# Reports:Tasks not implemented in Erlang

**Awareness**

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## Contents

## Not implemented[edit]

These are currently not implemented in Erlang. Please implement some if you can. If any tasks are not possible or too complex in Erlang, they should not be on this list. To mark a task as such, add **{{omit from|Erlang}}**, preserving the capitalization of the language, to that task. It will appear below under the "Not Considered" section.

### A

- ASCII art diagram converter
- AVL tree
- Abbreviations, easy
- Abbreviations, simple
- Abelian sandpile model
- Abelian sandpile model/Identity
- Abundant odd numbers
- Active Directory/Search for a user
- Add a variable to a class instance at runtime
- Additive primes
- Aliquot sequence classifications
- Amb
- Angles (geometric), normalization and conversion
- Animate a pendulum
- Animation
- Append a record to the end of a text file
- Apply a digital filter (direct form II transposed)
- Approximate equality
- Archimedean spiral
- Arithmetic/Rational
- Arithmetic evaluation
- Associative array/Merging
- Attractive numbers
- Average loop length

### B

- Barnsley fern
- Base64 decode data
- Bell numbers
- Bernoulli numbers
- Bin given limits
- Bioinformatics/Sequence mutation
- Bioinformatics/base count
- Biorhythms
- Bitcoin/public point to address
- Bitmap/Bézier curves/Cubic
- Bitmap/Bézier curves/Quadratic
- Bitmap/Flood fill
- Bitmap/Histogram
- Bitmap/Midpoint circle algorithm
- Bitmap/PPM conversion through a pipe
- Bitmap/Read an image through a pipe
- Box the compass
- Brace expansion
- Brazilian numbers
- Break OO privacy
- Brownian tree
- Bulls and cows/Player
- Burrows–Wheeler transform

### C

- CUSIP
- Calculating the value of e
- Calendar
- Calendar - for "REAL" programmers
- Calkin-Wilf sequence
- Call a foreign-language function
- Call a function in a shared library
- Call an object method
- Canny edge detector
- Canonicalize CIDR
- Cantor set
- Carmichael 3 strong pseudoprimes
- Cartesian product of two or more lists
- Casting out nines
- Catmull–Clark subdivision surface
- Chaocipher
- Chaos game
- Check Machin-like formulas
- Check input device is a terminal
- Check output device is a terminal
- Chernick's Carmichael numbers
- Cheryl's birthday
- Chinese zodiac
- Cholesky decomposition
- Chowla numbers
- Circles of given radius through two points
- Circular primes
- Cistercian numerals
- Classes
- Closest-pair problem
- Collections
- Color of a screen pixel
- Color quantization
- Color wheel
- Colour bars/Display
- Colour pinstripe/Display
- Colour pinstripe/Printer
- Commatizing numbers
- Compare length of two strings
- Compiler/AST interpreter
- Compiler/code generator
- Compiler/lexical analyzer
- Compiler/syntax analyzer
- Compiler/virtual machine interpreter
- Conjugate transpose
- Consecutive primes with ascending or descending differences
- Constrained genericity
- Constrained random points on a circle
- Continued fraction/Arithmetic/Construct from rational number
- Convert decimal number to rational
- Convex hull
- Copy stdin to stdout
- Count in factors
- Cramer's rule
- Create a file on magnetic tape
- Cuban primes
- Currency
- Cut a rectangle
- Cyclotomic polynomial

### D

- Damm algorithm
- De Bruijn sequences
- Deal cards for FreeCell
- Death Star
- Deconvolution/1D
- Deconvolution/2D+
- Delegates
- Deming's Funnel
- Department numbers
- Determinant and permanent
- Determine if a string is collapsible
- Determine if a string is squeezable
- Determine if two triangles overlap
- Determine sentence type
- Dice game probabilities
- Digital root/Multiplicative digital root
- Discordian date
- Display a linear combination
- Display an outline as a nested table
- Diversity prediction theorem
- Dragon curve
- Draw a clock
- Draw a cuboid
- Draw a pixel
- Draw a rotating cube
- Draw a sphere

