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Code Golf

Questions tagged [functional-programming]

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This tag is for challenges related to the functional programming paradigm.

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A monad is a type that wraps another type, that represents the available operations on the wrapped type. Monads have the following associated operations, where M is ...
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Task I need a function that accept string and return a function f1. That f1 function should also accept string and return a <...
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The golfing language Jelly has a built-in ƭ called "tie", that cycles through a list of functions every time it's called. For example, ...
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The goal of this challenge is to compare how well different programming languages support functional programming, by seeing how much code it takes to implement BLC8, the simplest functional ...
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In this programming-puzzle, your goal is to write the following function in JavaScript, using (essentially) point-free (tacit) programming: (f) => void(f()) ...
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A fixed-point combinator is a higher order function \$\mathrm{fix}\$ that returns the fixed point of its argument function. If the function \$f\$ has one or more fixed points, then $$\mathrm{fix} f=f(\...
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Ruby has a strange operator, .., called flip-flop (not to be confused with the range operator, which looks the same). Used in a loop, flip-flop takes two conditions ...
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The persistence of a number \$x = d_1d_2d_3...d_n\$, with \$d_1 \ne 0\$, under some function \$f : \mathbb N_0 \times \mathbb N_0 \to \mathbb N_0\$ is defined as the number of applications of \$f\$ to ...
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Curry is the Language of the Month this month and some users are starting to get into it, so let's get some tips together. Haskell and Curry are similar in a lot of ways and a lot of tips for Haskell ...
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The \$\text{argwhere}\$ function takes a list of values and a predicate/boolean function as arguments and returns a list of indices where the predicate function returns true in the input list. For ...
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Background K functions have a feature called projection, which is essentially partial application of values to a function. The syntax for projections is a natural extension of the regular function ...
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Background Supplementary reading 1, Supplementary reading 2 Linear lambda calculus is a limited form of lambda calculus, where every bound variable must be used exactly once. For example, ...
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Task Haskell's and Scala's standard libraries have an unfold function that builds a list from an initial state s and a function <...
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Background Lambda calculus is a model of computation using lambda terms. A variable \$x\$ is a lambda term. If \$E\$ is a lambda term, the lambda abstraction \$\lambda x. E\$ is a lambda term. If \$...
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Think of cleave as the conceptual inverse of map. If map applies a function to each number in a list... map([1, 2, 3], x -> x * 5) -> ...
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Background The fixed-point combinator \$\textsf{fix}\$ is a higher-order function that computes the fixed point of the given function. $$\textsf{fix}\ f = f\ (\textsf{fix}\ f)$$ In terms of ...
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Background Combinatory logic is a system where a term is written using a finite set of combinators and function application between terms, and reduction rules are defined for each combinator. The well-...
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Background Combinatory logic is a system where a term is written using a finite set of combinators and function application between terms, and reduction rules are defined for each combinator. The well-...
Bubbler's user avatar
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26 votes
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Given: a blackbox function \$f : \mathbb N \to \mathbb N\$, a list of positive integers \$L\$, and a list of indices \$I\$, apply \$f(x)\$ to the elements of \$L\$ at the indices specified in \$I\$. ...
caird coinheringaahing's user avatar
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Over is a higher-order function in multiple languages such as APL (⍥). It takes 2 functions and 2 values as arguments, applies the first function to both values, ...
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zipwith is a functional construct that takes three arguments: one binary function and two lists of the same length, and returns a single list where each element is ...
caird coinheringaahing's user avatar
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23 votes
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I don't like curry. Help me reverse the effects of this evil question - Make me some curry - by uncurrying functions. Task Given a blackbox curried function, output its uncurried equivalent. The ...
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9 answers
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Church Subtraction Lambda calculus has always been a fascination of mine and the emergent behaviors of passing functions into each other is delightfully complex. Church numerals are representations ...
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Church booleans A Church boolean is a function that returns x for true and y for false where ...
