Tasks not implemented in Crystal
Awareness
If Crystal is a language you like, or are interested in, please inform your fellow members of the Crystal community; this page can't be emptied without your and their participation.
If Crystal is a language you like, or are interested in, please inform your fellow members of the Crystal community; this page can't be emptied without your and their participation.
Tasks not implemented in Crystal
1
2
A
- ABC problem
- ADFGVX cipher
- ASCII art diagram converter
- AVL tree
- Abbreviations, easy
- Abelian sandpile model
- Abelian sandpile model/Identity
- Abundant odd numbers
- Abundant, deficient and perfect number classifications
- Achilles numbers
- Active Directory/Connect
- Active Directory/Search for a user
- Add a variable to a class instance at runtime
- Address of a variable
- Algebraic data types
- Align columns
- Aliquot sequence classifications
- Almkvist-Giullera formula for pi
- Almost prime
- Amb
- Anagram generator
- Anagrams/Deranged anagrams
- Anaprimes
- Angle difference between two bearings
- Angles (geometric), normalization and conversion
- Animate a pendulum
- Animated Spinners
- Animation
- Anonymous recursion
- Append a record to the end of a text file
- Apply a digital filter (direct form II transposed)
- Approximate equality
- Apéry's constant
- Arena storage pool
- Arithmetic derivative
- Arithmetic evaluation
- Arithmetic numbers
- Arithmetic-geometric mean/Calculate Pi
- Arithmetic/Rational
- Ascending primes
- Atomic updates
- Attractive numbers
- Average loop length
- Averages/Mean angle
- Averages/Mean time of day
B
- Babbage problem
- Babylonian spiral
- Balanced ternary
- Barnsley fern
- Bell numbers
- Bernstein basis polynomials
- Bifid cipher
- Bin given limits
- Binary strings
- Binomial transform
- Bioinformatics/Global alignment
- Bioinformatics/Sequence mutation
- Bioinformatics/base count
- Biorhythms
- Bitcoin/address validation
- Bitcoin/public point to address
- 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
- Bitwise operations
- Blum integer
- Boustrophedon transform
- Box the compass
- Boyer-Moore string search
- Brace expansion
- Brazilian numbers
- Break OO privacy
- Brilliant numbers
- Bron–Kerbosch algorithm
- Brownian tree
- Burrows–Wheeler transform
- Bézier curves/Intersections
C
- CSV data manipulation
- CSV to HTML translation
- CUSIP
- Calculating the value of e
- Calendar
- Calendar - for "REAL" programmers
- Calkin-Wilf sequence
- Call a function
- Call an object method
- Camel case and snake case
- Canny edge detector
- Canonicalize CIDR
- Cantor set
- Carmichael 3 strong pseudoprimes
- Casting out nines
- Catalan numbers/Pascal's triangle
- Catamorphism
- Catmull–Clark subdivision surface
- Centre and radius of a circle passing through 3 points in a plane
- Chaocipher
- Chaos game
- Character codes
- Chat server
- Check Machin-like formulas
- Check if a polygon overlaps with a rectangle
- Check if two polygons overlap
- Checkpoint synchronization
- Chernick's Carmichael numbers
- Cheryl's birthday
- Chinese zodiac
- Cholesky decomposition
- Chowla numbers
- Circles of given radius through two points
- Circular primes
- Cistercian numerals
- Closures/Value capture
- Collections
- Color of a screen pixel
- Color quantization
- Color wheel
- Colorful numbers
- Colour pinstripe/Display
- Colour pinstripe/Printer
- Comma quibbling
- Command-line arguments
- Commatizing numbers
- Compare a list of strings
- Compare length of two strings
- Compare sorting algorithms' performance
- Compile-time calculation
- Compiler/AST interpreter
- Compiler/Simple file inclusion pre processor
- 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
- Conditional structures
- Conjugate transpose
- Consecutive primes with ascending or descending differences
- Constrained random points on a circle
- Continued fraction
- Continued fraction/Arithmetic/Construct from rational number
- Continued fraction/Arithmetic/G(matrix ng, continued fraction n)
- Continued fraction/Arithmetic/G(matrix ng, continued fraction n1, continued fraction n2)
- Convert decimal number to rational
- Convert seconds to compound duration
- Convex hull
- Conway's Game of Life
- Count in factors
