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{{Infobox array language
{{Infobox array language
| logo                  = [[File:Jblue.png]]
| file ext              = .ijs
| file ext              = .ijs
| array model            = [[Flat array model|flat]] with [[Box|boxes]]
| array model            = [[Flat array model|flat]] with [[Box|boxes]]
| index origin          = 0
| index origin          = 0
| function styles        = explicit, [[tacit]]
| function styles        = [[Anonymous function|explicit]], [[tacit]]
| numeric types          = 64-bit integer, complex float, [[extended integer]], [[rational]]
| numeric types          = 64-bit integer, [[complex]] float, [[extended integer]], [[rational]]
| unicode support        = full; distinct byte and code point types
| unicode support        = full; distinct byte and code point types
| released              = 1990
| released              = 1990
| developer              = [[JSoftware]] ([[Kenneth E. Iverson]], [[Roger Hui]])
| developer              = [[Jsoftware]] ([[Ken Iverson]], [[Roger Hui]])
| latest release version = J807 / 2018-10-08
| latest release version = j903 / 2021-12-17
| influenced by          = [[SHARP APL]], [[Rationalized APL]], [https://en.wikipedia.org/wiki/FP_(programming_language) FP], [https://en.wikipedia.org/wiki/FL_(programming_language) FL]
| influenced by          = [[SAX]], [[Rationalized APL]]
| influenced            = [[Dyalog APL]], [[I]]
| influenced            = [[Dyalog APL]], [[NARS2000]], [[I]], [[BQN]]
| implementation language= [[wikipedia:C (programming language)|C]]
| source                = [https://github.com/jsoftware/jsource GitHub]
| platforms              = x86, x86_64
| platforms              = x86, x86_64
| operating systems      = Windows, Linux, macOS
| operating systems      = Windows, Linux, macOS
| license                = [https://en.wikipedia.org/wiki/GNU_General_Public_License GPLv3]
| license                = [[wikipedia:GNU General Public License|GPLv3]]
| website                = [https://www.jsoftware.com/ www.jsoftware.com]
| website                = [https://www.jsoftware.com/ www.jsoftware.com]
| forum                  = [https://code.jsoftware.com/wiki/System/Forums multiple]
| download              = [https://code.jsoftware.com/wiki/System/Installation System/Installation]
| download              = [https://code.jsoftware.com/wiki/System/Installation System/Installation]
| documentation          = [https://www.jsoftware.com/help/dictionary/contents.htm Dictionary], [https://code.jsoftware.com/wiki/NuVoc NuVoc]
| documentation          = [https://www.jsoftware.com/help/dictionary/contents.htm Dictionary], [https://code.jsoftware.com/wiki/NuVoc NuVoc]
| run online            = [https://joebo.github.io/j-emscripten/ Emscripten], [https://jsoftware.github.io/j-playground/bin/html/ J playground]
}}
}}
'''J''' is an array language loosely following the [[SHARP APL]] tradition which uses [[wikipedia:ASCII|ASCII]] characters for primitive functionality and builds in [[leading axis theory]] and [[tacit programming]] as foundational design principles. J discards backwards compatibility with older APLs in order to simplify and regularize its syntax, redesign primitives to work on leading axes, and disentangle [[reduction]] from [[scan]]s and [[windowed reduction]]s (yielding the [[Prefix operator|prefix]] and [[infix operator]]s). However, J concepts such as [[function train]]s and the [[Indices]] function have been adopted by later APLs such as [[NARS2000]], [[Dyalog APL]], and [[dzaima/APL]]. J breaks the APL convention of writing primitives with a single glyph: instead, they are spelled with a single ASCII character possibly followed by one or two periods (<source lang=j inline>.</source>) or colons (<source lang=j inline>:</source>). It is also notable for its use of terms from English grammar to describe the language. For example, [[function]]s are called "verbs" while arrays are called "nouns".


