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• Inspiring the method of teaching. Example- C++ :)

  - by Ashwin

  A year ago I graduated with a degree in Computer Science and Engineering. Considering C++ as the first choice of programming language I have been in the process of learning C++ in many ways. At first - five years back - I had many conceptions, most of which were so abstract to me. It started when I knew almost everything about Structs in C and nothing about Classes in C++. I went through a great time experimenting them all and learning a lot. I had a hard time evaluating Procedural programming vs Object-Oriented Programming. Deciding when to choose Procedural or Object-Oriented Programming took a great deal of patience for me. I knew that I cannot underestimate any of these Programming styles... Though Procedural programming is often a better choice than simple sequential unstructured programming, when solving problems with procedural programming, we usually divide one problem into several steps in order regarded as functions. Then we call these functions one by one to get the result of the problem. When solving problems with Object Oriented Priciples we divide one problem into several classes and form the interaction between them. Evaluating these two at the beginning (as a learner) required a lot of inspiration and thoughts. Instructing to think step by step. Relative concepts to understand deeply. Intensive interests to contrast both solving in both POP and OOP. If you were ever a mentor: What ideas/methods would you teach to students in which it will Inspire them to learn a programming language (in general, computer sciences)?

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• Kids and programming: ScratchKara

  - by Mike Pagel

  Ever now and then I kept wondering how to share with my kids the excitement of creating something with your computer. Of course, today this is a bit more difficult, as they have seen 3D animation games and well-edited websites. I guess that's why they weren't all that hyped when I found my first computer model at our local recycling facilities (an 8-bit Laser VZ-200 with rubber keys). When I finally got it up and running with an old analog TV set they finally asked whether we could play soccer on it. Needless to say that my showing them how it remembers some BASIC commands and lists and executes them did not make any impression. So the question is for real: How do you get today's kids excited about programming? And just recently I looked again for environments that allow even young kids (mine are 7 and 9 years old now) to do something and have fun. Obviously any real, text-oriented programming language wouldn't work well. To cut it short: Something really nice was built by University of Oldenburg: ScratchKara. It is the perfect mixture of Kara, a simulation of a little ladybug and Scratch, an authoring environment from MIT. ScratchKara allows kids to initially simply explore how the bug moves and turns by pressing the action buttons, then move towards sequencing commands through drag & drop, and eventually end up building algorithms with procedures and functions. Even through it is built for kids and beginners, the environment comes with debugging and refactoring, which I found more than amazing. My kids love it and I have to admit I keep thinking about how to solve a bit more advanced problems with this language, which does not allow you to store any state information (other than your call stack). Yes, I am hooked, too... Once the language is understood you can then move to one of the original Kara versions, where you can define the bug's behavior through finite statemachines, Turing tables, Java and other textual languages. And from there, anything is possible.

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• How to justify technology choice to customer?

  - by suslik

  When freelancing / contracting a customer will typically specify functional requirements, acceptance criteria, etc, and the implementation details are in the developer's hands. As a developer your technology choice is a balancing act between what you are most familiar with, technologically what the right tool appears to be, ease of finding coders with this skill and their expense, and a few other factors. I'm in a situation where I have evaluated my options and selected a somewhat obscure open source technology that I believe will get me there faster, easier, and be more maintanable in the long term. It's different, but I think that that is what the requirements call for. The customer has inquired about what I'm going to use to build the solution, and now they are concerned because they've never heard of it before. The reasons for my choice are mostly technical, whereas the customer isn't (but they know some buzzwords!). Explaining these technical reasons will not be easy, and I am not sure if that is the right way to approach this situation anyway. And that's my question: what is the right way to approach this situation so as to cause the least amount of headache for everyone involved?

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• How to represent an agile project to people focused on waterfall [closed]

  - by ahsteele

  Our team has been asked to represent our development efforts in a project plan. No one is unhappy with our work or questioning our ability to deliver, we are just participating in an IT cattle call for project plans. Trouble is we are an agile team and haven't thought about our work in terms of a formal project plan. While we have a general idea of what we are working on next we aren't 100% sure until we plan an iteration. Until now our team has largely operated in a vacuum and has not been required to present our methodology or metrics to outside parties. We follow most of the practices espoused in Extreme Programming. We hold quarterly planning meetings to have a general idea of the stories we are going to work on for a quarter. That said, our stories are documented on 3x5 cards and are only estimated at the beginning of the iteration in which they are going to be worked. After estimation we document the story in Team Foundation Sever. During an iteration, we attach code to stories and mark stories as completed once finished. From this data we are able to generate burn down and velocity charts. Most importantly we know our average velocity for an iteration keeping us from biting off more than we can chew. I am not looking to modify the way we do development but want to present our development activities in a report that someone only familiar with waterfall will understand. In What Does an Agile Project Plan Look Like, Kent McDonald does a good job laying out the differences between agile and waterfall project plans. He specifies the differences in consumable bullets: An agile project plan is feature based An Agile Project Plan is organized into iterations An Agile Project Plan has different levels of detail depending on the time frame An Agile Project Plan is owned by the Team Being able to explain the differences is great, but how best to present the data?

