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Tacit programming: Difference between revisions
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Tacit functions apply to implicit arguments. This is in contrast to the explicit use of arguments in [[ | Tacit functions apply to implicit arguments. This is in contrast to the explicit use of arguments in [[dfn]]s (<source inline lang=apl>⍺ ⍵</source>) and [[tradfn]]s (which have named arguments). Some APL dialects allow to combine functions into '''trains''' following a small set of rules. This allows creating complex derived functions without specifying any arguments explicitly. | ||
Known dialects which implement trains are [[Dyalog APL]], [[dzaima/APL]], [[ngn/apl]] and [[NARS2000]]. | Known dialects which implement trains are [[Dyalog APL]], [[dzaima/APL]], [[ngn/apl]] and [[NARS2000]]. | ||
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A train is a series of functions in isolation. An isolated function is either surrounded by parentheses or named. Below, <source lang=apl inline>⍺</source> and <source lang=apl inline>⍵</source> refer to the arguments of the train. <source lang=apl inline>f</source>, <source lang=apl inline>g</source>, and <source lang=apl inline>h</source> are functions (which themselves can be tacit or not), and <source lang=apl inline>A</source> is an array. The arguments are processed by the following rules: | A train is a series of functions in isolation. An isolated function is either surrounded by parentheses or named. Below, <source lang=apl inline>⍺</source> and <source lang=apl inline>⍵</source> refer to the arguments of the train. <source lang=apl inline>f</source>, <source lang=apl inline>g</source>, and <source lang=apl inline>h</source> are functions (which themselves can be tacit or not), and <source lang=apl inline>A</source> is an array. The arguments are processed by the following rules: | ||
=== Forks === | |||
A 3-train is a ''fork'': | A 3-train is a ''fork'': | ||
{| | {| | ||
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|- | |- | ||
|<source lang=apl>⍺ (A g h) ⍵</source>|| {{←→}} ||<source lang=apl>A g (⍺ h ⍵)</source> | |<source lang=apl>⍺ (A g h) ⍵</source>|| {{←→}} ||<source lang=apl>A g (⍺ h ⍵)</source> | ||
|} | |||
=== Atops === | |||
A 2-train is an ''atop'': | |||
{| | |||
|<source lang=apl> (g h) ⍵</source>|| {{←→}} ||<source lang=apl>g ( h ⍵)</source> | |||
|- | |||
|<source lang=apl>⍺ (g h) ⍵</source>|| {{←→}} ||<source lang=apl>g (⍺ h ⍵)</source> | |||
|} | |} | ||
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Or fully parenthesised: | Or fully parenthesised: | ||
<source lang=apl> | <source lang=apl> | ||
]Boxing on -trains=parens | |||
Was OFF -trains=box | |||
((+.×⍨⊢~∘.×⍨)1↓⍳) ⍝ the train to be analysed | ((+.×⍨⊢~∘.×⍨)1↓⍳) ⍝ the train to be analysed | ||
(((+.×)⍨)(⊢~((∘.×)⍨)))(1↓⍳) | (((+.×)⍨)(⊢~((∘.×)⍨)))(1↓⍳) | ||
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666 ⍝ ⍎ executes original Accursed train | 666 ⍝ ⍎ executes original Accursed train | ||
</source> | </source> | ||
== See also == | |||
* [[Function composition]] | |||
== External links == | == External links == | ||