The '''J''' programming language combines an ASCII encoding of APL as embodied by [[SHARP APL]] with functional techniques developed by [https://en.wikipedia.org/wiki/John_Backus John Backus] for the [https://en.wikipedia.org/wiki/FP_(programming_language) FP] and [https://en.wikipedia.org/wiki/FL_(programming_language) FL] languages. J is characterized by its use of [[leading axis theory]] as a foundational design principle and its [[tacit programming]] capabilities. [[Function trains]] are a key J feature and were later adopted by [[Dyalog APL]]. J's primitives consist of a single ASCII character possibly followed by one or two periods (<source lang=j inline>.</source>) or colons (<source lang=j inline>:</source>). It is also notable for its use of terms from English grammar to describe the language. For example, [[functions]] are called "verbs" while arrays are called "nouns".
== History ==


{{APL programming language}}
J was initially designed primarily by [[Ken Iverson]] and [[Roger Hui]], with input from [[Arthur Whitney]] and [[Eric Iverson]]. Ken had been considering a new language based on [[A Dictionary of APL]] but without the backwards compatibility constraints of APL and the custom character set (which was a major technical issue at the time). In "A Personal View of APL"<ref name="personal">[[Ken Iverson|Iverson, K.E.]] [https://www.jsoftware.com/papers/APLPersonalView.htm "A Personal View of APL"]. IBM Systems Journal, Volume 30, Number 4. 1991-12.</ref> he gives the following as the most important goals for a new language:
{{quote|
* Is available as “shareware”, and is inexpensive enough to be acquired by students as well as by schools
* Can be printed on standard printers
* Runs on a wide variety of computers
* Provides the simplicity and the generality of the latest thinking in APL}}
 
Iverson's phrase "the latest thinking in APL" refers to two major breakthroughs made that decade: the invention of the [[Rank operator]] by [[Arthur Whitney]] in 1982 and subsequent development of [[leading axis theory]], and the invention of [[function train]]s by Iverson and [[Eugene McDonnell]] in 1988.
 
In the summer of 1989 Whitney visited Iverson, who discussed with Whitney his plans for a new array language. Whitney wrote a one-page prototype for the language in a single afternoon using [[wikipedia:C (programming language)|C]]. Iverson shared the program with [[Roger Hui]], who began working on J on August 27 and quickly produced a more complete prototype.<ref name="personal"/><ref>[[Roger Hui|Hui, Roger]]. [https://code.jsoftware.com/wiki/Essays/Incunabulum "Incunabulum"]. From ''An Implementation of J'', Appendix A: Incunabulum, 1992-01-27.</ref><ref name>McIntyre, Donald. [https://web.archive.org/web/20060410225556/http://elliscave.com/APL_J/rogerhui.htm "A Tribute to Roger Hui, presented at APL96"]. 1996.</ref> The name "J", chosen by Hui when saving the first source code file, is meaningless: in ''An Implementation of J'', Hui remarks "Why 'J'? It is easy to type."<ref>[[Roger Hui|Hui, Roger]]. [https://sblom.github.io/openj-core/ioj.htm ''An Implementation of J''] ([http://www.jsoftware.com/books/pdf/aioj.pdf pdf]), Preface. 1992-01-27.</ref> J was first presented by Hui and Iverson, including a live demo, at a meeting of the Toronto APLSIG in February 1990.<ref name="remembering">[[Roger Hui|Hui, Roger]]. [http://keiapl.org/rhui/remember.htm "Remembering Ken Iverson"]. 2004-11.</ref>
 
In 1990 Hui and Iverson joined Iverson Software Inc. (now [[Jsoftware]]), which had been founded that year by [[Eric Iverson]] to sell a [[SHARP APL]] product. Eric converted his SHARP [[session]] to use with J as Hui continued on the core language's implementation. The J language, including Eric's session environment, was first released at [[APL90]] in Copenhagen August 1990.<ref name="remembering"/>
 
== Versions ==
 
J has used two numbering systems. Releases prior to 1994 used a single decimal and the naming scheme "Version X.Y", while those after used two decimals and are called "Release X.YY", or "JXYY" as in "J807".
 
