# Reports:Tasks not implemented in Elena

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## Contents

## Not implemented[edit]

These are currently not implemented in Elena. Please implement some if you can. If any tasks are not possible or too complex in Elena, they should not be on this list. To mark a task as such, add **{{omit from|Elena}}**, 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, automatic
- Abbreviations, easy
- Abbreviations, simple
- Abelian sandpile model
- Abelian sandpile model/Identity
- Abundant odd numbers
- Active Directory/Connect
- Active Directory/Search for a user
- Active object
- Additive primes
- Address of a variable
- Align columns
- Aliquot sequence classifications
- Almkvist-Giullera formula for pi
- Almost prime
- Anagrams/Deranged anagrams
- Angle difference between two bearings
- Angles (geometric), normalization and conversion
- Animate a pendulum
- Animation
- Anti-primes
- Append a record to the end of a text file
- Apply a digital filter (direct form II transposed)
- Approximate equality
- Arbitrary-precision integers (included)
- Archimedean spiral
- Arena storage pool
- Arithmetic-geometric mean
- Arithmetic-geometric mean/Calculate Pi
- Arithmetic/Complex
- Arithmetic/Rational
- Assertions
- Associative array/Merging
- Atomic updates
- Attractive numbers
- Average loop length
- Averages/Mean angle
- Averages/Mean time of day
- Averages/Pythagorean means

### B

- Balanced ternary
- Barnsley fern
- Base64 decode data
- Bell numbers
- Benford's law
- Bernoulli numbers
- Bin given limits
- Binary search
- Binary strings
- Bioinformatics/Sequence mutation
- Bioinformatics/base count
- Biorhythms
- Bitcoin/address validation
- Bitcoin/public point to address
- Bitmap
- Bitmap/Bresenham's line algorithm
- 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 a PPM file
- Bitmap/Read an image through a pipe
- Bitmap/Write a PPM file
- Bitwise IO
- Box the compass
- Brace expansion
- Brazilian numbers
- Break OO privacy
- Brownian tree
- Bulls and cows/Player
- Burrows–Wheeler transform

### C

- CRC-32
- CSV data manipulation
- CSV to HTML translation
- CUSIP
- Calculating the value of e
- Calendar
- Calkin-Wilf sequence
- Call a foreign-language function
- Call a function in a shared library
- Canny edge detector
- Canonicalize CIDR
- Cantor set
- Carmichael 3 strong pseudoprimes
- Cartesian product of two or more lists
- Casting out nines
- Catalan numbers
- Catalan numbers/Pascal's triangle
- Catmull–Clark subdivision surface
- Chaocipher
- Chaos game
- Chat server
- Check Machin-like formulas
- Check input device is a terminal
- Check output device is a terminal
- Checkpoint synchronization
- Chernick's Carmichael numbers
- Cheryl's birthday
- Chinese remainder theorem
- Chinese zodiac
- Cholesky decomposition
- Chowla numbers
- Church numerals
- Circles of given radius through two points
- Circular primes
- Cistercian numerals
- Closest-pair problem
- Color of a screen pixel
- Color quantization
- Color wheel
- Colour bars/Display
- Colour pinstripe/Display
- Colour pinstripe/Printer
- Combinations and permutations
- Combinations with repetitions
- Comma quibbling
- Commatizing numbers
- Compare length of two strings
- Compare sorting algorithms' performance
- Compile-time calculation
- Compiler/AST interpreter
- Compiler/code generator
- Compiler/lexical analyzer
- Compiler/syntax analyzer
- Compiler/virtual machine interpreter
- Concurrent computing
- Conditional structures
- Conjugate transpose
- Consecutive primes with ascending or descending differences
- 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 stdin to stdout
- Count in factors
- Count in octal
- Count occurrences of a substring
- Count the coins
- Cramer's rule
- Create a file on magnetic tape
- Create an HTML table
- Create an object at a given address
- Cuban primes
- Cumulative standard deviation
- Currency
- Currying
- Cut a rectangle
- Cyclotomic polynomial

