Haskell

Haskell is a standardized purely functional programming language with non-strict semantics, named after the logician Haskell Curry. It is one of the more popular functional languages, and the lazy functional language on which the most research is being performed.

Although Haskell has a comparatively small user community, its strengths have been well applied to a few projects:

• Pandoc - Universal document converter.
• [Shellcheck]](https://www.shellcheck.net/) - Static analysis tool for shell scripts.
• Pugs by Audrey Tang - Implementation for the Perl 6 language with an interpreter and compilers that proved useful already after just a few months of its writing.
• Darcs - Revision control system with several innovative features.

Tasks

• 100 doors
• 15 Puzzle Game
• 2048
• 24 game
• 24 game/Solve
• 4-rings or 4-squares puzzle
• 9 billion names of God the integer
• A+B
• ABC Problem
• AKS test for primes
• AVL tree
• Abbreviations, automatic
• Abbreviations, easy
• Abbreviations, simple
• Abelian sandpile model
• Abstract type
• Abundant odd numbers
• Abundant, deficient and perfect number classifications
• Accumulator factory
• Ackermann function
• Active Directory/Connect
• Active Directory/Search for a user
• Active object
• Align columns
• Aliquot sequence classifications
• Almost prime
• Amicable pairs
• Anagrams/Deranged anagrams
• Angle difference between two bearings
• Animate a pendulum
• Animation
• Anonymous recursion
• Anti-primes
• Append a record to the end of a text file
• Apply a callback to an array
• Arbitrary-precision integers (included)
• Archimedean spiral
• Arithmetic evaluation
• Arithmetic-geometric mean
• Arithmetic-geometric mean/Calculate Pi
• Arithmetic/Complex
• Arithmetic/Integer
• Arithmetic/Rational
• Array concatenation
• Array length
• Arrays
• Assertions
• Associative array/Creation
• Associative array/Iteration
• Atomic updates
• Attractive numbers
• Average loop length
• Averages/Arithmetic mean
• Averages/Mean angle
• Averages/Mean time of day
• Averages/Median
• Averages/Mode
• Averages/Pythagorean means
• Averages/Root mean square
• Averages/Simple moving average
• Babbage problem
• Bacon cipher
• Balanced brackets
• Balanced ternary
• Barnsley fern
• Base58Check encoding
• Base64 decode data
• Base64 encode data
• Benford's law
• Bernoulli numbers
• Best shuffle
• Binary digits
• Binary search
• Binary strings
• Bitcoin/address validation
• Bitcoin/public point to address
• Bitmap
• Bitmap/Bézier curves/Quadratic
• Bitmap/Flood fill
• Bitmap/Histogram
• Bitmap/Midpoint circle algorithm
• Bitmap/Read a PPM file
• Bitmap/Write a PPM file
• Bitwise IO
• Bitwise operations
• Boolean values
• Box the compass
• Brace expansion
• Brazilian numbers
• Bresenham's Line Algorithm
• Brownian tree
• Bulls and cows
• Bulls and cows/Player
• Burrows–Wheeler transform
• CRC-32
• CSV data manipulation
• CSV to HTML translation
• CUSIP
• Caesar cipher
• Calculating the value of e
• Calendar
• Call a foreign-language function
• Call a function
• Call a function in a shared library
• Carmichael 3 strong pseudoprimes
• Cartesian product of two or more lists
• Case-sensitivity of identifiers
• Casting out nines
• Catalan numbers
• Catalan numbers/Pascal's triangle
• Catamorphism
• Catmull–Clark subdivision surface
• Chaocipher
• Chaos game
• Character codes
• Chat server
• Check Machin-like formulas
• Check input device is a terminal
• Check output device is a terminal
• Check that file exists
• Checkpoint synchronization
• Cheryl's Birthday
• Chinese remainder theorem
• Cholesky decomposition
• Church Numerals
• Circles of given radius through two points
• Classes
• Closest-pair problem
• Closures/Value capture
• Collections
• Color quantization
• Colour bars/Display
• Combinations
• Combinations and permutations
• Combinations with repetitions
• Comma quibbling
• Command-line arguments
• Comments
• Compare a list of strings
• Compile-time calculation
• Compound data type
• Concurrent computing
• Conditional structures
• Conjugate transpose
• Constrained genericity
• Constrained random points on a circle
• Continued fraction
