# Reports:Tasks not implemented in R

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## Contents

## Not implemented[edit]

These are currently not implemented in R. Please implement some if you can. If any tasks are not possible or too complex in R, they should not be on this list. To mark a task as such, add **{{omit from|R}}**, 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
- Abstract type
- Achilles numbers
- Active Directory/Connect
- Active Directory/Search for a user
- Active object
- Additive primes
- Algebraic data types
- Aliquot sequence classifications
- Almkvist-Giullera formula for pi
- Angle difference between two bearings
- Angles (geometric), normalization and conversion
- Append a record to the end of a text file
- Apply a digital filter (direct form II transposed)
- Arena storage pool
- Arithmetic/Rational
- Arithmetic evaluation
- Arithmetic numbers
- Ascending primes
- Associative array/Merging
- Atomic updates
- Averages/Mean time of day

### B

- Balanced ternary
- Bell numbers
- Best shuffle
- Binary strings
- Bioinformatics/Sequence mutation
- Bitcoin/address validation
- Bitcoin/public point to address
- Bitmap/Bresenham's line algorithm
- Bitmap/Histogram
- Bitmap/Midpoint circle algorithm
- Bitmap/PPM conversion through a pipe
- Bitmap/Read a PPM file
- Bitmap/Read an image through a pipe
- Bitwise IO
- Brace expansion
- Brazilian numbers
- Brilliant numbers
- Burrows–Wheeler transform

### C

- CUSIP
- Calendar
- Calendar - for "REAL" programmers
- Calkin-Wilf sequence
- Call a foreign-language function
- Call an object method
- Canny edge detector
- Canonicalize CIDR
- Carmichael 3 strong pseudoprimes
- Casting out nines
- Catalan numbers/Pascal's triangle
- Catmull–Clark subdivision surface
- Chaocipher
- Check input device is a terminal
- Check output device is a terminal
- Checkpoint synchronization
- Chernick's Carmichael numbers
- Chinese zodiac
- Chowla numbers
- Circles of given radius through two points
- Circular primes
- Cistercian numerals
- Color quantization
- Color wheel
- Colorful numbers
- Colour pinstripe/Display
- Colour pinstripe/Printer
- 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
- Composite numbers k with no single digit factors whose factors are all substrings of k
- Concurrent computing
- Conjugate transpose
- Consecutive primes with ascending or descending differences
- Constrained genericity
- Continued fraction
- Continued fraction/Arithmetic/Construct from rational number
- Convert seconds to compound duration
- Convex hull
- Count in octal
- 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
- Cullen and Woodall numbers
- Currency
- Curzon numbers
- Cut a rectangle
- Cyclops numbers
- Cyclotomic polynomial

### D

- De Bruijn sequences
- Death Star
- Deceptive numbers
- Deconvolution/2D+
- Deepcopy
- Define a primitive data type
- Delegates
- Deming's funnel
- Descending primes
- Determine if only one instance is running
- Determine if two triangles overlap
- Determine sentence type
- Digital root/Multiplicative digital root
- Dijkstra's algorithm
- Dining philosophers
- Disarium numbers
- Discordian date
- Display a linear combination
- Display an outline as a nested table
- Distributed programming
- Dominoes
- Doubly-linked list/Definition
- Doubly-linked list/Element definition
- Doubly-linked list/Element insertion
- Doubly-linked list/Traversal
- Draw a clock
- Draw a cuboid
- Draw a pixel
- Draw a rotating cube
- Draw a sphere
- Duffinian numbers
- Dutch national flag problem

### E

- EKG sequence convergence
- Earliest difference between prime gaps
- Eban numbers
- Echo server
- Eertree
- Egyptian fractions
- Elementary cellular automaton
- Elementary cellular automaton/Infinite length
- Elementary cellular automaton/Random number generator
- Elliptic Curve Digital Signature Algorithm
- Elliptic curve arithmetic
- Enforced immutability
- Entropy/Narcissist
- Equal prime and composite sums
- Equilibrium index
- Erdös-Selfridge categorization of primes
- Esthetic numbers
- Euler's constant 0.5772...
- Euler's sum of powers conjecture
- Events
- Execute Brain****
- Execute Computer/Zero
- Execute HQ9+
- Execute SNUSP
- Execute a Markov algorithm
- Extensible prime generator

