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  • How can one manage thousands of IF...THEN...ELSE rules?

    - by David
    I am considering building an application, which, at its core, would consist of thousands of if...then...else statements. The purpose of the application is to be able to predict how cows move around in any landscape. They are affected by things like the sun, wind, food source, sudden events etc. How can such an application be managed? I imagine that after a few hundred IF-statements, it would be as good as unpredictable how the program would react and debugging what lead to a certain reaction would mean that one would have to traverse the whole IF-statement tree every time. I have read a bit about rules engines, but I do not see how they would get around this complexity.

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  • What guidelines do you suggest for using Objective-C Properties?

    - by adarsha
    Objective-C 2.0 introduced properties. While I personally think properties are nice addition to the language, I have seen a trend of making every instance variable as a property. Apple sample codes are no exceptions to this. I believe this is against the spirit of OOP, and since it exposes a lot more implementation details of a class to the client than they need to know. What guidelines do you suggest for the proper usage properties in Objective C?

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  • Determining Cost of API Calls

    - by Sam
    [This is a cross-post originally posted by me in SO. I think the question is more appropriate here.] I was going through the adwords API and came across their rate sheet - http://code.google.com/apis/adwords/docs/ratesheet.html . They charge $0.25 per 1000 API units and under the 'Operation Costs' sections list the cost (in API units) of different API calls. I am curious - based on what factors do they (and others API developers) calculate the cost of an API call? Is there any simple formula or a standard way to determine this? Note: When I say 'cost' of an API call, I don't mean the money but the API units. For example, how do you determine one API call costs 100 'units' and another 1000?

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  • C++ and function pointers assessment: lack of inspiration

    - by OlivierDofus
    I've got an assessment to give to my students. It's about C++ and function pointers. Their skill is middle: it the first year of a programming school after bachelor. To give you something precise, here's a sample of a solution of one of 3 exercices they had to do in 30 minutes (the question was: "here's a version of a code that could be written with function pointers, write down the same thing but with function pointers"): typedef void (*fcPtr) (istream &); fcPtr ArrayFct [] = { Delete , Insert, Swap, Move }; void HandleCmd (const string && Cmd) { string AvalaibleCommands ("DISM"); string::size_type Pos; istringstream Flux (Cmd); char CodeOp; Flux >> CodeOp; Pos = AvalaibleCommands.find (toupper (CodeOp)); if (Pos != string::npos) { ArrayFct [Pos](Flux); } } Any idea where I could find some inspiration? Some of the students have understood the principles, even though it's very hard for them to write C++ code. I know them, I know they're clever, and I'm pretty sure they should be very good project managers. So, writing C++ code is not that important after all. Understanding is the most important part (IMHO). I'm wondering about maybe break the habits, and give half of the questions about the principle, or even better, give some sample in other language and ask them why it's better to use function pointers instead of classical programming (usually a big switch case). Any idea where I could look? Find some inspiration?

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  • Best approach to accessing multiple data source in a web application

    - by ced
    I've a base web application developed with .net technologies (asp.net) used into our LAN by 30 users simultanousley. From this web application I've developed two verticalization used from online users. In future i expect hundreds users simultanousley. Our company has different locations. Each site use its own database. The web application needs to retrieve information from all existing databases. Currently there are 3 database, but it's not excluded in the future expansion of new offices. My question then is: What is the best strategy for a web application to retrieve information from different databases (which have the same schema) whereas the main objective performance data access and high fault tolerance? There are case studies in the literature that I can take as an example? Do you know some good documents to study? Do you have any tips to implement this task so efficient? Intuitively I would say that two possible strategy are: perform queries from different sources in real time and aggregate data on the fly; create a repository that contains the union of the entities of interest and perform queries directly on repository;

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  • Clients with multiple proxy and multithreading callbacks

