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• MapReduce

  - by kaleidoscope

  MapReduce is a programming model and an associated implementation for processing and generating large data sets. Users specify a map function that processes a key/value pair to generate a set of  intermediate key/value pairs, and a reduce function that merges all intermediate values associated with the same intermediate key. Many real world tasks are expressible in this model, as shown in the paper. Programs written in this functional style are automatically parallelized and executed on a large cluster of commodity machines. The run-time system takes care of the details of partitioning the input data,  scheduling the program's execution across a set of machines, handling machine failures, and managing the required inter-machine communication. This allows programmers without any experience with parallel and distributed systems to easily utilize the resources of a large distributed system. Example: A process to count the appearances of each different word in a set of documents void map(String name, String document):   // name: document name   // document: document contents   for each word w in document:     EmitIntermediate(w, 1); void reduce(String word, Iterator partialCounts):   // word: a word   // partialCounts: a list of aggregated partial counts   int result = 0;   for each pc in partialCounts:     result += ParseInt(pc);   Emit(result); Here, each document is split in words, and each word is counted initially with a "1" value by the Map function, using the word as the result key. The framework puts together all the pairs with the same key and feeds them to the same call to Reduce, thus this function just needs to sum all of its input values to find the total appearances of that word.   Sarang, K

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• CodePlex Daily Summary for Saturday, September 15, 2012

