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  • Using the Coherence ConcurrentMap Interface (Locking API)

    - by jpurdy
    For many developers using Coherence, the first place they look for concurrency control is the com.tangosol.util.ConcurrentMap interface (part of the NamedCache interface). The ConcurrentMap interface includes methods for explicitly locking data. Despite the obvious appeal of a lock-based API, these methods should generally be avoided for a variety of reasons: They are very "chatty" in that they can't be bundled with other operations (such as get and put) and there are no collection-based versions of them. Locks do directly not impact mutating calls (including puts and entry processors), so all code must make explicit lock requests before modifying (or in some cases reading) cache entries. They require coordination of all code that may mutate the objects, including the need to lock at the same level of granularity (there is no built-in lock hierarchy and thus no concept of lock escalation). Even if all code is properly coordinated (or there's only one piece of code), failure during updates that may leave a collection of changes to a set of objects in a partially committed state. There is no concept of a read-only lock. In general, use of locking is highly discouraged for most applications. Instead, the use of entry processors provides a far more efficient approach, at the cost of some additional complexity.

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  • How can I convince my boss that ANSI C is inadequate for our new project?

    - by justifiably cowardly
    A few months ago, we started developing an app to control an in-house developed test equipment and record a set of measurements. It should have a simple UI, and would likely require threads due to the continuous recording that must take place. This application will be used for a few years, and shall be maintained by a number of computer science students during this period. Our boss graduated some 30 years ago (not to be taken as an offense; I have more than half that time on my back too) and has mandated that we develop this application in ANSI C. The rationale is that he is the only one that will be around the entire time, and therefore he must be able to understand what we are doing. He also ruled that we should use no abstract data types; he even gave us a list with the name of the global variables (sigh) he wants us to use. I actually tried that approach for a while, but it was really slowing me down to make sure that all pointer operations were safe and all strings had the correct size. Additionally, the number of lines of code that actually related to the problem in hand was a only small fraction of our code base. After a few days, I scrapped the entire thing and started anew using C#. Our boss has already seen the program running and he likes the way it works, but he doesn't know that it's written in another language. Next week the two of us will meet to go over the source code, so that he "will know how to maintain it". I am sort of scared, and I would like to hear from you guys what arguments I could use to support my decision. Cowardly yours,

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  • Creating a Predicate Builder extension method

    - by Rippo
    I have a Kendo UI Grid that I am currently allowing filtering on multiple columns. I am wondering if there is a an alternative approach removing the outer switch statement? Basically I want to able to create an extension method so I can filter on a IQueryable<T> and I want to drop the outer case statement so I don't have to switch column names. private static IQueryable<Contact> FilterContactList(FilterDescriptor filter, IQueryable<Contact> contactList) { switch (filter.Member) { case "Name": switch (filter.Operator) { case FilterOperator.StartsWith: contactList = contactList.Where(w => w.Firstname.StartsWith(filter.Value.ToString()) || w.Lastname.StartsWith(filter.Value.ToString()) || (w.Firstname + " " + w.Lastname).StartsWith(filter.Value.ToString())); break; case FilterOperator.Contains: contactList = contactList.Where(w => w.Firstname.Contains(filter.Value.ToString()) || w.Lastname.Contains(filter.Value.ToString()) || (w.Firstname + " " + w.Lastname).Contains( filter.Value.ToString())); break; case FilterOperator.IsEqualTo: contactList = contactList.Where(w => w.Firstname == filter.Value.ToString() || w.Lastname == filter.Value.ToString() || (w.Firstname + " " + w.Lastname) == filter.Value.ToString()); break; } break; case "Company": switch (filter.Operator) { case FilterOperator.StartsWith: contactList = contactList.Where(w => w.Company.StartsWith(filter.Value.ToString())); break; case FilterOperator.Contains: contactList = contactList.Where(w => w.Company.Contains(filter.Value.ToString())); break; case FilterOperator.IsEqualTo: contactList = contactList.Where(w => w.Company == filter.Value.ToString()); break; } break; } return contactList; } Some additional information, I am using NHibernate Linq. Also another problem is that the "Name" column on my grid is actually "Firstname" + " " + "LastName" on my contact entity. We can also assume that all filterable columns will be strings.

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  • Learning project Custom c# Cms [closed]

    - by user313378
    I want to start new project customCms, cause I think it's a good starting point to implement my collected knowledge from c#, ddd, nhibernate, mvc3, js. It will be great if I hear some guidlines from expirienced users here. I will use C# ASP.NET MVC3 razor view engine. Also I was thinking of NHibernate ORM, I dont know if using Nhibernate will cause performanse down. Initially MSSQL 2008 will be used, but using ORM layer cause that I can switch to some other db with no pain. I was thinking to create News entity which will have properties Id Name Created Updated IntroText Content Title Author ListPhotos Every input will be validated with untroub. java script on the view, and it will be validated on db level as well. Maybe it is best approach to create some interface which will be implemented by my cmsClient entity like NewsEntity. In this interface will be included everything it should be requested from my client in future. At least some stuff which are not included in entity right now, consumed data by rss feed, wcf, etc. So basically everything you think its good idea from documentating project, to coding. Everyone is welcomed to brainstorm for custom cms.

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  • How best to construct our test subjects in unit tests?

