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Match can be used to compare [[simple]] [[vector]]s to see if they are the same: | Match can be used to compare [[simple]] [[vector]]s to see if they are the same: | ||
< | <syntaxhighlight lang=apl> | ||
1 2 3 ≡ 1 2 3 | 1 2 3 ≡ 1 2 3 | ||
1 | 1 | ||
1 2 3 ≡ 1 2 5 | 1 2 3 ≡ 1 2 5 | ||
0 | 0 | ||
</ | </syntaxhighlight> | ||
Using [[strand notation]] to create [[nested]] arrays, we see that Match also compares elements nested within arrays: | Using [[strand notation]] to create [[nested]] arrays, we see that Match also compares elements nested within arrays: | ||
< | <syntaxhighlight lang=apl> | ||
(1 2)3 ≡ (2 1)3 | (1 2)3 ≡ (2 1)3 | ||
0 | 0 | ||
</ | </syntaxhighlight> | ||
Arrays with the same elements but different shapes do not match. Unlike [[Equal to]], Match never gives a [[RANK ERROR]] or [[LENGTH ERROR]] because of argument shapes. | Arrays with the same elements but different shapes do not match. Unlike [[Equal to]], Match never gives a [[RANK ERROR]] or [[LENGTH ERROR]] because of argument shapes. | ||
< | <syntaxhighlight lang=apl> | ||
(3 2⍴⍳6) ≡ (2 3⍴⍳6) | (3 2⍴⍳6) ≡ (2 3⍴⍳6) | ||
0 | 0 | ||
'a' ≡ ,'a' ⍝ Scalar versus singleton | 'a' ≡ ,'a' ⍝ Scalar versus singleton | ||
0 | 0 | ||
</ | </syntaxhighlight> | ||
Match depends on [[comparison tolerance]]. Here two arrays which are not exactly identical are still reported as matching: | Match depends on [[comparison tolerance]]. Here two arrays which are not exactly identical are still reported as matching: | ||
< | <syntaxhighlight lang=apl> | ||
a←⎕CT+b←2 3 4 ⍝ Two vectors | a←⎕CT+b←2 3 4 ⍝ Two vectors | ||
a - b ⍝ Difference is not zero | a - b ⍝ Difference is not zero | ||
| Line 31: | Line 31: | ||
a {⎕CT←0⋄⍺≡⍵} b ⍝ ...but not intolerantly | a {⎕CT←0⋄⍺≡⍵} b ⍝ ...but not intolerantly | ||
0 | 0 | ||
</ | </syntaxhighlight> | ||
== Description == | == Description == | ||
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=== APL model === | === APL model === | ||
The following model implements Match in [[Dyalog APL]]. Because Match compares the same characteristic of both arguments, [[Over]] (< | The following model implements Match in [[Dyalog APL]]. Because Match compares the same characteristic of both arguments, [[Over]] (<syntaxhighlight lang=apl inline>⍥</syntaxhighlight>) is used throughout. | ||
< | <syntaxhighlight lang=apl> | ||
Match ← { | Match ← { | ||
⍺≠⍥(≢⍴)⍵: 0 ⍝ Rank | ⍺≠⍥(≢⍴)⍵: 0 ⍝ Rank | ||
| Line 52: | Line 52: | ||
⍺∧.∇⍥,⍵ ⍝ Recurse | ⍺∧.∇⍥,⍵ ⍝ Recurse | ||
} | } | ||
</ | </syntaxhighlight> | ||
{{Works in|[[Dyalog APL 18.0]]}} | {{Works in|[[Dyalog APL 18.0]]}} | ||
== History == | |||
Match was defined in [[Jim Brown]]'s 1971 Ph.D. thesis, "A Generalization of APL",<ref>[[Jim Brown]]. [http://www.softwarepreservation.org/projects/apl/Books/AGENERALIZATIONOFAPL "A Generalization of APL"]. 1971.</ref> with the name "same". It was implemented in both [[NARS]] (called it "Equivalent") and [[SHARP APL]]<ref>[https://www.jsoftware.com/papers/satn41.htm "Composition and Enclosure"]. SATN-41, 1981-06-20.</ref> in 1981. Both [[Dyalog APL]] and [[APL2]] included it with the name "Match" taken from SHARP, which has generally been used in later APLs as well. | |||
== External links == | |||
=== Documentation === | |||
* [https://help.dyalog.com/latest/#Language/Primitive%20Functions/Match.htm Dyalog] | |||
* [http://microapl.com/apl_help/ch_020_020_360.htm APLX] | |||
* [https://mlochbaum.github.io/BQN/doc/match.html BQN] | |||
* J [https://www.jsoftware.com/help/dictionary/d122.htm Dictionary], [https://code.jsoftware.com/wiki/Vocabulary/minusco#dyadic NuVoc] (as <syntaxhighlight lang=j inline>-:</syntaxhighlight>) | |||
== See also == | |||
* [[Not Match]] | |||
== References == | |||
<references/> | |||
{{APL built-ins}}[[Category:Primitive functions]] | {{APL built-ins}}[[Category:Primitive functions]] | ||