  CodePlex Daily Summary for Saturday, September 15, 2012Popular ReleasesMCEBuddy 2.x: MCEBuddy 2.2.15: Changelog for 2.2.15 (32bit and 64bit) 1. Added support for %originalfilepath% to get the source file full path. Used for custom commands only. 2. Added support for better parsing of Media Portal XML files to extract ShowName and Episode Name and download additional details from TVDB (like Season No, Episode No etc). 3. Added support for TVDB seriesID in metadata 4. Added support for eMail non blocking UI testCrashReporter.NET : Exception reporting library for C# and VB.NET: CrashReporter.NET 1.2: *Added html mail format which shows hierarchical exception report for better understanding.VCC: Latest build, v2.3.00914.0: Automatic drop of latest buildScarlet Road: Scarlet Road Test Build 007: Playable game. Includes source.DotNetNuke Search Engine Sitemaps Provider: Version 02.00.00: New release of the Search Engine Sitemap Providers New version - not backwards compatible with 1.x versions New sandboxing to prevent exceptions in module providers interfering with main provider Now installable using the Host->Extensions page New sitemaps available for Active Forums and Ventrian Property Agent Now derived from DotNetNuke Provider base for better framework integration DotNetNuke minimum compatibility raised to DNN 5.2, .NET to 3.5PDF Viewer Web part: PDF Viewer Web Part: PDF Viewer Web PartChris on SharePoint Solutions: View Grid Banding - v1.0: Initial release of the View Creation and Management Page Column Selector Banding solution.$linq - A Javascript LINQ library: Version 1.0: Version 1.0 Initial releasePowerConverter: PowerConverter Beta: This is the first release of PowerConverter. Allows for converting PE code to Power code.NetView Control for Microsoft Access: DevVersion 19852 - More Databinding and Resizing: NetView Renamed event GotFocus to Clicked Added events Clicked/DoubleClicked Added event BackgroundDoubleClicked Changed nomenclature for world coordinates to (Position1, Position2)|Extent1xExtent2 Renamed Locked -> Readonly Added properties Minimum1/Maximum1 and Minimum2/Maximum2 Removed NetView.DeviceDefinitionArea, obsolete properties Support for resizing Added properties BackColor and BorderColor NetView Properties form added binding field for BusinessId propagate erro...Runtime Dynamic Data Model Builder: Main Library Version 1.0.0.0: Main Library Version 1.0.0.0Microsoft Ajax Minifier: Microsoft Ajax Minifier 4.67: Fix issue #18629 - incorrectly handling null characters in string literals and not throwing an error when outside string literals. update for Issue #18600 - forgot to make the ///#DEBUG= directive also set a known-global for the given debug namespace. removed the kill-switch for disregarding preprocessor define-comments (///#IF and the like) and created a separate CodeSettings.IgnorePreprocessorDefines property for those who really need to turn that off. Some people had been setting -kil...Lakana - WPF Framework: Lakana V2: Lakana V2 contains : - Lakana WPF Forms (with sample project) - Lakana WPF Navigation (with sample project)Microsoft SQL Server Product Samples: Database: OData QueryFeed workflow activity: The OData QueryFeed sample activity shows how to create a workflow activity that consumes an OData resource, and renders entity properties in a Microsoft Excel 2010 worksheet or Microsoft Word 2010 document. Using the sample QueryFeed activity, you can consume any OData resource. The sample activity uses LINQ to project OData metadata into activity designer expression items. By setting activity expressions, a fully qualified OData query string is constructed consisting of Resource, Filter, Or...Arduino for Visual Studio: Arduino 1.x for Visual Studio 2012, 2010 and 2008: Register for the visualmicro.com forum for more news and updates Version 1209.10 includes support for VS2012 and minor fixes for the Arduino debugger beta test team. Version 1208.19 is considered stable for visual studio 2010 and 2008. If you are upgrading from an older release of Visual Micro and encounter a problem then uninstall "Visual Micro for Arduino" using "Control Panel>Add and Remove Programs" and then run the install again. Key Features of 1209.10 Support for Visual Studio 2...Social Network Importer for NodeXL: SocialNetImporter(v.1.5): This new version includes: - Fixed the "resource limit" bug caused by Facebook - Bug fixes To use the new graph data provider, do the following: Unzip the Zip file into the "PlugIns" folder that can be found in the NodeXL installation folder (i.e "C:\Program Files\Social Media Research Foundation\NodeXL Excel Template\PlugIns") Open NodeXL template and you can access the new importer from the "Import" menuAcDown????? - AcDown Downloader Framework: AcDown????? v4.1: ??●AcDown??????????、??、??、???????。????，????，?????????????????????????。???????????Acfun、????(Bilibili)、??、??、YouTube、??、???、??????、SF????、????????????。 ●??????AcPlay?????，??????、????????????????。 ● AcDown??????????????????，????????????????????????????。 ● AcDown???????C#??，????.NET Framework 2.0??。?????"Acfun?????"。 ????32??64? Windows XP/Vista/7/8 ???? 32??64? ???Linux ????(1)????????Windows XP???,?????????.NET Framework 2.0???(x86)，?????"?????????"??? (2)???????????Linux???，????????Mono?? ??...Move Mouse: Move Mouse 2.5.2: FIXED - Minor fixes and improvements.MVC Controls Toolkit: Mvc Controls Toolkit 2.3: Added The new release is compatible with Mvc4 RTM. Support for handling Time Zones in dates. Specifically added helper methods to convert to UTC or local time all DateTimes contained in a model received by a controller, and helper methods to handle date only fileds. This together with a detailed documentation on how TimeZones are handled in all situations by the Asp.net Mvc framework, will contribute to mitigate the nightmare of dates and timezones. Multiple Templates, and more options to...DNN Metro7 style Skin package: Metro7 style Skin for DotNetNuke 06.02.00: Maintenance Release Changes on Metro7 06.02.00 Fixed width and height on the jQuery popup for the Editor. Navigation Provider changed to DDR menu Added menu files and scripts Changed skins to Doctype HTML Changed manifest to dnn6 manifest file Changed License to HTML view Fixed issue on Metro7/PinkTitle.ascx with double registering of the Actions Changed source folder structure and start folder, so the project works with the default DNN structure on developing Added VS 20...New ProjectsBizTalk Zombie Management: A powerful tool to handle zombie. As a service you can monitor all zombie instance and process them. For the moment only file is supporting.bxkw8: oooooooooooh long johnsonCellularSolver: The main idea of a this project - create cellular automation (CA) simulation system. We try to reduce ODE/PDE/Integral Equations models to CA-modelEAWebService: EAWebService is web service that executes parallel evolutionary algorithm. Finite Element Method Samples with C#: Finite Element Method Samples with C# Game Jolt C# Trophy API: The Game Jolt Trophy API provides dotNET developers with access to the Game Jolt services including Trophies, High Scores, Data Storage and many more.GNSystem: GNSystem is a simple (yet, no so elegant) Web-Application which contains a Forum system and a CMS\Blog system. GNSystem is written in ASP.Net MVC 4 using C#Hospital Management System (HMS): HMS is a software basically working to make the hospital management much easier and fasterInfinity - WPF.MVC: Framework for WPF/SL/WinFormsKindle: Kindle PublisherMetroCash: A personal finance management programmetroCIS: metroCIS - Eine open-source Anwendung für Windows8 Verwalte dein Studium an der FH Technikum Wien mit dieser App und erleichter dir damit dein Studentenleben.MTAC: MTAC, for My Tfs Administration Center, is a centralized administration tool for TFSMyStart: Create an Open Source implementation of the Windows Start Menu (based initially on Windows 7), to be used on Windows 8.NLite Data Framework: NLite Linq ORM frameworkPDF Viewer Web part: Here now presenting PDF Viewer web part solution with code. Project91405: dfgfdgfdrProject91407: awqwqProject91407M: 111Purchasesales(??????): a simple Sales Manage Project.QueryOver Specification: A simple implementation of the Specification Pattern using NHibernate QueryOver.Shopping Analytics: Esta aplicacion muestra como aprovechar diversas caracteristicas de la plataforma Windows Phone.simbo: Simbo is a simple, fun app for sharing small notes with friends where many of the concepts in your note can be represented by a symbols.SISLOG: El sistema de logística SISLOG es un software que cual será capaz de automatizar y optimizar los procesos que se llevan a cabo en el área de logística.SQL Server Scripts - A RSSUG CodePlex Project: The SQL Server Scripts project is dedicated to supplying high quality scripts to help with the maintenance and development of SQL Server in every environment.Talqum.League: Talqum.League is a League organisator and statistics app.The Pratoriate Foundation: used for all software dev projects for the non profit Pratoriate Foundation.