### E

- EKG sequence convergence
- Eban numbers
- Eertree
- Element-wise operations
- Elementary cellular automaton
- Elementary cellular automaton/Infinite length
- Elementary cellular automaton/Random Number Generator
- Elliptic Curve Digital Signature Algorithm
- Elliptic curve arithmetic
- Emirp primes
- Equilibrium index
- Esthetic numbers
- Euler's constant 0.5772...
- Euler's identity
- Euler's sum of powers conjecture
- Executable library
- Execute SNUSP
- Execute a Markov algorithm
- Exponentiation order
- Exponentiation with infix operators in (or operating on) the base
- Extend your language
- Extensible prime generator
- Extreme floating point values

### F

- FASTA format
- Faces from a mesh
- Factorial base numbers indexing permutations of a collection
- Factorions
- Fairshare between two and more
- Farey sequence
- Fast Fourier transform
- Faulhaber's formula
- Faulhaber's triangle
- Feigenbaum constant calculation
- Fermat numbers
- Fibonacci word
- Fibonacci word/fractal
- File extension is in extensions list
- File size distribution
- Find Chess960 starting position identifier
- Find duplicate files
- Find if a point is within a triangle
- Find largest left truncatable prime in a given base
- Find palindromic numbers in both binary and ternary bases
- Find the intersection of a line with a plane
- Find the intersection of two lines
- First perfect square in base n with n unique digits
- First power of 2 that has leading decimal digits of 12
- Fivenum
- Fixed length records
- Flipping bits game
- Floyd-Warshall algorithm
- Formal power series
- Fortunate numbers
- Four is magic
- Four is the number of letters in the ...
- Fractal tree
- Fraction reduction
- French Republican calendar
- Functional coverage tree
- Fusc sequence

### G

- GUI/Maximum window dimensions
- GUI component interaction
- GUI enabling/disabling of controls
- Galton box animation
- Gamma function
- Gauss-Jordan matrix inversion
- Gaussian elimination
- Generate Chess960 starting position
- Generate random chess position
- Get system command output
- Graph colouring
- Greatest subsequential sum
- Greyscale bars/Display

### H

- HTTPS/Authenticated
- HTTPS/Client-authenticated
- Halt and catch fire
- Hamming numbers
- Hello world/Graphical
- Hello world/Line printer
- Heronian triangles
- Hickerson series of almost integers
- Hilbert curve
- Hofstadter Figure-Figure sequences
- Honeycombs
- Horizontal sundial calculations
- Hough transform
- Humble numbers
- Hunt the Wumpus

### I

- IBAN
- ISBN13 check digit
- Idiomatically determine all the characters that can be used for symbols
- Idiomatically determine all the lowercase and uppercase letters
- Image convolution
- Image noise
- Imaginary base numbers
- Increasing gaps between consecutive Niven numbers
- Index finite lists of positive integers
- Inheritance/Multiple
- Inheritance/Single
- Integer overflow
- Intersecting number wheels
- Inverted syntax
- Isqrt (integer square root) of X
- Iterated digits squaring

### J

### K

- K-d tree
- K-means++ clustering
- Kernighans large earthquake problem
- Keyboard input/Flush the keyboard buffer
- Keyboard input/Keypress check
- Keyboard input/Obtain a Y or N response
- Keyboard macros
- Knapsack problem/Bounded
- Knapsack problem/Unbounded
- Knuth's algorithm S
- Knuth's power tree
- Koch curve
- Kolakoski sequence
- Kosaraju
- Kronecker product
- Kronecker product based fractals

### L

- LU decomposition
- Lah numbers
- Largest number divisible by its digits
- Largest proper divisor of n
- Latin Squares in reduced form
- Latin Squares in reduced form/Randomizing using Jacobson and Matthews’ Technique
- Law of cosines - triples
- Left factorials
- Leonardo numbers
- Levenshtein distance/Alignment
- List rooted trees
- Long literals, with continuations
- Long primes
- Long year
- Longest common substring
- Longest string challenge
- Loops/Increment loop index within loop body
- Loops/With multiple ranges
- Loops/Wrong ranges
- Lucky and even lucky numbers
- Ludic numbers
- Lychrel numbers