### F

- FTP
- Faces from a mesh
- Factorial base numbers indexing permutations of a collection
- Factorions
- Factors of a Mersenne number
- Fairshare between two and more
- Faulhaber's formula
- Faulhaber's triangle
- Feigenbaum constant calculation
- Fermat numbers
- Fibonacci n-step number sequences
- 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 two lines
- First perfect square in base n with n unique digits
- First power of 2 that has leading decimal digits of 12
- Fixed length records
- Flipping bits game
- Flow-control structures
- Floyd-Warshall algorithm
- Forest fire
- Formal power series
- Fortunate numbers
- Four bit adder
- Four is the number of letters in the ...
- Fraction reduction
- Fractran
- French Republican calendar
- Function frequency
- Functional coverage tree

### G

### H

- HTTPS/Authenticated
- HTTPS/Client-authenticated
- Halt and catch fire
- Handle a signal
- Harshad or Niven series
- Hash join
- Hello world/Line printer
- Hello world/Newbie
- Here document
- Hickerson series of almost integers
- Hilbert curve
- History variables
- Home primes
- Honeycombs
- Horizontal sundial calculations
- Hough transform
- Huffman coding
- Humble numbers
- Hunt the Wumpus

### I

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

### J

### K

### L

- LZW compression
- Last letter-first letter
- Latin Squares in reduced form
- Latin Squares in reduced form/Randomizing using Jacobson and Matthews’ Technique
- Legendre prime counting function
- Levenshtein distance
- Levenshtein distance/Alignment
- List rooted trees
- Literals/Floating point
- Long literals, with continuations
- Long primes
- Long year
- Longest common subsequence
- Longest common substring
- Longest increasing subsequence
- Longest string challenge
- Loops/With multiple ranges
- Lucky and even lucky numbers
- Ludic numbers

### M

- MAC vendor lookup
- MD4
- MD5/Implementation
- Machine code
- Mad Libs
- Magic constant
- Magnanimous numbers
- Main step of GOST 28147-89
- Make directory path
- Mastermind
- Matrix digital rain
- Maximum triangle path sum
- Mayan calendar
- Mayan numerals
- Maze generation
- Maze solving
- Median filter
- Memory layout of a data structure
- Mertens function
- Metallic ratios
- Metered concurrency
- Metronome
- Mian-Chowla sequence
- Middle three digits
- Miller–Rabin primality test
- Minesweeper game
- Minimal steps down to 1
- Minimum multiple of m where digital sum equals m
- Minimum positive multiple in base 10 using only 0 and 1
- Minkowski question-mark function
- Modular arithmetic
- Modular exponentiation
- Modular inverse
- Monads/List monad
- Monads/Maybe monad
- Monads/Writer monad
- Morse code
- Motzkin numbers
- Move-to-front algorithm
- Multi-base primes
- Multi-dimensional array
- Multiplicative order
- Multisplit
- Munchausen numbers
- Munching squares
- Mutex
- Möbius function

### N

- N-smooth numbers
- Naming conventions
- Narcissist
- Natural sorting
- Nautical bell
- Negative base numbers
- Next highest int from digits
- Nonoblock
- Nonogram solver
- Numbers which are not the sum of distinct squares
- Numbers with equal rises and falls
- Numeric error propagation
- Numerical and alphabetical suffixes
- Numerical integration/Gauss-Legendre Quadrature

### O

### P

- P-Adic numbers, basic
- P-Adic square roots
- Padovan n-step number sequences
- Padovan sequence
- Palindrome dates
- Palindromic gapful numbers
- Pancake numbers
- Paraffins
- Parallel brute force
- Parallel calculations
- Parameterized SQL statement
- Parametric polymorphism
- Parse an IP Address
- Parsing/RPN calculator algorithm
- Parsing/RPN to infix conversion
- Parsing/Shunting-yard algorithm
- Particle fountain
- Partition an integer x into n primes
- Partition function P
- Pascal's triangle/Puzzle
- Pathological floating point problems
- Peaceful chess queen armies
- Pell's equation
- Pell numbers
- Pentomino tiling
- Percentage difference between images
- Percolation/Bond percolation
- Percolation/Mean cluster density
- Percolation/Mean run density
- Percolation/Site percolation
- Perfect totient numbers
- Periodic table
- Peripheral drift illusion
- Perlin noise
- Permutations/Derangements
- Permutations/Rank of a permutation
- Permutations by swapping
- Pernicious numbers
- Phrase reversals
- Pierpont primes
- Pig the dice game
- Pig the dice game/Player
- Pinstripe/Display
- Pinstripe/Printer
- Pisano period
- Plasma effect
- Playfair cipher
- Pointers and references
- Poker hand analyser
- Polymorphic copy
- Polyspiral
- Pragmatic directives
- Primality by Wilson's theorem
- Prime triangle
- Primes - allocate descendants to their ancestors
- Primorial numbers
- Problem of Apollonius
- Pseudo-random numbers/Combined recursive generator MRG32k3a
- Pseudo-random numbers/Middle-square method
- Pseudo-random numbers/PCG32
- Pseudo-random numbers/Splitmix64
- Pseudo-random numbers/Xorshift star
- Pythagorean triples

