

    - by dsimcha
    Around here, it seems like there's somewhat of a consensus that generalist programming languages (that try to be good at everything, support multiple paradigms, support both very high- and very low-level programming), etc. are a bad idea, and that it's better to pick the right tool for the job and use lots of different languages. I see three major areas where this is flawed: Interfacing multiple languages is always at least a source of friction and is sometimes practically impossible. How severe a problem this is depends on how fine-grained the interfacing is. Near the boundary between the two languages, though, you're basically limited to the intersection of their features, and you have to care about things like binary interfaces that you usually wouldn't. Passing complex data structures (i.e. not just primitives and arrays of primitives) between languages is almost always a hassle. Furthermore, shifting between different syntaxes, different conventions, etc. can be confusing and annoying, though this is a fairly minor complaint. Requirements are never set in stone. I hate picking a language thinking it's the right tool for the job, then realizing that, when some new requirement surfaces, it's actually a terrible choice for that requirement. This has happened to me several times before, usually when working with languages that are very slow, very domain specific and/or has very poor concurrency/parallelism support. When you program in a language for a while, you start to build up a personal toolbox of small utility functions/classes/programs. The value of these goes drastically down if you're forced to use a different language than the one you've accumulated all this code in. What am I missing here? Why shouldn't more focus be placed on generalist languages? Are generalist languages as a category dying or alive and well?

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  • Drawing a sprite or text causes the OpenGl rendering to 'disappear' in SFML

    - by Ken
    I'm using some SFML built in functions to draw sprites and text as an overlay on top of some OpenGL rending in an SFML RenderWindow. The opengl rendering appears fine until I add the code to draw the sprites or text. The sprite or text drawing causes the OpenGL stuff to disappear. The follow code show what I'm trying to do sf::RenderWindow window(sf::VideoMode(viewport.width,viewport.height,32), "SFML Window"); glMatrixMode(GL_PROJECTION); glLoadIdentity(); glOrtho(0,viewport.width,0,viewport.height,0,1); while (window.pollEvent(Event)) { //event handling... //begin drawing glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); glBegin(GL_TRIANGLES); glColor3f(col.x,col.y,col.z); for(int i=0;i<3;i++) glVertex2f(pos.x+verts[i].x,pos.y+verts[i].y); glEnd(); // adding this line causes all the previous opengl triangles not to appear window.draw("Sometext"); window.display(); }

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  • Suggestions required to build an ECommerce Platform

    - by Haris
    For a prospective client we have to offer a solution to provide following system: CMS Order Management Shopping Cart CRM Helpdesk Accounting & Finance Custom Functions In order to save time and to avoid reinvent the wheel our idea is to integrate different off-the-shelf solutions. Their first requirement is that the system has to be hosted in their country which I think will exclude application like Aplicor, Netsuite & Salesforce. Basically the nucleaus would be the CMS which would integrate all the other apps. PHP or .Net based solutions would be our preferences as have inhouse expertise. So far following are few combinations I have come up with: Joomla (CMS) + Virtuemart (Cart+Ordering) + Sugar CRM + Open ERP (finance) + OTRS Magento (CMS+Cart+Ordering) + Sugar CRM + Open ERP (finance) + Helpdesk Ultimate Drupal (CMS) + Ubercart (Cart+Ordering) + Sugar CRM + Open ERP (finance) + Support Ticketing System Sharepoint (CMS) + OptimusBt (Cart+Ordering) + Dynamics CRM + Great Plains + SharepointHQ Dotnetnuke (CMS) + DNNSpot (Cart+Ordering) + Sigma Pro (CRM+Helpdesk) + Open ERP For Helpdesk I liked Zendesk but the server location was the stopping factor, similar for finance and CRM I liked Aplicor. I would not like to go into detailed requirements as it would make things very complex. Could you please suggest me which options are worth enough to start looking into? What other options we have?

