Array notation: Difference between revisions

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Array notation (view source)

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:''See also [[Array notation in Dyalog APL]]''
:''See also [[Array notation in Dyalog APL]]''


One-dimensional list syntax with surrounding brackets and delimiters, matching [[wikipedia:sequence|sequence]] notation in mathematics, is common in programming. It appears as early as [[wikipedia:ALGOL 68|ALGOL 68]] with parentheses, and square-bracket lists or arrays feature in languages from the 1970s such as [[wikipedia:ML (programming language)|ML]] and [[wikipedia:Icon (programming language)|Icon]]. [[MATLAB]] uses matrix syntax with square brackets, semicolons to separate rows, and commas to separate columns.
One-dimensional list syntax with surrounding brackets and delimiters, matching [[wikipedia:sequence|sequence]] notation in mathematics, is common in programming. It appears as early as [[wikipedia:ALGOL 68|ALGOL 68]] with parentheses, and square-bracket lists feature in languages from the 1970s such as [[wikipedia:ML (programming language)|ML]] and [[wikipedia:Icon (programming language)|Icon]]. [[MATLAB]] uses matrix syntax with square brackets, semicolons to separate rows, and commas to separate elements within a row. [[wikipedia:FP (programming language)|FP]] uses angle brackets for lists, and square brackets for function "construction", with behavior like [[function array]]s.


List notation appears in [[Nial]], with brackets and commas like <source lang=apl inline>[a,b,c]</source>, and in [[A+]] and [[K]], with parentheses and semicolons like <source lang=apl inline>(a;b;c)</source>. In A+ this is related to [[bracket indexing]] and an "expression group" notation written with curly braces and semicolons. It allows line breaks, but in addition to rather than in place of semicolons. The later K version corresponds more closely to APL: the semicolon is a statement separator and is interchangeable with a line break, and because K represents arrays with nested lists, it corresponds to both vector and high-rank array notation. In all three languages this syntax can be used with functions, as functions are first-class in A+ and K, and arrays of functions called "atlases" can be used for specific purposes in Nial.
List notation appears in [[Nial]] using brackets and commas like <source lang=apl inline>[a,b,c]</source>, and allowing function arrays called "atlases". [[A+]] and [[K]] have a list notation using parentheses and semicolons like <source lang=apl inline>(a;b;c)</source>. In A+ this is related to [[bracket indexing]] and an "expression group" notation written with curly braces and semicolons. It allows line breaks, but in addition to rather than in place of semicolons. The later K version corresponds more closely to APL: the semicolon is a statement separator and is interchangeable with a line break, and because K represents arrays with nested lists, it corresponds to both vector and high-rank array notation.


The first published proposals that influenced [[Dyalog APL]]'s array notation were made by [[Phil Last]] at [[Dyalog '15]] and later in [[Vector Journal]].<ref>[[Phil Last]]. [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><ref>[[Phil Last]]. [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> Last also used the design in Acre Desktop, a project manager for Dyalog APL, to support storing constant arrays and namespaces in text files. Following the conference presentation, [[Adám Brudzewsky]] began work on array notation and presented on it in a series of conferences, initially using parentheses for the high-rank notation<ref>[[Adám Brudzewsky]]. [https://dyalog.tv/Dyalog17/?v=CRQNzL8cUQE Literal Notation for Arrays and Namespaces] ([https://www.dyalog.com/uploads/conference/dyalog17/presentations/D11_Literal_Notation_for_Arrays_and_Namespaces.pdf slides]). [[Dyalog '17]].</ref> and later returning to square brackets.<ref>[[Adám Brudzewsky]]. [https://dyalog.tv/Dyalog18/?v=GAdQuOtPcfM Array Notation Mk III]. [[Dyalog '18]].</ref><ref>[[Adám Brudzewsky]]. [https://apl-germany.de/wp-content/uploads/2021/11/APL_Journal_2020_1u2.pdf#page=34 A Notation for APL Arrays]. APL-Journal, Volume 2020, number 1-2. [[APL Germany|APL-Germany e.V.]] 2020.</ref> Because Last's use of <source lang=apl inline>←</source> to separate namespace keys from values prevented lists from including arbitrary expressions (which might contain assignment), he proposed a change to <source lang=apl inline>:</source> as in [[wikipedia:JSON|JSON]]. [[Dyalog APL 18.0]], released in 2020, included support for array notation in source files loaded by [[Link]], but not in the language itself.<ref>[[Adám Brudzewsky]]. [https://dyalog.tv/Dyalog20/?v=5drncJiWOM4 Array Notation RC1] ([https://www.dyalog.com/uploads/conference/dyalog20/presentations/D09_Array_Notation_RC1.pdf slides]). [[Dyalog '20]].</ref>
The first published proposals that influenced [[Dyalog APL]]'s array notation were made by [[Phil Last]] at [[Dyalog '15]] and later in [[Vector Journal]].<ref>[[Phil Last]]. [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><ref>[[Phil Last]]. [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> Last also used the design in Acre Desktop, a project manager for Dyalog APL, to support storing constant arrays and namespaces in text files. Following the conference presentation, [[Adám Brudzewsky]] began work on array notation and presented on it in a series of conferences, initially using parentheses for the high-rank notation<ref>[[Adám Brudzewsky]]. [https://dyalog.tv/Dyalog17/?v=CRQNzL8cUQE Literal Notation for Arrays and Namespaces] ([https://www.dyalog.com/uploads/conference/dyalog17/presentations/D11_Literal_Notation_for_Arrays_and_Namespaces.pdf slides]). [[Dyalog '17]].</ref> and later returning to square brackets.<ref>[[Adám Brudzewsky]]. [https://dyalog.tv/Dyalog18/?v=GAdQuOtPcfM Array Notation Mk III]. [[Dyalog '18]].</ref><ref>[[Adám Brudzewsky]]. [https://apl-germany.de/wp-content/uploads/2021/11/APL_Journal_2020_1u2.pdf#page=34 A Notation for APL Arrays]. APL-Journal, Volume 2020, number 1-2. [[APL Germany|APL-Germany e.V.]] 2020.</ref> Because Last's use of <source lang=apl inline>←</source> to separate namespace keys from values prevented lists from including arbitrary expressions (which might contain assignment), he proposed a change to <source lang=apl inline>:</source> as in [[wikipedia:JSON|JSON]]. [[Dyalog APL 18.0]], released in 2020, included support for array notation in source files loaded by [[Link]], but not in the language itself.<ref>[[Adám Brudzewsky]]. [https://dyalog.tv/Dyalog20/?v=5drncJiWOM4 Array Notation RC1] ([https://www.dyalog.com/uploads/conference/dyalog20/presentations/D09_Array_Notation_RC1.pdf slides]). [[Dyalog '20]].</ref>
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