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{{Built-in|Tally|≢}} is a [[primitive function|primitive]] [[monadic function]] which returns the number of [[major cell]]s in its [[argument]]. The Tally of an array is also the first [[element]] of its [[shape]], or 1 if it is a [[scalar]] (since a scalar is its own major cell by convention). Tally counts the first [[axis]] rather than the last because the number of major cells is more useful in [[leading axis theory]]. | {{Built-in|Tally|≢}} or '''Count''' is a [[primitive function|primitive]] [[monadic function]] which returns the number of [[major cell]]s in its [[argument]]. The Tally of an array is also the first [[element]] of its [[shape]], or 1 if it is a [[scalar]] (since a scalar is its own major cell by convention). Tally counts the first [[axis]] rather than the last because the number of major cells is more useful in [[leading axis theory]]. | ||
== Examples == | == Examples == | ||
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== History == | == History == | ||
Tally was introduced in [[ | Tally was introduced in [[A]] with the name "count" and symbol <source lang=j inline>#</source>. The same notation was carried forward to [[A+]], as well as [[J]] following [[Arthur Whitney]]'s suggestion. The primitive was present in [[NARS2000]] by 2010, with the name "Tally" and symbol <source lang=apl inline>></source><ref>NARS2000 Wiki. [http://wiki.nars2000.org/index.php?title=Tally&oldid=573 Tally]. Old revision: 2010-08-29.</ref>. The symbol <source lang=apl inline>≢</source> for Tally was introduced in [[Dyalog APL 14.0]], and quickly adopted by NARS2000. It was later added to [[GNU APL]] and has been included in many recent APLs based on Dyalog, such as [[ngn/apl]], [[dzaima/APL]], and [[APL\iv]]. | ||
Before the addition of Tally (and [[Zilde]]), there were numerous ways to get the length of a vector as a scalar: | |||
<source lang=apl> | |||
''⍴⍴v | |||
(⍴0)⍴⍴v | |||
(⍳0)⍴⍴v | |||
(⍴v)[0] | |||
×/⍴v ⍝ shortest and obscure | |||
0⊥⍴v ⍝ shortest and obscurest | |||
</source> | |||
== External links == | == External links == | ||
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* [http://help.dyalog.com/latest/index.htm#Language/Primitive%20Functions/Tally.htm Dyalog] | * [http://help.dyalog.com/latest/index.htm#Language/Primitive%20Functions/Tally.htm Dyalog] | ||
* [http://wiki.nars2000.org/index.php/Tally NARS2000] | |||
* J [http://www.jsoftware.com/help/dictionary/d400.htm Dictionary], [https://code.jsoftware.com/wiki/Vocabulary/number NuVoc] | * J [http://www.jsoftware.com/help/dictionary/d400.htm Dictionary], [https://code.jsoftware.com/wiki/Vocabulary/number NuVoc] | ||
== References == | |||
<references /> | |||
{{APL built-ins}}[[Category:Primitive functions]] | |||