{|class=wikitable
! Version !! Date    !! Features
|-
| 2.0  || 1990-08-09 || (APL90)
|-
| 2.7  || 1990-10-22 || [[Rank operator|Rank]] with a function right operand, [[Under]]
|-
| 2.8  || 1990-11-15 ||
|-
| 2.9  || 1991-02-15 || Monadic <source lang=j inline>+:</source> (double), <source lang=j inline>-:</source> (halve), <source lang=j inline>*:</source> (square), dyadic <source lang=j inline>":</source> ([[Format]]), constant functions <source lang=j inline>0:</source> and <source lang=j inline>1:</source>
|-
| 3.0  || 1991-03-17 || Changes to spellings, [[Reverse]] with [[Variant]] to specify [[fill]]
|-
| 3.1  || 1991-05-17 || [[Determinant]] (<source lang=j inline>.</source>)
|-
| 3.2  || 1991-06-02 || <source lang=j inline>,.</source> for ravel items (like [[Table]]) and append lists, <source lang=j inline>;</source> for [[Raze]] and [[Link]], <source lang=j inline>@.</source> for agenda, non-[[close composition]]s
|-
| 3.3  || 1991-06-25 || Dyadic <source lang=j inline>,.</source> changed to append items, more types of trains
|-
| 3.4  || 1991-07-15 || <source lang=j inline>NB.</source> for comments
|-
| 4.0  || 1991-11-23 || Monadic <source lang=j inline>+.</source> and <source lang=j inline>*.</source> for complex components and phase/magnitude with <source lang=j inline>j.</source> and <source lang=j inline>r.</source> to recombine, <source lang=j inline>^:_</source> for power limit
|-
| 4.1  || 1992-02-02 || <source lang=j inline>^!.p</source> for rising/falling factorials
|-
| 4.2  || 1992-03-19 ||
|-
| 5.0  || 1992-06-22 || [[Variant]] to specify [[comparison tolerance]] and [[fill]] for [[Take]]
|-
| 5.1  || 1992-07-28 || <source lang=j inline>f.</source> to expand a tacit function containing names, constant functions <source lang=j inline>2:</source> to <source lang=j inline>9:</source>
|-
| 5.1a || 1992-08-11 ||
|-
| 6.0  || 1992-10-24 || Error handling with <source lang=j inline>::</source>, additional [[system function]]s
|-
| 6.1  || 1992-11-26 || [[Amend]] operator <source lang=j inline>}</source>
|-
| 6.2  || 1992-12-20 || Derivative operator <source lang=j inline>D.</source>
|-
| 7.0  || 1993-11-14 || [[wikipedia:Taylor series|Taylor series]] operators <source lang=j inline>t.</source> and <source lang=j inline>T.</source>
|}
 
