# Reports:Tasks not implemented in J

**Awareness**

If

**J**is a language you like, or are interested in, please inform your fellow members of the J community; this page can't be emptied without your and their participation.

## Contents

## Not implemented[edit]

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

### A

### B

### C

- Canonicalize CIDR
- Chat server
- Check input device is a terminal
- Chernick's Carmichael numbers
- Church numerals
- Color of a screen pixel
- Color wheel
- Colour pinstripe/Printer
- Compare length of two strings
- Compiler/AST interpreter
- Compiler/code generator
- Compiler/lexical analyzer
- Compiler/syntax analyzer
- Compiler/virtual machine interpreter
- Consecutive primes with ascending or descending differences
- Copy stdin to stdout
- Create a file on magnetic tape
- Create an object at a given address
- Cyclotomic polynomial

### D

### E

### F

### H

### K

### L

### M

- Machine code
- Main step of GOST 28147-89
- Mastermind
- Matrix digital rain
- Mayan calendar
- Merge and aggregate datasets
- Metallic ratios
- Metered concurrency
- 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
- Motzkin numbers
- Mouse position
- Mutex
- Möbius function

### N

### P

- P-Adic numbers, basic
- P-Adic square roots
- P-value correction
- Padovan n-step number sequences
- Palindrome dates
- Pancake numbers
- Parallel brute force
- Parametrized SQL statement
- Peaceful chess queen armies
- Percolation/Bond percolation
- Peripheral drift illusion
- Pierpont primes
- Pinstripe/Printer
- Pisano period
- Play recorded sounds
- Pseudo-random numbers/Combined recursive generator MRG32k3a
- Pseudo-random numbers/PCG32
- Pseudo-random numbers/Splitmix64
- Pseudo-random numbers/Xorshift star

### R

### S

- SHA-256 Merkle tree
- SOAP
- SQL-based authentication
- Secure temporary file
- Self numbers
- Send email
- Sequence: nth number with exactly n divisors
- Shortest common supersequence
- Sierpinski arrowhead curve
- Sierpinski pentagon
- Sierpinski square curve
- Simulate input/Keyboard
- Simulate input/Mouse
- Sleeping Beauty problem
- Snake
- Sokoban
- Solve a Hidato puzzle
- Solve a Hopido puzzle
- Solve a Numbrix puzzle
- Sort an outline at every level
- Sorting algorithms/Cocktail sort with shifting bounds
- Sorting algorithms/Sleep sort
- Speech synthesis
- Spelling of ordinal numbers
- Spinning rod animation/Text
- Square form factorization
- Strassen's algorithm
- Stream merge
- Suffixation of decimal numbers
- Sum and product puzzle
- Summarize primes
- Sylvester's sequence

### T

### 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 J (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

### B

### C

- CLI-based maze-game
- Camel case and snake case
- Change e letters to i in words
- Changeable words
- Checksumcolor
- Chemical calculator
- Chess player
- Code segment unload
- Combinations with repetitions/Square digit chain
- Common list elements
- 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 n1, continued fraction n2)
- Coprime triplets
- Count how many vowels and consonants occur in a string
- Count the coins/0-1
- Create your own text control codes
- Cubic Special Primes
- Cyclops numbers

### D

### E

### F

- Fibonacci heap
- Fibonacci matrix-exponentiation
- Find URI in text
- Find adjacents primes which difference is square integer
- 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

### G

### I

### L

- Largest difference between adjacent primes
- 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
- Logistic curve fitting in epidemiology
- Long stairs
- Longest palindromic substrings
- Longest substrings without repeating characters

### M

### N

- NYSIIS
- Neighbour primes
- Next special primes
- Number triplets game
- 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 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

### O

### P

- Palindromic primes
- Palindromic primes in base 16
- Pandigital prime
- Parse EBNF
- Particle fountain
- Penrose tiling
- Pentomino tiling
- Perceptron
- Permutations with some identical elements
- Permuted multiples
- Polynomial derivative
- Positive decimal integers with the digit 1 occurring exactly twice
- Powerful 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
- Print debugging statement
- Print itself
- Process SMIL directives in XML data
- Product of divisors
- Pseudorandom number generator image

### R

- Railway circuit
- Ramanujan primes
- Range modifications
- Raster bars
- Readline interface
- Remote agent/Agent interface
- Remote agent/Agent logic
- Remote agent/Simulation
- Remove vowels from a string
- Resistance calculator
- Resistance network calculator
- 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
- Segmentation fault protection
- Selective file copy
- 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
- 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
- Solve a Rubik's Cube
- Solve equations with substitution method
- Solving coin problems
- Sort the letters of string in alphabetical order
- 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
- Substring primes
- Sum data type
- Sum of divisors
- Sum of primes in odd positions is prime
- Summation of primes
- Sunflower fractal

### T

### U

### W

## Requiring Attention[edit]

### Examples[edit]

These tasks have implementations in J, 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 J 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 J 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.