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• Program to find canonical cover or minimum number of functional dependencies

  - by Sev

  I would like to know if there is a program or algorithm to find canonical cover or minimum number of functional dependencies? For example: If you have: R = (A,B,C) <-- these are tables: A,B,C And dependencies: A ? BC B ? C A ? B AB ? C The canonical cover (or minimum number of dependencies) is: A ? B B ? C Is there a program that can accomplish this? If not, any code/pseudocode to help me write one would be appreciated. Prefer in Python or Java.

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• Functional Specifications vs. Requirements Document

  - by KP

  Guys, Currently in my comp., there are some changes going on regarding project documentation. There is a LOT of time and effort spent on discussing functional specs vs. requirements doc. However, I don't think anyone here understands the reason why you would use one over the other. Therefore, I don't understand the difference myself. Can someone shed some light on this matter plz? If you have links to articles, blog posts, etc. that would be helpful too. Thanks

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• Using FlexMock in a rails functional test.

  - by dagda1

  Hi, I have the following index action: class ExpensesController < ApplicationController def index() @expenses = Expense.all end end I want to mock the call to all in a functional test. I am using flexmock and have written the following test: require 'test_helper' require 'flexmock' require 'flexmock/test_unit' class ExpensesControllerTest < ActionController::TestCase test "should render index" do flexmock(Expense).should_receive(:all).and_return([]) get :index assert_response :success assert_template :index assert_equal [], assigns(:presentations) end end The problem is the the last assertion fais with the following error message: <[] expected but was nil I am confused what I am doing wrong. Should this not work? Cheers Paul

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• Need a push in the right direction, to write my first functional test in Rails

  - by Jason

  I've read quiet a bit of documentation over the last few days about testing in Rails, I'm sitting down to write my first real test and not 100% sure how to tie what I have learned together to achieve the following functional test (testing a controller) I need to send a GET request to a URL and pass 3 parameters (simple web-service), if the functionality works the keyword true is simply returned, otherwise the keyword false is returned - its in only value returned & not contained in any <div>, <span> or other tags. The test should assert that if "true" is returned the test is successful. This is probably very simple so apologies for such a non-challenging question. If anyone could point me in the write direction on how I can get started, particularly how I can test the response, I'd be very grateful!

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• Minimal files to run a fully-functional PostgreSQL in Windows

  - by fxam

  I would like to bundle PostgreSQL into my application. I downloaded the PostgreSQL 9 beta zip without the installer. After extraction, there are 8 directories. I found out that at least the following directories are required to run PostgreSQL properly, at least under my experiments. bin lib share The question is, are the above three directories really sufficient to run a fullly functional PostgreSQL? Do I need the 'include' and 'symbols' directories? Also, can I remove 'share\locale' if I don't use these locales?

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• Why are my functional tests failing?

  - by Mongus Pong

  I have generated some scaffolding for my rails app. I am running the generated tests and they are failing. for example test "should create area" do assert_difference('Area.count') do post :create, :area => { :name => 'area1' } end assert_redirected_to area_path(assigns(:area)) end This test is failing saying that : 1) Failure: test_should_create_area(AreasControllerTest) [/test/functional/areas_controller_test.rb:16]: "Area.count" didn't change by 1. <3 expected but was <2. There is only one field in the model : name. I am populating this so it cant be because I am failing to populate the only field. I can run the site and create an area with the name 'area1'. So reality is succeeding, but the test is failing. I cant ask why its failing, because Im sure theres not enough information here for anyone here to know why. Im just stuck at knowing what avenues to go down to work out why the test is failing. Even putting puts into the code dont print out... What steps can I take to track this down?

