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(Close composition (SHARP/J) section) |
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In [[SHARP APL]] and [[J]], Over is implemented as a [[close composition]], meaning that (using SHARP syntax) <source lang=apl inline>f⍤g</source> has the overall [[function rank]] of <source lang=apl inline>g</source>. J uses <code>&</code> for the close form and <code>&:</code> for the rankless form that appears in modern APLs. | In [[SHARP APL]] and [[J]], Over is implemented as a [[close composition]], meaning that (using SHARP syntax) <source lang=apl inline>f⍤g</source> has the overall [[function rank]] of <source lang=apl inline>g</source>. J uses <code>&</code> for the close form and <code>&:</code> for the rankless form that appears in modern APLs. | ||
== History == | |||
[[Ken Iverson]] defined Over in 1978 as part of "Operators and Functions",<ref>[[Ken Iverson]]. [https://www.jsoftware.com/papers/opfns.htm ''Operators and Functions''], §8 Composition and Duality. IBM Research Report #RC7091. 1978-04-26.</ref> with the glyph <source lang=apl inline>¨</source>. He called it Composition, as there was no [[Atop operator]]. It was added to [[SHARP APL]] as a [[close composition]] with glyph <source lang=apl inline>⍤</source> and name "upon", with a limited implementation in 1981<ref>[https://www.jsoftware.com/papers/satn41.htm "Composition and Enclosure"]. SATN-41, 1981-06-20.</ref> followed by a full implementation in 1983 with the introduction of [[function rank]].<ref>[https://www.jsoftware.com/papers/satn45.htm "Language Extensions of May 1983"]. SATN-45, 1983-05-02.</ref> | |||
The glyph <source lang=apl inline>⍥</source> appeared in [[NARS2000]], with name "Composition", by 2011.<ref>[http://wiki.nars2000.org/index.php?title=Composition Composition]. [[NARS2000]] Wiki.</ref> The name "Over" was used in [[Dyalog APL 18.0]], suggested by [[Adám Brudzewsky]].<ref>[https://chat.stackexchange.com/transcript/message/42021088#42021088]</ref> | |||
== External links == | == External links == | ||