### D

- DNS query
- Damm algorithm
- Date format
- Date manipulation
- Day of the week
- De Bruijn sequences
- Deal cards for FreeCell
- Death Star
- Deconvolution/1D
- Deconvolution/2D+
- Deepcopy
- Deming's Funnel
- Department numbers
- Detect division by zero
- Determinant and permanent
- Determine if a string has all the same characters
- Determine if a string has all unique characters
- Determine if a string is collapsible
- Determine if a string is numeric
- Determine if a string is squeezable
- Determine if only one instance is running
- Determine if two triangles overlap
- Determine sentence type
- Dice game probabilities
- Digital root/Multiplicative digital root
- Dijkstra's algorithm
- Dinesman's multiple-dwelling problem
- Dining philosophers
- Discordian date
- Display a linear combination
- Display an outline as a nested table
- Distributed programming
- Diversity prediction theorem
- Documentation
- 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 pixel
- Draw a rotating cube
- Draw a sphere
- Dutch national flag problem

### E

- EKG sequence convergence
- Eban numbers
- Echo server
- Eertree
- Egyptian division
- Egyptian fractions
- 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
- Empty directory
- Enforced immutability
- Entropy/Narcissist
- Enumerations
- Environment variables
- Esthetic numbers
- Ethiopian multiplication
- Euler's constant 0.5772...
- Euler's identity
- Euler's sum of powers conjecture
- Euler method
- Evaluate binomial coefficients
- Even or odd
- Events
- Executable library
- Execute HQ9+
- Execute SNUSP
- Execute a Markov algorithm
- Execute a system command
- Exponentiation operator
- 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
- FTP
- Faces from a mesh
- Factorial
- Factorial base numbers indexing permutations of a collection
- Factorions
- Factors of a Mersenne number
- Factors of an integer
- Fairshare between two and more
- Farey sequence
- Fast Fourier transform
- Faulhaber's formula
- Faulhaber's triangle
- Feigenbaum constant calculation
- Fermat numbers
- Fibonacci n-step number sequences
- Fibonacci word
- Fibonacci word/fractal
- File extension is in extensions list
- File modification time
- File size distribution
- Find Chess960 starting position identifier
- Find common directory path
- Find duplicate files
- Find if a point is within a triangle
- 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 perfect square in base n with n unique digits
- First power of 2 that has leading decimal digits of 12
- Five weekends
- Fivenum
- Fixed length records
- 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
- Fortunate numbers
- Forward difference
- Four bit adder
- Four is magic
- Four is the number of letters in the ...
- Fractal tree
- Fraction reduction
- Fractran
- French Republican calendar
- Function frequency
- Function prototype
- Functional coverage tree
- Fusc sequence

### G

- GUI/Maximum window dimensions
- GUI enabling/disabling of controls
- Galton box animation
- Gamma function
- Gapful numbers
- Gauss-Jordan matrix inversion
- Gaussian elimination
- General FizzBuzz
- Generate Chess960 starting position
- Generate random chess position
- Generator/Exponential
- Get system command output
- Globally replace text in several files
- Go Fish
- Graph colouring
- Gray code
- Grayscale image
- Greatest subsequential sum
- Greyscale bars/Display
- Guess the number/With feedback (player)

### H

- HTTP
- HTTPS
- HTTPS/Authenticated
- HTTPS/Client-authenticated
- Halt and catch fire
- Hamming numbers
- Handle a signal
- Harshad or Niven series
- Hash from two arrays
- Hash join
- Hello world/Line printer
- Hello world/Standard error
- Hello world/Web server
- Here document
- Heronian triangles
- Hickerson series of almost integers
- Hilbert curve
- Hofstadter-Conway $10,000 sequence
- Hofstadter Figure-Figure sequences
- Hofstadter Q sequence
- Holidays related to Easter
- Honeycombs
- Horizontal sundial calculations
- Host introspection
- Hostname
- Hough transform
- Huffman coding
- Humble numbers
- Hunt the Wumpus

