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• Scala factory pattern returns unusable abstract type

  - by GGGforce

  Please let me know how to make the following bit of code work as intended. The problem is that the Scala compiler doesn't understand that my factory is returning a concrete class, so my object can't be used later. Can TypeTags or type parameters help? Or do I need to refactor the code some other way? I'm (obviously) new to Scala. trait Animal trait DomesticatedAnimal extends Animal trait Pet extends DomesticatedAnimal {var name: String = _} class Wolf extends Animal class Cow extends DomesticatedAnimal class Dog extends Pet object Animal { def apply(aType: String) = { aType match { case "wolf" => new Wolf case "cow" => new Cow case "dog" => new Dog } } } def name(a: Pet, name: String) { a.name = name println(a +"'s name is: " + a.name) } val d = Animal("dog") name(d, "fred") The last line of code fails because the compiler thinks d is an Animal, not a Dog.

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• Unit testing in Django

  - by acjohnson55

  I'm really struggling to write effective unit tests for a large Django project. I have reasonably good test coverage, but I've come to realize that the tests I've been writing are definitely integration/acceptance tests, not unit tests at all, and I have critical portions of my application that are not being tested effectively. I want to fix this ASAP. Here's my problem. My schema is deeply relational, and heavily time-oriented, giving my model object high internal coupling and lots of state. Many of my model methods query based on time intervals, and I've got a lot of auto_now_add going on in timestamped fields. So take a method that looks like this for example: def summary(self, startTime=None, endTime=None): # ... logic to assign a proper start and end time # if none was provided, probably using datetime.now() objects = self.related_model_set.manager_method.filter(...) return sum(object.key_method(startTime, endTime) for object in objects) How does one approach testing something like this? Here's where I am so far. It occurs to me that the unit testing objective should be given some mocked behavior by key_method on its arguments, is summary correctly filtering/aggregating to produce a correct result? Mocking datetime.now() is straightforward enough, but how can I mock out the rest of the behavior? I could use fixtures, but I've heard pros and cons of using fixtures for building my data (poor maintainability being a con that hits home for me). I could also setup my data through the ORM, but that can be limiting, because then I have to create related objects as well. And the ORM doesn't let you mess with auto_now_add fields manually. Mocking the ORM is another option, but not only is it tricky to mock deeply nested ORM methods, but the logic in the ORM code gets mocked out of the test, and mocking seems to make the test really dependent on the internals and dependencies of the function-under-test. The toughest nuts to crack seem to be the functions like this, that sit on a few layers of models and lower-level functions and are very dependent on the time, even though these functions may not be super complicated. My overall problem is that no matter how I seem to slice it, my tests are looking way more complex than the functions they are testing.

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• How should I make searching a relational database more efficient?

  - by Travis J

  This is in the scope of a web application. I have a database which has a few nested relations. There is a feature which depicts the history of a large chain of relations. It is essentially a data analysis feature. The issue is that in order to search, a large object graph must be loaded - the loading time for this object graph is not quick enough to be viable. The problem is that without loading the whole graph it makes searching from a single string nearly impossible. In order to search, explicit fields must be specified and the search data supplied. Is there a design pattern for exposing the data in a way which facilitates a single string search instead of having to explicitly define parameters?

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• Some non-generic collections

