# 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
- Almost prime
- Amb
- Amicable pairs
- Anagrams
- Anagrams/Deranged anagrams
- Angle difference between two bearings
- 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
- 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
- Call a function in a shared library
- 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
- Circular primes
- 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 sorting algorithms' performance
- Conjugate transpose
- 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
- 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
- Draw a sphere

### 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 identity
- 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

- FASTA format
- 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 common directory path
- Find duplicate files
- 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
- 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
- Gapful numbers
- Gauss-Jordan matrix inversion
- Gaussian elimination
- Generate random chess position
- Get system command output
- 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
- Harshad or Niven series
- Hash from two arrays
- Hello world/Newbie
- Hello world/Web server
- Heronian triangles
- Hickerson series of almost integers
- Hofstadter-Conway $10,000 sequence
- Hofstadter Figure-Figure sequences
- Honeycombs
- Hough transform
- Huffman coding
- Humble numbers
- Hunt the Wumpus

### I

- 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
- Increasing gaps between consecutive Niven numbers
- Index finite lists of positive integers
- Inheritance/Multiple
- Integer overflow
- Intersecting number wheels
- Inverted index
- Inverted syntax
- Iterated digits squaring

### 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
- Law of cosines - triples
- Leonardo numbers
- Levenshtein distance/Alignment
- List comprehensions
- List rooted trees
- Long literals, with continuations
- Long multiplication
- Long year
- 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
- Main step of GOST 28147-89
- Make directory path
- Mastermind
- Matrix-exponentiation operator
- Matrix chain multiplication
- Matrix digital rain
- 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
- Minkowski question-mark function
- Modified random distribution
- Modular arithmetic
- Modular exponentiation
- Monads/List monad
- Monads/Maybe monad
- Monads/Writer monad
- Mouse position
- Move-to-front algorithm
- Multiple regression
- Multiplicative order
- Multisplit
- Munching squares
- Mutex

### 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
- Percolation/Bond percolation
- Percolation/Mean cluster density
- Percolation/Mean run density
- Percolation/Site percolation
- Perfect shuffle
- Perfect totient numbers
- 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
- 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
- Proper divisors
- Pseudo-random numbers/Combined recursive generator MRG32k3a
- 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
- 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
- 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
- Sexy primes
- Shoelace formula for polygonal area
- Shortest common supersequence
- Sierpinski pentagon
- Simulate input/Keyboard
- Simulate input/Mouse
- Smith numbers
- 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
- Stream merge
- String interpolation (included)
- Strip block comments
- Strong and weak primes
- Substitution cipher
- Subtractive generator
- Successive prime differences
- Suffixation of decimal numbers
- Sum and product puzzle
- Summarize and say sequence
- Sunflower fractal
- Super-d numbers
- Superellipse
- Superpermutation minimisation
- Sutherland-Hodgman polygon clipping

### T

- Table creation/Postal addresses
- Tarjan
- Taxicab numbers
- Teacup rim text
- Terminal control/Hiding the cursor
- Terminal control/Inverse video
- 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
- Thiele's interpolation formula
- Thue-Morse
- Tic-tac-toe
- Tokenize a string with escaping
- Tonelli-Shanks algorithm
- Topswops
- Total circles area
- Totient function
- Tree datastructures
- Tree from nesting levels
- Truncate a file
- Truth table

### U

### V

- Validate International Securities Identification Number
- Vampire number
- Van Eck sequence
- Variable-length quantity
- Variable size/Set
- 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
- ABC words
- Addition-chain exponentiation
- Addition chains
- Air mass
- Almkvist-Giullera formula for pi
- Alternade words
- 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
- 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/Verifying syntax
- Consecutive Primes With Ascending Or Descending Differences
- 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 the coins/0-1
- Cousin primes
- Create an object/Native demonstration
- Cubic Special Primes
- Curve that touches three points

### D

### F

- Fibonacci heap
- Fibonacci matrix-exponentiation
- Find URI in text
- Find first and last set bit of a long integer
- Find first missing positive
- Find if a point is within a triangle
- Find prime n for that reversed n is also prime
- Find words which contains most consonants
- Finite state machine
- Free polyominoes enumeration
- Frobenius numbers

### G

### I

### L

- Latin Squares in reduced form/Randomizing using Jacobson and Matthews’ Technique
- 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
- Longest common prefix
- Longest common suffix
- Longest palindromic substrings

### M

### N

### P

- Palindromic primes
- Parse EBNF
- Parse command-line arguments
- Particle swarm optimization
- Penrose tiling
- Pentomino tiling
- Permutations with repetitions
- Permutations with some identical elements
- Piprimes
- Pisano period
- Polynomial synthetic division
- Powerful numbers
- Practical numbers
- Price list behind API
- Prime triplets
- Prime words
- 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
- 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
- Robots
- Rosetta Code/List authors of task descriptions
- Rosetta Code/Run examples
- Rosetta Code/Tasks without examples
- Run as a daemon or service

### S

- Safe mode
- Sattolo cycle
- Selective file copy
- Self-hosting compiler
- Separate the house number from the street name
- Shift list elements to left by 3
- Sierpinski curve
- Sierpinski square curve
- Simulated annealing
- Sine wave
- Singly-linked list/Element removal
- Sleeping Beauty problem
- Smallest enclosing circle problem
- Smallest numbers
- Smallest power of 6 whose decimal expansion contains n
- Smallest square that begins with n
- Snake
- Snake and Ladder
- Solve a Rubik's Cube
- Solve triangle solitare puzzle
- Solving coin problems
- Sorting algorithms/Cycle sort
- Sorting algorithms/Tree sort on a linked list
- Special Divisors
- Special factorials
- Spoof game
- Square root by hand
- Starting a web browser
- Strassen's algorithm
- Subset sum problem
- Substring primes
- Suffix tree
- Sum data type
- Sum of the digits of n is substring of n

### 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
- Triplet of three numbers
- Twin primes
- Two bullet roulette
- Type detection

### U

### 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.