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• Should "closed as duplicate" software programming be extreme or functional? [migrated]

  - by Web Developer

  I'm a web developer loving this site for it's potential, and it's Coffee look . I was reading a great question, that is this: click here and noticed 8 moderators tagged it as DUPLICATED! The question was closed! Obviously it isn't and I'm going to explain why if needed but it can be seen: the question is unique, is the case/story of a young who have SPECIFIC experience with C++ , VB and Assembler and asking, knowing this specifications an answer (It is not a general question like "hey I'm young can I do the programmer??") Let me know your opinion! do you think this question should or should not be closed? And let's think about also the people not only the "data" and "cases covered" ... do you think this is important too? or is better to keep a place where people doesn't count?

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• How do functional languages handle a mocking situation when using Interface based design?

  - by Programmin Tool

  Typically in C# I use dependency injection to help with mocking; public void UserService { public UserService(IUserQuery userQuery, IUserCommunicator userCommunicator, IUserValidator userValidator) { UserQuery = userQuery; UserValidator = userValidator; UserCommunicator = userCommunicator; } ... public UserResponseModel UpdateAUserName(int userId, string userName) { var result = UserValidator.ValidateUserName(userName) if(result.Success) { var user = UserQuery.GetUserById(userId); if(user == null) { throw new ArgumentException(); user.UserName = userName; UserCommunicator.UpdateUser(user); } } ... } ... } public class WhenGettingAUser { public void AndTheUserDoesNotExistThrowAnException() { var userQuery = Substitute.For<IUserQuery>(); userQuery.GetUserById(Arg.Any<int>).Returns(null); var userService = new UserService(userQuery); AssertionExtensions.ShouldThrow<ArgumentException>(() => userService.GetUserById(-121)); } } Now in something like F#: if I don't go down the hybrid path, how would I test workflow situations like above that normally would touch the persistence layer without using Interfaces/Mocks? I realize that every step above would be tested on its own and would be kept as atomic as possible. Problem is that at some point they all have to be called in line, and I'll want to make sure everything is called correctly.

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• functional-style datatypes in Python

  - by Danny Roberts

  For anyone who's spent some time with sml, ocaml, haskell, etc. when you go back to using C, Python, Java, etc. you start to notice things you never knew were missing. I'm doing some stuff in Python and I realized what I really want is a functional-style datatype like (for example) datatype phoneme = Vowel of string | Consonant of voice * place * manner datatype voice = Voiced | Voiceless datatype place = Labial | Dental | Retroflex | Palatal | Velar | Glottal datatype manner = Stop | Affricate | Fricative | Nasal | Lateral type syllable = phoneme list Does anyone have a particular way that they like to simulate this in Python?

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• Seeking Functional Programming Lexicon

  - by Randall Schulz

  Hi, Knowing the argot of a field helps me a lot, especially since it allows me to converse intelligently with those who know a lot more than I, so I would like to find a good lexicon of Functional Programming terms. E.g., I repeatedly encounter these: Functor, Arrow, Category, Kleisli, Monad, Monoid, a veritable zoo of Morphisms, etc. I also notice many of these appear with prefixes such as "covariant", "co-", "endo-" etc. Of these, I can say I actually understand Monoid and Covariant and sort of get Monad, but the rest are still gibberish to me. (Note that I don't mean this list as exhaustive and I'm not looking to have these defined or described for me here, I'm looking for learning resources.) Can someone point me towards an FP lexicon? It need not be on-line, as long as it's possible to find it (and it's not a rare volume for which I'd have to pay many tens of dollars).

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• Setting up functional Tests in Flex

  - by Dan Monego

  I'm setting up a functional test suite for an application that loads an external configuration file. Right now, I'm using flexunit's addAsync function to load it and then again to test if the contents point to services that exist and can be accessed. The trouble with this is that having this kind of two (or more) stage method means that I'm running all of my tests in the context of one test with dozens of asserts, which seems like a kind of degenerate way to use the framework, and makes bugs harder to find. Is there a way to have something like an asynchronous setup? Is there another testing framework that handles this better?

