# Elm

One of the easiest ways to add new exercises to the Elm track is to translate them from other language tracks on Exercism. This page lists all of the problem specifications in the common pool of exercises which have not yet been implemented in Elm.

The icon links to the language-independent description of the problem.

The icon links to the canonical test data.

We also link to all the implementations of each exercise in other languages, which you can use for inspiration.

Once you've picked an exercise, follow the instructions in this guide and submit your pull request to the Elm track repository on GitHub.

### Beer Song

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

### Robot Name

Manage robot factory settings.

### Sieve

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

### Clock

Implement a clock that handles times without dates.

### Meetup

Calculate the date of meetups.

### Nth Prime

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

### Bracket Push

Make sure the brackets and braces all match.

### Crypto Square

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

### Perfect Numbers

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

### Prime Factors

Compute the prime factors of a given natural number.

### Two Fer

Create a sentence of the form "One for X, one for me."

### Pig Latin

Implement a program that translates from English to Pig Latin

### 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.

### Secret Handshake

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

### Minesweeper

Add the numbers to a minesweeper board

### Diamond

Given a letter, print a diamond starting with 'A' with the supplied letter at the widest point.

### Flatten Array

Take a nested list and return a single list with all values except nil/null

### Wordy

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

### Binary Search Tree

Insert and search for numbers in a binary tree.

### Custom Set

Create a custom set type.

### Rotational Cipher

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

### Bowling

Score a bowling game

### Isbn Verifier

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

### Palindrome Products

Detect palindrome products in a given range.

Detect saddle points in a matrix.

### 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

### Circular Buffer

A data structure that uses a single, fixed-size buffer as if it were connected end-to-end.

### Kindergarten Garden

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

### Protein Translation

Translate RNA sequences into proteins.

### Pythagorean Triplet

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

### Simple Cipher

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

### Bank Account

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

### Complex Numbers

Implement complex numbers.

### Food Chain

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

### Matrix

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

### Armstrong Numbers

Determine if a number is an Armstrong number

### React

Implement a basic reactive system.

### Reverse String

Reverse a string

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

### Spiral Matrix

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

### Alphametics

Write a function to solve alphametics puzzles.

### Connect

Compute the result for a game of Hex / Polygon

### Dominoes

Make a chain of dominoes.

### Forth

Implement an evaluator for a very simple subset of Forth

### House

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

### Poker

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

### Proverb

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

### Rail Fence Cipher

Implement encoding and decoding for the rail fence cipher.

### Rectangles

Count the rectangles in an ASCII diagram.

### Tournament

Tally the results of a small football competition.

### Variable Length Quantity

Implement variable length quantity encoding and decoding.

### 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.

### Diffie Hellman

Diffie-Hellman key exchange.

### Parallel Letter Frequency

Count the frequency of letters in texts using parallel computation.

### Two Bucket

Given two buckets of different size, demonstrate how to measure an exact number of liters.

### Zipper

Creating a zipper for a binary tree.

### Markdown

Refactor a Markdown parser

### Grep

Search a file for lines matching a regular expression pattern. Return the line number and contents of each matching line.

### Pov

Reparent a graph on a selected node

### Scale Generator

Generate musical scales, given a starting note and a set of intervals.

### Word Search

Create a program to solve a word search puzzle.

### Error Handling

Implement various kinds of error handling and resource management

### Rational Numbers

Implement rational numbers.

### Zebra Puzzle

Solve the zebra puzzle.

### Go Counting

Count the scored points on a Go board.

### Sgf Parsing

Parsing a Smart Game Format string.

### Dot Dsl

Write a Domain Specific Language similar to the Graphviz dot language

### Tree Building

Refactor a tree building algorithm.

### Yacht

Score a single throw of dice in the game Yacht

### Hangman

Implement the logic of the hangman game using functional reactive programming.

### Ledger

Refactor a ledger printer.

### Lens Person

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

### Paasio

Report network IO statistics