### M

- MAC Vendor Lookup
- MD5/Implementation
- Machine code
- Magic 8-ball
- Magic squares of doubly even order
- Magic squares of odd order
- Magic squares of singly even order
- Magnanimous numbers
- Main step of GOST 28147-89
- Make directory path
- Mastermind
- Matrix-exponentiation operator
- Matrix chain multiplication
- Matrix digital rain
- Maximum triangle path sum
- Mayan calendar
- Mayan numerals
- McNuggets problem
- Median filter
- Memory layout of a data structure
- Menu
- Merge and aggregate datasets
- Mertens function
- Metallic ratios
- Metronome
- Mian-Chowla sequence
- Mind boggling card trick
- Minesweeper game
- Minimal steps down to 1
- Minimum positive multiple in base 10 using only 0 and 1
- Minkowski question-mark function
- Modified random distribution
- Modular arithmetic
- Modular inverse
- Monads/List monad
- Monads/Maybe monad
- Monads/Writer monad
- Morse code
- Motzkin numbers
- Mouse position
- Move-to-front algorithm
- Multi-dimensional array
- Multiple regression
- Multiplicative order
- Munchausen numbers
- Munching squares
- Musical scale
- Möbius function

### N

- N'th
- N-smooth numbers
- Naming conventions
- Narcissist
- Narcissistic decimal number
- Natural sorting
- Nautical bell
- Negative base numbers
- Nested function
- Nested templated data
- Next highest int from digits
- Nim game
- Nimber arithmetic
- Non-transitive dice
- Nonoblock
- Nonogram solver
- Numbers with equal rises and falls
- Numeric error propagation
- Numerical and alphabetical suffixes
- Numerical integration
- Numerical integration/Gauss-Legendre Quadrature

### O

### P

- P-Adic numbers, basic
- P-Adic square roots
- P-value correction
- Padovan n-step number sequences
- Padovan sequence
- Palindrome dates
- Palindromic gapful numbers
- Pancake numbers
- Paraffins
- Parametric polymorphism
- Parametrized SQL statement
- Parse an IP Address
- Parsing/RPN to infix conversion
- Parsing/Shunting-yard algorithm
- Partial function application
- Partition an integer x into n primes
- Pascal's triangle/Puzzle
- Pascal matrix generation
- Password generator
- Pathological floating point problems
- Peaceful chess queen armies
- Peano curve
- Pell's equation
- Penney's game
- Pentagram
- Percentage difference between images
- Percolation/Bond percolation
- Percolation/Mean cluster density
- Percolation/Mean run density
- Percolation/Site percolation
- Perfect shuffle
- Perfect totient numbers
- Peripheral drift illusion
- Perlin noise
- Permutation test
- Permutations/Derangements
- Permutations/Rank of a permutation
- Permutations by swapping
- Pernicious numbers
- Phrase reversals
- Pierpont primes
- Pinstripe/Display
- Pinstripe/Printer
- Pisano period
- Plasma effect
- Play recorded sounds
- Playfair cipher
- Pointers and references
- Poker hand analyser
- Polymorphic copy
- Polymorphism
- Polynomial long division
- Polynomial regression
- Polyspiral
- Prime conspiracy
- Primes - allocate descendants to their ancestors
- Primorial numbers
- Problem of Apollonius
- Pseudo-random numbers/Combined recursive generator MRG32k3a
- Pseudo-random numbers/PCG32
- Pseudo-random numbers/Splitmix64
- Pseudo-random numbers/Xorshift star
- Pythagoras tree
- Pythagorean quadruples

### R

- RIPEMD-160
- RPG attributes generator
- Ramanujan's constant
- Ramanujan primes/twins
- Ramer-Douglas-Peucker line simplification
- Random Latin squares
- Random number generator (device)
- Random sentence from book
- Range consolidation
- Ranking methods
- Rare numbers
- Ray-casting algorithm
- Read a file character by character/UTF8
- Recaman's sequence
- Record sound
- Reduced row echelon form
- Reflection/Get source
- Reflection/List methods
- Reflection/List properties
- Rep-string
- Repeat
- Resistor mesh
- Respond to an unknown method call
- Retrieve and search chat history
- Reverse words in a string
- Roots of a quadratic function
- Roots of unity
- Rosetta Code/Rank languages by number of users
- Runge-Kutta method