  - by Simon Cooper

  Although the collections classes introduced in .NET 2, 3.5 and 4 cover most scenarios, there are still some .NET 1 collections that don't have generic counterparts. In this post, I'll be examining what they do, why you might use them, and some things you'll need to bear in mind when doing so. BitArray System.Collections.BitArray is conceptually the same as a List<bool>, but whereas List<bool> stores each boolean in a single byte (as that's what the backing bool[] does), BitArray uses a single bit to store each value, and uses various bitmasks to access each bit individually. This means that BitArray is eight times smaller than a List<bool>. Furthermore, BitArray has some useful functions for bitmasks, like And, Xor and Not, and it's not limited to 32 or 64 bits; a BitArray can hold as many bits as you need. However, it's not all roses and kittens. There are some fundamental limitations you have to bear in mind when using BitArray: It's a non-generic collection. The enumerator returns object (a boxed boolean), rather than an unboxed bool. This means that if you do this: foreach (bool b in bitArray) { ... } Every single boolean value will be boxed, then unboxed. And if you do this: foreach (var b in bitArray) { ... } you'll have to manually unbox b on every iteration, as it'll come out of the enumerator an object. Instead, you should manually iterate over the collection using a for loop: for (int i=0; i<bitArray.Length; i++) { bool b = bitArray[i]; ... } Following on from that, if you want to use BitArray in the context of an IEnumerable<bool>, ICollection<bool> or IList<bool>, you'll need to write a wrapper class, or use the Enumerable.Cast<bool> extension method (although Cast would box and unbox every value you get out of it). There is no Add or Remove method. You specify the number of bits you need in the constructor, and that's what you get. You can change the length yourself using the Length property setter though. It doesn't implement IList. Although not really important if you're writing a generic wrapper around it, it is something to bear in mind if you're using it with pre-generic code. However, if you use BitArray carefully, it can provide significant gains over a List<bool> for functionality and efficiency of space. OrderedDictionary System.Collections.Specialized.OrderedDictionary does exactly what you would expect - it's an IDictionary that maintains items in the order they are added. It does this by storing key/value pairs in a Hashtable (to get O(1) key lookup) and an ArrayList (to maintain the order). You can access values by key or index, and insert or remove items at a particular index. The enumerator returns items in index order. However, the Keys and Values properties return ICollection, not IList, as you might expect; CopyTo doesn't maintain the same ordering, as it copies from the backing Hashtable, not ArrayList; and any operations that insert or remove items from the middle of the collection are O(n), just like a normal list. In short; don't use this class. If you need some sort of ordered dictionary, it would be better to write your own generic dictionary combining a Dictionary<TKey, TValue> and List<KeyValuePair<TKey, TValue>> or List<TKey> for your specific situation. ListDictionary and HybridDictionary To look at why you might want to use ListDictionary or HybridDictionary, we need to examine the performance of these dictionaries compared to Hashtable and Dictionary<object, object>. For this test, I added n items to each collection, then randomly accessed n/2 items: So, what's going on here? Well, ListDictionary is implemented as a linked list of key/value pairs; all operations on the dictionary require an O(n) search through the list. However, for small n, the constant factor that big-o notation doesn't measure is much lower than the hashing overhead of Hashtable or Dictionary. HybridDictionary combines a Hashtable and ListDictionary; for small n, it uses a backing ListDictionary, but switches to a Hashtable when it gets to 9 items (you can see the point it switches from a ListDictionary to Hashtable in the graph). Apart from that, it's got very similar performance to Hashtable. So why would you want to use either of these? In short, you wouldn't. Any gain in performance by using ListDictionary over Dictionary<TKey, TValue> would be offset by the generic dictionary not having to cast or box the items you store, something the graphs above don't measure. Only if the performance of the dictionary is vital, the dictionary will hold less than 30 items, and you don't need type safety, would you use ListDictionary over the generic Dictionary. And even then, there's probably more useful performance gains you can make elsewhere.

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• How are buttons made to be clicked?

  - by Johnny

  I just want to ask a general question. According to that answer, Ill continue thinking. You know in games there are lots of clickable items. Play button, exit, comboboxes maybe etc. My question is are those buttons drawn in same canvas with background and all other things, or for every different thing there is another canvas object? My question is about for general. Im not asking about a specific game, im asking how they are made generally. Im planning to start a game on Android, and Im confused actually how to design buttons, and other object. Probably Im going to use View/SurfaceView for now. I don't have much experience with OpenGL yet. Thanks in advance.

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• What's a good data structure solution for a scene manager in XNA?

  - by tunnuz

  Hello, I'm playing with XNA for a game project of myself, I had previous exposure to OpenGL and worked a bit with Ogre, so I'm trying to get the same concepts working on XNA. Specifically I'm trying to add to XNA a scene manager to handle hierarchical transforms, frustum (maybe even occlusion) culling and transparency object sorting. My plan was to build a tree scene manager to handle hierarchical transforms and lighting, and then use an Octree for frustum culling and object sorting. The problem is how to do geometry sorting to support transparencies correctly. I know that sorting is very expensive if done on a per-polygon basis, so expensive that it is not even managed by Ogre. But still images from Ogre look right. Any ideas on how to do it and which data structures to use and their capabilities? I know people around is using: Octrees Kd-trees (someone on GameDev forum said that these are far better than Octrees) BSP (which should handle per-polygon ordering but are very expensive) BVH (but just for frustum and occlusion culling) Thank you Tunnuz

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• How to update coffee script?