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• Functional languages targeting the LLVM

  - by Matthew

  Are there any languages that target the LLVM that: Are statically typed Use type inference Are functional (i.e. lambda expressions, closures, list primitives, list comprehensions, etc.) Have first class object-oriented features (inheritance, polymorphism, mixins, etc.) Have a sophisticated type system (generics, covariance and contravariance, etc.) Scala is all of these, but only targets the JVM. F# (and to some extent C#) is most if not all of these, but only targets .NET. What similar language targets the LLVM?

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• How does functional programming work?

  - by Headcrab

  I'm used to imperative/OO programming (know C, C++, Python, PHP, etc.). I wanted to get into functional programming but there are some things unclear to me. Take for example the languages F# and Haskell: How do you implement loops? By recursion? Eew. What about conditions? How can you get by without variables? I mean.. What do we have RAM for.. storing variables, right?

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• Functional languages & support for memoization

  - by Joel

  Do any of the current crop of popular functional languages have good support for memoization & if I was to pick one on the strength of its memoisation which would you recommend & why? Update: I'm looking to optimise a directed graph (where nodes could be functions or data). When a node in the graph is updated I would like the values of other nodes to be recalculated only if they depend the node that changed. Update2: require free or open-source language/runtime.

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• Scala, make my loop more functional

  - by Pengin

  I'm trying to reduce the extent to which I write Scala (2.8) like Java. Here's a simplification of a problem I came across. Can you suggest improvements on my solutions that are "more functional"? Transform the map val inputMap = mutable.LinkedHashMap(1->'a',2->'a',3->'b',4->'z',5->'c') by discarding any entries with value 'z' and indexing the characters as they are encountered First try var outputMap = new mutable.HashMap[Char,Int]() var counter = 0 for(kvp <- inputMap){ val character = kvp._2 if(character !='z' && !outputMap.contains(character)){ outputMap += (character -> counter) counter += 1 } } Second try (not much better, but uses an immutable map and a 'foreach') var outputMap = new immutable.HashMap[Char,Int]() var counter = 0 inputMap.foreach{ case(number,character) => { if(character !='z' && !outputMap.contains(character)){ outputMap2 += (character -> counter) counter += 1 } } }

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• Purely functional equivalent of weakhashmap?

  - by Jon Harrop

  Weak hash tables like Java's weak hash map use weak references to track the collection of unreachable keys by the garbage collector and remove bindings with that key from the collection. Weak hash tables are typically used to implement indirections from one vertex or edge in a graph to another because they allow the garbage collector to collect unreachable portions of the graph. Is there a purely functional equivalent of this data structure? If not, how might one be created? This seems like an interesting challenge. The internal implementation cannot be pure because it must collect (i.e. mutate) the data structure in order to remove unreachable parts but I believe it could present a pure interface to the user, who could never observe the impurities because they only affect portions of the data structure that the user can, by definition, no longer reach.

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• Functional equivalent of if (p(f(a), f(b)) a else b

  - by oxbow_lakes

  I'm guessing that there must be a better functional way of expressing the following: def foo(i: Any) : Int if (foo(a) < foo(b)) a else b So in this example f == foo and p == _ < _. There's bound to be some masterful cleverness in scalaz for this! I can see that using BooleanW I can write: p(f(a), f(b)).option(a).getOrElse(b) But I was sure that I would be able to write some code which only referred to a and b once. If this exists it must be on some combination of Function1W and something else but scalaz is a bit of a mystery to me! EDIT: I guess what I'm asking here is not "how do I write this?" but "What is the correct name and signature for such a function and does it have anything to do with FP stuff I do not yet understand like Kleisli, Comonad etc?"

