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• How does one handle an incorrect resource file?

  - by AedonEtLIRA

  I'm starting the parser that will handle one of the key features of my app and realizing exactly who easy it would be for me to screw up a resource file that is provided to the application. For example, a simple resource that I provide to my app is a JSON file that contains an entity layout (name, fascia, location etc...). It would be easy for me to leave out the name of the entity or misspell the JSON key. Obviously catastrophic failures during parsing are to be handled in a try/catch, but how would subtle failures (such as a dyslexic spelling of name) be handled?

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• Which approach would lead to an API that is easier to use?

  - by Clem

  I'm writing a JavaScript API and for a particular case, I'm wondering which approach is the sexiest. Let's take an example: writing a VideoPlayer, I add a getCurrentTime method which gives the elapsed time since the start. The first approach simply declares getCurrentTime as follows: getCurrentTime():number where number is the native number type. This approach includes a CURRENT_TIME_CHANGED event so that API users can add callbacks to be aware of time changes. Listening to this event would look like the following: myVideoPlayer.addEventListener(CURRENT_TIME_CHANGED, function(evt){ console.log ("current time = "+evt.getDispatcher().getCurrentTime()); }); The second approach declares getCurrentTime differently: getCurrentTime():CustomNumber where CustomNumber is a custom number object, not the native one. This custom object dispatches a VALUE_CHANGED event when its value changes, so there is no need for the CURRENT_TIME_CHANGED event! Just listen to the returned object for value changes! Listening to this event would look like the following: myVideoPlayer.getCurrentTime().addEventListener(VALUE_CHANGED, function(evt){ console.log ("current time = "+evt.getDispatcher().valueOf()); }); Note that CustomNumber has a valueOf method which returns a native number that lets the returned CustomNumber object being used as a number, so: var result = myVideoPlayer.getCurrentTime()+5; will work! So in the first approach, we listen to an object for a change in its property's value. In the second one we directly listen to the property for a change on its value. There are multiple pros and cons for each approach, I just want to know which one the developers would prefer to use!

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• Architectural Composition Languages

  - by C. Lawrence Wenham

  Recently stumbled upon this paper (PDF) talking about ACLs, or Architectural Composition Languages. They're a fusion of two earlier lines of research: Architectural Definition Languages (such as UML) and Object Composition Languages (such as XAML, WWF, or scripting languages). The goal of an ACL is to have a high-level description of a program's architecture which can also be compiled into a runnable program. The high-level description assists automated analysis, while the 'executability' means changes can be tested immediately. You would still author the components of the program in a conventional programming language (C, Java, Python, etc), but they would be composed into a complete program by the ACL. One of the expected benefits is that a program can be ported to a different platform by swapping in "similar but different" components. I've been hankering for something like this for a long time (see this answer I gave on a StackOverflow question a few years ago). The paper mentions that the researchers were working on a language called ACL/1 that initially targeted Java, but would be ported to support .Net as well. However, I can't find any more mention of ACL/1 anywhere. Has there been any more work done on this? Are there any other implementations of the ACL concept that are available for use or experimentation?

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• Are There Realistic/Useful Solutions for Source Control for Ladder Logic Programs

  - by Steven A. Lowe

  Version control for ladder logic (LL) programs for programmable logic controllers (PLCs) seems to be virtually non-existent. It may be because LL is a visual language and tends to be stored in binary files, or it may be because source code control hasn't "caught on" in process control engineering circles - or perhaps my Google-Fu is weak tonight. Do you know of any realistic and useful solutions for version control for such systems? Definitions: realistic = changes to the programs are tracked by user and subject to reversion and merges useful = the system integrates with visual LL designers, is not limited to LL from a single PLC manufacturer, and does not cost a ridiculous amount of money? Note: I have heard of people using SVN or Mercurial et al to track the binary files, but I don't think the diff/merge capabilities would display readable differences.

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• Splitting big request in multiple small ajax requests

  - by Ionut

  I am unsure regarding the scalability of the following model. I have no experience at all with large systems, big number of requests and so on but I'm trying to build some features considering scalability first. In my scenario there is a user page which contains data for: User's details (name, location, workplace ...) User's activity (blog posts, comments...) User statistics (rating, number of friends...) In order to show all this on the same page, for a request there will be at least 3 different database queries on the back-end. In some cases, I imagine that those queries will be running quite a wile, therefore the user experience may suffer while waiting between requests. This is why I decided to run only step 1 (User's details) as a normal request. After the response is received, two ajax requests are sent for steps 2 and 3. When those responses are received, I only place the data in the destined wrappers. For me at least this makes more sense. However there are 3 requests instead of one for every user page view. Will this affect the system on the long term? I'm assuming that this kind of approach requires more resources but is this trade of UX for resources a good dial or should I stick to one plain big request?

