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Exercism

Factor

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Get fluent in Factor by solving 160 exercises. And then level up with mentoring from our world-class team.

Syllabus

  • Hello World
    • Exercism's classic introductory exercise. Just say "Hello, World!".
  • Cargo Shuffle
    • Learn how Factor passes values on the data stack by re-stowing cargo with shuffle words.
  • Leah's Luscious Lasagna
    • Learn about stack effects in Factor by cooking delicious lasagna.
  • Annalyn's Infiltration
    • Learn about boolean expressions by implementing the quest logic for a new RPG.
  • Currency Conversion
    • Learn about numbers in Factor by solving Chandler's currency exchange conundrums.
  • Cars, Assemble!
    • Learn about conditionals in Factor by analyzing the production of an assembly line.
  • Log Levels
    • Learn about strings in Factor by parsing log lines.
  • Character Study
    • Learn about Unicode-aware character handling by helping a Forth Alien with her alphabets project.
  • High School Sweetheart
    • Learn about quotations in Factor by helping high school sweethearts profess their love on social media via unicode art.
  • Joiner's Journey
    • Replace stack shuffling with combinators by helping a furniture workshop plan its cuts.
  • Secrets
    • Learn about bitwise operations in Factor by writing a program to decrypt a message.
  • Bunting Bonanza
    • Help a party robot string up rows of bunting for the bonanza and learn how to build a string from index-driven decisions.
  • Backyard Birdwatcher
    • Learn about sequences in Factor by tracking the birds visiting your garden.
  • Mosaic Making
    • Help build a community mosaic and learn the small toolkit of array constructors and lookups.
  • Boutique Bookkeeping
    • Learn about higher-order sequence words by stocking your fashion boutique.
  • Mosaic Mischief
    • Help log Magpie Marg's mischief by mutating arrays and vectors in place.
  • Librarian's Ledger
    • Tally a librarian's ledger with reduce and the cumulative family of reductions.
  • Coordinate Choreography
    • Learn about curry, compose, and fry quotations by building reusable 2D coordinate transformations.
  • Poetry Club
    • Learn about disjoint sets in Factor by tracking the writing circles of a poetry club.
  • Passphrase Patrol
    • Learn about regular expressions in Factor by validating badge codes and tidying an access log.
  • Ledger Lookout
    • Learn advanced regular expressions in Factor — grouping, lookaround, and options — by parsing a ledger.
  • Lap Leaderboard
    • Walk a list of finishers with each-index, map-index, and times to build the club race's leaderboard.
  • Belgian Boxcars
    • Run the Antwerp marshalling yard by chunking, sliding, and splitting freight-car sequences with group/clump/split-when/monotonic-split.
  • Role Playing Game
    • Learn about tuples in Factor by building the mechanics for a role-playing game.
  • Factory Failsafe
    • Learn about errors in Factor by monitoring machines in a newspaper factory.
  • Bosun's Briefing
    • Help the bosun assemble a watch briefing by factoring small named lines into a helpers vocabulary and composing them in the main file.
  • Purser's Pantry
    • Learn about hashtables in Factor by managing the warehouse inventory.
  • Tellers' Triage
    • Learn about heaps in Factor by serving a bank's customers in priority order.
  • RPN Calculator
    • Learn about quotations and call by building a small RPN calculator.
  • Backyard Birdcount
    • Learn about recursion in Factor by counting visits from your garden's birds.
  • Valentine's Day
    • Learn about case and symbols by rating Valentine's Day plans.
  • Lasagna Luminary
    • Learn about locals in Factor by mastering the lasagna recipe.
  • Mixed Juices
    • Help Li Mei manage her juice bar and learn the while combinator.
  • Garden Gathering
    • Learn about dynamic variables in Factor by managing a community garden's plot registrations.
  • Boardwalk Games
    • Learn about randomness in Factor by running the games of chance at a seaside boardwalk arcade.
  • Ferry Schedule
    • Learn about the calendar vocabulary in Factor by keeping the timetable for an island ferry.
  • Bering Bearings
    • Plot bearings reported in three different forms onto a single chart with generic words and per-class methods.
  • Lighthouse Logbook
    • Track unique vessel sightings and signal-relay reachability with mutable hash-sets and a textbook BFS.
  • Pirates' Path
    • Use a as the BFS frontier through a chart of hidden coves, then cache an expensive gold-lookup with MEMO:.
  • Quayside Crew
    • Run the quayside night shift with cooperative threads, parallel-map, promises, and a lock-protected tonnage tally.
  • Signaler's Satchel
    • Quote values, slice signal flags, and project pairs and triples with the multi-input cleave family.
  • Dragons' Descendants
    • Build a hierarchy of dragon tuples using TUPLE: < parent, then exercise slot and accessor inheritance with one word that ages any descendant.
  • Signal Stencils
    • Build four MACRO: declarations whose bodies run at compile time and return quotations specialised on each call site's literal arguments.