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• Ninject/DI: How to correctly pass initialisation data to injected type at runtime

  - by MrLane

  I have the following two classes: public class StoreService : IStoreService { private IEmailService _emailService; public StoreService(IEmailService emailService) { _emailService = emailService; } } public class EmailService : IEmailService { } Using Ninject I can set up bindings no problem to get it to inject a concrete implementation of IEmailService into the StoreService constructor. StoreService is actually injected into the code behind of an ASP.NET WebForm as so: [Ninject.Inject] public IStoreService StoreService { get; set; } But now I need to change EmailService to accept an object that contains SMTP related settings (that are pulled from the ApplicationSettings of the Web.config). So I changed EmailService to now look like this: public class EmailService : IEmailService { private SMTPSettings _smtpSettings; public void SetSMTPSettings(SMTPSettings smtpSettings) { _smtpSettings = smtpSettings; } } Setting SMTPSettings in this way also requires it to be passed into StoreService (via another public method). This has to be done in the Page_Load method in the WebForms code behind (I only have access to the Settings class in the UI layer). With manual/poor mans DI I could pass SMTPSettings directly into the constructor of EmailService and then inject EmailService into the StoreService constructor. With Ninject I don't have access to the instances of injected types outside of the objects they are injected to, so I have to set their data AFTER Ninject has already injected them via a separate public setter method. This to me seems wrong. How should I really be solving this scenario?

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• Algorithms or patterns for a linked question and answer cost calculator

  - by kmc

  I've been asked to build an online calculator in PHP (and the Laravel framework). It will take the answers to a series of questions to estimate the cost of a home extension. For example, a couple of questions may be: What is the lie of your property? Flat, slightly inclined, heavily inclined. (these suggestive values could have specific values in the underlying calculator like, 0 degrees, 5 degrees, 10 degrees. What is your current flooring system? Wooden, or concrete? These would then impact the results of other questions. Once the size of the extension has been input, the lie of the land will affect how much site works will cost, and how much rubbish collection will cost. The second question will impact the cost of the extensions flooring, as stumping and laying floorboards is a different cost to laying foundations and a concrete slab. It will also influence what heating and cooling systems are available in the calculator. So it's VERY interlinked. The answer to any question can influence the options of other questions, and the end result. I'm having trouble figuring out an approach to this that will allow new options and questions to be plugged in at a later stage without having things too coupled. The Observer pattern, or Laravel's events may be handy, but currently the sheer breadth of the calculator has me struggling to gather my thoughts and see a sensible implementation. Are there any patterns or OO approaches that may help? Thanks!

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• Synchronous vs. asynchronous for publish subscribe communication between JavaScript objects

  - by natlee75

  I implemented the publish subscribe pattern in a JavaScript module to be used by entirely client-side oriented JavaScript objects. This module has nothing to do with client-server communications in any way, shape or form. My question is whether it's better for the publish method in such a module to be synchronous or asynchronous, and why. As a very simplified example let's say I'm building a custom UI for an HTML5 video player widget: One of my modules is the "video" module that contains the VIDEO element and handles the various features and events associated with that element. This would probably have a namespace something like "widgets.player.video." Another is the "controls" module that has the various buttons - play, pause, volume, scrub, fullscreen, etc. This might have a namespace along the lines of "widgets.player.controls." These two modules are children of a parent "player" module ("widgets.player" ??), and as such would have no inherent knowledge of each other when instantiated as children of the "player" object. The "controls" elements would obviously need to be able to effect some changes on the video (click "Play" and the video should play), and vice versa (video's "timeUpdate" event fires and the visual display of the current time in the controls should update). I could tightly couple these modules and pass references to each other, but I'd rather take a more loosely coupled approach by setting up a pubsub type module that both can subscribe to and publish from. SO (thanks for bearing with me) in this kind of a scenario is there an advantage one way or another for synchronous publication versus asynchronous publication? I've seen some solutions posted online that allow for either/or with a boolean flag whereas others automatically do it asynchronously. I haven't personally seen an implementation that just automatically goes with synchronous publication... is this because there's no advantage to it? I know that I can accomplish this with features provided by jQuery, but it seems that there may be too much overhead involved here. The publish subscribe pattern can be implemented with relatively lightweight code designed specifically for this particular purpose so I'd rather go with that then a more general purpose eventing system like jQuery's (which I'll use for more general eventing needs :-).

