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  • how a pure functional programming language manage without assignment statements?

    - by Gnijuohz
    When reading the famous SICP,I found the authors seem rather reluctant to introduce the assignment statement to Scheme in Chapter 3.I read the text and kind of understand why they feel so. As Scheme is the first functional programming language I ever know something about,I am kind of surprised that there are some functional programming languages(not Scheme of course) can do without assignments. Let use the example the book offers,the bank account example.If there is no assignment statement,how can this be done?How to change the balance variable?I ask so because I know there are some so-called pure functional languages out there and according to the Turing complete theory,this must can be done too. I learned C,Java,Python and use assignments a lot in every program I wrote.So it's really an eye-opening experience.I really hope someone can briefly explain how assignments are avoided in those functional programming languages and what profound impact(if any) it has on these languages. The example mentioned above is here: (define (make-withdraw balance) (lambda (amount) (if (>= balance amount) (begin (set! balance (- balance amount)) balance) "Insufficient funds"))) This changed the balance by set!.To me it looks a lot like a class method to change the class member balance. As I said,I am not familiar with functional programming languages,so if I said something wrong about them,feel free to point out.

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  • Threads are facing deadlock in socket program [migrated]

    - by ankur.trapasiya
    I am developing one program in which a user can download a number of files. Now first I am sending the list of files to the user. So from the list user selects one file at a time and provides path where to store that file. In turn it also gives the server the path of file where does it exist. I am following this approach because I want to give stream like experience without file size limitation. Here is my code.. 1) This is server which gets started each time I start my application public class FileServer extends Thread { private ServerSocket socket = null; public FileServer() { try { socket = new ServerSocket(Utils.tcp_port); } catch (IOException e) { // TODO Auto-generated catch block e.printStackTrace(); } } @Override public void run() { try { System.out.println("request received"); new FileThread(socket.accept()).start(); } catch (IOException ex) { ex.printStackTrace(); } } } 2) This thread runs for each client separately and sends the requested file to the user 8kb data at a time. public class FileThread extends Thread { private Socket socket; private String filePath; public String getFilePath() { return filePath; } public void setFilePath(String filePath) { this.filePath = filePath; } public FileThread(Socket socket) { this.socket = socket; System.out.println("server thread" + this.socket.isConnected()); //this.filePath = filePath; } @Override public void run() { // TODO Auto-generated method stub try { ObjectInputStream ois=new ObjectInputStream(socket.getInputStream()); try { //************NOTE filePath=(String) ois.readObject(); } catch (ClassNotFoundException e) { // TODO Auto-generated catch block e.printStackTrace(); } File f = new File(this.filePath); byte[] buf = new byte[8192]; InputStream is = new FileInputStream(f); BufferedInputStream bis = new BufferedInputStream(is); ObjectOutputStream oos = new ObjectOutputStream( socket.getOutputStream()); int c = 0; while ((c = bis.read(buf, 0, buf.length)) > 0) { oos.write(buf, 0, c); oos.flush(); // buf=new byte[8192]; } oos.close(); //socket.shutdownOutput(); // client.shutdownOutput(); System.out.println("stop"); // client.shutdownOutput(); ois.close(); // Thread.sleep(500); is.close(); bis.close(); socket.close(); } catch (IOException ex) { ex.printStackTrace(); } } } NOTE: here filePath represents the path of the file where it exists on the server. The client who is connecting to the server provides this path. I am managing this through sockets and I am successfully receiving this path. 3) FileReceiverThread is responsible for receiving the data from the server and constructing file from this buffer data. public class FileReceiveThread extends Thread { private String fileStorePath; private String sourceFile; private Socket socket = null; public FileReceiveThread(String ip, int port, String fileStorePath, String sourceFile) { this.fileStorePath = fileStorePath; this.sourceFile = sourceFile; try { socket = new Socket(ip, port); System.out.println("receive file thread " + socket.isConnected()); } catch (IOException ex) { ex.printStackTrace(); } } @Override public void run() { try { ObjectOutputStream oos = new ObjectOutputStream( socket.getOutputStream()); oos.writeObject(sourceFile); oos.flush(); // oos.close(); File f = new File(fileStorePath); OutputStream os = new FileOutputStream(f); BufferedOutputStream bos = new BufferedOutputStream(os); byte[] buf = new byte[8192]; int c = 0; //************ NOTE ObjectInputStream ois = new ObjectInputStream( socket.getInputStream()); while ((c = ois.read(buf, 0, buf.length)) > 0) { // ois.read(buf); bos.write(buf, 0, c); bos.flush(); // buf = new byte[8192]; } ois.close(); oos.close(); // os.close(); bos.close(); socket.close(); //Thread.sleep(500); } catch (IOException ex) { ex.printStackTrace(); } } } NOTE : Now the problem that I am facing is at the first time when the file is requested the outcome of the program is same as my expectation. I am able to transmit any size of file at first time. Now when the second file is requested (e.g. I have sent file a,b,c,d to the user and user has received file a successfully and now he is requesting file b) the program faces deadlock at this situation. It is waiting for socket's input stream. I put breakpoint and tried to debug it but it is not going in FileThread's run method second time. I could not find out the mistake here. Basically I am making a LAN Messenger which works on LAN. I am using SWT as UI framework.