• Continued fraction/Arithmetic/Construct from rational number
• Convert decimal number to rational
• Convert seconds to compound duration
• Convex hull
• Copy a string
• Count in factors
• Count in octal
• Count occurrences of a substring
• Count the coins
• Cramer's rule
• Create a file
• Create a file on magnetic tape
• Create a two-dimensional array at runtime
• Create an HTML table
• Cumulative standard deviation
• Currency
• Currying
• Cut a rectangle
• Date format
• Date manipulation
• Day of the week
• Decimal floating point number to binary
• Deconvolution/1D
• Define a primitive data type
• Delete a file
• Deming's Funnel
• Department Numbers
• Detect division by zero
• Determinant and permanent
• Determine if a string is numeric
• Determine if only one instance is running
• Digital root
• Digital root/Multiplicative digital root
• Dijkstra's algorithm
• Dinesman's multiple-dwelling problem
• Dining philosophers
• Discordian date
• Distributed programming
• Documentation
• Dot product
• Doubly-linked list/Definition
• Doubly-linked list/Element definition
• Doubly-linked list/Element insertion
• Doubly-linked list/Traversal
• Dragon curve
• Draw a clock
• Draw a cuboid
• Draw a rotating cube
• Draw a sphere
• Dutch national flag problem
• Dynamic variable names
• EKG sequence convergence
• Echo server
• Egyptian division
• Egyptian fractions
• Element-wise operations
• Elementary cellular automaton
• Elementary cellular automaton/Infinite length
• Elementary cellular automaton/Random Number Generator
• Elliptic curve arithmetic
• Emirp primes
• Empty directory
• Empty program
• Empty string
• Enforced immutability
• Entropy
• Entropy/Narcissist
• Enumerations
• Environment variables
• Equilibrium index
• Ethiopian multiplication
• Euler method
• Euler's identity
• Euler's sum of powers conjecture
• Evaluate binomial coefficients
• Even or odd
• Events
• Evolutionary algorithm
• Exceptions
• Exceptions/Catch an exception thrown in a nested call
• Execute Brainfuck
• Execute HQ9+
• Execute SNUSP
• Execute a Markov algorithm
• Execute a system command
• Exponentiation operator
• Exponentiation order
• Extend your language
• Extensible prime generator
• Extract file extension
• Extreme floating point values
• FASTA format
• FTP
• Factorial
• Factors of a Mersenne number
• Farey sequence
• Fast Fourier transform
• Faulhaber's formula
• Faulhaber's triangle
• Feigenbaum constant calculation
• Fibonacci n-step number sequences
• Fibonacci sequence
• Fibonacci word
• File input and output
• Filter
• Find common directory path
• Find duplicate files
• Find largest left truncatable prime in a given base
• Find limit of recursion
• Find palindromic numbers in both binary and ternary bases
• Find the intersection of a line with a plane
• Find the intersection of two lines
• Find the last Sunday of each month
• Find the missing permutation
• First class environments
• First-class functions
• First-class functions/Use numbers analogously
• Five weekends
• FizzBuzz
• Flatten a list
• Flipping bits game
• Flow-control structures
• Floyd's triangle
• Floyd-Warshall algorithm
• Forest fire
• Fork
• Formal power series
• Formatted numeric output
• Forward difference
• Four bit adder
• Fractal tree
• Fractran
• Free polyominoes enumeration
• Function composition
• Function definition
• Function prototype
• Functional coverage tree
• Fusc sequence
• GUI component interaction
• GUI/Maximum window dimensions
• Galton box animation
• Gamma function
• Gaussian elimination
• General FizzBuzz
• Generate Chess960 starting position
• Generate lower case ASCII alphabet
• Generator/Exponential
• Generic swap
• Get system command output
• Go Fish
• Gray code
• Grayscale image
• Greatest common divisor
• Greatest element of a list
• Greatest subsequential sum
• Greyscale bars/Display
• Guess the number
• Guess the number/With feedback
• Guess the number/With feedback (player)
• HTTP
• HTTPS
• HTTPS/Authenticated
• Hailstone sequence
• Hamming numbers
• Handle a signal
• Happy numbers
• Harshad or Niven series
• Hash from two arrays
• Hash join
• Haversine formula
• Hello world!
