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  • Object Oriented programming on 8-bit MCU Case Study

    - by Calvin Grier
    I see that there's a lot of questions related to OO Programming here. I'm actually trying to find a specific resource related to embedded OO approaches for an 8 bit MCU. Several years back (maybe 6) I was looking for material related to Object Oriented programming for resource constrained 8051 microprocessors. I found an article/website with a case history of a design group that used a very small RAM part, and implemented many Object based constructs during their C design and development. I believe it was an 8051. The project was a success, and managed to stay inside the very small ROM/RAM they had available. I'm attempting to find it again, but Google can't locate it. The article was well written, and recommended a "mixed" approach using C methods for inheritance and encapsulation - if I recall correctly. Can anyone help me locate this article?

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  • how to troubleshoot sql server issues

    - by joe
    i have an ASP .net application with sql server database, and i am wondering if you can give your ideas on how to troubleshoot the following issue: i can insert / update / delete from any table, but i have one page that uses transactions to insert into different tables. the c# code is correct and very simple, but it fails. i used the sql profiler to see how my app interacts with the DB, especially that the app is using stored procedures, i can catch the exec procedure statement and run it manually from SSMS and it works fine, but the same stored procedure fails from the application!!! which lead me to think that issue is coming from the user account and settings, i am no expert in sql server and wondering if anyone can explain how to verify the required settings for user account. thanks EDIT: in web.config here is how i reference my connection <connectionStrings> <add name="Conn" connectionString="Data Source=localhost;Initial Catalog=myDB;Persist Security Info=True;User ID=DbUser;Password=password1254_3" providerName="System.Data.SqlClient"> </connectionstring> EDIT: i will try to describe the process here: 1- i begin a transaction 2- i call a stored proc to insert (which succeeds) and return the scope identity ( that will be used in the next step) 3- i call another stored procedure to insert some more info + scope identity from step 2, which is a foreign key here 4- i get error, foreign key violation 5- transaction rolled back, now tables empty again... thanks

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  • Explanation on how "Tell, Don't Ask" is considered good OO

    - by Pubby
    This blogpost was posted on Hacker News with several upvotes. Coming from C++, most of these examples seem to go against what I've been taught. Such as example #2: Bad: def check_for_overheating(system_monitor) if system_monitor.temperature > 100 system_monitor.sound_alarms end end versus good: system_monitor.check_for_overheating class SystemMonitor def check_for_overheating if temperature > 100 sound_alarms end end end The advice in C++ is that you should prefer free functions instead of member functions as they increase encapsulation. Both of these are identical semantically, so why prefer the choice that has access to more state? Example 4: Bad: def street_name(user) if user.address user.address.street_name else 'No street name on file' end end versus good: def street_name(user) user.address.street_name end class User def address @address || NullAddress.new end end class NullAddress def street_name 'No street name on file' end end Why is it the responsibility of User to format an unrelated error string? What if I want to do something besides print 'No street name on file' if it has no street? What if the street is named the same thing? Could someone enlighten me on the "Tell, Don't Ask" advantages and rationale? I am not looking for which is better, but instead trying to understand the author's viewpoint.

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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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  • Class design, One class in two sources

    - by Pavla
    Is it possible define methods from the same class in different "CPP" files? I have header file "myClass.h" with: class myClass { public: // methods for counting ... // methods for other ... }; I would like to define "methods for counting" in one CPP and "methods for other" in other CPP. For clarity. Both groups of methods sometime use the same attributes. Is it possible? Thanks :).

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  • Can't understand example using continuations

    - by Matt Fenwick
    I'm reading the r6rs Scheme report and am confused by the explanation of continuations (I find it to be too dense and lacking of examples for a beginner). What is this code doing and how does it evaluate to 4? Why does call/cc want an argument that's a function of one argument? How is call/cc's argument used? (+ 1 (call-with-current-continuation (lambda (escape) (+ 2 (escape 3))))) =? 4 This example is from section 1.11 - Continuations.

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  • ASP.NET web-application example for newbies

    - by A-Cube
    I want to learn ASP.NET web-application development by example. I want to learn it from an already developed web-application that is good as a tutorial for newbies. A fully functional web application that is small but powerful enough to teach newbies the development effort required for web-application development. I am looking for some application that is made using software engineering principles and not just a code written haphazardly.

