Haskell

via Exercism

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Provider

Exercism
Pricing

Free Online Course
Languages

English
Sessions

On-Demand
Level

Advanced

Found in

Haskell is a general-purpose programming language known for being purely functional, non-strict with strong static typing and for having type inference.

Purely functional means that you don't update variables or modify state. Pure functions will always return the same value given the same input and will do nothing else. Functions that are referentially transparent are more predictable and more composable. Non-strict (somewhat like lazy) means that you can express infinite data structures. Strong static typing means that a lot of program errors are caught during compilation. Type inferencemeans that the compiler can often figure out the type of a value by itself. The compiler can also tell you if a value has conflicting types in different parts of the code.

There are more than 10,000 free third-party packages available at Hackage, the Haskell community's central package archive, and you can download them using the Stack tool that Exercism also uses.

You can also read the free book Learn You a Haskell for Great Good or follow the interactive tutorial at tryhaskell.org.

Syllabus

Hello World

The classical introductory exercise. Just say "Hello, World!".

Leap

Determine whether a given year is a leap year.

Reverse String

Reverse a given string.

Darts

Write a function that returns the earned points in a single toss of a Darts game.

Space Age

Given an age in seconds, calculate how old someone is in terms of a given planet's solar years.

Pangram

Determine if a sentence is a pangram.

Bob is a lackadaisical teenager. In conversation, his responses are very limited.

Collatz Conjecture

Calculate the number of steps to reach 1 using the Collatz conjecture.

RNA Transcription

Given a DNA strand, return its RNA Complement Transcription.

Nucleotide Count

Given a DNA string, compute how many times each nucleotide occurs in the string.

Sum of Multiples

Given a number, find the sum of all the multiples of particular numbers up to but not including that number.

Grains

Calculate the number of grains of wheat on a chessboard given that the number on each square doubles.

Acronym

Convert a long phrase to its acronym.

Strain

Implement the `keep` and `discard` operation on collections. Given a collection and a predicate on the collection's elements, `keep` returns a new collection containing those elements where the predicate is true, while `discard` returns a new collection containing those elements where the predicate is false.

Anagram

Given a word and a list of possible anagrams, select the correct sublist.

Clock

Implement a clock that handles times without dates.

Crypto Square

Implement the classic method for composing secret messages called a square code.

Luhn

Given a number determine whether or not it is valid per the Luhn formula.

Nth Prime

Given a number n, determine what the nth prime is.

Minesweeper

Add the numbers to a minesweeper board.

Game of Life

Implement Conway's Game of Life.

Perfect Numbers

Determine if a number is perfect, abundant, or deficient based on Nicomachus' (60 - 120 CE) classification scheme for positive integers.

Phone Number

Clean up user-entered phone numbers so that they can be sent SMS messages.

Secret Handshake

Given a decimal number, convert it to the appropriate sequence of events for a secret handshake.

Pascal's Triangle

Compute Pascal's triangle up to a given number of rows.

Binary Search Tree

Insert and search for numbers in a binary tree.

Queen Attack

Given the position of two queens on a chess board, indicate whether or not they are positioned so that they can attack each other.

State of Tic-Tac-Toe

Determine the game state of a match of Tic-Tac-Toe.

Word Count

Given a phrase, count the occurrences of each word in that phrase.

Word Search

Create a program to solve a word search puzzle.

Wordy

Parse and evaluate simple math word problems returning the answer as an integer.

Hamming

Calculate the Hamming difference between two DNA strands.

Robot Simulator

Write a robot simulator.

Twelve Days

Output the lyrics to 'The Twelve Days of Christmas'.

Saddle Points

Detect saddle points in a matrix.

Food Chain

Generate the lyrics of the song 'I Know an Old Lady Who Swallowed a Fly'.

OCR Numbers

Given a 3 x 4 grid of pipes, underscores, and spaces, determine which number is represented, or whether it is garbled.

Change

Correctly determine change to be given using the least number of coins.

Knapsack

Given a knapsack that can only carry a certain weight, determine which items to put in the knapsack in order to maximize their combined value.

Satellite

Rebuild binary trees from pre-order and in-order traversals.

