Functional programming is a paradigm which attempts to solve computational problems by the chained evaluation of functions whose output is determined by their inputs rather than the programme state. In this style of programming, side effects and mutable data are deprecated and usually strictly ...

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12answers
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Why isn't functional programming more popular in the industry? Does it catch on now? [closed]

During my four years at university we have been using much functional programming in several functional programming languages. But I have also used much object oriented programming to, and in fact I ...
2
votes
2answers
575 views

Why isn't functional programming embraced more widely? [duplicate]

Possible Duplicate: Why isn't functional programming more popular in the industry? Does it catch on now? I've been working as a J2EE developer for the past 3 years and wanted to learn ...
-1
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0answers
20 views

How would you write the following bit of Elixir code passing a function to the Enum.chunk_by? [on hold]

This is the bit of code I'd like to learn how to write using the anonymous function as the second parameter to the Enum.chunk_by. Enum.chunk_by([1, 2, 2, 3, 4, 4, 6, 7, 7], &(rem(&1, 2) == ...
0
votes
0answers
44 views

How to model space in a mudlike

I am trying to make a clone of the 3-D space-modeling system from swmud This is the criteria so far: (1) Objects in space will be either ships that can move or stationary things like non-moving ...
5
votes
4answers
779 views

Why not apply Interface Segregation Principle to “extreme”

Providing that clients would typically consume just one method, though methods would be conceptually related, why not always apply the Interface Segregation Principle to the extreme and have [many] ...
39
votes
10answers
6k views

Why would a program use a closure?

After reading many posts explaining closures here I'm still missing a key concept: Why write a closure? What specific task would a programmer be performing that might be best served by a closure? ...
0
votes
2answers
133 views

Almost point-free style

Programmers often talk about point-free style. In contrast to the imperative style (pseudocode): h := function(x) { y := f(x) z := g(y) return z; } one might write the following point-free: ...
16
votes
2answers
2k views

Does Clojure have continuations/coroutines/etc?

I started programming with Python, and I was really confused by concepts like coroutines and closures. Now I think I know them on some superficial level, but I've never felt that "enlightement" ...
2
votes
1answer
60 views

Term for the opposite of the functional Compose operator

In functional programming, given a function f and a function g we can define a function . (compose): let (.) f g = fun x -> g (f x) Is there a term for the function which applies arguments in the ...
3
votes
1answer
54 views

Under what scenarios would 'functional' `Try` objects be more or less beneficial than 'rx' `Try` objects?

Definitions used by this question: 'functional' Try is what https://github.com/lambdista/try is. Success and Failure are subclasses of Try. Exceptions aren't thrown by the called function. 'rx' Try ...
33
votes
7answers
4k views

What do you call a function that's pure, meaning the same input will always return the same output, but also has side effects?

Say we have a normal pure function such as function add(a, b) { return a + b } And then we alter it such that it has a side effect function add(a, b) { writeToDatabase(Math.random()) return ...
10
votes
4answers
321 views

Is it still valid to speak about anemic model in the context of functional programming?

Most of DDD tactical design patterns belong to object-oriented paradigm, and anemic model describes the situation when all business logic is put into services rather than objects thus making them a ...
26
votes
1answer
1k views

How to implement a branch-and-bound in a functional programming language?

I am trying to write a branch and bound search on the set of all functions f: D -> R, where the domain size is small (|D| ~ 20) and the range is much bigger (|R| ~ 2^20). Initially, I came up with the ...
2
votes
6answers
229 views

How does immutability remove the need for locks when two threads are trying to update the shared state?

Okay so I read through this: Does immutability entirely eliminate the need for locks in multi-processor programming? And this was the main takeaway for me: Now, what does it get you? ...
43
votes
13answers
11k views

Why are side-effects considered evil in functional programming?

I feel that side effects are a natural phenomenon. But it is something like taboo in functional languages. What are the reasons? My question is specific to functional programming style. Not all ...
5
votes
2answers
110 views

Using queues to decouple functions/avoid direct calling?

Kind of a functional programming newbie question here: I've been reading the transcripts of some of Rich Hickey's talks, and in several of his more well-known ones, he recommends using queues as an ...
2
votes
4answers
484 views

What is Big-O notation for purely functional languages?

