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• Why would one overload the && and & operator?

  - by acidzombie24

  The same question goes for | and ||. Why would one overload or 'use' the & and && operator? The only use i thought of are Bitwise Ands for int base types (but not float/decimals) using & logical short circuit for bools/functions that return bool. Using the && operator usually. I cant think of any classes that use those operators. Absolutely none. I know a class might support + (and not '-') which combine two strings together. I seen an object such as datetime overload '-' so two dates can be subtracted to make a timespan (obviously you cant add two dates) but i never seen &, &&, | and || used. Does anyone know of a use? In any language?

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• Exclusive use of a Jini server during long-running call

  - by Matthew Flint

  I'm trying to use Jini, in a "Masters/Workers" arrangement, but the Worker jobs may be long running. In addition, each worker needs to have exclusive access to a singleton resource on that machine. As it stands, if a Worker receives another request while a previous request is running, then the new request is accepted and executed in a second thread. Are there any best-practices to ensure that a Worker accepts no further jobs until the current job is complete? Things I've considered: synchronize the job on the server, with a lock on the singleton resource. This would work, but is far from ideal. A call from a Master would block until the current Worker thread completes, even if other Workers become free in the meantime unregister the Worker from the registry while the job is running, then re-register when it completes. Might work OK, but something doesn't smell right with this idea... Of course, I'm quite happy to be told that there are more appropriate technologies than Jini... but I wouldn't want anything too heavyweight, like rolling out EJB containers all over the place.

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• Javascript form validation - what's lacking?

  - by box9

  I've tried out two javascript form validation frameworks - jQuery validation, and jQuery Tools validator - and I've found both of them lacking. jQuery validation lacks the clear separation between the concepts of "validating" and "displaying validation errors", and is highly inflexible when it comes to displaying dynamic error messages. jQuery Tools on the other hand lacks decent remote validation support (to check if a username exists for example). Even though jQuery validation supports remote validation, the built-in method requires the server to respond in a particular format. In both cases, any sort of asynchronous validation is a pain, as is defining rules for dependencies between multiple inputs. I'm thinking of rolling my own framework to address these shortcomings, but first I want to ask... have others experienced similar annoyances with javascript validation? What did you end up doing? What are some common validation requirements you've had which really should be catered for? And are there other, much better frameworks out there which I've missed? I'm looking primarily at jQuery-based frameworks, though well-implemented frameworks built on other libraries can still provide some useful ideas.

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• SQL query. An unusual join. DB implemented in sqlite-3

  - by user02814

  This is essentially a question about constructing an SQL query. The db is implemented with sqlite3. I am a relatively new user of SQL. I have two tables and want to join them in an unusual way. The following is an example to explain the problem. Table 1 (t1): id year name ------------------------- 297 2010 Charles 298 2011 David 300 2010 Peter 301 2011 Richard Table 2 (t2) id year food --------------------------- 296 2009 Bananas 296 2011 Bananas 297 2009 Melon 297 2010 Coffee 297 2012 Cheese 298 2007 Sugar 298 2008 Cereal 298 2012 Chocolate 299 2000 Peas 300 2007 Barley 300 2011 Beans 300 2012 Chickpeas 301 2010 Watermelon I want to join the tables on id and year. The catch is that (1) id must match exactly, but if there is no exact match in Table 2 for the year in Table 1, then I want to choose the year that is the next (lower) available. A selection of the kind that I want to produce would give the following result id year matchyr name food ------------------------------------------------- 297 2010 2010 Charles Coffee 298 2011 2008 David Cereal 300 2010 2007 Peter Barley 301 2011 2010 Richard Watermelon To summarise, id=297 had an exact match for year=2010 given in Table 1, so the corresponding line for id=297, year=2010 is chosen from Table 2. id=298, year=2011 did not have a matching year in Table 2, so the next available year (less than 2011) is chosen. As you can see, I would also like to know what that matched year (whether exactly , or inexactly) actually was. I would very much appreciate (1) an indication (yes/no answer) of whether this is possible to do in SQL alone, or whether I need to look outside SQL, and (2) a solution, if that is not too onerous.

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• Why many designs ignore normalization in RDBMS?

  - by Yosi

  I got to see many designs that normalization wasn't the first consideration in decision making phase. In many cases those designs included more than 30 columns, and the main approach was "to put everything in the same place" According to what I remember normalization is one of the first, most important things, so why is it dropped so easily sometimes? Edit: Is it true that good architects and experts choose a denormalized design while non-experienced developers choose the opposite? What are the arguments against starting your design with normalization in mind?