    - by enzom83
    I created a sessionful web service using WCF, and in particular I used the NetTcpBinding binding. In addition to methods to initiate and terminate a session, other methods allow the client to send to one or more tasks to be performed (the results are returned via callback, so the service is duplex), but they also allow you to know the status of the service. Assuming you activate the same service on multiple endpoints, and assuming that the client knows these endpoints (for example, it could maintain a List of endpoints), the client should connect with one or more replicas of the same service. The client periodically updates the status of the service, so when it needs to perform a new task (the task is submitted by the user via UI), it selects the service currently less loaded and sends the task to it. Periodically, the client also initiates a maintenance procedure in order to disconnect from one or more overloaded service and in order to connect with new services. I created a client proxy using the svcutil tool. I wish each proxy can be used simultaneously by different threads, for example, in addition to the thread that submits the tasks using a proxy, there are also the following two threads which act periodically: a thread that periodically sends a request to the service in order to obtain the updated state; a thread that periodically selects a proxy to close and instantiates a new proxy to replace the closed one. To achieve these objectives, is it sufficient to create an array of proxies and manage their opening and closing in separate threads? I think I read that the proxy method calls are thread safe, so I would not need to perform a lock before requesting updates to the service. However, when the maintenance procedure (which is activated on its own thread) decides to close a proxy, should I perform a lock? Finally, each proxy is also associated with an object that implements the callback interface for the service: are the callbacks (invoked on the client) executed on different threads on the client? I would like to wrap the management of the proxy in one or more classes so that it can then easily manage within a WPF application.

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  • What are the roles of a Software Delivery Manager

    - by Rich
    I have been told about a position that may be open to me - the role of a Software Delivery Manager. From what I understand this role does not already exist within my organisation. To be perfectly honest I'm not quite sure what a Software Delivery Manager's roles are. I have a few ideas and would appreciate some input around whether they are correct or not, or if there is anything missing: ensure the quality of the software being delivered document the relationships between the components being delivered ensure that the delivery of these components does not break other components ensure that the components being developed make the best use of the environments they are being deployed in being on-hand during software deliveries (though not actually performing the delivery of software, rather giving the Go) I have also been told that the role would include some software development work (which is important to me being a developer at heart!) - is there software development specifically associated with the role of Software Delivery Manager or is this more likely to just be a case of helping the team out when time is short?

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  • Storing Attendance Data in database

    - by Ali Abbas
    So i have to store daily attendance of employees of my organisation from my application . The part where I need some help is, the efficient way to store attendance data. After some research and brain storming I came up with some approaches . Could you point me out which one is the best and any unobvious ill effects of the mentioned approaches. The approaches are as follows Create a single table for whole organisation and store empid,date,presentstatus as a row for every employee everyday. Create a single table for whole organisation and store a single row for each day with a comma delimited string of empids which are absent. I will generate the string on my application. Create different tables for each department and follow the 1 method. Please share your views and do mention any other good methods

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  • Understanding the problem when things break in production

    - by bitcycle
    Scenario: You push to production The push broke multiple things That same build did not break qa or dev As a developer, you don't have prod access. There is lots of pressure from above to get things working agian. Specifics: PHP/MVC application that is API-driven in Zend. Deployed to a few servers. My question: While investigating, lets say I have a hunch that something is wrong. But, I don't know for sure. And, of course, I can't test things in production. If I have a suggested fix based on that hunch, would it be wise to try and apply it and see if it works, before understanding what the problem is?

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  • Taking Object Oriented development to the next level

    - by Songo
    Can you mention some advanced OO topics or concepts that one should be aware of? I have been a developer for 2 years now and currently aiming for a certain company that requires a web developer with a minimum experience of 3 years. I imagine the interview will have the basic object oriented topics like (Abstraction, Polymorphism, Inheritance, Design patterns, UML, Databases and ORMs, SOLID principles, DRY principle, ...etc) I have these topics covered, but what I'm looking forward to is bringing up topics such as Efferent Coupling, Afferent Coupling, Instability, The law of Demeter, ...etc. Till few days ago I never knew such concepts existed (maybe because I'm a communication engineer basically not a CS graduate.) Can you please recommend some more advanced topics concerning object oriented programming?

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  • How to explain OOP to a matlab programmer?

    - by Oak
    I have a lot of friends who come from electrical / physical / mechanical engineering background, and are curious about what is "OOP" all about. They all know Matlab quite well, so they do have basic programming background; but they have a very hard time grasping a complex type system which can benefit from the concepts OOP introduces. Can anyone propose a way I can try to explain it to them? I'm just not familiar with Matlab myself, so I'm having troubles finding parallels. I think using simple examples like shapes or animals is a bit too abstract for those engineers. So far I've tried using a Matrix interface vs array-based / sparse / whatever implementations, but that didn't work so well, probably because different matrix types are already well-supported in Matlab.

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  • Optimize strategies for xml parsing?

    - by Future2020
    I am looking for general optimization tips and guidelines for xml parsing. One of the optimization strategies is of course selecting the "right" parser. A detailed comparison between the available parsers for ios can be found here http://www.raywenderlich.com/553/how-to-chose-the-best-xml-parser-for-your-iphone-project. However, I am currently trying to investigate general guidelines and tips on how to optimize by payloads to increase the performance as possible. This question is similar to (a question I have posted in the context of ios) but I have not got a sufficient answer. So this question is not in the context of any particular programming language.

