Category:ALGOL 68
This programming language may be used to instruct a computer to perform a task.
Parameter passing methods: | By reference, By value |
---|---|
Type safety: | Safe |
Type strength: | Strong |
Type compatibility: | Structural |
Type expression: | Explicit |
Type checking: | Dynamic, Static |
See Also: |
If you know ALGOL 68, please write code for some of the tasks not implemented in ALGOL 68.
ALGOL 68 (short for ALGOrithmic Language 1968) is an imperative computer programming language that was conceived as a successor to the ALGOL 60 programming language, designed with the goal of a much wider scope of application and more rigorously defined syntax and semantics.
The main aims and principles of design of ALGOL 68:
- Completeness and clarity of design,
- Orthogonal design,
- Security,
- Efficiency:
- Static mode checking,
- Mode-independent parsing,
- Independent compilation,
- Loop optimization,
- Representations - in minimal & larger character sets.
Contents
Execute an ALGOL 68 program online[edit]
Grammar[edit]
The grammar for ALGOL 68 is officially in the two level, Van Wijngaarden grammar but a subset has been done in the one level Backus–Naur Form:
- Van Wijngaarden grammar: [1]
- Backus–Naur Form/Yacc: [2]
- Syntax Chart (Size 516.6 kB - File type application/pdf)
Resources[edit]
- ALGOL BULLETIN - March 1959 to August 1988, in 52 issues[3]
- Algol68 mailinglist - December 2008 - algol68-user AT lists.sourceforge.net[4]
- Algol68 group at linked: [5] - includes various famous compiler composers.
FYI: There are two online manual pages:
Or - if you prefer a hardcopy - you can try and pick up a hard cover manual like "Informal Introduction to Algol 68" - by C. H. Lindsey & S. V. Vander Meulen. Be sure to get the 1977 edition:
- www.amazon.com - Aboout $119
- barnesandnoble.com - about $40
IItA68 is a beautiful book, and makes great "bedtime" reading... Highly recommended!
- NEW: softwarepreservation.org has an on-line IItA68 PDF ready for download.
Editor modes:
- Emacs mode for Algol 68 supporting syntax highlighting and context-sensitive indentation.
- Vim script providing support for syntax highlighting.
- NEW: GeSHi syntax highlighting
Status[edit]
- 20th December 1968 - ALGOL 68's Final Report was ratified by UNESCO's IFIP working group 2.1 in Munich.
- 20th December 2008 - Zig Zag - the 100th ALGOL 68 code contribution on rosettacode.org!
- Happy 40th Birthday ALGOL 68,
- AND 50th Birthday ALGOL 58.
- 23rd August 2009 - algol68g-1.18.0-9h released
- 20th December 2009 - Happy 51st/41st Birthdays with Hamming numbers - the 200th ALGOL 68 code contribution on rosettacode.org!
- This time code was by Marcel van der Veer, author of Algol 68 Genie
- 25th October 2011 - Jejones3141 added Soundex - the 300th ALGOL 68 code specimen.
Revisions[edit]
- Mar. 1968: Draft Report on the Algorithmic Language ALGOL 68 - Edited by: A. van Wijngaarden, B.J. Mailloux, J.E.L. Peck and C.H.A. Koster.
- Oct. 1968: Penultimate Draft Report on the Algorithmic Language ALGOL 68 - Chapters 1-9 - Edited by: A. van Wijngaarden, B.J. Mailloux, J.E.L. Peck and C.H.A. Koster.
- Dec. 1968: Report on the Algorithmic Language ALGOL 68 - Offprint from Numerische Mathematik, 14, 79-218 (1969); Springer-Verlag. - Edited by: A. van Wijngaarden, B.J. Mailloux, J.E.L. Peck and C.H.A. Koster.
- Sep 1973: Revised Report on the Algorithmic Language Algol 68 - Springer-Verlag 1976 - Edited by: A. van Wijngaarden, B.J. Mailloux, J.E.L. Peck, C.H.A. Koster, M. Sintzoff, C.H. Lindsey, L.G.L.T. Meertens and R.G. Fisker.
Code samples[edit]
Most of the code samples provided here have a leading main:(
and a matching )
at the end. These are not actually required in the language, but are included so as to highlight that the code sample is complete, and works with (at least) ALGOL 68G unmodified.