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  • Organization standards for large programs

    - by Chronicide
    I'm the only software developer at the company where I work. I was hired straight out of college, and I've been working here for several years. When I started, eveeryone was managing their own data as they saw fit (lots of filing cabinets). Until recently, I've only been tasked with small standalone projects to help with simple workflows. In the beginning of the year I was asked to make a replacement for their HR software. I used SQL Server, Entity Framework, WPF, along with MVVM and Repository/Unit of work patterns. It was a huge hit. I was very happy with how it went, and it was a very solid program. As such, my employer asked me to expand this program into a corporate dashboard that tracks all of their various corporate data domains (People, Salary, Vehicles/Assets, Statistics, etc.) I use integrated authentication, and due to the initial HR build, I can map users to people in positions, so I know who is who when they open the program, and I can show each person a customized dashboard given their work functions. My concern is that I've never worked on such a large project. I'm planning, meeting with end users, developing, documenting, testing and deploying it on my own. I'm part way through the second addition, and I'm seeing that my code is getting disorganized. It's still programmed well, I'm just struggling with the organization of namespaces, classes and the database model. Are there any good guidelines to follow that will help me keep everything straight? As I have it now, I have folders for Data, Repositories/Unit of Work, Views, View Models, XAML Resources and Miscellaneous Utilities. Should I make parent folders for each data domain? Should I make separate EF models per domain instead of the one I have for the entire database? Are there any standards out there for organizing large programs that span multiple data domains? I would appreciate any suggestions.

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  • Remote server's x menus without vino, vnc etc

    - by Fredde
    A question where both google searches, as well as askubuntu and ubuntu forums searches fails though rephrasing the question a number of times. Have a Lubuntu server with some storage and functions and a lubuntu laptop. Previous when running winXP, I had Xming, could start a x-session on the server, got the lxpanel on the laptop, switching, running x-programs without a hitch though the lxpanel menu. A very neat and convenient solution. However the winXP crashed, me moving to lubuntu also for the laptop. still things work, I ssh into the server and can start x-programs without a hitch. But, as with all graphical desktops, I at times need access to the lx menus on the server to find programs and here the problems arise, most finding I got talk about installing VNC, vino etc overkills, avoiding existing X-integration between the servers. I'll like to do as I did with Xming, see the menu system on the server, in my "client's" xwin? Just to see the servers installed software without colliding with the laptop X-server, just using it as normal X-apps.

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  • Approach for developing software that will need to be ported to multiple mobile platforms in the future

    - by Jonathan Henson
    I am currently doing the preliminary design for a new product my company will be pushing out soon. We will start on Android, but then we will need to quickly develop the IPhone, IPad.... and then the Windows 8 ports of the application. Basically the only code that wouldn't be reusable is the view specific code and the multimedia functions. This will be an SIP client (of course the user of the app will not know this) with several bells and whistles for our own business specific purposes. My initial thought is to develop all of the engine in C and provide a nice API for the C library since JAVA and .NET will allow native invoking, and I should just be able to directly link to the C lib in objective-C. Is there a better approach for vast code reuse which also remains close to the native platform? I.e. I don't want dependencies such as Mono-droid and the like or complicated interpreter/translator schemes. I don't mind re-coding the view(s) for each platform, but I do not want to have multiple versions of the main engine. Also, if I want to have some good abstraction mechanisms (like I would in say, C++) is this possible? I have read that C++ is not allowed for the IPad and Iphone devices. I would love to handle the media decoding in the C library, but I assume that this will be platform dependent so that probably will not be an option either. Any ideas here?

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  • JavaScript 3D space ship rotation

    - by user36202
    I am working with a fairly low-level JavaScript 3D API (not Three.js) which uses euler angles for rotation. In most cases, euler angles work quite well for doing things like aligning buildings, operating a hovercraft, or looking around in the first-person. However, in space there is no up or down. I want to control the ship's roll, pitch, and yaw. To do that, some people would use a local coordinate system or a permenant matrix or quaternion or whatever to represent the ship's angle. However, since I am not most people and am using a library that deals exclusively in euler angles, I will be using relative angles to represent how to rotate the ship in space and getting the resulting non-relative euler angles. For you math nerds, that means I need to convert 3 euler angles (with Y being the vertical axis, X representing the pitch, and Z representing a roll which is unaffected by the other angles, left-handed system) into a 3x3 orientation matrix, do something fancy with the matrix, and convert it back into the 3 euler angles. Euler to matrix to euler. Somebody has posted something similar to this on SO (http://stackoverflow.com/questions/1217775/rotating-a-spaceship-model-for-a-space-simulator-game) but he ended up just working with a matrix. This will not do for me. Also, I am using JavaScript, not C++. What I want essentially are the functions do_roll, do_pitch, and do_yaw which only take in and put out euler angles. Many thanks.

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  • Floating point undesireable in highly critical code?

