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 program state. In this style of programming, side effects and mutable data are deprecated.

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Provide functional-programming style solution for 2D Array - DS challenge

Problem Statement: Given a 6×6 2D Array, arr: 1 1 1 0 0 0 0 1 0 0 0 0 1 1 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 We define an hourglass in A to be ...
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2answers
2k views

Message-formatting code with pluralization, revised to be more functional

I'm a C++ dev, and I've recently started working my way through Clean Code*. Whenever I encounter an example I think I could improve, I try to re-implement it in C++. On pp. 28-29 there is an example ...
2
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1answer
50 views

Toggling the background color of a page using JavaScript closures

This question is to see if I can get some input on the "design pattern" I tried to implement here. I'm just learning about closure in JavaScript and I think I'm starting to get it. I'm wondering if ...
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2answers
74 views

Function invocation every second time

Recently I got test task at the project, it is fairly simple: ...
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2answers
67 views

Count character 'a' in first n characters of indefinitely repeating string s

Problem statement: Lilah has a string, s, of lowercase English letters that she repeated infinitely many times. Given an integer, n, find and print the number of letter a's in the first n ...
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2answers
70 views

Counting valleys traversed below sea level, given elevation changes

Problem Statement: Gary is an avid hiker. He tracks his hikes meticulously, paying close attention to small details like topography. During his last hike he took exactly steps. For every step ...
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3answers
88 views

Functional CSV Parser

I've been starting to migrate some C++ code from imperative to more of a functional style. I'm new to functional programming so I'm trying to get a sense of how well this code fits into the functional ...
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2answers
204 views

Emulation of SE's text input control for tags

Introduction I used React to write a component, which is meant to be a faithful emulation of the input for "Tags" which you see at the top of every question/topic on SE. Why this project? If you're ...
2
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1answer
55 views

JSON Parser, pulls data from a JSON file for analysis

This is the first time I have programmed something that I will actually personally use, so I am happy about that. I tried to write good code whilst applying functional programming concepts. So no ...
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1answer
49 views

Currying in Lua

Just whipped up this quick curry function in Lua, as a building block for partial application and memoization. Any feedback is appreciated. It takes two arguments; ...
3
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1answer
70 views

Pre-calculate the winning combinations for an n-sized tic tac toe board using C++ functional programming

This code pre-calculates the winning combinations for an n-sized tic tac toe board. I first created my function using an imperative approach. This is just how I naturally write code most of the time....
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1answer
30 views

A game that deals a high card to one of two players [closed]

So for my class, I have to design a game that will deal out one card to for each player. I also need to use functions to accomplish this one for the high card game, and another for the face value of ...
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A tiny library implementing the Elm Architecture in C++

Elm is a pure functional language for the front-end. It enforces an architecture that allows programs to stay pure in an event-based setting. This simple header-only library implements a variant of ...
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41 views

Binary Trie in F#

I have this little exercise writing a binary trie in F#. In C# it can be done in few lines, but here it became more complicated than I had expected (especially the ...
8
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3answers
370 views

Story-based adventure with functions and relationships

This is a story-based adventure program I coded by myself (forgive the length). It took a long time but it was fun. It includes loading times, changes in relationships, relationship levels, storyline ...
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2answers
40 views

Seeking the seeds for writing tidy event handlers in JS

I'm seeking a critique of the simple program below, which displays two counters and increments them through a button, using D3.js. In real life of course no one has a need for displaying buttons that ...
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1answer
47 views

Print a Connect 4 grid based on some rules for each cell

In a game of Connect4: we start with an empty grid two players place pieces X and O on the grid the first player to achieve 4 pieces in a line wins! this is a text based console game Here is the ...
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21 views

Create a template literal tag to remove whitespace from a string

I'm just getting into functional programming (as in, just started reading the book) and as practice I'm trying to refactor a past answer I wrote to fit in line with the functional style. The ...
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0answers
70 views

Async in Railway Oriented Programming in F#

In F# the Railway Oriented Programming pattern can be implemented synchronously using the Result<'t,'terr> type as result value for functions, so they can be ...
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1answer
22 views

Two-Part Hurdle Model Simulation with Bootstrapping

I am running a simulation study where I am using two-part hurdle modeling on different effect sizes. I tried to stream-line my code for the best optimization including foreach loops and ...
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1answer
32 views

Typescript monad for data being loaded

I have been struggling to make typescript happy about the types. I am pulling data from our backend API and I wanted to give context to the data. Basically it is a monad with 4 shapes: Initial (...
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1answer
42 views

Perform KS-test on Random Number Generator [closed]

I've just started practicing Functional Programming in Scala in some days. This is the code I used to perform KS-test on a random number generator. ...
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4answers
1k views

Find all letter Combinations of a Phone Number

The task is taken from LeetCode Given a string containing digits from 2-9 inclusive, return all possible letter combinations that the number could represent. A mapping of digit to letters (just ...
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0answers
38 views

Given time intervals determine if a person could attend all meetings

The task is taken from LeetCode Given an array of meeting time intervals consisting of start and end times [[s1,e1],[s2,e2],...] ...
3
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2answers
48 views