### I

- IBAN
- ISBN13 check digit
- I before E except after C
- 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
- Include a file
- Increasing gaps between consecutive Niven numbers
- Index finite lists of positive integers
- Infinity
- Integer overflow
- Intersecting number wheels
- Introspection
- Inverted index
- Inverted syntax
- Isqrt (integer square root) of X
- Iterated digits squaring

### J

### K

- K-d tree
- K-means++ clustering
- Kaprekar numbers
- Kernighans large earthquake problem
- Keyboard input/Flush the keyboard buffer
- Keyboard input/Obtain a Y or N response
- Keyboard macros
- Knapsack problem/0-1
- Knapsack problem/Bounded
- Knapsack problem/Continuous
- Knapsack problem/Unbounded
- Knight's tour
- Knuth's power tree
- Koch curve
- Kolakoski sequence
- Kosaraju
- Kronecker product
- Kronecker product based fractals

### L

- LU decomposition
- LZW compression
- Lah numbers
- Langton's ant
- Largest int from concatenated ints
- Largest number divisible by its digits
- Largest proper divisor of n
- Last Friday of each month
- Last letter-first letter
- Latin Squares in reduced form
- Latin Squares in reduced form/Randomizing using Jacobson and Matthews’ Technique
- Law of cosines - triples
- Leap year
- Left factorials
- Legendre prime counting function
- Leonardo numbers
- Letter frequency
- Levenshtein distance
- Levenshtein distance/Alignment
- Linear congruential generator
- List comprehensions
- List rooted trees
- Long literals, with continuations
- Long multiplication
- Long primes
- Long year
- Longest common subsequence
- Longest common substring
- Longest increasing subsequence
- Longest string challenge
- Look-and-say sequence
- Loops/Break
- Loops/Continue
- Loops/Do-while
- Loops/Downward for
- Loops/Increment loop index within loop body
- Loops/N plus one half
- Loops/Nested
- Loops/With multiple ranges
- Loops/Wrong ranges
- Lucas-Lehmer test
- Lucky and even lucky numbers
- Ludic numbers
- Luhn test of credit card numbers
- Lychrel numbers

### M

- MAC Vendor Lookup
- MD4
- MD5
- MD5/Implementation
- Machine code
- Mad Libs
- Magic 8-ball
- Magic squares of odd order
- Magic squares of singly even order
- Magnanimous numbers
- Main step of GOST 28147-89
- Make directory path
- Mandelbrot set
- Map range
- Mastermind
- Matrix-exponentiation operator
- Matrix chain multiplication
- Matrix digital rain
- Matrix multiplication
- Matrix transposition
- Mayan calendar
- Mayan numerals
- Maze generation
- Maze solving
- McNuggets problem
- Median filter
- Memory allocation
- Memory layout of a data structure
- Menu
- Merge and aggregate datasets
- Mertens function
- Metallic ratios
- Metaprogramming
- Metered concurrency
- Metronome
- Mian-Chowla sequence
- Miller–Rabin primality test
- 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 exponentiation
- Modular inverse
- Monads/List monad
- Monads/Maybe monad
- Monads/Writer monad
- Monte Carlo methods
- Monty Hall problem
- Morse code
- Motzkin numbers
- Mouse position
- Move-to-front algorithm
- Multi-dimensional array
- Multifactorial
- Multiple regression
- Multiplication tables
- Multiplicative order
- Multisplit
- Munchausen numbers
- Munching squares
- Musical scale
- Mutex
- Möbius function

### N

- N-queens problem
- N-smooth numbers
- Named parameters
- Naming conventions
- Narcissist
- Narcissistic decimal number
- Natural sorting
- Nautical bell
- Negative base numbers
- Nested templated data
- Next highest int from digits
- Nim game
- Nimber arithmetic
- Non-continuous subsequences
- Non-decimal radices/Convert
- Non-decimal radices/Input
- Non-decimal radices/Output
- Non-transitive dice
- Nonoblock
- Nonogram solver
- Nth root
- Null object
- Number names
- Numbers with equal rises and falls
- Numeric error propagation
- Numerical and alphabetical suffixes
- Numerical integration
- Numerical integration/Gauss-Legendre Quadrature