    - by Kirt Undercoffer
    Question 11 in the Software Quality section of "IEEE Computer Society Real-World Software Engineering Problems", Naveda, Seidman, lists fp computation as undesirable because "the accuracy of the computations cannot be guaranteed". This is in the context of computing acceleration for an emergency braking system for a high speed train. This thinking seems to be invoking possible errors in small differences between measurements of a moving object but small differences at slow speeds aren't a problem (or shouldn't be), small differences between two measurements at high speed are irrelevant - can there be a problem with small roundoff errors during deceleration for an emergency braking system? This problem has been observed with airplane braking systems resulting in hydroplaning but could this actually happen in the context of a high speed train? The concern about fp errors seems to not be well-founded in this context. Any insight? The fp is used for acceleration so perhaps the concern is inching over a speed limit? But fp should be just fine if they use a double in whatever implementation language. The actual problem in the text states: During the inspection of the code for the emergency braking system of a new high speed train (a highly critical, real-time application), the review team identifies several characteristics of the code. Which of these characteristics are generally viewed as undesirable? The code contains three recursive functions (well that one is obvious). The computation of acceleration uses floating point arithmetic. All other computations use integer arithmetic. The code contains one linked list that uses dynamic memory allocation (second obvious problem). All inputs are checked to determine that they are within expected bounds before they are used.

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  • the correct way to deal with gtk_events_pending and gtk_main_iteration

    - by abd alsalam
    I have program that send files and i want to make a progress bar for it, but that progress bar just updated after the transferring complete,so i putted a gtk_events_pending() and gtk_main_iteration() functions in the sending loop to go back to the gtk main loop to update the progress bar but also it seems to not work here is a EDIT: the send function is in a separated thread snippet from my code float Percent = 0.0 ; float Interval = 0.0 ; the sending function gint SendTheFile ( ) { char FileBlockBuffer[512]; bzero(FileBlockBuffer, 512); int FileBlockSize ; FILE * FilePointer ; int filesize = 0 ; FilePointer = fopen(LocalFileName , "r"); struct stat st; stat(LocalFileName, &st); filesize = st.st_size; Interval = (512 / (float)filesize) ; while((FileBlockSize = fread(FileBlockBuffer,sizeof(char),512,FilePointer))>0) { send(SocketDiscriptor , FileBlockBuffer , FileBlockSize,0); bzero(FileBlockBuffer, 512); Percent = Percent + Interval ; if (Percent > 1.0)Percent = 0.0; while(gtk_events_pending() ) { gtk_main_iteration(); } } update progress bar function gint UpdateProgressBar(gpointer data) { gtk_progress_bar_set_fraction(GTK_PROGRESS_BAR(data),Percent); } updating progress bar in the main function g_timeout_add(50,(GSourceFunc)UpdateProgressBar,SendFileProgressBar);

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  • Composing programs from small simple pieces: OOP vs Functional Programming

    - by Jay Godse
    I started programming when imperative programming languages such as C were virtually the only game in town for paid gigs. I'm not a computer scientist by training so I was only exposed to Assembler and Pascal in school, and not Lisp or Prolog. Over the 1990s, Object-Oriented Programming (OOP) became more popular because one of the marketing memes for OOP was that complex programs could be composed of loosely coupled but well-defined, well-tested, cohesive, and reusable classes and objects. And in many cases that is quite true. Once I learned object-oriented programming my C programs became better because I structured them more like classes and objects. In the last few years (2008-2014) I have programmed in Ruby, an OOP language. However, Ruby has many functional programming (FP) features such as lambdas and procs, which enable a different style of programming using recursion, currying, lazy evaluation and the like. (Through ignorance I am at a loss to explain why these techniques are so great). Very recently, I have written code to use methods from the Ruby Enumerable library, such as map(), reduce(), and select(). Apparently this is a functional style of programming. I have found that using these methods significantly reduce code volume, and make my code easier to debug. Upon reading more about FP, one of the marketing claims made by advocates is that FP enables developers to compose programs out of small well-defined, well-tested, and reusable functions, which leads to less buggy code, and low code volume. QUESTIONS: Is the composition of complex program by using FP techniques contradictory to or complementary to composition of a complex program by using OOP techniques? In which situations is OOP more effective, and when is FP more effective? Is it possible to use both techniques in the same complex program? Do the techniques overlap or contradict each other?