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  • Which is more maintainable -- boolean assignment via if/else or boolean expression?

    - by Bret Walker
    Which would be considered more maintainable? if (a == b) c = true; else c = false; or c = (a == b); I've tried looking in Code Complete, but can't find an answer. I think the first is more readable (you can literally read it out loud), which I also think makes it more maintainable. The second one certainly makes more sense and reduces code, but I'm not sure it's as maintainable for C# developers (I'd expect to see this idiom more in, for example, Python).

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  • Use-cases for node.js and c#

    - by Chase Florell
    I do quite a bit of ASP.NET work (C#, MVC), but most of it is typical web development. I do Restful architecture using CRUD repositories. Most of my clients don't have a lot of advanced requirements within their applications. I'm now looking at node.js and it's performance implications (I'm addicted to speed), but I haven't delved into it all that much. I'm wondering if node.js can realistically replace my typical web development in C# and ASP.NET MVC (not rewriting existing apps, but when working on new ones) node.js can complement an ASP.NET MVC app by adding some async goodness to the existing architecture. Are there use-cases for/against C# and node.js? Edit I love ASP.NET MVC and am super excited with where it's going. Just trying to see if there are special use cases that would favor node.js

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  • Secure Store Service Application not available in SharePoint 2010 Standard

    - by Haseeb Akhtar
    We have migrated from SharePoint 2010 foundation to SharePoint 2010 standard. Now, the problem is we are looking for Secure Store Service on 'Services on Server' page in Central Administration, but we didn't see it. We have another server where SharePoint 2010 standard is installed and there we can see Secure Store Service available. Please let me know what needs to be done for the same. Thanks in Advance

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  • What to do when projects are slow and you are being held up by others?

    - by antonpug
    Where I work, projects take a significant amount of time because the teams are large, there is a lot of "design and analysis", a lot of documentation, and work always gets pushed off. I work in the middle tier and I always have to wait for the services and client folks to get their work done. Oftentimes there are weeks at a time when I can't get any work done. I feel bored and weird just sitting here scrambling to at least appear like I am busy. Management seems to do little when asked for more work. What do you do in such cases?

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  • Ruby on Rails background API polling

    - by Matthew Turney
    I need to integrate a free/busy calendar integration with Zimbra. Unlike outlook, it seems, Zimbra requires polling their API. I need to be able to grab the free/busy data in background tasks for 10's of thousands of users on a regular time interval, preferably every few minutes. What would be the best way to implement this in a Rails application without bogging down our current resque tasks? I have considered moving this process to something like node.js or something similar in Ruby. The biggest problem is that we have no control over the IO, as each clients Zimbra instances could be slow and we don't want to create a huge backup in tasks. Thoughts and ideas?

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  • Reasons NOT to open source not-for-profit code?

    - by naught101
    I am a big fan of open source code. I think I understand most of the advantages of going open source. I'm a science student researcher, and I have to work with quite a surprising amount of software and code that is not open source (either it's proprietary, or it's not public). I can't really see a good reason for this, and I can see that the code, and people using it, would definitely benefit from being more public (if nothing else, in science it's vital that your results can be replicated if necessary, and that's much harder if others don't have access to your code). Before I go out and start proselytising, I want to know: are there any good arguments for not releasing not-for-profit code publicly, and with an OSI-compliant license? (I realise there are a few similar questions on SE, but most focus on situations where the code is primarily used for making money, and I couldn't much relevant in the answers.) Clarification: By "not-for-profit", I am including downstream profit motives, such as parent-company brand-recognition and investor profit expectations. In other words, the question relates only to software for which there is NO profit motive tied to the software what so ever.