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• Exchange 2007 Email Address Policies

  - by Ryan Migita

  We have recently upgraded to Exchange 2007 (from 2003) and have noticed the change from recipient policies to email address policies. We have two separate domains (let's call them domaina.com and domainb.com) we receive email for, have email address policies and both email address policies are not applied. In our Exchange 2003 environment, domaina.com was the default email address when we created new mailboxes and due to the migration, domainb is the default (and its email address policy is a higher priority). Now, when we create a new mailbox (or edit existing ones), the primary email address becomes domainb.com. Now the question is, is this as simple as putting the email address policies in the correct order? Do I have to apply both policies? What effect will the above changes make to existing mailboxes? Since we do not have any conditions set on the policies, I assume prior to making these changes, I should force all domainb mailboxes to not automatically update email address based on policy? Thanks in advance!

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• Super key to pause, mute mic, and mute speakers in windows

  - by Bruce Connor

  EDIT:Just rephrasing the question: Does anyone know how to mute the mic using autohotkey? Here's why I need it: Whenever someone walks in my office I have to pause the media player. Sometimes, when I'm watching a video, I also have to mute the headphone speakers. And if I'm on a skype call I have to mute the mic. I want to assign all those functions to a single hotkey for convienience (probably the "mute" or "play/pause" key) and I'm pretty sure autohotkey can do that, but I don't know how to mute the mic using autohotkey. Plus, I also want to assign all reverse commands (play and unmute) to a single key (could be a different one or the same one). (I don't think it matters, but I'm using windows 7)

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• SQL Saturday #274 Slovenia

  - by Dejan Sarka

  Yes, here it is SQL Saturday #274 is coming to Slovenia (#sqlsatSlovenia). The event will take place on Saturday, December 21st, at company pixi* labs, Informacijske tehnologije, d.o.o. Poslovna cona A 2 SI-4208 Šencur This company generously offered to host the event. We, the whole Slovenian SQL Server community, are very grateful for this. At this time, a call for speakers went out, and we are already getting the first proposals. We are especially happy that we will get possibility to show the foreign speakers how beautiful Slovenia and especially the capital Ljubljana is in December. Expect a lot of partying right on the streets, no matter of weather. Be prepared, we have slightly weird customs when it comes to drinks. For example, our regular special discount offer is not three drinks for the price of two; it is six drinks for the price of five. If you are a speaker or want to become one, consider sending a proposal. Since most of the sessions will be held in English and you don’t want to speak, consider coming as a visitor as well. Or maybe you would be interested to become a sponsor. Although we are targeting a low budgeted event, any kind of sponsorship is very welcome. Please feel free to contact the organizers if you are interested to become a sponsor: Matija Lah – [email protected], Mladen Prajdic - [email protected], or Dejan Sarka  - [email protected]. Looking forward to see you all!

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• How to write PowerShell code part 2 (Using function)

  - by ybbest

  In the last post, I have showed you how to use external configuration file in your PowerShell script. In this post, I will show you how to create PowerShell function and call external PowerShell script.You can download the script here. 1. In the original script, I create the site directly using New-SPSite command. I will refactor it so that I will create a new function to create the site using New-SPSite. The PowerShell function is quite similar to a C# method. You put your function parameters in () and separate each parameter by a comma (,). Then you put your method body in {}. function add ([int] $num1 , [int] $num2){ $total=$num1+$num2 #Return $total $total } 2. The difference is you do not need semi-colon (;) at the end of each statement and when calling the method you do not need comma (,) to separate each parameter. function add ([int] $num1 , [int] $num2){ $total=$num1+$num2 #Return $total $total } #Calling the function [int] $num1=3 [int] $num2=4 $d= add $num1 $num2 Write-Host $d 3. If you like to return anything from the function, you just need to type in the object you like to return, not need to type return .e.g. $ObjectToReturn not return $ObjectToReturn

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• Struggling with the Single Responsibility Principle