Is it still relevant? Instead of var result = new List<int>(); for (var i = 0; i < prev.Count; ++i) { result.Add(prev[i] * 2); } where the result.Add, prev[i], and * 2 instructions ...
56
votes
4answers
6k views

Is functional programming faster in multithreading because I write things differently or because things are compiled differently?

I'm diving into the world of functional programming and I keep reading everywhere that functional languages are better for multithreading/multicore programs. I understand how functional languages do a ...
5
votes
2answers
121 views

What is the difference between explicit parameters and closures

In F#, a tail recursive List.filter function can be implemented like: let filter f = let rec filterImpl f acc = function | [] -> List.rev acc | h :: t -> filterImpl f (if ...
49
votes
3answers
7k views

What are the biggest differences between F# and Scala?

F# and Scala are both functional programming langugages that don't force the developer to only use immutable datatypes. They both have support for objects, can use libraries written in other languages ...
1
vote
2answers
232 views

Need help with deciding elements for icon creating application

I'm trying to practice programing by creating a simple application which, I think, I can manage to do in .Net C# in Visual Studio 2010. I'm working on simple application which will let me to create ...
8
votes
2answers
276 views

How to handle complex calculated fields in an ORM

In our API we've got a few central datatypes which need to be "decorated" (so to speak) after retrieval from the database with calculated values. The database is accessed through an ORM which follows ...
1
vote
3answers
112 views

Logic Programming(Unification) vs List Comprehensions (in Functional Programming)

I found this answer on StackOverflow very clear to explain the difference beween the Logic Programming paradigm and the Functional Programming paradigm: The thing that makes logical append ...
7
votes
6answers
2k views

A programming language that does not allow IO. Haskell is not a pure language

Are there any 100% pure languages (as I describe in the Stack Overflow post) out there already and if so, could they feasibly be used to actually do stuff? i.e. do they have an implementation? I'm not ...
36
votes
7answers
15k views

Haskell AND Lisp vs. Haskell OR Lisp [closed]

I currently code with C, C++, and Python. I'm wanting to pick up a functional programming language, and right now I'm leaning toward Haskell. I do NOT want to start a "Haskell vs Lisp" war here; what ...
4
votes
1answer
170 views

JavaScript functional conversion from flat list to tree

I've been going through the RxJS tutorials http://reactivex.io/learnrx/. Almost all of the exercises involve moving from a hierarchical structure to a flat structure so I thought I'd try to do the ...
5
votes
3answers
203 views

Should databases be viewed as Monads?

Because any kind of persistence updates/inserts/deletes represents in some sense a kind of state change in a database, it makes me wonder whether databases can be considered monads. We say the same ...
2
votes
3answers
94 views

Declarative programming for deterministic real time control

Let's say you want control a motor in real time. Normally you would use a microcontroller or PC with e.g. c-programming language. So you would use an imperative approach. You tell the microcontroller ...
3
votes
1answer
94 views

Can I use maybe on multiple inputs in Haskell?

Suppose I wanted to test that both my inputs are positive. Can I do something like this? test :: Float -> Float -> Maybe Float Float test a b | a>0 && b>0 = a b | ...
7
votes
3answers
1k views

Is a function getting a value from another function considered pure?

I'm trying to figure out a way to handle default variable values when making functions without side effects and have ended up with the following: function getDefaultSeparator() { return ':'; } ...
40
votes
2answers
4k views

Why (or why not) are existential types considered bad practice in functional programming?

What are some techniques I might use to consistently refactor code removing the reliance on existential types? Typically these are used to disqualify undesired constructions of your type as well as to ...
3
votes
2answers
282 views

Shared data in functional programming

I have been working on a project in JavaScript which requires a data structure (read only), to be shared between two functions. var mySharedData = ['hours', 'minutes', 'seconds']; Now I have two ...
15
votes
5answers
2k views

Is a function immediately impure if it takes a function as a parameter?