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• Help in (re)designing my Swing application

  - by Harihar Das

  I have developed a Swing application that controls execution of several script like jobs. I need to display the interim output of the jobs concurrently. I have followed MVC while writing the application. The application is working as expected. But off late I have the following requirements in hand: A few of the script jobs need special user privileges to execute so as to access specialized resources. There seems to be now way in Java to impersonate as a different user while running an application.[examined in this question]. Also trying to run the Swing application as a scheduled task in windows is not helping. Once started the jobs should be running even if the user logs off after starting the jobs. I am thinking of separating the execution logic from the UI and run that as a service; and introduce JMS in between the two layers so as to store/retrieve the interim the output. Note: I need to run this application on windows Any ideas on meeting my requirements will be highly appreciated.

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• Limited resource practice problems?

  - by Mark

  I'm applying for some big companies and the areas I seem to be getting burned on is problems involving limited memory, disk-space or throughput. These large companies process GBs of data every second (or more), and they need efficient ways of managing all that data. I have no experience with this as none of the projects I have worked on have grown that large. Is there a good place to learn about or practice these sorts of problems? Most of the practice-problem sites I've encountered only have problems where you have to solve something efficiently (usually involving prime numbers) but none of them limit your resources.

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• Need help in using hadoop in a Spring-Hibernate-JPA based web application [closed]

  - by John Varghese

  Possible Duplicate: Need help in using hadoop framework in a Spring-Hibernate-JPA based web application We are developing a Spring-Hibernate-JPA based web application which uses MySql as the database for storage and retrieval. We need to store and compute huge amounts of data, for that we need to use hadoop framework. How hadoop framework can be used in our web application to store and compute huge amounts of data?

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• Finding Database issue for iphone app

  - by David Liu

  I know this is a dumb question and it might not be "conceptual" but, as a self-starter I really want to know how to get connected to some sort of "commercial database"? I'm recently designing my local gas station utility app for iphone and ipad. I have absolutely no clue of find a relevant database. For example, if I want to make an app for pizza ordering in the great Chicago area. How do I get info (price, menu, location, etc.) of those pizza stores scattered all over Chicago? Can any one light something for me? I appreciated your help. **If this question is not suitable here please tell me and I will delete this post. Thank you.

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• How to learn what the industry standards/expectations are, particularly with security?

  - by Aerovistae

  For instance, I was making my first mobile web-application about a year ago, and half-way through, someone pointed me to jQuery Mobile. Obviously this induced a total revolution in my app. Rewrote everything. Now, if you're in the field long enough, maybe that seems like common knowledge, but I was totally new to it. But this set me wondering: there are so many libraries and extensions and frameworks. This seems particularly crucial in the category of security. I'm afraid I'm going to find myself doing something in a professional setting eventually (I'm still a student) and someone's going to walk over and be like, My god, you're trying to secure user data that way? Don't you know about the Gordon-Wokker crypto-magic-hash-algorithms library? Without it you may as well go plaintext. How do you know what the best ways are to maximize security? Especially if you're trying to develop something on your own...

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• Why does this static field always get initialized over-eagerly?

  - by TheSilverBullet

  I am looking at this excellent article from Jon Skeet. While executing the demo code, Jon Skeet says that we can expect three different kinds of behaviours. To quote that article: The runtime could decide to run the type initializer on loading the assembly to start with... Or perhaps it will run it when the static method is first run... Or even wait until the field is first accessed... When I try this out (on framework 4), I always get the first result. That is, the static method is initialized before the assembly is loaded. I have tried running this multiple times and get the same result. (I tried both the debug and release versions) Why is this so? Am I missing something?

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• The perfect crossfade

  - by epologee

  I find it hard to describe this problem in words, which is why I made a video (45 seconds) to illustrate it. Here's a preview of the questions, please have a look at it on Vimeo: http://vimeo.com/epologee/perfect-crossfade The issue of creating a flawless crossfade or dissolve of two images or shapes has been recurring to me in a number of fields over the last decade. First in video editing, then in Flash animation and now in iOS programming. When you start googling it, there are many workarounds to be found, but I really want to solve this without a hack this time. The summary: What is the name of the technique or curve to apply in crossfading two semi-transparent, same-colored bitmaps, if you want the resulting transparency to match the original of either one? Is there a (mathematical) function to calculate the neccessary partial transparency/alpha values during the fade? Are there programming languages that have these functions as a preset, similar to the ease in, ease out or ease in out functions found in ActionScript or Cocoa?