  - by AngryBird

  Consider this example: I have a website. It allows users to make posts (can be anything) and add tags that describe the post. In the code, I have two classes that represent the post and tags. Lets call these classes Post and Tag. Post takes care of creating posts, deleting posts, updating posts, etc. Tag takes care of creating tags, deleting tags, updating tags, etc. There is one operation that is missing. The linking of tags to posts. I am struggling with who should do this operation. It could fit equally well in either class. On one hand, the Post class could have a function that takes a Tag as a parameter, and then stores it in a list of tags. On the other hand, the Tag class could have a function that takes a Post as a parameter and links the Tag to the Post. The above is just an example of my problem. I am actually running into this with multiple classes that are all similar. It could fit equally well in both. Short of actually putting the functionality in both classes, what conventions or design styles exist to help me solve this problem. I am assuming there has to be something short of just picking one? Maybe putting it in both classes is the correct answer?

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• Oracle Flashback Technology - Webcast 9th June 2010

  - by Alex Blyth

  Hi All Here are the details for webcast on Oracle Flashback Technologies on Wednesday (9th June 2010) beginning at 1.30pm (Sydney, Australia Time). The Oracle Database architecture leverages the unique technological advances in the area of database recovery due to human errors. Oracle Flashback Technology provides a set of new features to view and rewind data back and forth in time. The Flashback features offer the capability to query historical data, perform change analysis, and perform self-service repair to recover from logical corruptions while the database is online. With Oracle Flashback Technology, you can indeed undo the past! Oracle9i introduced Flashback Query to provide a simple, powerful and completely non-disruptive mechanism for recovering from human errors. It allows users to view the state of data at a point in time in the past without requiring any structural changes to the database. Oracle Database 10g extended the Flashback Technology to provide fast and easy recovery at the database, table, row, and transaction level. Flashback Technology revolutionizes recovery by operating just on the changed data. The time it takes to recover the error is now equal to the same amount of time it took to make the mistake. Oracle 10g Flashback Technologies includes Flashback Database, Flashback Table, Flashback Drop, Flashback Versions Query, and Flashback Transaction Query. Flashback technology can just as easily be utilized for non-repair purposes, such as historical auditing with Flashback Query and undoing test changes with Flashback Database. Oracle Database 11g introduces an innovative method to manage and query long-term historical data with Flashback Data Archive. This release also provides an easy, one-step transaction backout operation, with the new Flashback Transaction capability. Webcast is at http://strtc.oracle.com (IE6, 7 & 8 supported only)Conference ID for the webcast is 6690835Conference Key: flashbackEnrollment is required. Please click here to enroll.Please use your real name in the name field (just makes it easier for us to help you out if we can't answer your questions on the call) Audio details: NZ Toll Free - 0800 888 157 orAU Toll Free - 1800420354 (or +61 2 8064 0613)Meeting ID: 7914841Meeting Passcode: 09062010 Talk to you all Wednesday 9th June Alex

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• Finding bugs is difficult, right?

  - by Laila

  Something I hear developers tell us all the time is that they take pride in being a developer.and that bugs are a dent in that pride. Someone once told me "I know I have found bugs years later, and it's the worst feeling in the world." So how can you avoid that sinking feeling when you find out a bug has been in production months before someone lets you know about it? Besides, let's face it: hearing about a bug often means a world of pain, because it can take hours to track down where the problem is and more hours (if not days) to fix it. And during that time, you're not working on something new, and that, my friends, is really frustrating! So to cheer you up, we've created a Bug Hunt game, where you battle against the clock to spot bugs. We've really enjoyed putting this together and hope you enjoy playing it too. Once you're done with the bug hunt, we explain how easy it can be to find and fix bugs in real life, using a neat mechanism that we call Automated Error Reporting. Play the game now.

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• Where to place the R code for R+Sweave+LaTeX workflow

  - by claytontstanley

  I spent the last week learning 3 new tools: R, Sweave, and LaTeX. One question that came to my mind though when working through my first project: Where do I place the majority of the R code? The tutorials that I read online placed the majority of the R code in the LaTeX .Rnw file. However, I find having a bunch of R calculations in the LaTeX file distracting. What I do find extremely helpful (of course) is to call out to R code in the LaTeX file and embed the result. So the workflow I've been using is to place 99% of my R code in my .R file. I run that file first, save a bunch of calculations as objects, and output the .Rout file once finished (to save the work). Then when running Sweave, I load up that .Rout file, so that I have the majority of my calculations already completed and in the Sweave R session. Then my LaTeX callouts to R are quite simple: Just give me the XTable stored in 'res.table', or give me the result of an already-computed calculation stored in the variable 'res'. So I push towards the minimal amount of R code in the LaTex file possible, to achieve the desired result (embedding stats results in the LaTeX writeup). Does anyone have any experience with this approach? I'm just worried I might run into trouble further down the line, when I start really trying to load up and leverage this workflow.