• Hello world/Graphical
• Hello world/Line printer
• Hello world/Newbie
• Hello world/Newline omission
• Hello world/Standard error
• Hello world/Text
• Hello world/Web server
• Here document
• Heronian triangles
• Hickerson series of almost integers
• Higher-order functions
• Hilbert curve
• History variables
• Hofstadter Figure-Figure sequences
• Hofstadter Q sequence
• Hofstadter-Conway $10,000 sequence
• Honeycombs
• Horizontal sundial calculations
• Horner's rule for polynomial evaluation
• Host introspection
• Hostname
• Hough transform
• Huffman coding
• I before E except after C
• IBAN
• Identity matrix
• Idiomatically determine all the lowercase and uppercase letters
• Image noise
• Imaginary base numbers
• Include a file
• Increment a numerical string
• Infinity
• Inheritance/Multiple
• Inheritance/Single
• Input loop
• Input/Output for Lines of Text
• Input/Output for Pairs of Numbers
• Integer comparison
• Integer overflow
• Integer roots
• Integer sequence
• Interactive programming
• Intersecting Number Wheels
• Introspection
• Inverted index
• Inverted syntax
• Iterated digits squaring
• JSON
• Jaro distance
• Jensen's Device
• Jewels and Stones
• JortSort
• Josephus problem
• Joystick position
• Jump anywhere
• K-d tree
• K-means++ clustering
• Kaprekar numbers
• Kernighans large earthquake problem
• Keyboard input/Flush the keyboard buffer
• Keyboard input/Keypress check
• Keyboard input/Obtain a Y or N response
• Knapsack problem/0-1
• Knapsack problem/Continuous
• Knapsack problem/Unbounded
• Knight's tour
• Knuth shuffle
• Knuth's algorithm S
• Koch curve
• Kolakoski sequence
• Kronecker product
• Kronecker product based fractals
• LU decomposition
• LZW compression
• Langton's ant
• Largest int from concatenated ints
• Largest number divisible by its digits
• Last Friday of each month
• Last letter-first letter
• Law of cosines - triples
• Leap year
• Least common multiple
• Left factorials
• Leonardo numbers
• Letter frequency
• Levenshtein distance
• Linear congruential generator
• Linux CPU utilization
• List comprehensions
• List rooted trees
• Literals/Floating point
• Literals/Integer
• Literals/String
• Logical operations
• Long multiplication
• Longest Common Substring
• Longest common prefix
• Longest common subsequence
• Longest increasing subsequence
• Longest string challenge
• Look-and-say sequence
• Loop over multiple arrays simultaneously
• Loops/Break
• Loops/Continue
• Loops/Do-while
• Loops/Downward for
• Loops/For
• Loops/For with a specified step
• Loops/Foreach
• Loops/Infinite
• Loops/N plus one half
• Loops/Nested
• Loops/While
• Lucas-Lehmer test
• Lucky and even lucky numbers
• Ludic numbers
• Luhn test of credit card numbers
• Lychrel numbers
• MAC Vendor Lookup
• MD4
• MD5
• MD5/Implementation
• Mad Libs
• Magic squares of doubly even order
• Magic squares of odd order
• Magic squares of singly even order
• Make directory path
• Man or boy test
• Mandelbrot set
• Map range
• Matrix chain multiplication
• Matrix multiplication
• Matrix transposition
• Matrix-exponentiation operator
• Maximum triangle path sum
• Mayan numerals
• Maze generation
• Maze solving
• McNuggets Problem
• Memory allocation
• Menu
• Metaprogramming
• Metered concurrency
• Mian-Chowla sequence
• Middle three digits
• Miller–Rabin primality test
• Mind boggling card trick
• Modular arithmetic
• Modular exponentiation
• Modular inverse
• Modulinos
• Monads/List monad
• Monads/Maybe monad
• Monads/Writer monad
• Monte Carlo methods
• Monty Hall problem
• Morse code
• Most frequent k chars distance
• Move-to-front algorithm
• Multifactorial
• Multiline shebang
• Multiple distinct objects
• Multiple regression
• Multiplication tables
• Multiplicative order
• Multisplit
• Munchausen numbers
• Munching squares
• Mutual recursion
• N'th
• N-queens problem
• Named parameters
• Names to numbers
• Naming conventions
• Narcissist
• Narcissistic decimal number
• Natural sorting
• Nautical bell
• Negative base numbers
• Nested function
• Non-continuous subsequences
• Non-decimal radices/Convert
• Non-decimal radices/Input