### S

- S-expressions
- SEDOLs
- SHA-256 Merkle tree
- SOAP
- SQL-based authentication
- Safe addition
- Safe primes and unsafe primes
- Sailors, coconuts and a monkey problem
- Same fringe
- Search a list of records
- Secure temporary file
- Self numbers
- Send an unknown method call
- Send email
- Sequence: nth number with exactly n divisors
- Sequence: smallest number greater than previous term with exactly n divisors
- Sequence: smallest number with exactly n divisors
- Sequence of primes by trial division
- Sequence of primorial primes
- Set consolidation
- Set of real numbers
- Sexy primes
- Shoelace formula for polygonal area
- Shortest common supersequence
- Show ASCII table
- Sierpinski arrowhead curve
- Sierpinski pentagon
- Sierpinski square curve
- Simple windowed application
- Simulate input/Keyboard
- Simulate input/Mouse
- Sleeping Beauty problem
- Smarandache prime-digital sequence
- Smith numbers
- Snake
- Sokoban
- Solve a Holy Knight's tour
- Solve a Hopido puzzle
- Solve a Numbrix puzzle
- Solve the no connection puzzle
- Sort a list of object identifiers
- Sort an outline at every level
- Sort numbers lexicographically
- Sort three variables
- Sorting Algorithms/Circle Sort
- Sorting algorithms/Bogosort
- Sorting algorithms/Cocktail sort
- Sorting algorithms/Cocktail sort with shifting bounds
- Sorting algorithms/Comb sort
- Sorting algorithms/Counting sort
- Sorting algorithms/Heapsort
- Sorting algorithms/Pancake sort
- Sorting algorithms/Patience sort
- Sorting algorithms/Permutation sort
- Sorting algorithms/Radix sort
- Sorting algorithms/Shell sort
- Sorting algorithms/Stooge sort
- Sorting algorithms/Strand sort
- Sparkline in unicode
- Speech synthesis
- Spelling of ordinal numbers
- Spinning rod animation/Text
- Spiral matrix
- Split a character string based on change of character
- Square-free integers
- Square but not cube
- Square form factorization
- Stable marriage problem
- State name puzzle
- Statistics/Basic
- Statistics/Normal distribution
- Stem-and-leaf plot
- Stern-Brocot sequence
- Stirling numbers of the first kind
- Stirling numbers of the second kind
- Straddling checkerboard
- Strassen's algorithm
- Stream merge
- Strip block comments
- Strong and weak primes
- Subleq
- Substitution cipher
- Subtractive generator
- Successive prime differences
- Suffixation of decimal numbers
- Sum and product puzzle
- Sum of elements below main diagonal of matrix
- Sum to 100
- Summarize and say sequence
- Summarize primes
- Super-d numbers
- Superellipse
- Superpermutation minimisation
- Sutherland-Hodgman polygon clipping
- Sylvester's sequence

### T

- Tarjan
- Tau function
- Tau number
- Taxicab numbers
- Teacup rim text
- Terminal control/Coloured text
- Terminal control/Cursor movement
- Terminal control/Cursor positioning
- Terminal control/Dimensions
- Terminal control/Hiding the cursor
- Terminal control/Inverse video
- Terminal control/Positional read
- Terminal control/Preserve screen
- Terminal control/Ringing the terminal bell
- Terminal control/Unicode output
- Test integerness
- Textonyms
- The ISAAC Cipher
- The Name Game
- The sieve of Sundaram
- Thiele's interpolation formula
- Thue-Morse
- Tokenize a string with escaping
- Tonelli-Shanks algorithm
- Total circles area
- Totient function
- Tree datastructures
- Tree from nesting levels
- Truncatable primes
- Truth table
- Twelve statements
- Twin primes
- Two bullet roulette

### U

### V

### W

### Draft tasks without implementation[edit]

These tasks are drafts, meaning they largely need more work to turn them into full tasks. Perhaps you can help by trying to implement them in Erlang (after all, one of the key requirements for a task being non-draft is multiple implementations, preferably in widely different languages) but be aware that this may be difficult because of lack of definition of the task itself.