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• Javascript functional inheritance with prototypes

  - by cdmckay

  In Douglas Crockford's JavaScript: The Good Parts he recommends that we use functional inheritance. Here's an example: var mammal = function(spec, my) { var that = {}; my = my || {}; // Protected my.clearThroat = function() { return "Ahem"; }; that.getName = function() { return spec.name; }; that.says = function() { return my.clearThroat() + ' ' + spec.saying || ''; }; return that; } var cat = function(spec, my) { var that = {}; my = my || {}; spec.saying = spec.saying || 'meow'; that = mammal(spec, my); that.purr = function() { return my.clearThroat() + " purr"; }; that.getName = function() { return that.says() + ' ' + spec.name + ' ' + that.says(); }; return that; }; var kitty = cat({name: "Fluffy"}); The main issue I have with this is that every time I make a mammal or cat the JavaScript interpreter has to re-compile all the functions in it. That is, you don't get to share the code between instances. My question is: how do I make this code more efficient? For example, if I was making thousands of cat objects, what is the best way to modify this pattern to take advantage of the prototype object?

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• Automated UAT/functional tests on Swing applications without source code

  - by jas

  Our team is now working on a big Swing application. Our job basically focuses on writing extensions to the existing framework. A typical job would be adding a new panel/ or adding a new tab with some extra functionalities that suit our need. It seems FEST can help a lot in terms of unit-test our code. I am going to try it out this week. But the question here is if there is a way to do automated functional testing on the whole application. In another word, we do not only need to test our code but also the framework. After all, UAT is the most important part. I am currently considering decompiling the jar files we got into source code then we can identify the components and then use FEST. So, before I get started to give this approach a shot, I think I just ask for ideas and inspirations here. There must be people who have done similar things before. Would be nice if I could learn from the veterans who fought against this before . Thanks,

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• Finding the shortest path between two points on a grid, using Haskell.

  - by esperantist

  This is a problem that I can easily enough solve in a non-functional manner. But solving it in Haskell is giving me big problems. Me being inexperienced when it comes to functional programming is surely a reason. The problem: I have a 2D field divided into rectangles of equal size. A simple grid. Some rectangles are empty space (and can be passed through) while others are impassable. Given a starting rectangle A and a destination rectangle B, how would I calculate the shortest path between the two? Movement is possible only vertically and horizontally, in steps a single rectangle large. How would I go about accomplishing this in Haskell? Code snippets certainly welcome, but also certainly not neccessary. And links to further resources also very welcome! Thanks!

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• Challenge: Neater way of currying or partially applying C#4's string.Join

  - by Damian Powell

  Background I recently read that .NET 4's System.String class has a new overload of the Join method. This new overload takes a separator, and an IEnumerable<T> which allows arbitrary collections to be joined into a single string without the need to convert to an intermediate string array. Cool! That means I can now do this: var evenNums = Enumerable.Range(1, 100) .Where(i => i%2 == 0); var list = string.Join(",",evenNums); ...instead of this: var evenNums = Enumerable.Range(1, 100) .Where(i => i%2 == 0) .Select(i => i.ToString()) .ToArray(); var list = string.Join(",", evenNums); ...thus saving on a conversion of every item to a string, and then the allocation of an array. The Problem However, being a fan of the functional style of programming in general, and method chaining in C# in particular, I would prefer to be able to write something like this: var list = Enumerable.Range(1, 100) .Where(i => i%2 == 0) .string.Join(","); This is not legal C# though. The closest I've managed to get is this: var list = Enumerable.Range(1, 100) .Where(i => i%2 == 0) .ApplyTo( Functional.Curry<string, IEnumerable<object>, string> (string.Join)(",") ); ...using the following extension methods: public static class Functional { public static TRslt ApplyTo<TArg, TRslt>(this TArg arg, Func<TArg, TRslt> func) { return func(arg); } public static Func<T1, Func<T2, TResult>> Curry<T1, T2, TResult>(this Func<T1, T2, TResult> func) { Func<Func<T1, T2, TResult>, Func<T1, Func<T2, TResult>>> curried = f => x => y => f(x, y); return curried(func); } } This is quite verbose, requires explicit definition of the parameters and return type of the string.Join overload I want to use, and relies upon C#4's variance features because we are defining one of the arguments as IEnumerable rather than IEnumerable. The Challenge Can you find a neater way of achieving this using the method-chaining style of programming?

