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Write a quine... from which every other character can be removed it still be a valid quine. You can specify whether to start removing characters at the first or second character.

Scoring criteria (add bonuses/penatly percentages together for total percentage):

  • Answers must be at least 4 characters long
  • Program must contain at least one alphabetical character in its source, so for example, 12345!@#$%^&*() is disqualified
  • +750% if the language used is not Turing-complete (I'm looking at you, HTML!)
  • -15% if the solution does not read its source from anywhere in any form
  • -20% if you can also keep only every 5th character and still form a quine

The score is measured by the number of characters in the first program.

Example (not real programs):

If 123456789abcdef and 13579bdf are both quines, the score is 15. Additionally, if 159d is also a quine, then the final score is 12.

This is code-golf, so lowest score wins.

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16
  • 2
    \$\begingroup\$ @hosch250 The original program wouldn't be a quine because it wouldn't print those whitespaces. Same goes for unnecessary comments. \$\endgroup\$
    – Jwosty
    Commented Mar 7, 2014 at 5:26
  • 1
    \$\begingroup\$ Yeah, I have never programed a quine before, and have no idea how to do it without reading the source code in C++. I have seen them in C++ before though! \$\endgroup\$
    – user10766
    Commented Mar 7, 2014 at 5:37
  • 1
    \$\begingroup\$ You state: "-20% if you can also remove every 4 characters and still form a quine". But technically this is not what happens in your example. You mean you can do it a second time? \$\endgroup\$
    – mmumboss
    Commented Mar 7, 2014 at 8:17
  • 4
    \$\begingroup\$ Are the bonuses additive or multiplicative? That is, if my program is 10 chars long and qualifies for both the -15% bonus and the -20% bonus, will its score be 10 * (1 - 0.15 - 0.2) = 6.5 or 10 * (1 - 0.15) * (1 - 0.2) = 6.8? I assumed the latter, but an explicit clarification would be nice. \$\endgroup\$
    – Ilmari Karonen
    Commented Mar 7, 2014 at 10:26
  • 1
    \$\begingroup\$ Wouldn't this be a Mandoline quine, not a Guillotine? Guillotines make one clean, generally fatal, cut and the head rolls away. Mandolines make with the many evenly spaced slices. :) \$\endgroup\$
    – Jonathan Van Matre
    Commented Mar 7, 2014 at 21:45

12 Answers 12

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26
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PHP, 4 chars − 15% − 20% = 2.72 2.6 points

ABCD

Yes, PHP is a Turing-complete language. Nobody said I have to use any of its actual programming features. ;-)

Edit: Changed the score based on the clarification that bonuses are additive, not multiplicative.

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4
  • \$\begingroup\$ This works in ASP, possibly. \$\endgroup\$
    – Ismael Miguel
    Commented Mar 7, 2014 at 14:03
  • 2
    \$\begingroup\$ @n̴̖̋h̷͉̃a̷̭̿h̸̡̅ẗ̵̨́d̷̰̀ĥ̷̳ I give up. :P \$\endgroup\$
    – Jwosty
    Commented Mar 8, 2014 at 4:35
  • 22
    \$\begingroup\$ Actually, use of PHP's actual programming features is discouraged. \$\endgroup\$
    – Rhymoid
    Commented Mar 8, 2014 at 18:21
  • 3
    \$\begingroup\$ This is not a proper quine. Still a good answer, though \$\endgroup\$
    – MilkyWay90
    Commented Apr 6, 2019 at 18:21
14
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TI BASIC 4 - 35% = 2.6

I might understand them wrong, but I think I am also eligible for the -15% and the -20% bonusses, meaning I have the lowest possible score.

I can write the program:

123i

which will output 123i where i is of course the imaginary unit. When you remove the 1st and the 3rd character all that remains is 2i which outputs 2i

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5
  • \$\begingroup\$ Not quite... '12i' will output '12i' and '2' will output '2' for a minimum score of 1.95. \$\endgroup\$
    – intx13
    Commented Mar 7, 2014 at 11:33
  • \$\begingroup\$ Actually, '2i' scores 1.3, and if the empty program is considered a quine, 'i' scores 0.65. \$\endgroup\$
    – intx13
    Commented Mar 7, 2014 at 11:36
  • 4
    \$\begingroup\$ @intx13: "Answers must be at least 4 characters long." \$\endgroup\$
    – Ilmari Karonen
    Commented Mar 7, 2014 at 14:02
  • \$\begingroup\$ Ah, I missed that! \$\endgroup\$
    – intx13
    Commented Mar 7, 2014 at 18:14
  • \$\begingroup\$ Beat me to it ;) \$\endgroup\$
    – Timtech
    Commented Mar 8, 2014 at 0:40
14
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Python - 95

Great challenge. I thought this was pretty clever, and actually a legit solution!