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• Using table-styled divs instead of tables

  - by mister martin

  I was referred here from stackoverflow as my question was apparently too broad. I'm working on a template, and I know using CSS is preferred over HTML tables for positioning... But, is it acceptable to get the best of both worlds and use table-like styles on my divs? For example: display: table; This not only helps solve the sticky footer problem, but it also avoids the pains associated with using floats. Somehow it feels dirty, but I can't logically explain why because it works without any "tricks" or ugly hacks, which is how it should be, right? Is this technically incorrect, or does it ultimately boil down to just a matter of opinion? ...Thoughts?

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• Parsing stdout with custom format or standard format?

  - by linquize

  To integrate with other executables, a executable may launch another executable and capture its output from stdout. But most programs writes the output message to stdout in custom format and usually in human readable format. So it requires the system integrator to write a function to parse the output, which is considered trouble and the parser code may be buggy. Do you think this is old fashioned? Most Unix-style programs do that. Very few programs write to stdout in standard format such as XML or JSON, which is more modern. Example: Veracity (DVCS) writes JSON to stdout. Should we switch to use modern formats? For a console program, human readable or easy parsable: which is more important ?

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• How often do CPUs make calculation errors?

  - by veryfoolish

  In Dijkstra's Notes on Structured Programming he talks a lot about the provability of computer programs as abstract entities. As a corollary, he remarks how testing isn't enough. E.g., he points out the fact that it would be impossible to test a multiplication function f(x,y) = x*y for any large values of x and y across the entire ranges of x and y. My question concerns his misc. remarks on "lousy hardware". I know the essay was written in the 1970s when computer hardware was less reliable, but computers still aren't perfect, so they must make calculation mistakes sometimes. Does anybody know how often this happens or if there are any statistics on this?

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• Is there a good book to grok C++?

  - by Paperflyer

  This question got me thinking. I would say I am a pretty experienced C++ programmer. I use it a lot at work, I had some courses on it at the university, I can understand most C++ code I find out there without problems. Other languages you can pretty much learn by using them. But every time I use a new C++ library or check out some new C++ code by someone I did not know before, I discover a new set of idioms C++ has to offer. Basically, this has lead me to believe that there is a lot of stuff in C++ that might be worth knowing but that is not easily discoverable. So, is there a good book for a somewhat experienced C++ programmer to step up the game? You know, to kind of 'get' that language the way you can 'get' Ruby or Objective-C, where everything just suddenly makes sense and you start instinctively knowing 'that C++ way of thing'?

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• Why are people using C instead of C++? [closed]

  - by Darth

  Possible Duplicate: When to use C over C++, and C++ over C? Many times I've stumbled upon people saying that C++ is not always better than C. Great example here would be the Linux kernel, where they simply decided to use C instead of C++ because it had better compilers at the time. But that's many years ago and a lot has changed. So the question is, why are people still using C over C++? I gues there are probably some cases (like embedded devices), where there simply isn't a good C++ compiler, or am I wrong here? What are the other cases when it is better to go with C instead of C++?

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• MCSD Certification, any recommended study material?

  - by Dayan

  I wish to study for the new MCSD Certification For web applications: I headed over to Amazon in search of some books and had no luck with finding anything up to date, most books are outdated, such as the list provided by Amazon MCSD Books. Is this because the test is more based on experience rather than just an understanding of the subject? Any tips and/or recommended materials will be appreciated, thank you!

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• Algorithm for tracking progress of controller method running in background