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  • Flash messages in ASP.NET MVC without sessions

    - by Fernando Correia
    I'm developing a web application for Windows Azure using ASP.NET MVC 4. I would like to enforce one restriction in the architecture: do not use Session. To achieve availability on Azure, and since there is no sticky sessions, I would need to store the session data in some central service, probably either SQL Azure or the Caching Service. I would rather avoid sessions on the SQL database to avoid the increased latency, and the caching service on Azure is very expensive for the ammount of memory offered. On the other hand, I would like to have the ability to easily pass Flash-style messages among redirects. TempData is the recommended way to do this, but by default it uses the session object. So I would like to know: Is there an alternative way to use TempData that doesn't require sessions or shared data between servers? Cookies perhaps? Is there a better alternative I'm overlooking?

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  • Is there an easy way to type in common math symbols?

    - by srcspider
    Disclaimer: I'm sure someone is going to moan about easy-of-use, for the purpose of this question consider readability to be the only factor that matters So I found this site that converts to easting northing, it's not really important what that even means but here's how the piece of javascript looks. /** * Convert Ordnance Survey grid reference easting/northing coordinate to (OSGB36) latitude/longitude * * @param {OsGridRef} gridref - easting/northing to be converted to latitude/longitude * @returns {LatLonE} latitude/longitude (in OSGB36) of supplied grid reference */ OsGridRef.osGridToLatLong = function(gridref) { var E = gridref.easting; var N = gridref.northing; var a = 6377563.396, b = 6356256.909; // Airy 1830 major & minor semi-axes var F0 = 0.9996012717; // NatGrid scale factor on central meridian var f0 = 49*Math.PI/180, ?0 = -2*Math.PI/180; // NatGrid true origin var N0 = -100000, E0 = 400000; // northing & easting of true origin, metres var e2 = 1 - (b*b)/(a*a); // eccentricity squared var n = (a-b)/(a+b), n2 = n*n, n3 = n*n*n; // n, n², n³ var f=f0, M=0; do { f = (N-N0-M)/(a*F0) + f; var Ma = (1 + n + (5/4)*n2 + (5/4)*n3) * (f-f0); var Mb = (3*n + 3*n*n + (21/8)*n3) * Math.sin(f-f0) * Math.cos(f+f0); var Mc = ((15/8)*n2 + (15/8)*n3) * Math.sin(2*(f-f0)) * Math.cos(2*(f+f0)); var Md = (35/24)*n3 * Math.sin(3*(f-f0)) * Math.cos(3*(f+f0)); M = b * F0 * (Ma - Mb + Mc - Md); // meridional arc } while (N-N0-M >= 0.00001); // ie until < 0.01mm var cosf = Math.cos(f), sinf = Math.sin(f); var ? = a*F0/Math.sqrt(1-e2*sinf*sinf); // nu = transverse radius of curvature var ? = a*F0*(1-e2)/Math.pow(1-e2*sinf*sinf, 1.5); // rho = meridional radius of curvature var ?2 = ?/?-1; // eta = ? var tanf = Math.tan(f); var tan2f = tanf*tanf, tan4f = tan2f*tan2f, tan6f = tan4f*tan2f; var secf = 1/cosf; var ?3 = ?*?*?, ?5 = ?3*?*?, ?7 = ?5*?*?; var VII = tanf/(2*?*?); var VIII = tanf/(24*?*?3)*(5+3*tan2f+?2-9*tan2f*?2); var IX = tanf/(720*?*?5)*(61+90*tan2f+45*tan4f); var X = secf/?; var XI = secf/(6*?3)*(?/?+2*tan2f); var XII = secf/(120*?5)*(5+28*tan2f+24*tan4f); var XIIA = secf/(5040*?7)*(61+662*tan2f+1320*tan4f+720*tan6f); var dE = (E-E0), dE2 = dE*dE, dE3 = dE2*dE, dE4 = dE2*dE2, dE5 = dE3*dE2, dE6 = dE4*dE2, dE7 = dE5*dE2; f = f - VII*dE2 + VIII*dE4 - IX*dE6; var ? = ?0 + X*dE - XI*dE3 + XII*dE5 - XIIA*dE7; return new LatLonE(f.toDegrees(), ?.toDegrees(), GeoParams.datum.OSGB36); } I found that to be a really nice way of writing an algorythm, at least as far as redability is concerned. Is there any way to easily write the special symbols. And by easily write I mean NOT copy/paste them.