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• Is this the right strategy to convert an in-level order binary tree to a doubly linked list?

  - by Ankit Soni

  So I recently came across this question - Make a function that converts a in-level-order binary tree into a doubly linked list. Apparently, it's a common interview question. This is the strategy I had - Simply do a pre-order traversal of the tree, and instead of returning a node, return a list of nodes, in the order in which you traverse them. i.e return a list, and append the current node to the list at each point. For the base case, return the node itself when you are at a leaf. so you would say left = recursive_function(node.left) right = recursive_function(node.right) return(left.append(node.data)).append(right);` Is this the right approach?

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• Public Speaking in software development.

  - by mummey

  Greetings my fellow cubicle dwellers. I've found my role gradually change from "feature-maintainer" to "feature-developer". While much of the former would consist of fixing and/or updating an existing feature (and quietly grumbling about it's implementation with complete naiveté), in this new role I find: Have to communicate with immediate management to define the development requirements to turnaround the new feature Have to communicate with design to determine the user requirements of the new feature Have to communicate with QA to determine test sets for the new feature, as well as it's current state during development. Have to communicate with producers/project-managers to define remaining turnaround time as well as updates in development requirements. and finally, have to occasionally communicate with upper-management to defend the new feature and demonstrate it's minimized risk to the upcoming release. The last item is key here, and this took me a couple occasions to completely realize. In all, though, it becomes very apparent that communication skills ARE important, even or especially as such for developers who feel they 'own' the feature they're working on. All of this said, I recognize it's importance and would like to improve my skills in this area further. I enjoy one-on-one communication but find I tend to stutter a bit when speaking to any group larger than a few people I know well. Where can I find good resources to improve my own communication skills?

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• Designing a Business Rule Engine

  - by Nisha_Roy

  I have a requirement where there are 10 Rules to be applied on data in excel. If Rule 1 and Rule 2 fails rest of the rules are not checked. But if Rule 1 and Rule 2 passes the rest of all the Rules should be verified and if any errors found- they should be logged. Is there any design pattern which I can use to keep this Rule Engine flexible for adding these 10 rules and Closed for any additional chains in the Current Rule. I was thinking of something like a Decorator Pattern. Will this help me achieve that?

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• In a SSL web application, what would be the vulnerabilities of using session based authentication?

  - by Thomas C. G. de Vilhena

  I'm not sure the term even exists, so let me explain what I mean by "session based authentication" through some pseudo-code: void PerformLogin(string userName, string password) { if(AreValidCredentials(userName, password)) { Session.Set("IsAuthenticated", true); } else { Message.Show("Invalid credentials!"); } } So the above method simply verifies the provided credentials are valid and then sets a session flag to indicate that the session user is authenticated. Under plain HTTP that is obviously unsafe, because anyone could hijack the session cookie/querystring and breach security. However, under HTTPS the session cookie/querystring is protected because client-server communication is encrypted, so I believe this authentication approach would be safe, wouldn't it? I'm asking this because I want to know how authentication tickets can improve web applications security. Thanks in advance!

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• Microkernel architectural pattern and applicability for business applications

  - by Pangea

  We are in the business of building customizable web applications. We have the core team that provides what we call as the core platform (provides services like security, billing etc.) on top of which core products are built. These core products are industry specific solutions like telecom, utility etc. These core products are later used by other teams to build customer specific solutions in a particular industry. Until now we have a loose separation between platform and core product. The customer specific solutions are build by customizing 20-40% of the core offering and re-packaging. The core-platform and core products are released together as monolithic apps (ear). I am looking to improvise the current situation so that there is a cleaner separation on these 3. This allows us to have evolve each of these 3 separately etc. I've read through the Mircokernel architecture and kind of felt that I can take apply the principles in my context. But most of my reading about this pattern is always in the context of operating systems or application servers etc. I am wondering if there are any examples on how that pattern was used for architecting business applications. Or you could provide some insight on how to apply that pattern to my problem.

