Icon - Programming language

Icon is a programming language created in 1977 by Ralph Griswold.

#540on PLDB

47Years Old

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Icon is a very high-level programming language featuring goal-directed execution and many facilities for managing strings and textual patterns. It is related to SNOBOL and SL5, string processing languages. Icon is not object-oriented, but an object-oriented extension called Idol was developed in 1996 which eventually became Unicon.. Read more on Wikipedia...

Tags: programming language
Early development of Icon happened in University of Arizona
Explore Icon snippets on Rosetta Code
Icon on HOPL
Icon appears in the TIOBE Index
Icon Ubuntu package
Pygments supports syntax highlighting for Icon
Icon appears in the Quine Relay project
See also: (9 related languages) SNOBOL, Algol, Python, Unicon, C, Pascal, Java, Smalltalk, CLU
1 PLDB concepts link to Icon: Unicon

Example from Riju:

procedure main ()
    write("Hello, world!")
end

Example from hello-world:

procedure main()
    write("Hello World");
end

Example from the Hello World Collection:

# Hello world in Icon (http://www.cs.arizona.edu/icon/)

procedure main()
    write("Hello world")
end

Example from Wikipedia:

procedure main()
     s := "Mon Dec 8"
     s ? write(Mdate() | "not a valid date")
 end
 # Define a matching function that returns
 # a string that matches a day month dayofmonth
 procedure Mdate()
 # Define some initial values
 static dates
 static days
 initial {
        days := ["Mon","Tue","Wed","Thr","Fri","Sat","Sun"]
        dates := ["Jan","Feb","Mar","Apr","May","Jun",
                  "Jul","Aug","Sep","Oct","Nov","Dec"]
 }
 every suspend   (retval <-  tab(match(!days)) ||     # Match a day
                             =" " ||                  # Followed by a blank
                             tab(match(!dates)) ||    # Followed by the month
                             =" " ||                  # Followed by a blank
                             matchdigits(2)           # Followed by at least 2 digits
                 ) &
                 (=" " | pos(0) ) &                   # Either a blank or the end of the string
                 retval                               # And finally return the string
 end
 # Matching function that returns a string of n digits
 procedure matchdigits(n)
     suspend (v := tab(many(&digits)) & *v <= n) & v
 end

Language features

Feature	Supported	Example	Token
Integers	✓	# \b([+-]?[0-9]+[KMGTPkmgtp]?)\b
Floats	✓	# [+-]?[0-9]\.([0-9])([Ee][+-]?[0-9]*)?
Hexadecimals	✓	# \b([+-]?([2-9]\|[12][0-9]\|3[0-6])[rR][0-9a-zA-Z]+)\b
Strings	✓	"Hello world"	"
Print() Debugging	✓		write
Comments	✓	# A comment
Line Comments	✓	# A comment	#
Semantic Indentation	X