# Reports:Tasks not implemented in Forth

**Awareness**

If

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

## Contents

## Not implemented[edit]

These are currently not implemented in Forth. Please implement some if you can. If any tasks are not possible or too complex in Forth, they should not be on this list. To mark a task as such, add **{{omit from|Forth}}**, 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
- Abelian sandpile model/Identity
- Abundant odd numbers
- Active Directory/Connect
- Active Directory/Search for a user
- Active object
- Aliquot sequence classifications
- Almkvist-Giullera formula for pi
- Almost prime
- Amb
- Anagrams
- Anagrams/Deranged anagrams
- 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)
- Archimedean spiral
- Arena storage pool
- Arithmetic-geometric mean/Calculate Pi
- Arithmetic evaluation
- Associative array/Merging
- Atomic updates
- Attractive numbers
- Average loop length
- Averages/Mean angle
- Averages/Mean time of day
- Averages/Mode

### B

- Balanced ternary
- Bell numbers
- Bernoulli numbers
- Best shuffle
- Bin given limits
- Bioinformatics/Sequence mutation
- Biorhythms
- Bitcoin/address validation
- Bitcoin/public point to address
- Bitmap/Bézier curves/Cubic
- Bitmap/Bézier curves/Quadratic
- Bitmap/PPM conversion through a pipe
- Bitmap/Read an image through a pipe
- Box the compass
- Brace expansion
- Brownian tree
- Bulls and cows/Player
- Burrows–Wheeler transform

### C

- CUSIP
- Calendar
- Calendar - for "REAL" programmers
- Calkin-Wilf sequence
- Canny edge detector
- Canonicalize CIDR
- Carmichael 3 strong pseudoprimes
- Cartesian product of two or more lists
- Casting out nines
- 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 zodiac
- Cholesky decomposition
- Chowla numbers
- Church numerals
- Circles of given radius through two points
- Cistercian numerals
- Closest-pair problem
- Color of a screen pixel
- Color quantization
- Color wheel
- Colour pinstripe/Display
- Colour pinstripe/Printer
- Combinations
- Combinations and permutations
- Combinations with repetitions
- Commatizing numbers
- Compare length of two strings
- Compare sorting algorithms' performance
- Conjugate transpose
- Consecutive primes with ascending or descending differences
- Constrained random points on a circle
- Continued fraction/Arithmetic/Construct from rational number
- Convex hull
- Cramer's rule
- Create a file on magnetic tape
- Currency
- Cut a rectangle
- Cyclotomic polynomial

### D

- DNS query
- Date manipulation
- De Bruijn sequences
- Deal cards for FreeCell
- Death Star
- Deconvolution/1D
- Deconvolution/2D+
- Deepcopy
- Deming's Funnel
- 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 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
- Dining philosophers
- Discordian date
- Display a linear combination
- Display an outline as a nested table
- Distributed programming
- Diversity prediction theorem
- Doubly-linked list/Definition
- Doubly-linked list/Element definition
- Doubly-linked list/Element insertion
- Doubly-linked list/Traversal
- Draw a cuboid
- Draw a rotating cube

### E

- EKG sequence convergence
- Eban numbers
- Eertree
- 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
- Empty directory
- Entropy/Narcissist
- Equilibrium index
- Euler's constant 0.5772...
- Events
- Exceptions/Catch an exception thrown in a nested call
- Executable library
- Execute SNUSP
- Execute a Markov algorithm
- Exponentiation order
- Exponentiation with infix operators in (or operating on) the base
- Extensible prime generator

### F

- FTP
- 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 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 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
- First-class functions/Use numbers analogously
- First class environments
- First power of 2 that has leading decimal digits of 12
- Five weekends
- Fivenum
- Fixed length records
- Flipping bits game
- Floyd-Warshall algorithm
- Fork
- Formal power series
- Fortunate numbers
- Four is magic
- Four is the number of letters in the ...
- Fractal tree
- Fraction reduction
- Fractran
- French Republican calendar
- Functional coverage tree
- Fusc sequence