- Count occurrences of a substring
- Count the coins
- Cramer's rule
- Create an HTML table
- Create an object at a given address
- Cuban primes
- Cullen and Woodall numbers
- Currency
- Curzon numbers
- Cut a rectangle
- Cycles of a permutation
- Cyclops numbers
- Cyclotomic polynomial
D
- Damm algorithm
- Day of the week
- De Bruijn sequences
- De Polignac numbers
- Deal cards for FreeCell
- Death Star
- Deceptive numbers
- Deconvolution/1D
- Deconvolution/2D+
- Decorate-sort-undecorate idiom
- Deepcopy
- Define a primitive data type
- Delegates
- Delete a file
- Deming's funnel
- Department numbers
- Descending primes
- 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 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
- Dining philosophers
- Disarium numbers
- Discordian date
- Display a linear combination
- Display an outline as a nested table
- Distance and Bearing
- Distributed programming
- Distribution of 0 digits in factorial series
- Diversity prediction theorem
- Dominoes
- Doomsday rule
- 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
- Duffinian numbers
- Dutch national flag problem
- Dynamic variable names
E
- EKG sequence convergence
- Earliest difference between prime gaps
- Eban numbers
- Echo server
- Eertree
- Egyptian division
- 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
- Empty string
- Enforced immutability
- Engel expansion
- Environment variables
- Equal prime and composite sums
- Equilibrium index
- Erdös-Selfridge categorization of primes
- Erdős-Nicolas numbers
- Erdős-primes
- Esthetic numbers
- Ethiopian multiplication
- Euclid-Mullin sequence
- Euclidean rhythm
- Euler method
- Euler's constant 0.5772...
- Euler's identity
- Euler's sum of powers conjecture
- Evaluate binomial coefficients
- Events
- Exceptions
- Executable library
- Execute Brain****
- Execute Computer/Zero
- Execute HQ9+
- Execute SNUSP
- Execute a Markov algorithm
- Execute a system command
- Exponential digital sums
- 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
- FTP
- Faces from a mesh
- Factorial base numbers indexing permutations of a collection
- Factorial primes
- Factorions
- Factorize string into Lyndon words
- Fairshare between two and more
- Faulhaber's formula
- Faulhaber's triangle
- Feigenbaum constant calculation
- Fermat pseudoprimes
- Fibonacci n-step number sequences
- Fibonacci word
- Fibonacci word/fractal
- File extension is in extensions list
- File input/output
- File modification time
- File size
- File size distribution
- Filter
- 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
- 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
- First-class functions
- First-class functions/Use numbers analogously
- Five weekends
- Fivenum
- Fixed length records
- Flipping bits game
- Flow-control structures
- Floyd's triangle
- Floyd-Warshall algorithm
- Forbidden numbers
- 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 definition
- Function frequency
- Function prototype
- Functional coverage tree
- Fusc sequence
G
- GSTrans string conversion
- GUI component interaction
- GUI enabling/disabling of controls
- GUI/Maximum window dimensions
- Galton box animation
- Gauss-Jordan matrix inversion
- Gaussian elimination
- Gaussian primes
- Generate Chess960 starting position
- Generate lower case ASCII alphabet
- Generator/Exponential
- Get system command output
- Giuga numbers
- Globally replace text in several files
- Go Fish
- Goldbach's comet
- Golden ratio/Convergence
- Gotchas
- Graph colouring
- Greatest common divisor
- Greatest prime dividing the n-th cubefree number
- Greedy algorithm for Egyptian fractions
- Greyscale bars/Display
- Guess the number/With feedback (player)
H
- HTTPS
- HTTPS/Authenticated
- HTTPS/Client-authenticated
- Harmonic series
- Harriss Spiral
- Hash join
- Hashtron inference
- Hello world/Line printer
- Hello world/Newbie
- Hello world/Newline omission
- Hello world/Standard error
- Heronian triangles
- Hex words
- Higher-order functions
- Hilbert curve
- History variables
- Hofstadter Figure-Figure sequences
- Hofstadter Q sequence
- Hofstadter-Conway $10,000 sequence
- Holidays related to Easter
- Home primes
- Honaker primes
- Honeycombs
