Charity (programming language)

Charity

Paradigm(s)	pure functional
Appeared in	1992[1]
Developer	The Charity Development Group
Preview release	1.99.1 (beta)[2] (August 2000; 11 years ago (2000-08))
OS	Linux, SunOS, Windows 9x, Windows NT[2]
License	Non-commercial use only[3]
Website	pll.cpsc.ucalgary.ca/charity1/www/home.html

Charity is an experimental purely functional programming language, developed at the University of Calgary. Based on ideas by Hagino Tatsuya, it is completely grounded in category theory.

Disregarding interactions with the outside world, all Charity programs are guaranteed to terminate. This means that the language is not Turing-complete. Nevertheless, it is capable of expressing the Ackermann function, which makes it more expressive than primitive recursion.

The language allows ordinary recursive data types, such as might be found in ML, which are required to be finite, and corecursive data types, which are allowed to be potentially infinite. The control structure for operating on recursive data types is primitive recursion or catamorphism, and the control structure for corecursive data types is primitive co-recursion or anamorphism. Neither control structure can operate over the other kind of data, so all catamorphisms terminate and all anamorphisms are productive.

References

1. ^ Cockett, Robin; Fukushima, Tom (May 27, 1992). "About Charity". Yellow Series Report (Calgary, Alberta, Canada: Department of Computer Science, University of Calgary) (92/480/18). ftp://ftp.cpsc.ucalgary.ca/pub/projects/charity/literature/papers_and_reports/about_charity.ps. 
2. ^ ^{a b} "Download The Charity System". CHARITY. The Charity Development Group. October 2000. http://pll.cpsc.ucalgary.ca/charity1/www/system.html. Retrieved 2011-03-06. 
3. ^ "License Conditions". CHARITY. The Charity Development Group. September 1997. http://pll.cpsc.ucalgary.ca/charity1/www/license.html. Retrieved 2011-03-06. 

External links

• Official website