  - by Tetsu

  I got a following error when I tried to watch coffee scripts by coffee -o js -cw coffee. /usr/local/lib/node_modules/coffee-script/lib/coffee-script/command.js:321 throw e; ^ Error: watch Unknown system errno 28 at errnoException (fs.js:636:11) at FSWatcher.start (fs.js:663:11) at Object.watch (fs.js:691:11) at /usr/local/lib/node_modules/coffee-script/lib/coffee-script/command.js:287:27 at Object.oncomplete (/usr/local/lib/node_modules/coffee-script/lib/coffee-script/command.js:100:11) I have no idea what is going with error. Then I checked the versions, coffee -v is 1.6.1 and node -v is v0.6.12. According the official site( http://coffeescript.org/ ) the latest version is 1.6.3, so I wanted update coffee by npm update -g coffee-script, but this fails also. npm WARN [email protected] package.json: bugs['name'] should probably be bugs['url'] npm http GET https://registry.npmjs.org/coffee-script npm http 304 https://registry.npmjs.org/coffee-script How can I update coffee script? Edit 2013/10/11 In my coffee script directory there is only one file box_wrapper.coffee. $ -> $("body").children().wrap -> "<div id='#{$(@).attr "id"}_box' class='wrapper'/>" Edit 2013/10/16 I tried to re-install coffee, so I've done like this. $ sudo npm -g rm coffee npm WARN Not installed in /usr/local/lib/node_modules coffee $ coffee -v CoffeeScript version 1.6.1 I can't remove coffee. And I tried also like this. $ sudo apt-get remove npm $ npm -v -bash: /usr/bin/npm: No such file or directory $ sudo apt-get install npm $ npm -v 1.1.4 $ sudo npm -g install coffee # I omit a lot of `GET` parts. npm http 304 https://registry.npmjs.org/mkdirp/0.3.4 npm ERR! error installing [email protected] npm http 304 https://registry.npmjs.org/assertion-error/1.0.0 npm http 304 https://registry.npmjs.org/growl npm http 304 https://registry.npmjs.org/jade/0.26.3 npm http 304 https://registry.npmjs.org/diff/1.0.2 npm http 304 https://registry.npmjs.org/mkdirp/0.3.5 npm http 304 https://registry.npmjs.org/glob/3.2.1 npm http 304 https://registry.npmjs.org/ms/0.3.0 npm ERR! error rolling back [email protected] Error: UNKNOWN, unknown error '/usr/local/lib/node_modules/coffee/node_modules/express' npm ERR! error installing [email protected] npm ERR! EEXIST, file already exists '/usr/local/lib/node_modules/coffee/node_modules/mocha/node_modules' npm ERR! File exists: /usr/local/lib/node_modules/coffee/node_modules/mocha/node_modules npm ERR! Move it away, and try again. npm ERR! npm ERR! System Linux 3.2.0-54-generic-pae npm ERR! command "node" "/usr/bin/npm" "-g" "install" "coffee" npm ERR! cwd /home/ironsand npm ERR! node -v v0.6.12 npm ERR! npm -v 1.1.4 npm ERR! path /usr/local/lib/node_modules/coffee/node_modules/mocha/node_modules npm ERR! fstream_path /usr/local/lib/node_modules/coffee/node_modules/mocha/node_modules/___debug.npm npm ERR! fstream_type Directory npm ERR! fstream_class DirWriter npm ERR! code EEXIST npm ERR! message EEXIST, file already exists '/usr/local/lib/node_modules/coffee/node_modules/mocha/node_modules' npm ERR! errno {} npm ERR! fstream_stack /usr/lib/nodejs/fstream/lib/writer.js:161:23 npm ERR! fstream_stack Object.oncomplete (/usr/lib/nodejs/mkdirp.js:34:53) npm ERR! EEXIST, file already exists '/usr/local/lib/node_modules/coffee/node_modules/mocha/node_modules' npm ERR! File exists: /usr/local/lib/node_modules/coffee/node_modules/mocha/node_modules npm ERR! Move it away, and try again. npm ERR! npm ERR! System Linux 3.2.0-54-generic-pae npm ERR! command "node" "/usr/bin/npm" "-g" "install" "coffee" npm ERR! cwd /home/ironsand npm ERR! node -v v0.6.12 npm ERR! npm -v 1.1.4 npm ERR! path /usr/local/lib/node_modules/coffee/node_modules/mocha/node_modules npm ERR! fstream_path /usr/local/lib/node_modules/coffee/node_modules/mocha/node_modules/___debug.npm npm ERR! fstream_type Directory npm ERR! fstream_class DirWriter npm ERR! code EEXIST npm ERR! message EEXIST, file already exists '/usr/local/lib/node_modules/coffee/node_modules/mocha/node_modules' npm ERR! errno {} npm ERR! fstream_stack /usr/lib/nodejs/fstream/lib/writer.js:161:23 npm ERR! fstream_stack Object.oncomplete (/usr/lib/nodejs/mkdirp.js:34:53) npm ERR! npm ERR! Additional logging details can be found in: npm ERR! /home/ironsand/npm-debug.log npm not ok And npm-debug.log is a blank file.

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• How can I solve for the game's world coordinates?

  - by HyperGroups

  I've used 3DReaperDX to get a obj file, the header information are shown as follows: #AR=2.00606, FOV=45.09583(height), Xscale:0.83290, Yscale:0.41519, Zscale:1.0 #************************************************** #ALPHABLENDENABLE: No #ZENABLE: Yes #ZWRITEENABLE: Yes #TWOSIDED: No #INVALID: No #THIN: No #RENDERTARGET_IS_BACKBUFFER: Yes #WIDTH_DO_MATCH: Yes #RGBWRITEDISABLED: No # object DrawCall_0 to come ... g v 2143.35547 6654.99023 25835.37109 v 2243.17773 6296.61523 25957.53906 v 2343.00000 5856.84473 26093.97656 How can I get the game's world coordinates. For example: I can map the scaleTransform to the VertexData scaleTransform={X1scale,Y1scale,Z1scale} {0.8329,0.41519,1.} Is the obj file enough to get the game's world coordinates? I want to put a object in this ground, and the coordinates is the same to that in the Game Engine, And I can place something(with some fixed coordinates) in the Game and then to use 3DReaper to get the obj file. If the file is not enough itself to get the game world coordinates.