### R

- RCRPG
- RIPEMD-160
- 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
- Ranking methods
- Rare numbers
- Rate counter
- Read a configuration file
- Read a file character by character/UTF8
- Record sound
- Reflection/Get source
- Reflection/List methods
- Reflection/List properties
- Remove lines from a file
- Rename a file
- Rendezvous
- Rep-string
- Repunit primes
- Resistor mesh
- Respond to an unknown method call
- Retrieve and search chat history
- Rhonda numbers
- Rosetta Code/Find bare lang tags
- Rosetta Code/Rank languages by number of users
- Ruth-Aaron numbers

### S

- S-expressions
- SHA-256 Merkle tree
- SOAP
- SQL-based authentication
- Safe addition
- Safe primes and unsafe primes
- Same fringe
- Scope/Function names and labels
- Search a list of records
- Search in paragraph's text
- Secure temporary file
- Selectively replace multiple instances of a character within a string
- Self-describing numbers
- Self numbers
- Semiprime
- Semordnilap
- Send an unknown method call
- Sequence: nth number with exactly n divisors
- Sequence of primes by trial division
- Sequence of primorial primes
- Set
- Set consolidation
- Set of real numbers
- Set puzzle
- Set right-adjacent bits
- Sexy primes
- Shoelace formula for polygonal area
- Shortest common supersequence
- Sierpinski arrowhead curve
- Sierpinski pentagon
- Sierpinski square curve
- Simple database
- Simple turtle graphics
- Singleton
- Singly-linked list/Element definition
- Singly-linked list/Element insertion
- Singly-linked list/Traversal
- Smallest number k such that k+2^m is composite for all m less than k
- 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
- Sorting Algorithms/Circle Sort
- Sorting algorithms/Bead sort
- Sorting algorithms/Cocktail sort with shifting bounds
- Sorting algorithms/Heapsort
- Sorting algorithms/Pancake sort
- Sorting algorithms/Patience sort
- Sorting algorithms/Radix sort
- Sorting algorithms/Shell sort
- Sorting algorithms/Sleep sort
- Sorting algorithms/Strand sort
- Soundex
- Special characters
- Special variables
- Speech synthesis
- Spelling of ordinal numbers
- Spinning rod animation/Text
- Split a character string based on change of character
- Square-free integers
- Square but not cube
- Square form factorization
- Stable marriage problem
- Start from a main routine
- State name puzzle
- Stirling numbers of the first kind
- Stirling numbers of the second kind
- Straddling checkerboard
- Strassen's algorithm
- Stream merge
- String append
- String interpolation (included)
- String matching
- String prepend
- Strip a set of characters from a string
- Strip block comments
- Strip control codes and extended characters from a string
- Strong and weak primes
- Substitution cipher
- Substring/Top and tail
- Subtractive generator
- Successive prime differences
- Sudoku
- Suffixation of decimal numbers
- Sum and product puzzle
- Sum to 100
- Summarize and say sequence
- Summarize primes
- Superellipse
- Superpermutation minimisation
- Sutherland-Hodgman polygon clipping
- Sylvester's sequence
- Synchronous concurrency

### T

- Table creation/Postal addresses
- Tarjan
- Taxicab numbers
- Teacup rim text
- Terminal control/Coloured text
- Terminal control/Cursor movement
- Terminal control/Cursor positioning
- Terminal control/Dimensions
- Terminal control/Inverse video
- Terminal control/Positional read
- Ternary logic
- Test integerness
- Textonyms
- The Name Game
- The sieve of Sundaram
- Thiele's interpolation formula
- Tokenize a string with escaping
- Tonelli-Shanks algorithm
- Topic variable
- Total circles area
- Totient function
- Tree datastructures
- Tree from nesting levels
- Tree traversal
- Truncatable primes
- Twelve statements
- Twin primes
- Two's complement
- Two bullet roulette

### U

### V

- Validate International Securities Identification Number
- Vampire number
- Van Eck sequence
- Van der Corput sequence
- Variable-length quantity
- Variable declaration reset
- Variable size/Set
- Vector
- Verhoeff algorithm
- Video display modes
- Vigenère cipher/Cryptanalysis
- Visualize a tree
- Vogel's approximation method