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This challenge is about Haskell point-free style polynomial functions. Although you don't need to know Haskell language to do this challenge, Haskellers might have an advantage here. Point-free ...
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The Dirichlet convolution is a special kind of convolution that appears as a very useful tool in number theory. It operates on the set of arithmetic functions. Challenge Given two arithmetic ...
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Introduction I have some JavaScript code that uses Array.prototype.map to map an array of functions fns to their return values: ...
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Motivation: Sometimes certain items in a list don't count towards your totals. For example, counting plane passengers in rows, where babies sit on a parent's laps. Challenge: write a program to split ...
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Having a function f that takes arguments x1, x2, …, xn                         &...
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Using your language of choice, write a function that takes a variable number of arguments and returns the number of arguments it was called with. Specifics: Your language needs to support variadic ...
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Recently, my reputation was 25,121. I noticed that each digit grouping (i.e. the numbers separated by commas) was a perfect square. Your challenge is, given a non-...
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Inspiration. Given (by any means): A two-argument (or single argument consisting of a two-element list) black box function, f: ℤ+ × ℤ+ → ℤ+ (input and output are 1,...
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What is the shortest way we can express the function f(a,b)(c,d)=(a+c,b+d) in point-free notation? pointfree.io gives us ...
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Given an integer \$x_1\$ and some black box function \$f: ℤ → ℤ\$ find a fixed point of \$f\$ in the sequence defined by \$x_{k+1} := f(x_k)\$. Details A value \$x\$ is said to be a fixed point of \$...
flawr's user avatar
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16 votes
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Are there any functional programming languages designed for code golfing? I know that golfscript and CJam fulfill the same category for stack based, but I couldn't find a functional code golfing ...
Christopher King's user avatar
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Write a function, f, that takes in a positive integer and returns a function. The new function returned should be identical to f...
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1 answer
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The λ-calculus, or lambda calculus, is a logical system based on anonymous functions. For example, this a λ-expression: λf.(λx.xx)(λx.f(xx)) However, for the ...
Esolanging Fruit's user avatar
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Introduction and Credit Today without a fancy prelude: Please implement takewhile. A variation of this (on a non-trivial data structure) was an assignment at my ...
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Challenge Find an expression, at most 100 bytes long, with the longest type signature. Rules Any statically typed language with type inference is allowed The type must be non-ambiguous, but otherwise ...
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map is a very basic yet important function in functional programming. All FP programming languages have it built-in but it is always fun to see how shortly you can ...
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11 answers
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Your company is just getting started on a project, and for the first time you decided to go use a functional programming code-style. However your boss is really diffident and doesn't want to use built-...
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8 votes
6 answers
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Background (F#) Let there be trees: type Tree<'T> = Node of 'T * Tree<'T> list Now lets fold them nicely with a function called... ...
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4 answers
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EDIT: As some of you suspected, there was a bug in the official interpreter: the order of composition in . was reversed. I had two versions of the interpreter, and ...
Zgarb's user avatar
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Develop a program which takes two arrays of decimal numbers, and compare the sum of whole numbers only and the decimal part. If the sums of the whole numbers are the same, and the decimal parts of ...
andyra42's user avatar
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9 votes
5 answers
437 views

The Haskell function biSp has type signature ...
dspyz's user avatar
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21 votes
3 answers
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I got the following question at a test: Write a function f with the following type a -> b -> (a -> b). ...
Radu Stoenescu's user avatar
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5 votes
12 answers
620 views

You are given two functions \$g(x)\$ and \$h(x)\$, each of which takes an integer \$x\$ and returns the number \$ax + b\$ (where \$a\$ and \$b\$ are integers defined in the function). Your task is to ...
Joe Z.'s user avatar
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13 votes
9 answers
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Write a fixed point combinator in as few characters as possible, in the language of your choice. free form (i.e., whatever's shortest): whole program, actual function, code snippet you may not use ...
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