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• Observable Adapter

  - by Roman Schindlauer

  .NET 4.0 introduced a pair of interfaces, IObservable<T> and IObserver<T>, supporting subscriptions to and notifications for push-based sequences. In combination with Reactive Extensions (Rx), these interfaces provide a convenient and uniform way of describing event sources and sinks in .NET. The StreamInsight CTP refresh in November 2009 included an Observable adapter supporting “reactive” event inputs and outputs.   While we continue to believe it enables an important programming model, the Observable adapter was not included in the final (RTM) release of Microsoft StreamInsight 1.0. The release takes a dependency on .NET 3.5 but for timing reasons could not take a dependency on .NET 4.0. Shipping a separate copy of the observable interfaces in StreamInsight – as we did in the CTP refresh – was not a viable option in the RTM release.   Within the next months, we will be shipping another preview of the Observable adapter that targets .NET 4.0. We look forward to gathering your feedback on the new adapter design! We plan to include the Observable adapter implementation into the product in a future release of Microsoft StreamInsight. Share this post: email it! | bookmark it! | digg it! | reddit! | kick it! | live it!

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• Should I use an interface when methods are only similar?

  - by Joshua Harris

  I was posed with the idea of creating an object that checks if a point will collide with a line: public class PointAndLineSegmentCollisionDetector { public void Collides(Point p, LineSegment s) { // ... } } This made me think that if I decided to create a Box object, then I would need a PointAndBoxCollisionDetector and a LineSegmentAndBoxCollisionDetector. I might even realize that I should have a BoxAndBoxCollisionDetector and a LineSegmentAndLineSegmentCollisionDetector. And, when I add new objects that can collide I would need to add even more of these. But, they all have a Collides method, so everything I learned about abstraction is telling me, "Make an interface." public interface CollisionDetector { public void Collides(Spatial s1, Spatial s2); } But now I have a function that only detects some abstract class or interface that is used by Point, LineSegment, Box, etc.. So if I did this then each implementation would have to to a type check to make sure that the types are the appropriate type because the collision algorithm is different for each different type match up. Another solution could be this: public class CollisionDetector { public void Collides(Point p, LineSegment s) { ... } public void Collides(LineSegment s, Box b) { ... } public void Collides(Point p, Box b) { ... } // ... } But, this could end up being a huge class that seems unwieldy, although it would have simplicity in that it is only a bunch of Collide methods. This is similar to C#'s Convert class. Which is nice because it is large, but it is simple to understand how it works. This seems to be the better solution, but I thought I should open it for discussion as a wiki to get other opinions.

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• Price Drop for Processor based License on Exalytics

  - by Mike.Hallett(at)Oracle-BI&EPM

  ·       33% reduction in the list `per processor` license pricing for the Oracle BI Foundation Suite ·       New capacity-based licensing which allows customers to think big & start small, significantly lowering the entry price point for an Exalytics. Oracle BI Software List Price changes In response to new powerful platforms like the in-memory Oracle Exalytics with 40 cpu cores (counted under Oracle pricing policy as 20 “processors”), the list price of “Oracle BI Foundation Suite” (BIFS) is reduced by 33% from $450K per processor to $300K per processor. Capacity-based licensing on Exalytics (Trusted Partitions) “Capacity-based pricing” for the BIFS, Endeca, Essbase and Times Ten for Exalytics software is now available for Exalytics systems. This is delivered using “Oracle VM” (OVM).  We still ship a full Exalytics machine to all customers, but they may choose to only use and license a subset of the processors installed in the machine.   Customers can license Exalytics software in units of 5 “processors”: 5, 10, 15 or the full capacity 20.   As the customer’s implementation and workload increases, it is a simple matter to license additional processors and, using OVM, make them available to the BI or EPM application. Endeca Information Discovery now available on Exalytics Oracle has also announced the certification of “Oracle Endeca Information Discovery” (EID) on the Exalytics machine.    EID can be licensed alone or in combination with the BIFS & Times Ten for an Exalytics stack, and also participates in the capacity based pricing outlined above.   The Exalytics hardware is the perfect platform for EID, and provides superb power and performance for this in-memory hybrid text-search-analytics.   For more information : Oracle Price lists Oracle Partitioning Policy Discussion by Mark Rittman (Rittman Mead Consulting ltd.) on Oracle Trusted Partitions for Oracle Engineered Systems, Oracle Exalytics and Updated BI Foundation Pricing.