    - by Liath
    Some of our business logic classes require quite a few dependencies (in our case 7-10). As such when we come to unit test these the creation become quite complex. In most tests these dependencies are often not required (only some dependencies are required for particular methods). As a result unit tests often require a significant number of lines of code to mock up these useless dependencies (which can't be null because of null checks). For example: [Test] public void TestMethodA() { var dependency5 = new Mock<IDependency1>(); dependency5.Setup(x => x. // some setup var sut = new Sut(new Mock<IDependency1>().Object, new Mock<IDependency2>().Object, new Mock<IDependency3>().Object, new Mock<IDependency4>().Object, dependency5); Assert.SomeAssert(sut.MethodA()); } In this example almost half the test is taken up creating dependencies which aren't used. I've investigated an approach where I have a helper method. [Test] public void TestMethodA() { var dependency5 = new Mock<IDependency1>(); dependency5.Setup(x => x. // some setup var sut = CreateSut(null, null, null, null, dependency5); Assert.SomeAssert(sut.MethodA()); } private Sut CreateSut(IDependency1 d1, IDependency2 d2...) { return new Sut(d1 ?? new Mock<IDependency1>().Object, d2 ?? new Mock<IDependency2>().Object, } But these often grow very complicated very quickly. What is the best way to create these BLL classes in test classes to reduce complexity and simplify tests?

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  • Enjoy Cloud Odyssey The Oracle Movie

    - by Naresh Persaud
    If you attended Open World you may have seen the promotions for a new movie produced by Oracle. The movie is called Cloud Odyssey and it chronicles the journey of a hero to the cloud. The movie is an animated sci-fi adventure. This movie will be played at Oracle events around the world so you may soon get an invite to attend. Interesting approach to telling the cloud story. For many IT organizations, the journey to the cloud is a major initiative for end users. I am sure Homer would be proud. In fact perhaps if it is successful, I am hopeful we may see a cloud Iliad.  Below, I have embedded a trailer to the movie for your viewing pleasure. While it clearly is not the next Iron Man, it is intriguing. Hope you enjoy.  &amp;amp;amp;amp;amp;lt;span id=&amp;amp;amp;amp;amp;quot;XinhaEditingPostion&amp;amp;amp;amp;amp;quot;&amp;amp;amp;amp;amp;gt;&amp;amp;amp;amp;amp;lt;/span&amp;amp;amp;amp;amp;gt;

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  • When should I decline to make a requested change?

    - by reuscam
    I work on the software side of a company that provides custom hardware with software running on top of it. Often times the hardware is not engineered well. In those cases, I am often asked first to troubleshoot the problem - of course the symptom is always "your software crashed" or something along those lines. Just recently we had another one of these incidents where power on a USB line is not reliable, and it causes a USB device to fail. This causes a usability problem in one of our applications. I have been asked by upper management to handle this better - continually monitor the USB device, and if it disappears, then reboot, or try to reset it. Doing either of these is not guaranteed to fix anything. Ultimately, the real fix is to correct the reliability of the device from the hardware side. I could improve performance, but not to 100%, and of course I would be using my already limited time to bloat code and add yet another device monitoring thread. So with all that said, how do I make a good decision about when to say that this needs to be a hardware fix, and only a hardware fix? Can I approach this quantitatively, and come up with some sort of definitive yes/no test? I'm sure its not that easy.

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  • Data structure for grid with negative indeces

    - by The Secret Imbecile
    Sorry if this is an insultingly obvious concept, but it's something I haven't done before and I've been unable to find any material discussing the best way to approach it. I'm wondering what's the best data structure for holding a 2D grid of unknown size. The grid has integer coordinates (x,y), and will have negative indices in both directions. So, what is the best way to hold this grid? I'm programming in c# currently, so I can't have negative array indices. My initial thought was to have class with 4 separate arrays for (+x,+y),(+x,-y),(-x,+y), and (-x,-y). This seems to be a valid way to implement the grid, but it does seem like I'm over-engineering the solution, and array resizing will be a headache. Another idea was to keep track of the center-point of the array and set that as the topological (0,0), however I would have the issue of having to do a shift to every element of the grid when repeatedly adding to the top-left of the grid, which would be similar to grid resizing though in all likelihood more frequent. Thoughts?

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  • How to learn to program [on hold]

    - by user94914
    I went to a community college and got a degree in computer science, but I found out I only learn very little about programming. As a result I landed byself a office assistant work (for a year now), I want to study on my own and apply for some internship / very entry level development job. I am wondering how should a person learn to program now? I feel that I might not doing it correctly, I understand everyone has a different approach, but I am really clueless on what to do, as it seems I am 5-10 years away. 1) Read the old college programming textbook cover to cover, learn every single concepts, do all the practice problems and master them (1-2 times until error free). Currently reading this java book 2) Work on any project, keep on googling and reading tutorials (including the books on that specific language). I have been doing 1, but the progress is really slow, about 2-5 pages / hour, over a 1000+ page book, I felt really discouraged. I have a few of them to go through (data struction, analyis algorthim, computer theory, operating system.) I wonder is this the right method to do? I know it is going to take time, but I am hoping to get some advice from current programmers.

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  • Interfaces: profit of using

    - by Zapadlo
    First of all, my ubiquitous language is PHP, and I'm thinking about learning Java. So let me split my question on two closely related parts. Here goes the first part. Say I have a domain-model class. It has some getters, setters, some query methods etc. And one day I want to have a possibility to compare them. So it looks like: class MyEntity extends AbstractEntity { public function getId() { // get id property } public function setId($id) { // set id property } // plenty of other methods that set or retrieve data public function compareTo(MyEntity $anotherEntity) { // some compare logic } } If it would have been Java, I should have implemented a Comparable interface. But why? Polymorphism? Readbility? Or something else? And if it was PHP -- should I create Comparable interface for myself? So here goes the second part. My colleague told me that it is a rule of thumb in Java to create an interface for every behavioral aspect of the class. For example, if I wanted to present this object as a string, I should state this behaviour by something like implements Stringable, where in case of PHP Stringable would look like: interface Stringable { public function __toString(); } Is that really a rule of thumb? What benefits are gained with this approach? And does it worth it in PHP? And in Java?

