APL (programming language): Difference between revisions

{{Distinguish|Address (programming language)}}

| website = {{url|https://aplwiki.com/}}

'''APL''' (named after the book ''A Programming Language'')<ref name="aplbook">{{Cite Q|Q105954505|url=https://www.softwarepreservation.org/projects/apl/Books/APROGRAMMING%20LANGUAGE|access-date=2023-08-06}}</ref> is a [[programming language]] developed in the 1960s by [[Kenneth E. Iverson]]. Its central datatype is the [[Array data type#Multi-dimensional arrays|multidimensional array]]. It uses a large range of [[APL syntax and symbols|special graphic symbols]]<ref>{{cite journal |last1=McIntyre |first1=Donald B. |title=Language as an Intellectual Tool: From Hieroglyphics to APL |journal=IBM Systems Journal |date=1991 |volume=30 |issue=4 |pages=554–581 |doi=10.1147/sj.304.0554 |url=http://domino.research.ibm.com/tchjr/journalindex.nsf/e90fc5d047e64ebf85256bc80066919c/9c834f5a16efa82085256bfa00685c72!OpenDocument |access-date=January 9, 2015|archive-url=https://web.archive.org/web/20160304051735/http://domino.research.ibm.com/tchjr/journalindex.nsf/e90fc5d047e64ebf85256bc80066919c/9c834f5a16efa82085256bfa00685c72!OpenDocument|archive-date=March 4, 2016|url-status=dead|url-access=subscription }}</ref> to represent most functions and operators, leading to very concise code. It has been an important influence on the development of concept modeling, [[spreadsheet]]s, [[functional programming]],<ref>{{cite web |url=http://awards.acm.org/citation.cfm?id=0703524&srt=all&aw=140&ao=AMTURING |archive-url=https://web.archive.org/web/20080212043802/https://awards.acm.org/citation.cfm?id=0703524&srt=all&aw=140&ao=AMTURING |archive-date=February 12, 2008 |title=ACM Award Citation&nbsp;– John Backus |publisher=Awards.acm.org |date= 1977 |access-date=February 3, 2010}}</ref> and computer math packages.<ref name="mworks"/> It has also inspired several other programming languages.<ref name="jinsp"/><ref name="kinsp"/>

Iverson also used his notation in a draft of the chapter ''A Programming Language'', written for a book he was writing with [[Fred Brooks]], ''Automatic Data Processing'', which would be published in 1963.<ref>Iverson, Kenneth E., [http://www.softwarepreservation.org/projects/apl/Books/Iverson-AutomaticDataProcessing-bilevel.pdf/view "Automatic Data Processing: Chapter 6: A programming language"] {{webarchive|url=https://web.archive.org/web/20090604091847/http://www.softwarepreservation.org/projects/apl/Books/Iverson-AutomaticDataProcessing-bilevel.pdf/view |date=June 4, 2009}}, 1960, Draft copy for Brooks and Iverson 1963 book, ''Automatic Data Processing''.</ref><ref>[[Fred Brooks|Brooks, Fred]]; Iverson, Kenneth, (1963), ''Automatic Data Processing'', John Wiley & Sons Inc.</ref>

In 1973–1974, Patrick E. Hagerty directed the implementation of the University of Maryland APL interpreter for the 1100 line of the Sperry [[UNIVAC 1100/2200 series]] mainframe computers.<ref>{{cite report |last1=Minker |first1=Jack |title=Beginning of Computing and Computer Sciences at the University of Maryland |url=http://www.cs.umd.edu/department/dept-history/minker-report.pdf |publisher=University of Maryland |access-date=May 23, 2011 |section=2.3.4 Computer Software Developments in the CSC, 1962–1973 |page=38 |date=January 2004 |archive-url= https://web.archive.org/web/20110610064807/http://www.cs.umd.edu/department/dept-history/minker-report.pdf |archive-date= June 10, 2011}}</ref> In 1974, student Alan Stebbens was assigned the task of implementing an internal function.<ref>{{cite web |last1=Stebbens |first1=Alan |title=How it all began |url=http://lathwellproductions.ca/wordpress/film |access-date=2011-05-22 |archive-url=https://web.archive.org/web/20160304000314/http://lathwellproductions.ca/wordpress/film |archive-date=2016-03-04 |url-status=dead}}</ref> Xerox APL was available from June 1975 for Xerox 560 and Sigma 6, 7, and 9 mainframes running [[Universal Time-Sharing System#CP-V|CP-V]] and for [[Honeywell CP-6]].<ref>{{cite web |title=Xerox APL Language and Operations Reference Manual |url=http://www.softwarepreservation.org/projects/apl/Books/197506_Xerox%20APL%20Language%20and%20Operations%20Reference%20Manual_90131C.pdf |archive-url=https://ghostarchive.org/archive/20221009/http://www.softwarepreservation.org/projects/apl/Books/197506_Xerox%20APL%20Language%20and%20Operations%20Reference%20Manual_90131C.pdf |archive-date=2022-10-09 |url-status=live}}</ref>