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• Website Ethics / legal issues, image copyrights

  - by RailsN00b

  Ignoring the technical implementation of a website for a second, assume a website that is similar to twitter but with pictures. A user say something and puts a picture of whatever they said. As the nature of the internet, the images will most likely not be his/hers image. There are 2 options that I see for dealing with this: 1. The user will post a URL of the picture and the website will pull the picture from that URL everytime someone enters that page 2. The website will save the image in its own database of images and display the image to the visitors 'locally' The problem with option #1, while it saved storage, I see an issue with 'stealing' other websites bandwidth and if my website has many many visitors it could cost the image-hosting websites a lot and possible even crash it if the server can't handle the load. The problem with opion #2, while it saves the load to other websites, it practically takes pictures that could have copyright on them. Which option is better to implement in terms of legal issues and ethics? When do I need to contact another website to request permission to use the images from that site? Does anyone really care about that anymore. Where can I read about this?

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• sqlplus: Running "set lines" and "set pagesize" automatially

  - by katsumii

  This is a followup to my previous entry. Using the full tty real estate with sqlplus (INOUE Katsumi @ Tokyo) 'rlwrap' is widely used for adding 'sqlplus' the history function and command line editing. Here's another but again kludgy implementation. First this is the alias. alias sqlplus="rlwrap -z ~/sqlplus.filter sqlplus" And this is the file content. #!/usr/bin/env perl use lib ($ENV{RLWRAP_FILTERDIR} or "."); use RlwrapFilter; use POSIX qw(:signal_h); use strict; my $filter = new RlwrapFilter; $filter -> prompt_handler(\&prompt); sigprocmask(SIG_UNBLOCK, POSIX::SigSet->new(28)); $SIG{WINCH} = 'winchHandler'; $filter -> run; sub winchHandler { $filter -> input_handler(\&input); sigprocmask(SIG_UNBLOCK, POSIX::SigSet->new(28)); $SIG{WINCH} = 'winchHandler'; $filter -> run; } sub input { $filter -> input_handler(undef); return `resize |sed -n "1s/COLUMNS=/set linesize /p;2s/LINES=/set pagesize /p"` . $_; } sub prompt { if ($_ =~ "SQL> ") { $filter -> input_handler(\&input); $filter -> prompt_handler(undef); } return $_; } I hope I can compare these 2 implementations after testing more and getting some feedbacks.

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• Can JSON be made easily and safely editable by the non-technical Excel crowd?

  - by glitch

  I'm looking for a data storage format that's very intuitive and easy to edit. It should be ideally targeted towards the same crowd as Excel. At the same time I would like the data structure to be a tree. Ideally this would be JSON, since it offers both the tree aspect and allows for more interesting constructs like arrays. That and parsing libraries for JSON are ubiquitous, so I don't have to reinvent the wheel. The problem is that, at least with a non-specialized text editor, JSON is a giant pain to edit for a non-technical user. I'm thinking along the lines of someone who might have used Excel in the past, but never a real text editor. Someone who might not be comfortable with the idea of preserving JSON syntax by hand. Are there data formats out there that would fit this profile? I'd very much prefer this to be a JSON actually, but then it would require a solid editing tool that would hide the underlying implementation from the user. Think Excel and how it abstracts CSV syntax from the user. The reason I'm looking for something like this is because the team has been working with pretty hierarchical data for a while now and we've hit the limits of how easy it is to represent in simple CSVs without having to create complex rules for how represent hierarchy semantics from each row. Any suggestions?

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• What alternative is better to diagram this scenario?

  - by Mosty Mostacho

  I was creating and discussing a class diagram with a partner of mine. To simplify things, I've modify the real domain we're working on and made up the following diagram: Basically, a company works on constructions that are quite different one from each other but are still constructions. Note I've added one field for each class but there should be many more. Now, I thought this was the way to go but my partner told me that if in the future new construction classes appear we would have to modify the Company class, which is correct. So the new proposed class diagram would be this: Now I've been wondering: Should the fact that in no place of the application will there be mixed lists of planes and bridges affect the design in any way? When we have to list only planes for a company, how are we supposed to distinguish them from the other elements in the list without checking for their class names? Related to the previous question, is it correct to assume that this type of diagram should be high-level and this is something it shouldn't matter at this stage but rather be thought and decided at implementation time? Any comment will be appreciated.

