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• Why do old programming languages continue to be revised?

  - by SunAvatar

  This question is not, "Why do people still use old programming languages?" I understand that quite well. In fact the two programming languages I know best are C and Scheme, both of which date back to the 70s. Recently I was reading about the changes in C99 and C11 versus C89 (which seems to still be the most-used version of C in practice and the version I learned from K&R). Looking around, it seems like every programming language in heavy use gets a new specification at least once per decade or so. Even Fortran is still getting new revisions, despite the fact that most people using it are still using FORTRAN 77. Contrast this with the approach of, say, the typesetting system TeX. In 1989, with the release of TeX 3.0, Donald Knuth declared that TeX was feature-complete and future releases would contain only bug fixes. Even beyond this, he has stated that upon his death, "all remaining bugs will become features" and absolutely no further updates will be made. Others are free to fork TeX and have done so, but the resulting systems are renamed to indicate that they are different from the official TeX. This is not because Knuth thinks TeX is perfect, but because he understands the value of a stable, predictable system that will do the same thing in fifty years that it does now. Why do most programming language designers not follow the same principle? Of course, when a language is relatively new, it makes sense that it will go through a period of rapid change before settling down. And no one can really object to minor changes that don't do much more than codify existing pseudo-standards or correct unintended readings. But when a language still seems to need improvement after ten or twenty years, why not just fork it or start over, rather than try to change what is already in use? If some people really want to do object-oriented programming in Fortran, why not create "Objective Fortran" for that purpose, and leave Fortran itself alone? I suppose one could say that, regardless of future revisions, C89 is already a standard and nothing stops people from continuing to use it. This is sort of true, but connotations do have consequences. GCC will, in pedantic mode, warn about syntax that is either deprecated or has a subtly different meaning in C99, which means C89 programmers can't just totally ignore the new standard. So there must be some benefit in C99 that is sufficient to impose this overhead on everyone who uses the language. This is a real question, not an invitation to argue. Obviously I do have an opinion on this, but at the moment I'm just trying to understand why this isn't just how things are done already. I suppose the question is: What are the (real or perceived) advantages of updating a language standard, as opposed to creating a new language based on the old?

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• Learning by doing (and programming by trial and error)

  - by AlexBottoni

  How do you learn a new platform/toolkit while producing working code and keeping your codebase clean? When I know what I can do with the underlying platform and toolkit, I usually do this: I create a new branch (with GIT, in my case) I write a few unit tests (with JUnit, for example) I write my code until it passes my tests So far, so good. The problem is that very often I do not know what I can do with the toolkit because it is brand new to me. I work as a consulant so I cannot have my preferred language/platform/toolkit. I have to cope with whatever the customer uses for the task at hand. Most often, I have to deal (often in a hurry) with a large toolkit that I know very little so I'm forced to "learn by doing" (actually, programming by "trial and error") and this makes me anxious. Please note that, at some point in the learning process, usually I already have: read one or more five-stars books followed one or more web tutorials (writing working code a line at a time) created a couple of small experimental projects with my IDE (IntelliJ IDEA, at the moment. I use Eclipse, Netbeans and others, as well.) Despite all my efforts, at this point usually I can just have a coarse understanding of the platform/toolkit I have to use. I cannot yet grasp each and every detail. This means that each and every new feature that involves some data preparation and some non-trivial algorithm is a pain to implement and requires a lot of trial-and-error. Unfortunately, working by trial-and-error is neither safe nor easy. Actually, this is the phase that makes me most anxious: experimenting with a new toolkit while producing working code and keeping my codebase clean. Usually, at this stage I cannot use the Eclipse Scrapbook because the code I have to write is already too large and complex for this small tool. In the same way, I cannot use any more an indipendent small project for my experiments because I need to try the new code in place. I can just write my code in place and rely on GIT for a safe bail-out. This makes me anxious because this kind of intertwined, half-ripe code can rapidly become incredibly hard to manage. How do you face this phase of the development process? How do you learn-by-doing without making a mess of your codebase? Any tips&tricks, best practice or something like that?

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• Self-Executing Anonymous Function vs Prototype

  - by Robotsushi

  In Javascript there are a few clearly prominent techniques for create and manage classes/namespaces in javascript. I am curious what situations warrant using one technique vs. the other. I want to pick one and stick with it moving forward. I write enterprise code that is maintained and shared across multiple teams, and I want to know what is the best practice when writing maintainable javascript ? I tend to prefer Self-Executing Anonymous Functions however I am curious what the community vote is on these techniques. Prototype : function obj() { } obj.prototype.test = function() { alert('Hello?'); }; var obj2 = new obj(); obj2.test(); Self-Closing Anonymous Function : //Self-Executing Anonymous Function (function( skillet, $, undefined ) { //Private Property var isHot = true; //Public Property skillet.ingredient = "Bacon Strips"; //Public Method skillet.fry = function() { var oliveOil; addItem( "\t\n Butter \n\t" ); addItem( oliveOil ); console.log( "Frying " + skillet.ingredient ); }; //Private Method function addItem( item ) { if ( item !== undefined ) { console.log( "Adding " + $.trim(item) ); } } }( window.skillet = window.skillet || {}, jQuery )); //Public Properties console.log( skillet.ingredient ); //Bacon Strips //Public Methods skillet.fry(); //Adding Butter & Fraying Bacon Strips //Adding a Public Property skillet.quantity = "12"; console.log( skillet.quantity ); //12 //Adding New Functionality to the Skillet (function( skillet, $, undefined ) { //Private Property var amountOfGrease = "1 Cup"; //Public Method skillet.toString = function() { console.log( skillet.quantity + " " + skillet.ingredient + " & " + amountOfGrease + " of Grease" ); console.log( isHot ? "Hot" : "Cold" ); }; }( window.skillet = window.skillet || {}, jQuery )); //end of skillet definition try { //12 Bacon Strips & 1 Cup of Grease skillet.toString(); //Throws Exception } catch( e ) { console.log( e.message ); //isHot is not defined } I feel that I should mention that the Self-Executing Anonymous Function is the pattern used by the jQuery team. Update When I asked this question I didn't truly see the importance of what I was trying to understand. The real issue at hand is whether or not to use new to create instances of your objects or to use patterns which do not require constructors of the use of the new keyword. I added my own answer, because in my opinion we should make use of patterns which don't use the new keyword. For more information please see my answer.