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• Liskov principle: violation by type-hinting

  - by Elias Van Ootegem

  According to the Liskov principle, a construction like the one below is invalid, as it strengthens a pre-condition. I know the example is pointless/nonsense, but when I last asked a question like this, and used a more elaborate code sample, it seemed to distract people too much from the actual question. //Data models abstract class Argument { protected $value = null; public function getValue() { return $this->value; } abstract public function setValue($val); } class Numeric extends Argument { public function setValue($val) { $this->value = $val + 0;//coerce to number return $this; } } //used here: abstract class Output { public function printValue(Argument $arg) { echo $this->format($arg); return $this; } abstract public function format(Argument $arg); } class OutputNumeric extends Output { public function format(Numeric $arg)//<-- VIOLATION! { $format = is_float($arg->getValue()) ? '%.3f' : '%d'; return sprintf($format, $arg->getValue()); } } My question is this: Why would this kind of "violation" be considered harmful? So much so that some languages, like the one I used in this example (PHP), don't even allow this? I'm not allowed to strengthen the type-hint of an abstract method but, by overriding the printValue method, I am allowed to write: class OutputNumeric extends Output { final public function printValue(Numeric $arg) { echo $this->format($arg); } public function format(Argument $arg) { $format = is_float($arg->getValue()) ? '%.3f' : '%d'; return sprintf($format, $arg->getValue()); } } But this would imply repeating myself for each and every child of Output, and makes my objects harder to reuse. I understand why the Liskov principle exists, don't get me wrong, but I find it somewhat difficult to fathom why the signature of an abstract method in an abstract class has to be adhered to so much stricter than a non-abstract method. Could someone explain to me why I'm not allowed to hind at a child class, in a child class? The way I see it, the child class OutputNumeric is a specific use-case of Output, and thus might need a specific instance of Argument, namely Numeric. Is it really so wrong of me to write code like this?

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• Scrum - real life example?

  - by Camilo

  I'm starting with scrum and saw many partial examples on books and tutorials, but when try to use scrum in the real life, it's not easy to write the user stories and create the product backlog. I want to see a real project with user stories, product backlog and sprint backlogs to see if I'm doing it in the correct way. Is there any open source project with a public product backlog ? Is there any shared complete user stories and product backlog from a real project?

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• Is big (as much as big) size display (Monitor) always better for Development?

  - by Jitendra Vyas

  Is bigger size display ( Monitor) always better for Development? I'm going to buy a new LCD Monitor. I mostly work in Adobe Photoshop, HTML, CSS, jQuery and Wordpress. Budget is not a problem. Many options are there for LCD Monitor SIZE My questions are Would it better for maximum size, or large size monitor are not good always? Would it better to buy 21.5 inch x 2 than one 30 inch monitor? Which monitor size would you would prefer between the size of 21.5 inch - 30 inch, if bugdet is not a problem?

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• still about perl vs python but (to me) slightly different from what has been asked [closed]

  - by B Chen

  Being a newbie to coding, I read from this site that Perl is still as viable as it has been, while Python, quoted from someone else's post, is good but just "snake oil" (not sure what this refers to exactly though). So from the responses in that post, I got the gist that Perl is good and worthy to learn. My question is - pardon me for phrasing it in this "non-programmer's" way - Which one should I learn FIRST? (I am actually currently learning R) Here below is the background info - (a) I will be using it mostly for data mining and statistics analysis (b) Will there be this "first" and "later" issue with learning either Perl or Python? That is, after I become competent with one language, would there be a need to learn the second one (for a similar task??) (c) If there should be circumstances where I must learn the second one, would learning Perl FIRST be better than learning Python? I hope to learn as much from exchanging info here, so please help provide with more than just "it depends" type of info. Great many thanks to all who choose to respond to my query.

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• Why isn't DSM for unstructured memory done today?

  - by sinned

  Ages ago, Djikstra invented IPC through mutexes which then somehow led to shared memory (SHM) in multics (which afaik had the necessary mmap first). Then computer networks came up and DSM (distributed SHM) was invented for IPC between computers. So DSM is basically a not prestructured memory region (like a SHM) that magically get's synchronized between computers without the applications programmer taking action. Implementations include Treadmarks (inofficially dead now) and CRL. But then someone thought this is not the right way to do it and invented Linda & tuplespaces. Current implementations include JavaSpaces and GigaSpaces. Here, you have to structure your data into tuples. Other ways to achieve similar effects may be the use of a relational database or a key-value-store like RIAK. Although someone might argue, I don't consider them as DSM since there is no coherent memory region where you can put data structures in as you like but have to structure your data which can be hard if it is continuous and administration like locking can not be done for hard coded parts (=tuples, ...). Why is there no DSM implementation today or am I just unable to find one?