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• Moving 2d camera in the y direction

  - by Alex

  I'm developing a simple game for the iphone and am struggling to work out the best way for the camera to follow the main character. The following picture hightlights the three main components: There are 3 components to this: Circle - the main character Green line - terrain Black background The terrain is simply made from an array of points (approx 20 points per screen width). The terrain is moved in the x direction relative to the black background in order to keep the circle in its position shown. The distance to move the terrain is simply: movex = circle.position.x - terrain.position.x with a constant to fix the circle at some distance from the left of the screen. I am struggling to determine the best way to position the terrain in the y plane keep the focus in the character. I want to move the terrain in the y direction smoothly and not fix it to the position of the circle, so the circle can move in the y plane. If I take the same approach as the x positioning, the character is fixed at a point on the screen and the terrain moves. I could sample some terrain points either side of the character and produce an average, but in my implementation this was not smooth. I thought another approach might be to create a camera 'line' that is a smooth version of the terrain line and make the camerea follow this, but I'm not sure if this is the optimum solution. Any advice is much appreciated!

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• What should a developer know before building a public web site?

  - by Joel Coehoorn

  What things should a programmer implementing the technical details of a web site address before making the site public? If Jeff Atwood can forget about HttpOnly cookies, sitemaps, and cross-site request forgeries all in the same site, what important thing could I be forgetting as well? I'm thinking about this from a web developer's perspective, such that someone else is creating the actual design and content for the site. So while usability and content may be more important than the platform, you the programmer have little say in that. What you do need to worry about is that your implementation of the platform is stable, performs well, is secure, and meets any other business goals (like not cost too much, take too long to build, and rank as well with Google as the content supports). Think of this from the perspective of a developer who's done some work for intranet-type applications in a fairly trusted environment, and is about to have his first shot and putting out a potentially popular site for the entire big bad world wide web. Also: I'm looking for something more specific than just a vague "web standards" response. I mean, HTML, JavaScript, and CSS over HTTP are pretty much a given, especially when I've already specified that you're a professional web developer. So going beyond that, Which standards? In what circumstances, and why? Provide a link to the standard's specification. This question is community wiki, so please feel free to edit that answer to add links to good articles that will help explain or teach each particular point. To search in only the answers from this question, use the inquestion:this option.

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• Stacks in C++

  - by MarkPearl

  So some more basics… One of the things you will be taught at any college after conquering arrays is different derivatives of collections. Stack is one of the simplest of those and very useful… A stack is a LIFO (last in first out) data structure and has at least two basic method calls – push & pop. Push, “pushes” an item on the top of the stack. Pop, removes the top most item off the stack. Because all elements on a stack are of the same type, one can use an array to implement a stack or a linked list. With the array based approach, the first element in a stack would be the first element in the array, the second on the stack would be the second on the array, etc. One limitation with an array implementation of a stack is that unless the array is dynamic, one would have to have a preset max stack size (based on the bounds of the array). Linked lists is another approach that gets past this boundary by allowing you to dynamically grow or shrink a collection of data. Stacks have many applications… a typical computer science example would be Postfix Expression Calculator, where the LIFO principle is maintained.

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• Empty interface to combine multiple interfaces

  - by user1109519

  Suppose you have two interfaces: interface Readable { public void read(); } interface Writable { public void write(); } In some cases the implementing objects can only support one of these but in a lot of cases the implementations will support both interfaces. The people who use the interfaces will have to do something like: // can't write to it without explicit casting Readable myObject = new MyObject(); // can't read from it without explicit casting Writable myObject = new MyObject(); // tight coupling to actual implementation MyObject myObject = new MyObject(); None of these options is terribly convenient, even more so when considering that you want this as a method parameter. One solution would be to declare a wrapping interface: interface TheWholeShabam extends Readable, Writable {} But this has one specific problem: all implementations that support both Readable and Writable have to implement TheWholeShabam if they want to be compatible with people using the interface. Even though it offers nothing apart from the guaranteed presence of both interfaces. Is there a clean solution to this problem or should I go for the wrapper interface? UPDATE It is in fact often necessary to have an object that is both readable and writable so simply seperating the concerns in the arguments is not always a clean solution. UPDATE2 (extracted as answer so it's easier to comment on) UPDATE3 Please beware that the primary usecase for this is not streams (although they too must be supported). Streams make a very specific distinction between input and output and there is a clear separation of responsibilities. Rather, think of something like a bytebuffer where you need one object you can write to and read from, one object that has a very specific state attached to it. These objects exist because they are very useful for some things like asynchronous I/O, encodings,...