• Non-decimal radices/Output
• Nth root
• Null object
• Number names
• Number reversal game
• Numeric error propagation
• Numerical integration
• Numerical integration/Gauss-Legendre Quadrature
• Object serialization
• Odd word problem
• Old Russian measure of length
• Old lady swallowed a fly
• One of n lines in a file
• One-dimensional cellular automata
• OpenGL
• Operator precedence
• Optional parameters
• Order disjoint list items
• Order two numerical lists
• Ordered Partitions
• Ordered words
• Palindrome detection
• Pangram checker
• Paraffins
• Parallel calculations
• Parametric polymorphism
• Parametrized SQL statement
• Parse EBNF
• Parse an IP Address
• Parsing/RPN calculator algorithm
• Parsing/RPN to infix conversion
• Parsing/Shunting-yard algorithm
• Partial function application
• Partition an integer X into N primes
• Pascal matrix generation
• Pascal's triangle
• Pascal's triangle/Puzzle
• Password generator
• Pattern matching
• Penney's game
• Pentagram
• Percentage difference between images
• Percolation/Bond percolation
• Percolation/Site percolation
• Perfect numbers
• Perfect shuffle
• Perfect totient numbers
• Permutation test
• Permutations
• Permutations by swapping
• Permutations with repetitions
• Permutations/Derangements
• Permutations/Rank of a permutation
• Pernicious numbers
• Phrase reversals
• Pi
• Pick random element
• Pig the dice game
• Pig the dice game/Player
• Playfair cipher
• Playing cards
• Plot coordinate pairs
• Pointers and references
• Polymorphism
• Polynomial long division
• Polynomial regression
• Polyspiral
• Population count
• Power set
• Price fraction
• Primality by trial division
• Prime decomposition
• Primorial numbers
• Priority queue
• Probabilistic choice
• Problem of Apollonius
• Program name
• Program termination
• Proof
• Proper divisors
• Pythagoras tree
• Pythagorean quadruples
• Pythagorean triples
• QR decomposition
• Quaternion type
• Queue/Definition
• Queue/Usage
• Quickselect algorithm
• Quine
• RCRPG
• RIPEMD-160
• RPG Attributes Generator
• RSA code
• Random number generator (device)
• Random number generator (included)
• Random numbers
• Range consolidation
• Range expansion
• Range extraction
• Ranking methods
• Rate counter
• Ray-casting algorithm
• Read a configuration file
• Read a specific line from a file
• Read entire file
• Real constants and functions
• Recaman's sequence
• Reduced row echelon form
• Regular expressions
• Remove duplicate elements
• Remove lines from a file
• Rename a file
• Rep-string
• Repeat
• Repeat a string
• Resistor mesh
• Return multiple values
• Reverse a string
• Reverse the gender of a string
• Reverse words in a string
• Rock-paper-scissors
• Roman numerals/Decode
• Roman numerals/Encode
• Roots of a function
• Roots of a quadratic function
• Roots of unity
• Rosetta Code/Count examples
• Rosetta Code/Find bare lang tags
• Rosetta Code/Find unimplemented tasks
• Rot-13
• Run-length encoding
• Runge-Kutta method
• S-Expressions
• SEDOLs
• SHA-1
• SHA-256
• Sailors, coconuts and a monkey problem
• Same Fringe
• Sattolo cycle
• Scope modifiers
• Scope/Function names and labels
• Search a list
• Search a list of records
• Secure temporary file
• Self-describing numbers
• Self-referential sequence
• Semiprime
• Semordnilap
• Send email
• Sequence of non-squares
• Sequence of primes by trial division
• Sequence of primorial primes
• Set
• Set consolidation
• Set of real numbers
• Set puzzle
• Seven-sided dice from five-sided dice
• Shell one-liner
• Shoelace formula for polygonal area
• Short-circuit evaluation
• Show Ascii table
• Show the epoch
• Sierpinski carpet
• Sierpinski pentagon
• Sierpinski triangle
• Sierpinski triangle/Graphical
• Sieve of Eratosthenes
• Simple database
• Simple windowed application
• Singly-linked list/Element definition
• Singly-linked list/Element insertion
• Singly-linked list/Traversal
• Sleep
• Smith numbers
• Snake
• Sockets
• Sokoban
• Solve a Hidato puzzle
• Solve a Holy Knight's tour
• Solve the no connection puzzle
• Sort a list of object identifiers