On microcomputers, which became available from the mid-1970s onwards, [[BASIC]] became the dominant programming language.<ref>{{cite magazine|url=https://time.com/69316/basic/|title=Fifty Years of BASIC, the Programming Language That Made Computers Personal|date=April 29, 2014|magazine=[[Time (magazine)|Time]] |access-date=April 29, 2018}}</ref> Nevertheless, some microcomputers provided APL instead – the first being the [[Intel 8008]]-based [[MCM/70]] which was released in 1974<ref>{{cite web|url=http://www.old-computers.com/museum/computer.asp?c=346 |title=MCM Computers M70/M700|website=old-computers.com|access-date=April 8, 2018 |archive-url=https://web.archive.org/web/20180403063223/http://www.old-computers.com/museum/computer.asp?c=346|archive-date=April 3, 2018|url-status=dead}}</ref><ref>{{cite book|last1=Stachniak|first1=Stachniak |date=2011|title=Inventing the PC: The MCM/70 Story|publisher=McGill Queens's University Press |isbn=978-0-7735-3852-8|url=https://books.google.com/books?id=cyWOA2FED7EC}}</ref> and which was primarily used in education.<ref>{{cite magazine |last1=Miller |first1=Michael |date=December 17, 2014 |title=PCs That Paved the Way for the Altair |url=http://uk.pcmag.com/opinion/38348/opinion/pcs-that-paved-the-way-for-the-altair |magazine=[[PC Magazine]]|publisher=Ziff Davis |access-date=April 29, 2018}}</ref> Another machine of this time was the [[VideoBrain Family Computer]], released in 1977, which was supplied with its dialect of APL called APL/S.<ref>[https://books.google.com/books?id=OQEAAAAAMBAJ&q=videobrain+family+computer+apl%2Fs&pg=PA133/s "VideoBrain Family Computer"], ''[[Popular Science]]'', November 1978, advertisement.</ref>

In 1976, Bill Gates claimed in his [[Open Letter to Hobbyists]] that [[Microsoft Corporation]] was implementing APL for the [[Intel 8080]] and [[Motorola 6800]] but had "very little incentive to make [it] available to hobbyists" because of [[software piracy]].<ref>{{cite magazine |last1=Gates |first1=Bill |date=January 31, 1976 |title=An Open Letter to Hobbyists |magazine=[[Homebrew Computer Club]] Newsletter |url=http://www.digibarn.com/collections/newsletters/homebrew/V2_01/index.html |access-date=April 29, 2018}}</ref> It was never released.

Suppose that {{code|X}} is an array of numbers. Then {{code|(+/X)÷⍴X}} gives its average. Reading ''right-to-left'', {{code|⍴X}} gives the number of elements in X, and since {{code|÷}} is a dyadic operator, the term to its left is required as well. It is surrounded by parentheses since otherwise X would be taken (so that the summation would be of {{code|X÷⍴X}}—each element of X divided by the number of elements in X), and {{code|+/X}} gives the sum of the elements of X. Building on this, the following expression computes [[standard deviation]]: {{sxhl|2=apl|((+/((X - (+/X)÷⍴X)*2))÷⍴X)*0.5}}

<p>Then one day Adin Falkoff walked into Ken's office and wrote "A Programming Language" on the board, and underneath it the acronym "APL". Thus it was born. It was just a week or so after this that Eric Iverson asked me his question, at a time when the name hadn't yet found its way the thirteen miles up the Taconic Parkway from IBM Research to IBM Mohansic.</p>|author=[[Eugene McDonnell]]|source=<ref>McDonnell, E.E. The [https://code.jsoftware.com/wiki/Doc/A_Source_Book_in_APL#origins introduction to ''A Source Book in APL''], APL Press, 1981. ([http://www.softwarepreservation.org/projects/apl/Papers/ASourceBookInAPL/view full book scan])</ref>}}

