# Erlang

When you're logged in, you can say `exercism fetch erlang` to get the next available exercise on the track.

Every time you submit a solution to an exercise, you will get the next in line the next time you fetch.

If you want to try a specific exercise, you can always fetch it directly (commands are listed below).

The exercises are ordered roughly in order of difficulty.

### Available Exercises

• Hello World The classical introductory exercise. Just say "Hello, World!"
• Leap Given a year, report if it is a leap year.
• 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.
• Collatz Conjecture Calculate the number of steps to reach 1 using the Collatz conjecture
• Raindrops Convert a number to a string, the contents of which depend on the number's factors.
• Rna Transcription Given a DNA strand, return its RNA Complement Transcription.
• Bob Bob is a lackadaisical teenager. In conversation, his responses are very limited.
• 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.
• Hamming Calculate the Hamming difference between two DNA strands.
• Space Age Given an age in seconds, calculate how old someone is in terms of a given planet's solar years.
• Grains Calculate the number of grains of wheat on a chessboard given that the number on each square doubles.
• Isogram Determine if a word or phrase is an isogram.
• Pangram Determine if a sentence is a pangram.
• Nucleotide Count Given a DNA string, compute how many times each nucleotide occurs in the string.
• Difference Of Squares Find the difference between the square of the sum and the sum of the squares of the first N natural numbers.
• Triangle Determine if a triangle is equilateral, isosceles, or scalene.
• Sum Of Multiples Given a number, find the sum of all the multiples of particular numbers up to but not including that number.
• Anagram Given a word and a list of possible anagrams, select the correct sublist.
• Atbash Cipher Create an implementation of the atbash cipher, an ancient encryption system created in the Middle East.
• Phone Number Clean up user-entered phone numbers so that they can be sent SMS messages.
• Gigasecond Calculate the moment when someone has lived for 10^9 seconds.
• Scrabble Score Given a word, compute the scrabble score for that word.
• Two Fer Create a sentence of the form "One for X, one for me."
• Robot Simulator Write a robot simulator.
• Grade School Given students' names along with the grade that they are in, create a roster for the school
• Word Count Given a phrase, count the occurrences of each word in that phrase.
• Clock Implement a clock that handles times without dates.
• Allergies Given a person's allergy score, determine whether or not they're allergic to a given item, and their full list of allergies.
• All Your Base Convert a number, represented as a sequence of digits in one base, to any other base.
• Series Given a string of digits, output all the contiguous substrings of length `n` in that string.
• Parallel Letter Frequency Count the frequency of letters in texts using parallel computation.
• Roman Numerals Write a function to convert from normal numbers to Roman Numerals.
• Sieve Use the Sieve of Eratosthenes to find all the primes from 2 up to a given number.
• Largest Series Product Given a string of digits, calculate the largest product for a contiguous substring of digits of length n.
• Complex Numbers Implement complex numbers.
• Rotational Cipher Create an implementation of the rotational cipher, also sometimes called the Caesar cipher.
• Etl We are going to do the `Transform` step of an Extract-Transform-Load.
• Bank Account Simulate a bank account supporting opening/closing, withdraws, and deposits of money. Watch out for concurrent transactions!
• Luhn Given a number determine whether or not it is valid per the Luhn formula.
• Custom Set Create a custom set type.
• Meetup Calculate the date of meetups.
• Circular Buffer A data structure that uses a single, fixed-size buffer as if it were connected end-to-end.
• Beer Song Produce the lyrics to that beloved classic, that field-trip favorite: 99 Bottles of Beer on the Wall.
• Zipper Creating a zipper for a binary tree.
• Spiral Matrix Given the size, return a square matrix of numbers in spiral order.