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  • How does throwing an ArgumentNullException help?

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

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  • How do we keep dependent data structures up to date?

    - by Geo
    Suppose you have a parse tree, an abstract syntax tree, and a control flow graph, each one logically derived from the one before. In principle it is easy to construct each graph given the parse tree, but how can we manage the complexity of updating the graphs when the parse tree is modified? We know exactly how the tree has been modified, but how can the change be propagated to the other trees in a way that doesn't become difficult to manage? Naturally the dependent graph can be updated by simply reconstructing it from scratch every time the first graph changes, but then there would be no way of knowing the details of the changes in the dependent graph. I currently have four ways to attempt to solve this problem, but each one has difficulties. Nodes of the dependent tree each observe the relevant nodes of the original tree, updating themselves and the observer lists of original tree nodes as necessary. The conceptual complexity of this can become daunting. Each node of the original tree has a list of the dependent tree nodes that specifically depend upon it, and when the node changes it sets a flag on the dependent nodes to mark them as dirty, including the parents of the dependent nodes all the way down to the root. After each change we run an algorithm that is much like the algorithm for constructing the dependent graph from scratch, but it skips over any clean node and reconstructs each dirty node, keeping track of whether the reconstructed node is actually different from the dirty node. This can also get tricky. We can represent the logical connection between the original graph and the dependent graph as a data structure, like a list of constraints, perhaps designed using a declarative language. When the original graph changes we need only scan the list to discover which constraints are violated and how the dependent tree needs to change to correct the violation, all encoded as data. We can reconstruct the dependent graph from scratch as though there were no existing dependent graph, and then compare the existing graph and the new graph to discover how it has changed. I'm sure this is the easiest way because I know there are algorithms available for detecting differences, but they are all quite computationally expensive and in principle it seems unnecessary so I'm deliberately avoiding this option. What is the right way to deal with these sorts of problems? Surely there must be a design pattern that makes this whole thing almost easy. It would be nice to have a good solution for every problem of this general description. Does this class of problem have a name?

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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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  • Why don't we just fix Javascript?

    - by Jan Meyer
    Javascript sucks because of a few fatalities well pointed out by Douglas Crockford. We talk a lot about it. But the point here is, why we don't fix it? Coffeescript of course does that and a lot more. But the question here is another: if we provide a webservice that can convert one version of Javascript to the next, and so on, we can keep the language up to date. Such a conversion allows old code to run, albeit with an ever-increasing startup delay, as newer browsers convert old code to the new syntax. To avoid that delay, the site only needs to take the output of the code-transform and paste it in! The effort has immediate benefits for those businesses interested in the results. The rest can sleep tight: their code will continue to run. If we provide backward code-transformation also, then elder browsers can also run ANY new code! Migration scripts should be created by those that make changes to a language. Today they don't, which is in itself a fundamental omission! It should be am obvious part of their job to provide them, as their job isn't really done without them. The onus of making it work should be on them. With this system Any site will be able to run in Any browser, but new code will run best on the newest browsers. This way we reap the benefit of an up-to-date and productive development environment, where today we suffer, supposedly because of yesterday. This is a misconception. We are all trapped in committee-thinking, and we drag along things that only worsen our performance over time! We cause an ever increasing complexity that is hard to underestimate. Javascript is easily fixed. The fact is we don't. As an example, I have seen Patrick Michaud tackle the migration problem in PmWiki. It included forward migration scripts. Whenever syntax changes were made, a migration script was added to transform pages to the new syntax. As far as I know, ALL migrations have worked flawlessly. In other words, we don't tackle the migration problem, we just drag it along. We are incompetent! And why is that? Because technically incompetent people feel they must decide for us. Because they are incompetent, fear rules them. They are obnoxiously conservative, and we suffer the consequence of bad leadership. But the competent don't need to play by the same rules. They can (and must) change them. They are the path forward. It is about time to leave the past behind, and pursue the leanest meanest, no, eternal functionality. That would in and of itself revolutionize programming. So, why don't we stop whining and fix programming? Begin with Javascript and change the world. Even if the browser doesn't hook into this system, coders could. So language updaters should take it upon them to provide migration scripts. Once they exist, browsers may take advantage of them.

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  • Is it worth it to switch from home-grown remote command interface to using JMX

    - by Sam Goldberg
    Without knowing too much about JMX, I've always assumed that it would be the best approach for building in remote management to our standalone Java server application. Our server application has some minimal remote control capability, using text commands sent via TCP/IP socket to it. Using the home grown approach, it is fairly to add a new command. (Just create new command text, and the code to handle that in the message receiver). On the other hand, we have hardly implemented any commands, even though there are many things we would like to be able to execute remotely. I am trying to weigh the value of moving to incorporating JMX (learning it, and building the interfaces), versus just sticking with the home-grown approach. Does anyone have any experience or advice regarding changing an existing application to use JMX?