  - by SilentAssassin

  I am using Codeigniter framework for PHP on Windows platform. My problem is I am trying to track progress of a controller method running in background. The controller extracts data from the database(MySQL) then does some processing and then stores the results again in the database. The complete aforesaid process can be considered as a single task. A new task can be assigned while another task is running. The newly assigned task will be added in a queue. So if I can track progress of the controller, I can show status for each of these tasks. Like I can show "Pending" status for tasks in the queue, "In Progress" for tasks running and "Done" for tasks that are completed. Main Issue: Now first thing I need to find is an algorithm to track the progress of how much amount of execution the controller method has completed and that means tracking how much amount of method has completed execution. For instance, this PHP script tracks progress of array being counted. Here the current state and state after total execution are known so it is possible to track its progress. But I am not able to devise anything analogous to it in my case. Maybe what I am trying to achieve is programmtically not possible. If its not possible then suggest me a workaround or a completely new approach. If some details are pending you can mention them. Sorry for my ignorance this is my first post here. I welcome you to point out my mistakes. EDIT: Database outline: The URL(s) and keyword(s) are first entered by user which are stored in a database table called link_master and keyword_master respectively. Then keywords are extracted from all the links present in this table and compared with keywords entered by user and their frequency is calculated which is the final result. And the results are stored in another table called link_result. Now sub-links are extracted from the domain links and stored in a table called sub_link_master. Now again the keywords are extracted from these sub-links and the corresponding results are stored in a table called sub_link_result. The number of records cannot be defined beforehand as the number of links on any web page can be different. Only the cardinality of *link_result* table can be known which will be equal to multiplication of number of keyword(s) and URL(s) . I insert multiple records at a time using this resource. Controller outline: The controller extracts keywords from a web page and also extracts keywords from all the links present on that page. There is a method called crawlLink. I used Rolling Curl to extract keywords and web page content. It has callback function which I used for extracting keywords alongwith generating results and extracting valid sub-links. There is a insertResult method which stores results for links and sub-links in the respective tables. Yes, the processing depends on the number of records. The more the number of records, the more time it takes to execute: Consider this scenario: Number of Domain Links = 1 Number of Keywords = 3 Number of Domain Links Result generated = 3 (3 x 1 as described in the question) Number of Sub Links generated = 41 Number of Sub Links Result = 117 (41 x 3 = 123 but some links are not valid or searchable) Approximate time taken for above process to complete = 55 seconds. The above result is for a single link. I want to track the progress of the above results getting stored in database. When all results are stored, the task is complete. If results are getting stored, the task is In Progress. I am not clear how can I track this progress.

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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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• How to achieve a loosely coupled REST API but with a defined and well understood contract?

  - by BestPractices

  I am new to REST and am struggling to understand how one would properly design a REST system to both allow for loose coupling but at the same time allow a consumer of a REST API to understand the API. If, in my client code, I issue a GET request for a resource and get back XML, how do I know what to do with that xml? e.g. if it contains <fname>John</fname><lname>Smith</lname> how do I know that these refer to the concept of "first name", "last name"? Is it up to the person writing the REST API to define in documentation some place what each of the XML fields mean? What if producer of the API wants to change the implementation to be <firstname> instead of <fname>? How do they do this and notify their consumers that this change occurred? Or do the consumers just encounter the error and then look at the payload and figure out on their own that it changed? I've read in REST in Practice that using a WADL tool to create a client implementation based on the WADL (and hide the fact that you're doing a distributed call) is an "anti-pattern". But I was planning to do this-- at least then I would have a statically typed API call that, if it changed, I would know at compile time and not at run time. Why is this a bad thing to generate client code based on a WADL? And how do I know what to do with the links that returned in the response of a POST to a REST API? What defines this contract and gives true meaning to what each link will do? Please help! I dont understand how to go from statically-typed or even SOAP/RPC to REST!

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• Which simple Java JPA ORM tool to use ?

  - by Guillaume

  What Java ORM library implementing JPA that match following criteria would you recommend and why ? free & open source alive (at least bug fixes and a mailing list) with good documentation simple (simpler than hibernate) I need to select a simple ORM tool that can be set up in minutes, without too much configuration and easy to understand, for setting simple CRUD DAOs. A query builder will be an interesting plus. Later I can have to move to Hibernate, that's why being JPA compliant is a must. I have found some candidates on the web, but not so much feedback, so I will gladly take your advices on the topic. ----- EDIT --------- I have been successfully testing ebean/avaje with a small test cases. Any one has a feedback on using these tools in production ?

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• Best design for a memory resident tool

  - by Andrew S.

  I apologize if this tends more toward design that programming, but here goes. What design would you recommend for a database that is Memory resident Must run on windows, linux and (at a stretch) the mac Accept multiple queries simultaneously Have minimum overhead, since a search is expected to take <0.25s This program implements a domain-specific search. Think of it as a database, but one that takes advantage of domain specific information to outperform a convential database search (for example, with custom oracle indexing). We have a custom data structure for our data. Our protoype is a simple exe that constructs the database in memory each time it is run. We were thinking that perhaps this program would suffice, but augmented with sockets so it can listen for queries. This database will be static. Its contents will change infrequently. We expect queries, and the solution, to be delivered via a web service.

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• How to understand Linux kernel source code for a beginner?

  - by Amit Chavan

  Hi, I am a student interested in working on Memory Management, particularly the page replacement component of the linux kernel. What are the different guides that can help me to begin understanding the kernel source? I have tried to read the book Understanding the Linux Virutal Memory Manager by Mel Gorman and Understanding the Linux Kernel by Cesati and Bovet, but they do not explain the flow of control through the code. They only end up explaining various data structures used and the work various functions perform. This makes the code more confusing. My project deals with tweaking the page replacement algorithm in a mainstream kernel and analyse its performance for a set of workloads. Is there a flavor of the linux kernel that would be easier to understand(if not the linux-2.6.xx kernel)?

