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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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
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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
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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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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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2 answers
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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
260 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 ...
wrschneider's user avatar
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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
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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
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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
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1 answer
186 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 (...
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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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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
397 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
154 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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5 answers
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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
309 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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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
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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
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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
229 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
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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
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2 answers
542 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
789 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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2 answers
657 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
358 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
128 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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2 answers
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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
347 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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1 answer
811 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
294 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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2 answers
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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
230 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
143 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
125 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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2 answers
948 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
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-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
7 votes
2 answers
4k 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
292 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
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3 votes
1 answer
155 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
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5 votes
2 answers
387 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
108 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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5 votes
3 answers
682 views

How could a computer program do anything if everything is immutable?

I feel this is a bad question because I probably do not understand what I am talking about. In my effort to learn about functional programming, I became stumped on understanding the idea of immutable ...
Julian's user avatar
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4 votes
3 answers
839 views

Is this extensive usage of closure a known (anti-)pattern? And does it have a name?

I often use function closures for storing data (e.g. database URL), which doesn't change between function calls. Is this an (anti-)pattern? Does it have a name? While developing apps, which recieve ...
Sebastian DonnerWolfBach's user avatar
7 votes
3 answers
960 views

Functional architecture with lots of I/O

I'm learning about "Functional Core, Imperative Shell" as espoused by Gary Bernhardt in his talk about "Boundaries". In reality, it seems like these ideas have been known for a ...
Maletor's user avatar
  • 179
16 votes
10 answers
6k views

Are immutable objects important only in multi-threaded applications and if so, how are shared immutable objects useful?

I think the answer to the first part of my question is, "yes" -- no point in making objects immutable in a single-threaded application (or I guess in a multi-threaded application if that ...
releseabe's user avatar
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-1 votes
1 answer
167 views

Refactoring: Pythonic way of reducing the subclasses?

background: so, I am working on an NLP problem. where I need to extract different types of features based on different types of context from text documents. and I currently have a setup where there is ...
ultron's user avatar
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