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• Is OO design's strength in semantics or encapsulation?

  - by Phil H

  Object-oriented design (OOD) combines data and its methods. This, as far as I can see, achieves two great things: it provides encapsulation (so I don't care what data there is, only how I get values I want) and semantics (it relates the data together with names, and its methods consistently use the data as originally intended). So where does OOD's strength lie? In constrast, functional programming attributes the richness to the verbs rather than the nouns, and so both encapsulation and semantics are provided by the methods rather than the data structures. I work with a system that is on the functional end of the spectrum, and continually long for the semantics and encapsulation of OO. But I can see that OO's encapsulation can be a barrier to flexible extension of an object. So at the moment, I can see the semantics as a greater strength. Or is encapsulation the key to all worthwhile code?

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• Is JBehave a good choice for Web Service Automated Testing?

  - by Vanchinathan

  Hi All, We have a requirement at my workplace to automate the webservice testing. We have been using QTP scripts to do so. We as a team, Kind of leaning towards Jbehave as a choice. Is JBehave a good choice for web service functional testing automation? We do use Soap UI to test manually. But we are planning to automate the functional and regression testing to reduce the release cycle time. Suggestions welcome.

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• Appending an element to a collection using LINQ

  - by SRKX

  I am trying to process some list with a functional approach in C#. The idea is that I have a collection of Tuple<T,double> and I want to change the Item 2 of some element T. The functional way to do so, as data is immutable, is to take the list, filter for all elements where the element is different from the one to change, and the append a new tuple with the new values. My problem is that I do not know how to append the element at the end. I would like to do: public List<Tuple<T,double>> Replace(List<Tuple<T,double>> collection, T term,double value) { return collection.Where(x=>!x.Item1.Equals(term)).Append(Tuple.Create(term,value)); } But there is no Append method. Is there something else?

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• How can I represent a line of music notes in a way that allows fast insertion at any index?

  - by chairbender

  For "fun", and to learn functional programming, I'm developing a program in Clojure that does algorithmic composition using ideas from this theory of music called "Westergaardian Theory". It generates lines of music (where a line is just a single staff consisting of a sequence of notes, each with pitches and durations). It basically works like this: Start with a line consisting of three notes (the specifics of how these are chosen are not important). Randomly perform one of several "operations" on this line. The operation picks randomly from all pairs of adjacent notes that meet a certain criteria (for each pair, the criteria only depends on the pair and is independent of the other notes in the line). It inserts 1 or several notes (depending on the operation) between the chosen pair. Each operation has its own unique criteria. Continue randomly performing these operations on the line until the line is the desired length. The issue I've run into is that my implementation of this is quite slow, and I suspect it could be made faster. I'm new to Clojure and functional programming in general (though I'm experienced with OO), so I'm hoping someone with more experience can point out if I'm not thinking in a functional paradigm or missing out on some FP technique. My current implementation is that each line is a vector containing maps. Each map has a :note and a :dur. :note's value is a keyword representing a musical note like :A4 or :C#3. :dur's value is a fraction, representing the duration of the note (1 is a whole note, 1/4 is a quarter note, etc...). So, for example, a line representing the C major scale starting on C3 would look like this: [ {:note :C3 :dur 1} {:note :D3 :dur 1} {:note :E3 :dur 1} {:note :F3 :dur 1} {:note :G3 :dur 1} {:note :A4 :dur 1} {:note :B4 :dur 1} ] This is a problematic representation because there's not really a quick way to insert into an arbitrary index of a vector. But insertion is the most frequently performed operation on these lines. My current terrible function for inserting notes into a line basically splits the vector using subvec at the point of insertion, uses conj to join the first part + notes + last part, then uses flatten and vec to make them all be in a one-dimensional vector. For example if I want to insert C3 and D3 into the the C major scale at index 3 (where the F3 is), it would do this (I'll use the note name in place of the :note and :dur maps): (conj [C3 D3 E3] [C3 D3] [F3 G3 A4 B4]), which creates [C3 D3 E3 [C3 D3] [F3 G3 A4 B4]] (vec (flatten previous-vector)) which gives [C3 D3 E3 C3 D3 F3 G3 A4 B4] The run time of that is O(n), AFAIK. I'm looking for a way to make this insertion faster. I've searched for information on Clojure data structures that have fast insertion but haven't found anything that would work. I found "finger trees" but they only allow fast insertion at the start or end of the list. Edit: I split this into two questions. The other part is here.