On some compilers, it may be necessary to include appropriate "job cards" or precludes in order for the programs to compile successfully. Hopefully not too much else is required. Examples:
Brief Algol68 | Algol68 as in rosettacode | Actual ELLA Algol 68RS code |
print(("Hello, world!",new line)) |
main:( print(("Hello, world!",new line)) ) |
PROGRAM helloworld CONTEXT VOID USE standard BEGIN print(("Hello, world!", new line)) END FINISH |
Example of different program representations[edit]
At the time when ALGOL 68 was defined some predominant computers had 24 or 36 bit words, with 6 bit character sets. Hence it was desirable that ALGOL 68 should be able to run on machines with only uppercase. The official spec provided for different representations of the same program. Quote stropping (enclosing the bold words in single quotes) and Point stropping (preceeding the bold words with a dot) were used. A variant of Point stropping called RES stropping was also defined. In RES stropping some language-defined bold words are not preceded by a dot. A pragmatic comment may have been required to indicate which stropping convention was to be used, as in some of the examples below. Upper stropping (representing the bold words by upper case and non-bold words in lower case) was introduced by Algol 68R. Upper stropping is used by Algol 68RS and is one of the options for Algol 68G. Rutgers ALGOL 68 uses quote stropping. Most of the samples on Rosetta Code use Upper stropping. Example:
Algol68 as typically published
¢ bold/underline typeface ¢ mode xint = int; xint sum sq:=0; for i while sum sq≠70×70 do sum sq+:=i↑2 od |
quote stropping (similar to wiki)
'pr' quote 'pr' 'mode' 'xint' = 'int'; 'xint' sum sq:=0; 'for' i 'while' sum sq≠70×70 'do' sum sq+:=i↑2 'od' |
7-bit/ascii compiler
.PR UPPER .PR MODE XINT = INT; XINT sum sq:=0; FOR i WHILE sum sq/=70*70 DO sum sq+:=i**2 OD |
6-bits/byte compiler
.PR POINT .PR .MODE .XINT = .INT; .XINT SUM SQ:=0; .FOR I .WHILE SUM SQ .NE 70*70 .DO SUM SQ .PLUSAB I .UP 2 .OD |
RES stropping
.PR RES .PR mode .xint = int; .xint sum sq:=0; for i while sum sq≠70×70 do sum sq+:=i↑2 od |
Upper stropping
# upper case = bold # MODE XINT = INT; XINT sum sq:=0; FOR i WHILE sum sq /= 70*70 DO sum sq PLUSAB i UP 2 OD |
Coercion (casting)[edit]
ALGOL 68 has a hierarchy of contexts which determine which kind of coercions are available at a particular point in the program. These contexts are:
N a |
Context location | Coercions available in this context | Coercion examples | ||||
---|---|---|---|---|---|---|---|
Soft | Weak | Meek | Firm | Strong | |||
S t |
Right hand side of:
Also:
|
deproc- eduring | all soft then weak deref- erencing | all weak then deref- erencing | all meek then uniting | all firm then widening, rowing and voiding |
Widening occurs if there is no loss of precision. For example: An INT will be coerced to a REAL, and a REAL will be coerced to a LONG REAL. But not vice-versa. Examples: INT to LONG INT A variable can also be coerced (rowed) to an array of length 1. For example: INT to [1]INTetc |
F i |
|
Example:
UNION(INT,REAL) var := 1 | |||||
M e |
IF ~ THEN ... FIand FROM ~ BY ~ TO ~ WHILE ~ DO ... OD etc
|
Examples:
REF REF BOOL to BOOL | |||||
W e |
|
Examples:
REF BOOL to REF BOOL | |||||
S o |
The LHS of assignments, as "~" in: ~ := ... |
Example:
|
For more details about Primaries and Secondaries refer to Operator precedence.
See also[edit]
Code Specimen[edit]
Subcategories
This category has the following 3 subcategories, out of 3 total.
Pages in category "ALGOL 68"
The following 642 pages are in this category, out of 642 total.
