Scheme is a statically scoped and properly tail-recursive dialect of the Lisp programming language invented by Guy Lewis Steele Jr. and Gerald Jay Sussman. It was designed to have an exceptionally clear and simple semantics and few different ways to form expressions. A wide variety of programming paradigms, including functional, imperative, and message passing styles, find convenient expression in Scheme.

Syllabus

Hello World

Exercism's classic introductory exercise. Just say "Hello, World!".

Leap

Determine whether a given year is a leap year.

RNA Transcription

Given a DNA strand, return its RNA Complement Transcription.

Hamming

Calculate the Hamming distance between two DNA strands.

Grains

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

Anagram

Given a word and a list of possible anagrams, select the correct sublist.

Difference of Squares

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

Pascal's Triangle

Compute Pascal's triangle up to a given number of rows.

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.

Binary Search

Implement a binary search algorithm.

Two Fer

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

Transpose

Take input text and output it transposed.

Forth

Implement an evaluator for a very simple subset of Forth.

Phone Number

Clean up user-entered phone numbers so that they can be sent SMS messages.

Raindrops

Convert a number into its corresponding raindrop sounds - Pling, Plang and Plong.

Matching Brackets

Make sure the brackets and braces all match.

Perfect Numbers

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

Nucleotide Count

Given a DNA string, compute how many times each nucleotide occurs in the string.

Scrabble Score

Given a word, compute the Scrabble score for that word.

Word Count

Given a phrase, count the occurrences of each word in that phrase.

Pangram

Determine if a sentence is a pangram.

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.

Atbash Cipher

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

Change

Correctly determine change to be given using the least number of coins.

Collatz Conjecture

Calculate the number of steps to reach 1 using the Collatz conjecture.

Rotational Cipher

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

Prime Factors

Compute the prime factors of a given natural number.

Bob is a lackadaisical teenager. In conversation, his responses are very limited.

Affine Cipher

Create an implementation of the Affine cipher, an ancient encryption algorithm from the Middle East.

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.

Armstrong Numbers

Determine if a number is an Armstrong number.

Acronym

Convert a long phrase to its acronym.

Octal

Convert a octal number, represented as a string (e.g. '1735263'), to its decimal equivalent using first principles (i.e. no, you may not use built-in or external libraries to accomplish the conversion).