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'''Array notation''' is a way to write most [[array]]s literally, with no or minimal use of [[primitive function]]s, possibly over multiple code lines. While APL has had at least simple numeric [[ | '''Array notation''' is a way to write most [[array]]s literally, with no or minimal use of [[primitive function]]s, possibly over multiple code lines. While APL has had at least simple numeric [[strand notation]] since [[APL\360]], no major APL has implemented native support for an extended notation as of 2020. | ||
Medium-sized array constants are often needed in code. Due to the lack of a native multi-line notation, programmers have resorted to various ad-hoc methods of approximating such, usually at the cost of reduced [[readability]]. A very common technique is repeated [[concatenate|concatenation]]: | Medium-sized array constants are often needed in code. Due to the lack of a native multi-line notation, programmers have resorted to various ad-hoc methods of approximating such, usually at the cost of reduced [[readability]]. A very common technique is repeated [[concatenate|concatenation]]: | ||
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[[File:Nested Arrays System array notation.png|thumb|right|Array notation in [[NARS]].]] | [[File:Nested Arrays System array notation.png|thumb|right|Array notation in [[NARS]].]] | ||
=== 1981 === | === 1981 === | ||
When [[NARS]] introduced [[nested array theory]], the need for a way to represent complex structures was already recognised. Though a formal notation was never adopted, much less implemented, the NARS reference manual included round parentheses to delimit nested arrays.<ref>Carl M | When [[NARS]] introduced [[nested array theory]], the need for a way to represent complex structures was already recognised. Though a formal notation was never adopted, much less implemented, the NARS reference manual included round parentheses to delimit nested arrays.<ref>Cheney, Carl M. ''APL*PLUS Nested Arrays System'' (reference manual). [http://www.sudleyplace.com/APL/Nested%20Arrays%20System.pdf#page=7 1.1 What are nested arrays?] [[STSC]]. 1981.</ref> | ||
=== 2014 === | |||
At [[Dyalog '14]], [[Morten Kromberg]] said: | |||
:''The emphasis on using scripts to store source code means that it's probably time for us to come up with a notation for constants in the language so that in your script you can declare matrices and so on in a nice readable fashion.'' | |||
Although no concrete proposal was made at the time, he set the expectation of this being the subject of a presentation the following year.<ref>[[Morten Kromberg|Kromberg, Morten]]. [https://dyalog.tv/Dyalog14/?v=rRRyDWaU1fA Technical Road Map]. [[Dyalog '15]].</ref> | |||
=== 2015 === | === 2015 === | ||
At [[Dyalog '15]], Phil Last explained that he considered the lack of such a notation a big hole in APL notation and gave a suggestions for such a notation. He presented a model using square brackets to indicate collections of [[major cell]]s of [[rank]] 1 or higher, delimited by line breaks and/or [[diamond]]s, for example <source lang=apl inline>[1 2 3 ⋄ 4 5 6]</source> would be equivalent to <source lang=apl inline>2 3⍴1 2 3 4 5 6</source>. He also proposed that if the delimited expressions were [[assignment]]s, then the notation would instead declare members of an anonymous [[namespace]], for example for example <source lang=apl inline>[a←3 ⋄ b←6]</source>. He pointed out that this overloading of the symbols meant that the array notation could only represent constants, as allowing general expressions would lead to ambiguity. He also mentioned that doubled symbols or [[Unicode]] brackets could be used instead.<ref>Last, Phil. [https://dyalog.tv/Dyalog15/?v=9-HAvTMhYao APL Array Notation] ([https://www.dyalog.com/uploads/conference/dyalog15/presentations/U07_APL_Array_Notation.pdf transcript]). [[Dyalog '15]].</ref> | At [[Dyalog '15]], [[Phil Last]] explained that he considered the lack of such a notation a big hole in APL notation and gave a suggestions for such a notation. He presented a model using square brackets to indicate collections of [[major cell]]s of [[rank]] 1 or higher, delimited by line breaks and/or [[diamond]]s, for example <source lang=apl inline>[1 2 3 ⋄ 4 5 6]</source> would be equivalent to <source lang=apl inline>2 3⍴1 2 3 4 5 6</source>. He also proposed that if the delimited expressions were [[assignment]]s, then the notation would instead declare members of an anonymous [[namespace]], for example for example <source lang=apl inline>[a←3 ⋄ b←6]</source>. He pointed out that this overloading of the symbols meant that the array notation could only represent constants, as allowing general expressions would lead to ambiguity. He also mentioned that doubled symbols or [[Unicode]] brackets could be used instead.<ref>[[Phil Last|Last, Phil]]. [https://dyalog.tv/Dyalog15/?v=9-HAvTMhYao APL Array Notation] ([https://www.dyalog.com/uploads/conference/dyalog15/presentations/U07_APL_Array_Notation.pdf transcript]). [[Dyalog '15]].</ref> | ||