{|class=wikitable
! Release !! Date    !! Features
|-
| 2.01 || 1994-09-01 || [[Control structure]]s, many additional [[system function]]s
|-
| 2.03 || 1994-09-21 ||
|-
| 2.04 || 1994-11-28 ||
|-
| 2.05 || 1995-02-26 || Additional [[inverse]]s, [[primitive array]] <source lang=j inline>a:</source> ("ace")
|-
| 2.06 || 1995-05-30 || More [[inverse]]s, hypergeometric operator <source lang=j inline>H.</source>, and prime functions <source lang=j inline>p.</source>, <source lang=j inline>p:</source>, and <source lang=j inline>q:</source>
|-
| 3.01 || 1996-01-16 || Repeatable [[Roll]]/[[Deal]] <source lang=j inline>?.</source>, [[Depth]] <source lang=j inline>L.</source> and [[Depth operator]] <source lang=j inline>L:</source>, [[total array ordering]]
|-
| 3.02 || 1996-06-24 || [[Pick]] variant <source lang=j inline>{::</source>, [[extended precision]] types
|-
| 3.03 || 1996-12-13 || [[Multiple assignment]] using a string target
|-
| 3.04 || 1997-05-19 || More operators with gerund operands, <source lang=j inline>for.</source> and <source lang=j inline>select.</source> [[control structure]]s
|-
| 3.05 || 1997-09-27 || Extended dyad <source lang=j inline>q:</source> ([[Factor]]) to take a negative left argument
|-
| 4.01 || 1998-03-22 || [[Find]] (<source lang=j inline>E.</source>) and [[Index of Last]] (<source lang=j inline>i:</source>)
|-
| 4.02 || 1998-11-07 || Symmetric range monad (<source lang=j inline>i:</source>), infinite left arguments to [[Take]]
|-
| 4.03 || 1999-04-21 ||
|-
| 4.04 || 2000-01-02 || [[Sparse array]] support
|-
| 4.05 || 2000-09-05 || [[Comparison tolerance]] for [[Key]]
|-
| 4.06 || 2001-05-09 || <source lang=j inline>assert.</source> and <source lang=j inline>throw.</source>, Symbols (<source lang=j inline>s:</source>) and Unicode (<source lang=j inline>u:</source>), multiple axes in [[Cut]] operator
|-
| 5.01 || 2002-09-10 || Non-[[Close composition|close]] [[Under]] <source lang=j inline>&.:</source>, Bitwise Operations (<source lang=j inline>b.</source>), Polynomial Derivative (<source lang=j inline>p..</source>), Head (<source lang=j inline>{.</source>) and Tail (<source lang=j inline>{:</source>) allow [[empty]] arguments
|-
| 5.02 || 2003-05-21 ||
|-
| 5.03 || 2004-03-19 || [[Indices]] (<source lang=j inline>I.</source>), Sequential Machine (<source lang=j inline>;:</source>)
|-
| 5.04 || 2005-03-18 || J64 (64-bit version) introduced, boxed right argument for [[Power operator]], [[scalar extension]] for left argument of [[Cut]] (<source lang=j inline>;.</source>)
|-
| 6.01 || 2006-07-21 || Noun left arguments in trains (<source lang=j inline>N0 V1 V2</source>), dots removed from explicit argument names (<source lang=j inline>y.</source> to <source lang=j inline>y</source>, etc.), [[Interval Index]] (<source lang=j inline>I.</source>)
|-
| 6.02 || 2008-02-29 || [[Index Of]] (<source lang=j inline>i.</source>) extended to allow unmatched cell shapes, Memoize adverb (<source lang=j inline>M.</source>)
|-
| 7.01 || 2010-08-05 || GTK IDE
|-
| 7.02 ||            ||
|-
| 8.01 || 2014-02    || Qt IDE
|-
| 8.02 || 2014-08-02 || Qt IDE improved
|-
| 8.03 || 2014-12-09 || Native read/write of jpeg and png images
|-
| 8.04 || 2016-01-04 ||
|-
| 8.05 || 2016-12-19 || Improved UTF-8 handling, memory allocator rewritten with more in-place argument usage
|-
| 8.06 || 2017-11-12 || Allow array right operands to [[Atop]] and Adverse (<source lang=j inline>::</source>), treating as constant functions, improved [[Vector instructions|vector instruction]] usage
|-
| 8.07 || 2018-10-08 || Removed support for dot-style explicit arguments (e.g. <source lang=j inline>y.</source>)
|-
| 9.01 || 2019-12-15 || Iteration primitives <source lang=j inline>F..</source>, <source lang=j inline>F.:</source>, <source lang=j inline>F.</source>, <source lang=j inline>F:.</source>, <source lang=j inline>F::</source>, <source lang=j inline>F:</source>; Remove calculus operators <source lang=j inline>d.</source>, <source lang=j inline>D.</source>, <source lang=j inline>D:</source>, <source lang=j inline>t.</source>, <source lang=j inline>t:</source>, <source lang=j inline>T.</source>, <source lang=j inline>..</source>, <source lang=j inline>.:</source>; <source lang=j inline>gerund"r</source>
|-
| 9.02 || 2020-12-13 || "Direct definition" syntax for explicit functions, special semidual form <source lang=j inline>u&.:(a:`v)</source> added, minor incompatible changes
|-
| 9.03 || 2021-12-17 || Modifier trains and other combinations, foreigns to enable nameref caching, Kahan summation with <source lang=j inline>+/!.0</source>
|}
 
== References ==
 
<references />
{{APL dialects}}[[Category:Array languages]][[Category:Flat array languages]][[Category:Leading axis languages]][[Category:Languages with tacit programming]][[Category:ASCII languages]]

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