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  • Oracle ADF Mobile

    - by rituchhibber
    We are happy to announce that Oracle ADF Mobile is now available for our customers.Oracle ADF Mobile enables developer to build applications that install and run on both iOS and Android devices from one source code.Development is done with JDeveloper and ADF and leverages Java and HTML5 technologies, while keeping the same visual and declarative approach ADF is known for.Please Click here to read more about the Oracle ADF Mobile release and learn more on our OTN Page. Feature Highlights: Java - Oracle brings a Java VM embedded with each application so you can develop all your business logic in the platform neutral language you know and love! (Yes, even iOS!) JDBC - Since we give you Java, we also provide JDBC along with a SQLite driver and engine that also supports encryption out of the box. Multi-Platform - Truly develop your application only once and deploy to multiple platforms. iOS and Android platforms are supported for both phone and tablet. Flexible - You can decide how to implement the UI: Use existing server-based UI framework like JSF. Use your own favorite HTML5 framework like JQuery. Use our declarative HTML5 component set provided with the framework. Device Feature Access - You can get access to device features from either Java or JavaScript to invoke features like camera, GPS, email, SMS, contacts, etc. Secure - ADF Mobile provides integrated security that works with your server back-end as well. Whether you’re using remote URLs, local HTML or AMX, you can secure any/all of your features with a single consistent login page. Since we also give you SQLite encryption, we are assured that your data is safe. Rapid - Using the same development techniques that ADF developers are already used to, you can quickly create mobile applications without ever learning another language!ADF Mobile XML or AMX for short, provides all the normal input and layout controls you expect and we also add charts/maps/gauges along with it to provide a very comprehensive UI controls. You can also mix and match any of the three for ultimate flexibility!

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  • If the bug is 5+ years old, then is it a feature?

    - by Job
    Allow me to add details: I work at an institutional place with many coders, testers, QA analysts, product owners, etc. and here is something that bugs me: We have been able to sell crappy (albeit pretty functional) software for over a decade. It has many features and the product is competitive, but there are a some serious bugs out there, as well as thousands of "paper cuts" - little annoyances that clients need to get used to. It pains me to look at some of the things because I firmly believe that if computers do not help to make our lives easier, then we should not use them. I have confidence in my colleagues - they are smart, able, and can improve things when the focus is on doing that. But, it can be difficult to file bugs against some old functionality without seeing them closed or forgotten. "It worked like that for ions" is a typical answer. Also, when QA does regression, they tend to look for anything that is different as much as anything that does not seem right. So, a fix to an old problem can be written up as a bug, because "it has been like that before even my time". The young coder in me thinks: rewrite this freaking thing! As someone who had the opportunity to be close to sales, clients, I want to give a benefit of a doubt to this approach. I am interested in your opinion/experience as well. Please try to consider risk, cost-to-benefit, and other non-technical factors.

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  • Dealing with bilingual(spoken language) code?

    - by user1525
    So I've got to work with this set of code here for a re-write, and it's written by people who speak both English and French. Here's a snapshot of what I'm talking about (only, about 4000 lines of this) function refreshDest(FormEnCours,dest,hotel,duration) { var GateEnCours; GateEnCours = FormEnCours.gateway_dep.options[FormEnCours.gateway_dep.selectedIndex].value; if (GateEnCours == "") { FormEnCours.dest_dep.length = 0 } else if (FormEnCours.dest_dep != null && FormEnCours.dest_dep.type && FormEnCours.dest_dep.value != "ALL") { if (Destinations[GateEnCours] == null || Destinations[GateEnCours].length == 0) { RetreiveDestinations(FormEnCours,GateEnCours,dest,hotel,duration); } else { refreshDestSuite(FormEnCours,GateEnCours,dest,hotel,duration); } } } function refreshDuration(FormEnCours,GateEnCours,DestEnCours,hotel,duration) { // Refresh durations var FlagMoinsDe5Jours = ""; var Flag5a10jours = ""; var Flag11a16jours = ""; var FlagPlusDe16Jours = ""; ....... Is there any approach that I, as a speaker of only one of these languages, can use to make this entire process a lot less painful for both figuring out what everything does, and then refactoring it?

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  • Should I amortize scripting cost via bytecode analysis or multithreading?

    - by user18983
    I'm working on a game sort of thing where users can write arbitrary code for individual agents, and I'm trying to decide the best way to divide up computation time. The simplest option would be to give each agent a set amount of time and skip their turn if it elapses without an action being decided upon, but I would like people to be able to write their agents decision functions without having to think too much about how long its taking unless they really want to. The two approaches I'm considering are giving each agent a set number of bytecode instructions (taking cost into account) each timestep, and making players deal with the consequences of the game state changing between blocks of computation (as with Battlecode) or giving each agent it's own thread and giving each thread equal time on the processor. I'm about equally knowledgeable on both concurrency and bytecode stuff, which is to say not very, so I'm wondering which approach would be best. I have a clearer idea of how I'd structure things if I used bytecode, but less certainty about how to actually implement the analysis. I'm pretty sure I can work up a concurrency based system without much trouble, but I worry it will be messier with more overhead and will add unnecessary complexity to the project.

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  • RPGMakerVX - Changing item_max?

    - by rackemup420
    I've been working on a game for awhile and I am developing it with RPG Maker VX. I came to a point where I needed to... I guess for lack of better explanation... Limit the key items to just 1. So I started looking through my scripts and found (in Game_Party): #-------------------------------------------------------------------------- # * Get Maximum Number of Items Possessed #-------------------------------------------------------------------------- def max_item_number(item) return 99 end and added below it: #-------------------------------------------------------------------------- # * Get Maximum Number of Key Items Possessed #-------------------------------------------------------------------------- def max_key_item_number(item) return 1 end and right below that is: #-------------------------------------------------------------------------- # * Determine if Maximum Number of Items Are Possessed #-------------------------------------------------------------------------- def item_max?(item) item_number(item) >= max_item_number(item) end So I changed the last one too: #-------------------------------------------------------------------------- # * Determine if Maximum Number of Items Are Possessed #-------------------------------------------------------------------------- def item_max?(item) if key_item? == true item_number(item) >= max_key_item_number(item) end if key_item? == false item_number(item) >= max_item_number(item) end end Now this seemed to not affect anything (that I could tell). I tested it and its still the same as before I touched anything. I am new to developing games and relatively new to scripting for them. Is this approach even close to what I want to do? Any help is greatly apprecieated!