- Horizontal sundial calculations
- Horner's rule for polynomial evaluation
- Horse racing
- Host introspection
- Hough transform
- Huffman coding
- Hunt the Wumpus
I
- I before E except after C
- I'm a software engineer, get me out of here
- IBAN
- ISBN13 check digit
- Identity matrix
- Idiomatically determine all the characters that can be used for symbols
- Idiomatically determine all the lowercase and uppercase letters
- Idoneal numbers
- Image convolution
- Image noise
- Imaginary base numbers
- Inconsummate numbers in base 10
- Increasing gaps between consecutive Niven numbers
- Increment a numerical string
- Index finite lists of positive integers
- Infinity
- Inheritance/Multiple
- Inheritance/Single
- Inner classes
- Input loop
- Integer comparison
- Integer overflow
- Interactive programming (repl)
- Intersecting number wheels
- Introspection
- Inventory sequence
- Inverted index
- Inverted syntax
- Isograms and heterograms
- Isqrt (integer square root) of X
- Iterated digits squaring
J
- JSON pointer
- Jacobsthal numbers
- Jaro-Winkler distance
- Jensen's Device
- Jordan-Pólya numbers
- Joystick position
- Juggler sequence
- Jump anywhere
K
- K-d tree
- Kaprekar numbers
- Kernighans large earthquake problem
- Keyboard input/Flush the keyboard buffer
- Keyboard input/Keypress check
- Keyboard input/Obtain a Y or N response
- Keyboard macros
- Klarner-Rado sequence
- Knapsack problem/Continuous
- Knapsack problem/Unbounded
- Knight's tour
- Knuth's algorithm S
- 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 proper divisor of n
- Last Friday of each month
- Last letter-first letter
- Latin Squares in reduced form
- Law of cosines - triples
- Least common multiple
- Least m such that n! + m is prime
- Left factorials
- Levenshtein distance/Alignment
- Linear congruential generator
- List comprehensions
- List rooted trees
- Literals/Floating point
- Literals/Integer
- Literals/String
- Logical operations
- Logistic curve fitting in epidemiology
- Long year
- Longest common subsequence
- Longest common substring
- Longest increasing subsequence
- Longest string challenge
- Loop over multiple arrays simultaneously
- Loops/Break
- Loops/Continue
- Loops/Do-while
- Loops/For with a specified step
- Loops/Foreach
- Loops/Increment loop index within loop body
- Loops/N plus one half
- Loops/Nested
- Loops/With multiple ranges
- Loops/Wrong ranges
- Lucky and even lucky numbers
- Ludic numbers
- Lyndon word
M
- MAC vendor lookup
- MD4
- MD5/Implementation
- Machine code
- Mad Libs
- Magic 8-ball
- Magic constant
- Magic numbers
- 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
- Mandelbrot set
- Map range
- Mastermind
- Matrix chain multiplication
- Matrix digital rain
- Matrix multiplication
- Matrix transposition
- Matrix-exponentiation operator
- Maximum triangle path sum
- Mayan calendar
- Mayan numerals
- Maze generation
- Maze solving
- McNuggets problem
- Median filter
- Meissel–Mertens constant
- Memory allocation
- Memory layout of a data structure
- Menu
- Merge and aggregate datasets
- Mertens function
- Metallic ratios
- Metaprogramming
- Metered concurrency
- Metronome
- Mian-Chowla sequence
- Middle three digits
- 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
- Modified random distribution
- Modular arithmetic
- Monads/List monad
- Monads/Maybe monad
- Monads/Writer monad
- Monty Hall problem
- Morse code
- Motzkin numbers
- Mouse position
- Move-to-front algorithm
- Multi-base primes
- Multi-dimensional array
- Multiple distinct objects
- Multiple regression
- Multiplication tables
- Multiplicative order
- Multisplit
- Munchausen numbers
- Munching squares
- Musical scale
- Mutex
- Mutual recursion
- Möbius function
N
- N-queens problem
- Named parameters
- Naming conventions
- Narcissist
- Narcissistic decimal number
- Natural sorting
- Nautical bell
- Negative base numbers
- Nested function
- Next highest int from digits
- Non-continuous subsequences
- Non-decimal radices/Convert
- Non-decimal radices/Input
- Non-decimal radices/Output
- Non-transitive dice
- Nonoblock
- Nonogram solver
- Nth root
- Number names
- Numbers k such that the last letter of k is the same as the first letter of k+1
