Sign up
Log in
Home
Language tracks
Emacs Lisp track
Exercises
Exercises on the Emacs Lisp track
Join the Emacs Lisp Track
28 exercises to help you master Emacs Lisp
easy
Hello World
The classical introductory exercise. Just say "Hello, World!"
strings
easy
Two Fer
Create a sentence of the form "One for X, one for me."
strings
easy
Bob
Bob is a lackadaisical teenager. In conversation, his responses are very limited.
control flow conditionals
parsing
strings
easy
Difference Of Squares
Find the difference between the square of the sum and the sum of the squares of the first N natural numbers.
math
control flow loops
floating point numbers
integers
easy
Gigasecond
Given a moment, determine the moment that would be after a gigasecond has passed.
date
integers
time
transforming
variables
easy
Hamming
Calculate the Hamming difference between two DNA strands.
control flow conditionals
control flow loops
equality
filtering
strings
easy
Pangram
Determine if a sentence is a pangram.
strings
control flow loops
easy
Anagram
Given a word and a list of possible anagrams, select the correct sublist.
equality
filtering
strings
easy
Binary
Convert a binary number, represented as a string (e.g. '101010'), to its decimal equivalent using first principles
math
bitwise operations
control flow conditionals
integers
easy
Leap
Given a year, report if it is a leap year.
control flow conditionals
equality
integers
logic
easy
Allergies
Given a person's allergy score, determine whether or not they're allergic to a given item, and their full list of allergies.
bitwise operations
control flow conditionals
integers
text formatting
easy
Robot Name
Manage robot factory settings.
randomness
strings
variables
easy
RNA Transcription
Given a DNA strand, return its RNA Complement Transcription.
control flow conditionals
strings
transforming
easy
Atbash Cipher
Create an implementation of the atbash cipher, an ancient encryption system created in the Middle East.
control flow conditionals
control flow loops
sequences
transforming
easy
Raindrops
Convert a number to a string, the contents of which depend on the number's factors.
control flow conditionals
filtering
integers
easy
Roman Numerals
Write a function to convert from normal numbers to Roman Numerals.
control flow conditionals
control flow loops
integers
strings
text formatting
easy
Perfect Numbers
Determine if a number is perfect, abundant, or deficient based on Nicomachus' (60 - 120 CE) classification scheme for natural numbers.
math
number theory
easy
ETL
We are going to do the `Transform` step of an Extract-Transform-Load.
control flow loops
maps
transforming
easy
Word Count
Given a phrase, count the occurrences of each word in that phrase.
control flow conditionals
control flow loops
filtering
strings
easy
Nucleotide Count
Given a DNA string, compute how many times each nucleotide occurs in the string.
control flow loops
maps
sorting
strings
easy
Phone Number
Clean up user-entered phone numbers so that they can be sent SMS messages.
interfaces
parsing
strings
easy
Grains
Calculate the number of grains of wheat on a chessboard given that the number on each square doubles.
integers
variables
easy
Acronym
Convert a long phrase to its acronym
strings
transforming
easy
Armstrong Numbers
Determine if a number is an Armstrong number
math
easy
Run Length Encoding
Implement run-length encoding and decoding.
misc
easy
Trinary
Convert a trinary number, represented as a string (e.g. '102012'), to its decimal equivalent using first principles.
math
easy
Crypto Square
Implement the classic method for composing secret messages called a square code.
strings
transforming
cryptograpy
easy
Luhn
Given a number determine whether or not it is valid per the Luhn formula.
strings
list operations
checksums