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  • iPhone Serialization problem

    - by Jenicek
    Hi, I need to save my own created class to file, I found on the internet, that good approach is to use NSKeyedArchiver and NSKeyedUnarchiver My class definition looks like this: @interface Game : NSObject <NSCoding> { NSMutableString *strCompleteWord; NSMutableString *strWordToGuess; NSMutableArray *arGuessedLetters; //This array stores characters NSMutableArray *arGuessedLettersPos; //This array stores CGRects NSInteger iScore; NSInteger iLives; NSInteger iRocksFallen; BOOL bGameCompleted; BOOL bGameOver; } I've implemented methods initWithCoder: and encodeWithCoder: this way: - (id)initWithCoder:(NSCoder *)coder { if([coder allowsKeyedCoding]) { strCompleteWord = [[coder decodeObjectForKey:@"CompletedWord"] copy]; strWordToGuess = [[coder decodeObjectForKey:@"WordToGuess"] copy]; arGuessedLetters = [[coder decodeObjectForKey:@"GuessedLetters"] retain]; // arGuessedLettersPos = [[coder decodeObjectForKey:@"GuessedLettersPos"] retain]; iScore = [coder decodeIntegerForKey:@"Score"]; iLives = [coder decodeIntegerForKey:@"Lives"]; iRocksFallen = [coder decodeIntegerForKey:@"RocksFallen"]; bGameCompleted = [coder decodeBoolForKey:@"GameCompleted"]; bGameOver = [coder decodeBoolForKey:@"GameOver"]; } else { strCompleteWord = [[coder decodeObject] retain]; strWordToGuess = [[coder decodeObject] retain]; arGuessedLetters = [[coder decodeObject] retain]; // arGuessedLettersPos = [[coder decodeObject] retain]; [coder decodeValueOfObjCType:@encode(NSInteger) at:&iScore]; [coder decodeValueOfObjCType:@encode(NSInteger) at:&iLives]; [coder decodeValueOfObjCType:@encode(NSInteger) at:&iRocksFallen]; [coder decodeValueOfObjCType:@encode(BOOL) at:&bGameCompleted]; [coder decodeValueOfObjCType:@encode(BOOL) at:&bGameOver]; } return self; } - (void)encodeWithCoder:(NSCoder *)coder { if([coder allowsKeyedCoding]) { [coder encodeObject:strCompleteWord forKey:@"CompleteWord"]; [coder encodeObject:strWordToGuess forKey:@"WordToGuess"]; [coder encodeObject:arGuessedLetters forKey:@"GuessedLetters"]; //[coder encodeObject:arGuessedLettersPos forKey:@"GuessedLettersPos"]; [coder encodeInteger:iScore forKey:@"Score"]; [coder encodeInteger:iLives forKey:@"Lives"]; [coder encodeInteger:iRocksFallen forKey:@"RocksFallen"]; [coder encodeBool:bGameCompleted forKey:@"GameCompleted"]; [coder encodeBool:bGameOver forKey:@"GameOver"]; } else { [coder encodeObject:strCompleteWord]; [coder encodeObject:strWordToGuess]; [coder encodeObject:arGuessedLetters]; //[coder encodeObject:arGuessedLettersPos]; [coder encodeValueOfObjCType:@encode(NSInteger) at:&iScore]; [coder encodeValueOfObjCType:@encode(NSInteger) at:&iLives]; [coder encodeValueOfObjCType:@encode(NSInteger) at:&iRocksFallen]; [coder encodeValueOfObjCType:@encode(BOOL) at:&bGameCompleted]; [coder encodeValueOfObjCType:@encode(BOOL) at:&bGameOver]; } } And I use these methods to archive and unarchive data: [NSKeyedArchiver archiveRootObject:currentGame toFile:strPath]; Game *currentGame = [NSKeyedUnarchiver unarchiveObjectWithFile:strPath]; I have two problems. 1) As you can see, lines with arGuessedLettersPos is commented, it's because every time I try to encode this array, error comes up(this archiver cannot encode structs), and this array is used for storing CGRect structs. I've seen solution on the internet. The thing is, that every CGRect in the array is converted to an NSString (using NSStringFromCGRect()) and then saved. Is it a good approach? 2)This is bigger problem for me. Even if I comment this line and then run the code successfully, then save(archive) the data and then try to load (unarchive) them, no data is loaded. There aren't any error but currentGame object does not have data that should be loaded. Could you please give me some advice? This is first time I'm using archivers and unarchivers. Thanks a lot for every reply.

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  • CSG operations on implicit surfaces with marching cubes [SOLVED]

