Under: Difference between revisions

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SHARP and J history
(Created page with "{{Built-in|Under|⍢}} is a primitive dyadic operator which takes two function operands. It pre-processes it's argument(s) with the monadic...")
 
(SHARP and J history)
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{{Built-in|Under|⍢}} is a [[primitive operator|primitive]] [[dyadic operator]] which takes two [[function]] [[operand]]s. It pre-processes it's argument(s) with the monadic right operand, before applying the left operand on/between the result(s), then undoing the pre-processing.<ref>[https://mlochbaum.github.io/BQN/help/under.html BQN: Circle Jot (⌾)]</ref>
{{Built-in|Under|⍢}}, or '''Dual''' (<code>¨</code>), is a [[primitive operator|primitive]] [[dyadic operator]] which takes two [[function]] [[operand]]s. It pre-processes its argument(s) with the monadic right operand, before applying the left operand on/between the result(s), then undoing the pre-processing.<ref>[https://mlochbaum.github.io/BQN/help/under.html BQN: Circle Jot (⌾)]</ref>


== Model ==
== Model ==
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==External links==
== History ==


===References===
The Dual operator, written <code>¨</code>, appeared in 1983 both in [[Rationalized APL]] and [[SHARP APL]]<ref>[https://www.jsoftware.com/papers/satn45.htm "Language Extensions of May 1983"]. SATN-45, 1983-05-02.</ref> just after. In both cases it was defined to be a [[close composition]], so that the overall function has the rank of the right operand; this allows <code>¨></code> to serve the purpose of [[Each]] from a [[Nested array model|nested]] APL. Iverson changed the name to Under for his 1987 [[A Dictionary of APL]], and [[J]] uses this name as well. It includes both a close form <source lang=j inline>&.</source> like SHARP and a non-close form <source lang=j inline>&.:</source>.
 
== External links ==
 
* [[J]]: <source lang=j inline>&.</source> [https://code.jsoftware.com/wiki/Vocabulary/ampdot NuVoc], [https://www.jsoftware.com/help/dictionary/d631.htm dictionary]; <source lang=j inline>&.:</source> [https://code.jsoftware.com/wiki/Vocabulary/ampdotco NuVoc], [https://www.jsoftware.com/help/dictionary/d631c.htm dictionary]
 
== References ==
<references/>
<references/>
{{APL built-ins}}[[Category:Primitive operators]][[Category:Composition operators]]
{{APL built-ins}}[[Category:Primitive operators]][[Category:Composition operators]]

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