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• How to use TestAndSet() for solving the critical section problem?

  - by Dan Mantyla

  I'm studying for an exam and I'm having difficulty with a concept. This is the pseudo code I am given: int mutex = 0; do { while (TestAndSet(&mutex)); // critical section mutiex = 0; // remainder section } while (TRUE); My instructor says that only two of the three necessary conditions (mutual exclusion, progress, and bounded waiting) are met with this code, but I don't understand which one isn't being met...?? How should the code be modified to support the missing condition to solve the critical region problem? Thanks in advance for any insight!

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• Use count or have a field that tallies?

  - by Dan LaManna

  Fairly simple concept, making an extremely basic message board system and I want users to have a post count. Now I was debating on whether or not to have a tally in their row that is added each time a post by them is created, or subtracted by one each time a post of theirs is deleted. However I'm sure that performing a count query when the post count is requested would be more accurate due to unforseen circumstances (say a thread gets deleted and it doesn't lower their tally properly), however this seems like it would be less efficient to run a query EVERY time their post count is loaded, especially in the case of them having 10 posts on the same page and it lists their post count each post. Thoughts/Advice? Thanks

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• What's the deal with all of the abstract stuff?

  - by JustVenting

  I see a lot of talk about MVVM, MVC, Design Patterns etc... You know, some guy has a blog, and he spent the last six months learning about one these things and desiging a program centered around that concept and then he goes on and on about it like its better than sliced bread. I read all of this crap and I wonder, whatever happened to simple logical programming? Not self-absorbed huge frameworks of design patterns and mvc and whatever else you can think of... just simple linear programming, perhaps a few classes to encapsulate things here and there.

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• Is it a good idea to apply some basic macros to simplify code in a large project?

  - by DoctorT

  I've been working on a foundational c++ library for some time now, and there are a variety of ideas I've had that could really simplify the code writing and managing process. One of these is the concept of introducing some macros to help simplify statements that appear very often, but are a bit more complicated than should be necessary. For example, I've come up with this basic macro to simplify the most common type of for loop: #define loop(v,n) for(unsigned long v=0; v<n; ++v) This would enable you to replace those clunky for loops you see so much of: for (int i = 0, i < max_things; i++) With something much easier to write, and even slightly more efficient: loop (i, max_things) Is it a good idea to use conventions like this? Are there any problems you might run into with different types of compilers? Would it just be too confusing for someone unfamiliar with the macro(s)?

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• What is the difference between the * and the & operators in c programming?

  - by Wesley

  I am just making sure I understand this concept correctly. With the * operator, I make a new variable, which is allocated a place in memory. So as to not unnecessarily duplicate variables and their values, the & operator is used in passing values to methods and such and it actually points to the original instance of the variable, as opposed to making new copies...Is that right? It is obviously a shallow understanding, but I just want to make sure I am not getting them mixed up. Thanks!

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• is there some lightweight tecnique for adding type safety to identifier properties?

  - by shoren

  After using C++ I got used to the concept of Identifier which can be used with a class for the type, provides type safety and has no runtime overhead (the actual size is the size of the primitive). I want to do something like that, so I will not make mistakes like: personDao.find(book.getId());//I want compilation to fail personDao.find(book.getOwnerId());//I want compilation to succeed Possible solutuions that I don't like: For every entity have an entity id class wrapping the id primitive. I don't like the code bloat. Create a generic Identifier class. Code like this will not compile: void foo(Identifier book); void foo(Identifier person); Does anyone know of a better way? Is there a library with a utility such as this? Is implementing this an overkill? And the best of all, can this be done in Java without the object overhead like in C++?

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• What features do you expect from a Java (Rich) Client Framework?