    - by Mads Elvheim
    I render isosurfaces with marching cubes, (or perhaps marching squares as this is 2D) and I want to do set operations like set difference, intersection and union. I thought this was easy to implement, by simply choosing between two vertex scalars from two different implicit surfaces, but it is not. For my initial testing, I tried with two spheres circles, and the set operation difference. i.e A - B. One circle is moving and the other one is stationary. Here's the approach I tried when picking vertex scalars and when classifying corner vertices as inside or outside. The code is written in C++. OpenGL is used for rendering, but that's not important. Normal rendering without any CSG operations does give the expected result. void march(const vec2& cmin, //min x and y for the grid cell const vec2& cmax, //max x and y for the grid cell std::vector<vec2>& tri, float iso, float (*cmp1)(const vec2&), //distance from stationary circle float (*cmp2)(const vec2&) //distance from moving circle ) { unsigned int squareindex = 0; float scalar[4]; vec2 verts[8]; /* initial setup of the grid cell */ verts[0] = vec2(cmax.x, cmax.y); verts[2] = vec2(cmin.x, cmax.y); verts[4] = vec2(cmin.x, cmin.y); verts[6] = vec2(cmax.x, cmin.y); float s1,s2; /********************************** ********For-loop of interest****** *******Set difference between **** *******two implicit surfaces****** **********************************/ for(int i=0,j=0; i<4; ++i, j+=2){ s1 = cmp1(verts[j]); s2 = cmp2(verts[j]); if((s1 < iso)){ //if inside circle1 if((s2 < iso)){ //if inside circle2 scalar[i] = s2; //then set the scalar to the moving circle } else { scalar[i] = s1; //only inside circle1 squareindex |= (1<<i); //mark as inside } } else { scalar[i] = s1; //inside neither circle } } if(squareindex == 0) return; /* Usual interpolation between edge points to compute the new intersection points */ verts[1] = mix(iso, verts[0], verts[2], scalar[0], scalar[1]); verts[3] = mix(iso, verts[2], verts[4], scalar[1], scalar[2]); verts[5] = mix(iso, verts[4], verts[6], scalar[2], scalar[3]); verts[7] = mix(iso, verts[6], verts[0], scalar[3], scalar[0]); for(int i=0; i<10; ++i){ //10 = maxmimum 3 triangles, + one end token int index = triTable[squareindex][i]; //look up our indices for triangulation if(index == -1) break; tri.push_back(verts[index]); } } This gives me weird jaggies: It looks like the CSG operation is done without interpolation. It just "discards" the whole triangle. Do I need to interpolate in some other way, or combine the vertex scalar values? I'd love some help with this. A full testcase can be downloaded HERE EDIT: Basically, my implementation of marching squares works fine. It is my scalar field which is broken, and I wonder what the correct way would look like. Preferably I'm looking for a general approach to implement the three set operations I discussed above, for the usual primitives (circle, rectangle/square, plane)

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  • Safe, standard way to load images in ListView on a different thread?

    - by Po
    Before making this question, I have searched and read these ones: http://stackoverflow.com/questions/541966/android-how-do-i-do-a-lazy-load-of-images-in-listview http://stackoverflow.com/questions/1409623/android-issue-with-lazy-loading-images-into-a-listview My problem is I have a ListView, where: Each row contains an ImageView, whose content is to be loaded from the internet Each row's view is recycled as in ApiDemo's List14 What I want ultimately: Load images lazily, only when the user scrolls to them Load images on different thread(s) to maintain responsiveness My current approach: In the adapter's getView() method, apart from setting up other child views, I launch a new thread that loads the Bitmap from the internet. When that loading thread finishes, it returns the Bitmap to be set on the ImageView (I do this using AsyncTask or Handler). Because I recycle ImageViews, it may be the case that I first want to set a view with Bitmap#1, then later want to set it to Bitmap#2 when the user scrolls down. Bitmap#1 may happen to take longer than Bitmap#2 to load, so it may end up overwriting Bitmap#2 on the view. I solve this by maintaining a WeakHashMap that remembers the last Bitmap I want to set for that view. Below is somewhat a pseudocode for my current approach. I've ommitted other details like caching, just to keep the thing clear. public class ImageLoader { // keeps track of the last Bitmap we want to set for this ImageView private static final WeakHashMap<ImageView, AsyncTask> assignments = new WeakHashMap<ImageView, AsyncTask>(); /** Asynchronously sets an ImageView to some Bitmap loaded from the internet */ public static void setImageAsync(final ImageView imageView, final String imageUrl) { // cancel whatever previous task AsyncTask oldTask = assignments.get(imageView); if (oldTask != null) { oldTask.cancel(true); } // prepare to launch a new task to load this new image AsyncTask<String, Integer, Bitmap> newTask = new AsyncTask<String, Integer, Bitmap>() { protected void onPreExecute() { // set ImageView to some "loading..." image } protected Bitmap doInBackground(String... urls) { return loadFromInternet(imageUrl); } protected void onPostExecute(Bitmap bitmap) { // set Bitmap if successfully loaded, or an "error" image if (bitmap != null) { imageView.setImageBitmap(bitmap); } else { imageView.setImageResource(R.drawable.error); } } }; newTask.execute(); // mark this as the latest Bitmap we want to set for this ImageView assignments.put(imageView, newTask); } /** returns (Bitmap on success | null on error) */ private Bitmap loadFromInternet(String imageUrl) {} } Problem I still have: what if the Activity gets destroyed while some images are still loading? Is there any risk when the loading thread calls back to the ImageView later, when the Activity is already destroyed? Moreover, AsyncTask has some global thread-pool underneath, so if lengthy tasks are not canceled when they're not needed anymore, I may end up wasting time loading things users don't see. My current design of keeping this thing globally is too ugly, and may eventually cause some leaks that are beyond my understanding. Instead of making ImageLoader a singleton like this, I'm thinking of actually creating separate ImageLoader objects for different Activities, then when an Activity gets destroyed, all its AsyncTask will be canceled. Is this too awkward? Anyway, I wonder if there is a safe and standard way of doing this in Android. In addition, I don't know iPhone but is there a similar problem there and do they have a standard way to do this kind of task? Many thanks.

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  • Chaining CSS classes in IE6 - Trying to find a jQuery solution?