### G

- GUI/Maximum window dimensions
- GUI component interaction
- GUI enabling/disabling of controls
- Galton box animation
- Gauss-Jordan matrix inversion
- Gaussian elimination
- Generate random chess position
- Globally replace text in several files
- Go Fish
- Graph colouring
- Greyscale bars/Display
- Guess the number/With feedback
- Guess the number/With feedback (player)

### H

- HTTPS
- HTTPS/Authenticated
- HTTPS/Client-authenticated
- Halt and catch fire
- Harshad or Niven series
- Hash from two arrays
- Hello world/Newbie
- Hello world/Web server
- Heronian triangles
- Hofstadter-Conway $10,000 sequence
- Hofstadter Figure-Figure sequences
- Honeycombs
- Hough transform
- Huffman coding
- Humble numbers
- Hunt the Wumpus

### I

- 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
- Increasing gaps between consecutive Niven numbers
- Index finite lists of positive integers
- Integer overflow
- Intersecting number wheels
- Inverted index
- Inverted syntax

### J

### K

### L

- LU decomposition
- Lah numbers
- Largest int from concatenated ints
- Largest number divisible by its digits
- 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
- Legendre prime counting function
- Leonardo numbers
- Levenshtein distance/Alignment
- List comprehensions
- List rooted trees
- Long literals, with continuations
- Long multiplication
- Longest common subsequence
- Longest common substring
- Longest increasing subsequence
- Longest string challenge
- Loops/Increment loop index within loop body
- Loops/With multiple ranges
- Lucky and even lucky numbers
- Ludic numbers
- Lychrel numbers

### M

- MAC Vendor Lookup
- MD4
- MD5/Implementation
- Machine code
- Mad Libs
- 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
- Mayan calendar
- Mayan numerals
- Maze solving
- McNuggets problem
- Median filter
- Merge and aggregate datasets
- Metallic ratios
- Metered concurrency
- 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 exponentiation
- Monads/List monad
- Monads/Maybe monad
- Monads/Writer monad
- Motzkin numbers
- Mouse position
- Move-to-front algorithm
- Multiple regression
- Multiplicative order
- Multisplit
- Munching squares
- Mutex
- Möbius function

### N

- N-smooth numbers
- Natural sorting
- Nautical bell
- Negative base numbers
- Nested function
- Nested templated data
- Next highest int from digits
- Nim game
- Nimber arithmetic
- Non-continuous subsequences
- Non-transitive dice
- Nonoblock
- Nonogram solver
- Number names
- Numeric error propagation
- Numerical and alphabetical suffixes
- 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
- 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
- Partial function application
- Partition an integer x into n primes
- Partition function P
- 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
- Pentomino tiling
- 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
- Phrase reversals
- Pi
- Pick random element
- Pierpont primes
- Pig the dice game/Player
- Pinstripe/Display
- Pinstripe/Printer
- Pisano period
- Plasma effect
- Play recorded sounds
- Playfair cipher
- Plot coordinate pairs
- Poker hand analyser
- Polynomial long division
- Polynomial regression
- Polyspiral
- Pragmatic directives
- Prime conspiracy
- Primes - allocate descendants to their ancestors
- Primorial numbers
- Priority queue
- Problem of Apollonius
- Pseudo-random numbers/Middle-square method
- Pseudo-random numbers/PCG32
- Pseudo-random numbers/Xorshift star
- Pythagoras tree
- Pythagorean quadruples