2
A
- A+B
- Abbreviations, easy
- Abbreviations, simple
- ABC problem
- ABC words
- Abundant odd numbers
- Abundant, deficient and perfect number classifications
- Accumulator factory
- Ackermann function
- Address of a variable
- AKS test for primes
- Algol 68
- Align columns
- Aliquot sequence classifications
- Almost prime
- Alternade words
- Amb
- Amicable pairs
- Anagrams
- Anagrams/Deranged anagrams
- Anonymous recursion
- Apply a callback to an array
- Arbitrary-precision integers (included)
- Arithmetic evaluation
- Arithmetic-geometric mean
- Arithmetic/Complex
- Arithmetic/Integer
- Arithmetic/Rational
- Array concatenation
- Array length
- Arrays
- Assertions
- Associative array/Creation
- Associative array/Iteration
- Associative array/Merging
- Averages/Arithmetic mean
- Averages/Mean angle
- Averages/Median
- Averages/Pythagorean means
- Averages/Root mean square
- Averages/Simple moving average
B
- Babbage problem
- Bacon cipher
- Balanced brackets
- Balanced ternary
- Barnsley fern
- Base64 encode data
- Benford's law
- Bernoulli numbers
- Binary digits
- Binary search
- Binary strings
- Bioinformatics/base count
- Birthday problem
- Bitmap
- Bitmap/Bresenham's line algorithm
- Bitmap/Bézier curves/Cubic
- Bitmap/Midpoint circle algorithm
- Bitwise IO
- Bitwise operations
- Boolean values
- Box the compass
- Bulls and cows
C
- Caesar cipher
- Calculating the value of e
- Calendar
- Calendar - for "REAL" programmers
- Call a foreign-language function
- Call a function
- Cantor set
- Carmichael 3 strong pseudoprimes
- Case-sensitivity of identifiers
- Catalan numbers
- Catalan numbers/Pascal's triangle
- Catamorphism
- Change e letters to i in words
- Character codes
- Check that file exists
- Cholesky decomposition
- Circles of given radius through two points
- Classes
- Closures/Value capture
- Collections
- Combinations
- Combinations and permutations
- Comma quibbling
- Command-line arguments
- Commatizing numbers
- Comments
- Compare a list of strings
- Compiler/code generator
- Compound data type
- Concurrent computing
- Conditional structures
- Consecutive Primes With Ascending Or Descending Differences
- Constrained random points on a circle
- Continued fraction
- Convert seconds to compound duration
- Conway's Game of Life
- Copy a string
- Copy stdin to stdout
- Count in factors
- Count in octal
- Count occurrences of a substring
- Count the coins
- Cousin primes
- Cramer's rule
- CRC-32
- Create a file
- Create a two-dimensional array at runtime
- Create an HTML table
- CSV data manipulation
- CSV to HTML translation
- Cuban primes
- Cumulative standard deviation
- Currency
- Currying
- CUSIP
D
- Damm algorithm
- Date format
- Day of the week
- Define a primitive data type
- Delegates
- Delete a file
- Department numbers
- Detect division by zero
- 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 numeric
- Determine if a string is squeezable
- Digital root
- Digital root/Multiplicative digital root
- Dijkstra's algorithm
- Dinesman's multiple-dwelling problem
- Dot product
- Doubly-linked list/Definition
- Doubly-linked list/Element definition
- Doubly-linked list/Element insertion
- Doubly-linked list/Traversal
- Dragon curve
E
- Egyptian division
- Egyptian fractions
- Element-wise operations
- Emirp primes
- Empty directory
- Empty program
- Empty string
- Enforced immutability
- Entropy
- Entropy/Narcissist
- Enumerations
- Environment variables
- Equilibrium index
- Ethiopian multiplication
- Euler method
- Euler's identity
- Euler's sum of powers conjecture
- Evaluate binomial coefficients
- Even or odd
- Evolutionary algorithm
- Exceptions
- Exceptions/Catch an exception thrown in a nested call
- Execute a system command
- Execute Brain****
- Execute HQ9+
- Execute SNUSP
- Exponentiation operator
- Exponentiation order
- Exponentiation with infix operators in (or operating on) the base
- Extend your language
- Extract file extension
F
- Factorial
- Factorions
- Factors of a Mersenne number
- Factors of an integer
- Fast Fourier transform
- Feigenbaum constant calculation
- Fibonacci n-step number sequences
- Fibonacci sequence
- Fibonacci word
- File extension is in extensions list
- File input/output
- File modification time
- File size
- Filter
- Find common directory path
- Find first and last set bit of a long integer
- Find limit of recursion
- Find the intersection of two lines
- Find words which contains all the vowels
- Find words which contains more than 3 e vowels
- Find words which first and last three letters are equals
- Find words with alternating vowels and consonants
- First power of 2 that has leading decimal digits of 12
