Quinary is like binary, except that 1 is represented by the text of the program, and 0 is represented as the backwards text of the program.

The Fibonacci Sequence is the well known sequence

F(0) = 0, F(1) = 1, F(n) = F(n - 1) + F(n - 2)

Write a program that takes some input n and outputs the nth fibonacci number in quinary.

Standard code golf rules apply.

  • \$\begingroup\$ Can we read program code using filesystem IO? \$\endgroup\$ Jan 31, 2016 at 7:36
  • \$\begingroup\$ @HannesKarppila That's considered a standard loophole for quines. \$\endgroup\$
    – Alex A.
    Jan 31, 2016 at 7:37
  • \$\begingroup\$ Yes it is, but actually question does not use word quine, so I asked. Of course it usually is, but I wanted to be sure if that applies here. \$\endgroup\$ Jan 31, 2016 at 7:40
  • \$\begingroup\$ @Mego I believe you are supposed to output F(n) in binary, but with the reversed program for 0 and the program code for 1. So if your code was 1234, and the input was 4, you'd output 12341234 (11), and for 5, you'd output 123443211234 (101). \$\endgroup\$
    – es1024
    Jan 31, 2016 at 7:51
  • 1
    \$\begingroup\$ Is the program allowed to be a palindrome? (Same backwards and forwards) \$\endgroup\$
    – xenia
    Jan 31, 2016 at 9:17

5 Answers 5


CJam, 30 bytes


Try it online!

How it works

{                          }_~  Define a code block, and push and execute a copy.
 s                              Convert the original code block to a string.
  "_~"+                         Append "_~" to the string.
       UXri                     Push 0, 1 and an integer N from STDIN.
           {   }*               Do N times:
            _                     Push a copy of the topmost integer. 
             @                    Rotate the bottom-most integer on top of it.
              +                   Push the sum of the copy and the rotated integer.
                 ;              Discard the topmost stack item, i.e., F(N+1).
                  2b            Convert the remaining stack item to base 2.
                    Wfe|        Logical OR all binary digits with -1.
                                This turns 0's into -1's.
                        \f%     For each binary digits A, take each Ath item of the
                                generated string.
                                This pushes the string itself for A = 1, and the
                                reversed string for A = -1.

Python, 226 bytes

s='s=%r;a,b=0,1;exec"a,b=b,a+b;"*input();print"".join(map(lambda i:(s%%s)*int(i)+(s%%s)[::-1]*(1-int(i)),bin(a)[2:]))';a,b=0,1;exec"a,b=b,a+b;"*input();print"".join(map(lambda i:(s%s)*int(i)+(s%s)[::-1]*(1-int(i)),bin(a)[2:]))

It's quite a heavy modification to the standard Python Quine. It uses a,b=0,1;exec"a,b=b,a+b;" to generate Fibonacci numbers.

  • \$\begingroup\$ I get syntax error on both python 2 and 3. \$\endgroup\$
    – k_g
    Jan 31, 2016 at 9:22
  • \$\begingroup\$ @k_g Weird, the program works for me in 2.7.3. Are you sure you copied the whole thing? \$\endgroup\$
    – xenia
    Jan 31, 2016 at 9:25
  • 1
    \$\begingroup\$ Oh, whoops, it works. I was using python3 in both my tests. Who knew python -> python3? \$\endgroup\$
    – k_g
    Jan 31, 2016 at 9:29

𝔼𝕊𝕄𝕚𝕟, 24 chars / 44 bytes


Try it here (Firefox only).


Standard quine framework: ⟮ɕṡ+ᶈ0

⟮Мȫïⓑⓢⓜ+$?(a=ɕṡ+ᶈ0):aᴙ)⨝ // implicit: ï=input
⟮                           // copy block start
 Мȫï                       // get nth Fibonacci number
    ⓑⓢⓜ                  // convert to binary, split along chars, map
         +$?               // is mapitem truthy?
            (a=ɕṡ+ᶈ0)      // if so, replace w/ quine as is
                     :aᴙ)  // else replace w/ reverse quine
                         ⨝ // join
                           // implicit output
  • \$\begingroup\$ What's ɕṡ+ᶈ0? Is that a quine builtin? \$\endgroup\$
    – lirtosiast
    Feb 1, 2016 at 2:03
  • \$\begingroup\$ Naw, ɕṡ refers to character and ᶈ0 is a string representation of the contents of the copy block. \$\endgroup\$ Feb 1, 2016 at 2:05
  • \$\begingroup\$ is the quine function, which isn't used/allowed here. \$\endgroup\$ Feb 1, 2016 at 2:06
  • \$\begingroup\$ That's a good way to quine without a quine builtin. \$\endgroup\$
    – lirtosiast
    Feb 1, 2016 at 2:08
  • \$\begingroup\$ Found it by accident. \$\endgroup\$ Feb 1, 2016 at 2:09

Javascript ES6, 121 bytes


I'm looking for ways to shorten the Fibonacci function...


Python 3.8 (pre-release), 113 bytes

exec(s:="f=lambda x:x<2or f(x-1)+f(x-2)\nfor i in f'{f(int(input())):b}':print(('exec(s:=%r)'%s)[::2*int(i)-1])")

Try it online!


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