  - by Peter Walser

  I'm intending to design (and provide a reference implementation for) a new Swing Rich Client Framework. My job and personal experience covers many project-specific Swing client frameworks as well as the Eclipse RCP, and every one of them had some original and clever concepts, but also drawbacks and rigid realizations. My plan is to incorporate the best of those concepts and features into a new framework whose core is very open and extendable. For my must-have-features list, I'm counting on your input and hope you can share some concept pearls & diamonds you've encountered in other frameworks, or features you always wanted to have or have in a better way. The framework is intended for very simple to very complex and sophisticated projects for clients that need full i18n for richt clients that execute some or all of the non-presentation logic on the server to be very lightweight to be easy to learn and use Thanks in advance for sharing your insights :)

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• Learning C++ from AS3

  - by grey

  I'm a decent AS3 programmer. I work in games, and that is my reason for programming. While there is much I can accomplish with Adobe AIR, my understanding at this point is that learning C++ is probably a good direction to take. I would learn a lot of valuable lower level programming if I needed it down the road, and I would have an easier time learning other C oriented languages. I see a lot of information for people looking to learn AS3 who know C++, but not the other way around. Why C++? Cross platform compatibility is important to me, so I'm not particularly interested in C# or Objective-C at this junction. I'm also aware of HaXe, and while I love the concept, after doing some research I'm worried about investing a lot of time into something so recent with limited learning resources and documentation. I'm looking for advice and resources (books, articles) related to this topic. Thanks in advance!

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• Query with multiple IN-statements but without the cartesian product

  - by Janne

  How could I make this kind of query e.g. in MySQL SELECT * FROM Table t WHERE t.a IN (1,2,3) AND t.b IN (4,5,6) AND t.c IN (7,8,9) ... so that the result would contain only the three rows: t.a|t.b|t.c ---+---+--- 1 | 4 | 7 2 | 5 | 8 3 | 6 | 9 The above query of course returns all the combinations of the values in the IN clauses but I would like to get just the ones where the first elements of each tuple match, second elements of each tuple match and so on. Is there any efficient way to do this? By the way is there some common term for this kind of query or concept? I'm having hard time coming up with the question's title because I can't put this into words..

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• Are there any Visual Studio add-ins for true 'smart tabs'?

  - by Eye of Hell

  Hello. 'Smart Tabs' concept allows to automatically insert tab character for block indentation and space characters for in-block formatting. It's described here. Unfortunately, Visual Studio's 'smart tabs' option in text editor settings just indents text on enter press. Same name, completely different and near useless thing :). So, maybe someone knows of a visual studio addin that can change how 'tab' key work so it will insert tab characters and space characters according to rules mentioned above? Any hints are welcome. Update: I need it for C++. According to comments, ReSharper can do something like this, but only for Basic and C#.

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• Overriding Magento Admin Controller, for Beginners

  - by Knowledge Craving

  In the Magento Admin section, I want to override the "Sales/Order/ShipmentController.php" controller file of the core Mage. I have tried rewriting the URL, using the "from" & "to" tags, but in vain. I don't know what is the actual & correct way of doing this, as I'm a newbie in Magento. Please anybody provide some good fundamental & correct answer, so that at least the concept gets clear. Also, if possible, please tell me, what is the actual purpose of the controller, for both the frontend & the back-end? Any help is greatly appreciated.

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• How would you code this: Grid-breaking shapes

  - by BeachRunnerJoe

  I'm a person that learns best from example. Currently, I'm diving into the field of Web Development after fifteen years of developing desktop apps. I'm still getting used to all the web technologies used for developing modern web sites and everywhere I look, I see cool little UI elements and question how they're implemented. So I thought I'd ask you, the web experts...the wexperts :) What are some straight forward or creative ways you could code this grid-breaking arrow... The basic layout for this page looks like... What would the html/css code look like? Would you split the image into multiple images or could you use a single image? I'm sure this is a really simple concept and it completely boggles me. I'm sorry if this is a strange question, remember I'm a noob! :) Thanks in advance for all your help! Here's a link to the original tutorial where I found these images

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• How secure is encryption?