Since the purity of an input parameter is an unknown until runtime, is a function immediately considered impure if it takes a function as an input parameter? Related: if a function applies a pure ...
4
votes
2answers
605 views

Local Updates in Persistent/Immutable Data Structures

I'm getting into ReactJS and am intrigued but also confused about persistent data structures. I love the idea, but I'm not sure how to take my MV*, Mutable, Observable Bindings experience in designing ...
9
votes
4answers
506 views

What programming problems do Monads solve? [closed]

I've read a lot of posts that explain what monads are, how unit and bind work, some of them plunging straight into category theory so abstract (for me at least) that makes the eyes bleed, some ...
10
votes
2answers
289 views

Haskell ways to the 3n+1 problem

Here is a simple programming problem from SPOJ: http://www.spoj.com/problems/PROBTRES/. Basically, you are asked to output the biggest Collatz cycle for numbers between i and j. (Collatz cycle of a ...
82
votes
5answers
18k views

Functional Programming vs. OOP [closed]

I've heard a lot of talk about using functional languages such as Haskell as of late. What are some of the big differences, pros and cons of functional programming vs. object-oriented programming?
35
votes
6answers
10k views

Workaround for Java checked exceptions

I appreciate a lot the new Java 8 features about lambdas and default methods interfaces. Yet, I still get bored with checked exceptions. For instance, if I just want to list all the visible fields of ...
3
votes
6answers
2k views

How can IO cause side effects in Functional Programming? [duplicate]

Whenever I read about Haskell, I find that IO can cause side effects. But I do not understand how it would do it? Do we mean that we are writing to a file from one lazy sequence and another lazy ...
2
votes
1answer
131 views

Enumerating the primitive recursive functions

How can I enumerate (by expression tree size, for example) all of the primitive recursive functions that map natural numbers to natural numbers in a traditional programming language like C? For ...
4
votes
8answers
666 views

One-use variables - has any language ever had them?

A principle that I follow is that, when an identifier is established, it should be a signal to the reader that the value referred to is indeed an abstraction which will be used more than once. That ...
19
votes
2answers
425 views

How different is garbage collection in pure languages?

In a pure language like Haskell, all data is immutable and no existing data structures can be changed in any way. Additionally, many algorithms on immutable data and functional programming patterns ...
1
vote
1answer
126 views

Why use tuples as function parameters in languages that support currying?

In languages that support currying, I can't think of many cases where using a tuple as function input parameters would be better than breaking the tuple apart into multiple parameters, which then ...
-2
votes
1answer
239 views

Functional programming, and pushing item to array [closed]

I'm studying functional programming and I'm having some question concerning array population. Actually, I'm trying to rebuild the Array.prototype.map function, and here's what I've got: ...
1
vote
0answers
62 views

Chronological/evolutionary positioning of Curry in relation to Haskell and Prolog

is Curry a transitional language from FP to Logic Programming (Haskell to Prolog), like Scala is a transitional language from imperative to FP (Java to Haskell)? I find it hard to come up with a ...
23
votes
4answers
3k views

Is return-type-(only)-polymorphism in Haskell a good thing?

One thing that I've never quite come to terms with in Haskell is how you can have polymorphic constants and functions whose return type cannot be determined by their input type, like class Foo a ...
1
vote
2answers
204 views

Functional Programming style: How to write functions - explicit currying, implicit currying or lamdas?

So I have been using F# for a while and studying a bit of Haskell on the side and I have realized I could rewrite the exact same function one of three different ways. Either with implicit currying, ...
2
votes
2answers
188 views

Haskell types for functions

I don't understand the answer to this question: Q: Can Haskell find a type for the function selfapply defined by: selfapply f = f f A: The function selfapply is not typeable in the simple ...
8
votes
4answers
355 views

Is there a Haskell idiom for trying several functions and stop as soon as one succeeds?

In Haskell, I can use the type a -> Maybe b to model a function that either returns a value of type b, or returns nothing (it fails). If I have types a1, ..., a(n+1) and functions f1, ..., fn, ...
1
vote
2answers
147 views

Why does Scala name monadic composition as “for comprehension”?

Not sure if it's an appropriate question, but here it goes. I know Haskell's do notation pretty well. And I realized that Scala's "for comprehension" really is just mostly the same as do notation in ...