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  • Configuring permissions with Bastille

    - by Lucio
    I was using Bastille to improve the security of OS and I found the next question there I don't know if I should answer for YES or NOT: Questions: Would you like to set more restrictive permissions on the administration utilities? Explanation: In general, the default file permissions set by most vendors are fairly secure. To make them more secure, though, you can remove non-root user access to some administrator functions. If you choose this option, you'll be changing the permissions on some common system administration utilities so that they're not readable or executable by users other than root. These utilities (which include linuxconf, fsck, ipconfig, runlevel and portmap) are ones that most users could never have a need to access. This option will increase your system security, but there's a chance it will inconvenience your users. My users: When I installed Ubuntu I had create a user (admin), then I was able to create another user (people) but I cannot change the permissions of this user. Questions: The user there I am using like admin it's not the root, right? The effects of this option will affect to the two users (admin & people) or just to people?

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  • Languages like Tcl that have configurable syntax?

    - by boost
    I'm looking for a language that will let me do what I could do with Clipper years ago, and which I can do with Tcl, namely add functionality in a way other than just adding functions. For example in Clipper/(x)Harbour there are commands #command, #translate, #xcommand and #xtranslate that allow things like this: #xcommand REPEAT; => DO WHILE .T. #xcommand UNTIL <cond>; => IF (<cond>); ;EXIT; ;ENDIF; ;ENDDO LOCAL n := 1 REPEAT n := n + 1 UNTIL n > 100 Similarly, in Tcl I'm doing proc process_range {_for_ project _from_ dat1 _to_ dat2 _by_ slice} { set fromDate [clock scan $dat1] set toDate [clock scan $dat2] if {$slice eq "day"} then {set incrementor [expr 24 * 60]} if {$slice eq "hour"} then {set incrementor 60} set method DateRange puts "Scanning from [clock format $fromDate -format "%c"] to [clock format $toDate -format "%c"] by $slice" for {set dateCursor $fromDate} {$dateCursor <= $toDate} {set dateCursor [clock add $dateCursor $incrementor minutes]} { # ... } } process_range for "client" from "2013-10-18 00:00" to "2013-10-20 23:59" by day Are there any other languages that permit this kind of, almost COBOL-esque, syntax modification? If you're wondering why I'm asking, it's for setting up stuff so that others with a not-as-geeky-as-I-am skillset can declare processing tasks.

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  • forward motion car physics - gradual slow

    - by spartan2417
    Im having trouble creating realistic car movements in xna 4. Right now i have a car going forward and hitting a terminal velocity which is fine but when i release the up key i need to the car to slow down gradually and then come to a stop. Im pretty sure this is easy code but i cant seem to get it to work the code - update if (Keyboard.GetState().IsKeyDown(Keys.Up)) { double elapsedTime = gameTime.ElapsedGameTime.Milliseconds; CalcTotalForce(); Acceleration = Vector2.Divide(CalcTotalForce(), MASS); Velocity = Vector2.Add(Velocity, Vector2.Multiply(Acceleration, (float)(elapsedTime))); Position = Vector2.Add(Position, Vector2.Multiply(Velocity, (float)(elapsedTime))); } added functions public Vector2 CalcTraction() { //Traction force = vector direction * engine force return Vector2.Multiply(forwardDirection, ENGINE_FORCE); } public Vector2 CalcDrag() { //Drag force = constdrag * velocity * speed return Vector2.Multiply(Vector2.Multiply(Velocity, DRAG_CONST), Velocity.Y); } public Vector2 CalcRoll() { //roll force = const roll * velocity return Vector2.Multiply(Velocity, ROLL_CONST); } public Vector2 CalcTotalForce() { //total force = traction + (-drag) + (-rolling) return Vector2.Add(CalcTraction(), Vector2.Add(-CalcDrag(), -CalcRoll())); } anyone have any ideas?

