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• How to call a different post to a different controller in Rails Functional Test

  - by Snehal

  I want to make a post request to a different controller inside my functional test which is intended for a particular controller. However the post method in ActiveController class just takes the method to be called, it doesn't take the controller name to be called. Any ideas how to invoke a different controller?

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• Rails functional testing without migrations

  - by Brian D.

  The name pretty much says it all. Does anyone know how to accomplish functional testing when you are not using migrations in Rails? I'd be open to any advice or third party libraries (if there are any). I thought of creating my own plugin to address this but it seems like a pretty big task and would rather not do this unless necessary. Thanks in advance.

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• Learning functional/clojure programming - practical excersises?

  - by Konrad Garus

  I'm learning functional programming with Clojure. What practical excersises can you recommend? Online repositories with solutions would be perfect. One idea I can think of is going through all the popular algorithms on sorting, trees, graphs etc. and implementing them in Clojure myself. While it could work, it may be pretty steep and I'm likely to do it inefficiently (compared to someone who knows what she's doing).

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• Functional programming approach for Java's input/output streams

  - by Elazar Leibovich

  I'm using Java's DataInputStream with scala to parse some simple binary file (which is very bad exprerience due to the lack of unsigned types, even in scala, but that's a different story). However I find myself forced to use mutable data structure, since Java's streams are inherently state preserving entities. What's a good design to wrap Java's streams with nice functional data structure?

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• functional dependencies vs type families

  - by mhwombat

  I'm developing a framework for running experiments with artificial life, and I'm trying to use type families instead of functional dependencies. Type families seems to be the preferred approach among Haskellers, but I've run into a situation where functional dependencies seem like a better fit. Am I missing a trick? Here's the design using type families. (This code compiles OK.) {-# LANGUAGE TypeFamilies, FlexibleContexts #-} import Control.Monad.State (StateT) class Agent a where agentId :: a -> String liveALittle :: Universe u => a -> StateT u IO a -- plus other functions class Universe u where type MyAgent u :: * withAgent :: (MyAgent u -> StateT u IO (MyAgent u)) -> String -> StateT u IO () -- plus other functions data SimpleUniverse = SimpleUniverse { mainDir :: FilePath -- plus other fields } defaultWithAgent :: (MyAgent u -> StateT u IO (MyAgent u)) -> String -> StateT u IO () defaultWithAgent = undefined -- stub -- plus default implementations for other functions -- -- In order to use my framework, the user will need to create a typeclass -- that implements the Agent class... -- data Bug = Bug String deriving (Show, Eq) instance Agent Bug where agentId (Bug s) = s liveALittle bug = return bug -- stub -- -- .. and they'll also need to make SimpleUniverse an instance of Universe -- for their agent type. -- instance Universe SimpleUniverse where type MyAgent SimpleUniverse = Bug withAgent = defaultWithAgent -- boilerplate -- plus similar boilerplate for other functions Is there a way to avoid forcing my users to write those last two lines of boilerplate? Compare with the version using fundeps, below, which seems to make things simpler for my users. (The use of UndecideableInstances may be a red flag.) (This code also compiles OK.) {-# LANGUAGE MultiParamTypeClasses, FunctionalDependencies, FlexibleInstances, UndecidableInstances #-} import Control.Monad.State (StateT) class Agent a where agentId :: a -> String liveALittle :: Universe u a => a -> StateT u IO a -- plus other functions class Universe u a | u -> a where withAgent :: Agent a => (a -> StateT u IO a) -> String -> StateT u IO () -- plus other functions data SimpleUniverse = SimpleUniverse { mainDir :: FilePath -- plus other fields } instance Universe SimpleUniverse a where withAgent = undefined -- stub -- plus implementations for other functions -- -- In order to use my framework, the user will need to create a typeclass -- that implements the Agent class... -- data Bug = Bug String deriving (Show, Eq) instance Agent Bug where agentId (Bug s) = s liveALittle bug = return bug -- stub -- -- And now my users only have to write stuff like... -- u :: SimpleUniverse u = SimpleUniverse "mydir"

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• How do functional language gui bindings work?

  - by Roman A. Taycher

  Do they typically use non functional aspects of the language (including mutable variables). Are there other strategies? Could you describe them?

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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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• 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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• 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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• https:// search results appearing on Google for purely http:// site

  - by hydrurga

  I started weeding through my site's search results from Google today, using a site: search, to determine if there are any links that cause 404s and thus need redirecting. To my amazement I noticed numerous https:// results relating to various pages. My site doesn't have a SSL certificate, doesn't serve such pages, doesn't internally link to https:// pages, doesn't include any such files in its sitemap.xml and, for all of these, never has. I decided to do a Google search for https://<my site> and found one site that incorrectly refers to the root of my site with a https:// prefix - I will try to contact them to get them to correct this. I'm not sure however how Googlebot managed to index the non-root files as https://. I can't find any external links to them and surely, without certification, Googlebot should have stalled at the first request? I've just added the following lines to the site's .htaccess (although the surfer still has to navigate through the browser's "This site is a security risk. Abandon hope all ye who enter here!" message(s) first to get there): RewriteEngine On RewriteCond %{HTTPS} on RewriteRule ^(.*)$ http://www.<my site>.org/$1 [R=301,L] replacing <my site> with my domain name. My big question is this though - I would like to use the Google Webmaster Tools Remove URLs feature to remove the https:// pages from the index. Can I be guaranteed that this will only remove the https:// versions of each relevant page and not the valid http:// versions? My thanks to anyone who can help me out with this particular question and the issue in general.

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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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• Functional Java

  Functional programming with functors and object streams in Java

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• Debugging F# code and functional style

  - by Roger Alsing

  I'm new to funcctional programming and have some questions regarding coding style and debugging. I'm under the impression that one should avoid storing results from funcction calls in a temp variable and then return that variable e.g. let someFunc foo = let result = match foo with | x -> ... | y -> ... result And instead do it like this (I might be way off?): let someFunc foo = match foo with | x -> ... | y -> ... Which works fine from a functionallity perspective, but it makes it way harder to debug. I have no way to examine the result if the right hand side of - does some funky stuff. So how should I deal with this kind of scenarios?

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