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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Checking in four directions for board game win

I have the following code which I would like to simplify in Haskell, although I'm not sure how. I recall that I can use monads to simplify a case chain when the result of the case leads onto a next ...
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61 views

Converting imperative style user input menu to functional programming style

I am currently trying to teach myself scala by rewriting projects from my intro CS class, which was taught in C++. In addition to just learning the syntax I am trying to gain understanding of how ...
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432 views

Printing removed items using lambdas and streams

I'm struggling to make my lambdas readable. I've seen various approaches. Below are three different examples that all do the same thing. Forgive the example: I suspect there are better actual ...
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45 views

“Invert” a JavaScript object hash whose values are arrays to produce a new object hash with keys as the elements of those original value vectors

Background lodash and underscore have an invert function that takes an object hash and converts it to a new one, which has keys as the input object's values and ...
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10 views

Multitenant Cassandra Query in Clojure

The following code handles querying for user data in a multitenant Cassandra database. Each tenant has their own keyspace and within that keyspace data about each tenants users is stored. This code ...
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1answer
61 views

Streaming Collatz

Challenge The recent question The 3n + 1 algorithm for a range inspired me to investigate a Java-8 dependent streaming mechanism for solving the programming challenge: For any two numbers ...
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1answer
31 views

Performance of parsing math functions

I wrote the following code as part of a larger application. This code takes a string that defines a mathematical function on such as r,y x[0], x[1] etc. or any ...
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1answer
109 views

Abstracting the process of finding the index of the maximum in Python

Suppose I want to find the index of the maximal value of a given sequence. In Matlab, this is: [value, index] = max(x) In Python, I would abstract the following ...
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40 views

2D lattice random walk plots in functional style

To practice writing code in the functional programming style, I wrote a program to plot two-dimensional lattice random walks. I'd appreciate any feedback about how to improve its "functionaliness". ...
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1answer
67 views

“Data Abstraction” and “Abstract Data Type” for a rational number [closed]

Below is implementation 1 of data abstraction for rational number using functional paradigm written in Python: ...
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3answers
125 views

Optimization of stack frame usage with recursion

For the given below exercise: Here is one method to check if a number is prime: ...
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2answers
57 views

Function returning higher order function

For the below given exercise: Define a function cycle which takes in three functions as arguments: f1, f2, f3. cycle will then return another function. The returned fuction should take in an ...
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1answer
44 views

File-to-fully qualified class name function

My instincts are telling me a seasoned Scala programmer will find my code less than optimal. As will no doubt be obvious, I'm a Java guy who has just started in with Scala. Is there a more ...
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1answer
63 views

Extracting tuples from Excel sheet

My code have too much nested option processing which makes it ugly. But it has an advantage it has no side effect and typesafe. ...
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3answers
63 views

Prime factorization of an integer

I have just started learning functional programming (Haskell) for fun after using imperative languages my whole life. I am looking for quick and simple tips from pros on how the particular code I just ...
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71 views

Test runner for Scala problems

I'm learning Scala and could use another set of eyes on the code below. I'm creating a test runner for the 99 scala problems set. I figure between actually solving the problems and working through the ...
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2answers
372 views

Failing fast by raising an exception with a custom message

This is a script that utilizes lazy exception throwing. What I do is decorate a function that might throw an exception to throw an exception with a formatted string. ...
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46 views

Using interface for generated functions or just create plain functions

I was wondering which code might be better. I'm abstracting away the rote code as follows: ...
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3answers
135 views

Functional programming approach to repeated function application

Control like if..else and while If \$f\$ is a numerical function and \$n\$ is a positive integer, then we can form the ...
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2answers
68 views

Summation and product functions using functional paradigm

Below is the problem: Show that both summation and product are instances of a more general function, called accumulate, with the following signature: ...
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2answers
56 views

Functional-style linked list written in C

For my Operating Systems class, I needed a linked list data structure and didn't have one already written. During the course of thinking about how to implement a linked list again (it had been a ...
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1answer
113 views

Counting Lines and Sum of Lines

I have a small function that when passed a str that names a file that contains a program; it returns a 2-tuple with the number of the non-empty lines in that program, and the sum of the lengths of all ...
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1answer
44 views

UpdateGame function for Tetris

I am writing a Tetris game while learning Haskell and I'm trying to make the following code more concise and easier to read. How can I improve it? Note that the function is not finished yet (There is ...
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49 views

Natural sorting/comparing algorithm in TypeScript

This code sorts string that may contain numbers in natural order, that's it, "item 2" comes before than "item 10". It currently ignores case. I plan to implement options to handle case sensitivity and ...
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4answers
209 views

