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Text replacement - "</source>" to "</syntaxhighlight>"
(Add model that reflects common implementation.) |
m (Text replacement - "</source>" to "</syntaxhighlight>") |
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WEEK⍷'DAY' ⍝ WEEK not found in 'DAY'; left arg may have higher rank but it is never found | WEEK⍷'DAY' ⍝ WEEK not found in 'DAY'; left arg may have higher rank but it is never found | ||
0 0 0 | 0 0 0 | ||
</ | </syntaxhighlight> | ||
For [[nested array|nested arrays]], Find tests for exact [[match]] between the elements. | For [[nested array|nested arrays]], Find tests for exact [[match]] between the elements. | ||
| Line 34: | Line 34: | ||
'BIRDS' 'NEST'⍷'BIRDS' 'NEST' 'SOUP' | 'BIRDS' 'NEST'⍷'BIRDS' 'NEST' 'SOUP' | ||
1 0 0 | 1 0 0 | ||
</ | </syntaxhighlight> | ||
== Model == | == Model == | ||
| Line 46: | Line 46: | ||
(⍴⍵) ↑ ⍺∘{⍺≡(⍴⍺)↑⍵↓ww}¨ ⍳(×⍴⍺)+(⍴⍵)-⍴⍺ | (⍴⍵) ↑ ⍺∘{⍺≡(⍴⍺)↑⍵↓ww}¨ ⍳(×⍴⍺)+(⍴⍵)-⍴⍺ | ||
} | } | ||
</ | </syntaxhighlight> | ||
=== Empty left argument === | === Empty left argument === | ||
Implementations differ in their treatment of empty left arguments: | Implementations differ in their treatment of empty left arguments: | ||
| Line 53: | Line 53: | ||
* [[APL+]] finds empty arrays everywhere, even where they would extend beyond the edges of the right argument. | * [[APL+]] finds empty arrays everywhere, even where they would extend beyond the edges of the right argument. | ||
The prototype is never used, in contrast to [[Match]], which in many APLs compares prototypes of empty arrays. The behavior may come from the use of the [[inner product]] <source lang=apl inline>∧.=</ | The prototype is never used, in contrast to [[Match]], which in many APLs compares prototypes of empty arrays. The behavior may come from the use of the [[inner product]] <source lang=apl inline>∧.=</syntaxhighlight> in early [[Array_model#Flat_array_theory|flat]] APLs where [[Match]] is not a primitive; this function naturally checks elements and not the prototype. [[Adin Falkoff]] presented code for Find-like functions using <source lang=apl inline>∧.=</syntaxhighlight> at [[APL79]].<ref>[[Adin Falkoff|Falkoff, Adin]]. [https://dl.acm.org/doi/10.1145/390009.804448 A note on pattern matching: Where do you find the match to an empty array?] at [[APL79]].</ref> | ||
Correspondingly, the above model can be amended to match the behaviour of the primitive (in APL2, etc.) by replacing the <source lang=apl inline>≡</ | Correspondingly, the above model can be amended to match the behaviour of the primitive (in APL2, etc.) by replacing the <source lang=apl inline>≡</syntaxhighlight> with <source lang=apl inline>{(⍺≡⍥⍴⍵)∧(∧/⍺≡¨⍥,⍵)}</syntaxhighlight> which ignores prototypes, only comparing shape and elements:<ref>[[Adám Brudzewsky|Brudzewsky, Adám]]. [https://forums.dyalog.com/viewtopic.php?f=30&t=1735&p=7416#p7416 RE: ⍷ follies]. Dyalog Forums. 23 Aug 2022.</ref> | ||
<source lang=apl> | <source lang=apl> | ||
ebar2←{⎕IO←0 | ebar2←{⎕IO←0 | ||
| Line 64: | Line 64: | ||
(⍴⍵) ↑ ⍺∘{⍺ {(⍺≡⍥⍴⍵)∧(∧/⍺≡¨⍥,⍵)} (⍴⍺)↑⍵↓ww}¨ ⍳(×⍴⍺)+(⍴⍵)-⍴⍺ | (⍴⍵) ↑ ⍺∘{⍺ {(⍺≡⍥⍴⍵)∧(∧/⍺≡¨⍥,⍵)} (⍴⍺)↑⍵↓ww}¨ ⍳(×⍴⍺)+(⍴⍵)-⍴⍺ | ||
} | } | ||
</ | </syntaxhighlight> | ||
== See also == | == See also == | ||
* [[Membership]] | * [[Membership]] | ||