### Add new Factor exercises

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

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 Factor track repository on GitHub.

#### Exercises

#### About

#### Examples

### Difference Of Squares

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

### Atbash Cipher

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

### Grains

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

### Allergies

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

### Beer Song

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

### Space Age

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

### Largest Series Product

Given a string of digits, calculate the largest product for a contiguous substring of digits of length n.

### Sum Of Multiples

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

### Grade School

Given students' names along with the grade that they are in, create a roster for the school

### Perfect Numbers

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

### 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.

### 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.

### Diamond

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

### Ocr Numbers

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

### Rotational Cipher

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

### 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.

### Pythagorean Triplet

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

### 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.

### Bank Account

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

### 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.

### Two Bucket

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

### Proverb

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

### Grep

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