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• Turn-Based RPG Battle Instance Layout For Larger Groups

  - by SoulBeaver

  What a title, eh? I'm currently designing a videogame; a turn-based RPG like Final Fantasy (because everybody knows Final Fantasy). It's a 2D sprite game. These are my ideas for combat: -The player has a group of 15 members (main character included) -During battle, five of the group are designated as active, and appear in the battle. -These five may be switched out at leisure, or when one of the five die. -At any time, the Waiting members can cast buffs, be healed by the active members, or perform special attacks. -Battles should contain 10+ monsters at least. I'm aiming for 20, but I'm not sure if that's possible yet. -Battles should feel larger than normal due to the interaction of Waiting members, active members and the increased amount of monsters per battle. -The player has two rows in which to put the Active members: front and back. -Depending on the implementation, I might allow comboing of player attacks and skills. These are just design ideas, so beware! I have not been able to test this out yet- I have no idea yet if any of these ideas bunched together will make for a compelling game. What sounds good on paper doesn't necessarily have to be good in practice! What I'm asking now is how to create the layout for this. My starting point are the battles in Final Fantasy VI, with up to 5-6 monsters on the left and the characters on the right- monsters on both sides if it's a pincer attack. However, this view would not work feasible with my goal of 20 monsters and 5 characters. All the monsters on the left would appear cluttered unless I scale them far far back. If I create a pincer-like map, then there would be no real pincer-attack possible. If I space the monsters out I force the player to scroll the screen- a game mechanic I've come across and not enjoyed imho. My question is: does anybody have any layouts or guides for designing battle maps in turn-based RPGs, especially with a larger number of enemies taken into consideration? How should it look? I am not asking for specific combat mechanics, just the layout for the moment.

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• Professional immigration

  - by etranger

  Hello all, Does anyone here have a practical advice on professional relocation from Russia to Europe? The reasons behind making such a decision are far beyond the subject, perhaps, so I'll stick to the practical part. Having done some of the "common stuff" for finding a job, I am now facing two serious problems: I am a "dual-class" person, with university degree in marketing, and multiple years of self-studied computer competence (hence my writing here). Have professional experience in both areas. I don't currently hold a European work permit. From what I can see, this results in normal HR person throwing out my CV as either being "overqualified" or "too much trouble with making the permit". I do have the skills and character to start my own business, but it requires start-up capital that I don't have, over the last years I had to pay high bills for medical treatment of my family member, who had deceased. Now, I'm almost out of debts. As you can probably guess, English is not a problem, and I'm open to new languages, but first steps of entering the market, or the society, is the problematic part. I live close to Norway, and am trying to get some professional contacts there, but it hasn't got me any practical perspective so far. Any advice is greatly appreciated. EDIT: I am currently making my living off web site development, and occasional consulting services both in IT and marketing. For purely geographic reasons I'm dealing with clients that reside in the same city where I live, pop. 350 000. Being quite local, market requirements for web sites are simple and stable — clients need to control navigation, write articles in a word-like editor, upload illustrations and place ad banners, all with no additional programming. As many web developers do, I'm using my own content management system that fits these expectations. I have also started developing a newer version of this system that has better support for international environments, but I'm too distant from the real market demand in Europe to speak of the right track here. Technically it's based on php/mysql and uses xslt for templating. It allows for quick website deployment, and has architectural neatness, lack of which made me abandon similar opensource solutions (Joomla and the like). Deploying time from rasterized design proofs is normally under 6-8 working hours, don't know how that compares to the world practice. EDIT 2: Can anyone share what Norwegian (Scandinavian) web solutions market currently demands?

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• Adding Facebook Open Graph Tags to an MVC Application

  - by amaniar

  If you have any kind of share functionality within your application it’s a good practice to add the basic Facebook open graph tags to the header of all pages. For an MVC application this can be as simple as adding these tags to the Head section of the Layouts file.<head> <title>@ViewBag.Title</title> <meta property="og:title" content="@ViewBag.FacebookTitle" /> <meta property="og:type" content="website"/> <meta property="og:url" content="@ViewBag.FacebookUrl"/> <meta property="og:image" content="@ViewBag.FacebookImage"/> <meta property="og:site_name" content="Site Name"/> <meta property="og:description" content="@ViewBag.FacebookDescription"/></head>  These ViewBag properties can then be populated from any action: private ActionResult MyAction() { ViewBag.FacebookDescription = "My Actions Description"; ViewBag.FacebookUrl = "My Full Url"; ViewBag.FacebookTitle = "My Actions Title"; ViewBag.FacebookImage = "My Actions Social Image"; .... } You might want to populate these ViewBag properties with default values when the actions don’t populate them. This can be done in 2 places. 1. In the Layout itself. (check the ViewBag properties and set them if they are empty) @{ ViewBag.FacebookTitle = ViewBag.FacebookTitle ?? "My Default Title"; ViewBag.FacebookUrl = ViewBag.FacebookUrl ?? HttpContext.Current.Request.RawUrl; ViewBag.FacebookImage = ViewBag.FacebookImage ?? "http://www.mysite.com/images/logo_main.png"; ViewBag.FacebookDescription = ViewBag.FacebookDescription ?? "My Default Description"; }  2. Create an action filter and add it to all Controllers or your base controller. public class FacebookActionFilterAttribute : ActionFilterAttribute { public override void OnActionExecuting(ActionExecutingContext filterContext) { var viewBag = filterContext.Controller.ViewBag; viewBag.FacebookDescription = "My Actions Description"; viewBag.FacebookUrl = "My Full Url"; viewBag.FacebookTitle = "My Actions Title"; viewBag.FacebookImage = "My Actions Social Image"; base.OnActionExecuting(filterContext); } } Add attribute to your BaseController. [FacebookActionFilter] public class HomeController : Controller { .... }

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• Are these non-standard applications of rendering practical in games?