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  • Windows Phone 7 : Dragging and flicking UI controls

    - by TechTwaddle
    Who would want to flick and drag UI controls!? There might not be many use cases but I think some concepts here are worthy of a post. So we will create a simple silverlight application for windows phone 7, containing a canvas element on which we’ll place a button control and an image and then, as the title says, drag and flick the controls. Here’s Mainpage.xaml, <Grid x:Name="LayoutRoot" Background="Transparent">   <Grid.RowDefinitions>     <RowDefinition Height="Auto"/>     <RowDefinition Height="*"/>   </Grid.RowDefinitions>     <!--TitlePanel contains the name of the application and page title-->   <StackPanel x:Name="TitlePanel" Grid.Row="0" Margin="12,17,0,28">     <TextBlock x:Name="ApplicationTitle" Text="KINETICS" Style="{StaticResource PhoneTextNormalStyle}"/>     <TextBlock x:Name="PageTitle" Text="drag and flick" Margin="9,-7,0,0" Style="{StaticResource PhoneTextTitle1Style}"/>   </StackPanel>     <!--ContentPanel - place additional content here-->   <Grid x:Name="ContentPanel" Grid.Row="1" >     <Canvas x:Name="MainCanvas" HorizontalAlignment="Stretch" VerticalAlignment="Stretch">       <Canvas.Background>         <LinearGradientBrush StartPoint="0 0" EndPoint="0 1">           <GradientStop Offset="0" Color="Black"/>           <GradientStop Offset="1.5" Color="BlanchedAlmond"/>         </LinearGradientBrush>       </Canvas.Background>     </Canvas>   </Grid> </Grid> the second row in the main grid contains a canvas element, MainCanvas, with its horizontal and vertical alignment set to stretch so that it occupies the entire grid. The canvas background is a linear gradient brush starting with Black and ending with BlanchedAlmond. We’ll add the button and image control to this canvas at run time. Moving to Mainpage.xaml.cs the Mainpage class contains the following members, public partial class MainPage : PhoneApplicationPage {     Button FlickButton;     Image FlickImage;       FrameworkElement ElemToMove = null;     double ElemVelX, ElemVelY;       const double SPEED_FACTOR = 60;       DispatcherTimer timer; FlickButton and FlickImage are the controls that we’ll add to the canvas. ElemToMove, ElemVelX and ElemVelY will be used by the timer callback to move the ui control. SPEED_FACTOR is used to scale the velocities of ui controls. Here’s the Mainpage constructor, // Constructor public MainPage() {     InitializeComponent();       AddButtonToCanvas();       AddImageToCanvas();       timer = new DispatcherTimer();     timer.Interval = TimeSpan.FromMilliseconds(35);     timer.Tick += new EventHandler(OnTimerTick); } We’ll look at those AddButton and AddImage functions in a moment. The constructor initializes a timer which fires every 35 milliseconds, this timer will be started after the flick gesture completes with some inertia. Back to AddButton and AddImage functions, void AddButtonToCanvas() {     LinearGradientBrush brush;     GradientStop stop1, stop2;       Random rand = new Random(DateTime.Now.Millisecond);       FlickButton = new Button();     FlickButton.Content = "";     FlickButton.Width = 100;     FlickButton.Height = 100;       brush = new LinearGradientBrush();     brush.StartPoint = new Point(0, 0);     brush.EndPoint = new Point(0, 1);       stop1 = new GradientStop();     stop1.Offset = 0;     stop1.Color = Colors.White;       stop2 = new GradientStop();     stop2.Offset = 1;     stop2.Color = (Application.Current.Resources["PhoneAccentBrush"] as SolidColorBrush).Color;       brush.GradientStops.Add(stop1);     brush.GradientStops.Add(stop2);       FlickButton.Background = brush;       Canvas.SetTop(FlickButton, rand.Next(0, 400));     Canvas.SetLeft(FlickButton, rand.Next(0, 200));       MainCanvas.Children.Add(FlickButton);       //subscribe to events     FlickButton.ManipulationDelta += new EventHandler<ManipulationDeltaEventArgs>(OnManipulationDelta);     FlickButton.ManipulationCompleted += new EventHandler<ManipulationCompletedEventArgs>(OnManipulationCompleted); } this function is basically glorifying a simple task. After creating the button and setting its height and width, its background is set to a linear gradient brush. The direction of the gradient is from top towards bottom and notice that the second stop color is the PhoneAccentColor, which changes along with the theme of the device. The line,     stop2.Color = (Application.Current.Resources["PhoneAccentBrush"] as SolidColorBrush).Color; does the magic of extracting the PhoneAccentBrush from application’s resources, getting its color and assigning it to the gradient stop. AddImage function is straight forward in comparison, void AddImageToCanvas() {     Random rand = new Random(DateTime.Now.Millisecond);       FlickImage = new