Quine
This is an article about a kind of computer program. You may be looking for information on the philosopher W. V. Quine.In computing, a quine is a program (a form of metaprogram) that produces its complete source code as its only output. For amusement, hackers sometimes attempt to develop the shortest possible quine in any given programming language.
Note that simply opening the source file of the program and printing the contents is considered cheating.
Quines are named after W. V. Quine, who made an extensive study of indirect self-reference: he coined, among others, the paradox-producing expression, "yields falsehood when appended to its own quotation."
\n ->+>+++>>+>++>+>+++>>+>++>>>+>+>+>++>+>>>>+++>+>>++>+>+++>>++>++>>+>>+>++>++>\n +>>>>+++>+>>>>++>++>>>>+>>++>+>+++>>>++>>++++++>>+>>++>+>>>>+++>>+++++>>+>+++\n >>>++>>++>>+>>++>+>+++>>>++>>+++++++++++++>>+>>++>+>+++>+>+++>>>++>>++++>>+>>\n ++>+>>>>+++>>+++++>>>>++>>>>+>+>++>>+++>+>>>>+++>+>>>>+++>+>>>>+++>>++>++>+>+\n ++>+>++>++>>>>>>++>+>+++>>>>>+++>>>++>+>+++>+>+>++>>>>>>++>>>+>>>++>+>>>>+++>\n +>>>+>>++>+>++++++++++++++++++>>>>+>+>>>+>>++>+>+++>>>++>>++++++++>>+>>++>+>>\n >>+++>>++++++>>>+>++>>+++>+>+>++>+>+++>>>>>+++>>>+>+>>++>+>+++>>>++>>++++++++\n >>+>>++>+>>>>+++>>++++>>+>+++>>>>>>++>+>+++>>+>++>>>>+>+>++>+>>>>+++>>+++>>>+\n [[->>+<<]<+]+++++[->+++++++++<]>.[+]>>[<<+++++++[->+++++++++<]>-\n .------------------->-[-<.<+>>]<[+]<+>>>]<<<[-[-[-[>>+<++++++[->+++++<]]>++++\n ++++++++++<]>+++<]++++++[->+++++++<]>+<<<-[->>>++<<<]>[->>.<<]<<]\n
Sample quine in C
char x[]="char x[]=%c%s%c;%cint main() {printf(x,34,x,34,10,10);return 0;}%c";
int main() {printf(x,34,x,34,10,10);return 0;}
Sample quine in LISP
((lambda (x)
(list x (list (quote quote) x)))
(quote
(lambda (x)
(list x (list (quote quote) x)))))
Sample quine in OCaml
(fun s -> Printf.printf "%s %S" s s) "(fun s -> Printf.printf \\"%s %S\\" s s)"
Sample quine in Python
a='a=%s;print a%%`a`';print a%`a`
Sample quine in Perl
$_=q{$_=q{Q};s/Q/$_/;print};s/Q/$_/;print
Sample quine in BASIC
10 C=": PRINT CHR(49)+CHR(48)+CHR(32)+CHR(67)+CHR(61)+CHR(34)+C+CHR(34)+C":
PRINT CHR(49)+CHR(48)+CHR(32)+CHR(67)+CHR(61)+CHR(34)+C+CHR(34)+C
Sample quine in Pascal
const a='const a=';b='begin write(a,#39,a,#39#59#98#61#39,b,#39#59#10,b) end.';
begin write(a,#39,a,#39#59#98#61#39,b,#39#59#10,b) end.
Sample quine in Brainfuck
(Note: This should be one continuous line of code, but line breaks have been added for ease of reading.)Sample quine in HQ9+
Q
Sample quine in MS-DOS
@echo off
%1 %2
call %0 goto e %%
call %0 goto e %%3 echo.%%4
echo :f
goto f
:e
echo.%4@echo off
echo.%4%31 %32
echo.%4call %30 goto e %3%3
echo.%4call %30 goto e %3%33 echo.%3%34
echo.%4echo :f
echo.%4goto f
echo.%4:e
:f
Sample quine in PHP
$a='chr(60).chr(63).chr(10).chr(36).chr(97).chr(61).chr(39).$a.chr(39).chr(59).chr(10)."echo $a;".chr(10).chr(63).chr(62)';
echo chr(60).chr(63).chr(10).chr(36).chr(97).chr(61).chr(39).$a.chr(39).chr(59).chr(10)."echo $a;".chr(10).chr(63).chr(62);
?>
$a='
$a=2;
echo str_replace(1+1,chr(39).$a.chr(39),$a);
?>';
echo str_replace(1+1,chr(39).$a.chr(39),$a);
?>
Sample quine in PostScript
(dup == {dup cvx exec} pop 8 12 getinterval =)
dup cvx exec
External links
See also