  - by Stomped

  Let me preface this by saying I know nothing about encryption. I understand the basic concept of public key / private key encryption but I don't how easily it can be broken, if at all. If one were to believe the movies, encrypted data can be broken by a teenager with a decent computer in a few hours. I have a client who wants credit card information sent via email - encrypted of course, but I'm still not feeling terribly good about the idea. I feel it would be safer to store the info on the VPS, but even then its an unmanaged server and there's nobody watching it who knows much about security. So can anyone tell me if there's a safe way to store and/or send this data out? Thanks

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• Does Core Data automatically validate new values when they are set?

  - by mystify

  In this question, someone asked how to write a validation method for Core Data. I did that, and it looks cool. But one thing doesn't happen: The validation. I can easily set any "bad" value and this method doesn't get called automatically. What's the concept behind this? Must I always first call the validation method before setting any value? So would I write setter methods which call the appropriate validation method first? And if yes, what's the point of following a strict convention in how to write the validation method signature? I guess there's also some automatic way of validation, then. How to activate this?

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• In TDD, should tests be written by the person who implemented the feature under test?

  - by martin

  We run a project in which we want to solve with test driven development. I thought about some questions that came up when initiating the project. One question was: Who should write the unit-test for a feature? Should the unit-test be written by the feature-implementing programmer? Or should the unit test be written by another programmer, who defines what a method should do and the feature-implementing programmer implements the method until the tests runs? If I understand the concept of TDD in the right way, the feature-implementing programmer has to write the test by himself, because TDD is procedure with mini-iterations. So it would be too complex to have the tests written by another programmer? What would you say? Should the tests in TDD be written by the programmer himself or should another programmer write the tests that describes what a method can do?

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• Formal name of Magento’s Class Override Design Pattern?

  - by Alan Storm

  Magento is a newish (past 5 years) PHP based Ecommerce system with an architecture that's similar to the Java Spring framework (or so I've been told) One of the features of the Framework is certain classes are not directly instantiated. Rather than do something like $model = new Mage_Foo_Model_Name(); you pass an identifier into a static method on a global application object $model = Mage::getModel('foo/name'); and this instantiates the class for you. One of the wins with this approach is getModel checks a global configuration system for the foo/name identifier, and instantiates the class name it finds in the configuration system. This allows you to change the behavior of a Model system wide with a single configuration change. Is there a formal, Gang of Four or otherwise, name that describes this system/design pattern? The instantiation itself looks like a classic Factory pattern, but I'm specifically interested in the whole "override a class in the system via configuration" aspect. Is there a name/concept that covers this, or is it contained within the worldview of a Factory?

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• BST Level Traversal

  - by Dalton Conley

  Ok, so I'm trying to do a level order traversal of a binary search tree and its not working. The code below makes sense to me, but that is probably because I've been looking at it forever and I've convinced myself that it should work. void BST<T>::levelByLevel(ostream &out) { Queue<BinNodePointer> q; BinNodePointer subtreeRoot; if(myRoot == NULL) return; q.enqueue(myRoot); while(!q.empty()) { subtreeRoot = q.front(); out << subtreeRoot->data << " "; q.dequeue(); if(subtreeRoot->left != NULL) q.enqueue(subtreeRoot->left); if(subtreeRoot->right != NULL) q.enqueue(subtreeRoot->right); } } Maybe you guys could point out what I'm doing wrong because, although I understand the concept of a binary search tree, I'm not 100% on all the ins and outs.

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• How to learn web-programming (Javascript, PHP)?

  - by metal-gear-solid

  If I'm going to learn programming first time, How i should start? I don't know programming yet but I'm good at XHTML and CSS. my main aim is to learn first Javascript than second PHP. after having good command in Javascript I'll move to PHP. all these i want to learn to get good command in all areas of Wordpress design and Development. Although i can use basic javascript, jquery, PHP scripts in my projects but know i want to learn programming concept and want to get good knowledge.