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• Handling incremental Data Modeling Changes in Functional Programming

  - by Adam Gent

  Most of the problems I have to solve in my job as a developer have to do with data modeling. For example in a OOP Web Application world I often have to change the data properties that are in a object to meet new requirements. If I'm lucky I don't even need to programmatically add new "behavior" code (functions,methods). Instead I can declarative add validation and even UI options by annotating the property (Java). In Functional Programming it seems that adding new data properties requires lots of code changes because of pattern matching and data constructors (Haskell, ML). How do I minimize this problem? This seems to be a recognized problem as Xavier Leroy states nicely on page 24 of "Objects and Classes vs. Modules" - To summarize for those that don't have a PostScript viewer it basically says FP languages are better than OOP languages for adding new behavior over data objects but OOP languages are better for adding new data objects/properties. Are there any design pattern used in FP languages to help mitigate this problem? I have read Phillip Wadler's recommendation of using Monads to help this modularity problem but I'm not sure I understand how?

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• C# functional quicksort is failing

  - by Rubys

  I'm trying to implement quicksort in a functional style using C# using linq, and this code randomly works/doesn't work, and I can't figure out why. Important to mention: When I call this on an array or list, it works fine. But on an unknown-what-it-really-is IEnumerable, it goes insane (loses values or crashes, usually. sometimes works.) The code: public static IEnumerable<T> Quicksort<T>(this IEnumerable<T> source) where T : IComparable<T> { if (!source.Any()) yield break; var pivot = source.First(); var sortedQuery = source.Skip(1).Where(a => a.CompareTo(source.First()) <= 0).Quicksort() .Concat(new[] { pivot }) .Concat(source.Skip(1).Where(a => a.CompareTo(source.First()) > 0).Quicksort()); foreach (T key in sortedQuery) yield return key; } Can you find any faults here that would cause this to fail?

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• Flowcharting functional programming languages

  - by Sadface

  Flowcharting. This ancient old practice that's been in use for over 1000 years now, being forced upon us poor students, without any usefulness (or so do I think). It might work well with imperative, sequentially running languages, but what about my beloved functional programming? Sadly, I'm forced to create a flow chart for my programm (that is written in Haskell). I imagine it being easy for something like this: main :: IO () main = do someInput <- getLine let upped = map toUpper someInput putStrLn upped Which is just 3 sequenced steps, fetching data, uppercasing it, outputting it. Things look worse this time: main :: IO () main = do someInput <- fmap toUpper getLine putStrLn someInput Or like this: main :: IO () main = interact (map toUpper) Okay, that was IO, you can handle that like an imperative language. What about pure functions? An actual example: onlyMatching :: String -> [FilePath] -> [FilePath] onlyMatching ext = filter f where f name = lower ('.' : ext) == (lower . takeExtension $ name) lower = map toLower How would you flowchart that last one?

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• Problem with routes in functional testing

  - by Wishmaster

  Hi, I'm making a simple test project to prepare myself for my test. I'm fairly new to nested resources, in my example I have a newsitem and each newsitem has comments. The routing looks like this: resources :comments resources :newsitems do resources :comments end I'm setting up the functional tests for comments at the moment and I ran into some problems. This will get the index of the comments of a newsitem. @newsitem is declared in the setup ofc. test "should get index" do get :index,:newsitem_id => @newsitem assert_response :success assert_not_nil assigns(:newsitem) end But the problem lays here, in the "should get new". test "should get new" do get new_newsitem_comment_path(@newsitem) assert_response :success end I'm getting the following error. ActionController::RoutingError: No route matches {:controller=>"comments", :action=>"/newsitems/1/comments/new"} But when I look into the routes table, I see this: new_newsitem_comment GET /newsitems/:newsitem_id/comments/new(.:format) {:action=>"new", :controller=>"comments"} Can't I use the name path or what I'm doing wrong here? Thanks in advance.

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• Best Practices for Source Control Dependencies

  - by VirtuosiMedia

  How do you handle source control setup of a project that has dependency on a separate framework or library? For example, Project A uses Framework B. Should Project A also include the code from Framework B in its repository? Is there a way for it to be included automatically from a different repository or would I have to updated it manually? What are the general approaches are usually taken for this scenario? Assume that I control the repositories for both Project A and Framework B and that the source code for both is not compiled. Any resources or suggestions would be greatly appreciated. I'm currently using Subversion (on a very basic level), but I would like to switch to Mercurial so that I can try out Kiln with Fogbugz. Edit: In Mercurial, would you use parent repositories for this function?