### A

- A* search algorithm
- ABC words
- ADFGVX cipher
- Addition-chain exponentiation
- Addition chains
- Air mass
- Alternade words
- Append numbers at same position in strings
- Arithmetic coding/As a generalized change of radix
- Aspect oriented programming
- Assertions in design by contract
- Audio alarm
- Audio frequency generator
- Audio overlap loop

### B

### C

- CLI-based maze-game
- Camel case and snake case
- Card shuffles
- Change e letters to i in words
- Changeable words
- Chebyshev coefficients
- Checksumcolor
- Chemical calculator
- Chess player
- Cipolla's algorithm
- Code segment unload
- Combinations with repetitions/Square digit chain
- Common list elements
- Common sorted list
- Compiler/Simple file inclusion pre processor
- Compiler/Verifying syntax
- Concatenate two primes is also prime
- Conjugate a Latin verb
- Continued fraction/Arithmetic/G(matrix ng, continued fraction n)
- Continued fraction/Arithmetic/G(matrix ng, continued fraction n1, continued fraction n2)
- Coprime triplets
- Coprimes
- Count how many vowels and consonants occur in a string
- Count the coins/0-1
- Cousin primes
- Create an object/Native demonstration
- Create your own text control codes
- Cubic Special Primes
- Curve that touches three points
- Cycle detection
- Cyclops numbers

### D

- Data Encryption Standard
- Dating agency
- Decimal floating point number to binary
- Decision tables
- Digit fifth powers
- Discrete Fourier transform
- Distinct Palindromes within decimal numbers
- Distinct power numbers
- Distribution of 0 Digits in factorial series
- Dominoes
- Doomsday rule
- Doubly-linked list/Element removal
- Draw pixel 2

### E

### F

- Fibonacci heap
- Fibonacci matrix-exponentiation
- Find URI in text
- Find adjacent primes which differ by a square integer
- Find first and last set bit of a long integer
- Find first missing positive
- Find minimum number of coins that make a given value
- Find prime n such that reversed n is also prime
- Find prime numbers of the form n*n*n+2
- Find square difference
- Find words which contain the most consonants
- Find words which contains all the vowels
- Find words which contains more than 3 e vowels
- Find words whose first and last three letters are equal
- Find words with alternating vowels and consonants
- Finite state machine
- Free polyominoes enumeration
- Frobenius numbers

### G

### I

### L

- Largest difference between adjacent primes
- Largest five adjacent number
- Largest palindrome product
- Largest prime factor
- Largest product in a grid
- Last list item
- Launch rocket with countdown and acceleration in stdout
- Length of an arc between two angles
- Line circle intersection
- Linux CPU utilization
- Logistic curve fitting in epidemiology
- Long stairs
- Longest common suffix
- Longest palindromic substrings
- Longest substrings without repeating characters

### M

- Magic constant
- Make a backup file
- Markov chain text generator
- Maximum difference between adjacent elements of list
- Mersenne primes
- Mine a bitcoin
- Minimum number of cells after, before, above and below NxN squares
- Minimum numbers of three lists
- Minimum primes
- Montgomery reduction
- Morpion solitaire
- Most frequent k chars distance
- Multi-base primes
- Multidimensional Newton-Raphson method
- Multiton

### N

- N-body problem
- NYSIIS
- Names to numbers
- Native shebang
- Neighbour primes
- Next special primes
- Nice primes
- Number triplets game
- Numbers divisible by their individual digits, but not by the product of their digits.
- Numbers in base-16 representation that cannot be written with decimal digits
- Numbers in base 10 that are palindromic in bases 2, 4, and 16
- Numbers which are not the sum of distinct squares
- Numbers which binary and ternary digit sum are prime
- Numbers whose count of divisors is prime
- Numbers with prime digits whose sum is 13
- Numbers with same digit set in base 10 and base 16
- Numeric separator syntax
- Numerical integration/Adaptive Simpson's method