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  • Requiring multithreading/concurrency for implementation of scripting language

    - by Ricky Stewart
    Here's the deal: I'm looking at designing my own scripting/interpreted language for fun. I'm only in the planning stages right now; I want to make sure I have a very strong hold on exactly how I will implement everything before I start coding. What I'm currently struggling with is concurrency. It seems to me like an easy way to avoid the unpredictable performance that comes with garbage collection would be to put the garbage collector in its own thread, and have it run concurrently with the interpreter itself. (To be clear, I don't plan to allow the scripts to be multithreaded themselves; I would simply put a garbage collector to work in a different thread than the interpreter.) This doesn't seem to be a common strategy for many popular scripting languages, probably for portability reasons; I would probably write the interpreter in the UNIX/POSIX threading framework initially and then port it to other platforms (Windows, etc.) if need be. Does anyone have any thoughts in this issue? Would whatever gains I receive by exploiting concurrency be nullified by the portability issues that will inevitably arise? (On that note, am I really correct in my assumption that I would experience great performance gains with a concurrent garbage collector?) Should I move forward with this strategy or step away from it?

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  • Hiring a swing developer - Need some tough assignments

    - by Jay
    I am trying to hire a java swing developer, who would most likely work on a java 1.4 based swing app. I have finalized 2-3 people and I would like to give them a one week assignment on Swing. It has to be a really tough one - something that they can't just copy from the internet and something that tests their in-depth knowledge on Swing. I can think of things like split screen windows, and custom UI controls that would involve custom paining. If you were to prepare such an assignment, what would you do? Please share your thoughts/experiences.

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  • Workflow versioning

    - by Nitra
    I believe I have a fundamental misunderstanding when it comes to workflow engines which I would appreciate if you could help me sort out. I'm not sure if my misunderstanding is specific to the workflow engine I'm using, or if it's a general misunderstanding. I happen to use Windows Workflow Foundation (WWF). TLDR-version WWF allows you to implement business processes in long-running workflows (think months or even years). When started, the workflows can't be changed. But what business process can't change at any time? And if a business process changes, wouldn't you want your software to reflect this change for already started 'instances' of the business process? What am I missing? Background In WWF you define a workflow by combining a set of activites. There are different types of activities - some of them are for flow control, such as the IfElseActivity and the WhileActivty while others allows you to perform actual tasks, such as the CodeActivity wich allows you to run .NET code and the InvokeWebServiceActivity which allows you to call web services. The activites are combined to a workflow using a visual designer. You pretty much drag-and-drop activities from a toolbox to a designer area and connect the activites to each other. The workflow and activities have input paramters, output parameters and variables. We have a single workflow which sometimes runs in a matter of a few days, but it may run for 5-6 months. WWF takes care of persisting the workflow state (what activity are we currently executing, what are the variable values and so on). So far I think WWF makes sense. Some people will prefer to implement a software representation of a business process using a visual designer over writing all of it in code. So what's the issue then? What I don't really get is the following: WWF is designed to take care of long-running workflows. But at the same time, WWF has no built-in functionality which allows you to modify the running workflows. So if you model a business process using a workflow and run that for 6 months, you better hope that the business process does not change. Because if it do, you'll have to have multiple versions of the workflow executing at the same time. This seems like a fundamental design mistake to me, but at the same time it seems more likely that I've misunderstood something. For us, this has had some real-world effects: We release new versions every month, but some workflows may run for a year. This means that we have several versions of the workflow running in parallell, in other words several versions of the business logics. This is the same as having many differnt versions of your code running in production in the same system at the same time, which becomes a bit hard to understand for users. (depending on on whether they clicked a 'Start' button 9 or 10 months ago, the software will behave differently) Our workflow refers to different types of entities and since WWF now has persisted and serialized these we can't really refactor the entities since then existing workflows can't be resumed (deserialization will fail We've received some suggestions on how to handle this When we create a new version of the workflow, cancel all running workflows and create new ones. But in our workflows there's a lot of manual work involved and if we start from scratch a lot of people has to re-do their work. Track what has been done in the workflow and when you create a new one skip activites which have already been executed. I feel that this alternative may work for simple workflows, but it becomes hairy to automatically figure out what activities to skip if there's major refactoring done to a workflow. When we create a new version of the workflow, upgrade old versions using the new WWF 4.5 functionality for upgrading workflows. But then we would have to skip using the visual designer and write code to inject activities in the right places in the workflow. According to MSDN, this upgrade functionality is only intended for minor bug fixes and not larger changes. What am I missing?