### 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 R (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
- Anadromes
- Anagram generator
- Append numbers at same position in strings
- Arithmetic coding/As a generalized change of radix
- Arithmetic derivative
- Aspect oriented programming
- Assertions in design by contract
- Audio alarm
- Audio frequency generator
- Audio overlap loop
- Autogram checker

### B

- B-spline
- Babylonian spiral
- Bacon cipher
- Banker's algorithm
- Base58Check encoding
- Base64 encode data
- Base 16 numbers needing a to f
- Bifid cipher
- Bilinear interpolation
- Binary coded decimal
- Bioinformatics/Global alignment
- Bioinformatics/Subsequence
- Birthday problem
- Black box
- Blackjack strategy
- Boids
- Boyer-Moore string search
- Brace expansion using ranges

### C

- CLI-based maze-game
- Camel case and snake case
- Card shuffles
- Changeable words
- Chebyshev coefficients
- Checksumcolor
- Chemical calculator
- Chess player
- Cipolla's algorithm
- Code segment unload
- Collect and sort square numbers in ascending order from three lists
- Combinations with repetitions/Square digit chain
- Common list elements
- Common sorted list
- Compiler/Preprocessor
- 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
- Count how many vowels and consonants occur in a string
- Count the coins/0-1
- Cousin primes
- Create an executable for a program in an interpreted language
- Create an object/Native demonstration
- Create your own text control codes
- Cross compilation
- Cubic special primes
- Curve that touches three points
- Cycle detection
- Cycles of a permutation

### D

- Data Encryption Standard
- Dating agency
- Day of the week of Christmas and New Year
- Days between dates
- Decimal floating point number to binary
- Decision tables
- Digit fifth powers
- Diophantine linear system solving
- Discrete Fourier transform
- Distinct palindromes within decimal numbers
- Distribution of 0 digits in factorial series
- Divide a rectangle into a number of unequal triangles
- 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 squares n where n+1 is prime
- Find words with alternating vowels and consonants
- Finite state machine
- First 9 prime Fibonacci number
- Four sides of square
- Free polyominoes enumeration
- Frobenius numbers

### G

### I

### L

- Largest difference between adjacent primes
- Largest five adjacent number
- Largest palindrome product
- 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
- Long stairs
- Longest common prefix
- Longest common suffix
- Longest palindromic substrings
- Longest substrings without repeating characters

### M

- Make a backup file
- Marching squares
- Markov chain text generator
- Matrix with two diagonals
- Maximum difference between adjacent elements of list
- Mersenne primes
- Minimum number of cells after, before, above and below NxN squares
- Minimum numbers of three lists
- Minimum primes
- Montgomery reduction
- Morpion solitaire
- Mosaic matrix
- Most frequent k chars distance
- Multidimensional Newton-Raphson method
- Multiline shebang
- Multiton

### N

- N-body problem
- N-queens minimum and knights and bishops
- NYSIIS
- Names to numbers
- Native shebang
- Neighbour primes
- Next special primes
- Nice primes
- Nimber arithmetic
- 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 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
- Pan base non-primes
- Pandigital prime
- Parse EBNF
- Parse command-line arguments
- Particle swarm optimization
- Penrose 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 for which the sum of primes less than 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
- Proof
- Pseudorandom number generator image

### R

- Railway circuit
- Ramanujan primes
- Ramsey's theorem
- Range modifications
- Raster bars
- Readline interface
- Recursive descent parser generator
- Red black tree sort
- 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
- 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 and Sophie Germain primes
- Safe mode
- Sanitize user input
- 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
- 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 hanging lantern problem
- Solve triangle solitare puzzle
- Solving coin problems
- Sort primes from list to a list
- 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
- Steady squares
- Strange numbers
- Strange unique prime triplets
- Subset sum problem
- Substring primes
- Suffix tree
- Sum data type
- Sum of primes in odd positions is prime
- Sum of square and cube digits of an integer are primes
- Sum of the digits of n is substring of n
- Sum of two adjacent numbers are primes
- Summation of primes

### 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
- The ISAAC cipher
- Three word location
- Time-based one-time password algorithm
- Topological sort/Extracted top item
- Transliterate English text using the Greek alphabet
- Triplet of three numbers
- Two identical strings
- Two sum
- Type detection

### U

### W

## Requiring Attention[edit]

### Examples[edit]

These tasks have implementations in R, 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 R which require attention; with your knowledge and assistance, we can improve the quality of the site's content.

### No pages found.

## Not Considered[edit]

These tasks are not generally counted toward "unimplemented", as somebody, somewhere, decided that R 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.