# Lua

One of the easiest ways to add new exercises to the Lua 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 Lua.

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 Lua track repository on GitHub.

### Two Fer

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

### Wordy

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

### Rotational Cipher

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

### Palindrome Products

Detect palindrome products in a given range.

Detect saddle points in a matrix.

### 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.

### Simple Cipher

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

### Complex Numbers

Implement complex numbers.

### Armstrong Numbers

Determine if a number is an Armstrong number

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.

### Twelve Days

Output the lyrics to 'The Twelve Days of Christmas'

### 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

### 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.

### 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.

### Scale Generator

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

### 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