### O

### P

- Palindromic primes
- Palindromic primes in base 16
- Pandigital prime
- Parse EBNF
- Parse command-line arguments
- Particle fountain
- Particle swarm optimization
- Penrose tiling
- Pentomino tiling
- Perceptron
- Permutations with some identical elements
- Permuted multiples
- Piprimes
- Polynomial derivative
- Polynomial synthetic division
- Positive decimal integers with the digit 1 occurring exactly twice
- Powerful numbers
- Practical numbers
- Price list behind API
- Prime numbers p which sum of prime numbers less or equal to p is prime
- Prime numbers which contain 123
- Prime triplets
- Prime words
- Primes which contain only one odd digit
- Primes whose first and last number is 3
- Primes whose sum of digits is 25
- Primes with digits in nondecreasing order
- Print debugging statement
- Print itself
- Process SMIL directives in XML data
- Product of divisors
- Proof
- Pseudorandom number generator image

### R

- Railway circuit
- Ramanujan primes
- Range modifications
- Raster bars
- Readline interface
- Recursive descent parser generator
- Remote agent/Agent interface
- Remote agent/Agent logic
- Remote agent/Simulation
- Remove vowels from a string
- Resistance calculator
- Resistance network calculator
- Reverse the gender of a string
- Reverse the order of lines in a text file while preserving the contents of each line
- Robots
- Rodrigues’ rotation formula
- Rosetta Code/List authors of task descriptions
- Rosetta Code/Run examples
- Rosetta Code/Tasks without examples
- Round-robin tournament schedule
- Run as a daemon or service

### S

- Safe mode
- Sattolo cycle
- Segmentation fault protection
- Selective file copy
- Self-hosting compiler
- Separate the house number from the street name
- Shift list elements to left by 3
- Show the (decimal) value of a number of 1s appended with a 3, then squared
- Sierpinski curve
- Simple turtle graphics
- Simulated annealing
- Sine wave
- Singly-linked list/Element removal
- Smallest enclosing circle problem
- Smallest multiple
- Smallest numbers
- Smallest power of 6 whose decimal expansion contains n
- Smallest square that begins with n
- Snake and Ladder
- Solve a Rubik's Cube
- Solve equations with substitution method
- Solve triangle solitare puzzle
- Solving coin problems
- Sort the letters of string in alphabetical order
- Sorting algorithms/Cycle sort
- Sorting algorithms/Tree sort on a linked list
- Special Divisors
- Special factorials
- Special neighbor primes
- Special pythagorean triplet
- Spoof game
- Square root by hand
- Starting a web browser
- Strange numbers
- Strange plus numbers
- Strange unique prime triplets
- Subset sum problem
- Substring primes
- Suffix tree
- Sum data type
- Sum of divisors
- Sum of first n cubes
- Sum of primes in odd positions is prime
- Sum of the digits of n is substring of n
- Summation of primes
- Sunflower fractal

### T

- Table creation
- Tamagotchi emulator
- Terminal control/Restricted width positional input/No wrapping
- Terminal control/Restricted width positional input/With wrapping
- Tetris
- Text between
- Text completion
- Text to HTML
- Three word location
- Time-based one-time password algorithm
- Topological sort/Extracted top item
- Transportation problem
- Triplet of three numbers
- Tropical algebra overloading
- Two identical strings
- Two sum
- Type detection

### U

### W

## Requiring Attention[edit]

### Examples[edit]

These tasks have implementations in Erlang, but somebody, somewhere, decided that the example implementation was faulty or in some other way requiring attention. If you're familiar with the task and language, please consider reviewing/correcting the example and removing the notice.

### Other pages[edit]

These are other pages related to Erlang which require attention; with your knowledge and assistance, we can improve the quality of the site's content.

## Not Considered[edit]

These tasks are not generally counted toward "unimplemented", as somebody, somewhere, decided that Erlang was inappropriate for these tasks, or implementations of them would be unenlightening. Feel free to try your hand at them anyway.

## End of List[edit]

Again, feel free to try your hand at any of the tasks listed on this page.