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Questions tagged [functional-programming]

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 isolated.

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How to filter "locally and remotely" in functional programming

My example applies to reading and deleting files (I/O), but this is probably a common scenario (eg, keeping local and global state in sync in functional programming). I am reading in files from a ...
rpivovar's user avatar
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3 votes
3 answers
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How to "pass through" data in a functional programming pipeline so that it's accessible later on in the pipeline

I am trying to refactor some JavaScript code to use functional programming principles. I have some functions that I want to use in a series of maps. const transformedData = rawData .map(...
rpivovar's user avatar
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5 votes
3 answers
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Are "pipelines" in functional programming bad for time complexity?

This question is not meant to be a critique of functional programming, but more hoping for resources and opinions. I am refactoring some historically messy code so that it follows functional ...
rpivovar's user avatar
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4 votes
2 answers
365 views

How to handle file I/O in a for loop?

(this question is written using javascript for examples) Say I have a bunch of files that I need to access sequentially: 1.json 2.json 3.json 4.json ... Say I want to transform the data in all of ...
rpivovar's user avatar
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1 answer
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(functional programming) What do you call a function that abstracts away a group of function calls?

(this question is written from a functional javascript point of view) say you have some pure functions: function a (arg) { ... return result } function b (arg) { ... return result } function ...
rpivovar's user avatar
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2 votes
1 answer
207 views

Did the term "decorator" originate with OOP design patterns?

The Decorator pattern allows behaviour to be dynamically added to an existing object, effectively "decorating" it with new behaviour. While the pattern as formalised and named seems to have ...
Iain Galloway's user avatar
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1 answer
521 views

How could I apply the strategy pattern to a react component? [closed]

For the following component, how would I extract the unit logic to allow for composition? In my actual app I am trying to reduce the amount of logic encoded in the component and I have decided that ...
Tyler Kasper's user avatar
2 votes
1 answer
129 views

OO vs FP: What is a good approach to understanding if heavy wrapper classes should be used?

Consider a processing system which ingests objects from an external source and performs extensive processing. One example could be objects detected by a computer vision system which are then fed into ...
panlex's user avatar
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2 answers
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Why did TC39 name JavaScript's array predicate functions `some` and `every` instead of `any` and `all`?

Python, Ruby, Rust, Haskell, Kotlin, C#, C++, Perl, MATLAB, SQL, and R all call their respective array predicate checking functions any and all. Is there any record of why JavaScript's designers ...
Alex Ryan's user avatar
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6 votes
2 answers
721 views

Object immutability and persistence

While I was learning functional programming I have encounterd two for me very similar terms: immutability and persistence. Also I have read simular questions from stackoverflow, but I am still ...
DimitrijeCiric's user avatar
1 vote
3 answers
322 views

Scala Option vs. conditional branches

If I'm writing Scala functions and have to check for nulls in situations where I can't avoid it (say, working with Spark UDFs and some legacy Java types), is it better to turn things into Option or to ...
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When is the application of Kotlin infix functions appropriate? [closed]

The Kotlin language brings the simplification of function calls to the natural language. This article shows a nice example: Function: fun of(suit: Suit) = Card(this, suit) val card = Rank.QUEEN.of(...
Nikolas Charalambidis's user avatar
-2 votes
1 answer
690 views

Should I use function-based exports/imports or classes?

What would make more sense, to use functions for exports/imports: // globals/helpers.js exports.fnOne = () => {} // features/user.js const {fnOne} = require() Or class-based approach with static ...
WebrJohn's user avatar
1 vote
3 answers
1k views

Are "Distributed Enums" an Anti-pattern in non-OOP like they seem to be considered in OOP?

I have recently read about the so-called "distributed enum anti-pattern." In particular, as it relates to using enums in conditional statements. (The idea is apparently that if you were to ...
user1713450's user avatar
1 vote
1 answer
206 views

Are there any drawbacks to partial application?

Consider the following Typescript code: function exampleAction(target: Target, options: ExampleActionOptions) { // ... } export function getExampleAction(options: ExampleActionOptions) { return (...
kaan_atakan's user avatar
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385 views

How to Represent Functional Boolean

.NET Boolean type usually makes if else pair all over the code. Functional Boolean should be more like Either type. Ideally represented as Either<Unit, Unit>. However, my issues with Either type ...
TIKSN's user avatar
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1 answer
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Loosened or sequential referential transparency [closed]

I am interested in robotics programming. HW control often involves calculating the derivative or integration of the signal. It seems quite inevitable to avoid local states for such calculation. (Since ...
chanwoo ahn's user avatar
7 votes
1 answer
441 views

Can functional programming languages have deadlock conditions?