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• Item cannot be installed or removed until the package catalogue is repaired

  - by Alex Thorne

  After installing Microsoft Windows Compatibility Layer (meta-package) i receive an error Item cannot be installed or removed until the package catalogue is repaired. Do you want to repair it Ok, I thought... I'll just click repair and be done with it. After doing so I receive another error. The full text reads: installArchives() failed: (Reading database ... (Reading database ... 5% (Reading database ... 10% (Reading database ... 15% (Reading database ... 20% (Reading database ... 25% (Reading database ... 30% (Reading database ... 35% (Reading database ... 40% (Reading database ... 45% (Reading database ... 50% (Reading database ... 55% (Reading database ... 60% (Reading database ... 65% (Reading database ... 70% (Reading database ... 75% (Reading database ... 80% (Reading database ... 85% (Reading database ... 90% (Reading database ... 95% (Reading database ... 100% (Reading database ... 212945 files and directories currently installed.) Unpacking libasound2:i386 (from .../libasound2_1.0.25-1ubuntu10_i386.deb) ... dpkg: error processing /var/cache/apt/archives/libasound2_1.0.25-1ubuntu10_i386.deb (--unpack): './usr/share/alsa/cards/ICE1712.conf' is different from the same file on the system dpkg-deb: error: subprocess paste was killed by signal (Broken pipe) Errors were encountered while processing: /var/cache/apt/archives/libasound2_1.0.25-1ubuntu10_i386.deb Error in function: SystemError: E:Sub-process /usr/bin/dpkg returned an error code (1) dpkg: dependency problems prevent configuration of wine1.4-i386:i386: wine1.4-i386:i386 depends on libasound2 (>= 1.0.23); however: Package libasound2:i386 is not installed. dpkg: error processing wine1.4-i386:i386 (--configure): dependency problems - leaving unconfigured dpkg: dependency problems prevent configuration of wine1.4: wine1.4 depends on wine1.4-i386 (= 1.4-0ubuntu4); however: Package wine1.4-i386 is not installed. Package wine1.4-i386:i386 is not configured yet. dpkg: error processing wine1.4 (--configure): dependency problems - leaving unconfigured dpkg: dependency problems prevent configuration of wine: wine depends on wine1.4; however: Package wine1.4 is not configured yet. dpkg: error processing wine (--configure): dependency problems - leaving unconfigured dpkg: dependency problems prevent configuration of wine1.4-common: wine1.4-common depends on wine1.4 (= 1.4-0ubuntu4); however: Package wine1.4 is not configured yet. dpkg: error processing wine1.4-common (--configure): dependency problems - leaving unconfigured dpkg: dependency problems prevent configuration of wine1.4-amd64: wine1.4-amd64 depends on wine1.4-common (= 1.4-0ubuntu4); however: Package wine1.4-common is not configured yet. dpkg: error processing wine1.4-amd64 (--configure): dependency problems - leaving unconfigured So I click OK and now I'm back to previous screen ("Item cannot be installed ...") I click on cancel and go to the red circle on the top right on my screen and try to update from there and receive this error After that I just get thrown these errors So now I can't add or remove any programs on my system. Does anyone have any idea how to fix this?

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• Best practices for periodically saving game state to disk

  - by Ben Morris

  I'm working on an MMO. All of the player and environment data lives on a server and is kept in memory. There's a "world" object which keeps track of all of the maps, characters, etc. and their relations to each other. To avoid data loss in case of a crash, I've been periodically serializing the world to disk. The trouble is, this object can be quite large, so when the server starts writing, there's noticeable in-game slowdown for a few seconds, which I'd like to avoid. Any pointers on how to go about this in a more efficient way?

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• Are there well-known PowerShell coding conventions?

  - by Tahir Hassan

  Are there any well-defined conventions when programming in PowerShell? For example, in scripts which are to be maintained long-term, do we need to: Use the real cmdlet name or alias? Specify the cmdlet parameter name in full or only partially (dir -Recurse versus dir -r) When specifying string arguments for cmdlets do you enclose them in quotes (New-Object 'System.Int32' versus New-Object System.Int32 When writing functions and filters do you specify the types of parameters? Do you write cmdlets in the (official) correct case? For keywords like BEGIN...PROCESS...END do you write them in uppercase only? It seems that MSDN lack coding conventions document for PowerShell, while such document exist for example for C#.