- Numbers which are not the sum of distinct squares
- Numbers which are the cube roots of the product of their proper divisors
- Numbers with equal rises and falls
- Numeric error propagation
- Numerical and alphabetical suffixes
- Numerical integration
- Numerical integration/Gauss-Legendre Quadrature
O
- O'Halloran numbers
- OLE automation
- Object serialization
- Odd word problem
- Old Russian measure of length
- Old lady swallowed a fly
- One of n lines in a file
- One-dimensional cellular automata
- One-time pad
- OpenGL
- OpenWebNet password
- Operator precedence
- Optional parameters
- Order by pair comparisons
- Order disjoint list items
- Ordered partitions
- Ordered words
- Ormiston pairs
- Ormiston triples
- Own digits power sum
P
- P-Adic numbers, basic
- P-Adic square roots
- P-value correction
- Padovan n-step number sequences
- Padovan sequence
- Pairs with common factors
- Palindrome dates
- Palindromic primes in base 16
- Pan base non-primes
- 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
- Partial function application
- Particle fountain
- Partition an integer x into n primes
- Partition function P
- Pascal matrix generation
- Pascal's triangle
- Pascal's triangle/Puzzle
- Peaceful chess queen armies
- Peano curve
- Pell numbers
- Pell's equation
- Penney's game
- Penta-power prime seeds
- Pentagram
- Pentomino tiling
- Percentage difference between images
- Percolation/Bond percolation
- Percolation/Mean cluster density
- Percolation/Mean run density
- Percolation/Site percolation
- Perfect numbers
- Perfect shuffle
- Perfect totient numbers
- Periodic table
- Peripheral drift illusion
- Perlin noise
- Permutation test
- Permutations by swapping
- Permutations/Derangements
- Permutations/Rank of a permutation
- Pernicious numbers
- Phrase reversals
- 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
- Polymorphic copy
- Polymorphism
- Polynomial long division
- Polynomial regression
- Polyspiral
- Power set
- Pragmatic directives
- Price fraction
- Primality by Wilson's theorem
- Prime conspiracy
- Prime decomposition
- Prime numbers whose neighboring pairs are tetraprimes
- Prime triangle
- Primes - allocate descendants to their ancestors
- Primes: n*2^m+1
- Primorial numbers
- Priority queue
- Probabilistic choice
- Problem of Apollonius
- Product of min and max prime factors
- Program name
- Program termination
- Proper divisors
- 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
- Pythagoras tree
Q
R
- RCRPG
- RIPEMD-160
- RSA code
- Radical of an integer
- Ramanujan primes/twins
- Ramanujan's constant
- Ramer-Douglas-Peucker line simplification
- Random Latin squares
- Random number generator (device)
- Random number generator (included)
- Random sentence from book
- Range consolidation
- Range extraction
- Ranking methods
- Rare numbers
- Ray-casting algorithm
- Read a configuration file
- Read a file line by line
- 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
- Regular expressions
- Remove lines from a file
- Rename a file
- Rendezvous
- Repeat
- Repunit primes
- Resistor mesh
- Respond to an unknown method call
- Retrieve and search chat history
- Return multiple values
- Reverse words in a string
- Rhonda numbers
- Riordan numbers
- Roman numerals/Decode
- Roman numerals/Encode
- Roots of a function
- Roots of a quadratic 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
- Rot-13
- Round-robin tournament schedule
- Run-length encoding
- Runtime evaluation
- Runtime evaluation/In an environment
- Ruth-Aaron numbers
S
- S-expressions
- SEDOLs
- SHA-256 Merkle tree
- SOAP
- SQL-based authentication
- Safe addition
- Safe primes and unsafe primes
- Sailors, coconuts and a monkey problem
- Same fringe
- Scope modifiers
- Scope/Function names and labels
- Sealed classes and methods
- Search a list
- Search a list of records
- Search in paragraph's text
- Secure temporary file
- Selectively replace multiple instances of a character within a string
- Self numbers
- Send an unknown method call
- Send email
- Sequence of non-squares
- Sequence of primorial primes
- 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
- Set
- Set consolidation
- Set of real numbers
- Set puzzle
- Set right-adjacent bits
