Write a quine that

  1. Writes its source code to disk
  2. Recursively executes the written source code
  3. Produces some variation to the code the third time (so not a true Quine)
  4. Stops recursively calling itself the fifth time

Bonus points for leaving nothing on disk after execution.

  • 2
    \$\begingroup\$ Is this code-golf, or is there some other winning criterion, making it a code-challenge? It doesn't make sense to be both. \$\endgroup\$ Jan 7, 2014 at 17:48
  • \$\begingroup\$ @KendallFrey I guess I misunderstood what code-challenge was for. Removing the tag. Thanks! \$\endgroup\$
    – simon
    Jan 7, 2014 at 17:52
  • \$\begingroup\$ It's not clear what you consider to be a recursive call (or, for that matter, what "itself" is, given that you're creating imperfect copies), or what you expect to leave on the disk after it finishes. \$\endgroup\$ Jan 7, 2014 at 22:36
  • \$\begingroup\$ @PeterTaylor, thanks for the feedback. See clarifying edits. \$\endgroup\$
    – simon
    Jan 7, 2014 at 23:02

4 Answers 4


TCL 220

proc a b {
if {"$b"=="bb"} {
rename puts w
rename p puts
set b \;exit
puts [set q [open [incr ::i] w]] "proc a b \{[info body a]\};a b"
catch {rename puts p}
proc puts {n m} "p \$n \${m}$b"
close $q
source $::i
};a b

The code generates files 1, 2, 3 and 4. The variation is only present in 2, the others are equivalent to the original.


PHP 643

'echo $m."\n";',
'if($c<5){file_put_contents("q$c.php", $o);echo `php q$c.php`;}',
echo $m."\n";
if($c<5){file_put_contents("q$c.php", $o);echo `php q$c.php`;}



The variation in the code is produced in the 3rd iteration and is then only noticeable in the echoes of the 4th and 5th iterations.

  • \$\begingroup\$ Interesting interpretation of the rules! I didn't say whether the variation should be propagated or not. I guess technically a proper quine would propagate the change... +1 \$\endgroup\$
    – simon
    Jan 7, 2014 at 20:53

GTB, 19



X starts by default at 10, so we increment X once. Then, if X<15 check if X=13. If X=13, change the code. Then dump it all to memory.

  • \$\begingroup\$ If you are going to write your own language to answer code golf questions, you at least need to explain what it does... ;) \$\endgroup\$
    – simon
    Jan 8, 2014 at 17:36
  • \$\begingroup\$ Okay, I have :) \$\endgroup\$
    – Timtech
    Jan 8, 2014 at 21:35

In Squeak 4.x Smalltalk, it's not golfed, but there is a 299 chars version below

Compile this method in Object:

[| value morph |
value := (((self negated raisedTo: self - 1) / 15) exp exp - 1) reciprocal significand rounded reciprocal.
morph := ToolSet inspect: value.
[(Delay forSeconds: value reciprocal * 5) wait.
morph delete] fork.
World displayWorld.
(Delay forSeconds: 1) wait]
    on: Error
    do: [:exc | 
        FileDirectory default deleteFileNamed: 'quine'.
(FileStream forceNewFileNamed: 'quine') nextPutAll: thisContext method getSource; close.
^self class newCompiler
    evaluate: ((FileStream oldFileNamed: 'quine') contentsOfEntireFile lines allButFirst reduce: [:a :b | a , b])
    for: self + 1

Then evaluate '1 quine' where you want.

Each evaluation differs, because it is evaluated with incremented receiver. ( evaluate: ... for: self+1 )

The awfull expression computing the value is different for 3 (lead to a Fraction 1/2 instead of Integer 1) and for 5 (lead to ZeroDivide).

The file is deleted when the exception is caught and 5 is returned.

Otherwise, an inspector is opened on the value, the display is refreshed, the process is paused during 1 second before evaluating next quine.

A process for closing opened inspectors after a longer pause is forked.

The source of quine is retrieved via the current context of execution (thisContext method getSource), written, then re-evaluated without the first line (the name of the method). So the second and successive evaluation do not evaluate #quine, but an anonymous (#Doit) method sharing exactly the same contents.

Based on same principles, this less funny example will print 00100 in Transcript then stop when evaluating 1 quine, but it avoids explicit 3 and 5 in source:

quine|v|v:=self highBit-self lowBit.Transcript show:(1bitAnd:v).(2bitAnd:v)=0or:[^FileDirectory default deleteFileNamed:'q'].(FileStream forceNewFileNamed:'q')nextPutAll:thisContext method getSource;close.^Compiler evaluate:((FileStream oldFileNamed:'q')contentsOfEntireFile allButFirst:5)for:self+1

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