### 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 (included)
- Random sentence from book
- Range consolidation
- Ranking methods
- Rare numbers
- Rate counter
- Ray-casting algorithm
- Read a file character by character/UTF8
- Read a specific line from a file
- Recaman's sequence
- Record sound
- Reduced row echelon form
- Reflection/Get source
- Reflection/List methods
- Reflection/List properties
- Remove lines from a file
- Rendezvous
- Resistor mesh
- Retrieve and search chat history
- Roots of a function
- 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
- SHA-1
- SHA-256 Merkle tree
- SOAP
- SQL-based authentication
- Safe primes and unsafe primes
- Same fringe
- Scope/Function names and labels
- Scope modifiers
- Search a list of records
- Secure temporary file
- Self numbers
- 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 primorial primes
- Set consolidation
- Set of real numbers
- Set puzzle
- Set right-adjacent bits
- Sexy primes
- Shoelace formula for polygonal area
- Shortest common supersequence
- Sierpinski pentagon
- Sierpinski square curve
- Simulate input/Keyboard
- Simulate input/Mouse
- Sleeping Beauty problem
- 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 array of composite structures
- Sort an outline at every level
- Sort disjoint sublist
- Sort numbers lexicographically
- Sort stability
- Sort using a custom comparator
- Sorting algorithms/Bead sort
- Sorting algorithms/Bogosort
- Sorting algorithms/Cocktail sort with shifting bounds
- Sorting algorithms/Counting sort
- Sorting algorithms/Pancake sort
- Sorting algorithms/Patience sort
- Sorting algorithms/Permutation sort
- Sorting algorithms/Radix sort
- Sorting algorithms/Sleep sort
- Sorting algorithms/Stooge sort
- Sorting algorithms/Strand sort
- Sparkline in unicode
- Speech synthesis
- Spelling of ordinal numbers
- Spiral matrix
- Square form factorization
- Stable marriage problem
- State name puzzle
- Statistics/Basic
- Statistics/Normal distribution
- 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
- Substitution cipher
- Subtractive generator
- Successive prime differences
- Suffixation of decimal numbers
- Sum and product puzzle
- Sum of elements below main diagonal of matrix
- Summarize and say sequence
- Super-d numbers
- Superellipse
- Superpermutation minimisation
- Sutherland-Hodgman polygon clipping
- Sylvester's sequence

### T

- Table creation/Postal addresses
- Tarjan
- Teacup rim text
- Terminal control/Hiding the cursor
- Terminal control/Positional read
- Terminal control/Unicode output
- Ternary logic
- Test a function
- Test integerness
- Text processing/2
- Textonyms
- The ISAAC Cipher
- The Name Game
- The sieve of Sundaram
- Thiele's interpolation formula
- Thue-Morse
- Tic-tac-toe
- Tonelli-Shanks algorithm
- Topswops
- Total circles area
- Totient function
- Tree datastructures
- Tree from nesting levels
- Truncate a file
- Truth table
- Twin primes
- Two bullet roulette

### U

### V

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

### 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 Forth (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
- 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 Golf: Code Golf
- 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/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
- Create an object/Native demonstration
- Create your own text control codes
- Cubic Special Primes
- Cullen and Woodall numbers
- Curve that touches three points
- Cyclops numbers

### 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
- Distinct power numbers
- Distribution of 0 Digits in factorial series
- Divide a rectangle into a number of unequal triangles
- 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 square difference
- Find squares n where n+1 is prime
- Find words which contain the most 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
- 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
- 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 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
- 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 with digits in nondecreasing order
- Print debugging statement
- Print itself
- Process SMIL directives in XML data
- Product of divisors
- Proof

### 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 and Sophie Germain primes
- Safe mode
- Sanitize user input
- 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
- Sierpinski curve
- Simple turtle graphics
- Simulated annealing
- Sine wave
- Singly-linked list/Element removal
- Smallest enclosing circle problem
- Smallest multiple
- Smallest number k such that k+2^m is composite for all m less than k
- 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 factorials
- Special neighbor primes
- Special pythagorean triplet
- Spoof game
- Square root by hand
- Starting a web browser
- Steady Squares
- 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
- Summation of primes
- Sunflower fractal

### T

- Table creation
- 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
- Tropical algebra overloading
- Type detection

### U

- URL shortener
- Ulam numbers
- Ultra useful primes
- Unicode polynomial equation
- Unique characters
- Unique characters in each string
- Unit testing
- Uno (Card Game)
- Untrusted environment
- Useless instructions
- User defined pipe and redirection operators
- Using a speech engine to highlight words
- Using the Meetup.com API

### W

## Requiring Attention[edit]

### Examples[edit]

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

### F

## Not Considered[edit]

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