- Set, the card game
- Seven-sided dice from five-sided dice
- Sexy primes
- Shell one-liner
- Shoelace formula for polygonal area
- Short-circuit evaluation
- Shortest common supersequence
- Show ASCII table
- Show the epoch
- Sierpinski arrowhead curve
- Sierpinski pentagon
- Sierpinski square curve
- Sierpinski triangle
- Sierpinski triangle/Graphical
- Sieve of Pritchard
- Simple database
- Simple turtle graphics
- Simple windowed application
- Simulate input/Keyboard
- Simulate input/Mouse
- Singleton
- Singly-linked list/Element definition
- Singly-linked list/Element insertion
- Singly-linked list/Traversal
- Singular value decomposition
- Sisyphus sequence
- Sleep
- Sleeping Beauty problem
- Smallest number k such that k+2^m is composite for all m less than k
- Smarandache prime-digital sequence
- Smarandache-Wellin primes
- Smith numbers
- Snake
- Sockets
- Sokoban
- Soloway's recurring rainfall
- Solve a Hidato puzzle
- Solve a Holy Knight's tour
- Solve a Hopido puzzle
- Solve a Numbrix puzzle
- Solve the no connection puzzle
- Sorensen–Dice coefficient
- 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 three variables
- Sort using a custom comparator
- Sorting Algorithms/Circle Sort
- Sorting algorithms/Bead sort
- Sorting algorithms/Bubble sort
- Sorting algorithms/Cocktail sort
- Sorting algorithms/Cocktail sort with shifting bounds
- Sorting algorithms/Comb sort
- Sorting algorithms/Counting sort
- Sorting algorithms/Gnome sort
- Sorting algorithms/Heapsort
- Sorting algorithms/Insertion sort
- Sorting algorithms/Pancake sort
- Sorting algorithms/Patience sort
- Sorting algorithms/Radix sort
- Sorting algorithms/Shell sort
- Sorting algorithms/Sleep sort
- Sorting algorithms/Stooge sort
- Sorting algorithms/Strand sort
- Sparkline in unicode
- Special characters
- Special variables
- Speech synthesis
- Spelling of ordinal numbers
- Sphenic numbers
- Spinning rod animation/Text
- Spiral matrix
- Square but not cube
- Square form factorization
- Square-free integers
- Stable marriage problem
- Stack traces
- Stair-climbing puzzle
- Start from a main routine
- State name puzzle
- Statistics/Basic
- Statistics/Normal distribution
- Steffensen's method
- Stern-Brocot sequence
- Stirling numbers of the first kind
- Stirling numbers of the second kind
- Straddling checkerboard
- Strassen's algorithm
- Stream merge
- String append
- String comparison
- String concatenation
- String interpolation (included)
- String matching
- String prepend
- Strip a set of characters from a string
- Strip block comments
- Strip comments from a string
- Strip control codes and extended characters from a string
- Strong and weak primes
- Sub-unit squares
- Subleq
- Substitution cipher
- Substring/Top and tail
- Subtractive generator
- Successive prime differences
- Suffixation of decimal numbers
- Sum and product puzzle
- Sum of elements below main diagonal of matrix
- Sum to 100
- Summarize and say sequence
- Summarize primes
- Super-Poulet numbers
- Super-d numbers
- Superellipse
- Superpermutation minimisation
- Sutherland-Hodgman polygon clipping
- Sylvester's sequence
- Symmetric difference
- Sync subtitles
- Syntax highlighting using Mediawiki formatting
T
- Table creation/Postal addresses
- Take notes on the command line
- Tarjan
- Tau function
- Tau number
- Taxicab numbers
- Teacup rim text
- Temperature conversion
- Terminal control/Clear the screen
- Terminal control/Coloured text
- Terminal control/Cursor movement
- Terminal control/Cursor positioning
- 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
- Ternary logic
- Test integerness
- Text processing/1
- Text processing/2
- Text processing/Max licenses in use
- The Name Game
- The sieve of Sundaram
- Thiele's interpolation formula
- Tic-tac-toe
- Time a function
- Tokenize a string with escaping
- Tonelli-Shanks algorithm
- Top rank per group
- Topic variable
- Topswops
- Total circles area
- Totient function
- Towers of Hanoi
- Trabb Pardo–Knuth algorithm
- Transliterate English text using the Greek alphabet
- Tree datastructures
- Tree from nesting levels
- Trigonometric functions
- Tropical algebra overloading
- Truncatable primes
- Truncate a file
- Truth table