APL is well suited to [[image manipulation]] and [[computer animation]], where graphic transformations can be encoded as matrix multiplications. One of the first commercial computer graphics houses, [[Digital Effects (studio)|Digital Effects]], produced an APL graphics product named ''Visions'', which was used to create television commercials and animation for the 1982 film ''[[Tron]]''.<ref>{{cite book |last1=Magnenat-Thalmann |first1=Nadia |last2=Thalmann |first2=Daniel |date=1985 |title=Computer Animation Theory and Practice |url=https://books.google.com/books?id=neGoCAAAQBAJ&pg=PA38 |publisher=[[Springer-Verlag]] |page=38 |isbn=9784431684336 |quote=[[Digital Effects]] is another production house that worked on Tron. They used a laser-scanning system to digitize, store and reproduce images. Judson Rosebush, president of Digital Effects, is the primary designer of APL VISION and FORTRAN VISION, two computer animation packages that are currently used. |access-date=April 3, 2018}}</ref> Latterly, the [https://stormwind.fi/en/ Stormwind] [[Simulation video game|boating simulator]] uses APL to implement its core logic, its interfacing to the rendering pipeline middleware and a major part of its [[physics engine]].<ref>{{cite web |url=https://www.optima-systems.co.uk/stormwind-simulator-dyalog-16 |title=Stormwind Simulator at Dyalog '16 |last1=Gutsell |first1=Sam |date=October 17, 2017 |website=www.optima-systems.co.uk |publisher=Optima Systems |access-date=April 3, 2018 |quote=Stormwind is a [3D boating simulator] that has gained a huge amount of interest in the APL community.}}</ref>

York APL<ref name="YorkAPL">{{cite web |url=https://www.softwarepreservation.org/projects/apl/Books/YorkAPL |title=York APL}}</ref> was developed at the [[York University]], Ontario around 1968, running on IBM 360 mainframes. One notable difference between it and APL\360 was that it defined the "shape" (ρ) of a scalar as 1 whereas APL\360 defined it as the more mathematically correct 0 — this made it easier to write functions that acted the same with scalars and vectors.