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  • How do Tortoise svn handle concurrent file updation

    - by sabithpocker
    I don't know much about Tortoise SVN, but have been using it for a while :) I understand that it is capable of managing concurrent users on same file, but how does it do that? I am working on a file that another user is using concurrently and he committed couple of times before me, Now my files doesnt have the changes he made. Every time i end up in such a situation I gets a conflict and I am stuck. So is there something else I should do instead of just committing and causing conflict. Is it safe to do a update first and then commit ? Will I lose my local changes in this case? Please dont beat me up if this is somthing basic, A link to some tutorial will be useful in that case :)

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  • Non-Profit Technololgy for Non-Profits?

    - by TomJ
    I've been looking around for a way to give back to the community, but I haven't found my right fit yet, so an idea came to mind: A non-profit technology "company" that targets non-profits. Do these exist? I've been doing some google searches and can only find software that is targeted for non-profits that is created by for-profit companies or that charges what I believe to be an outrages amount, conferences directed towards non-profits and technology they may use -- or articles complaining about the digital divide and how non-profits view technology as key but dont have the funds or the knowledge to employ it. Pseudo "Business Model" An open source 501(3)(c) organization that targets directly targets non-profits to fill the "digital divide." Most services would be free and consulting fees would be charged for customization. Donations would be accepted and government grants would be sought after. This would enable non-profits to keep pace with the for-profits in the technology sector, but at little to no cost. Perhaps the first "industry" to be targeted would be those that fill key social needs like unemployment, or food banks.

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  • Publish/Subscribe/Request for exchange of big, complex, and confidential data?

    - by Morten
    I am working on a project where a website needs to exchange complex and confidential (and thus encrypted) data with other systems. The data includes personal information, technical drawings, public documents etc. We would prefer to avoid the Request-Reply pattern to the dependent systems (and there are a LOT of them), as that would create an awful lot of empty traffic. On the other hand, I am not sure that a pure Publisher/Subscriber pattern would be apropriate -- mainly because of the complex and bulky nature of the data to be exchanged. For that reason we have discussed the possibility of a "publish/subscribe/request" solution. The Publish/Subscribe part would be to publish a message to the dependent systems, that something is ready for pickup. The actual content is then picked up by old-school Request-Reply action. How does this sound to you?? Regards, Morten

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  • Customizing the NUnit GUI for data-driven testing

    - by rwong
    My test project consists of a set of input data files which is fed into a piece of legacy third-party software. Since the input data files for this software are difficult to construct (not something that can be done intentionally), I am not going to add new input data files. Each input data file will be subject to a set of "test functions". Some of the test functions can be invoked independently. Other test functions represent the stages of a sequential operation - if an earlier stage fails, the subsequent stages do not need to be executed. I have experimented with the NUnit parametrized test case (TestCaseAttribute and TestCaseSourceAttribute), passing in the list of data files as test cases. I am generally satisfied with the the ability to select the input data for testing. However, I would like to see if it is possible to customize its GUI's tree structure, so that the "test functions" become the children of the "input data". For example: File #1 CheckFileTypeTest GetFileTopLevelStructureTest CompleteProcessTest StageOneTest StageTwoTest StageThreeTest File #2 CheckFileTypeTest GetFileTopLevelStructureTest CompleteProcessTest StageOneTest StageTwoTest StageThreeTest This will be useful for identifying the stage that failed during the processing of a particular input file. Is there any tips and tricks that will enable the new tree layout? Do I need to customize NUnit to get this layout?

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  • What is a good stopword in full text indexation?

    - by Benoit
    When you go to the Appendix D in Oracle Text Reference they provide lists of stopwords used by Oracle Text when indexing table contents. When I see the English list, nothing puzzles me. But the reason why the French list includes moyennant (French for in view of which) for example is unclear. Oracle has probably thought it through more than once before including it. How would you constitute a list of appropriate stopwords if you were to design an indexer?