I am reading through "Clean Architecture: A Craftsman's Guide to Software Structure and Design" and it says that: All race conditions, deadlock conditions, and concurrent update problems are ...
Quantum Guy 123's user avatar
-2 votes
1 answer
165 views

Which paradigm(between OOP and Functional) should be chosen for a given task?

Which paradigm(between OOP and Functional) should be chosen for a given task ? What are the tradeoffs between these two styles ? In which case using Functional makes sense and vice versa,in which case ...
Dennis's user avatar
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17 votes
5 answers
6k views

Is there a non-deterministic function without side effects?

By definition, a pure function is deterministic + no side effect. Is there any example for a function which has no side effects, but is non-deterministic? I.e., a function without side effects, but ...
Helin Wang's user avatar
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2 answers
330 views

C# coding style, functional approach

I have thought of this for a while and I want to know what you think about this. This is more of a way to structure the code that might not be 100% object oriented and that is not the purpose. I would ...
Cowborg's user avatar
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5 votes
2 answers
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Is it normal for names in functional programming to be extremely terse?

I am working on a compilers assignment in OCaml, and the following is an example of the pre-written code in said assignment: (* Build a CFG and collection of global variable definitions from a stream *...
SRSR333's user avatar
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13 votes
8 answers
6k views

How do compilers work in a language that doesn't allow recursion?

I'm recently learning the programming language, and I wonder how compilers work when the language itself does not allow recursion, like how the compiler or the runtime checkers makes sure that there ...
csxyyyyy's user avatar
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2 votes
2 answers
328 views

Modularity vs pure functions

I often come across this dilemma in my own code and wondered if there is a term for this and if there is a single solution to it. Let me illustrate it with a pseudocode example of making a table from ...
deSKase's user avatar
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-2 votes
4 answers
237 views

Block structured iteration and recursion

Programming languages traditionally have blocks that specifically cater to controlling iteration. There is the simple while-loop: while (i < 3) {...}; Then there is the more complicated for-loop: ...
Steve's user avatar
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1 vote
2 answers
432 views

In what language does a method not return a value and a function does?

I don't know from where I got this but in my head a function returns a value and a method does not. I know that with OOP a method is a function related to a class. But I am trying to remember where I ...
houimli manel's user avatar
1 vote
2 answers
628 views

Dependency injection vs function parameter

I am working on a project that is structured in hexagonal architecture. It is a multi module gradle project where web layer is a separate module that depends on the domain module. Sample code related ...
sidgate's user avatar
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4 votes
2 answers
939 views

How to organize a chain of functions that share parameters, functional programming

When trying to follow a functional programming paradigm, I often find myself in a situation where I have a chain of functions that I would want to combine/compose somehow, but they all also take in a ...
Cordello's user avatar
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0 votes
2 answers
706 views

Should I use unnecessary function for readability sake

I am implementing if/else statement, by using function "inCase" to make it more readable: const size = 'small' const equals = str1 => str2 => str2 === str1 const inCase = (obj) => ...
Djordje Vuckovic's user avatar
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2 answers
396 views

How to model transactions in a client-side functional DDD?

I'm new to DDD and I would like to clarify some concepts. I'm thinking about DDD in the client-side. The first one is regarding transactions: My understanding is that transactions are a responsibility ...
João Otero's user avatar
1 vote
1 answer
131 views

Private types, units of measure when is it a good idea?

My question is regarding using private type in F#. Consider the case we have some application and we have some library. One may consider using units within the library, and making them private behind ...
Just_Alex's user avatar
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1 vote
2 answers
159 views

Should I add functionality by adding a new method to a class - or should I "register" the new functionality into a data structure?

I have one large class that computes ~50 different metrics (each metric has no side effects). My code is similar to this: class ReportingMetrics: def __init__(self, data:pd.DataFrame, config:dict)...
MYK's user avatar
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1 vote
0 answers
373 views

Terse finite state machines in Haskell

I'm writing a parser for a markup language in haskell, and a finite state machine fell out of my ideal API. I have code that looks a bit like this: Token = BoldWord String | Word String | ...
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0 votes
1 answer
921 views

How to test a function with several conditional nested side effects

In Python, consider a function like the following: def main(*args): value1 = pure_function1(*args) if condition(value1): value = side_effect1(value1) if value: ...
pob's user avatar
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4 votes
2 answers
300 views

Should I use classes instead of functions with a state needed for computation?

