Joy (programming language): Difference between revisions

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The '''Joy programming language''' in [[computer science]] is a [[purely functional programming language]] that was produced by Manfred von Thun of [[La Trobe University]] in [[Melbourne]], [[Australia]]. Joy is based on composition of functions rather than [[lambda calculus]]. It has turned out to have many similarities to [[Forth (programming language)|Forth]], due not to design but to an independent evolution and convergence. It was also inspired by the [[Function-level programming|function-level programming style]] of [[John Backus]]'s [[FP (programming language)|FP]].<ref>{{cite web|title=A Conversation with Manfred von Thun|author=Manfred von Thun|url=http://www.nsl.com/papers/interview.htm|access-date=May 31, 2013|date=December 12, 2003|quote=" In the early 1980s I came across the famous Backus paper "Can programming be liberated from the von Neumann style," and I was immediately intrigued by the higher level of programming in his FP."}}</ref>

It has turned out to have many similarities to [[Forth (programming language)|Forth]], due not to design but to an independent evolution and convergence.{{Citation needed|date=October 2024}}

== How it worksOverview ==

Functions in Joy lack [[Parameter (computer science)|formal parameters]]. For example, a function that squares a numeric input can be expressed as follows:<ref>{{cite web|title=An informal tutorial on Joy |url=http://www.latrobe.edu.au/phimvt/joy/j01tut.html |url-status=dead |archive-url=https://web.archive.org/web/20111007030359/http://www.latrobe.edu.au/phimvt/joy/j01tut.html |archive-date=October 7, 2011 }}</ref>

DEFINE square == dup * .

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* The '''*''' operator pops two numbers off the stack and pushes their product.

So the square function makes a copy of the top element, and then multiplies the two top elements of the stack, leaving the square of the original top element at the top of the stack, with no need for a formal parameter. This makes Joy concise, as illustrated by this definition of [[quicksort]]:<ref>{{cite web|title=Sequence Library |url=http://www.latrobe.edu.au/phimvt/joy/seqlib.joy |url-status=dead |archive-url=https://web.archive.org/web/20111007030359/http://www.latrobe.edu.au/phimvt/joy/seqlib.joy |archive-date=October 7, 2011 }}</ref>

<pre><nowiki>

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[]

[uncons [>] split]

[swapd cons concat]

[enconcat]

binrec.

</nowiki></pre>

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* [http://www.kevinalbrecht.com/code/joy-mirror/index.html Joy homepage mirror]

* [https://github.com/Wodan58/Joy Joy source code] (GitHub-Archive)

* {{cite journal|first=Paul|last=Freneger|authorlink=Paul Freneger|title=The JOY of forth|journal=[[ACM SIGPLAN Notices]]|volume=38|issue=8|date=August 2003|url=http://portal.acm.org/citation.cfm?id=944579.944583 |pages=15–17 |doi=10.1145/944579.944583|url-access=subscription}}

* {{cite journal|first1=Manfred|last1=von Thun|authorlink1=Manfred von Tuhn|first2=Reuben|last2=Thomas|authorlink2=Reuben Thomas|title=Joy: Forth's Functional Cousin|journal=Proceedings of the 17th EuroForth Conference|url=http://www.complang.tuwien.ac.at/anton/euroforth/ef01/thomas01a.pdf|date=October 9, 2001}}

* {{Cite web| url = http://www.drdobbs.com/architecture-and-design/228701299 | author = Christopher Diggins | title = What is a Concatenative Language | date = December 31, 2008 | publisher = Dr. Dobbs | volume =33}}

* {{cite journal|first=Stevan|last=Apter|title=Functional Programming in Joy and K|journal=Vector|url=http://www.vector.org.uk/archive/v214/joy214.htm|access-date=2011-02-28|archive-url=https://web.archive.org/web/20080828115345/http://www.vector.org.uk/archive/v214/joy214.htm|archive-date=2008-08-28|url-status=dead}}

* [https://github.com/metazip/mjoy mjoy, an interpreter in Lazarus for drawings with turtle graphics] (Subset of Joy)

* [https://concatenative.org/wiki/view/Joy%20of%20Postfix Joy of Postfix Calculator App] (Subset of Joy)

[[Category:Programming languages]]