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  • Are there open source alternatives to Bitbucket, Github, Kiln, and similar DVCS browsing and management tools?

    - by Ryan Taylor
    I am aware of several tools/services that provide DVCS browsing and management such as Bitbucket, Github, Kiln, SCM-Manager and Rhodecode. However, the use case I am considering is one such that: Any source code must reside on an employers internal servers. The solution must be open source. It should provide a Bitbucket or Github like experience, including a project wiki, repository browsing and management, and social coding aspects such as code review. The solution should have mercurial support (if not support for other DVCSs). Of these, only SCM-Manager and RhodeCode come close as they can be installed on your own servers and are open source. However they do not have the Bitbucket or Github experience. There is no issue tracker or wiki and the UI, while functional, is not up to par with Github or Bitbucket. I can get close with Trac or Redmine with their repository browsers but unfortunately they do not have any repository management capabilities. Are there other open source tools out there that would provide a similar experience to Bitbucket, Github or Kiln?

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  • Adding complexity to remove duplicate code

    - by Phil
    I have several classes that all inherit from a generic base class. The base class contains a collection of several objects of type T. Each child class needs to be able to calculate interpolated values from the collection of objects, but since the child classes use different types, the calculation varies a tiny bit from class to class. So far I have copy/pasted my code from class to class and made minor modifications to each. But now I am trying to remove the duplicated code and replace it with one generic interpolation method in my base class. However that is proving to be very difficult, and all the solutions I have thought of seem way too complex. I am starting to think the DRY principle does not apply as much in this kind of situation, but that sounds like blasphemy. How much complexity is too much when trying to remove code duplication? EDIT: The best solution I can come up with goes something like this: Base Class: protected T GetInterpolated(int frame) { var index = SortedFrames.BinarySearch(frame); if (index >= 0) return Data[index]; index = ~index; if (index == 0) return Data[index]; if (index >= Data.Count) return Data[Data.Count - 1]; return GetInterpolatedItem(frame, Data[index - 1], Data[index]); } protected abstract T GetInterpolatedItem(int frame, T lower, T upper); Child class A: public IGpsCoordinate GetInterpolatedCoord(int frame) { ReadData(); return GetInterpolated(frame); } protected override IGpsCoordinate GetInterpolatedItem(int frame, IGpsCoordinate lower, IGpsCoordinate upper) { double ratio = GetInterpolationRatio(frame, lower.Frame, upper.Frame); var x = GetInterpolatedValue(lower.X, upper.X, ratio); var y = GetInterpolatedValue(lower.Y, upper.Y, ratio); var z = GetInterpolatedValue(lower.Z, upper.Z, ratio); return new GpsCoordinate(frame, x, y, z); } Child class B: public double GetMph(int frame) { ReadData(); return GetInterpolated(frame).MilesPerHour; } protected override ISpeed GetInterpolatedItem(int frame, ISpeed lower, ISpeed upper) { var ratio = GetInterpolationRatio(frame, lower.Frame, upper.Frame); var mph = GetInterpolatedValue(lower.MilesPerHour, upper.MilesPerHour, ratio); return new Speed(frame, mph); }

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  • How should I make searching a relational database more efficient?

    - by Travis J
    This is in the scope of a web application. I have a database which has a few nested relations. There is a feature which depicts the history of a large chain of relations. It is essentially a data analysis feature. The issue is that in order to search, a large object graph must be loaded - the loading time for this object graph is not quick enough to be viable. The problem is that without loading the whole graph it makes searching from a single string nearly impossible. In order to search, explicit fields must be specified and the search data supplied. Is there a design pattern for exposing the data in a way which facilitates a single string search instead of having to explicitly define parameters?

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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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  • test cases for common algorithms [on hold]

    - by Alexey
    I need samples of test inputs and correct outputs for common algorithms for sorting, searching, data structures, graphs, etc. to check for mistakes in my future implementations. Can you advice resources with test cases? Or a website with community that implements algorithms and shares with results? Thanks! Edit: to clarify: I am going to implement forementioned algorithms for studying purposes and need inputs including large ones and correct outputs to better find mistakes in my implementations, since test cases that I can come up with on my own with might not be enough to reveal mistakes.