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  • Suggestions for connecting .NET WPF GUI with Java SE Server aoo

    - by Sam Goldberg
    BACKGROUND We are building a Java (SE) trading application which will be monitoring market data and sending trade messages based on the market data, and also on user defined configuration parameters. We are planning to provide the user with a thin client, built in .NET (WPF) for managing the parameters, controlling the server behavior, and viewing the current state of the trading. The client doesn't need real-time updates; it will instead update the view once every few seconds (or whatever interval is configured by the user). The client has about 6 different operations it needs to perform with the server, for example: CRUD with configuration parameters query subset of the data receive updates of current positions from server It is possible that most of the different operations (except for receiving data) are just different flavors of managing the configuration parameters, but it's too early in our analysis for us to be sure. To connect the client with the server, we have been considering using: SOAP Web Service RESTful service building a custom TCP/IP based API (text or xml) (least preferred - but we use this approach with other applications we have) As best as I understand, pros and cons of the different web service flavors are: SOAP pro: totally automated in .NET (and Java), modifying server side interface require no code changes in communication layer, just running refresh on Web Service reference to regenerate the classes. con: more overhead in the communication layer sending more text, etc. We're not using J2EE container so maybe doesn't work so well with J2SE REST pro: lighter weight, less data. Has good .NET and Java support. (I don't have any real experience with this, so don't know what other benefits it has.) con: client will not be automatically aware if there are any new operations or properties added (?), so communication layer needs to be updated by developer if server interface changes. con: (both approaches) Server cannot really push updates to the client at regular intervals (?) (However, we won't mind if client polls the server to get updates.) QUESTION What are your opinions on the above options or suggestions for other ways to connect the 2 parts? (Ideally, we don't want to put much work into the communication layer, because it's not the significant part of the application so the more off-the-shelf and automated the better.)

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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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  • Should I start making connections even if I'm not ready for a job yet?

    - by James
    The first job is always the hardest to get and I'm not exception. I'm 23 years old and I have no college degree but planned on going to college this year if all goes well (CS of course). I'm self-studying java right now. I know most of the topics related to the language besides the more advanced topics and I'm beginning to look at open source projects. I would like to find a job (at least a part time job) after a year or two when I'll gain more experience and learn more about java technologies and other technologies that interest me. Finding a job will be a bit difficult because most of the people (or a lot of them at least) at my current age already have 2 years or more of experience, so I will be somewhat disadvantaged. Should I start building connections and joining websites such as linkedin ? I never bothered to look into it because I'm not much of a social network person. If I start contributing to open source projects and create personal projects for 2 years could I apply for jobs that require 1-2 years of experience? Does this experience count ?

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  • What threading pratice is good 90% of the time?

    - by acidzombie24
    Since my SO thread was closed i guess i can ask it here. What practice or practices are good 90% of the time when working with threading with multiple cores? Personally all i have done was share immutable classes and pass (copy) data to a queue to the destine thread. Note: This is for research and when i say 90% of the time i dont mean it is allowed to fail 10% of the time (thats ridiculous!) i mean 90% it is a good solution while the other 10% it is not so desirable due to implementation or efficiently reasons (or plainly another technique fits the problem domain a lot better).

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  • Rationale behind freeware projects

    - by VexXtreme
    I've seen some freeware projects in the past where the author(s) invested a significant amount of their personal time and resources and never even considered charging for the software. A lot of these projects were donation based, and from what I've heard, donationware can never be a viable business model (even to simply support development costs) because most people choose not to donate if given an option. A lot of these projects eventually shut down because their authors could not sustain them further. Granted, some people simply like making the community happy (or something), but if you're struggling to keep your project alive, why not charge some small amount such as $10 simply to stay operational? If people find your software useful (and a lot of people found those projects VERY useful) they won't have a problem paying such a small amount. The question is: if you have a popular app that people like and download in great numbers, why not put a price tag on it? Why do it for free?

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  • session management: verifying a user's log-in state

    - by good_computer
    I am storing sessions in my database. Everytime a user logs in, I create a new row corresponding to the new session, generate a new session id and send it as a cookie to the browser. My session data looks something like this: { 'user_id': 1234 'user_name': 'Sam' ... } When a request comes, I check whether a cookie with a session id is sent. If it is, I fetch session data from my database (or memcache) corresponding to that session id. When the user logs out, I remove the session data from my database (and memcache), and delete the cookie from the user's browser too. Notice that in my session data, I don't have something like logged_in: true. This is because if I find a session record in the database (or memcache) I deduce that the user is logged in, and if there is no session record found, the user is not logged in. My question is: is this the right approach? Should I have a logged_in key in my session data? Is there any possibility that a session record may be present on the server where the corresponding user is actually NOT logged in? Are there any security implications in having or not having such a key?