### O

- OLE automation
- Object serialization
- Odd word problem
- One-dimensional cellular automata
- One-time pad
- One of n lines in a file
- OpenGL
- OpenWebNet password
- Operator precedence
- Optional parameters
- Order by pair comparisons
- Order disjoint list items
- Order two numerical lists
- Ordered partitions
- Ordered words

### P

- P-Adic numbers, basic
- P-Adic square roots
- P-value correction
- Padovan n-step number sequences
- Padovan sequence
- Palindrome dates
- Palindrome detection
- Palindromic gapful numbers
- Pancake numbers
- Pangram checker
- Paraffins
- Parallel brute force
- Parallel calculations
- Parametric polymorphism
- Parametrized SQL statement
- Parse an IP Address
- Parsing/RPN calculator algorithm
- Parsing/RPN to infix conversion
- Parsing/Shunting-yard algorithm
- Partition an integer x into n primes
- Partition function P
- Pascal's triangle
- Pascal's triangle/Puzzle
- Pascal matrix generation
- Password generator
- Pathological floating point problems
- Pattern matching
- 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
- Permutations/Derangements
- Permutations/Rank of a permutation
- Permutations by swapping
- Pernicious numbers
- Pi
- Pierpont primes
- Pig the dice game
- Pig the dice game/Player
- Pinstripe/Display
- Pinstripe/Printer
- Pisano period
- Plasma effect
- Play recorded sounds
- Playfair cipher
- Playing cards
- Plot coordinate pairs
- Pointers and references
- Poker hand analyser
- Polynomial long division
- Polynomial regression
- Polyspiral
- Population count
- Power set
- Pragmatic directives
- Price fraction
- Primality by Wilson's theorem
- Primality by trial division
- Prime conspiracy
- Prime decomposition
- Primes - allocate descendants to their ancestors
- Primorial numbers
- Priority queue
- Probabilistic choice
- Problem of Apollonius
- Program termination
- Proper divisors
- Pseudo-random numbers/Combined recursive generator MRG32k3a
- Pseudo-random numbers/PCG32
- Pseudo-random numbers/Splitmix64
- Pseudo-random numbers/Xorshift star
- Pythagoras tree
- Pythagorean quadruples
- Pythagorean triples

### R

- RCRPG
- RIPEMD-160
- RPG attributes generator
- RSA code
- Ramanujan's constant
- Ramanujan primes/twins
- Ramer-Douglas-Peucker line simplification
- Random Latin squares
- Random number generator (device)
- Random sentence from book
- Range consolidation
- Range expansion
- Range extraction
- Ranking methods
- Rare numbers
- Rate counter
- Ray-casting algorithm
- Read a configuration file
- Read a file character by character/UTF8
- Read a specific line from a file
- Read entire file
- Recaman's sequence
- Record sound
- Reduced row echelon form
- Reflection/Get source
- Regular expressions
- Remove lines from a file
- Rename a file
- Rendezvous
- Rep-string
- Repeat
- Resistor mesh
- Retrieve and search chat history
- Rock-paper-scissors
- 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
- Rosetta Code/Fix code tags
- Rosetta Code/Rank languages by number of users
- Rosetta Code/Rank languages by popularity
- Runge-Kutta method