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• Reinventing the Wheel, why should I?

  - by Mercfh

  So I have this problem, it may be my OCD (i have OCD it's not severe.....but It makes me very..lets say specific about certain things, programming being one of them) or it may be the fact that I graduated college and still feel "meh" at programming. Reading This made me think "OH thats me!" but thats not really my main problem. My big problem is....anytime im using a high level language/API/etc. I always think to myself that im not really "programming". I know I know...it sounds stupid. But Like I feel like....if i can't figure out how to do it at the lowest level then Im not really "understanding" it. I do this for just about every new technology I learn. I look at the lowest level and try to understand it. Sometimes I do.....most of the time I don't, I mean i've only really been programming for 4 years (at college, if you even call it programming.....our university's program was "meh"). For instance I do a little bit of embedded programming (with the Atmel AVR 8bits/Arduino stuff). And I can't bring myself to use the C compiler, even though it's 8 million times easier than using assembly......it's stupid I know... Anyone else feel like this, I think it's just my OCD that makes me feel this way....but has anyone else ever felt like they need to go down to the lowest level of the language to even be satisfied with using it? I apologize for the very very odd question, but I think it really hinders me in getting deep seeded into a programming language and making a real application of my own. (it's silly I know)

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• Backup database from default (unnamed) sql server instance with powershell.

  - by sparks

  Trying to connect to an instance of SQL Server 2008 on a server we'll call Sputnik. There are no firewalls in between the two devices. Right now I'm just trying to list databases [System.Reflection.Assembly]::LoadWithPartialName("Microsoft.SqlServer.SMO") | Out-Null [System.Reflection.Assembly]::LoadWithPartialName("Microsoft.SqlServer.SmoExtended") | Out-Null [System.Reflection.Assembly]::LoadWithPartialName("Microsoft.SqlServer.ConnectionInfo") | Out-Null [System.Reflection.Assembly]::LoadWithPartialName("Microsoft.SqlServer.SmoEnum") | Out-Null $servername = "Sputnik" $remoteServer = New-Object("Microsoft.SqlServer.Management.Smo.Server") $servername $remoteServer.databases The following error message occurs: The following exception was thrown when trying to enumerate the collection: "Failed to connect to server Sputnik.". At line:1 char:15 + $remoteServer. <<<< databases + CategoryInfo : NotSpecified: (:) [], ExtendedTypeSystemException + FullyQualifiedErrorId : ExceptionInGetEnumerator

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• I don't understand the definition of side effects

  - by Chris Okyen

  I don't understand the wikipedia article on Side Effects: In computer science, a function or expression is said to have a side effect if, in addition to returning a value, it also 1.) Modifies some state or 2.) Has an observable interaction with calling functions or the outside world. I know an example of the first thing that causes a function or expression to have side effects - modifying a state Function and Expression modifying a state : 1.) foo(int X) { return x = x % x; } a = a + 1; What does 2.) - Has an observable interaction with calling functions or the outside world," mean? - Please give an example. The article continues on to say, "For example, a function might modify a global or static variable, modify one of its arguments, raise an exception, write data to a display or file, read data, or call other side-effecting functions...." Are all these examples, examples of 1.) - Modifiying some state , or are they also part of 2.) - Has an observable interaction with calling functions or the outside world?

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• C++ and system exceptions

  - by Abyx

  Why standard C++ doesn't respect system (foreign or hardware) exceptions? E.g. when null pointer dereference occurs, stack isn't unwound, destructors aren't called, and RAII doesn't work. The common advice is "to use system API". But on certain systems, specifically Win32, this doesn't work. To enable stack unwinding for this C++ code // class Foo; // void bar(const Foo&); bar(Foo(1, 2)); one should generate something like this C code Foo tempFoo; Foo_ctor(&tempFoo); __try { bar(&tempFoo); } __finally { Foo_dtor(&tempFoo); } Foo_dtor(&tempFoo); and it's impossible to implement this as C++ library. Upd: Standard doesn't forbid handling system exceptions. But it seems that popular compilers like g++ doesn't respect system exceptions on any platforms just because standard doesn't require this. The only thing that I want - is to use RAII to make code readable and program reliable. I don't want to put hand-crafted try\finally around every call to unknown code. For example in this reusable code, AbstractA::foo is such unknown code: void func(AbstractA* a, AbstractB* b) { TempFile file; a->foo(b, file); } Maybe one will pass to func such implementation of AbstractA, which every Friday will not check if b is NULL, so access violation will happen, application will terminate and temporary file will not be deleted. How many months uses will suffer because of this issue, until either author of func or author of AbstractA will do something with it? Related: Is `catch(...) { throw; }` a bad practice?