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• Instantiating Java object with a passed in method

  - by superluminary

  It's been a few years since I've been heavily into Java. Coming back to it I'm seeing this pattern all over the place: ratingBar.setOnRatingBarChangeListener(new OnRatingBarChangeListener() { public void onRatingChanged(RatingBar ratingBar, float rating, boolean fromUser) { // do work } }); This looks more like Functional programming to me. It's a nice pattern but how is it possible to pass a method like this? In the old days a class was a class, and once compiled there was little you could do to it. My questions are: Can anyone let me know what this pattern is called? How can I write a class that can be instantiated in this way. Are there any other useful examples of functional patterns that have made their way into Java? What do I need to Google to read more about this? Thanks.

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• need some concrete examples on user stories, tasks and how they relate to functional and technical specifications

  - by gideon

  Little heads up, Im the only lonely dev building/planning/mocking my project as I go. Ive come up with a preview release that does only the core aspects of the system, with good business value and I've coded most of the UI as dirty throw-able mockups over nicely abstracted and very minimal base code. In the end I know quite well what my clients want on the whole. I can't take agile-ish cowboying anymore because Im completely dis-organized and have no paper plan and since my clients are happy, things are getting more complex with more features and ideas. So I started using and learning Agile & Scrum Here are my problems: I know what a functional spec is.(sample): Do all user stories and/or scenarios become part of the functional spec? I know what user stories and tasks are. Are these kinda user stories? I dont see any Business Value reason added to them. I made a mind map using freemind, I had problems like this: Actor : Finance Manager Can Add a Financial Plan into the system because well thats the point of it? What Business Value reason do I add for things like this? Example : A user needs to be able to add a blog article (in the blogger app) because..?? Its the point of a blogger app, it centers around that feature? How do I go into the finer details and system definitions: Actor: Finance Manager Action: Adds a finance plan. This adding is a complicated process with lots of steps. What User Story will describe what a finance plan in the system is ?? I can add it into the functional spec under definitions explaining what a finance plan is and how one needs to add it into the system, but how do I get to the backlog planning from there? Example: A Blog Article is mostly a textual document that can be written in rich text in the system. To add a blog article one must...... But how do you create backlog list/features out of this? Where are the user stories for what a blog article is and how one adds/removes it? Finally, I'm a little confused about the relations between functional specs and user stories. Will my spec contain user stories in them with UI mockups? Now will these user stories then branch out tasks which will make up something like a technical specification? Example : EditorUser Can add a blog article. Use XML to store blog article. Add a form to add blog. Add Windows Live Writer Support. That would be agile tasks but would that also be part of/or form the technical specs? Some concrete examples/answers of my questions would be nice!!

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• Scheme Infix to Postfix

  - by Cody

  Let me establish that this is part of a class assignment, so I'm definitely not looking for a complete code answer. Essentially we need to write a converter in Scheme that takes a list representing a mathematical equation in infix format and then output a list with the equation in postfix format. We've been provided with the algorithm to do so, simple enough. The issue is that there is a restriction against using any of the available imperative language features. I can't figure out how to do this in a purely functional manner. This is our fist introduction to functional programming in my program. I know I'm going to be using recursion to iterate over the list of items in the infix expression like such. (define (itp ifExpr) ( ; do some processing using cond statement (itp (cdr ifExpr)) )) I have all of the processing implemented (at least as best I can without knowing how to do the rest) but the algorithm I'm using to implement this requires that operators be pushed onto a stack and used later. My question is how do I implement a stack in this function that is available to all of the recursive calls as well?