  • Boatswain's Bilge
    • Acquire and release bilge gear with dispose, with-disposal, with-destructors, &dispose, and |dispose, then define a fresh disposable from scratch.
  • Channel Chatter
    • Read, write, and scope bundled streams from the io vocabulary, using the same destructor combinators that release any disposable.
  • Telegrapher's Tape
    • Build a custom input stream that filters noise out of a wireless line — your first taste of Factor's stream protocol and disposable cleanup.
  • Mixtape Maker
    • Learn about combinatorics in Factor by choosing and ordering the songs on a mixtape.
  • Vltava Weather Watch
    • Read, write, and append to files on disk with the whole-file and scoped words of the io.files vocabulary.
  • Collatz Conjecture
    • Calculate the number of steps to reach 1 using the Collatz conjecture.
  • Darts
    • Calculate the points scored in a single toss of a Darts game.
  • Difference of Squares
    • Find the difference between the square of the sum and the sum of the squares of the first N natural numbers.
  • Eliud's Eggs
    • Help Eliud count the number of eggs in her chicken coop by counting the number of 1 bits in a binary representation.
  • ETL
    • Change the data format for scoring a game to more easily add other languages.
  • Grains
    • Calculate the number of grains of wheat on a chessboard given that the number on each square doubles.
  • High Scores
    • Manage a player's High Score list.
  • Micro Blog
    • Given an input string, truncate it to 5 characters.
  • Nucleotide Count
    • Given a DNA string, compute how many times each nucleotide occurs in the string.
  • Pangram
    • Determine whether a phrase uses every letter in the Latin alphabet.
  • Resistor Color
    • Convert a resistor band's color to its numeric representation.
  • Resistor Color Duo
    • Convert color codes, as used on resistors, to a numeric value.
  • Resistor Color Trio
    • Convert color codes, as used on resistors, to a human-readable label.
  • RNA Transcription
    • Given a DNA strand, return its RNA complement.
  • Triangle
    • Determine if a triangle is equilateral, isosceles, or scalene.
  • Two Fer
    • Create a sentence of the form "One for X, one for me.".
  • Acronym
    • Convert a long phrase to its acronym.
  • Atbash Cipher
    • Create an implementation of the Atbash cipher, an ancient encryption system created in the Middle East.
  • Binary Search
    • Implement a binary search algorithm.
  • Bob
    • Bob is a lackadaisical teenager. In conversation, his responses are very limited.
  • Hamming
    • Calculate the Hamming distance between two DNA strands.
  • ISBN Verifier
    • Check if a given string is a valid ISBN-10 number.
  • Isogram
    • Determine whether a phrase is an isogram, a word with no repeated letters.
  • Leap
    • Determine whether a given year is a leap year.
  • Line Up
    • Help lining up customers at YaÊ»qÅ«b's Deli.
  • Phone Number
    • Clean up user-entered phone numbers so that they can be sent SMS messages.
  • Prime Factors
    • Compute the prime factors of a given natural number.
  • 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.
  • Raindrops
    • Convert a number into its corresponding raindrop sounds - Pling, Plang and Plong.
  • Reverse String
    • Reverse a given string.
  • Rotational Cipher
    • Create an implementation of the rotational cipher, also sometimes called the Caesar cipher.
  • Scrabble Score
    • Given a word, compute the Scrabble score for that word.
  • Series
    • Given a string of digits, output all the contiguous substrings of length `n` in that string.
  • Sublist
    • Determine if a list is a sublist of another list.
  • Sum of Multiples
    • Given a number, find the sum of all the multiples of particular numbers up to but not including that number.
  • Allergies
    • Given a person's allergy score, determine whether or not they're allergic to a given item, and their full list of allergies.
  • Armstrong Numbers
    • Determine if a number is an Armstrong number.
  • Bottle Song
    • Produce the lyrics to the popular children's repetitive song: Ten Green Bottles.
  • Complex Numbers
    • Implement complex numbers.
  • D&D Character
    • Randomly generate Dungeons & Dragons characters.
  • 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.
  • Grade School
    • Given students' names along with the grade that they are in, create a roster for the school.
  • House
    • Output the nursery rhyme 'This is the House that Jack Built'.
  • Kindergarten Garden
    • Given a diagram, determine which plants each child in the kindergarten class is responsible for.
  • Largest Series Product
    • Given a string of digits, calculate the largest product for a contiguous substring of digits of length n.
  • Luhn
    • Given a number determine whether or not it is valid per the Luhn formula.
  • Matrix
    • Given a string representing a matrix of numbers, return the rows and columns of that matrix.
  • Meetup
    • Calculate the date of meetups.
  • Pascal's Triangle
    • Compute Pascal's triangle up to a given number of rows.
  • Protein Translation
    • Translate RNA sequences into proteins.
  • Proverb