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• Sending a Java object from my Android phone to my Computer

  - by TehGoose

  Hi, I was wondering what the simplest program for sending an object from my Andriod phone to my computer wirelessly (via LAN) would be. I have created Java RMI programs with a server and multiple clients, so I have a grasp of the concept. However with android I'm just not sure where to start. What I am aiming to do is send some sort of information (could simply be text) to my computer and my computer will do an action. I have the GUI interface's and the actions to be carried out all worked out, just the sending of some sort of information is getting me. Could anyone help me out?

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• Open Source PHP search engine

  - by Ravi Gupta

  I am looking for an open source search engine plugin written in php for my website(eCommerce). Before anybody answer that I have a doubt regarding the search engine. Usually search engine crawl web pages, create indexes and then use them while looking for contents. But will the same model work for eCommerce websites? Yeah, it can crawl products pages, index them but don't you think it would be better if it crawls the database directly and index the products stored in the database? And when a user search for any product, it will simply give us the rows of the table which matches the user query? May be what I am asking is a stupid question but I am new to web development, so kindly help me to understand the concept. I have looked at a search engine called Sphider but didn't get what all I have to do to make it work with an eCommerce website.

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• Is there an equivalent to C++'s "friend class" in Java?

  - by Ricket

  In C++ there is a concept of a "friend", which has access to a class's private variables and functions. So if you have: class Foo { friend class Bar; private: int x; } then any instance of the class Bar can modify any Foo instance's x member, despite it being private, because Bar is a friend of Foo. Now I have a situation in Java where this functionality would come in handy. There are three classes: Database, Modifier, Viewer. The Database is just a collection of variables (like a struct). Modifier should be "friends" with Database; that is, it should be able to read and write its variables directly. But Viewer should only be able to read Database's variables. How is this best implemented? Is there a good way to enforce Viewer's read-only access of Database?

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• Understanding reflection

  - by sdmiller

  I recently started work at a new company and a .net web application we have is built using reflection. I have only been out of school for a year and haven't worked with this concept. After studying the code... it looks like there is a single backend interface of type object that has about 20 classes that inherit from it. lots of generic gets and sets On the surface it looks like standard inheritance to me. I guess my question is, what makes this reflection? Is it because the interface is not strongly typed? Thanks

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• How to play a set of jpeg files as a movie?

  - by RJ

  I have a set of jpeg images where eacg image has an associated description. e.g. im1.jpg - suspect enters bank im7.jpg - suspect hands teller a note imj41.jpg - teller gives suspect a bag ... ... It's trivial to view these images individually and see the description but how do I play this as a movie? I need to play the images and when I encounter one with a description, display the description in a status pane. Do I need to convert the images into a movie, if so how? How do I get the player to notify me when the description frame is encountered? I'm using Windows. language doesn't matter, I just need the concept right now.

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• Use of class definitions inside a method in Java

  - by Bragaadeesh

  Hi public class TestClass { public static void main(String[] args) { TestClass t = new TestClass(); } private static void testMethod(){ class TestMethodClass{ int a; int b; int c; } TestMethodClass testMethodClass = new TestMethodClass(); } } I found out that the above piece of code is perfectly legal in Java. I have the following questions. What is the use of ever having a class definition inside a method? Will a class file be generated for TestMethodClass Its hard for me to imagine this concept in an Object Oriented manner. Having a class definition inside a behavior. Probably can someone tell me with equivalent real world examples. Thanks

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• What is the advantage of creating an enumerable object using to_enum in Ruby?

  - by Jason

  Hi, Why would you create a proxy reference to an object in Ruby, by using the to_enum method rather than just using the object directly? I cannot think of any practical use for this, trying to understand this concept & where someone might use it, but all the examples I have seen seem very trivial. For example, why use: "hello".enum_for(:each_char).map {|c| c.succ } instead of "hello".each_char.map {|c| c.succ } I know this is a very simple example, does anyone have any real-world examples? Thanks!

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