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A '''[[wikipedia:quine|quine]]''' is a program which takes no input and produces a copy of its own source code as its only output. | A '''[[wikipedia:quine|quine]]''' is a program which takes no input and produces a copy of its own source code as its only output. | ||
== Traditional expression == | |||
In APL, a quine is listed in the [[FinnAPL idiom library]] as "an expression giving itself": | In APL, a quine is listed in the [[FinnAPL idiom library]] as "an expression giving itself": | ||
< | <syntaxhighlight lang=apl> | ||
1⌽22⍴11⍴'''1⌽22⍴11⍴''' | 1⌽22⍴11⍴'''1⌽22⍴11⍴''' | ||
</ | </syntaxhighlight> | ||
=== Modern update === | |||
In 2019, [[Nick Nikolov]] proposed to shorten it using the [[commute]] operator:<ref>[https://chat.stackexchange.com/transcript/message/48380903#48380903 Transcript for 2019-01-06] – [[APL Orchard]].</ref> | In 2019, [[Nick Nikolov]] proposed to shorten it using the [[commute]] operator:<ref>[https://chat.stackexchange.com/transcript/message/48380903#48380903 Transcript for 2019-01-06] – [[APL Orchard]].</ref> | ||
< | <syntaxhighlight lang=apl> | ||
1⌽,⍨9⍴'''1⌽,⍨9⍴''' | 1⌽,⍨9⍴'''1⌽,⍨9⍴''' | ||
</ | </syntaxhighlight> | ||
==== Explanation ==== | |||
This shorter version is explain as follows:<ref>[https://codegolf.stackexchange.com/a/178459/87954 Golf you a quine for great good! – APL (Dyalog Unicode), 18 bytes] – Code Golf Stack Exchange.</ref> | |||
* <syntaxhighlight lang=apl inline>'''1⌽,⍨9⍴'''</syntaxhighlight> the characters <syntaxhighlight lang=text inline>'1⌽,⍨9⍴'</syntaxhighlight> | |||
* <syntaxhighlight lang=apl inline>9⍴</syntaxhighlight> reshape to shape 9, resulting in <syntaxhighlight lang=text inline>'1⌽,⍨9⍴''</syntaxhighlight> | |||
* <syntaxhighlight lang=apl inline>,⍨</syntaxhighlight> concatenate with itself, resulting in <syntaxhighlight lang=text inline>'1⌽,⍨9⍴'''1⌽,⍨9⍴''</syntaxhighlight> | |||
* <syntaxhighlight lang=apl inline>1⌽</syntaxhighlight> rotate one character to the left, getting the characters: <syntaxhighlight lang=text inline>1⌽,⍨9⍴'''1⌽,⍨9⍴'''</syntaxhighlight> | |||
== Further Entries == | |||
=== Based on replicating quote === | |||
In May 2022, [[APL Farm]] user OsKaR31415 shared the following:<ref>[https://discord.com/channels/821509511977762827/821511138184396840/976205210580037662 Transcript]. [[APL Farm]]. 2022-05-17.</ref> | |||
<syntaxhighlight lang=apl> | |||
'{∊⍵⍺⍵⍺,4/⍵}'{∊⍵⍺⍵⍺,4/⍵}'''' | |||
</syntaxhighlight> | |||
==== Explanation ==== | |||
In this code, the main function is <syntaxhighlight lang=apl inline>{∊⍵⍺⍵⍺,4/⍵}</syntaxhighlight> with the right argument <syntaxhighlight lang=apl inline>⍵</syntaxhighlight> being single quote literal (spelled with four quotes, <syntaxhighlight lang=apl inline>''''</syntaxhighlight>, because single quotes delimit APL character literals, and quotes inside such must be doubled), and the left argument <syntaxhighlight lang=apl inline>⍺</syntaxhighlight> being the character vector representation of the function (<syntaxhighlight lang=apl inline>'{∊⍵⍺⍵⍺,4/⍵}'</syntaxhighlight>). | |||
The idea behind this quine is that the only thing you need to have a string containing the original code is to reproduce this structure: [quote] [function] [quote] [function] [quote] [quote] [quote] [quote]. This is precisely what the function does. Given the representation of a function <syntaxhighlight lang=apl inline>⍺</syntaxhighlight> (itself in this case), and character <syntaxhighlight lang=apl inline>⍵</syntaxhighlight> (here, the quote), it produces the structure <syntaxhighlight lang=apl inline>⍵ ⍺ ⍵ ⍺ ⍵ ⍵ ⍵ ⍵</syntaxhighlight>. A more explicit version would be <syntaxhighlight lang=apl inline>'{⍵,⍺,⍵,⍺,⍵,⍵,⍵,⍵}'{⍵,⍺,⍵,⍺,⍵,⍵,⍵,⍵}''''</syntaxhighlight> which simply concatenates together the required parts. The original quine is very similar, only using the shorter <syntaxhighlight lang=apl inline>4/⍵</syntaxhighlight> to produce the 4 occurrences of <syntaxhighlight lang=apl inline>⍵</syntaxhighlight>, and [[code golf|golfs]] away the spaces, instead opting for [[Enlist]] (<syntaxhighlight lang=apl inline>∊</syntaxhighlight>) to flatten the intermediary [[nested array]]. | |||
=== Based on code point of quote === | |||
In Jun 2022, [[Jay Foad]] shared the following:<ref>Message {{M|61482904}}. [[APL Orchard]]. 2022-06-30.</ref> | |||
<syntaxhighlight lang=apl> | |||
{,⍨⍵,⎕UCS 39}'{,⍨⍵,⎕UCS 39}' | |||
</syntaxhighlight> | |||
==== Explanation ==== | |||
In this code, the main function is <syntaxhighlight lang=apl inline>{,⍨⍵,⎕UCS 39}</syntaxhighlight> with the argument <syntaxhighlight lang=apl inline>⍵</syntaxhighlight> being the function itself which avoids duplication of quotes by generating the quote from its [[Universal Character Set]] code point (<syntaxhighlight lang=apl inline>⎕UCS</syntaxhighlight>). | |||
The idea behind this quine is that the only thing you need to have a string containing the original code is to reproduce this structure: [function] [quote] [function] [quote]. This is precisely what the function does. Given the representation of a function <syntaxhighlight lang=apl inline>⍵</syntaxhighlight> (itself in this case), it generates a quote and concatenates it on the right of the function definition, giving [function] [quote]. It then uses [[commute|self]]-[[catenate|concatenation]] (<syntaxhighlight lang=apl inline>,⍨</syntaxhighlight>) to repeat the two parts into the required four. | |||
== External links == | == External links == | ||