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• Farseer tutorial for the absolute beginners

  - by Bil Simser

  This post is inspired (and somewhat a direct copy) of a couple of posts Emanuele Feronato wrote back in 2009 about Box2D (his tutorial was ActionScript 3 based for Box2D, this is C# XNA for the Farseer Physics Engine). Here’s what we’re building: What is Farseer The Farseer Physics Engine is a collision detection system with realistic physics responses to help you easily create simple hobby games or complex simulation systems. Farseer was built as a .NET version of Box2D (based on the Box2D.XNA port of Box2D). While the constructs and syntax has changed over the years, the principles remain the same. This tutorial will walk you through exactly what Emanuele create for Flash but we’ll be doing it using C#, XNA and the Windows Phone platform. The first step is to download the library from its home on CodePlex. If you have NuGet installed, you can install the library itself using the NuGet package that but we’ll also be using some code from the Samples source that can only be obtained by downloading the library. Once you download and unpacked the zip file into a folder and open the solution, this is what you will get: The Samples XNA WP7 project (and content) have all the demos for Farseer. There’s a wealth of info here and great examples to look at to learn. The Farseer Physics XNA WP7 project contains the core libraries that do all the work. DebugView XNA contains an XNA-ready class to let you view debug data and information in the game draw loop (which you can copy into your project or build the source and reference the assembly). The downloaded version has to be compiled as it’s only available in source format so you can do that now if you want (open the solution file and rebuild everything). If you’re using the NuGet package you can just install that. We only need the core library and we’ll be copying in some code from the samples later. Your first Farseer experiment Start Visual Studio and create a new project using the Windows Phone template can call it whatever you want. It’s time to edit Game1.cs 1 public class Game1 : Game 2 { 3 private readonly GraphicsDeviceManager _graphics; 4 private DebugViewXNA _debugView; 5 private Body _floor; 6 private SpriteBatch _spriteBatch; 7 private float _timer; 8 private World _world; 9 10 public Game1() 11 { 12 _graphics = new GraphicsDeviceManager(this) 13 { 14 PreferredBackBufferHeight = 800, 15 PreferredBackBufferWidth = 480, 16 IsFullScreen = true 17 }; 18 19 Content.RootDirectory = "Content"; 20 21 // Frame rate is 30 fps by default for Windows Phone. 22 TargetElapsedTime = TimeSpan.FromTicks(333333); 23 24 // Extend battery life under lock. 25 InactiveSleepTime = TimeSpan.FromSeconds(1); 26 } 27 28 protected override void LoadContent() 29 { 30 // Create a new SpriteBatch, which can be used to draw textures. 31 _spriteBatch = new SpriteBatch(_graphics.GraphicsDevice); 32 33 // Load our font (DebugViewXNA needs it for the DebugPanel) 34 Content.Load<SpriteFont>("font"); 35 36 // Create our World with a gravity of 10 vertical units 37 if (_world == null) 38 { 39 _world = new World(Vector2.UnitY*10); 40 } 41 else 42 { 43 _world.Clear(); 44 } 45 46 if (_debugView == null) 47 { 48 _debugView = new DebugViewXNA(_world); 49 50 // default is shape, controller, joints 51 // we just want shapes to display 52 _debugView.RemoveFlags(DebugViewFlags.Controllers); 53 _debugView.RemoveFlags(DebugViewFlags.Joint); 54 55 _debugView.LoadContent(GraphicsDevice, Content); 56 } 57 58 // Create and position our floor 59 _floor = BodyFactory.CreateRectangle( 60 _world, 61 ConvertUnits.ToSimUnits(480), 62 ConvertUnits.ToSimUnits(50), 63 10f); 64 _floor.Position = ConvertUnits.ToSimUnits(240, 775); 65 _floor.IsStatic = true; 66 _floor.Restitution = 0.2f; 67 _floor.Friction = 0.2f; 68 } 69 70 protected override void Update(GameTime gameTime) 71 { 72 // Allows the game to exit 73 if (GamePad.GetState(PlayerIndex.One).Buttons.Back == ButtonState.Pressed) 74 Exit(); 75 76 // Create a random box every second 77 _timer += (float) gameTime.ElapsedGameTime.TotalSeconds; 78 if (_timer >= 1.0f) 79 { 80 // Reset our timer 81 _timer = 0f; 82 83 // Determine a random size for each box 84 var random = new Random(); 85 var width = random.Next(20, 100); 86 var height = random.Next(20, 100); 87 88 // Create it and store the size in the user data 89 var box = BodyFactory.CreateRectangle( 90 _world, 91 ConvertUnits.ToSimUnits(width), 92 ConvertUnits.ToSimUnits(height), 93 10f, 94 new Point(width, height)); 95 96 box.BodyType = BodyType.Dynamic; 97 box.Restitution = 0.2f; 98 box.Friction = 0.2f; 99 100 // Randomly pick a location along the top to drop it from 101 box.Position = ConvertUnits.ToSimUnits(random.Next(50, 400), 0); 102 } 103 104 // Advance all the elements in the world 105 _world.Step(Math.Min((float) gameTime.ElapsedGameTime.TotalMilliseconds*0.001f, (1f/30f))); 106 107 // Clean up any boxes that have fallen offscreen 108 foreach (var box in from box in _world.BodyList 109 let pos = ConvertUnits.ToDisplayUnits(box.Position) 110 where pos.Y > _graphics.GraphicsDevice.Viewport.Height 111 select box) 112 { 113 _world.RemoveBody(box); 114 } 115 116 base.Update(gameTime); 117 } 118 119 protected override void