  - by maul

  I've recently got into 3D and I came up with a few different "tricky" rendering techniques. Unfortunately I don't have the time to work on this myself, but I'd like to know if these are known methods and if they can be used in practice. Hybrid rendering Now I know that ray-tracing is still not fast enough for real-time rendering, at least on home computers. I also know that hybrid rendering (a combination of rasterization and ray-tracing) is a well known theory. However I had the following idea: one could separate a scene into "important" and "not important" objects. First you render the "not important" objects using traditional rasterization. In this pass you also render the "important" objects using a special shader that simply marks these parts on the image using a special color, or some stencil/depth buffer trickery. Then in the second pass you read back the results of the first pass and start ray tracing, but only from the pixels that were marked by the "important" object's shader. This would allow you to only ray-trace exactly what you need to. Could this be fast enough for real-time effects? Rendered physics I'm specifically talking about bullet physics - intersection of a very small object (point/bullet) that travels across a straight line with other, relatively slow-moving, fairly constant objects. More specifically: hit detection. My idea is that you could render the scene from the point of view of the gun (or the bullet). Every object in the scene would draw a different color. You only need to render a 1x1 pixel window - the center of the screen (again, from the gun's point of view). Then you simply check that central pixel and the color tells you what you hit. This is pixel-perfect hit detection based on the graphical representation of objects, which is not common in games. Afaik traditional OpenGL "picking" is a similar method. This could be extended in a few ways: For larger (non-bullet) objects you render a larger portion of the screen. If you put a special-colored plane in the middle of the scene (exactly where the bullet will be after the current frame) you get a method that works as the traditional slow-moving iterative physics test as well. You could simulate objects that the bullet can pass through (with decreased velocity) using alpha blending or some similar trick. So are these techniques in use anywhere, and/or are they practical at all?

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• Should Item Grouping/Filter be in the ViewModel or View layer?

  - by ronag

  I'm in a situation where I have a list of items that need to be displayed depending on their properties. What I'm unsure of is where is the best place to put the filtering/grouping logic of the viewmodel state? Currently I have it in my view using converters, but I'm unsure whether I should have the logic in the viewmodel? e.g. ViewModel Layer: class ItemViewModel { DateTime LastAccessed { get; set; } bool IsActive { get; set; } } class ContainerViewModel { ObservableCollection<Item> Items {get; set;} } View Layer: <TextView Text="Active Items"/> <List ItemsSource={Binding Items, Converter=GroupActiveItemsByDay}/> <TextView Text="Active Items"/> <List ItemsSource={Binding Items, Converter=GroupInActiveItemsByDay}/> or should I build it like this? ViewModel Layer: class ContainerViewModel { ObservableCollection<IGrouping<string, Item>> ActiveItemsByGroup {get; set;} ObservableCollection<IGrouping<string, Item>> InActiveItemsByGroup {get; set;} } View Layer: <TextView Text="Active Items"/> <List ItemsSource={Binding ActiveItemsGroupByDate }/> <TextView Text="Active Items"/> <List ItemsSource={Binding InActiveItemsGroupByDate }/> Or maybe something in between? ViewModel Layer: class ContainerViewModel { ObservableCollection<IGrouping<string, Item>> ActiveItems {get; set;} ObservableCollection<IGrouping<string, Item>> InActiveItems {get; set;} } View Layer: <TextView Text="Active Items"/> <List ItemsSource={Binding ActiveItems, Converter=GroupByDate }/> <TextView Text="Active Items"/> <List ItemsSource={Binding InActiveItems, Converter=GroupByDate }/> I guess my question is what is good practice in terms as to what logic to put into the ViewModel and what logic to put into the Binding in the View, as they seem to overlap a bit?

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• How do I keep user input and rendering independent of the implementation environment?

  - by alex

  I'm writing a Tetris clone in JavaScript. I have a fair amount of experience in programming in general, but am rather new to game development. I want to separate the core game code from the code that would tie it to one environment, such as the browser. My quick thoughts led me to having the rendering and input functions external to my main game object. I could pass the current game state to the rendering method, which could render using canvas, elements, text, etc. I could also map input to certain game input events, such as move piece left, rotate piece clockwise, etc. I am having trouble designing how this should be implemented in my object. Should I pass references to functions that the main object will use to render and process user input? For example... var TetrisClone = function(renderer, inputUpdate) { this.renderer = renderer || function() {}; this.inputUpdate = input || function() {}; this.state = {}; }; TetrisClone.prototype = { update: function() { // Get user input via function passed to constructor. var inputEvents = this.inputUpdate(); // Update game state. // Render the current game state via function passed to constructor. this.renderer(this.state); } }; var renderer = function(state) { // Render blocks to browser page. } var inputEvents = {}; var charCodesToEvents = { 37: "move-piece-left" /* ... */ }; document.addEventListener("keypress", function(event) { inputEvents[event.which] = true; }); var inputUpdate = function() { var translatedEvents = [], event, translatedEvent; for (event in inputEvents) { if (inputEvents.hasOwnProperty(event)) { translatedEvent = charCodesToEvents[event]; translatedEvents.push(translatedEvent); } } inputEvents = {}; return translatedEvents; } var game = new TetrisClone(renderer, inputUpdate); Is this a good game design? How would you modify this to suit best practice in regard to making a game as platform/input independent as possible?