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• Everything has an Interface [closed]

  - by Shane

  Possible Duplicate: Do I need to use an interface when only one class will ever implement it? I am taking over a project where every single real class is implementing an Interface. The vast majority of these interfaces are implemented by a single class that share a similar name and the exact same methods (ex: MyCar and MyCarImpl). Almost no 2 classes in the project implement more than the interface that shares its name. I know the general recommendation is to code to an interface rather than an implementation, but isn't this taking it a bit too far? The system might be more flexible in that it is easier to add a new class that behaves very much like an existing class. However, it is significantly harder to parse through the code and method changes now require 2 edits instead of 1. Personally, I normally only create interfaces when there is a need for multiple classes to have the same behavior. I subscribe to YAGNI, so I don't create something unless I see a real need for it. Am I doing it all wrong or is this project going way overboard?

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• How can I improve my isometric tile-picking algorithm?

  - by Cypher

  I've spent the last few days researching isometric tile-picking algorithms (converting screen-coordinates to tile-coordinates), and have obviously found a lot of the math beyond my grasp. I have come fairly close and what I have is workable, but I would like to improve on this algorithm as it's a little off and seems to pick down and to the right of the mouse pointer. I've uploaded a video to help visualize the current implementation: http://youtu.be/EqwWcq1zuaM My isometric rendering algorithm is based on what is found at this stackoverflow question's answer, with the exception that my x and y axis' are inverted (x increased down-right, while y increased up-right). Here is where I am converting from screen to tiles: // these next few lines convert the mouse pointer position from screen // coordinates to tile-grid coordinates. cameraOffset captures the current // mouse location and takes into consideration the camera's position on screen. System.Drawing.Point cameraOffset = new System.Drawing.Point( 0, 0 ); cameraOffset.X = mouseLocation.X + (int)camera.Left; cameraOffset.Y = ( mouseLocation.Y + (int)camera.Top ); // the camera-aware mouse coordinates are then further converted in an attempt // to select only the "tile" portion of the grid tiles, instead of the entire // rectangle. this algorithm gets close, but could use improvement. mouseTileLocation.X = ( cameraOffset.X + 2 * cameraOffset.Y ) / Global.TileWidth; mouseTileLocation.Y = -( ( 2 * cameraOffset.Y - cameraOffset.X ) / Global.TileWidth ); Things to make note of: mouseLocation is a System.Drawing.Point that represents the screen coordinates of the mouse pointer. cameraOffset is the screen position of the mouse pointer that includes the position of the game camera. mouseTileLocation is a System.Drawing.Point that is supposed to represent the tile coordinates of the mouse pointer. If you check out the above link to youtube, you'll notice that the picking algorithm is off a bit. How can I improve on this?

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• With Slick, how to change the resolution during gameplay?

  - by TheLima

  I am developing a tile-based strategy game using Java and the Slick API. So far so good, but I've come to a standstill on my options menu. I have plans for the user to be able to change the resolution during gameplay (it is pretty common, after all). I can already change to fullscreen and back to windowed, this was pretty simple... //"fullScreenOption" is a checkbox-like button. if (fullScreenOption.isMouseOver(mouseX, mouseY)) { if (input.isMouseButtonDown(Input.MOUSE_LEFT_BUTTON)) { fullScreenOption.state = !fullScreenOption.state; container.setFullscreen(fullScreenOption.state); } } But the container class (Implemented by Slick, not me), contrary to my previous beliefs, does not seem to have any resolution-change functions! And that's pretty much the situation...I know it's possible, but i don't know how to do it, nor what is the class responsible! The AppGameContainer class, used on the very start of the game's initialization, is the only place with any functions for changing the display-mode that I've found so far, but it's only used at the very start, and i haven't found a way to travel back to it from my options menu. //This is my implementation of it... public static void main(String[] args) throws SlickException { AppGameContainer app = new AppGameContainer(new Main()); // app.setTargetFrameRate(60); app.setVSync(true); app.setDisplayMode(800, 600, false); app.start(); } I can define it as a static global on the Main, but it's probably a (very) bad way to do it...

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• Square game map rendered as sphere with OpenGL

  - by Roflha

  Okay so I have been trying to find a good way to do this for a while now and so far I have nothing. For a hobby project of mine I have created a finite voxel world (similar to minecraft), but as I said, mine is finite. When you reach the edge of it, you are sent to the other side. That is all working fine along with rendering the far side of the map, but I want to be able to render this grid as a sphere. Looking down from above, the world is a square. I basically want to be able to represent a portion of that square as a sphere, as if you were looking at a planet. Right now I am experimenting with taking a circular section of the map, and rendering that, but it look to flat (no curvature around the edges). My question then, is what would be the best way to add some curvature to the edges of a 2d circle to make it look like a hemisphere. However, I am not overly attached to this implementation so if somebody has some other idea for representing the square as a planet, I am all ears.