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• Web Automation Tool

  - by Aaron

  I've realized I need a full-fledged browser automation tool for testing user interactions with our JavaScript widget library. I was using qunit, starting with unit testing and then I unwisely started incorporating more and more functional tests. That was a bad idea: trying to simulate a lot of user actions with JavaScript. The timing issues have gotten out of control and have made the suite too brittle. Now I spend more time fixing the tests, then I do developing. Is it possible to find a browser automation tool that works in: Windows XP: IE6,7,8, FF3 OSX: Safari, FF3 ? I've looked into SeleniumIDE and RC, but there seems to be some IE8 problems. I've also seen some things about Google's WebDriver, which confusingly seems to work with Selenium. Our organziation has licenses for IBM's Rational Functional Tester, but I don' think that will work on the MAC. The idea is to try to run tests on all the browsers our organization supports. Doable? Are my requirements unrealistic? Any recommendations as far as software to try? Thanks!

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• std::bind overload resolution

  - by bpw1621

  The following code works fine #include <functional> using namespace std; using namespace std::placeholders; class A { int operator()( int i, int j ) { return i - j; } }; A a; auto aBind = bind( &A::operator(), ref(a), _2, _1 ); This does not #include <functional> using namespace std; using namespace std::placeholders; class A { int operator()( int i, int j ) { return i - j; } int operator()( int i ) { return -i; } }; A a; auto aBind = bind( &A::operator(), ref(a), _2, _1 ); I have tried playing around with the syntax to try and explicitly resolve which function I want in the code that does not work without luck so far. How do I write the bind line in order to choose the call that takes the two integer arguments?

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• When to use closure?

  - by shahkalpesh

  I have seen samples of closure from - http://stackoverflow.com/questions/36636/what-is-a-closure Can anyone provide simple example of when to use closure? Specifically, scenarios in which closure makes sense? Lets assume that the language doesn't have closure support, how would one still achieve similar thing? Not to offend anyone, please post code samples in a language like c#, python, javascript, ruby etc. I am sorry, I do not understand functional languages yet.

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• Abstraction is for lame programmers ? [closed]

  - by Zaban Khuli

  Hi, there's this senior developer in my company who's (in his own opinion) a pretty good C programmer. I happen to be from functional background (ML, to be specific) and so for me composition and abstraction are the two basic elements of programming. But this MrSmartyPants has got some kind of superiority complex and he'd always argue with me that abstraction is for lame programmers and _real_ programmers do not need it. Is it a problem with this guy or all C programmers have this opinion that abstraction is for lame programmers?

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• Can immutable be a memory hog?

  - by ciscoheat

  Let's say we have a memory-intensive class like an Image, with chainable methods like Resize() and ConvertTo(). If this class is immutable, won't it take a huge amount of memory when I start doing things like i.Resize(500, 800).Rotate(90).ConvertTo(Gif), compared to a mutable one which modifies itself? How to handle a situation like this in a functional language?

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• Code organization in an FP application

  - by fig-gnuton

  What are common or recommended ways to organize an application written in a functional language? Along what lines would you decide to create separate files, modules, directories, etc.?

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• Monad in plain English?

  - by fig-gnuton

  In terms that an OOP programmer would understand (without any functional programming background), what is a monad? What problem does it solve and what are the most common places it's used?

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• What's the main difference between F# and Occaml?

  - by prosseek

  I heard that F# is actually a modification of Occaml. Is this true? If so, F# is just Occaml on .NET? If not, what's the major difference between the two functional languages?

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