Hailstone Sequences in Python

For the problem given: Douglas Hofstadter’s Pulitzer-prize-winning book, Gödel, Escher, Bach, poses the following mathematical puzzle. Pick a positive integer \$n\$ as the start. If \$n\$ ...
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1answer
51 views

Lightweight TicTacToe in F#

This is more of a 'model' of TicTacToe, as you'll see it's not "gameified" in the sense that it will allow for inputs and outputs nor will it record any "active" state of the game but those things are ...
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186 views

Print “n” number of “hello world”

I had come up with the following code: ...
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141 views

N-Queens functional

I'm trying to get a better grip on the new functional possibilities of Java 8. As an example, I took this very elegant Haskell snippet: ...
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277 views

Am I thinking functionally in these simple Haskell functions?

I'm learning Haskell using the University of Pennsylvania's online materials. I'm a few lessons in and was looking for some feedback about whether I'm thinking functionally enough or porting over my ...
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62 views

Popping from a list in state while a condition is true

I'm dealing with data that stores its state as a String, treating the string like a stack. I also have to combine that with error handling. To that end, I'm using ...
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83 views

Universal memoization decorator

I've just written a simple caching / memoization python decorator. It's purpose is to cache what the function returns for all the arguments combinations it's been ever invoked with. So, if, say, we ...
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68 views

List.containsSlice

In an effort to strengthen my functional programming, I'm reading Functional Programming in Scala. One of the assignments is to implement a function that does the same operation as ...
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104 views

Haskell monads: sum of primes

They say you cannot get out of the monad, but I need to use the result (at least for assertions / unit tests). But print how does it do it? Otherwise, I worked ...
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1answer
58 views

Reacting to Boolean state in reactive ViewModels

When this ViewModel loads we kick off the IsAuthenticatedCommand: If the result of ...
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210 views

Checking for balanced parentheses

I wrote a method to check if each parenthesis in a string is closed. It should take into account the order in which a parenthesis is presented, e.g. "hello)goodbye(" should return false even though ...
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60 views

Remove items, resize columns, shuffle a list

I'm at the very beginning of starting to learn object-oriented programming patterns in JavaScript and PHP. Up until now I've always coded in a purely functional pattern. I'm doing a lot of reading, ...
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1answer
98 views

Factory template method for generalized functors

(A quick note on terminology: I use 'generalized functor' to refer to a functor that can be initialized from any callable entity, similar to the definition from Alexandrescu's Modern C++ Design. I use ...
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89 views

Idiomatic Scala for nested map/flatmap

Does anybody have an idea on how to make this code more idiomatic? I tried to use scalaz Traverse, but it didn't really help. Given the types and method signatures: ...
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Using my own Optional type with fold method in groovy

I have written an Optional type in groovy roughly based on java8s Optional. I implemented and use a fold method and would like to know if it can be improved. First, ...
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72 views

Generating a game board with squares in a rectangle

I am trying to generate a game board (similar to a Monopoly board). I am new to Scala and am thinking that there may be a better way to do this. But improvements to the code are also welcome. ...
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1answer
99 views

Making PHP composable and look functional

I've found myself on numerous occasions needing to with large text-files, where joining this on that, and filtering this out on arbitrary conditions. The first couple of times, this turned into a ...
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227 views

Evaluating Valid Date

I want to write a function which returns true if a selected date is smaller than the current date, else return false. This function is working as expected but I want to know the best possible way to ...
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2answers
103 views

zipWith function in Scala

My implementation works, but it looks very ugly. Curious to see how it's better implemented. The zipWith function takes a list of lists (...
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3answers
71 views

Removing nested blocks from a string

I wrote this function in scala that uses tail recursion to remove nested blocks from a text. Usage examples: ...
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1answer
181 views

Converting an object to an array of objects

I've written a method that takes an object whose keys are arrays and converts it to an array of objects. I feel like the code is fairly complex, after waiting a week or so and revisiting it, I don't ...
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2answers
53 views

Including references in onResume Lifecycle

What's a more concise way to do this? It's way too verbose for my taste. ...
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1answer
72 views

Function to get NGrams fast in Haskell

Is this a good way to get all sublists of a sequence/list that have a given length? An inefficient way to do it would be something like ...
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2answers
144 views

jsperf for js objects vs array tuples

I'm getting more and more into programming js in a functional manner which makes heavy use of multiple returns via tuples (especially useful with recursion). Also, a pattern that I use often is ...