- First-class functions
- First-class functions/Use numbers analogously
- Five weekends
- FizzBuzz
- Flatten a list
- Flow-control structures
- Floyd's triangle
- Forest fire
- Fork
- Formatted numeric output
- Forward difference
- Fractran
- Frobenius numbers
- Function composition
- Function definition
- Function prototype
- Fusc sequence
G
- Gamma function
- Gaussian elimination
- General FizzBuzz
- Generalised floating point addition
- Generalised floating point multiplication
- Generate lower case ASCII alphabet
- Generator/Exponential
- Generic swap
- Gradient descent
- Gray code
- Greatest common divisor
- Greatest element of a list
- Greatest subsequential sum
- Guess the number
- Guess the number/With feedback
- Guess the number/With feedback (player)
H
- Hailstone sequence
- Hamming numbers
- Happy numbers
- Harshad or Niven series
- Haversine formula
- Hello world/Graphical
- Hello world/Line printer
- Hello world/Newbie
- Hello world/Newline omission
- Hello world/Standard error
- Hello world/Text
- Here document
- Heronian triangles
- Hickerson series of almost integers
- Higher-order functions
- Hilbert curve
- Hofstadter Q sequence
- Hofstadter-Conway $10,000 sequence
- Holidays related to Easter
- Horizontal sundial calculations
- Horner's rule for polynomial evaluation
- Host introspection
- Hostname
- HTTP
I
- I before E except after C
- Identity matrix
- Idiomatically determine all the lowercase and uppercase letters
- Implicit type conversion
- Include a file
- Increment a numerical string
- Infinity
- Input loop
- Input/Output for lines of text
- Input/Output for pairs of numbers
- Integer comparison
- Integer overflow
- Integer sequence
- Intersecting number wheels
- Introspection
- Inverted syntax
- ISBN13 check digit
- Isqrt (integer square root) of X
- Iterated digits squaring
K
L
- Langton's ant
- Largest int from concatenated ints
- Law of cosines - triples
- Leap year
- Least common multiple
- Left factorials
- Leonardo numbers
- Letter frequency
- Levenshtein distance
- Linear congruential generator
- List comprehensions
- Literals/Floating point
- Literals/Integer
- Literals/String
- Logical operations
- Long multiplication
- Longest common prefix
- Longest common subsequence
- Longest common suffix
- Longest string challenge
- Look-and-say sequence
- Loop over multiple arrays simultaneously
- Loops/Break
- Loops/Continue
- Loops/Do-while
- Loops/Downward for
- Loops/For
- Loops/For with a specified step
- Loops/Foreach
- Loops/Increment loop index within loop body
- Loops/Infinite
- Loops/N plus one half
- Loops/Nested
- Loops/While
- Loops/With multiple ranges
- Lucas-Lehmer test
- Ludic numbers
- Luhn test of credit card numbers
- Lychrel numbers
M
- Mad Libs
- Magic 8-ball
- Magic squares of odd order
- Man or boy test
- Mandelbrot set
- Map range
- Matrix multiplication
- Matrix transposition
- Matrix-exponentiation operator
- Maximum triangle path sum
- McNuggets problem
- MD5
- Memory allocation
- Memory layout of a data structure
- Menu
- Metaprogramming
- Metered concurrency
- Mian-Chowla sequence
- Middle three digits
- Miller–Rabin primality test
- Minimum positive multiple in base 10 using only 0 and 1
- Modular arithmetic
- Modular exponentiation
- Modular inverse
- Monads/Maybe monad
- Monads/Writer monad
- Monte Carlo methods
- Monty Hall problem
- Move-to-front algorithm
- Multi-dimensional array
- Multifactorial
- Multiple distinct objects
- Multiplication tables
- Multiplicative order
- Multisplit
- Munchausen numbers
- Mutual recursion
- Möbius function
N
- N'th
- N-queens problem
- Named parameters
- Naming conventions
- Narcissist
- Narcissistic decimal number
- Native shebang
- Negative base numbers
- Nested function
- Non-continuous subsequences
- Non-decimal radices/Convert
- Non-decimal radices/Input
- Non-decimal radices/Output
- Nth root
- Null object
- Number names
- Numbers which binary and ternary digit sum are prime
- Numbers with equal rises and falls
- Numeric error propagation
- Numeric separator syntax
- Numerical integration
O
P
- Padovan n-step number sequences
- Padovan sequence
- Palindrome dates
- Palindrome detection
- Pangram checker
- Parsing/RPN calculator algorithm
- Parsing/RPN to infix conversion
- Parsing/Shunting-yard algorithm
- Partial function application
- Pascal matrix generation
- Pascal's triangle
- Pascal's triangle/Puzzle
- Pathological floating point problems
- Pell's equation
- Perfect numbers
- Perfect shuffle
- Permutations
- Permutations with repetitions
- Pernicious numbers
- Phrase reversals
- Pi
- Pick random element
- Piprimes
- Playing cards
- Plot coordinate pairs