    - by Mike Baxter
    Right, perhaps I ask the impossible? I consider myself fairly new to Javscript and jQuery, but that being said, I have written some fairly complex code recently so I am definitely getting there... however I am now possed with a rather interesting issue at my current freelance contract. The previous web coder has taken a Grid-960 approach to the HTML and as a result has used chained classes to style many of the elements. The example below is typical of what can be found in the code: <div class='blocks four-col-1 orange highlight'>Some content</div> And in the css there will be different declarations for: (not actual css... but close enough) .blocks {margin-right:10px;} .orange {background-image:url(someimage.jpg);} .highlight {font-weight:bold;} .four-col-1 {width:300px;} and to make matters worse... this is in the CSS: .blocks.orange.highlight {background-colour:#dd00ff;} Anyone not familiar with this particular bug can read more on it here: http://www.ryanbrill.com/archives/multiple-classes-in-ie/ it is very real and very annoying. Without wanting to go into the merrits of not chaining classes (I told them this, but it is no longer feasible to change their approach... 100 hand coded pages into a 150 page website, no CMS... sigh) and without the luxury of being able to change the way these blocks are styled... can anyone advise me on the complexity and benefits between any of my below proposed approaches or possible other options that would adequately solve this problem. Potential Solution 1 Using conditional comments I am considering loading a jquery script only for IE6 that: Reads the class of all divs in a certain section of the page and pushes to an array creates empty boxes off screen with only one of the classes applied at a time Reads the applied CSS values for each box Re-applies these styles to the individual box, somehow bearing in mind the order in which they are called and overwriting conflicting instructions as required Potential Solution 2 read the class of all divs in a certain section of the page and push to an array Scan the document for links to style sheets Ajax grab the stylesheets and traverse looking for matching names to those in class array Apply styles as needed Potential Solution 3 Create an IE6 only stylesheet containing the exact style to be applied as a unique name (ie: class='blocks orange highlight' becomes class='blocks-orange-highlight') Traverse the document in IE6 and convert all spaces in class declarations to hyphens and reapply classes based on new style name Summary: Solution 1 allows the people at this company to apply any styles in the future and the script will adjust as needed. However it does not allow for the chained style to be added, only the individual style... it is also processor intensive and time consuming, but also the most likely to be converted into a plugin that could be used the world over Solution 2 is a potential nightmare to code. But again will allow for an endless number of updates without breaking Solution 3 will require someone at the companty to hardcode the new styles every time they make a change, and if they don't, IE6 will break. Ironically the site, whilst needing to conform to IE6 in a limited manner, does not need to run wihtout javascript (they've made the call... have JS or go away), so consider all jQuery and JS solutions to be 'game on'. Did I mention how much i hate IE6? Anyway... any thoughts or comments would be appreciated. I will continue to develop my own solution and if I discover one that can be turned into a jQuery plugin I will post it here in the comments. Regards, Mike.

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  • In Ruby, how to I read memory values from an external process?

    - by grg-n-sox
    So all I simply want to do is make a Ruby program that reads some values from known memory address in another process's virtual memory. Through my research and basic knowledge of hex editing a running process's x86 assembly in memory, I have found the base address and offsets for the values in memory I want. I do not want to change them; I just want to read them. I asked a developer of a memory editor how to approach this abstract of language and assuming a Windows platform. He told me the Win32API calls for OpenProcess, CreateProcess, ReadProcessMemory, and WriteProcessMemory were the way to go using either C or C++. I think that the way to go would be just using the Win32API class and mapping two instances of it; One for either OpenProcess or CreateProcess, depending on if the user already has th process running or not, and another instance will be mapped to ReadProcessMemory. I probably still need to find the function for getting the list of running processes so I know which running process is the one I want if it is running already. This would take some work to put all together, but I am figuring it wouldn't be too bad to code up. It is just a new area of programming for me since I have never worked this low level from a high level language (well, higher level than C anyways). I am just wondering of the ways to approach this. I could just use a bunch or Win32API calls, but that means having to deal with a bunch of string and array pack and unpacking that is system dependant I want to eventually make this work cross-platform since the process I am reading from is produced from an executable that has multiple platform builds, (I know the memory address changes from system to system. The idea is to have a flat file that contains all memory mappings so the Ruby program can just match the current platform environment to the matching memory mapping.) but from the looks of things I'll just have to make a class that wraps whatever is the current platform's system shared library memory related function calls. For all I know, there could already exist a Ruby gem that takes care of all of this for me that I am just not finding. I could also possibly try editing the executables for each build to make it so whenever the memory values I want to read from are written to by the process, it also writes a copy of the new value to a space in shared memory that I somehow have Ruby make an instance of a class that is a pointer under the hood to that shared memory address and somehow signal to the Ruby program that the value was updated and should be reloaded. Basically a interrupt based system would be nice, but since the purpose of reading these values is just to send to a scoreboard broadcasted from a central server, I could just stick to a polling based system that sends updates at fixed time intervals. I also could just abandon Ruby altogether and go for C or C++ but I do not know those nearly as well. I actually know more x86 than C++ and I only know C as far as system independent ANSI C and have never dealt with shared system libraries before. So is there a gem or lesser known module available that has already done this? If not, then any additional information as to how to accomplish this would be nice. I guess, long story short, how do I do all this? Thanks in advance, Grg PS: Also a confirmation that those Win32API calls should be aimed at the kernel32.dll library would be nice.