Draw(GameTime gameTime) 120 { 121 GraphicsDevice.Clear(Color.FromNonPremultiplied(51, 51, 51, 255)); 122 123 _spriteBatch.Begin(); 124 125 var projection = Matrix.CreateOrthographicOffCenter( 126 0f, 127 ConvertUnits.ToSimUnits(_graphics.GraphicsDevice.Viewport.Width), 128 ConvertUnits.ToSimUnits(_graphics.GraphicsDevice.Viewport.Height), 0f, 0f, 129 1f); 130 _debugView.RenderDebugData(ref projection); 131 132 _spriteBatch.End(); 133 134 base.Draw(gameTime); 135 } 136 } 137 Lines 4: Declare the debug view we’ll use for rendering (more on that later). Lines 8: Declare _world variable of type class World. World is the main object to interact with the Farseer engine. It stores all the joints and bodies, and is responsible for stepping through the simulation. Lines 12-17: Create the graphics device we’ll be rendering on. This is an XNA component and we’re just setting it to be the same size as the phone and toggling it to be full screen (no system tray). Lines 34: We create a SpriteFont here by adding it to the project. It’s called “font” because that’s what the DebugView uses but you can name it whatever you want (and if you’re not using DebugView for your production app you might have several fonts). Lines 37-44: We create the physics environment that Farseer uses to contain all the objects by specifying it here. We’re using Vector2.UnitY*10 to represent the gravity to be used in the environment. In other words, 10 units going in a downward motion. Lines 46-56: We create the DebugViewXNA here. This is copied from the […] from the code you downloaded and provides the ability to render all entities onto the screen. In a production release you’ll be doing the rendering yourself of each object but we cheat a bit for the demo and let the DebugView do it for us. The other thing it can provide is to render out a panel of debugging information while the simulation is going on. This is useful in tracking down objects, figuring out how something works, or just keeping track of what’s in the engine. Lines 49-67: Here we create a rigid body (Farseer only supports rigid bodies) to represent the floor that we’ll drop objects onto. We create it by using one of the Farseer factories and specifying the width and height. The ConvertUnits class is copied from the samples code as-is and lets us toggle between display units (pixels) and simulation units (usually metres). We’re creating a floor that’s 480 pixels wide and 50 pixels high (converting them to SimUnits for the engine to understand). We also position it near the bottom of the screen. Values are in metres and when specifying values they refer to the centre of the body object. Lines 77-78: The game Update method fires 30 times a second, too fast to be creating objects this quickly. So we use a variable to track the elapsed seconds since the last update, accumulate that value, then create a new box to drop when 1 second has passed. Lines 89-94: We create a box the same way we created our floor (coming up with a random width and height for the box). Lines 96-101: We set the box to be Dynamic (rather than Static like the floor object) and position it somewhere along the top of the screen. And now you created the world. Gravity does the rest and the boxes fall to the ground. Here’s the result: Farseer Physics Engine Demo using XNA Lines 105: We must update the world at every frame. We do this with the Step method which takes in the time interval. [more] Lines 108-114: Body objects are added to the world but never automatically removed (because Farseer doesn’t know about the display world, it has no idea if an item is on the screen or not). Here we just loop through all the entities and anything that’s dropped off the screen (below the bottom) gets removed from the World. This keeps our entity count down (the simulation never has more than 30 or 40 objects in the world no matter how long you run it for). Too many entities and the app will grind to a halt. Lines 125-130: Farseer knows nothing about the UI so that’s entirely up to you as to how to draw things. Farseer is just tracking the objects and moving them around using the physics engine and it’s rules. You’ll still use XNA to draw items (using the SpriteBatch.Draw method) so you can load up your usual textures and draw items and pirates and dancing zombies all over the screen. Instead in this demo we’re going to cheat a little. In the sample code for Farseer you can download there’s a project called DebugView XNA. This project contains the DebugViewXNA class which just handles iterating through all the bodies in the world and drawing the shapes. So we call the RenderDebugData method here of that class to draw everything correctly. In the case of this demo, we just want to draw Shapes so take a look at the source code for the DebugViewXNA class as to how it extracts all the vertices for the shapes created (in this case simple boxes) and draws them. You’ll learn a *lot* about how Farseer works just by looking at this class. That’s it, that’s all. Simple huh? Hope you enjoy the code and library. Physics is hard and requires some math skills to really grok. The Farseer Physics Engine makes it pretty easy to get up and running and start building games. In future posts we’ll get more in-depth with things you can do with the engine so this is just the beginning. Enjoy!