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  • Does the use of mongodb enhance extending/changing database driven applications?

    - by developer10214
    When an application is created which need to store data, an SQL database is used very often. So did I in a lot of asp.net applications. The resulting applications have often an ORM like the entity framework and maybe a business layer. So when such an application needs to be extended(let's say you have to add a comment property to an object), you have to change/extend the database, then the ORM and the business layer and so on. To deploy the changes you have to update the target database and the application. I know that things like code first and fluent can make this approach easier. I tried mongodb, I only used the standard driver and I had to extend some objects and all I had to do was changing the code. So it feels that such approaches are much easier to realize when using mongodb. I don't have much experience with larger applications an mongodb. I know that a SQL database or mongodb doesn't fit for all needs and both have their pros and cons. I want to know if my feeling is right, if yes I would choose rather choose mongodb than SQL database.

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  • What's the relationship between meta-circular interpreters, virtual machines and increased performance?

    - by Gomi
    I've read about meta-circular interpreters on the web (including SICP) and I've looked into the code of some implementations (such as PyPy and Narcissus). I've read quite a bit about two languages which made great use of metacircular evaluation, Lisp and Smalltalk. As far as I understood Lisp was the first self-hosting compiler and Smalltalk had the first "true" JIT implementation. One thing I've not fully understood is how can those interpreters/compilers achieve so good performance or, in other words, why is PyPy faster than CPython? Is it because of reflection? And also, my Smalltalk research led me to believe that there's a relationship between JIT, virtual machines and reflection. Virtual Machines such as the JVM and CLR allow a great deal of type introspection and I believe they make great use it in Just-in-Time (and AOT, I suppose?) compilation. But as far as I know, Virtual Machines are kind of like CPUs, in that they have a basic instruction set. Are Virtual Machines efficient because they include type and reference information, which would allow language-agnostic reflection? I ask this because many both interpreted and compiled languages are now using bytecode as a target (LLVM, Parrot, YARV, CPython) and traditional VMs like JVM and CLR have gained incredible boosts in performance. I've been told that it's about JIT, but as far as I know JIT is nothing new since Smalltalk and Sun's own Self have been doing it before Java. I don't remember VMs performing particularly well in the past, there weren't many non-academic ones outside of JVM and .NET and their performance was definitely not as good as it is now (I wish I could source this claim but I speak from personal experience). Then all of a sudden, in the late 2000s something changed and a lot of VMs started to pop up even for established languages, and with very good performance. Was something discovered about the JIT implementation that allowed pretty much every modern VM to skyrocket in performance? A paper or a book maybe?

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  • Should mock objects for tests be created at a high or low level

    - by Danack
    When creating unit tests for those other objects, what is the best way to create mock objects that provide data to other objects. Should they be created at a 'high level' and intercept the calls as soon as possible, or should they be done at a 'low level' and so make as much as the real code still be called? e.g. I'm writing a test for some code that requires a NoteMapper object that allows Notes to be loaded from the DB. class NoteMapper { function getNote($sqlQueryFactory, $noteID) { // Create an SQL query from $sqlQueryFactory // Run that SQL // if null // return null // else // return new Note($dataFromSQLQuery) } } I could either mock this object at a high level by creating a mock NoteMapper object, so that there are no calls to the SQL at all e.g. class MockNoteMapper { function getNote($sqlQueryFactory, $noteID) { //$mockData = {'Test Note title', "Test note text" } // return new Note($mockData); } } Or I could do it at a very low level, by creating a MockSQLQueryFactory that instead of actually querying the database just provides mock data back, and passing that to the current NoteMapper object. It seems that creating mocks at a high level would be easier in the short term, but that in the long term doing it at a low level would be more powerful and possibly allow more automation of tests e.g. by recording data in an out of a DB and then replaying that data for tests. Is there a recommended way of creating mocks? Are there any hard and fast rules about which are better, or should they both be used where appropriate?

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  • android third party libraries

    - by Terrance
    Its hard to believe that there aren't a ton of awesome third party (possibly open source) libraries out on the web for android using java but, I cant say I have found a great many so far but, droid seems like the only notable one I've come across. Any other majorly useful android libraries out there? Sorry in advanced if there is a dupe out there somewhere (seems like there should be) but if there is by all means post it and let me know.