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  • CSS: Horizontal, comma-separated list with fixed <li> width

    - by hello
    Hello, I would like to achieve the following structure: [gfhtfg..., kgjrfg..., asd, mrhgf, ] ^-------^ ^-------^ ^-------^ ^-------^ X X X X (X = a fixed length) I've got a <div> with a fixed length, and inside it an horizontal, comma-separated list (ul) of links. The <li> elements should have a fixed width, and so if the links exceed a fixed length an ellipsis will be shown (using the text-overflow property). I know two ways to make a list horizontal. One is using display: inline and the other using the float property. With the first approach, I can't set a fixed width because the CSS specification doesn't allow setting the width of inline elements. The second approach creates a mess :O Setting float on the <a> element, intending to limit the width there, separates it from the commas. There are no browser-compatibility issues, I only have to support WebKit. I included the code I attempted to work with: <!DOCTYPE html> <html lang="en"> <head> <title>a title</title> <style> body { font-family: arial; font-size: 10pt; } div { height: 30px; width: 300px; background: #eee; border: 1px solid #ccc; text-align: center; } ul { margin: 0px; padding: 0px; } ul li:after { content: ","; } ul li:last-child:after { content: ""; } ul li a { text-decoration: none; color: #666; } ul li { margin: 0px; padding: 0px; list-style: none; overflow: hidden; text-overflow: ellipsis; -webkit-text-overflow: ellipsis; /* Inline elements can't have a width (and they shouldn't according to the specification */ display: inline; width: 30px; } </style> </head> <body> <div> <ul> <li><a href="#">a certain link</a></li> <li><a href="#">link</a></li> <li><a href="#">once again</a></li> <li><a href="#">another one</a></li> </ul> </div> </body> </html> Thank you.

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  • XNA: Load and read a XML file?

    - by Rosarch
    I'm having difficulty doing this seemingly simple task. I want to load XML files with the same ease of loading art assets: content = new ContentManager(Services); content.RootDirectory = "Content"; background = content.Load<Texture2D>("images\\ice"); I'm not sure how to do this. This tutorial seems helpful, but how do I get a StorageDevice instance? I do have something working now, but it feels pretty hacky: public IDictionary<string, string> Get(string typeName) { IDictionary<String, String> result = new Dictionary<String, String>(); xmlReader.Read(); // get past the XML declaration string element = null; string text = null; while (xmlReader.Read()) { switch (xmlReader.NodeType) { case XmlNodeType.Element: element = xmlReader.Name; break; case XmlNodeType.Text: text = xmlReader.Value; break; } if (text != null && element != null) { result[element] = text; text = null; element = null; } } return result; } I apply this to the following XML file: <?xml version="1.0" encoding="utf-8" ?> <zombies> <zombie> <health>100</health> <positionX>23</positionX> <positionY>12</positionY> <speed>2</speed> </zombie> </zombies> And it is able to pass this unit test: internal virtual IPersistentState CreateIPersistentState(string fullpath) { IPersistentState target = new ReadWriteXML(File.Open(fullpath, FileMode.Open)); return target; } /// <summary> ///A test for Get with one zombie. ///</summary> //[TestMethod()] public void SimpleGetTest() { string fullPath = "C:\\pathTo\\Data\\SavedZombies.xml"; IPersistentState target = CreateIPersistentState(fullPath); string typeName = "zombie"; IDictionary<string, string> expected = new Dictionary<string, string>(); expected["health"] = "100"; expected["positionX"] = "23"; expected["positionY"] = "12"; expected["speed"] = "2"; IDictionary<string, string> actual = target.Get(typeName); foreach (KeyValuePair<string, string> entry in expected) { Assert.AreEqual(entry.Value, expected[entry.Key]); } } Downsides to the current approach: file loading is done poorly, and matching keys to values seems like it's way more effort than necessary. Also, I suspect this approach would fall apart with more than one entry in the XML.

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  • Representing game states in Tic Tac Toe

    - by dacman
    The goal of the assignment that I'm currently working on for my Data Structures class is to create a of Quantum Tic Tac Toe with an AI that plays to win. Currently, I'm having a bit of trouble finding the most efficient way to represent states. Overview of current Structure: AbstractGame Has and manages AbstractPlayers (game.nextPlayer() returns next player by int ID) Has and intializes AbstractBoard at the beginning of the game Has a GameTree (Complete if called in initialization, incomplete otherwise) AbstractBoard Has a State, a Dimension, and a Parent Game Is a mediator between Player and State, (Translates States from collections of rows to a Point representation Is a StateConsumer AbstractPlayer Is a State Producer Has a ConcreteEvaluationStrategy to evaluate the current board StateTransveralPool Precomputes possible transversals of "3-states". Stores them in a HashMap, where the Set contains nextStates for a given "3-state" State Contains 3 Sets -- a Set of X-Moves, O-Moves, and the Board Each Integer in the set is a Row. These Integer values can be used to get the next row-state from the StateTransversalPool SO, the principle is Each row can be represented by the binary numbers 000-111, where 0 implies an open space and 1 implies a closed space. So, for an incomplete TTT board: From the Set<Integer> board perspective: X_X R1 might be: 101 OO_ R2 might be: 110 X_X R3 might be: 101, where 1 is an open space, and 0 is a closed space From the Set<Integer> xMoves perspective: X_X R1 might be: 101 OO_ R2 might be: 000 X_X R3 might be: 101, where 1 is an X and 0 is not From the Set<Integer> oMoves perspective: X_X R1 might be: 000 OO_ R2 might be: 110 X_X R3 might be: 000, where 1 is an O and 0 is not Then we see that x{R1,R2,R3} & o{R1,R2,R3} = board{R1,R2,R3} The problem is quickly generating next states for the GameTree. If I have player Max (x) with board{R1,R2,R3}, then getting the next row-states for R1, R2, and R3 is simple.. Set<Integer> R1nextStates = StateTransversalPool.get(R1); The problem is that I have to combine each one of those states with R1 and R2. Is there a better data structure besides Set that I could use? Is there a more efficient approach in general? I've also found Point<-State mediation cumbersome. Is there another approach that I could try there? Thanks! Here is the code for my ConcretePlayer class. It might help explain how players produce new states via moves, using the StateProducer (which might need to become StateFactory or StateBuilder). public class ConcretePlayerGeneric extends AbstractPlayer { @Override public BinaryState makeMove() { // Given a move and the current state, produce a new state Point playerMove = super.strategy.evaluate(this); BinaryState currentState = super.getInGame().getBoard().getState(); return StateProducer.getState(this, playerMove, currentState); } } EDIT: I'm starting with normal TTT and moving to Quantum TTT. Given the framework, it should be as simple as creating several new Concrete classes and tweaking some things.

