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|<code>⊣</code> <code>⊢</code> | |<code>⊣</code> <code>⊢</code> | ||
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:''This page is about the class of primitive functions. For the result of an empty reduction, see [[Identity element]].'' | |||
An '''Identity function''', or '''tack function''', is one of the three [[primitive function]]s which returns one of its [[argument]]s with no modification: | An '''Identity function''', or '''tack function''', is one of the three [[primitive function]]s which returns one of its [[argument]]s with no modification: | ||
* '''Identity''', '''Same''', or '''Pass''' (<source lang=apl inline>⊣</source> or <source lang=apl inline>⊢</source>) is [[monadic]] and returns its only argument. | * '''Identity''', '''Same''', or '''Pass''' (<source lang=apl inline>⊣</source> or <source lang=apl inline>⊢</source>) is [[monadic]] and returns its only argument. | ||
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== Uses == | == Uses == | ||
As the left [[operand]] to [[ | As the left [[operand]] to [[Beside]], Right makes the resulting [[derived function]] ignore its left argument (so the result is produced by a [[monadic]] invocation of the right operand, on the right argument). The same pattern can be produced by using Right as the right operand to [[Atop]]. | ||
<source lang=apl> | <source lang=apl> | ||
2 ⊢∘- 7 | 2 ⊢∘- 7 | ||
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¯7 | ¯7 | ||
</source> | </source> | ||
The mirror image—using only the left argument while ignoring the | The mirror image—using only the left argument while ignoring the right—is attained by using [[Atop]] (either the operator, or a 2-train) with Left as the right operand. | ||
<source lang=apl> | <source lang=apl> | ||
2 -⍤⊣ 7 | 2 -⍤⊣ 7 | ||
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1 2 3 4 5 6 | 1 2 3 4 5 6 | ||
</source> | </source> | ||
== External links == | == External links == | ||
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* Dyalog: [https://help.dyalog.com/17.1/Content/Language/Symbols/Left%20Tack.htm Left Tack], [https://help.dyalog.com/17.1/Content/Language/Symbols/Right%20Tack.htm Right Tack] | * Dyalog: [https://help.dyalog.com/17.1/Content/Language/Symbols/Left%20Tack.htm Left Tack], [https://help.dyalog.com/17.1/Content/Language/Symbols/Right%20Tack.htm Right Tack] | ||
* APLX: [http://microapl.com/apl_help/ch_020_020_754.htm Left], [http://microapl.com/apl_help/ch_020_020_756.htm Right], [http://microapl.com/apl_help/ch_020_020_755.htm Pass] | * APLX: [http://microapl.com/apl_help/ch_020_020_754.htm Left], [http://microapl.com/apl_help/ch_020_020_756.htm Right], [http://microapl.com/apl_help/ch_020_020_755.htm Pass] | ||
* [https://mlochbaum.github.io/BQN/doc/identity.html BQN] | |||
{{APL built-ins}} | {{APL built-ins}}[[Category:Primitive functions]] | ||