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  • svn usage advice

    - by AngeloBad
    I need an advice about SVN usage. I use Tortoise SVN on my client to deal with a project I am working on. The probjem is that I have two set of bugs top fix on the project. One to deploy till 5 days, and one to deploy till 10 days. I am going to solve all the bugs before the 5fth days but I do not want to deploy the last 5 before the release date (till 10 days). How can I work on two separate codes and the merge all the modification? Is it possible? I have to create a branch?

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  • What do you call "X <= $foo <= Y" comparison?

    - by Jakob
    While writing a Perl statement like if ( $foo >= X && $foo <= Y ) yet again, I wondered why many programming languages do not support the more comfortable form if ( X <= $foo <= Y ) and what this is called. I came up with "3-legged comparison" but no results when searching for it. By the way there is also the "element-of-set" form if ( $foo in X..Y ) which I only consider more readable when provided via a short keyword. Is there a term for X <= $foo <= Y comparison? Which languages support it?

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  • Simple method for reliably detecting code in text?

    - by Jeff Atwood
    GMail has this feature where it will warn you if you try to send an email that it thinks might have an attachment. Because GMail detected the string see the attached in the email, but no actual attachment, it warns me with an OK / Cancel dialog when I click the Send button. We have a related problem on Stack Overflow. That is, when a user enters a post like this one: my problem is I need to change the database but I don't won't to create a new connection. example: DataSet dsMasterInfo = new DataSet(); Database db = DatabaseFactory.CreateDatabase("ConnectionString"); DbCommand dbCommand = db.GetStoredProcCommand("uspGetMasterName"); This user did not format their code as code! That is, they didn't indent by 4 spaces per Markdown, or use the code button (or the keyboard shortcut ctrl+k) which does that for them. Thus, our system is accreting a lot of edits where people have to go in and manually format code for people that are somehow unable to figure this out. This leads to a lot of bellyaching. We've improved the editor help several times, but short of driving over to the user's house and pressing the correct buttons on their keyboard for them, we're at a loss to see what to do next. That's why we are considering a Google GMail style warning: Did you mean to post code? You wrote stuff that we think looks like code, but you didn't format it as code by indenting 4 spaces, using the toolbar code button or the ctrl+k code formatting command. However, presenting this warning requires us to detect the presence of what we think is unformatted code in a question. What is a simple, semi-reliable way of doing this? Per Markdown, code is always indented by 4 spaces or within backticks, so anything correctly formatted can be discarded from the check immediately. This is only a warning and it will only apply to low-reputation users asking their first questions (or providing their first answers), so some false positives are OK, so long as they are about 5% or less. Questions on Stack Overflow can be in any language, though we can realistically limit our check to, say, the "big ten" languages. Per the tags page that would be C#, Java, PHP, JavaScript, Objective-C, C, C++, Python, Ruby. Use the Stack Overflow creative commons data dump to audit your potential solution (or just pick a few questions in the top 10 tags on Stack Overflow) and see how it does. Pseudocode is fine, but we use c# if you want to be extra friendly. The simpler the better (so long as it works). KISS! If your solution requires us to attempt to compile posts in 10 different compilers, or an army of people to manually train a bayesian inference engine, that's ... not exactly what we had in mind.

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  • time it takes to develop 4*N lines of code. Nonlinear, but how nonlinear ?

    - by Andrei
    It took me time T to develop program A, 1000 lines of code (SLOC), in certain language/area/complexity. Then how much time it will take to develop program B which is expected 4000 lines, in same area/complexity/language ? I expect it to be 4*N, right ? Any formula how T grows with SLOC ? For contractor, these estimates are important. Is there formula from software enginering books, or from people's experience ? Also, what methods exist to make the code bug-free before it hits QA ?

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  • Where and how to mention Stackoverflow participation in the résumé?