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  • IDE for visually impaired

    - by Eli Rosencruft
    A visually impaired colleague has asked me to recommend an IDE with easy-to-find and easy-to-use controls for: font size background and foreground colors changing syntax color scheme support for at least C/C++ and Java He would prefer an IDE that is either portable or that has similar versions for Linux, Windows and Mac. He prefers a dark background and light colored fonts and needs to sit very close to the display.

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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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  • What quality standards to consider for software development process?

    - by Ron-Damon
    Hi, i'm looking for metrics/standards/normatives to evaluate a given "Software Development Process". I'm NOT looking to evaluate the SOFTWARE itself (trough SQUARE and such), i'm trying to evaluate software development PROCESS. So, my question is if you could give me some pointers to find this standard, considering that "evaluation objetives" would be documentation quality, how good is the customer relation, how efective is the process, etc. Very much like a ISO 9000, and like CMMI on a sense, but much lightweight and concrete and process oriented, not company oriented. Please help, i'm trying to stablish the advantages of our development process as formal as i can.

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  • Question about SDLC. How to answer this?

    - by pirzada
    I have seen this asked many times in job interviews but I am still not sure how to answer this. I am a web developer for quite some time but I still have problem with explaining OOP and SDLC (Familiar with system development life cycle) . How to prepare for above 2 topics for an interview point of view. Still I use both all the time during development. I am not clear on OOP SDLC Is there any simplest answer to both of these? Thanks

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  • Who are the outspoken critics of Object-Oriented design?

    - by Xepoch
    Sure, object-oriented techniques are great and have stuck around for a while. I know only less than a handful of critics of the OO principles. It seems as though most non-OO designs and architectures are shunned, yet we continue to write a lot of good software in C and solve a lot of data changes via awk/sed and countless other examples. Correct tool for the correct job, yes? I'm having a hard time finding articles, presentations, or published criticisms of OO (even Fred Brooks has blessed information hiding). Are there any well-known, published and/or outspoken critics of OO?

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  • Good sites for sharing code snippets & pastes that you can share links to?

    - by acidzombie24
    I know there are site tools to check if your webpage is alive, has compression, etc but lets not get into that. What are useful sites to paste code in and to share links to it? The three i know are http://codepad.org/ shows source and runs code online http://www.pastie.org/ share source with syntax highlighting http://jsfiddle.net/ great for JS help or for the occasional test. What else do you know of? One answer per question. I'll let lints and validators slide since you do paste code into them. Mention a weakness if you do know one so others wont be surprised or disappointed.

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  • Noob-Friendly Guides to WSGI?

    - by Johnny McKenzie
    world! I have recently been delving into server-side code web development with python, and I have hit a brick wall; you see, I know little about server side code and HTTP (other than the v. basics with php shudder), and all of the docs for wsgi that I have found seem to be for people already well established in the field. Are there any n00b happy guides for server-side scripting (the theory of), or on wsgi out there. Http would be helpful, video tuts are also greatly appreciated. Thanks in advance.

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  • What stands out on a Juniors CV

    - by DeanMc
    Hi all, I am looking for advice, hopefully from people more experienced that me. I am going to start applying for junior positions for .net development in the summer. At the moment the only thing on my CV is a project I have done for Windows Phone 7 called sprout sms. It allows the user to send webtext as provided by Irish Operators. The app is doing well and is top ten in my local marketplace (Ireland). By trade I am a salesman and that is the extent of most of my employment. I haven't been to college and due to financial commitments I would not be able to go down the road of full time education. I have kept up to date with various .net related tech in a junior capacity and am looking to now change careers. What I am look to see is what stands out on a juniors CV. My lack of education stands against me so I am looking to offset this with practical experience. I am open to all suggestions and from the end of this month I am free to pursue "notches" which will make my CV stand out. So in short if you where hiring a Junior, what would you like to see that would make you take a second look or request an interview? NOTE: I do fear this is a subjective subject, rather than debate what is the best items to have on a Juniors CV I would like to concentrate on what info you would give to a junior who is looking to apply for a job this year. Thanks to all that respond.

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  • With a small development team, how do you organize second-level support?

    - by Lenny222
    Say, you have a team of 5 developers and your inhouse customers demand a reasonable support availability of say 5 days a week, 9am-6pm. I can imagine the following scenarios: the customers approach the same guy, every time. Downside: single point of failure, if the guy is unavailable. each developer is assigned one week of support duty. Downside: how to you distribute the work evenly in times of planned (vacation) and unplanned (sickness) unavailability? each developer is assigned one day of support duty. Downside: similar to above, but not as bad. a randomly picked developer handles the support request. Downside: maybe not fair, see above. What is your experience?