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• (Abstract) Game engine design

  - by lukeluke

  I am writing a simple 2D game (for mobile platforms) for the first time. From an abstract point of view, i have the main player controlled by the human, the enemies, elments that will interact with the main player, other living elements that will be controlled by a simple AI (both enemies and non-enemies). The human player will be totally controlled by the player, the other actors will be controlled by AI. So i have a class CActor and a class CActorLogic to start with. I would define a CActor subclass CHero (the main player controlled with some input device). This class will probably implement some type of listener, in order to capture input events. The other players controlled by the AI will be probably a specific subclass of CActor (a subclass per-type, obviously). This seems to be reasonable. The CActor class should have a reference to a method of CActorLogic, that we will call something like CActorLogic::Advance() or similar. Actors should have a visual representation. I would introduce a CActorRepresentation class, with a method like Render() that will draw the actor (that is, the right frame of the right animation). Where to change the animation? Well, the actor logic method Advance() should take care of checking collisions and other things. I would like to discuss the design of a game engine (actors, entities, objects, messages, input handling, visualization of object states (that is, rendering, sound output and so on)) but not from a low level point of view, but from an high level point of view, like i have described above. My question is: is there any book/on line resource that will help me organize things (using an object oriented approach)? Thanks

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• Calling the LWRP from the Exception Handler

  - by Sarah Haskins

  Is it possible to call out to a Provider (LWRP) from a Chef Exception Handler? I think my Provider is out of scope, but I don't know if what I am trying to do is possible? or advisable? Here is my provider code (cookbooks/config/provider/signal.rb): action :failure do Chef::Log.info("Yeah success") end Here is my exception handler code (exception_handler/handlers/exceptionHandler.rb): require 'chef/handler' config_signal "signal" do action :nothing end class Chef class Handler class LogCollector < Chef::Handler notifies :failure, resources(:config_signal => signal) end end end Also, if anyone has a good recommendation for general reading about scope in the context of Chef I'd appreciate it.

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• Is this project Structure Valid?

  - by rafuru

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

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• Can non-IT people handle a wiki?

  - by Andrew Heath

  (I'm hoping that some of you will have encountered this issue before and can offer some insights...) My company is looking to improve their market research data management. Current data management style: "Hey Jimbo, where's that picture of our WhatZit 2.0? "yeah I remember that email about that company from that guy, gimme a few minutes to search my Outlook" "who has the newest copy of the Important Competitor's product catalogue? Mine is from '09." ... "Colleen does, and she's on maternity leave. You'll have to call her to get her workstation password..." Desired data management style: data organized neatly by topic (legal, economic, industrial, competitor) for each topic, multiple media types stored together (company product images, press releases, contact info) but still neatly sorted by type data editing histories communal access (no data silos) I was thinking about setting up a department wiki for all users to access. It seems to satisfy the four criteria above, but I'm a little concerned about how user-friendly (read: decipherable to non-technical people) it is for the more advanced features like image galleries, article formatting, and the like. Has anyone here setup a wiki for non-IT people and had it not catch on fire//become a ghost town//look like Geocities? Bonus question: can you see any obvious drawbacks to my choice of MediaWiki (or any other wiki) for solving this problem? Thank you.