00;"#";print(open(__file__).read())
0#;XpXrXiXnXtX(XoXpXeXnX(X_X_XfXiXlXeX_X_X)X.XrXeXaXdX(X)X)
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3
  • 1
    \$\begingroup\$ Nice! Note this technically doesn't work as-is since you end up deleting the newline when making the alternate quine. requires a tad bit of tweaking IOW \$\endgroup\$
    – Claudiu
    Commented Mar 7, 2014 at 5:44
  • 3
    \$\begingroup\$ @Claudiu Well I guess it depends on whether OP considers newline a character. If so, you can just add a newline between each line. 96 chars \$\endgroup\$
    – qwr
    Commented Mar 7, 2014 at 5:47
  • 1
    \$\begingroup\$ Of course a newline is a character... \$\endgroup\$
    – mbomb007
    Commented Dec 13, 2016 at 21:28
11
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Golfscript, 5 points

{hai}

is a function that, when executed, will run the (non-existing) function hai. It's not executed, however, but rather printed when the program ends - including the outer brackets. Removing each other character yields:

{a}

Lame, I know :-)

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11
  • \$\begingroup\$ I believe you qualify for both bonuses, too: your program does not read its own source code, and {} is a quine too. \$\endgroup\$
    – Ilmari Karonen
    Commented Mar 7, 2014 at 10:21
  • \$\begingroup\$ @IlmariKaronen it's hard to tell what counts as reading own source code. Does unevaluating functions count? Does evaluating strings count? As for the other bonus - maybe it's just badly worded, but I read "remove every four characters" as "keep every fifth character", which would leave me with one bracket only (though {ab0} qualifies if 0 can be the one that's kept) \$\endgroup\$
    – John Dvorak
    Commented Mar 7, 2014 at 10:40
  • \$\begingroup\$ It's indeed badly worded, but the example suggests it means "keep every fourth character". Anyway, as you note, {ab0} qualifies either way. \$\endgroup\$
    – Ilmari Karonen
    Commented Mar 7, 2014 at 10:44
  • \$\begingroup\$ It seems {hi} also works, will be shorter (4 chars), and will also qualify for all bonuses. (Seems the script {i evaluates to {i for some reason...) \$\endgroup\$
    – Claudiu
    Commented Mar 7, 2014 at 16:59
  • \$\begingroup\$ @Claudiu {i produces an extra closing curly for me \$\endgroup\$
    – John Dvorak
    Commented Mar 7, 2014 at 19:02
9
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HQ9+ - 4 * 7.5 * 0.8 = 24 points

Q+++

Still a quine with every second character:

Q+

...and every fifth:

Q

Sorry, I couldn't resist. :)

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7
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HTML/Markdown, 4*7.5 = 30

HHHH

I admit this is lame, but it doesn't really go against any rule in the question. Except that HTML/Markdown may not be considered a real programming language.

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7
  • \$\begingroup\$ I suppose I didn't specify that programs that can't be split any smaller aren't valid. Revising challenge... \$\endgroup\$
    – Jwosty
    Commented Mar 7, 2014 at 5:38
  • \$\begingroup\$ @Jwosty: then "HHHH" in HTML would win. Note 5555 doesn't work because it has no alphabetic character \$\endgroup\$
    – Claudiu
    Commented Mar 7, 2014 at 5:42
  • \$\begingroup\$ You need an alphabetic character. \$\endgroup\$
    – qwr
    Commented Mar 7, 2014 at 5:43
  • \$\begingroup\$ @qwr: Forgot that when looking at GolfScript. Removed. \$\endgroup\$
    – n̴̖̋h̷͉̃a̷̭̿h̸̡̅ẗ̵̨́d̷̰̀ĥ̷̳
    Commented Mar 7, 2014 at 5:44
  • \$\begingroup\$ Hmm... I suppose that this valid :P \$\endgroup\$
    – Jwosty
    Commented Mar 7, 2014 at 5:50
5
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!/bin/sh

I liked qwr's solution so much, I shamelessly made a port for POSIX shell. Please don't save it into a filename containing spaces.