Go Counting

Count the scored points on a Go board.

Resistor Color Duo

Convert color codes, as used on resistors, to a numeric value.

D&D Character

Randomly generate Dungeons & Dragons characters.

Resistor Color Trio

Convert color codes, as used on resistors, to a human-readable label.

Run-Length Encoding

Implement run-length encoding and decoding.

House

Output the nursery rhyme 'This is the House that Jack Built'.

Proverb

For want of a horseshoe nail, a kingdom was lost, or so the saying goes. Output the full text of this proverbial rhyme.

Simple Linked List

Write a simple linked list implementation that uses Elements and a List.

Custom Set

Create a custom set type.

Bowling

Score a bowling game.

ISBN Verifier

Check if a given string is a valid ISBN-10 number.

Protein Translation

Translate RNA sequences into proteins.

Yacht

Score a single throw of dice in the game Yacht.

Pythagorean Triplet

There exists exactly one Pythagorean triplet for which a + b + c = 1000. Find the product a * b * c.

Rotational Cipher

Create an implementation of the rotational cipher, also sometimes called the Caesar cipher.

Spiral Matrix

Given the size, return a square matrix of numbers in spiral order.

Affine Cipher

Create an implementation of the Affine cipher, an ancient encryption algorithm from the Middle East.

Alphametics

Write a function to solve alphametics puzzles.

Beer Song

Produce the lyrics to that beloved classic, that field-trip favorite: 99 Bottles of Beer on the Wall.

List Ops

Implement basic list operations.

Matrix

Given a string representing a matrix of numbers, return the rows and columns of that matrix.

Binary Search

Implement a binary search algorithm.

Parallel Letter Frequency

Count the frequency of letters in texts using parallel computation.

Transpose

Take input text and output it transposed.

Poker

Pick the best hand(s) from a list of poker hands.

Lens Person

Use lenses to update nested records (specific to languages with immutable data).

Triangle

Determine if a triangle is equilateral, isosceles, or scalene.

Meetup

Calculate the date of meetups.

Sieve

Use the Sieve of Eratosthenes to find all the primes from 2 up to a given number.

Palindrome Products

Detect palindrome products in a given range.

Simple Cipher

Implement a simple shift cipher like Caesar and a more secure substitution cipher.

Connect

Compute the result for a game of Hex / Polygon.

Book Store

To try and encourage more sales of different books from a popular 5 book series, a bookshop has decided to offer discounts of multiple-book purchases.

Reparent a graph on a selected node.

Difference of Squares

Find the difference between the square of the sum and the sum of the squares of the first N natural numbers.

Raindrops

Convert a number to a string, the content of which depends on the number's factors.

Kindergarten Garden

Given a diagram, determine which plants each child in the kindergarten class is responsible for.

All Your Base

Convert a number, represented as a sequence of digits in one base, to any other base.

Allergies

Given a person's allergy score, determine whether or not they're allergic to a given item, and their full list of allergies.

Series

Given a string of digits, output all the contiguous substrings of length `n` in that string.

Bank Account

Simulate a bank account supporting opening/closing, withdraws, and deposits of money. Watch out for concurrent transactions!

Rail Fence Cipher

Implement encoding and decoding for the rail fence cipher.

Sublist

Write a function to determine if a list is a sublist of another list.

SGF Parsing

Parsing a Smart Game Format string.

Zipper

Creating a zipper for a binary tree.

Armstrong Numbers

Determine if a number is an Armstrong number.

Change the data format for scoring a game to more easily add other languages.

Scrabble Score

Given a word, compute the Scrabble score for that word.

Roman Numerals

Convert modern Arabic numbers into Roman numerals.

Atbash Cipher

Create an implementation of the atbash cipher, an ancient encryption system created in the Middle East.

Pig Latin

Implement a program that translates from English to Pig Latin.

Robot Name

Manage robot factory settings.

Given a number from 0 to 999,999,999,999, spell out that number in English.

Dominoes

Make a chain of dominoes.

Accumulate

Implement the `accumulate` operation, which, given a collection and an operation to perform on each element of the collection, returns a new collection containing the result of applying that operation to each element of the input collection.