### S

- S-expressions
- SEDOLs
- SHA-1
- SHA-256
- SHA-256 Merkle tree
- SOAP
- SQL-based authentication
- Safe addition
- Safe primes and unsafe primes
- Sailors, coconuts and a monkey problem
- Same fringe
- Scope/Function names and labels
- Scope modifiers
- Secure temporary file
- Self-describing numbers
- Self numbers
- Semiprime
- Semordnilap
- 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 non-squares
- Sequence of primorial primes
- Set
- Set consolidation
- Set puzzle
- Seven-sided dice from five-sided dice
- Sexy primes
- Shell one-liner
- Shoelace formula for polygonal area
- Shortest common supersequence
- Show ASCII table
- Show the epoch
- Sierpinski arrowhead curve
- Sierpinski carpet
- Sierpinski pentagon
- Sierpinski square curve
- Sierpinski triangle
- Sierpinski triangle/Graphical
- Sieve of Eratosthenes
- Simple database
- Simulate input/Keyboard
- Simulate input/Mouse
- Sleeping Beauty problem
- Smarandache prime-digital sequence
- Smith numbers
- Snake
- Sokoban
- Solve a Hidato puzzle
- 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 stability
- Sorting Algorithms/Circle Sort
- Sorting algorithms/Bead sort
- Sorting algorithms/Cocktail sort with shifting bounds
- Sorting algorithms/Heapsort
- Sorting algorithms/Merge sort
- Sorting algorithms/Patience sort
- Sorting algorithms/Permutation sort
- Sorting algorithms/Radix sort
- Sorting algorithms/Shell sort
- Sorting algorithms/Strand sort
- Soundex
- Sparkline in unicode
- Special characters
- Special variables
- 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
- Stair-climbing puzzle
- Start from a main routine
- 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
- Strip comments from a string
- Strip control codes and extended characters from a string
- Strong and weak primes
- Subleq
- Substitution cipher
- Subtractive generator
- Successive prime differences
- Sudoku
- Suffixation of decimal numbers
- Sum and product puzzle
- Sum digits of an integer
- Sum multiples of 3 and 5
- 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
- Symmetric difference
- Synchronous concurrency

### T

- Table creation/Postal addresses
- Take notes on the command line
- Tarjan
- Tau function
- Tau number
- Taxicab numbers
- Teacup rim text
- Terminal control/Coloured text
- Terminal control/Cursor movement
- Terminal control/Dimensions
- Terminal control/Display an extended character
- 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 a function
- Test integerness
- Text processing/1
- Text processing/2
- Text processing/Max licenses in use
- Textonyms
- The ISAAC Cipher
- The Name Game
- The sieve of Sundaram
- Thiele's interpolation formula
- Tic-tac-toe
- Tonelli-Shanks algorithm
- Topic variable
- Topological sort
- Topswops
- Total circles area
- Totient function
- Tree datastructures
- Tree from nesting levels
- Truth table
- Twin primes
- Two bullet roulette

### U

### V

- Validate International Securities Identification Number
- Vampire number
- Van Eck sequence
- Van der Corput sequence
- Variable-length quantity
- Variable size/Get
- Variable size/Set
- Vector
- Vector products
- Verhoeff algorithm
- Verify distribution uniformity/Chi-squared test
- Verify distribution uniformity/Naive
- Video display modes
- Vigenère cipher/Cryptanalysis
- Vogel's approximation method
- Voronoi diagram

### W

- Walk a directory/Recursively
- War card game
- Water collected between towers
- Web scraping
- Weird numbers
- Wilson primes of order n
- Window creation
- Window creation/X11
- Window management
- Word frequency
- Word ladder
- Word search
- Word wheel
- Wordiff
- Write float arrays to a text file
- Write language name in 3D ASCII
- Write to Windows event log

### 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 Elena (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
- Days between dates
- 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 adjacents primes which difference is 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 prefix
- 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
- Modulinos
- Montgomery reduction
- Morpion solitaire
- Most frequent k chars distance
- Multi-base primes
- Multidimensional Newton-Raphson method
- Multiline shebang
- 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 repetitions
- 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
- Ramsey's theorem
- 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 Elena, 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.

### No pages found.

### Other pages[edit]

These are other pages related to Elena 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 Elena was inappropriate for these tasks, or implementations of them would be unenlightening. Feel free to try your hand at them anyway.

### No pages found.

## End of List[edit]

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