: '#';cat $0

#c a t   $ 0

Start removing at character number 1, and count newlines as characters. The second quine is of course:

 #;a 0
cat $0

Please upvote qwr's answer instead of this one!

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0
3
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Bash, 23

Newline is a character!

Some messy comment work, so that when every other character starting from the first is removed, the comment becomes code and the code becomes a comment:

#cRaRtR R$R0R R#
cat $0

After every other character (including the new line) is removed:

cat $0 #ct$
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4
  • \$\begingroup\$ it's not a quine if it reads its own source though. \$\endgroup\$
    – daniero
    Commented Apr 13, 2014 at 14:58
  • \$\begingroup\$ @daniero "-15% if the solution does not read its source from anywhere in any form" implies that you are allowed to read the program's source (but you don't get the bonus) \$\endgroup\$
    – user16402
    Commented Apr 13, 2014 at 15:39
  • \$\begingroup\$ @daniero oh i looked on wikipedia I suppose it is cheating... but it's code-golf \$\endgroup\$
    – user16402
    Commented Apr 13, 2014 at 15:44
  • \$\begingroup\$ I always upvote cats! \$\endgroup\$
    – Antonio Ragagnin
    Commented Apr 13, 2014 at 18:29
3
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Vyxal, 8 bytes -15% = 6.8

` I,` I,

Try it Online!

Every other char

`I`I

Try it Online!

Explanation :

` I,`    # push ` I,`
      I  # quote and prepend
       , # print

`I`  # push `I`
   I # quote and prepend
     # implicit output
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2
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Brainf**k, 37 - 15% = 31.45

Abusing the Portable Brainfuck Interpreter

+A[B-C<D+E]F-GÿH<I<J<K<L<M<N<O[P.Q>R]

Start removing from the second character.

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4
  • \$\begingroup\$ When i run this I get B-C<D+E]F-GÿH<I<J<K<L<M<N<O[P.Q>R] as output so it's lacknig some characters. \$\endgroup\$
    – Sylwester
    Commented Mar 8, 2014 at 10:57
  • \$\begingroup\$ Is it Brainfuck, or a particular dialect of Brainfuck that only works on one interpreter? \$\endgroup\$
    – Criticizing Israel not allowed
    Commented Mar 8, 2014 at 10:57
  • \$\begingroup\$ @immibis It's regular (those capital letters can be spaces or symbols or anything). However, you must use the portable interpreter linked from the answer. \$\endgroup\$
    – Timtech
    Commented Mar 8, 2014 at 12:28
  • 1
    \$\begingroup\$ The first part goes left until it finds the ÿ and the linked interpreter happens to store the code 5000 bytes before the start of the data tape. That's hardly portable Brainfuck. \$\endgroup\$
    – Criticizing Israel not allowed
    Commented Mar 8, 2014 at 12:40
2
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Python 3, 145 94 bytes -15% : Score = 79.9

s ="'psr=i%nrt;(p'rsi n=t%(rs;%e%xse)c;(xsc[s11:::2  2']; p)r'i%nst)(#s#%#s#)";exec(s[1:: 2] )

Try it online!

every other char:

s='s=%r;print(s%%s);xcs1:2 ';print(s%s);xcs1:2

Try it online!

How it works :

The ugly string is the blending of :

  • print('s =%r;exec(s[1::2 ] )'%s)#### for the normal quine
  • 's=%r;print(s%%s);xcs1:2 ';print(s%s) for the every-other-char quine

xcs1:2 is an annotation and doesn't throw any error as the part after the semicolumn can compile. Otherwise it would throw a SyntaxError and the program wouldn't run at all.

Python 3, with reading code source: 70 62 bytes

s ="p-r-i-n-t-(-*-o-p-e-n-(-_-_-f-i-l-e-_-_-)-)";exec(s[::2] )

Try it online!

every other char:

s=print(*open(__file__));xcs:2

Try it online!

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0
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HQ9+T, - 4 * 0.8 = 3.2 points

qqqq

It's a valid quine (ish) and a quine every second and fifth char. I couldn't resist . . . .

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