• Sort an array of composite structures
• Sort an integer array
• Sort disjoint sublist
• Sort stability
• Sort three variables
• Sort using a custom comparator
• Sorting algorithms/Bead sort
• Sorting algorithms/Bogosort
• Sorting algorithms/Bubble sort
• Sorting algorithms/Cocktail sort
• Sorting algorithms/Comb sort
• Sorting algorithms/Counting sort
• Sorting algorithms/Gnome sort
• Sorting algorithms/Heapsort
• Sorting algorithms/Insertion sort
• Sorting algorithms/Merge sort
• Sorting algorithms/Pancake sort
• Sorting algorithms/Patience sort
• Sorting algorithms/Permutation sort
• Sorting algorithms/Quicksort
• Sorting algorithms/Radix sort
• Sorting algorithms/Selection sort
• Sorting algorithms/Shell sort
• Sorting algorithms/Sleep sort
• Sorting algorithms/Stooge sort
• Sorting algorithms/Strand sort
• Soundex
• Sparkline in unicode
• Special characters
• Special variables
• Speech synthesis
• Spinning rod animation/Text
• Spiral matrix
• Split a character string based on change of character
• Square but not cube
• Square-free integers
• Stable marriage problem
• Stack
• Stair-climbing puzzle
• State name puzzle
• Statistics/Basic
• Statistics/Normal distribution
• Stem-and-leaf plot
• Stern-Brocot sequence
• Straddling checkerboard
• String append
• String case
• String comparison
• String concatenation
• String interpolation (included)
• String length
• String matching
• String prepend
• Strip a set of characters from a string
• Strip block comments
• Strip comments from a string
• Strip control codes and extended characters from a string
• Strip whitespace from a string/Top and tail
• Subleq
• Subset sum problem
• Substring
• Substring/Top and tail
• Subtractive generator
• Sudoku
• Sum and Product Puzzle
• Sum and product of an array
• Sum digits of an integer
• Sum multiples of 3 and 5
• Sum of a series
• Sum of squares
• Sum to 100
• Superellipse
• Sutherland-Hodgman polygon clipping
• Symmetric difference
• Synchronous concurrency
• System time
• Table creation/Postal addresses
• Take notes on the command line
• Taxicab numbers
• Teacup rim text
• Temperature conversion
• Terminal control/Clear the screen
• Terminal control/Coloured text
• Terminal control/Display an extended character
• Terminal control/Ringing the terminal bell
• Terminal control/Unicode output
• Ternary logic
• Test a function
• Test integerness
• Text between
• Text processing/1
• Text processing/2
• Textonyms
• The ISAAC Cipher
• The Name Game
• The Twelve Days of Christmas
• Thiele's interpolation formula
• Thue-Morse
• Tic-tac-toe
• Time a function
• Tokenize a string
• Tokenize a string with escaping
• Top rank per group
• Topic variable
• Topological sort
• Topswops
• Total circles area
• Totient function
• Trabb Pardo–Knuth algorithm
• Tree traversal
• Trigonometric functions
• Truncatable primes
• Truncate a file
• Truth table
• Twelve statements
• Two Sum
• URL decoding
• URL encoding
• URL parser
• UTF-8 encode and decode
• Ulam spiral (for primes)
• Unbias a random generator
• Undefined values
• Unicode strings
• Unicode variable names
• Universal Turing machine
• Unix/ls
• Update a configuration file
• Use another language to call a function
• Validate International Securities Identification Number
• Vampire number
• Van Eck sequence
• Van der Corput sequence
• Variable size/Get
• Variable size/Set
• Variable-length quantity
• Variables
• Variadic function
• Vector
• Vector products
• Verify distribution uniformity/Naive
• Vigenère cipher
• Vigenère cipher/Cryptanalysis
• Visualize a tree
• Walk a directory/Non-recursively
• Walk a directory/Recursively
• Water collected between towers
• Web scraping
• Weird numbers
• Window creation
• Window creation/X11
• Wireworld
• Word break problem
• Word frequency
• Word wrap
• Write entire file
• Write float arrays to a text file
• XML/DOM serialization
• XML/Input
• XML/Output
• XML/XPath
• Xiaolin Wu's line algorithm
• Y combinator
• Yahoo! search interface
• Yin and yang
• Zebra puzzle
• Zeckendorf number representation
• Zero to the zero power
• Zhang-Suen thinning algorithm
• Zig-zag matrix