Image();     FlickImage.Source = new BitmapImage(new Uri("/images/Marble.png", UriKind.Relative));       Canvas.SetTop(FlickImage, rand.Next(0, 400));     Canvas.SetLeft(FlickImage, rand.Next(0, 200));       MainCanvas.Children.Add(FlickImage);       //subscribe to events     FlickImage.ManipulationDelta += new EventHandler<ManipulationDeltaEventArgs>(OnManipulationDelta);     FlickImage.ManipulationCompleted += new EventHandler<ManipulationCompletedEventArgs>(OnManipulationCompleted); } The ManipulationDelta and ManipulationCompleted handlers are same for both the button and the image. OnManipulationDelta() should look familiar, a similar implementation was used in the previous post, void OnManipulationDelta(object sender, ManipulationDeltaEventArgs args) {     FrameworkElement Elem = sender as FrameworkElement;       double Left = Canvas.GetLeft(Elem);     double Top = Canvas.GetTop(Elem);       Left += args.DeltaManipulation.Translation.X;     Top += args.DeltaManipulation.Translation.Y;       //check for bounds     if (Left < 0)     {         Left = 0;     }     else if (Left > (MainCanvas.ActualWidth - Elem.ActualWidth))     {         Left = MainCanvas.ActualWidth - Elem.ActualWidth;     }       if (Top < 0)     {         Top = 0;     }     else if (Top > (MainCanvas.ActualHeight - Elem.ActualHeight))     {         Top = MainCanvas.ActualHeight - Elem.ActualHeight;     }       Canvas.SetLeft(Elem, Left);     Canvas.SetTop(Elem, Top); } all it does is calculate the control’s position, check for bounds and then set the top and left of the control. OnManipulationCompleted() is more interesting because here we need to check if the gesture completed with any inertia and if it did, start the timer and continue to move the ui control until it comes to a halt slowly, void OnManipulationCompleted(object sender, ManipulationCompletedEventArgs args) {     FrameworkElement Elem = sender as FrameworkElement;       if (args.IsInertial)     {         ElemToMove = Elem;           Debug.WriteLine("Linear VelX:{0:0.00}  VelY:{1:0.00}", args.FinalVelocities.LinearVelocity.X,             args.FinalVelocities.LinearVelocity.Y);           ElemVelX = args.FinalVelocities.LinearVelocity.X / SPEED_FACTOR;         ElemVelY = args.FinalVelocities.LinearVelocity.Y / SPEED_FACTOR;           timer.Start();     } } ManipulationCompletedEventArgs contains a member, IsInertial, which is set to true if the manipulation was completed with some inertia. args.FinalVelocities.LinearVelocity.X and .Y will contain the velocities along the X and Y axis. We need to scale down these values so they can be used to increment the ui control’s position sensibly. A reference to the ui control is stored in ElemToMove and the velocities are stored as well, these will be used in the timer callback to access the ui control. And finally, we start the timer. The timer callback function is as follows, void OnTimerTick(object sender, EventArgs e) {     if (null != ElemToMove)     {         double Left, Top;         Left = Canvas.GetLeft(ElemToMove);         Top = Canvas.GetTop(ElemToMove);           Left += ElemVelX;         Top += ElemVelY;           //check for bounds         if (Left < 0)         {             Left = 0;             ElemVelX *= -1;         }         else if (Left > (MainCanvas.ActualWidth - ElemToMove.ActualWidth))         {             Left = MainCanvas.ActualWidth - ElemToMove.ActualWidth;             ElemVelX *= -1;         }           if (Top < 0)         {             Top = 0;             ElemVelY *= -1;         }         else if (Top > (MainCanvas.ActualHeight - ElemToMove.ActualHeight))         {             Top = MainCanvas.ActualHeight - ElemToMove.ActualHeight;             ElemVelY *= -1;         }           Canvas.SetLeft(ElemToMove, Left);         Canvas.SetTop(ElemToMove, Top);           //reduce x,y velocities gradually         ElemVelX *= 0.9;         ElemVelY *= 0.9;           //when velocities become too low, break         if (Math.Abs(ElemVelX) < 1.0 && Math.Abs(ElemVelY) < 1.0)         {             timer.Stop();             ElemToMove = null;         }     } } if ElemToMove is not null, we get the top and left values of the control and increment the values with their X and Y velocities. Check for bounds, and if the control goes out of bounds we reverse its velocity. Towards the end, the velocities are reduced by 10% every time the timer callback is called, and if the velocities reach too low values the timer is stopped and ElemToMove is made null. Here’s a short video of the program, the video is a little dodgy because my display driver refuses to run the animations smoothly. The flicks aren’t always recognised but the program should run well on an actual device (or a pc with better configuration), You can download the source code from here: ButtonDragAndFlick.zip