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• What's the proper term for a function inverse to a constructor? Deconstructor, destructor, or something else?

  - by Petr Pudlák

  Edit: I'm rephrasing the question a bit. Apparently I caused some confusion because I didn't realize that the term destructor is used in OOP for something quite different - it's a function invoked when an object is being destroyed. In functional programming we (try to) avoid mutable state so there is no such equivalent to it. (I added the proper tag to the question.) Instead, I've seen that the record field for unwrapping a value (especially for single-valued data types such as newtypes) is sometimes called destructor or perhaps deconstructor. For example, let's have (in Haskell): newtype Wrap = Wrap { unwrap :: Int } Here Wrap is the constructor and unwrap is what? I've seen both, for example: ... Most often, one supplies smart constructors and destructors for these to ease working with them. ... at Haskell wiki, or ... The general theme here is to fuse constructor - deconstructor pairs like ... at Haskell wikibook (here it's probably meant in a bit more general sense). The questions are: How do we call unwrap in functional programming? Deconstructor? Destructor? Or by some other term? And to clarify, is this terminology applicable to other functional languages, or is it used just in the Has

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• Simplest way to render image over top of another with another image used as mask in OpenGL?

  - by Adam Naylor

  The effect I'm looking for is to have a single large background image that is always visible (at full alpha) and then show a second image (what I call a light map or specular map) that is partially shown over the top based on a third image (which is effectively a mask). The effect is similar to this effect except instead of simply darkening or lightening the background image using the third image it needs to mask the second without effecting the first at all. The third image is the only one that moves therefore hard baking the third images alpha into the second image isn't an option. If my explanation isn't clear I'll provide visual examples when I have more time. I'd prefer not to go down a shader route as I haven't taught myself this area yet so unless I have too I'd rather try to achieve this with simple alpha blending. Happy to use a shader approach. Cheers. Additional These third images are obviously light sources being cast onto the first image showing the specular information from the second image to simulate the light 'shining' off the objects in the first image. The solution I implement will need to allow two light sources to potentially overlap so my current thoughts are that the alpha values of the two images will need to be combined (Added?) to produce a final image which masks the second image? Don't worry about things like coloured lights. For this technique the lights are all considered white.

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• ArchBeat Link-o-Rama for December 14, 2012

  - by Bob Rhubart

  JMS Step 6 - How to Set Up an AQ JMS (Advanced Queueing JMS) for SOA Purposes | John-Brown Evans John Brown Evans' post continues the series of JMS articles that demonstrate how to use JMS queues in a SOA context. "This example leads you through the creation of an Oracle database Advanced Queue and the related WebLogic server objects in order to use AQ JMS in connection with a SOA composite," John explains. And if you missed the first 5 steps, don't worry – the post includes links. Cloud Deployment Models | B. R. Clouse Looking out for the cloud newbies... "As the cloud paradigm grows in depth and breadth, more readers are approaching the topic for the first time, or from a new perspective," says B. R. Clouse. "This blog is a basic review of cloud deployment models, to help orient newcomers and neophytes." Understanding the JSF Lifecycle and ADF Optimized Lifecycle | Steven Davelaar Would you call that a surprise ending? Oracle WebCenter & ADF Architecture Team (A-Team) member learned a lot more than he expected while creating a UKOUG presentation entitled "What you need to know about JSF to be succesful with ADF." Using Oracle Enterprise Manager Cloud Control 12c with Filer Snapshotting | Porus Homi Havewala This concise technical article includes a script for database backup using snapshots and cataloging in RMAN. Thought for the Day "A program which perfectly meets a lousy specification is a lousy program." — Cem Kaner Source: SoftwareQuotes.com

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• Using a permutation table for simplex noise without storing it

  - by J. C. Leitão

  Generating Simplex noise requires a permutation table for randomisation (e.g. see this question or this example). In some applications, we need to persist the state of the permutation table. This can be done by creating the table, e.g. using def permutation_table(seed): table_size = 2**10 # arbitrary for this question l = range(1, table_size + 1) random.seed(seed) # ensures the same shuffle for a given seed random.shuffle(l) return l + l # see shared link why l + l; is a detail and storing it. Can we avoid storing the full table by generating the required elements every time they are required? Specifically, currently I store the table and call it using table[i] (table is a list). Can I avoid storing it by having a function that computes the element i, e.g. get_table_element(seed, i). I'm aware that cryptography already solved this problem using block cyphers, however, I found it too complex to go deep and implement a block cypher. Does anyone knows a simple implementation of a block cypher to this problem?

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