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• Notes - Part I - Say Hello from Java

  - by Silviu Turuga

  Sometimes we need to take small notes to remember things, one way to do this is to use stick notes and have them all around our desktop. But what happening if you have a lot of notes and a small office? You'll need a piece of software that will sort things for you and also it will provide you a quick way to retrieve the notes when need. Did I mention that this will keep your desktop clean and also will reduce paper waste? During the next days we'll gonna create an application that will let you manage your notes, put them in different categories etc. I'll show you step by step what do you need to do and finally you'll have the application run on multiple systems, such as Mac, Windows, Linux, etc. The only pre-requisition for this lesson is to have JDK 7 with JavaFX installed and an IDE, preferably NetBeans. I'll call this application Notes…. Part I - Say Hello from Java  From NetBeans go to Files->New Project Chose JavaFX->JavaFX FXML Application Project Name: Notes FXML name: NotesUI Check Create Application Class and name it Main After this the project is created and you'll see the following structure As a best practice I advice you to have your code in your own package instead of the default one. right click on Source Packages and chose New->Java Package name it something like this: com.turuga.notes and click Next after the package is created, select all the 3 files from step #3 and drag them over the new package chose Refactor, as this will make sure all the references are correctly moved inside the new package now you should have the following structure if you'll try to run the project you'll get an error: Unable to find class: Main right click on project name Notes and click properties go to Run and you'll see Application Class set to Main, but because we have defined our own packages, this location has been change, so click on Browse and the correct one appear: com.turuga.notes.Main last modification before running the project is to right click on NotesUI.fxml and chose Edit (if you'll double click it will open in JavaFX Scene Builder) look around line 9 and change fx:controller="NotesUIController" to fx:controller="com.turuga.notes.NotesUIController" now you are ready to run it and you should see the following On the next lesson we'll continue to play with NetBeans and start working on the interface of our project

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• Could I be going crazy with Event Handlers? Am I going the "wrong way" with my design?

  - by sensae

  I guess I've decided that I really like event handlers. I may be suffering a bit from analysis paralysis, but I'm concerned about making my design unwieldy or running into some other unforeseen consequence to my design decisions. My game engine currently does basic sprite-based rendering with a panning overhead camera. My design looks a bit like this: SceneHandler Contains a list of classes that implement the SceneListener interface (currently only Sprites). Calls render() once per tick, and sends onCameraUpdate(); messages to SceneListeners. InputHandler Polls the input once per tick, and sends a simple "onKeyPressed" message to InputListeners. I have a Camera InputListener which holds a SceneHandler instance and triggers updateCamera(); events based on what the input is. AgentHandler Calls default actions on any Agents (AI) once per tick, and will check a stack for any new events that are registered, dispatching them to specific Agents as needed. So I have basic sprite objects that can move around a scene and use rudimentary steering behaviors to travel. I've gotten onto collision detection, and this is where I'm not sure the direction my design is going is good. Is it a good practice to have many, small event handlers? I imagine going the way I am that I'd have to implement some kind of CollisionHandler. Would I be better off with a more consolidated EntityHandler which handles AI, collision updates, and other entity interactions in one class? Or will I be fine just implementing many different event handling subsystems which pass messages to each other based on what kind of event it is? Should I write an EntityHandler which is simply responsible for coordinating all these sub event handlers? I realize in some cases, such as my InputHandler and SceneHandler, those are very specific types of events. A large portion of my game code won't care about input, and a large portion won't care about updates that happen purely in the rendering of the scene. Thus I feel my isolation of those systems is justified. However, I'm asking this question specifically approaching game logic type events.

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• How can you tell whether to use Composite Pattern or a Tree Structure, or a third implementation?

  - by Aske B.

  I have two client types, an "Observer"-type and a "Subject"-type. They're both associated with a hierarchy of groups. The Observer will receive (calendar) data from the groups it is associated with throughout the different hierarchies. This data is calculated by combining data from 'parent' groups of the group trying to collect data (each group can have only one parent). The Subject will be able to create the data (that the Observers will receive) in the groups they're associated with. When data is created in a group, all 'children' of the group will have the data as well, and they will be able to make their own version of a specific area of the data, but still linked to the original data created (in my specific implementation, the original data will contain time-period(s) and headline, while the subgroups specify the rest of the data for the receivers directly linked to their respective groups). However, when the Subject creates data, it has to check if all affected Observers have any data that conflicts with this, which means a huge recursive function, as far as I can understand. So I think this can be summed up to the fact that I need to be able to have a hierarchy that you can go up and down in, and some places be able to treat them as a whole (recursion, basically). Also, I'm not just aiming at a solution that works. I'm hoping to find a solution that is relatively easy to understand (architecture-wise at least) and also flexible enough to be able to easily receive additional functionality in the future. Is there a design pattern, or a good practice to go by, to solve this problem or similar hierarchy problems? EDIT: Here's the design I have: The "Phoenix"-class is named that way because I didn't think of an appropriate name yet. But besides this I need to be able to hide specific activities for specific observers, even though they are attached to them through the groups. A little Off-topic: Personally, I feel that I should be able to chop this problem down to smaller problems, but it escapes me how. I think it's because it involves multiple recursive functionalities that aren't associated with each other and different client types that needs to get information in different ways. I can't really wrap my head around it. If anyone can guide me in a direction of how to become better at encapsulating hierarchy problems, I'd be very glad to receive that as well.

