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Clean up, and avoid claiming up arrow can mean Disclose as it's never associated with that name
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(Clean up, and avoid claiming up arrow can mean Disclose as it's never associated with that name) |
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{{Built-in|Disclose|⊃}} is a [[monadic function]] | {{Built-in|Disclose|⊃}} or '''Reveal''' is a [[monadic function]] in [[Nested array model|nested]] APLs which reduces the level of nesting of an array. It may refer to: | ||
* [[First]], a the function extracting its argument's initial element in [[ravel order]]. | |||
* [[Mix]], a function combining its argument's elements (requiring conforming shapes or padding with [[fill element]]s). | |||
These two meanings are distributed among the [[glyphs]] [[Right Shoe]] (<syntaxhighlight lang=apl inline>⊃</syntaxhighlight>) and [[Up Arrow]] (<syntaxhighlight lang=apl inline>↑</syntaxhighlight>) in nested APLs; the name "Disclose" is usually used for whichever meaning is represented by <syntaxhighlight lang=apl inline>⊃</syntaxhighlight> and never for the one represented by <syntaxhighlight lang=apl inline>↑</syntaxhighlight>, which is called "First" or "Mix". | |||
In the [[SHARP APL]] family, the behavior of Mix follows automatically by giving Disclose a [[function rank]] of 0. Disclose returns the contents of each [[box]] in an array, and rank treats these results as the cells of a result array. | |||
== History == | |||
Early experiments in array nesting usually defined a primitive to extract the contents of a nested [[scalar]], but did not always specify how it should behave on an array. [[Jim Brown]]'s "A Generalization of APL"<ref>[[Jim Brown]]. [http://www.softwarepreservation.org/projects/apl/Books/AGENERALIZATIONOFAPL "A Generalization of APL"] (Ph.D. thesis). 1971.</ref> stated that it "may be undefined" on non-scalar arrays. However, all dialects do extend it to non-scalars, either as First or Mix. | |||
[[STSC]]'s [[NARS]], the first nested APL released, defined Disclose <syntaxhighlight lang=apl inline>⊃</syntaxhighlight> to be First, leaving monadic <syntaxhighlight lang=apl inline>↑</syntaxhighlight> as Mix, and [[Dyalog APL]] followed this choice. But [[IBM]] later released [[APL2]] with the definitions the other way around, a choice eventually adopted by the nested APL standard [[ISO/IEC 13751:2001]]. Due to the perceived authority of APL2, later dialects such as [[APLX]], [[NARS2000]], and [[GNU APL]] generally follow the APL2 definition, and Dyalog as well as STSC's [[APL*PLUS]] implement [[Migration Level]] to allow programs to select it. However, the NARS definition remains the default in Dyalog, causing it to be adopted by some dialects such as [[April]], [[dzaima/APL]], and [[ngn/apl]]. | |||
== References == | |||
<references/> | |||
{{APL built-ins}}[[Category:Primitive functions]] | {{APL built-ins}}[[Category:Primitive functions]] | ||