- Tupper's self-referential formula
- Twelve statements
- Twin primes
- Twin primes whose sum is square number
- Two bullet roulette
- Two's complement
U
- UPC
- UTF-8 encode and decode
- Ukkonen’s suffix tree construction
- Ultra useful primes
- Unbias a random generator
- Undefined values
- Undulating numbers
- Unicode strings
- Universal Lambda Machine
- Universal Turing machine
- Unix/ls
- Unprimeable numbers
- Untouchable numbers
- Update a configuration file
- Use another language to call a function
- User input/Graphical
V
- Validate International Securities Identification Number
- Vampire number
- Van Eck sequence
- Van der Corput sequence
- Variable declaration reset
- Variable size/Get
- Variable size/Set
- Variable-length quantity
- Variables
- Variadic fixed-point combinator
- Variadic function
- Vector
- Verhoeff algorithm
- Verify distribution uniformity/Chi-squared test
- Verify distribution uniformity/Naive
- Video display modes
- Vigenère cipher
- Vigenère cipher/Cryptanalysis
- Visualize a tree
- Vogel's approximation method
- Voronoi diagram
W
- Wagstaff primes
- Walk a directory/Non-recursively
- Walk a directory/Recursively
- War card game
- Wasteful, equidigital and frugal numbers
- Water collected between towers
- Web scraping
- Wieferich primes
- Wilson primes of order n
- Window creation
- Window creation/X11
- Window management
- Wireworld
- Wolstenholme numbers
- Word ladder
- Word search
- Word wheel
- Word wrap
- Wordiff
- World Cup group stage
- Worthwhile task shaving
- Write entire file
- Write float arrays to a text file
- Write language name in 3D ASCII
- Write to Windows event log
X
Y
Z
Draft tasks not implemented in Crystal
1
3
A
- A* search algorithm
- ASCII control characters
- Addition chains
- Addition-chain exponentiation
- 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
- B-spline
- Bacon cipher
- Banker's algorithm
- Base 16 numbers needing a to f
- Base58Check encoding
- Bilinear interpolation
- Binary coded decimal
- Bioinformatics/Subsequence
- Birthday problem
- Black box
- Blackjack strategy
- Boids
- Brace expansion using ranges
- Brzozowski algebraic method
C
- CLI-based maze-game
- CORDIC
- Calmo numbers
- CalmoSoft primes
- Card shuffles
- Carmichael lambda function
- Centroid of a set of N-dimensional points
- 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
- Color separation
- Combinations with repetitions/Square digit chain
- Common list elements
- Common sorted list
- Compiler/Preprocessor
- Compiler/Verifying syntax
- Concatenate two primes is also prime
- Conjugate a Latin verb
- Consistent overhead byte stuffing
- Continued fraction convergents
- Convert CSV records to TSV
- Coprime triplets
- Coprimes
- Count how many vowels and consonants occur in a string
- Count the coins/0-1
- Countdown
- 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
D
- Data Encryption Standard
- 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
- Divide a rectangle into a number of unequal triangles
- Double Twin Primes
- Doubly-linked list/Element removal
- Draw pixel 2
E
- Eisenstein primes
- Elevator simulation
- English cardinal anagrams
- Erdős–Woods numbers
- Even numbers which cannot be expressed as the sum of two twin primes
- Exactly three adjacent 3 in lists
- Execute CopyPasta Language
- Extended Straddling Checkerboard
- External sort
- Extra primes
- Extract file extension
- Extreme primes
F
- Factor-perfect numbers
- 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 which contain all the vowels
- Find words which contain the most consonants
- Find words whose first and last three letters are equal
- 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
- Generalised floating point addition
- Generalised floating point multiplication
- Generate random numbers without repeating a value
- Geohash
- Geometric algebra
- Getting the number of decimal places
- Goodstein Sequence
- Gradient descent
- Greed
H
I
- IPC via named pipe
- IRC gateway
- Iccanobif primes
- Implicit type conversion
- Input/Output for lines of text
- Input/Output for pairs of numbers
- Integer long division
- Integer roots
- Interactive help
- Iterators
J
K
L
- L-system
- Lagrange Interpolation