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  • In which cases build artifacts will be different in different environments

    - by Sundeep
    We are working on automation of deployment using Jenkins. We have different environments - DEV, UAT, PROD. In SVN, we are tagging each release and placing same binaries in DEV, UAT, PROD. The artifacts already contains config files w.r.t each environment but I am not understanding why we are storing binaries in environment folder again. Are there any scenarios where deployment might be different for different environments.

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  • Is Intellisense faster in Visual Studio 2012 compared to Visual Studio 2010 for C++ projects?

    - by syplex
    We switched to VS2010 from VS2003 a few months ago, and there are many many improvements. But the speed of Intellisense is not one of them (although it does generate higher quality results, which is great). I read that Intellisense and the MSDN help system were being improved in VS2012, so I'm curious if its actually faster? The only data I could find were graphs of an early release (VS2011). For the record, I am using a vanilla install of VS2010 with SP1 on Windows 7 SP1 (x64). No plugins or add-ins running. What I'm looking for specifically: Has the speed of intellisense autocomplete improved? Has the speed of F12 (goto definition) improved? The answers to these questions will help in determining if VS2012 is worth the money to upgrade at this time as the intellisense slowness would be the only major reason for upgrading. I'd also be interested in knowing if the help system has improved. I'm currently using MSDN help from VS2008SP1 because it has filtering and is faster.

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  • Segmentation fault 11 in MacOS X- C++ [migrated]

    - by Marcos Cesar Vargas Magana
    all. I have a "segmentation fault 11" error when I run the following code. The code actually compiles but I get the error at run time. //** Terror.h ** #include <iostream> #include <string> #include <map> using std::map; using std::pair; using std::string; template<typename Tsize> class Terror { public: //Inserts a message in the map. static Tsize insertMessage(const string& message) { mErrorMessages.insert( pair<Tsize, string>(mErrorMessages.size()+1, message) ); return mErrorMessages.size(); } private: static map<Tsize, string> mErrorMessages; } template<typename Tsize> map<Tsize,string> Terror<Tsize>::mErrorMessages; //** error.h ** #include <iostream> #include "Terror.h" typedef unsigned short errorType; typedef Terror<errorType> error; errorType memoryAllocationError=error::insertMessage("ERROR: out of memory."); //** main.cpp ** #include <iostream> #include "error.h" using namespace std; int main() { try { throw error(memoryAllocationError); } catch(error& err) { } } I have kind of debugging the code and the error happens when the message is being inserted in the static map member. An observation is that if I put the line: errorType memoryAllocationError=error::insertMessage("ERROR: out of memory."); inside the "main()" function instead of at global scope, then everything works fine. But I would like to extend the error messages at global scope, not at local scope. The map is defined static so that all instances of "error" share the same error codes and messages. Do you know how can I get this or something similar. Thank you very much.

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  • Will they release a Wrox Box 4?

    - by Winston Muller
    Hi, does anyone know if there will be a Wrox Box 4? I would love to get something like that, but the latest collection of Wrox books seems to be the release for 3.5. I really need to get up to date with the latest version of .NET. I'm not sure if there will be a Wrox Box 4 though, because it looks like Wiley is now publishing Wrox books under Wiley, and not Wrox anymore. So it looks like I'm going to have to go with Professional ASP.NET 4 in C# Instead of the Wrox Box 3.5

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  • Hard-copy approaches to time tracking

    - by STW
    I have a problem: I suck at tracking time-on-task for specific feature/defects/etc while coding them. I tend to jump between tasks a fair bit (partly due to the inherit juggling required by professional software development, partly due to my personal tendancy to focus on the code itself and not the business process around code). My personal preference is for a hard-copy system. Even with gabillions of pixels of real-estate on-screen I find it terribly distracting to keep a tracking window convienient; either I forget about it or it gets in my ways. So, looking for suggestions on time-tracking. My only requirement is a simple system to track start/stop times per task. I've considered going as far as buying a time-clock and giving each ticket a dedicated time-card. When I start working on it, punch-in; when done working, punch-out.

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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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  • Using <= for every dependency in case of following semantic versioning idea

    - by zerkms
    As Semantic Versioning (and common sense) declares - the major version is incremented in case if non backward compatible change is introduced. Now let's assume we have a project called Project that has a current version 1.0.42 and a library Lib it depends on that is of a 2.1.3 version at the moment. Does that mean that following semver ideology we should constraint the dependency of the Project to be Depends: Lib (< 3)? From my experience - no one does that, but I find it semantically correct and very self-descriptive. What do you think of this?

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