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• Imperative vs. component based programming [closed]

  - by AlexW

  I've been thinking about how programming and more specifically the teaching of programming is advocated amongst the community (online). Often I've heard that Ruby and RoR is an ideal platform for learning to program. I completely disagree... RoR and Ruby are based on the application of the component based paradigm, which means they are ideal for rapid application development. This is much like the MVC model in PHP and ASP.NET But, learning a proper imperative language like Java or C/C++ (or even Perl and PHP) is the only way for a new programmer to explore logic itself, and not get too bogged down in architectural concerns like the need for separation of concerns, and the preference for components. Maybe it's a personal preference thing. I rather think that the most interesting aspects to programming are the procedural bits of code I write that actually do stuff rather than the project planning, and modelling that comes about from fully object oriented engineering or simply using the MVC model. I know this may sound confused to some of you. I feel strongly though that the best way for programming to be taught is through imperative and procedural methods. Architectural (component) methods come later, if at all. After all, none of the amazing algorithms that exist were based on OOP practice! It's all procedural code when it comes to the 'magic'. OOP is useful in creating products and utilities. Algorithms are what makes things happen, and move data around, and so imperative (and/or procedural) code are what matters most. When I see programmers recommending Ruby on Rails to newbie developers, I think it's just so wrong. Just because you write less code with Ruby does not make it easier to do! It's the opposite... you have to know loads more to appreciate its succinct nature. New coders who really want to understand the nuts and bolts of coding need to go away and figure out writing methods/functions (i.e. imperative programming) and working in procedural style, in order to grasp the fundamentals, first, before looking into architectural ways of working. So, my question is: should Ruby ever be recommended as a first language? I think no (obviously)... what arguments are there for it?

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• Normal Redundancy (Double Mirroring) Option Available

  - by TammyBednar

  Normal 0 false false false EN-US X-NONE X-NONE MicrosoftInternetExplorer4 /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-qformat:yes; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin:0in; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:10.0pt; font-family:"Calibri","sans-serif";} The Oracle Database Appliance 2.4 Patch was released last week and provides you an option of ASM normal redundancy (double mirroring) during the initial deployment of the Database Appliance. The default deployment of the Oracle Database Appliance is high redundancy for the +DATA and +RECO disk groups. While there is 12TB of raw shared storage available, the Database Backup Location and Disk Group Redundancy govern how much usable storage is presented after the initial deployment is completed. The Database Backup Location options are Local or External. When the Local Backup Option is selected, this means that 60% of the available shared storage will be allocated for the Fast Recovery Area that contains database backups and archive logs. The External Backup Option will allocate 20% of the available shared storage to the Fast Recovery Area. So, let’s look at an example of High Redundancy and External Backups. Disk Group Redundancy – High --> Triple Mirroring to provide ~4TB of available storage Database Backup Location – External --> 20% of available shared storage allocated to +RECO +DATA = 3.2TB of usable storage, +RECO = 0.8TB of usable storage What about Normal Redundancy with External Backups? Disk Group Redundancy – Normal --> Double Mirroring to provide ~6TB of available storage Database Backup Location – External --> 20% of available shared storage allocated to +RECO +DATA = 4.8TB of usable storage, +RECO = 1.2TB of usable storage As a best practice, we would recommend using Normal Redundancy for your test and/or development Oracle Database Appliances and High Redundancy for production.

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• Why C++ people loves multithreading when it comes to performances?

  - by user1849534

  I have a question, it's about why programmers seems to love concurrency and multi-threaded programs in general. I'm considering 2 main approach here: an async approach basically based on signals, or just an async approach as called by many papers and languages like the new C# 5.0 for example, and a "companion thread" that maanges the policy of your pipeline a concurrent approach or multi-threading approach I will just say that I'm thinking about the hardware here and the worst case scenario, and I have tested this 2 paradigms myself, the async paradigm is a winner at the point that I don't get why people 90% of the time talk about concurrency when they wont to speed up things or make a good use of their resources. I have tested multi-threaded programs and async program on an old machine with an Intel quad-core that doesn't offer a memory controller inside the CPU, the memory is managed entirely by the motherboard, well in this case performances are horrible with a multi-threaded application, even a relatively low number of threads like 3-4-5 can be a problem, the application is unresponsive and is just slow and unpleasant. A good async approach is, on the other hand, probably not faster but it's not worst either, my application just waits for the result and doesn't hangs, it's responsive and there is a much better scaling going on. I have also discovered that a context change in the threading world it's not that cheap in real world scenario, it's infact quite expensive especially when you have more than 2 threads that need to cycle and swap among each other to be computed. On modern CPUs the situation it's not really that different, the memory controller it's integrated but my point is that an x86 CPUs is basically a serial machine and the memory controller works the same way as with the old machine with an external memory controller on the motherboard. The context switch is still a relevant cost in my application and the fact that the memory controller it's integrated or that the newer CPU have more than 2 core it's not bargain for me. For what i have experienced the concurrent approach is good in theory but not that good in practice, with the memory model imposed by the hardware, it's hard to make a good use of this paradigm, also it introduces a lot of issues ranging from the use of my data structures to the join of multiple threads. Also both paradigms do not offer any security abut when the task or the job will be done in a certain point in time, making them really similar from a functional point of view. According to the X86 memory model, why the majority of people suggest to use concurrency with C++ and not just an async aproach ? Also why not considering the worst case scenario of a computer where the context switch is probably more expensive than the computation itself ?

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• Is it unusual for a small company (15 developers) not to use managed source/version control?

