Quine: Difference between revisions
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Remove Java example which just copies the file Quine.java to standard output. |
Clarified. Removed Perl, PHP and UNIX Shell examples |
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{{puzzle}} |
{{puzzle}} |
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{{clarified-review}} |
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Print out a program's own source code. Since this is a puzzle, shorter/more efficient versions are encouraged along side more obvious versions. |
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Print out a program's own source code without reading from the source file. |
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{{clarify_task}} |
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=={{header|Ada}}== |
=={{header|Ada}}== |
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Haskell does not keep the code in an uncompiled-equivalent form around at runtime, so the "quotation trick" has to be used. |
Haskell does not keep the code in an uncompiled-equivalent form around at runtime, so the "quotation trick" has to be used. |
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=={{header|Perl}}== |
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This example retrieves the name of the source file from the $0 variable, which represents the file path and name used to invoke the script. |
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#!/usr/bin/perl |
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open FILE, "< $0" or die "Failed to open self\n"; |
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map { print $_ } <FILE>; |
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close FILE; |
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Assuming the code is saved in the file quine.pl, this works when executed as |
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./quine.pl |
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or |
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perl quine.pl |
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but fails when fed to the perl interpreter's standard input as |
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cat quine.pl|perl |
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If we may assume that the source file is named "quine.pl", replacing |
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open FILE, "< $0" or die "Failed to open self\n"; |
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with |
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open FILE, "< quine.pl" or die "Failed to open self\n"; |
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will allow us to execute the code through the interpreter's [[standard input]]: |
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cat quine.pl|perl |
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=={{header|PHP}}== |
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This example obtains its own filename from the __FILE__ built-in variable. |
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<? |
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$fh = fopen( __FILE__, 'r' ); |
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echo fread($fh, filesize(__FILE__)); |
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fclose( $fh ); |
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?> |
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Strictly speaking, however, the example prints more than its own source code. Because PHP is designed to service HTTP requests, the output looks like this: |
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X-Powered-By: PHP/5.2.3-1ubuntu6 |
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Content-type: text/html |
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<? |
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$fh = fopen( __FILE__, 'r' ); |
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echo fread($fh, filesize(__FILE__)); |
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fclose( $fh ); |
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?> |
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(The X-Powered-By line will vary from system to system.) |
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=={{header|Seed7}}== |
=={{header|Seed7}}== |
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Original source: [http://seed7.sourceforge.net/algorith/puzzles.htm#self] |
Original source: [http://seed7.sourceforge.net/algorith/puzzles.htm#self] |
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=={{header|UNIX Shell}}== |
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#!/bin/sh |
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cat "$0" |
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Revision as of 18:53, 20 November 2007
Quine is a programming puzzle. It lays out a problem which Rosetta Code users are encouraged to solve, using languages and techniques they know. Multiple approaches are not discouraged, so long as the puzzle guidelines are followed. For other Puzzles, see Category:Puzzles.
Print out a program's own source code without reading from the source file.
Ada
with Text_Io; procedure Self is Q:Character:='"'; A:String(1..132):="with text_io;procedure self is q:character:=;a:string(1..132):=;begin text_io.put_line(a(1..45)&q&a(46..65)&q&a&q&a(66..132));end;"; begin Text_Io.Put_Line(A(1..45)&Q&A(46..65)&Q&A&Q&A(66..132)); end;
Befunge
The code space is also the data space of a Befunge program. Programs can be read and modified on the fly. This quine works by reading and printing each character of the source. (This is a implicit loop, since the Befunge codespace wraps around.)
:0g,:66+`#@_1+
Forth
SOURCE TYPE
Haskell
The obvious solution, as a one-liner:
let q s = putStrLn $ s ++ show s in q "let q s = putStrLn $ s ++ show s in q "
Having the string at the end makes things a bit simpler than in generic version mentioned in the Wikipedia article.
Haskell does not keep the code in an uncompiled-equivalent form around at runtime, so the "quotation trick" has to be used.
Seed7
$ include "seed7_05.s7i";
const array string: prog is [](
"$ include \"seed7_05.s7i\";",
"const array string: prog is [](",
"const proc: main is func",
" local var integer: number is 0;",
" begin",
" for number range 1 to 2 do writeln(prog[number]); end for;",
" for number range 1 to 11 do",
" writeln(literal(prog[number]) <& \",\");",
" end for;",
" writeln(literal(prog[12]) <& \");\");",
" for number range 3 to 12 do writeln(prog[number]); end for;",
" end func;");
const proc: main is func
local var integer: number is 0;
begin
for number range 1 to 2 do writeln(prog[number]); end for;
for number range 1 to 11 do
writeln(literal(prog[number]) <& ",");
end for;
writeln(literal(prog[12]) <& ");");
for number range 3 to 12 do writeln(prog[number]); end for;
end func;
Original source: [1]