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Commute: Difference between revisions
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This decrements from the vector: | This decrements from the vector: | ||
< | <syntaxhighlight lang=apl> | ||
1 -⍨ 1 2 3 | 1 -⍨ 1 2 3 | ||
0 1 2 | 0 1 2 | ||
</ | </syntaxhighlight> | ||
{{Works in|[[Dyalog APL]], [[dzaima/APL]], [[NARS2000]]}} | {{Works in|[[Dyalog APL]], [[dzaima/APL]], [[NARS2000]]}} | ||
Double: | Double: | ||
< | <syntaxhighlight lang=apl> | ||
+⍨1 2 3 | +⍨1 2 3 | ||
2 4 6 | 2 4 6 | ||
</ | </syntaxhighlight> | ||
{{Works in|[[Dyalog APL]], [[dzaima/APL]], [[NARS2000]]}} | {{Works in|[[Dyalog APL]], [[dzaima/APL]], [[NARS2000]]}} | ||
[[Commute]] can be used to emulate a monadic < | [[Commute]] can be used to emulate a monadic <syntaxhighlight lang=apl inline>f g h</syntaxhighlight> [[Fork]] when combined with [[Compose]] (note the following code is not workable APL, but a series of evaluations): | ||
< | <syntaxhighlight lang=apl> | ||
g⍨∘f⍨∘h⍨ x | g⍨∘f⍨∘h⍨ x | ||
x g⍨∘f⍨∘h x ⍝ the last ⍨ is being used monadically, i.e. Selfie | x g⍨∘f⍨∘h x ⍝ the last ⍨ is being used monadically, i.e. Selfie | ||
| Line 24: | Line 24: | ||
(h x) g⍨ (f x) | (h x) g⍨ (f x) | ||
(f x) g (h x) ⍝ the last ⍨ is being used dyadically, i.e. Swap | (f x) g (h x) ⍝ the last ⍨ is being used dyadically, i.e. Swap | ||
</ | </syntaxhighlight> | ||
== History == | |||
The Commute operator was defined in [[Operators and Functions]] in 1978, and taken up by [[NARS]] as a result. [[Dyalog]], influenced by NARS, included the operator early on. While it didn't appear in [[SHARP APL]], it was included in [[J]] as "Reflex/Passive" (<syntaxhighlight lang=j inline>~</syntaxhighlight>). | |||
== External links == | == External links == | ||
| Line 35: | Line 39: | ||
* [https://help.dyalog.com/latest/index.htm#Language/Primitive%20Operators/Commute.htm Dyalog] | * [https://help.dyalog.com/latest/index.htm#Language/Primitive%20Operators/Commute.htm Dyalog] | ||
* [https://mlochbaum.github.io/BQN/doc/swap.html BQN] | |||
{{APL built-ins}}[[Category:Primitive operators]][[Category:Composition operators]] | {{APL built-ins}}[[Category:Primitive operators]][[Category:Composition operators]] | ||