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• Stir Trek 2: Iron Man Edition

  Next month (7 May 2010) Ill be presenting at the second annual Stir Trek event in Columbus, Ohio. Stir Trek (so named because last year its themes mixed MIX and the opening of the Star Trek movie) is a very cool local event.  Its a lot of fun to present at and to attend, because of its unique venue: a movie theater.  And whats more, the cost of admission includes a private showing of a new movie (this year: Iron Man 2).  The sessions cover a variety of topics (not just Microsoft), similar to CodeMash.  The event recently sold out, so Im not telling you all of this so that you can go and sign up (though I believe you can get on the waitlist still).  Rather, this is pretty much just an excuse for me to talk about my session as a way to organize my thoughts. Im actually speaking on the same topic as I did last year, but the key difference is that last year the subject of my session was nowhere close to being released, and this year, its RTM (as of last week).  Thats right, the topic is Whats New in ASP.NET 4 how did you guess? Whats New in ASP.NET 4 So, just what *is* new in ASP.NET 4?  Hasnt Microsoft been spending all of their time on Silverlight and MVC the last few years?  Well, actually, no.  There are some pretty cool things that are now available out of the box in ASP.NET 4.  Theres a nice summary of the new features on MSDN.  Here is my super-brief summary: Extensible Output Caching use providers like distributed cache or file system cache Preload Web Applications IIS 7.5 only; avoid the startup tax for your site by preloading it. Permanent (301) Redirects are finally supported by the framework in one line of code, not two. Session State Compression Can speed up session access in a web farm environment.  Test it to see. Web Forms Features several of which mirror ASP.NET MVC advantages (viewstate, control ids) Set Meta Keywords and Description easily Granular and inheritable control over ViewState Support for more recent browsers and devices Routing (introduced in 3.5 SP1) some new features and zero web.config changes required Client ID control makes client manipulation of DOM elements much simpler. Row Selection in Data Controls fixed (id based, not row index based) FormView and ListView enhancements (less markup, more CSS compliant) New QueryExtender control makes filtering data from other Data Source Controls easy More CSS and Accessibility support Reduction of Tables and more control over output for other template controls Dynamic Data enhancements More control templates Support for inheritance in the Data Model New Attributes ASP.NET Chart Control (learn more) Lots of IDE enhancements Web Deploy tool My session will cover many but not all of these features.  Theres only an hour (3pm-4pm), and its right before the prize giveaway and movie showing, so Ill be moving quickly and most likely answering questions off-line via email after the talk. Hope to see you there! Did you know that DotNetSlackers also publishes .net articles written by top known .net Authors? We already have over 80 articles in several categories including Silverlight. Take a look: here.

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• Setting up collision using a tilemap and cocos2d

  - by James

  I'm building my first platformer using cocos2d and a tilemap. I'm having trouble coming up with a decent way of determining if the character is colliding with an object. More specifically, in which direction is the character colliding with an object. Following the tutorial here, I have made a separate "meta" layer of collidable tiles. The problem is that unless the character is in the tile, you can't detect the collision. Also, there's no way of telling WHERE the collision is occurring. The best solution would be one that could tell me if a character is up against a wall, or walking on top of a platform. However, I can't seem to figure out a good technique for this.

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• Google Translator

  An object that harnesses the power of Google's online natural language translation tools.

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• Microsoft JScript runtime error in Visual studio 2010

  - by anirudha

  There is many tool exist to debug JavaScript visual studio , firebug and some other great plugin are one of them. here I show you solution for Microsoft JScript runtime error: Object doesn't support this property or method  if you search on Google for how to debug Javascript in Visual studio. all of them told you to follow this instruction :- go to Internet option in IE > advanced tab > Browsing section > uhcheck the both option disable script debugging for IE (internet explorer) disable script debugging (others). that’s the information you read are outdate or not true these days. in visual studio you can play with JavaScript debugging even these option is check or unchecked. off-course you  can try these step in express version of visual studio. I found a little problem that my code [based on jQuery plugin] try to call some function. some of them not implement in browser so they call other so that’s fine and work in every browser. when visual studio found some function they trying to call and not implemented in browser I use to debug they tell me Microsoft JScript runtime error: Object doesn't support this property or method  they tell me again whenever I put refresh [f5] in browser. so the thing they do you never like that. see error window first whenever code is not buggy and see everytime before see the page you want to see. this behavior harsh you. there is no problem whenever you not commonly used IE but whenever you really want to debugging you got some pain too from the behavior of this. well I have some patch for that if you really like the debugging in Visual studio with IE. so if you sure that code is not buggy or you really not want to see that’s window here is trick. when you debug the JavaScript in IE choose the compact mode and they never force you to see window first who tell the thing you not want to see. How to do that for reliefs from this pain in visual studio after debug the project or website IE gone automatically launch. go to Developer tool by pressing f12 > you see window something like this:- by the way they give you document mode IE 7 as default or browser mode based on your settings. first thing is that you need to set the compact view [any ] in browser mode. and next time the error window never come again who tell you Microsoft JScript runtime error: Object doesn't support this property or method

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• How to stop camera from rotating in 2.5d platformer

  - by Artem Suchkov

  I'm stuck with a problem: I can not make my camera stop rotating after character. What I already have tried: using empty game object with rigid body and locked rotation and make it parent of camera, while player being the parent of object. Also, I've tried using few scripts from web, that did not help. Right now I'm bad with using JS in Unity (can handle JS on website, but I dont know how to integrate it for now) and practicing the basics, making easy 2.5d platformer with basic features, so I can not write code for now.