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  • Duplication of code (backend and javascript - knockout)

    - by Michal B.
    We have a new developer in our team. He seems a smart guy (he just came in so I cannot really judge). He started with implementing some small enhancements in the project (MVC3 web application using javascript - jquery and knockout). Let's say we have two values: A - quite complex calculation C - constant B = A + C On the screen there is value B and user can change it (normal texbox). When B changes, A changes as well because C is constant. So there is linear dependency between A and B. Now, all the calculations are done in the backend, but we need to recalculate A as user changes B (in js, I would use knockout). I thought about storing old A and B and when B changes by 10 then we know that new A will be old A + 10. He says this is dirty, because it's duplication of code (we make use of the fact that they are dependent and according to him that should be only in one place in our app). I understand it's not ideal, but making AJAX request after every key press seems a bit too much. It's a really small thing and I would not post if we haven't had long discussion about it. How do you deal with such problems? Also I can imagine that using knockout implies lots of calculations on the client side, which very often leads to duplication of the same calculations from the backend. Does anyone have links to some articles/thoughts on this topic?

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  • What is a good support knowledge base tool?

    - by Guillaume
    I have been searching for a tool to help my team organize its knowledge for resolving recurring support cases. I know this question will probably be closed, but I'll try my change anyway because I know that I can have some good answers about that. Context: our team is developing and supporting an huge applications (lots of different screens and workflow processes. We already have a good tool for managing our documentation, but we are struggling with support cases. Support action involve often quite a lot of manual steps to fix stuff and the knowledge for these actions is more 'oral transmission' than modern tools. We need an efficient way to store them in a knowledge base to be able to retrieve similar cases based on patterns (a stacktrace, an error message, a component name, a workflow step, ...) and ranked by similarity. Our wiki search is not very powerful when it come to this kind of search and the team members don't want to 'waste' time writing a report that will never be found... Do you know efficient knowledge base tool for this kind of use case ?

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  • Strategy for building an application to replace a large spreadsheet

    - by Dan Walmsley
    I'm working on an application that is going to replace a rather large spreadsheet. The spreadsheet is used to budget purchases and things like that. It is the largest spreadsheet I have ever seen, and it required a lot of manual data entry, so this application is going to automate much of that. But as I'm working on this I've noticed its slow going. And I got to thinking this must be a common thing to do many companies will start with something like a spreadsheet, then when they get too big to maintain that, they will get a custom application built. So is there anything out there ( a framework or similar ) that does this sort of thing, migrating a spreadsheet to a custom application. I've had a quick Google but not really seen the kind of thing that I'm looking for. It's too late for this project, but I thought it would be worth having a look for next time. How do you guys tackle this problem?

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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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  • Why is implementing copy-paste in a touch screen based smartphone such a big deal?

    - by EpsilonVector
    I'm not entirely sure this is on-topic, but it definitely needs a programmer's understanding to be answered, and deals with general development (for a specific scenario) as opposed to a specific piece of code. In a way it also translates into "what are the challenges in doing X in a touch screen app", and similar questions have been asked here in the past. So here it is: When Apple didn't implement copy-pasting on the iPhone since version 1 I just assumed it was a UI issue- they were waiting until they figured out a good UI for it. But now the idea is out there, and Microsoft still released Windows Phone 7 without copy-pasting, promising it'll be ready in a few months. My question is: why does this takes a few months to implement? Are there some technological challenges that are unique to programming for a touch screen that I'm not familiar with?

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  • What are some reasonable arguments in favor of closed source software? [closed]

    - by Goma
    I like a technology (including programming language) but its platform is closed sourece and many times I meet people who ask me, "why do you use a closed source platform, why not use an open source alternative? If there is something wrong it should be with the closed source not with the open source, (as they say)". Actually I don't know how to answer their question. Could anyone tell me a good answer? Why do you use a closed source platform?

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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 do I learn to develop financial software?

    - by Jack Smartie
    I would like to know what I have to learn to become a financial software developer in the area of brokerage/investment software. I apologize if this question is off topic. I'm not sure where to put it. What programming language(s) is most commonly used in the financial world? Financial software requires highly accurate and redundant features. Are these programming skills learned through experience, a class, or a book?

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  • What is the best Video Conference integrated solution for Us? [closed]

    - by Andrei B
    we are trying to integrate a simple Video Conferencing (open source) solution into our existing application which is written in C++ and it runs on Linux. I am currently looking at using Ekiga (formely known as GnomeMeeting) or Homer Conferencing (short: Homer). My plan is to "integrate" an existing Video Conferencing client into our existing software. Please give me recommendation on which 3rd party application or library to use to add video conferencing feature to our application. PS: Please don't close this question. I asked it on StackOverflow and it got closed, so where am I supposed to ask this question? If not here, then whats the point of asking lol.

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