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• Should you create a class within a method?

  - by Amndeep7

  I have made a program using Java that is an implementation of this project: http://nifty.stanford.edu/2009/stone-random-art/sml/index.html. Essentially, you create a mathematical expression and, using the pixel coordinate as input, make a picture. After I initially implemented this in serial, I then implemented it in parallel due to the fact that if the picture size is too large or if the mathematical expression is too complex (especially considering the fact that I made the expression recursively), it takes a really long time. During this process, I realized that I needed two classes which implemented the Runnable interface as I had to put in parameters for the run method, which you aren't allowed to do directly. One of these classes ended up being a medium sized static inner class (not large enough to make an independent class file for it though). The other though, just needed a few parameters to determine some indexes and the size of the for loop that I was making run in parallel - here it is: class DataConversionRunnable implements Runnable { int jj, kk, w; DataConversionRunnable(int column, int matrix, int wid) { jj = column; kk = matrix; w = wid; } public void run() { for(int i = 0; i < w; i++) colorvals[kk][jj][i] = (int) ((raw[kk][jj][i] + 1.0) * 255 / 2.0); increaseCounter(); } } My question is should I make it a static inner class or can I just create it in a method? What is the general programming convention followed in this case?

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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 most mind-bending programming language? [closed]

  - by Xepoch

  From a reasonably common programming language, which do you find to be the most mind-bending? I have been listening to a lot of programming podcasts and taking some time to learn some new languages that are being considered upcoming, and important. I'm not necessarily talking about BrainFuck, but which language would you consider to be one that challenges the common programming paradigms? For me, I did some functional and logic (ex. Prolog) programming in the 90s, so can't say that I find anything special there. I am far from being an expert in it, but even today the most mind-bending programming language for me is Perl. Not because "Hello World" is hard to implement but rather there is so much lexical flexibility that some of the hardest solutions can be decomposed so poetically that I have to walk outside away from my terminal to clear my head. I'm not saying I'd likely sell a commercial software implementation, just that there is a distinct reason Perl is so (in)famous. Just look at the basic list of books on it. So, what is your mind-bending language that promotes your better programming and practices?

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• What is logical cohesion, and why is it bad or undesirable?

  - by Matt Fenwick

  From the c2wiki page on coupling & cohesion: Cohesion (interdependency within module) strength/level names : (from worse to better, high cohesion is good) Coincidental Cohesion : (Worst) Module elements are unrelated Logical Cohesion : Elements perform similar activities as selected from outside module, i.e. by a flag that selects operation to perform (see also CommandObject). i.e. body of function is one huge if-else/switch on operation flag Temporal Cohesion : operations related only by general time performed (i.e. initialization() or FatalErrorShutdown?()) Procedural Cohesion : Elements involved in different but sequential activities, each on different data (usually could be trivially split into multiple modules along linear sequence boundaries) Communicational Cohesion : unrelated operations except need same data or input Sequential Cohesion : operations on same data in significant order; output from one function is input to next (pipeline) Informational Cohesion: a module performs a number of actions, each with its own entry point, with independent code for each action, all performed on the same data structure. Essentially an implementation of an abstract data type. i.e. define structure of sales_region_table and its operators: init_table(), update_table(), print_table() Functional Cohesion : all elements contribute to a single, well-defined task, i.e. a function that performs exactly one operation get_engine_temperature(), add_sales_tax() (emphasis mine). I don't fully understand the definition of logical cohesion. My questions are: what is logical cohesion? Why does it get such a bad rap (2nd worst kind of cohesion)?

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• Need advice on framework design: how to make extending easy

  - by beginner_

  I'm creating a framework/library for a rather specific use-case (data type). It uses diverse spring components, including spring-data. The library has a set of entity classes properly set up and according service and dao layers. The main work or main benefit of the framework lies in the dao and service layer. Developers using the framework should be able to extend my entity classes to add additional fields they require. Therefore I made dao and service layer generic so it can be used by such extended entity classes. I now face an issue in the IO part of the framework. It must be able to import the according "special data type" into the database. In this part I need to create a new entity instance and hence need the actual class used. My current solution is to configure in spring a bean of the actual class used. The problem with this is that an application using the framework could only use 1 implementation of the entity (the original one from me or exactly 1 subclass but not 2 different classes of the same hierarchy. I'm looking for suggestions / desgins for solving this issue. Any ideas?

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