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• How can I create a facebook style message system in Rails 3?

  - by Angela

  I am trying to create a basic message system that allows users to send messages to each other and display it in a simple "Inbox" that shows both messages received and sent, as well as the status of read or unread. Ideally I could reuse existing code. But if not, can someone provide a framework to help me do it? I started to use a single Message record that has UserMessage - one for the sender, one for the receiver. That way I could have separate status. But I'm not sure I'm quite doing it right and would like some guidance. Thanks.

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• Is porting a Windows application to Mac worth it ?

  - by mikel

  I have a C# Windows application that sells for $35, and fairly regularly receive requests for a version for OS X too. I don't have any experience with Mac so far though, and so am not sure exactly how much work that would involve and if it would be worth it. If anyone's been in a similar position, it'd be very helpful to know: Roughly how many more (%) sales can you expect by porting to Mac ? Would you say it's worth the investment of a new Macbook Pro and the time of learning and porting to Objective-C ? Thanks in advance.

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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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• 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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• Easy to understand and interesting book on algorithms

  - by gasan

  Please advise me a book on algorithms, that would be easier to read and understand than Cormen's book1. It may be not so big and deep in explanation. I even want it to not be that big, however it shouldn't contain misconceptions or errors or inaccuracies. It should be a some kind of pre-Cormen's book, that will help later to understand more sophisticated conceptions. A beginner book (but still worth to read). 1 Introduction to Algorithms by Thomas H. Cormen, Charles E. Leiserson, Ronald L. Rivest, and Clifford Stein

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• How can I refactor client side functionality to create a product line-like generic design?

  - by Nupul

  Assume the following situation similar to that of Stack Overflow: I have a system with a front-end that can perform various manipulations on the data (by sending messages to REST back-end): Posting Editing and deleting Adding labels and tags Now in the first version we created it well modularized but the need as of now for 'evolving' the system similar to Stack Overflow. My question is how best to separate the commonality and how to incorporate the variability with respect to the following: Commonality: The above 'functionalities' and sending/receiving the data from the server Look and feel (also a variability as explained below) HTTP verbs associated with the above actions Variability: The RESTful URLs where the requests are sent The text/style of the UI (the commonality is analogous to Stack Overflow - the functionality of upvotes, posting a question remains the same, but the words, the icons, the look and feel is still different across sites) I think this is entirely a client-side code organization/refactoring issue. I'm heavily using jQuery, javascript and backbone for front-end development. My question is how best should I isolate the same to be able to create multiple such aspects to the tool we are currently working on?

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• How long can a user remember what they were working on? [migrated]

  - by GlenPeterson

  A web application lets the user browse its screens for future or past months. The time period the user is currently viewing follows the user through every screen of the system. But users can be logged in for a month or more. After a certain period of inactivity, we will prompt the user: You were viewing November 2008 when you last clicked. Want to view the current (default) time period instead? How long between user clicks should we wait to show this message? I'm guessing somewhere between 30 minutes and 3 hours most people will forget what they were doing, but I'd love to have some data, or someone's experience to base it on. Other suggestions related to this issue?

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• Suggestions for getting an open source electron beam tracking code going

  - by Boaz

  I work in the field of accelerator physics and synchrotron radiation. High energy electrons circulating in large rings of magnets produce x-rays that are used for a variety of different kinds of science. Running and improving these facilities requires controlling and modelling the electron beam as it circulates in the ring. A code to model this basically requires trackers to follow the electrons through the elements (something called a symplectic integrator), and then the computation of different parameters associated with this motion. The problem with these codes is that every facility has there own. In principle the code is not so complex. And as a modelling project, one might think it has some general interest. Who doesn't want to be able to create a track in space out of magnets and watch the electrons circulate? There is a Matlab based code to do this called Accelerator Toolbox, but the creator of the code is no longer in the field. I put the code in Sourceforge under the name atcollab. The basic resource is in C- it is the set of symplectic integrators. These are available in the atcollab code here. It has been useful to put the code on Sourceforge in order to exchange code, but the community of users is quite small and most are too busy to put that much time into collaboration. So in terms of really improving the code, I don't think it has been so successful. Any piece of this picture could be recreated without that much difficulty, but overall it is a bit complex, and because each lab has their own installation with lots of add-on Matlab code, people find it hard to really work together and share code. Somehow I think we need to involve a wider community in our development, or just use some standard tools. But for that, I suppose it needs to be of some general interest. I think symplectic integrators may have some general interest. And the part about a plug-in architecture to build up the ring ought to fit other patterns. Or the other option is to just accept that this is not a problem of general interest, and work harder within our small community. Suggestions, or anecdotes of analogous experience would be appreciated.

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