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  • Open XML SDK 2.0 - Split table to new power point slide when content flows off current slide

    - by amurra
    I have a bunch of data that I need to export from a website to a power point presentation and have been using Open XML SDK 2.0 to perform this task. I have a power point presentation that I am putting through Open XML SDK 2.0 Productivity Tool to generate the template code that I can use to recreate the export. On one of those slides I have a table and the requirement is to add data to that table and break that table across multiple slides if the table exceeds the bottom of the slide. The approach I have taken is to determine the height of the table and if it exceeds the height of the slide, move that new content into the next slide. I have read Bryan and Jones blog on adding repeating data to a power point slide, but my scenario is a little different. They use the following code: A.Table tbl = current.Slide.Descendants<A.Table>().First(); A.TableRow tr = new A.TableRow(); tr.Height = heightInEmu; tr.Append(CreateDrawingCell(imageRel + imageRelId)); tr.Append(CreateTextCell(category)); tr.Append(CreateTextCell(subcategory)); tr.Append(CreateTextCell(model)); tr.Append(CreateTextCell(price.ToString())); tbl.Append(tr); imageRelId++; This won't work for me since they know what height to set the table row to since it will be the height of the image, but when adding in different amounts of text I do not know the height ahead of time so I just set tr.Heightto a default value. Here is my attempt at figuring at the table height: A.Table tbl = tableSlide.Slide.Descendants<A.Table>().First(); A.TableRow tr = new A.TableRow(); tr.Height = 370840L; tr.Append(PowerPointUtilities.CreateTextCell("This"); tr.Append(PowerPointUtilities.CreateTextCell("is")); tr.Append(PowerPointUtilities.CreateTextCell("a")); tr.Append(PowerPointUtilities.CreateTextCell("test")); tr.Append(PowerPointUtilities.CreateTextCell("Test")); tbl.Append(tr); tableSlide.Slide.Save(); long tableHeight = PowerPointUtilities.TableHeight(tbl); Here are the helper methods: public static A.TableCell CreateTextCell(string text) { A.TableCell tableCell = new A.TableCell( new A.TextBody(new A.BodyProperties(), new A.Paragraph(new A.Run(new A.Text(text)))), new A.TableCellProperties()); return tableCell; } public static Int64Value TableHeight(A.Table table) { long height = 0; foreach (var row in table.Descendants<A.TableRow>() .Where(h => h.Height.HasValue)) { height += row.Height.Value; } return height; } This correctly adds the new table row to the existing table, but when I try and get the height of the table, it returns the original height and not the new height. The new height meaning the default height I initially set and not the height after a large amount of text has been inserted. It seems the height only gets readjusted when it is opened in power point. I have also tried accessing the height of the largest table cell in the row, but can't seem to find the right property to perform that task. My question is how do you determine the height of a dynamically added table row since it doesn't seem to update the height of the row until it is opened in power point? Any other ways to determine when to split content to another slide while using Open XML SDK 2.0? I'm open to any suggestion on a better approach someone might have taken since there isn't much documentation on this subject.

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  • Architecture for Qt SIGNAL with subclass-specific, templated argument type

    - by Barry Wark
    I am developing a scientific data acquisition application using Qt. Since I'm not a deep expert in Qt, I'd like some architecture advise from the community on the following problem: The application supports several hardware acquisition interfaces but I would like to provide an common API on top of those interfaces. Each interface has a sample data type and a units for its data. So I'm representing a vector of samples from each device as a std::vector of Boost.Units quantities (i.e. std::vector<boost::units::quantity<unit,sample_type> >). I'd like to use a multi-cast style architecture, where each data source broadcasts newly received data to 1 or more interested parties. Qt's Signal/Slot mechanism is an obvious fit for this style. So, I'd like each data source to emit a signal like typedef std::vector<boost::units::quantity<unit,sample_type> > SampleVector signals: void samplesAcquired(SampleVector sampleVector); for the unit and sample_type appropriate for that device. Since tempalted QObject subclasses aren't supported by the meta-object compiler, there doesn't seem to be a way to have a (tempalted) base class for all data sources which defines the samplesAcquired Signal. In other words, the following won't work: template<T,U> //sample type and units class DataSource : public QObject { Q_OBJECT ... public: typedef std::vector<boost::units::quantity<U,T> > SampleVector signals: void samplesAcquired(SampleVector sampleVector); }; The best option I've been able to come up with is a two-layered approach: template<T,U> //sample type and units class IAcquiredSamples { public: typedef std::vector<boost::units::quantity<U,T> > SampleVector virtual shared_ptr<SampleVector> acquiredData(TimeStamp ts, unsigned long nsamples); }; class DataSource : public QObject { ... signals: void samplesAcquired(TimeStamp ts, unsigned long nsamples); }; The samplesAcquired signal now gives a timestamp and number of samples for the acquisition and clients must use the IAcquiredSamples API to retrieve those samples. Obviously data sources must subclass both DataSource and IAcquiredSamples. The disadvantage of this approach appears to be a loss of simplicity in the API... it would be much nicer if clients could get the acquired samples in the Slot connected. Being able to use Qt's queued connections would also make threading issues easier instead of having to manage them in the acquiredData method within each subclass. One other possibility, is to use a QVariant argument. This necessarily puts the onus on subclass to register their particular sample vector type with Q_REGISTER_METATYPE/qRegisterMetaType. Not really a big deal. Clients of the base class however, will have no way of knowing what type the QVariant value type is, unless a tag struct is also passed with the signal. I consider this solution at least as convoluted as the one above, as it forces clients of the abstract base class API to deal with some of the gnarlier aspects of type system. So, is there a way to achieve the templated signal parameter? Is there a better architecture than the one I've proposed?

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