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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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  • 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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  • Fundamental programming book [closed]

    - by Luke Annison
    I'm a fairly new programmer and currently learning ruby on rails with the intention of developing a web application. I am currently going reading Agile Web Development with Rails 4th Edition and its working well for me, however I'm wondering if somebody can recommend a more general, almost classic book to read casually alongside to help cement the fundamentals in place. As I said, I'm for the most part a beginner and the only education I've had is this and briefly one other technical book, so I'm sure there must be some "must reads" out there that give me a more substantial context for the basics of either Ruby on Rails, Ruby, objective oriented programming, or programming in general. What books helped you grasp a deeper and more rounded understanding of your skills as a programmer? All suggestions are welcome and appreciated.

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  • How to build Gantt chart from a set of Redmine tickets without filling dates in all of them?

    - by Alexander Gladysh
    Redmine 1.1.1 I've created a set of tickets for a new project. In each issue I filled Subject, Description and Estimated time fields. I also filled blocks/blocked by dependencies in Related issues. But the Gantt chart for this project is empty (that is, it contains all the tasks, but does not contain any "bars" for them). I need to get a Gantt chart (or any other visual representation) to show to other project members. I'd hate to type all that information again into OpenProj. Is there a way to get a serviceable Gantt chart from the Redmine? Update: In the answers below I read that to get working Gantt chart I have to input start date and due date manually for each issue. I believe that this information should be inferred automatically from start date of first ticket (first — depenency-wise), estimated time of each ticket, dependency graph, resource assignment and working hours calendar. Just as it happens in any minimally sane Gantt chart project management tool. To enter this information by hand and to keep it up-to-date manually as the project evolves is insane waste of time. Is there a way to generate Gantt chart from the set of Redmine tickets without filling in all this information manually? (Solutions involving data export + import in sane tool or involving existing plugins are perfectly acceptable.)

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  • What is the most effective way to add functionality to unfamiliar, structurally unsound code?

    - by Coder
    This is probably something everyone has to face during the development sooner or later. You have an existing code written by someone else, and you have to extend it to work under new requirements. Sometimes it's simple, but sometimes the modules have medium to high coupling and medium to low cohesion, so the moment you start touching anything, everything breaks. And you don't feel that it's fixed correctly when you get the new and old scenarios working again. One approach would be to write tests, but in reality, in all cases I've seen, that was pretty much impossible (reliance on GUI, missing specifications, threading, complex dependencies and hierarchies, deadlines, etc). So everything sort of falls back to good ol' cowboy coding approach. But I refuse to believe there is no other systematic way that would make everything easier. Does anyone know a better approach, or the name of the methodology that should be used in such cases?

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  • Are there any resources on how to identify problems that could best be solved with templates?

    - by sap
    I decided to improve my knowledge in template meta-programming. I know the syntax and rules and been playing with counteless examples from online resources. I understand how powerful templates can be and how much compile time optimization they can provide but I still cant "think in templates", I can't seem to know by myself if a certain problem could be best solved with templates and if it can, how to adapt that problem to templates. Is there some kind of online resource or book that teaches how to identify problems that could best be solved with templates and how to adapt that problem?

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  • Does BizSpark preclude you from accepting funding elsewhere?

    - by Clay Shannon
    I am going to embark very soon on a software venture (have been a consultant and employee up until now). I see advantages in signing up for Microsoft's BizSpark. However, I wonder if doing so would preclude me from accepting funding from some equity-esque arrangements potentially available via crowdfunding. I know BizSpark's legal agreement probably spells this out, but it's about a gazillion pages long, so I'm hoping somebody here has existing knowledge of this so I don't have to spend a lot of time reading legalese.

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  • Scala factory pattern returns unusable abstract type

    - by GGGforce
    Please let me know how to make the following bit of code work as intended. The problem is that the Scala compiler doesn't understand that my factory is returning a concrete class, so my object can't be used later. Can TypeTags or type parameters help? Or do I need to refactor the code some other way? I'm (obviously) new to Scala. trait Animal trait DomesticatedAnimal extends Animal trait Pet extends DomesticatedAnimal {var name: String = _} class Wolf extends Animal class Cow extends DomesticatedAnimal class Dog extends Pet object Animal { def apply(aType: String) = { aType match { case "wolf" => new Wolf case "cow" => new Cow case "dog" => new Dog } } } def name(a: Pet, name: String) { a.name = name println(a +"'s name is: " + a.name) } val d = Animal("dog") name(d, "fred") The last line of code fails because the compiler thinks d is an Animal, not a Dog.

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