  - by LordScree

  It's not really a technical question, but there are several other questions here about source control and best practice. The company I work for (which will remain anonymous) uses a network share to host its source code and released code. It's the responsibility of the developer or manager to manually move source code to the correct folder depending on whether it's been released and what version it is and stuff. We have various spreadsheets dotted around where we record file names and versions and what's changed, and some teams also put details of different versions at the top of each file. Each team (2-3 teams) seems to do this differently within the company. As you can imagine, it's an organised mess - organised, because the "right people" know where their stuff is, but a mess because it's all different and it relies on people remembering what to do at any one time. One good thing is that everything is backed up on a nightly basis and kept indefinitely, so if mistakes are made, snapshots can be recovered. I've been trying to push for some kind of managed source control for a while, but I can't seem to get enough support for it within the company. My main arguments are: We're currently vulnerable; at any point someone could forget to do one of the many release actions we have to do, which could mean whole versions are not stored correctly. It could take hours or even days to piece a version back together if necessary We're developing new features along with bug fixes, and often have to delay the release of one or the other because some work has not been completed yet. We also have to force customers to take versions that include new features even if they just want a bug fix, because there's only really one version we're all working on We're experiencing problems with Visual Studio because multiple developers are using the same projects at the same time (not the same files, but it's still causing problems) There are only 15 developers, but we all do stuff differently; wouldn't it be better to have a standard company-wide approach we all have to follow? My questions are: Is it normal for a group of this size not to have source control? I have so far been given only vague reasons for not having source control - what reasons would you suggest could be valid for not implementing source control, given the information above? Are there any more reasons for source control that I could add to my arsenal? I'm asking mainly to get a feel for why I have had so much resistance, so please answer honestly. I'll give the answer to the person I believe has taken the most balanced approach and has answered all three questions. Thanks in advance

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• "Collection Wrapper" pattern - is this common?

  - by Prog

  A different question of mine had to do with encapsulating member data structures inside classes. In order to understand this question better please read that question and look at the approach discussed. One of the guys who answered that question said that the approach is good, but if I understood him correctly - he said that there should be a class existing just for the purpose of wrapping the collection, instead of an ordinary class offering a number of public methods just to access the member collection. For example, instead of this: class SomeClass{ // downright exposing the concrete collection. Things[] someCollection; // other stuff omitted Thing[] getCollection(){return someCollection;} } Or this: class SomeClass{ // encapsulating the collection, but inflating the class' public interface. Thing[] someCollection; // class functionality omitted. public Thing getThing(int index){ return someCollection[index]; } public int getSize(){ return someCollection.length; } public void setThing(int index, Thing thing){ someCollection[index] = thing; } public void removeThing(int index){ someCollection[index] = null; } } We'll have this: // encapsulating the collection - in a different class, dedicated to this. class SomeClass{ CollectionWrapper someCollection; CollectionWrapper getCollection(){return someCollection;} } class CollectionWrapper{ Thing[] someCollection; public Thing getThing(int index){ return someCollection[index]; } public int getSize(){ return someCollection.length; } public void setThing(int index, Thing thing){ someCollection[index] = thing; } public void removeThing(int index){ someCollection[index] = null; } } This way, the inner data structure in SomeClass can change without affecting client code, and without forcing SomeClass to offer a lot of public methods just to access the inner collection. CollectionWrapper does this instead. E.g. if the collection changes from an array to a List, the internal implementation of CollectionWrapper changes, but client code stays the same. Also, the CollectionWrapper can hide certain things from the client code - from example, it can disallow mutation to the collection by not having the methods setThing and removeThing. This approach to decoupling client code from the concrete data structure seems IMHO pretty good. Is this approach common? What are it's downfalls? Is this used in practice?

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• Apache2 with SSL and mod_jk on SUSE Linux Enterprise | Apache always starts SSL disabled

  - by Shaakunthala

  I have installed Apache2 (with mod_ssl enabled) on SUSE Linux Enterprise Server 11 (x86_64) (patchlevel 1), using YaST. Once installed, I tested whether everything works fine so far. SSL also worked fine. Just 'apache2ctl start' was enough to make everything working. Then I installed mod_jk and applied the following configuration changes to make it work. /etc/sysconfig/apache2 (added JK module) APACHE_MODULES="... ... ... ... ...jk" /etc/apache2/httpd.conf (included mod_jk.conf) Include /etc/apache2/mod_jk.conf /etc/apache2/mod_jk.conf (new file) JkLogFile /var/log/apache2/mod_jk.log JkWorkersFile /etc/apache2/mod_jk/workers.properties JkShmFile /etc/apache2/mod_jk/mod_jk.shm # Set the jk log level [debug/error/info] JkLogLevel info # Select the timestamp log format JkLogStampFormat "[%a %b %d %H:%M:%S %Y] " mod_jk.log & mod_jk.shm files were also created. /etc/apache2/mod_jk/workers.properties (new file) worker.list=jira worker.jira.type=ajp13 worker.jira.host=127.0.0.1 worker.jira.port=8009 Once everything is done, I've restarted Apache using the following command, apache2ctl restart Then I observed that SSL is not working. When checked with telnet, I observed that port 443 is not open. In listen.conf, if I specify port 443 bypassing 'IfDefine' and 'IfModule' conditions, then SSL works properly. This is likely the 'SSL' flag is not passed to Apache. I did not make this a persistent change as I thought it might not be the correct practice. I checked /etc/sysconfig/apache2 to see if this has been altered, but it is there. Although this flag is enabled, Apache won't start with SSL support. APACHE_SERVER_FLAGS="SSL" Finally, I had to start Apache using the following command, apache2ctl -D SSL -k start And my question is, why did Apache (or apache2ctl) fail to start with SSL when I have installed and correctly configured mod_jk, and no other configuration changes were applied? Have I missed anything? Thanks in advance. -- Shaakunthala

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• Cisco AnyConnect on IOS 12.4(20)T