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• How is game development different from other software development?

  - by Davy8

  For a solid general purpose software developer, what specifically is different about game development, either fundamentally or just differences in degree? I've done toy games like Tic-tac-toe, Tetris, and a brute-force sudoku solver (with UI) and I'm now embarking on a mid-sized project (mid-sized for being a single developer and not having done many games) and one thing I've found with this particular project is that separation of concerns is a lot harder since everything affects state, and every object can interact with every other object in a myriad of ways. So far I've managed to keep the code reasonably clean for my satisfaction but I find that keeping clean code in non-trivial games is a lot harder than it is for my day job. The game I'm working on is turn-based and the graphics are going to be fairly simple (web-based, mostly through DOM manipulation) so real time and 3d work aren't really applicable to me, but I'd still be interested in answers regarding those if they're interesting. Mostly interested in general game logic though. P.S. Feel free to retag this, I'm not really sure what tags are applicable.

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• Rule Engine in .net

  - by user641812

  I have to import data from excel to SQL database. Excel data contains various parameters and there value like P1,P1,P4,P5 etc. I have to apply business rules Like if( P1 100 and P1 < 200) then insert the record in database. Similarly in some cases string values are also validated. Can I have any open source rule engine that contains UI to change , add , delete the rules. Am using C# to read the excel and and insert the records One more thing which is best approach: Read excel first and store every record as an object in a collection, then iterate through the collection, apply business rules on every object and then insert record in the database Or Read one record from excel apply business rule and then insert record in the database. Repeat the process for whole excel.

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• Why can't I use Unity 3D on a ATI Mobility Radeon HD 4200 Series with FGLRX drivers?

  - by user88257

  With a brand new install of 12.04 on my Dell Inspiron M5030, Unity 3D appears to load everything but the icons in the top left, and I am unable to click on anything. Unity 2D seems to works fine however. I have done nothing except install Synaptic Package manager and follow this guide to install FGLRX Drivers under Settings ? Additional Drivers, the driver shows as installed and functioning. Also after running: /usr/lib/nux/unity_support_test -p, I get this: OpenGL vendor string: ATI Technologies Inc. OpenGL renderer string: ATI Mobility Radeon HD 4200 Series OpenGL version string: 3.3.11653 Compatibility Profile Context Not software rendered: yes Not blacklisted: yes GLX fbconfig: yes GLX texture from pixmap: yes GL npot or rect textures: yes GL vertex program: yes GL fragment program: yes GL vertex buffer object: yes GL framebuffer object: yes GL version is 1.4+: yes Unity 3D supported: yes I am unsure as to what the problem is. I have tried the non-proprietary drivers, I could not get them to work either, but I would be willing to try again.

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• Physics System ignores collision in some rare cases