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• Parallel Tasking Concurrency with Dependencies on Python like GNU Make

  - by Brian Bruggeman

  I'm looking for a method or possibly a philosophical approach for how to do something like GNU Make within python. Currently, we utilize makefiles to execute processing because the makefiles are extremely good at parallel runs with changing single option: -j x. In addition, gnu make already has the dependency stacks built into it, so adding a secondary processor or the ability to process more threads just means updating that single option. I want that same power and flexibility in python, but I don't see it. As an example: all: dependency_a dependency_b dependency_c dependency_a: dependency_d stuff dependency_b: dependency_d stuff dependency_c: dependency_e stuff dependency_d: dependency_f stuff dependency_e: stuff dependency_f: stuff If we do a standard single thread operation (-j 1), the order of operation might be: dependency_f -> dependency_d -> dependency_a -> dependency_b -> dependency_e \ -> dependency_c For two threads (-j 2), we might see: 1: dependency_f -> dependency_d -> dependency_a -> dependency_b 2: dependency_e -> dependency_c Does anyone have any suggestions on either a package already built or an approach? I'm totally open, provided it's a pythonic solution/approach. Please and Thanks in advance!

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• Rails: How do I included gem dependencies?

  - by marienbad

  This is a noob question: How do I add gems to my rails app in a way that I can just copy my app's directory structure to a remote location and have it just work, with all the gems I depend on installed and available?

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• Using native dependencies inside Maven

  - by Gili

  A POM dependency contains native libraries (DLLs inside a JAR file). How do I programmatically look up the path of the downloaded JAR file so I can pass it into "java.library.path"?

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• minimal cover for functional dependencies

  - by user2975836

  I have the following problem: AB -> CD H->B G ->DA CD-> EF A -> HJ J>G I understand the first step (break down right hand side) and get the following results: AB -> C AB -> D H -> B G -> D G -> A CD -> E CD -> F A -> H A -> J J -> G I understand that A - h and h - b, therefore I can remove the B from AB - c and ab - D, to get: A -> C A -> D H -> B G -> D G -> A CD -> E CD -> F A -> H A -> J J -> G The step that follows is what I can't compute (reduce the left hand side) Any help will be greatly appreciated.

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• dependent: :destroy is not deleting dependencies from views

  - by jxdx

  Projects have many rooms. When I delete a project from the view, the associated rooms are not deleted. Rooms also have many products which should also be deleted when a project is deleted. Project class class Project < ActiveRecord::Base belongs_to :user has_many :rooms, dependent: :destroy has_many :products, through: :rooms end Projects Controller class ProjectsController < ApplicationController def destroy @project = current_user.projects.find(params[:id]) if @project.delete redirect_to user_projects_path(@project.user) end end end Rooms Controller class RoomsController < ApplicationController def destroy @room = Room.find(params[:id]) if @room.delete redirect_to root_path end end The delete link in the projects show view. = link_to "Delete", project_room_path(room.project, room), method: :delete, data: { confirm: "Are you sure?" }, title: room.title, class: "btn btn-danger"

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• Deployable dependencies in Visual Studio 2010 SP1 Beta