  - by natacado

  There are plenty of tutorials on setting up AnyConnect on an ASA unit, and a handful of links noting that IOS 12.4(15) and later support AnyConnect, but I can't seem to find any good documentation about how to setup AnyConnect on IOS; most tutorials assume you only want a clientless VPN on IOS. the best I've found is this document on Cisco's site, but it's not working for me in practice - see below. This is all on a Cisco 881W: router#show version | include Version Cisco IOS Software, C880 Software (C880DATA-UNIVERSALK9-M), Version 12.4(20)T1, RELEASE SOFTWARE (fc3) ROM: System Bootstrap, Version 12.4(15r)XZ2, RELEASE SOFTWARE (fc1) The old SSL VPN Client seems to install just fine: router#show webvpn install status svc SSLVPN Package SSL-VPN-Client version installed: CISCO STC win2k+ 1.0.0 1,1,4,176 Thu 08/16/2007 12:37:00.43 However, when I install the AnyConnect client, after authenticating it hangs for a while during the self-update process, and stops with an error that the "AnyConnect package unavailable or corrupted." When I try to install the AnyConnect package on the router, I'm told that it's an invalid archive: router(config)#webvpn install svc flash:/webvpn/anyconnect-win-2.3.2016-k9.pkg SSLVPN Package SSL-VPN-Client (seq:2): installed Error: Invalid Archive Does anyone have a good sample on how to get the 2.x AnyConnect clients working with a Cisco device running IOS?

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• Useful software for netbook?

  - by Moayad Mardini

  I'm looking for recommendations of good software that are particularly useful for netbooks. Software that run great on small screens and low CPU/RAM requirments. I'll start off with the following : Operating Systems: Ubuntu Netbook Remix. Easy Peasy: A fork of Ubuntu Netbook Remix that was once called UBuntu EEE. It isn't just for eeePCs though. Definitely worth a look if vanilla Netbook Remix isn't cutting it. (MarkM) Damn Small Linux (Source) Windows 7: With trimming the installation or compressing the Windows directory to fit on an 8GB SSD. (Will Eddins) nLite: A utility to install a lightweight version of Windows XP without the unnecessary components (like Media Player, Internet Explorer, Outlook Express, MSN Explorer, Messenger...). Utilites: TouchFreeze: To disable the touch pad while typing (Source) InSSIDer: Not only does it make it easier to find and keep a wireless connection, but it turns a netbook into the perfect mobile tool for troubleshooting wireless networks. (phenry) AltMove: Adds more functionality to your mouse for interacting with windows. (Rob) ASUS Font Resizer Utility and other tools by ASUS, specific to ASUS Eee PC series. Internet: Run FileZilla FTP client for a small screen : You can hide a lot of FileZilla's interface parts in the View menu, even the directory trees. Go into Settings = Interface and move the message log next to the transfer queue, if you haven't hidden them both or you want to see them. Select a theme with 16x16 icons. (Source) IDEs and Text Editors: Best lightweight IDE/Text Editor: A question on Stack Overflow that has many good suggestions of IDEs and general text editors for programmers. What’s a good linux C/C++ IDE for a low-res screen?: IDEs for Linux-powered netbooks. Online tools: Dropbox: Since the Netbook has limited disk space, you would like to use Cloud Apps like Dropbox and Ubuntu One so that you don't run out of space especially if you are on a holiday. Later when you go back to your desktop with big hard disk,you can take out the files from your dropbox repo. (Manish Sinha) Google products: like Docs, Calendar and Reader (aviraldg) Web sites and software lists: Netbookfiles.com: Netbook specific software downloads. Software Apps to Maximise your Netbook Battery Power: Netbooks are known for their portability. Not only are they small and lightweight but with their increased power efficiency, batteries can last much longer than conventional laptops. This also means you no longer have to carry a power adapter with you! Several brands emphasis the longevity of the battery as a strong selling point, and for those people who travel a lot, it sure is. Free Must-Have Netbook Apps: Finding software for netbooks can present challenges due to limited hard drive space, processor power, RAM, and screen real-estate. That doesn't mean you have to do without essential programs. The apps below cover all the bases -- entertainment, productivity, security, and communication -- without compromising on performance or usability. Best of all, they're free! Useful Netbook Software: With short battery lives and small resolution screens Netbooks, unlike many other computers on the market, could so with some specific software for their use. Now, not all of those I’ve found are specifically designed for Netbooks, but all are relevant. And they’re designed for Windows XP. The question is community wiki, so feel free to edit it. Updated, thank you all for suggestions.

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• IP address spoofing using Source Routing

  - by iamrohitbanga

  With IP options we can specify the route we want an IP packet to take while connecting to a server. If we know that a particular server provides some extra functionality based on the IP address can we not utilize this by spoofing an IP packet so that the source IP address is the privileged IP address and one of the hosts on the Source Routing is our own. So if the privileged IP address is x1 and server IP address is x2 and my own IP address is x3. I send a packet from x1 to x2 which is supposed to pass through x3. x1 does not actually send the packet. It is just that x2 thinks the packet came from x1 via x3. Now in response if x2 uses the same routing policy (as a matter of courtesy to x1) then all packets would be received by x3. Will the destination typically use the same IP address sequences as specified in the routing header so that packets coming from the server pass through my IP where I can get the required information? Can we not spoof a TCP connection in the above case? Is this attack used in practice?

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• nginx subdomains improperly act like wildcard?