  - by Gajoo

  I've been developing a simple physics engine for my game. since the game physics is very simple I've decided to increase accuracy a little bit. Instead of formal integration methods like fourier or RK4, I'm directly computing the results after delta time "dt". based on the very first laws of physics : dx = 0.5 * a * dt^2 + v0 * dt dv = a * dt where a is acceleration and v0 is object's previous velocity. Also to handle collisions I've used a method which is somehow different from those I've seen so far. I'm detecting all the collision in the given time frame, stepping the world forward to the nearest collision, resolving it and again check for possible collisions. As I said the world consist of very simple objects, so I'm not loosing any performance due to multiple collision checking. First I'm checking if the ball collides with any walls around it (which is working perfectly) and then I'm checking if it collides with the edges of the walls (yellow points in the picture). the algorithm seems to work without any problem except some rare cases, in which the collision with points are ignored. I've tested everything and all the variables seem to be what they should but after leaving the system work for a minute or two the system the ball passes through one of those points. Here is collision portion of my code, hopefully one of you guys can give me a hint where to look for a potential bug! void PhysicalWorld::checkForPointCollision(Vec2 acceleration, PhysicsComponent& ball, Vec2& collisionNormal, float& collisionTime, Vec2 target) { // this function checks if there will be any collision between a circle and a point // ball contains informations about the circle (it's current velocity, position and radius) // collisionNormal is an output variable // collisionTime is also an output varialbe // target is the point I want to check for collisions Vec2 V = ball.mVelocity; Vec2 A = acceleration; Vec2 P = ball.mPosition - target; float wallWidth = mMap->getWallWidth() / (mMap->getWallWidth() + mMap->getHallWidth()) / 2; float r = ball.mRadius / (mMap->getWallWidth() + mMap->getHallWidth()); // r is ball radius scaled to match actual rendered object. if (A.any()) // todo : I need to first correctly solve the collisions in case there is no acceleration return; if (V.any()) // if object is not moving there will be no collisions! { float D = P.x * V.y - P.y * V.x; float Delta = r*r*V.length2() - D*D; if(Delta < eps) return; Delta = sqrt(Delta); float sgnvy = V.y > 0 ? 1: (V.y < 0?-1:0); Vec2 c1(( D*V.y+sgnvy*V.x*Delta) / V.length2(), (-D*V.x+fabs(V.y)*Delta) / V.length2()); Vec2 c2(( D*V.y-sgnvy*V.x*Delta) / V.length2(), (-D*V.x-fabs(V.y)*Delta) / V.length2()); float t1 = (c1.x - P.x) / V.x; float t2 = (c2.x - P.x) / V.x; if(t1 > eps && t1 <= collisionTime) { collisionTime = t1; collisionNormal = c1; } if(t2 > eps && t2 <= collisionTime) { collisionTime = t2; collisionNormal = c2; } } } // this function should step the world forward by dt. it doesn't check for collision of any two balls (components) // it just checks if there is a collision between the current component and 4 points forming a rectangle around it. void PhysicalWorld::step(float dt) { for (unsigned i=0;i<mObjects.size();i++) { PhysicsComponent &current = *mObjects[i]; Vec2 acceleration = current.mForces * current.mInvMass; float rt=dt; // stores how much more the world should advance while(rt > eps) { float collisionTime = rt; Vec2 collisionNormal = Vec2(0,0); float halfWallWidth = mMap->getWallWidth() / (mMap->getWallWidth() + mMap->getHallWidth()) / 2; // we check if there is any collision with any of those 4 points around the ball // if there is a collision both collisionNormal and collisionTime variables will change // after these functions collisionTime will be exactly the value of nearest collision (if any) // and if there was, collisionNormal will report in which direction the ball should return. checkForPointCollision(acceleration,current,collisionNormal,collisionTime,Vec2(floor(current.mPosition.x) + halfWallWidth,floor(current.mPosition.y) + halfWallWidth)); checkForPointCollision(acceleration,current,collisionNormal,collisionTime,Vec2(floor(current.mPosition.x) + halfWallWidth, ceil(current.mPosition.y) - halfWallWidth)); checkForPointCollision(acceleration,current,collisionNormal,collisionTime,Vec2( ceil(current.mPosition.x) - halfWallWidth,floor(current.mPosition.y) + halfWallWidth)); checkForPointCollision(acceleration,current,collisionNormal,collisionTime,Vec2( ceil(current.mPosition.x) - halfWallWidth, ceil(current.mPosition.y) - halfWallWidth)); // either if there is a collision or if there is not we step the forward since we are sure there will be no collision before collisionTime current.mPosition += collisionTime * (collisionTime * acceleration * 0.5 + current.mVelocity); current.mVelocity += collisionTime * acceleration; // if the ball collided with anything collisionNormal should be at least none zero in one of it's axis if (collisionNormal.any()) { collisionNormal *= Dot(collisionNormal, current.mVelocity) / collisionNormal.length2(); current.mVelocity -= 2 * collisionNormal; // simply reverse velocity along collision normal direction } rt -= collisionTime; } // reset all forces for current object so it'll be ready for later game event current.mForces.zero(); } }

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• Loading files during run time

  - by NDraskovic

  I made a content pipeline extension (using this tutorial) in XNA 4.0 game. I altered some aspects, so it serves my need better, but the basic idea still applies. Now I want to go a step further and enable my game to be changed during run time. The file I am loading trough my content pipeline extension is very simple, it only contains decimal numbers, so I want to enable the user to change that file at will and reload it while the game is running (without recompiling as I had to do so far). This file is a very simplified version of level editor, meaning that it contains rows like: 1 1,5 1,78 -3,6 Here, the first number determines the object that will be drawn to the scene, and the other 3 numbers are coordinates where that object will be placed. So, how can I change the file that contains these numbers so that the game loads it and redraws the scene accordingly? Thanks

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• Windows Azure Recipe: Consumer Portal