    - by Sandeepan Nath
    I think I have good enough reputation on SO now - here is my profile - http://stackoverflow.com/users/351903/sandeepan-nath. Well, this may not be that much as compared to so many other users out there but I am happy with mine. So, I was thinking of adding my profile link on my résumé. (Just the profile link and not that "I have this much reputation on SO"). Those who haven't seen, can see this question Would you put your stackoverflow profile link on your CV / Resume?. How would this look like? Forums/Blogs/Miscellaneous others No blogging as yet but active participant in Stackoverflow. My profile link - http://stackoverflow.com/users/351903/sandeepan-nath I think of putting this section after Project Details and Technical Expertise sections. Any tips/advice? Thanks Update MKO has made a very good point - "do you really want a potential employeer to be able to evaluate in detail everything you've ever written on SO". I thought of commenting but it would be too long - In my questions/answers I put a lot of statements like - "AFAIK ...", "following are my assumptions so far ...", "am I correct to conclude that... ?", "I doubt if it is possible to ..." etc. when I am not sure about something and I rarely involve in fights with other users. However I do argue on topics sometimes if I feel it is necessary and if I have a valid point. I do accept my mistakes and apologize for the same. As we all know nobody is perfect. I must have written many things which may be judged as wrong by a potential employer. But what if the same employer notices that I have improved in the quality of content by comparing old content with new one? Isn't that great? I also try to go back to older questions/answers and put corrective comments etc. when I feel I was wrong or if I can improve my post. Of course there are many employers who want you (potential employees) to be correct each and every time. They immediately remove you from consideration when you say a single incorrect thing. I have personally met such an interviewer few months back. He didn't even care to listen to any good thing I had done after he found a single wrong thing. Now the question is do you really care to work with such people? Or do you like those people who give value to the fact that you are striving to improve every day. I personally prefer the latter.

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  • How can I justify software testing to management?

    - by Nate
    I work for a small company (less than 200 employees) whose software group only makes up a small part of our staff (4 employees, occasionally with a few contractors). The four of us have been making strides in transitioning to better practices, and one of the next logical steps is to improve our testing. As anyone who has done any meaningful tests knows, testing takes a lot of time - and at my company, it takes too much time to justify to management, so we generally do what little we do on the sly. I don't think this is serving us well, as we keep coming up against otherwise avoidable problems when we ship under-tested software. I would like to be able to come to management with a justification for hiring a dedicated software test engineer (someone who can both write automated tests and perform manual ones). Are there any good published studies that show the benefits of adding such a position to a small company? Where can I find information about costs associated with the position? I plan on doing a little number crunching on our own history, but having some external sources to point to would help bolster my case.

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  • Opensource showcase for MVC in Java Swing

    - by Regular John
    I've allready created small desktop CRUD applications using Java/Swing. In hindsight I'm not quite sure if the overall design of these applications is good. I've also done some reading on MVC and looked at different Swing-tutorials. My problem is, that I've got a very theroatical knowledge of MVC and on the other hand, most Swing-resources don't implement the MVC-pattern. Now I would like to get my hands dirty and see how MVC is implemented in Swing in a real-world-application. Are there any opensource project you could recommend? It would be also interesting to have more than one project, to see different approaches. Best fit would be a software, that uses a relational database in the backend, to see an overall design, that I can compare to my former applications.

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  • save data in the database to xml in c [closed]

    - by Jayanth N
    I have some data in the database. I want those data in database to be stored as an xml file. I'm using postgresql 9.1 for database, for xml processing I'm using libxml (http://xmlsoft.org/). I'm writing the code in C language. Please help me. Detailed explanation: I have a client, which sends me a xml file. Server receives the xml file, parses the xml file and stores it in the db. From db i want to send the details in the form of an xml to the client. client: <employee> <name>glen</name> <telephone>123456789</telephone> </employee> <employee> <name>gwen</name> <telephone>123456789</telephone> </employee> server parses this xml file as displayed below: name : glen telephone:123456789 name : gwen telephone: 123456789 and saves it in a database(postgresql9.1) if the client requests for details of the employees, i've to send it in xml form from database.I don't know how to do it can u help me out.

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  • Best way to indicate more results available

    - by Alex Stangl
    We have a service to return messages. We want to limit the number returned, either allowing the caller to specify the max number to return, or else to use an internal hard limit. We also have thought it would be nice to include in the response whether more messages are available. The "best" way to go about this is not clear. Here are some ideas so far: Only set the "more messages" indicator if the user did not specify a max limit, and the internal max limit was hit. Same as #1 except that "more messages" indicator set regardless of whether the internal hard limit is hit, or the user-specified limit is hit. Same as #1 (or #2) except that we internally read limit + 1 records, but only return limit records, so we know "for sure" there is at least one additional message rather than "maybe" there are additional messages. Do away with the "more messages" flag, as it is confusing and unnecessary. Instead force the user to keep calling the API until it returns no messages. Change "more messages" indicator to something more akin to an EOF indicator, only set when the last message is known to have been retrieved and returned. What do you think is the best solution? (Doesn't have to be one of the above choices.) I searched and couldn't find a similar question already asked. Hopefully this is not "too subjective".

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