  - by binjured

  I have an odd problem with nginx subdomains. First, my configuration: server { listen 443 ssl; server_name secure.example.com; ssl_certificate example.crt; ssl_certificate_key example.key; keepalive_timeout 70; location / { fastcgi_pass 127.0.0.1:8000; ... } } server { listen 80; server_name example.com www.example.com; location / { fastcgi_pass 127.0.0.1:8000; ... } } The idea being that I have a secure domain, secure.example.com and a normal domain, example.com. In practice, I can go to https://example.com and http://secure.example.com. I worked around the second issue with an intermediary server: server { listen 80; server_name secure.example.com; rewrite ^(.*) https://secure.example.com$1 permanent; } But this is not an optimal solution and I'd have to create another one to redirect https on the tld to the subdomain. I feel like I must be doing something wrong if I need multiple servers like that. Why does https://example.com work when there is no server listening on 443 there? Shouldn't it just fail to connect? I'm rather confused.

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• How to setup linux permissions for the WWW folder?

  - by Xeoncross

  Updated Summery The /var/www directory is owned by root:root which means that no one can use it and it's entirely useless. Since we all want a web server that actually works (and no-one should be logging in as "root"), then we need to fix this. Only two entities need access. PHP/Perl/Ruby/Python all need access to the folders and files since they create many of them (i.e. /uploads/). These scripting languages should be running under nginx or apache (or even some other thing like FastCGI for PHP). The developers How do they get access? I know that someone, somewhere has done this before. With however-many billions of websites out there you would think that there would be more information on this topic. I know that 777 is full read/write/execute permission for owner/group/other. So this doesn't seem to be needed as it leaves random users full permissions. What permissions are need to be used on /var/www so that... Source control like git or svn Users in a group like "websites" (or even added to "www-data") Servers like apache or lighthttpd And PHP/Perl/Ruby can all read, create, and run files (and directories) there? If I'm correct, Ruby and PHP scripts are not "executed" directly - but passed to an interpreter. So there is no need for execute permission on files in /var/www...? Therefore, it seems like the correct permission would be chmod -R 1660 which would make all files shareable by these four entities all files non-executable by mistake block everyone else from the directory entirely set the permission mode to "sticky" for all future files Is this correct? Update: I just realized that files and directories might need different permissions - I was talking about files above so i'm not sure what the directory permissions would need to be. Update 2: The folder structure of /var/www changes drastically as one of the four entities above are always adding (and sometimes removing) folders and sub folders many levels deep. They also create and remove files that the other 3 entities might need read/write access to. Therefore, the permissions need to do the four things above for both files and directories. Since non of them should need execute permission (see question about ruby/php above) I would assume that rw-rw-r-- permission would be all that is needed and completely safe since these four entities are run by trusted personal (see #2) and all other users on the system only have read access. Update 3: This is for personal development machines and private company servers. No random "web customers" like a shared host. Update 4: This article by slicehost seems to be the best at explaining what is needed to setup permissions for your www folder. However, I'm not sure what user or group apache/nginx with PHP OR svn/git run as and how to change them. Update 5: I have (I think) finally found a way to get this all to work (answer below). However, I don't know if this is the correct and SECURE way to do this. Therefore I have started a bounty. The person that has the best method of securing and managing the www directory wins.

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• run script as another user from a root script with no tty stdin

  - by viktor tron

  Using CentOs, I want to run a script as user 'training' as a system service. I use daemontools to monitor the process, which needs a launcher script that is run as root and has no tty standard in. Below I give my four different attempts which all fail. : #!/bin/bash exec >> /var/log/training_service.log 2>&1 setuidgid training training_command This last line is not good enough since for training_command, we need environment for trqaining user to be set. : su - training -c 'training_command' This looks like it (http://serverfault.com/questions/44400/run-a-shell-script-as-a-different-user) but gives 'standard in must be tty' as su making sure tty is present to potentially accept password. I know I could make this disappear by modifying /etc/sudoers (a la http://superuser.com/questions/119376/bash-su-script-giving-an-error-standard-in-must-be-a-tty) but i am reluctant and unsure of consequences. : runuser - training -c 'training_command' This one gives runuser: cannot set groups: Connection refused. I found no sense or resolution to this error. : ssh -p100 training@localhost 'source $HOME/.bashrc; training_command' This one is more of a joke to show desparation. Even this one fails with Host key verification failed. (the host key IS in known_hosts, etc). Note: all of 2,3,4 work as they should if I run the wrapper script from a root shell. problems only occur if the system service monitor (daemontools) launches it (no tty terminal I guess). I am stuck. Is this something so hard to achieve? I appreciate all insight and guidance to best practice. (this has also been posted on superuser: http://superuser.com/questions/434235/script-calling-script-as-other-user)

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• Outgrew MongoDB … now what?

  - by samsmith

  We dump debug and transaction logs into mongodb. We really like mongodb because: Blazing insert perf document oriented Ability to let the engine drop inserts when needed for performance But there is this big problem with mongodb: The index must fit in physical RAM. In practice, this limits us to 80-150gb of raw data (we currently run on a system with 16gb RAM). Sooooo, for us to have 500gb or a tb of data, we would need 50gb or 80gb of RAM. Yes, I know this is possible. We can add servers and use mongo sharding. We can buy a special server box that can take 100 or 200 gb of RAM, but this is the tail wagging the dog! We could spend boucoup $$$ on hardware to run FOSS, when SQL Server Express can handle WAY more data on WAY less hardware than Mongo (SQL Server does not meet our architectural desires, or we would use it!) We are not going to spend huge $ on hardware here, because it is necessary only because of the Mongo architecture, not because of the inherent processing/storage needs. (And sharding? Please! Cost aside, who needs the ongoing complexity of three, five, or more servers to manage a relatively small load?) Bottom line: MongoDB is FOSS, but we gotta spend $$$$$$$ on hardware to run it? We sould rather buy commercial SW! I am sure we are not the first to hit this issue, so we ask the community: Where do we go next? (We already run Mongo v2) Thanks!!

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