    • For want of a horseshoe nail, a kingdom was lost, or so the saying goes. Output the full text of this proverbial rhyme.
  • Rational Numbers
    • Implement rational numbers.
  • Robot Simulator
    • Write a robot simulator.
  • Roman Numerals
    • Convert modern Arabic numbers into Roman numerals.
  • Saddle Points
    • Detect saddle points in a matrix.
  • Secret Handshake
    • Given a decimal number, convert it to the appropriate sequence of events for a secret handshake.
  • Sieve
    • Use the Sieve of Eratosthenes to find all the primes from 2 up to a given number.
  • Space Age
    • Given an age in seconds, calculate how old someone is in terms of a given planet's solar years.
  • Twelve Days
    • Output the lyrics to 'The Twelve Days of Christmas'.
  • Word Count
    • Given a phrase, count the occurrences of each word in that phrase.
  • Affine Cipher
    • Create an implementation of the Affine cipher, an ancient encryption algorithm from the Middle East.
  • Anagram
    • Find the words that use the same letters as another word.
  • Circular Buffer
    • A data structure that uses a single, fixed-size buffer as if it were connected end-to-end.
  • Clock
    • Implement a clock that handles times without dates.
  • Crypto Square
    • Implement the classic method for composing secret messages called a square code.
  • Gigasecond
    • Given a moment, determine the moment that would be after a gigasecond has passed.
  • Killer Sudoku Helper
    • Write a tool that makes it easier to solve Killer Sudokus
  • Knapsack
    • Given a knapsack that can only carry a certain weight, determine which items to put in the knapsack in order to maximize their combined value.
  • List Ops
    • Implement basic list operations.
  • Matching Brackets
    • Make sure the brackets and braces all match.
  • Pig Latin
    • Implement a program that translates from English to Pig Latin.
  • Relative Distance
    • Given a family tree, calculate the degree of separation.
  • Robot Name
    • Manage robot factory settings.
  • Run-Length Encoding
    • Implement run-length encoding and decoding.
  • Save the Cow
    • Implement a word-guessing game.
  • Spiral Matrix
    • Given the size, return a square matrix of numbers in spiral order.
  • Split-Second Stopwatch
    • Keep track of time through a digital stopwatch.
  • Square Root
    • Given a natural radicand, return its square root.
  • State of Tic-Tac-Toe
    • Determine the game state of a match of Tic-Tac-Toe.
  • Tournament
    • Tally the results of a small football competition.
  • Variable Length Quantity
    • Implement variable length quantity encoding and decoding.
  • Yacht
    • Score a single throw of dice in the game Yacht.
  • All Your Base
    • Convert a number, represented as a sequence of digits in one base, to any other base.
  • Binary Search Tree
    • Insert and search for numbers in a binary tree.
  • Change
    • Correctly determine change to be given using the least number of coins.
  • Conway's Game of Life
    • Implement Conway's Game of Life.
  • Flower Field
    • Mark all the flowers in a garden.
  • Food Chain
    • Generate the lyrics of the song 'I Know an Old Lady Who Swallowed a Fly'.
  • Intergalactic Transmission
    • Add parity bits to a message for transmission
  • OCR Numbers
    • Given a 3 x 4 grid of pipes, underscores, and spaces, determine which number is represented, or whether it is garbled.
  • Parallel Letter Frequency
    • Count the frequency of letters in texts using parallel computation.
  • Piecing It Together
    • Fill in missing jigsaw puzzle details from partial data
  • Rail Fence Cipher
    • Implement encoding and decoding for the rail fence cipher.
  • Say
    • Given a number from 0 to 999,999,999,999, spell out that number in English.
  • Two Bucket
    • Given two buckets of different size, demonstrate how to measure an exact number of liters.
  • Word Search
    • Create a program to solve a word search puzzle.
  • 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.
  • Custom Set
    • Create a custom set type.
  • Dominoes
    • Make a chain of dominoes.
  • Grep
    • Search a file for lines matching a regular expression pattern.
  • Nth Prime
    • Given a number n, determine what the nth prime is.
  • PaaS I/O
    • Report network IO statistics.
  • Perfect Numbers
    • Determine if a number is perfect, abundant, or deficient based on Nicomachus' (60 - 120 CE) classification scheme for positive integers.
  • Rectangles
    • Count the rectangles in an ASCII diagram.
  • Satellite
    • Rebuild binary trees from pre-order and in-order traversals.
  • Simple Linked List
    • Write a simple linked list implementation that uses Elements and a List.
  • Wordy
    • Parse and evaluate simple math word problems returning the answer as an integer.
  • Zebra Puzzle
    • Solve the zebra puzzle.
  • Palindrome Products
    • Detect palindrome products in a given range.
  • Pythagorean Triplet
    • Given an integer N, find all Pythagorean triplets for which a + b + c = N.
  • Bowling
    • Score a bowling game.
  • Connect
    • Compute the result for a game of Hex / Polygon.
  • Alphametics
    • Given an alphametics puzzle, find the correct solution.

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