APL is traditionally an [[interpreted language]], having language characteristics such as [[Strong and weak typing|weak variable typing]] not well suited to [[compiler|compilation]].<ref>{{cite book |last1=Budd |first1=Timothy |title=An APL Compiler |publisher=Springer-Verlag |year=1988 |isbn=978-0-387-96643-4 |url=https://books.google.com/books?id=rTb2BwAAQBAJ&pg=PA1}}</ref> However, with arrays as its core data structure<ref>{{cite web |title=What is APL? |website=www.sigapl.org |publisher=SIGAPL |url=http://www.sigapl.org/about.php |access-date=January 20, 2015}}</ref> it provides opportunities for performance gains through [[Data parallelism|parallelism]],<ref>{{cite book |last1=Ju |first1=Dz-Ching |last2=Ching |first2=Wai-Mee |title=Proceedings of the third ACM SIGPLAN symposium on Principles and practice of parallel programming |chapter=Exploitation of APL data parallelism on a shared-memory MIMD machine |date=1991 |volume=26 |issue=7 |pages=61–72 |doi=10.1145/109625.109633 |isbn=0-89791-390-6 |s2cid=8584353}}</ref> [[parallel computing]],<ref>{{cite web |last1=Hsu |first1=Aaron W. |last2=Bowman |first2=William J. |title=Revisiting APL in the Modern Era |url=http://www.cs.princeton.edu/~dpw/obt/abstracts/obt12_submission_11.pdf |access-date=January 20, 2015 |archive-url=https://ghostarchive.org/archive/20221009/http://www.cs.princeton.edu/~dpw/obt/abstracts/obt12_submission_11.pdf |archive-date=2022-10-09 |url-status=live |website=www.cs.princeton.edu}}</ref><ref>{{cite journal |last1=Ching |first1=W.-M. |last2=Ju |first2=D. |title=Execution of automatically parallelized APL programs on RP3 |journal=IBM Journal of Research & Development |date=1991 |volume=35 |issue=5/6 |pages=767–777 |url=http://domino.research.ibm.com/tchjr/journalindex.nsf/c469af92ea9eceac85256bd50048567c/f892e104dfc4d0fd85256bfa0067fb42!OpenDocument |access-date=January 20, 2015 |doi=10.1147/rd.355.0767 |archive-date=March 3, 2016 |archive-url=https://web.archive.org/web/20160303231727/http://domino.research.ibm.com/tchjr/journalindex.nsf/c469af92ea9eceac85256bd50048567c/f892e104dfc4d0fd85256bfa0067fb42!OpenDocument |url-status=dead|url-access=subscription }}</ref> [[Massively parallel (computing)|massively parallel]] applications,<ref>{{cite journal |last1=Blelloch |first1=Guy E. |last2=Sabot |first2=Gary W. |title=Compiling Collection-Oriented Languages onto Massively Parallel Computers |journal=Journal of Parallel and Distributed Computing |volume=8 |issue=2 |citeseerx=10.1.1.51.5088 |pages=119–134 |quote=Collection oriented languages include APL, APL2 |year=1990 |doi=10.1016/0743-7315(90)90087-6}}</ref><ref>{{cite web |last1=Jendrsczok |first1=Johannes |last2=Hoffmann |first2=Rolf |last3=Ediger |first3=Patrick |last4=Keller |first4=Jörg |title=Implementing APL-like data parallel functions on a GCA machine |pages=1–6 |url=https://www.fernuni-hagen.de/imperia/md/content/fakultaetfuermathematikundinformatik/pv/97-08/papergca_09_1_.pdf |website=www.fernuni-hagen.de |access-date=January 22, 2015 |quote=GCA – Global Cellular Automation. Inherently massively parallel. 'APL has been chosen because of the ability to express matrix and vector' structures. |archive-url=https://web.archive.org/web/20150122211834/https://www.fernuni-hagen.de/imperia/md/content/fakultaetfuermathematikundinformatik/pv/97-08/papergca_09_1_.pdf |archive-date=January 22, 2015 |url-status=dead}}</ref> and [[very-large-scale integration]] (VLSI),<ref>{{cite book |last1=Brenner |first1=Norman |chapter=VLSI circuit design using APL with fortran subroutines |title=Proceedings of the international conference on APL - APL '84 |date=1984 |volume=14 |issue=4 |pages=77–79 |doi=10.1145/800058.801079 |isbn=0-89791-137-7 |quote=APL for interactiveness and ease of coding |s2cid=30863491}}<br/>{{*}}{{cite book |last1=Brenner |first1=Norman |date=1984 |title=Proceedings of the international conference on APL – APL '84 |chapter=VLSI circuit design using APL with fortran subroutines |publisher=ACM SIGAPL |isbn=978-0897911375}}</ref><ref>{{cite book |doi=10.1109/PACRIM.1989.48437 |quote=VLSI module generators are described. APL and C, as examples of interpreted and compiled languages, can be interfaced to an advanced graphics display. |chapter=Towards a graphics/Procedural environment for constructing VLSI module generators |title=Conference Proceeding IEEE Pacific Rim Conference on Communications, Computers and Signal Processing |pages=606–611 |year=1989 |last1=Gamble |first1=D.J. |last2=Hobson |first2=R.F. |s2cid=7921438}}</ref> and from the outset APL has been regarded as a high-performance language<ref>{{cite journal |last1=Lee |first1=Robert S. |title=Two Implementations of APL |journal=PC Magazine |date=1983 |volume=2 |issue=5 |page=379 |url=https://books.google.com/books?id=qURs4j9vKn4C&q=%22IBM%20APL%27s%20fast%20execution%22&pg=PA379 |access-date=January 20, 2015}}</ref> – for example, it was noted for the speed with which it could perform complicated matrix operations "because it operates on arrays and performs operations like matrix inversion internally".<ref>{{cite web |website=MARTHA and LLAMA |title=The APL Computer Language |url=http://marthallama.org/apl/ |access-date=January 20, 2015 |archive-date=February 13, 2015 |archive-url=https://web.archive.org/web/20150213004709/http://marthallama.org/apl/ |url-status=dead}}</ref>

* [https://web.archive.org/web/20141027152546/http://www.softwarepreservation.org/projects/apl/Books/APROGRAMMING%20LANGUAGE/view ''A Programming Language''] by [[Kenneth E. Iverson]]

* [https://www.softwarepreservation.org/projects/apl/Papers/197201_APL%20In%20Exposition_320-3010.pdf/view ''APL in Exposition''] by [[Kenneth E. Iverson]]

* {{YouTube|id=8kUQWuK1L4w|title=The Origins of APL}} – a 1974 talk show style interview with the original developers of APL.

* {{YouTube|id=_DTpQ4Kk2wA|title=APL demonstration}} – a 1975 live demonstration of APL by [[Robert Spence (engineer)|Professor Bob Spence]], [[Imperial College London]].

* {{YouTube|id=a9xAKttWgP4|title=Conway's Game Of Life in APL}} – a 2009 tutorial by John Scholes of Dyalog Ltd. which implements [[Conway's Game of Life]] in a single line of APL.

* {{YouTube|id=ra_JyBCI4Xg|title=50 Years of APL}} – a 2009 introduction to APL by Graeme Robertson.