- Pointers and references
- Polymorphic copy
- Polymorphism
- Polynomial regression
- Population count
- Power set
- Pragmatic directives
- Price fraction
- Primality by trial division
- Prime conspiracy
- Prime decomposition
- Prime triplets
- Prime words
- Primes which sum of digits is 25
- Primes with digits in nondecreasing order
- Probabilistic choice
- Product of divisors
- Program name
- Program termination
- Proper divisors
- Pseudo-random numbers/PCG32
- Pseudo-random numbers/Splitmix64
- Pseudo-random numbers/Xorshift star
- Pythagorean quadruples
R
- Random number generator (included)
- Random numbers
- Random sentence from book
- Range expansion
- Range extraction
- Read a file line by line
- Read a specific line from a file
- Read entire file
- Real constants and functions
- Reduced row echelon form
- Regular expressions
- Remove duplicate elements
- Remove lines from a file
- Remove vowels from a string
- Rename a file
- Rep-string
- Repeat
- Repeat a string
- Return multiple values
- Reverse a string
- Reverse words in a string
- Rock-paper-scissors
- Roman numerals/Decode
- Roman numerals/Encode
- Roots of a function
- Roots of a quadratic function
- Roots of unity
- Rosetta Code/Rank languages by popularity
- Rot-13
- RSA code
- Run-length encoding
- Runge-Kutta method
- Runtime evaluation
- Runtime evaluation/In an environment
S
- S-expressions
- Safe primes and unsafe primes
- Sattolo cycle
- Scope modifiers
- Scope/Function names and labels
- Search a list
- Search a list of records
- SEDOLs
- Selective file copy
- Self-describing numbers
- Self-hosting compiler
- Semiprime
- Semordnilap
- Sequence of non-squares
- Sequence of primes by trial division
- Sequence: smallest number greater than previous term with exactly n divisors
- Sequence: smallest number with exactly n divisors
- Seven-sided dice from five-sided dice
- Shell one-liner
- Shift list elements to left by 3
- Shoelace formula for polygonal area
- Short-circuit evaluation
- Show ASCII table
- Show the (decimal) value of a number of 1s appended with a 3, then squared
- Sierpinski carpet
- Sierpinski triangle
- Sieve of Eratosthenes
- Singly-linked list/Element definition
- Singly-linked list/Element insertion
- Singly-linked list/Element removal
- Singly-linked list/Traversal
- Sleep
- Smallest numbers
- Smallest power of 6 whose decimal expansion contains n
- Smarandache prime-digital sequence
- Smith numbers
- Snake and Ladder
- Solve a Holy Knight's tour
- Sort an array of composite structures
- Sort an integer array
- Sort three variables
- Sort using a custom comparator
- Sorting algorithms/Bogosort
- Sorting algorithms/Bubble sort
- Sorting algorithms/Cocktail sort
- Sorting algorithms/Counting sort
- Sorting algorithms/Gnome sort
- Sorting algorithms/Heapsort
- Sorting algorithms/Insertion sort
- Sorting algorithms/Merge sort
- Sorting algorithms/Pancake sort
- Sorting algorithms/Quicksort
- Sorting algorithms/Radix sort
- Sorting algorithms/Selection sort
- Sorting algorithms/Shell sort
- Sorting algorithms/Stooge sort
- Soundex
- Special characters
- Special variables
- Spiral matrix
- Split a character string based on change of character
- Square but not cube
- Square-free integers
- Stack
- Stair-climbing puzzle
- Start from a main routine
- Stirling numbers of the first kind
- Stirling numbers of the second kind
- Straddling checkerboard
- Stream merge
- String append
- String case
- String comparison
- String concatenation
- String interpolation (included)
- String length
- String matching
- String prepend
- Strip a set of characters from a string
- Strip comments from a string
- Strip control codes and extended characters from a string
- Strip whitespace from a string/Top and tail
- Strong and weak primes
- Subleq
- Substring
- Substring primes
- Substring/Top and tail
- Successive prime differences
- Sudoku
- Sum and product of an array
- Sum data type
- Sum digits of an integer
- Sum multiples of 3 and 5
- Sum of a series
- Sum of squares
- Sum of the digits of n is substring of n
- Sum to 100
- Symmetric difference
- Synchronous concurrency
- System time
T
- Table creation/Postal addresses
- Tau number
- Temperature conversion
- Ternary logic
- Test integerness
- Text between
- Text processing/1
- Text processing/Max licenses in use
- Textonyms
- The Name Game
- The Twelve Days of Christmas
- Thiele's interpolation formula
- Thue-Morse
- Tokenize a string
- Tokenize a string with escaping
- Towers of Hanoi
- Trabb Pardo–Knuth algorithm
- Tree traversal
- Trigonometric functions
- Truncatable primes
- Truth table
- Twin primes
- Two identical strings
- Two sum