Functional Programming Hangman Practice

Recently, I have been trying to improve my functional programming skills and understanding. While at work today, my coworkers and I were playing Hangman in a group chat. I thought of a program that ...
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0answers
40 views

Merge k Sorted Lists

The task is taken from LeetCode Merge k sorted linked lists and return it as one sorted list. Analyze and describe its complexity. Example: ...
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0answers
87 views

Merge Intervals in JavaScript

This task is taken from Leetcode - Given a collection of intervals, merge all overlapping intervals. Example 1: ...
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2answers
139 views

Simple function that simulates survey results based on sample size and probability

What is this: This is a simple function, part of a basic Monte Carlo simulation. It takes sample size and probability as parameters. It returns the simulation result (positive answers) plus the input ...
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0answers
67 views

Rewrite a Haskell function to be total

I've written this function to give the neighbours of a vertex in a graph: ...
6
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1answer
75 views

Given a string containing just parentheses, determine if the input string is valid

The task is taken from leetcode Given a string containing just the characters '(', ')', '{', '}', '[' and ']', determine if the input string is valid. An input string is valid if: ...
3
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3answers
46 views

Counting duration values

I have a durations as such: [{'duration': 3600}, {'duration': 3600}] And I want the output to be ...
2
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1answer
54 views

Finding the most common section from the visible cells in a collection view

My goal is to determine, of all of the currently visible cells in a collection view, which section has the most visible cells. Start by getting the index paths for the visible cells: ...
8
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1answer
136 views

Lazy, Functional Parser Combinators

Parser Combinators are the amazingly elegant way to write parsers that has evolved over on the functional programming side of the world, but have been less available or accessible for imperative ...
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1answer
70 views

Find common characters (LeetCode)

The task is taken from leetcode Given an array A of strings made only from lowercase letters, return a list of all characters that show up in all strings within the list (including duplicates). ...
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2answers
51 views

Robot Return to Origin

The task is taken from leetcode There is a robot starting at position (0, 0), the origin, on a 2D plane. Given a sequence of its moves, judge if this robot ends up at (0, 0) after it completes ...
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1answer
60 views

Is it possible to DRY these 2 methods of a tailrec Node Tree?

I have a Tree structure composed by Node class. I have to @tailrec method that are visiting up to the root. Those 2 methods ...
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2answers
45 views

Flipping an Image

The task is taken from leetcode Given a binary matrix A, we want to flip the image horizontally, then invert it, and return the resulting image. To flip ...
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0answers
15 views

Combinable filters for Python Pandas dataframe structure

This is an extension of my other question here. I have applied suggestions from 200_success in real-life problem at hand that deals with modelling extensible and ...
3
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1answer
41 views

Utmost function that takes a comparator function

I'm working through Paul Graham's "ANSI Common Lisp". In Chapter 6 (p105), he introduces the idea of utility functions. He points out these are core to bottom-up programming and reusability. He ...
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0answers
37 views

Transform vcards into contacts using functional programming in JavaScript

Context: I'm building a React app using Ramda as a helper library for functional programming. Users can import contacts into the app. These contacts can be vCards. I've written a function that: ...
3
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1answer
45 views

Grouping dates by weeks using reduce()

I am trying to implement a function groupWeeks(dates) using reduce that allows me to group an array of objects ...
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1answer
74 views

Sort Array By Parity

The task is taken from leetcode Given an array A of non-negative integers, return an array consisting of all the even elements of A, followed by all the odd elements of A. You may return any ...
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1answer
31 views

Items also occurs in a set

The task You're given strings J representing the types of stones that are jewels, and S representing the stones you have. Each character in S is a type of stone you have. You want to know how ...
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0answers
72 views

Determine whether there exists a one-to-one character mapping from one string to another

The task Determine whether there exists a one-to-one character mapping from one string s1 to another s2. For example, given s1 = abc and s2 = bcd, return true since we can map a to b, b to ...
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2answers
51 views

Sum of two numbers in array

The task You are given two non-empty arrays representing two non-negative integers. The digits are stored in reverse order and each of their items contain a single digit. Add the two numbers ...
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2answers
112 views

Roman Numbers - The Functional Way

Yet another exercise in converting values between the decimal and roman number systems. I have tried the functional way. Any comments are welcome - but I'm especially interested in answers focusing ...
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1answer
83 views

Find busiest period in building

The task You are given a list of data entries that represent entries and exits of groups of people into a building. An entry looks like this: {"timestamp": 1526579928, count: 3, "type": "...
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1answer
47 views

Find indices of two numbers such that they add up to a target

The task ...is taken from leetcode Given an array of integers, return indices of the two numbers such that they add up to a specific target. You may assume that each input would have ...
2
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1answer
77 views

Find all pairs of unique indices in a list such that the concatenation of the two words is a palindrome

The task Given a list of words, find all pairs of unique indices such that the concatenation of the two words is a palindrome. For example, given the list ...
1
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1answer
116 views

Rotate a N by N matrix by 90 degrees clockwise

The task: Given an N by N matrix, rotate it by 90 degrees clockwise. For example, given the following matrix: [[1, 2, 3], [4, 5, 6], [7, 8, 9]] you should return: [[7, 4, 1], [8, ...