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  • How to apply verification and validation on the following example

    - by user970696
    I have been following verification and validation questions here with my colleagues, yet we are unable to see the slight differences, probably caused by language barrier in technical English. An example: Requirement specification User wants to control the lights in 4 rooms by remote command sent from the UI for each room separately. Functional specification The UI will contain 4 checkboxes labelled according to rooms they control. When a checkbox is checked, the signal is sent to corresponding light. A green dot appears next to the checkbox When a checkbox is unchecked, the signal (turn off) is sent to corresponding light. A red dot appears next to the checkbox. Let me start with what I learned here: Verification, according to many great answers here, ensures that product reflects specified requirements - as functional spec is done by a producer based on requirements from customer, this one will be verified for completeness, correctness). Then design document will be checked against functional spec (it should design 4 checkboxes..), and the source code against design (is there a code for 4 checkboxes, functions to send the signals etc. - is it traceable to requirements). Okay, product is built and we need to test it, validate. Here comes our understanding trouble - validation should ensure the product meets requirements for its specific intended use which is basically business requirement (does it work? can I control the lights from the UI?) but testers will definitely work with the functional spec, making sure the checkboxes are there, working, labelled, etc. They are basically checking whether the requirements in functional spec were met in the final product, isn't that verification? (should not be, lets stick to ISO 12207 that only validation is the actual testing)

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  • Database Driven Web Application, C# Front-End and F# Back-End meaning

    - by user1473053
    Hi I am an intern working with ASP.NET. My current task is to make a website which will incorporate some jquery viewing features. This project seems to me will be primarily dealing with reading data from a database and making graphs out of them. This will require me to make custom queries from whatever the client is looking at. I think it is going to be what this guy calls an Ad Hoc Query tool My plan for this is to make it a database-driven website. So I can utilize the jquery dynamic viewing capabilities. I stumbled upon the functional programming paradigm and found F#. I read that because of it's functional programming paradigm, it makes it a good language to do asynchronous functions. I read about how you can use this with LINQ to SQL and how easy it is to make queries without actually putting the query language in. I understand the concept of the MVC design pattern. But I don't understand what they mean about C# being the front-end and F# being the back-end. Can someone clarify this to me? Also what are your thoughts about doing this project in this way? Any comments and thoughts are greatly appreciated. I feel as if learning F# will be a great learning experience for me. My guess is that the F# back-end is like the part where it controls the calls to the database. F# is possibly the model part of the design pattern. And C# is the controller. So HTML, Javascript and Jquery stuff will be my View design pattern. Clarify please?

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  • Javascript Canvas Drawing Efficiency

    - by jujumbura
    I have just recently started some experiments with game development in Javascript/HTML5, and so far it has been going pretty well. I have a simple test scene running with some basic input handling, and a hundred-ish drawImage() calls with a few transforms. This all runs great on Chrome, but unfortunately, it already chugs on Firefox. I am using a very large canvas ( 1920 x 1080 ), but it doesn't seem like I should be hitting my limit already. So on that note, I was hoping to ask a few questions: 1) What exactly is done on the CPU vs. the GPU in terms of canvas and drawImage()? I'm afraid the answer is probably "it depends on the browser", but can anybody give me some rules of thumb? I naively imagined that each drawImage call results in a textured quad on the GPU with the canvas effectively being a render target, but I'm wondering if I'm pretty far off base there... 2) I have seen posts here and there with people saying not to use the translate(), rotate(), scale() functions when drawing on the canvas. Am I adding a lot of overhead just by adding a translate() call, as opposed to passing in the x,y to drawImage()? Some people suggest using "transate3d", etc., which are CSS properties, but I'm not sure how to use them within a scene. Can they be used for animated sprites within a single canvas? 3) I have also seen a lot of posts with people mentioning that pre-building canvases and then re-using them is a lot faster than issuing all the individual draw calls again. I am guessing that my background should definitely be pre-built into a canvas, but how far should I take this? Should I maintain an individual canvas for each sprite, to cache all static image data when not animating? Thank you much for your advice!

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