I have implemented the cows and bulls game in C++. The code: #include <cstdio> #include <cstdlib> #include <ctime> struct DigitMatches { int matches_in_right_positions; int ...
sshd's user avatar
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0 votes
2 answers
121 views

How to convert vehicle schedule time window calculation algorithm to FP

I am working on an algorithm that optimizes utilitization of a vehicle. What I have is a list of paths the vehicle is planned to take and between which times (time windows) it has to be at a certain ...
Blaž Mrak's user avatar
11 votes
6 answers
3k views

Is ad-hoc polymorphism a good practice in functional programming?

I am developing a utils data engineering package in python, and for the sake of reusability and readability, I chose the functional programming (FP) approach. Assume a key task of converting data from ...
maaniB's user avatar
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1 vote
2 answers
242 views

Connecting classes by passing method references

I am trying to find a good way of allowing two objects that are separated by a intermediate object to communicate while keeping the architecture loosely coupled. A solution I have developed is to pass ...
dda2120's user avatar
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1 vote
0 answers
146 views

How to improve maintainability and testability of a service by refactoring it into a functional style

A customer of ours has a rather large (500+ LOC) service as central part of the project. Written in C# and consisting of rather clunky large imperative style functions, I was asked to improve the test ...
Anders Bernard's user avatar
1 vote
3 answers
126 views

How to model a time-distributed process in functional programming style?

I'm searching for any formal/generic approach to modeling a process distributed in time with functional programming. Here is an example. Let's implement a very simple notification service. It accepts ...
Anthony's user avatar
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1 vote
2 answers
1k views

Should "functional core, imperative shell" approach canonically break "don't test private methods" rule?

In short, "functional core, imperative shell" can be summarized as: functional core implements logic; you unit test it. Your tests call real functions just like in production real functions ...
Coderino Javarino's user avatar
-1 votes
1 answer
97 views

Design suggestions for my simple data-analysis program

I need to create a program with the purpose of cross-referencing personal info from a spreadsheet(s), to check for conflicts of interest between clients of 3 different law firms. All of this client ...
boog's user avatar
  • 99
-1 votes
1 answer
84 views

Appropriate base type for simply typed lambda calculus

Given the following hypothetical programming language: Intended for practical programming A simply typed lambda calculus (STLC) All objects are functions, based on Church encodings I am aware that ...
Ari Fordsham's user avatar
8 votes
2 answers
5k views

Database access with functional programming

I'm interested in becoming more familiar with functional programming as a paradigm, so I'm trying to introduce a more functional style to some of my projects. I'm struggling to understand how to ...
Hassan's user avatar
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31 votes
3 answers
6k views

Definition of "functor"; Haskell vs. C++

I'm trying to understand whether the Haskell and C++ communities mean different things by the word "functor", or if there's some underlying concept that unifies the two meanings. My ...
Stephen Warren's user avatar
79 votes
10 answers
17k views

How functional programming achieves "No runtime exceptions"

How does a functional programming language, such as Elm, achieve "No runtime exceptions"? Coming from an OOP background, runtime exceptions have been part of whatever framework that is based ...
Fireburn's user avatar
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1 vote
2 answers
332 views

What is the name of "an IF-ELSE expression that returns a value"? [closed]

Some programming languages allow conditional value assignments that look like x = (IF condition THEN a ELSE b) My search-fu is failing me: how do we call such statements in the jargon of ...
Deleplace's user avatar
  • 143
3 votes
1 answer
165 views

Choosing the design of a scientific DSL: purely or impurely functional?

My aim is to create a language specific to the scientific field (which would be used mainly in the field of machine learning and physics) which would be based on the functional paradigm, a paradigm ...
Foxy's user avatar
  • 491
5 votes
2 answers
414 views

Doesn't "Always test through the public interface" contradict testing of individual composed functions?

I'm currently reading "Composing Software" by Eric Elliott, which is about functional programming in JavaScript. He states that if you compose multiple functions together, and that these ...
user1474326's user avatar
1 vote
1 answer
110 views

Unclear as to the informal definition of foldr

I've encountered the infomral definition of foldr in a couple of books. I've attached an image from Bird and Wadler's "Introduction to Functional Programming" (1988), but I've seen the same ...
Sarel's user avatar
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