After the presentation, Phil Last had a conversation with [[Adám Brudzewsky]] who had recently joined [[Dyalog Ltd.]], the [[language developer|language developer]] of [[Dyalog APL]], and who was inspired to begin an internal Dyalog research project on the matter. Meanwhile, Acre Desktop, a project manager that Last co-develops, moved from storing APL items in [[component file]]s to storing them in text files, necessitating a literal notation for arrays, and his notation for arrays was adopted. Acre stores unscripted namespaces as directories, so the need for a literal namespace notation only arises when a namespace is an element in a larger array, something that is quite unlikely for application constants. | After the presentation, Phil Last had a conversation with [[Adám Brudzewsky]] who had recently joined [[Dyalog Ltd.]], the [[language developer|language developer]] of [[Dyalog APL]], and who was inspired to begin an internal Dyalog research project on the matter. Meanwhile, Acre Desktop, a project manager that Last co-develops, moved from storing APL items in [[component file]]s to storing them in text files, necessitating a literal notation for arrays, and his notation for arrays was adopted. Acre stores unscripted namespaces as directories, so the need for a literal namespace notation only arises when a namespace is an element in a larger array, something that is quite unlikely for application constants. | ||
=== 2016 === | |||
Phil Last published a more formal proposal in the [[Vector Journal]]. Again, the notation was only described as a serialisation format; not as an integral part of the language. He added escape sequences to [[string]]s, further distancing the notation from compatibility with existing APL code.<ref>Last, Phil. [http://archive.vector.org.uk/art10501450 A Notation for APL array Embedding and Serialization]. Vector Journal, Volume 26, number 4. [[British APL Association]]. 2016.</ref> | |||
[[File:D11 Literal Notation for Arrays and Namespaces - Summary of notations.png|thumb|right|Array notation at [[Dyalog '17]].]] | [[File:D11 Literal Notation for Arrays and Namespaces - Summary of notations.png|thumb|right|Array notation at [[Dyalog '17]].]] | ||
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The namespace notation remained as before, using round parentheses so the empty namespace could be written in a consistent manner, but he presented formalised scoping rules for the value expressions, namely that these would run in the surrounding namespace, but within their own scope, so any assignment done during such an expression. For example <source lang=apl inline>(a:b,b←1 2)</source> would neither populate the new namespace with a member <source lang=apl inline>b</source>, nor create such a variable in the global scope.<ref>Brudzewsky, Adám. [https://dyalog.tv/Dyalog18/?v=GAdQuOtPcfM Array Notation Mk III]. [[Dyalog '18]].</ref> Acre quickly adopted this notation. | The namespace notation remained as before, using round parentheses so the empty namespace could be written in a consistent manner, but he presented formalised scoping rules for the value expressions, namely that these would run in the surrounding namespace, but within their own scope, so any assignment done during such an expression. For example <source lang=apl inline>(a:b,b←1 2)</source> would neither populate the new namespace with a member <source lang=apl inline>b</source>, nor create such a variable in the global scope.<ref>Brudzewsky, Adám. [https://dyalog.tv/Dyalog18/?v=GAdQuOtPcfM Array Notation Mk III]. [[Dyalog '18]].</ref> Acre quickly adopted this notation. | ||
[[File:D09 Array Notation RC1 - Questions.png|thumb|right|Array notation at [[Dyalog '20]]]] | |||
===2020=== | ===2020=== | ||
In the spring of 2020, dzaima/APL adopted the proposed array notation with the exception of forcing the result of statements in square brackets to rank 1 or higher.<ref>Stack Exchange user [https://codegolf.stackexchange.com/users/59183/dzaima dzaima]. [https://github.com/dzaima/APL dzaima/APL]. Git commit "[https://github.com/dzaima/APL/commit/dfebe5de3699b2e3f838a60f72c6b9a9f66317e7 <source lang=apl inline>[1 2⋄3 4]</source>, <source lang=apl inline>⎕AV</source>,]". GitHub.</ref> | In the spring of 2020, [[dzaima/APL]] adopted the proposed array notation with the exception of forcing the result of statements in square brackets to rank 1 or higher.<ref>Stack Exchange user [https://codegolf.stackexchange.com/users/59183/dzaima dzaima]. [https://github.com/dzaima/APL dzaima/APL]. Git commit "[https://github.com/dzaima/APL/commit/dfebe5de3699b2e3f838a60f72c6b9a9f66317e7 <source lang=apl inline>[1 2⋄3 4]</source>, <source lang=apl inline>⎕AV</source>,]". GitHub.</ref> | ||
At [[Dyalog '20]], Adám Brudzewsky presented the notation as ''Release Candidate 1'' and showed how [[Dyalog APL 18.0]]'s updated version of [https://github.com/Dyalog/link/wiki Link] (a simple interface for using source code in text files, synchronising the file system and the [[workspace]]) includes experimental support the array notation, including a facility to use multi-line array notation inside functions. He estimated that [[Dyalog APL 20.0]] will include native interpreter support for the notation in 2022. | At [[Dyalog '20]], Adám Brudzewsky presented the notation as ''Release Candidate 1'' and showed how [[Dyalog APL 18.0]]'s updated version of [https://github.com/Dyalog/link/wiki Link] (a simple interface for using source code in text files, synchronising the file system and the [[workspace]]) includes experimental support the array notation, including a facility to use multi-line array notation inside functions. He estimated that [[Dyalog APL 20.0]] will include native interpreter support for the notation in 2022. | ||
== References == | == References == | ||
<references/> | <references/> | ||
{{APL syntax}}[[Category:APL syntax]][[Category:Nested array model]] | {{APL syntax}}[[Category:APL syntax]][[Category:Nested array model]] | ||