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• As a person getting into mobile development, what's the best mobile platform in terms of profitability? [closed]

  - by Kyle Loman

  I realize this question can range very far so would love to hear any and all opinions on this. However, I'll be honest and say that I have been thinking of this in terms of most profitable. I know how this may sound either way but this is one of my main sticking points. I realize that I'm not guaranteed a single cent and success is never guaranteed but I'm going into this with the thought of making something out of it both financially and also for my own interest. I know that iOS gets a lot of attention on this front but Android commands a lot more market share. However, I know there are drawbacks to Android too, whether it's in the actual development process and programming (though I've heard conflicting reports on this, such as how easy/difficult it is for to address screen res in different devices) or the app ecosystem being flooded. But iOS's app ecosystem has been described as too saturated and harder to compete in for that reason. Since Windows Phone has fewer apps than both of those two, that might be the best place to start in order to be closer to the ground floor of the store and be noticed more? Less saturation = better chances of sales or differentiating? Something like the gold rush during the first years of the iOS App Store (not exactly but at least in concept)? Would it be that despite fewer users on the platform, there's more exposure due to less competition so that may translate to better success at sales? Plus, I know MS is in it for the long haul so I'm not too fearful of something like WebOS going away. Obviously RIM isn't very popular nowadays but I read a recent article that says Blackberry actually has the apps that make the most money, any thoughts on that: http://gigaom.com/mobile/which-mobile-oss-apps-make-most-money-surprise-its-blackberry/ Again, this is all I've heard or known about so if there's anything to add or correct here, please do. In addition, this has actually affected my next personal phone upgrade. I'm eligible for a carrier discount now and I've had my eye on the iPhone 5. However, the Lumia 920 is the one I'm holding out for and I'm open to trying an Android but I'm not sure I can wait that long for any new Nexus or even the Razr HD. Even the new Lumia in November is making me antsy, I'm so close to just getting an iPhone 5. But when I say this has affected my phone choice, I'd want to be able to carry the apps I write with me so that I'm able to pull my phone out to show people without having to carry around a second device to do so. So that's why I'd like to make my personal phone match the main platform I'm developing for. Of course, I will likely expand to other platforms if I gain any decent success but the one I target now would serve well as my personal phone I carry around so that I can use it as a marketing tool, in a sense, showing people my apps if the opportunity presents itself. So what's the best mobile platform to choose, and especially in regards to most lucrative? As said previously, this would influence my personal phone choice greatly. Thanks in advance and I hope this isn't taken the wrong way - I understand there are trade-offs and other factors that may balance this out but making some revenue is key among that. For some background, I have done software development and know programming language concepts so I'm not entirely new to it and I do get the notion of being familiar with these things so that I can translate this skill among a variety of languages but I'm currently just having difficulty choosing my first main mobile platform based on the criteria I've outlined above.

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• How Did we get from CLI to Graphics?

  - by Nathaniel Bennett

  I'm confused when looking into graphics - specifically with operating systems. I mean, how can a computer render a CLI/console along with a GUI. GUI's are completely different from Text. and How Can we have GUI windows that Display Text interfaces, ie how can we have CLI in modern Graphics Operating system - that's what I'm mainly trying to grip on to. How Do Graphic's get rendered to display? is there some sort of memory address that a GPU access which holds all pixel data, and there system's within OS's that Gather the pixel position of Windows and Widgets, along with the Z Index and rasterize them to that memory address, which then the GPU loads to the screen? How About the CLI's integrated with Graphics? how does the OS Tell the GPU that a certain part of the screen wants to display text while the rest, whats to display pixel data? it's all very confusing. Shed some light in it, will ya?

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• Do I really need to learn Python? [closed]

  - by Pouya

  These days, I see the name "Python" a lot. Mostly when I'm doing some programming on linux/mac, I see a trace of Python. I have a fair knowledge of C++ and I'm quite good at Java. I also know Delphi which comes handy sometimes. I've been good with these languages, however, I was wondering if learning Python could make it better. What does it offer that makes it worth learning? What are its key/unique advantages/features?

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