  - by DigiMortal

  One new feature that comes with Visual Studio 2010 SP1 Beta is support for deployment references. Deployment reference means that you can include all necessary DLL-s to deployment package so your application has all assemblies it needs to run with it in deployment package. In this posting I will show you how to use deployment dependencies. When I open my ASP.NET web application I have new option for references when I right-click on my web project: Add Deployable Dependencies… If you select it you will see dialog where you can select dependencies you want to add to your project package. When packages you need are selected click OK. Visual Studio adds new folder to your project called _bin_DeployableAssemblies. Screenshot on right shows the list of assemblies added for ASP.NET Pages and Razor. All DLL-s required to run ASP.NET MVC 3 with Razor view engine are here. I am not sure if NuGet.Core.dll is required in production but if it is added then let it be there. Deploy to Azure I tried to deploy my ASP.NET MVC project that uses Razor to Windows Azure after adding deployable references to my project. Deployment went fine and web role instance started without any problems. The only DLL reference I made as local was the one for System.Web.Mvc. All Razor stuff came with deployable dependencies. Conclusion Visual Studio support for deployable dependencies is great because this way component providers can build definitions for their components so also assemblies that are loaded dynamically at runtime will be in deployment package.

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• What is a Non-Functional Requirement?

  - by atconway

  In my breakdown of work I have to define work against 'Functional' and 'Non-Functional' design elements / work in my applications. I read the description from Wikipedia here: https://en.wikipedia.org/wiki/Non-functional_requirement but as typical the description did not speak exactly to me to clear up my understanding. Can someone please explain in terms of an example when creating an application from scratch, what would be defined as a 'Non-Functional' requirement?

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• Ubuntu 9.10 + LXDE Error unmet dependencies

  - by skg

  I am working on Ubuntu 9.10 + LXDE as my current project. I am finding it difficult to install any new packages on this OS. For example, I need to install OpenCv package for qt webcam application, but every time it gives unmet dependencies error.And when i try to install dependencies it again show some more dependencies and so on and forms a circular loops. for example: sudo apt-get install libcv-dev .. .... The following packages have unmet dependencies: libcv-dev: Depends: libhighgui-dev (=1.0.0-6.2ubuntu1) but it is not going to installed. E: Broken packages Then I try to install libhighgui-dev as follow: sudo appt-get install libhighgui-dev .. ... The following packages have unmet dependencies: libhighgui-dev: Depends: libgtk2.0-dev but it is not going to installed E: Broken packages And this goes on never ending. Please suggest me something, as i have googled a lot and did not found any help. It may be , i m missing some primary packages to be installed.But how to find it? Any suggestion/help/link will be really appreciated. Thanks in Advance.

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• Functional vs. Non-Functional Requirements vs Design ideas in an SRS

  - by Nicholas Chow

  For a school project, I had to create a SRS for a "fictional" application. However they did not show us what it exactly entails, and were very vague with explanations. The SRS asked of us has to have at least 5 functional requirements, 5 non functional requirements and 1 constraint. Now I have tried my best to make one however I there are still some uncertainties left, I hope you experts can tell me whether or not I am thinking in the right direction. I will keep on updating this posts as I have questions regarding requirements that are vague to me, thank you all in advance for making SRS more clear for me FR1 Registration of Organizer FR1 describes the registration of an Organizer on CrowdFundum FR1.1 The system shall display a registration form on the website. FR1.2 The system shall require a Name, Username, Document number passport/ID card, Address, Zip code, City, Email address, Telephone number, Bank account, Captcha code on the registration form when a user registers. FR1.3 The system shall check whether the Name, Username, Document number passport/ID card, Address, Zip code, City, Email address, Telephone number, Bank account, Captcha code are filled out correctly within 1 seconds after a user submits the registration form. FR1.4 The system shall display an error message containing: “Registration could not be completed” to the subscriber within 1 seconds after the system check of the registration form was unsuccessful. FR1.5 The system shall send a verification email containing a verification link to the subscriber within 30 seconds after the system check of the registration form was successful. FR1.6 The system shall add the newly registered Organizer to the user base within 5 seconds after the verification link was accessed. Questions: FR1.1 Is this a functional requirement, or have I incorporated design idea in it by using "shall display on website". If so what would be a better way to write it? FR1.2 Is this better written in one requirement, or should I write each condition as a seperate requirement? FR1.3-1.5 Are these functional requirements or did I mix some non functional elements in it? How is it better phrased? FR1.3-1.6 Are these all correct functional requirements? As in free of ambiguity, complete, implementation free etc.

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