- Largest difference between adjacent primes
- Largest five adjacent number
- Largest palindrome product
- Largest prime factor
- Largest product in a grid
- Last list item
- 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
- Longest common prefix
- Longest common suffix
- Longest palindromic substrings
- Longest substrings without repeating characters
- Lucas-Carmichael numbers
M
- Make a backup file
- Marching squares
- Matrix with two diagonals
- Maximum difference between adjacent elements of list
- McNaughton-Yamada-Thompson algorithm
- Mersenne primes
- Minimum number of cells after, before, above and below NxN squares
- Minimum numbers of three lists
- Minimum primes
- Modulinos
- Montgomery reduction
- Morpion solitaire
- Mosaic matrix
- Most frequent k chars distance
- Multidimensional Newton-Raphson method
- Multiline shebang
- Multiplicatively perfect numbers
- 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 10 that are palindromic in bases 2, 4, and 16
- Numbers in base-16 representation that cannot be written with decimal digits
- Numbers whose binary and ternary digit sums 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
- Odd and square numbers
- Odd squarefree semiprimes
- One-two primes
- OpenGL pixel shader
- OpenGL/Utah teapot
- Orbital elements
- Overloaded operators
P
- Palindromic primes
- Pandigital prime
- Parse EBNF
- Parse command-line arguments
- Particle swarm optimization
- Penholodigital squares
- Penrose tiling
- Perceptron
- Permutations with repetitions
- Permutations with some identical elements
- Permuted multiples
- Piprimes
- Pollard's rho algorithm
- Polynomial derivative
- Polynomial synthetic division
- Posit numbers/decoding
- Posit numbers/encoding
- 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 reciprocal sum
- 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
- Protecting Memory Secrets
- Pseudorandom number generator image
Q
R
- Railway circuit
- Rainbow
- 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
- 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
- Rice coding
- Robots
- Rodrigues’ rotation formula
- Roots of a cubic polynomial
- Rosetta Code/List authors of task descriptions
- Rosetta Code/Run examples
- Rosetta Code/Tasks without examples
- Run as a daemon or service
S
- SEND + MORE = MONEY
- Safe and Sophie Germain primes
- Safe mode
- Sanitize user input
- Sattolo cycle
- Segmentation fault protection
- Selection bias in clinical sciences
- Selective file copy
- Self-hosting compiler
- Separate the house number from the street name
- Shape-Machine
- Show the (decimal) value of a number of 1s appended with a 3, then squared
- Sierpinski curve
- Simulated annealing
- Simulated optics experiment/Data analysis
- Simulated optics experiment/Simulator
- Sine wave
- Singly-linked list/Element removal
- Singly-linked list/Reversal
- 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 solitaire 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
- Statistics/Chi-squared distribution
- Steady squares
- Strange numbers
- Strange plus numbers
- Strange unique prime triplets
- Sturmian word
- 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 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
- Sunflower fractal
- Szymański's algorithm
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 conventions and conversions
- Time-based one-time password algorithm
- Topological sort/Extracted top item
- Transportation problem
- Triangular numbers
- Triplet of three numbers
- Two sum
U
- Ulam numbers
- Unicode polynomial equation
- Unique characters
- Unique characters in each string
- Unit testing
- Uno (card game)
- Untrusted environment
- Upside-down numbers
- Use a REST API
- Useless instructions
- User defined pipe and redirection operators
- Using a speech engine to highlight words
V
W
- Walsh matrix
- Wave function collapse
- Waveform analysis/Doh ray me
- Waveform analysis/Top and tail
- Weather routing
- WebGL rotating F
- Welch's t-test
- WiktionaryDumps to words
- Word break problem
- Words containing "the" substring
- Words from neighbour ones
X
Tasks omitted from Crystal
End of List
Again, feel free to try your hand at any of the tasks listed on this page.