  - by Clint Edmonson

  Nearly every company on the internet has a web presence. Many are merely using theirs for informational purposes. More sophisticated portals allow customers to register their contact information and provide some level of interaction or customer support. But as our understanding of how consumers use the web increases, the more progressive companies are taking advantage of social web and rich media delivery to connect at a deeper level with the consumers of their goods and services. Drivers Cost reduction Scalability Global distribution Time to market Solution Here’s a sketch of how a Windows Azure Consumer Portal might be built out: Ingredients Web Role – this will host the core of the solution. Each web role is a virtual machine hosting an application written in ASP.NET (or optionally php, or node.js). The number of web roles can be scaled up or down as needed to handle peak and non-peak traffic loads. Database – every modern web application needs to store data. SQL Azure databases look and act exactly like their on-premise siblings but are fault tolerant and have data redundancy built in. Access Control (optional) – if identity needs to be tracked within the solution, the access control service combined with the Windows Identity Foundation framework provides out-of-the-box support for several social media platforms including Windows LiveID, Google, Yahoo!, Facebook. It also has a provider model to allow integration with other platforms as well. Caching (optional) – for sites with high traffic with lots of read-only data and lists, the distributed in-memory caching service can be used to cache and serve up static data at higher scale and speed than direct database requests. It can also be used to manage user session state. Blob Storage (optional) – for sites that serve up unstructured data such as documents, video, audio, device drivers, and more. The data is highly available and stored redundantly across data centers. Each entry in blob storage is provided with it’s own unique URL for direct access by the browser. Content Delivery Network (CDN) (optional) – for sites that service users around the globe, the CDN is an extension to blob storage that, when enabled, will automatically cache frequently accessed blobs and static site content at edge data centers around the world. The data can be delivered statically or streamed in the case of rich media content. Training Labs These links point to online Windows Azure training labs where you can learn more about the individual ingredients described above. (Note: The entire Windows Azure Training Kit can also be downloaded for offline use.) Windows Azure (16 labs) Windows Azure is an internet-scale cloud computing and services platform hosted in Microsoft data centers, which provides an operating system and a set of developer services which can be used individually or together. It gives developers the choice to build web applications; applications running on connected devices, PCs, or servers; or hybrid solutions offering the best of both worlds. New or enhanced applications can be built using existing skills with the Visual Studio development environment and the .NET Framework. With its standards-based and interoperable approach, the services platform supports multiple internet protocols, including HTTP, REST, SOAP, and plain XML SQL Azure (7 labs) Microsoft SQL Azure delivers on the Microsoft Data Platform vision of extending the SQL Server capabilities to the cloud as web-based services, enabling you to store structured, semi-structured, and unstructured data. Windows Azure Services (9 labs) As applications collaborate across organizational boundaries, ensuring secure transactions across disparate security domains is crucial but difficult to implement. Windows Azure Services provides hosted authentication and access control using powerful, secure, standards-based infrastructure. See my Windows Azure Resource Guide for more guidance on how to get started, including links web portals, training kits, samples, and blogs related to Windows Azure.

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• Exposing warnings\errors from data objects (that are also list returned)

  - by Oren Schwartz

  I'm exposing Data objects via service oriented assembly (which on future usages might become a WCF service). The data object is tree designed, as well as formed from allot of properties.Moreover, some services return one objects, others retrieve a list of them (thus disables throwing exceptions). I now want to expose data flow warnings and wondering what's the best way to do it having to things to consider: (1) seperation (2) ease of access. On the one hand, i want the UI team to be able to access a fields warnings (or errors) without having them mapping the field names to an external source but on the other hand, i don't want the warnings "hanged" on the object itself (as i don't see it a correct design). I tought of creating a new type of wrapper for each field, that'll expose events and they'll have to register the one's they care about (but totally not sure) I'll be happy to hear your thoughts. Could you please direct me to a respectful design pattern ? what dp will do best here ? Thank you very much!

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• Why do I get the result zero when I try to get the width of a DropDownList control in asp.net?

  - by Paul Jack

  After I click button1, it display 0, why? How can get correct width of a DropDownList control? Thanks! <%@ Page Language="C#" AutoEventWireup="true" CodeFile="Default2.aspx.cs" Inherits="Default2" % Item 1 Item 2 </div> </form> using System; using System.Collections.Generic; using System.Linq; using System.Web; using System.Web.UI; using System.Web.UI.WebControls; public partial class Default2 : System.Web.UI.Page { protected void Page_Load(object sender, EventArgs e) { } protected void Button1_Click(object sender, EventArgs e) { Button1.Text = DropDownList1.Width.Value.ToString(); } }

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• How does throwing an ArgumentNullException help?

  - by Scott Whitlock

  Let's say I have a method: public void DoSomething(ISomeInterface someObject) { if(someObject == null) throw new ArgumentNullException("someObject"); someObject.DoThisOrThat(); } I've been trained to believe that throwing the ArgumentNullException is "correct" but an "Object reference not set to an instance of an object" error means I have a bug. Why? I know that if I was caching the reference to someObject and using it later, then it's better to check for nullity when passed in, and fail early. However, if I'm dereferencing it on the next line, why are we supposed to do the check? It's going to throw an exception one way or the other. Edit: It just occurred to me... does the fear of the dereferenced null come from a language like C++ that doesn't check for you (i.e. it just tries to execute some method at memory location zero + method offset)?

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