A string only containing the following characters:
abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789.?! (space at the end) and two special characters (_ and |)


Mirror the text based on the position(s) of the _ and |.
_ mirrors horizontally and | mirrors vertically.

Mirroring process

  • The first _ indicates the start of the mirroring of that substring, the second _ the end.
  • If just one _ is present, you can continue on until the end of the string.
  • If more then two _ are present, the same process repeats.
  • There can only be one | in the string, and this reversed the first substring and removes the second substring.

abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789.?! (space at the end) will be converted to ɐqɔpǝɟɓɥıɾʞlɯuodbɹsʇnʌʍxʎz∀𐐒ƆᗡƎℲ⅁HIſ⋊⅂WNOԀΌᴚS⊥∩ΛMX⅄Z0⇂ᘔƐ߈ϛ9ㄥ86˙¿¡ (space at the end) when it is mirrored by _ (click the link for the unicode values - requires unicode v8.0+).

Example input 1: _Will I be mirrored?!
Output 1: Mıll I qǝ ɯıɹɹoɹǝp¿¡

Example input 2: Wi_ll I be mi_rrored?!
Output 2: Will I qǝ ɯırrored?!

When it is mirrored by | we simply reverse the substring from 0 to index-of-|.

Example input 1: Will I be mirror|ed?!
Output 1: Will I be mirrorrorrim eb I lliW

Both mirrors (_ and |) can be present in the string.

General rules:

  • This is , so shortest answer in bytes wins.
    Don't let code-golf languages discourage you from posting answers with non-codegolfing languages. Try to come up with an as short as possible answer for 'any' programming language.
  • Standard rules apply for your answer, so you are allowed to use STDIN/STDOUT, functions/method with the proper parameters, full programs. Your call.
  • Default Loopholes are forbidden.
  • If possible, please add a link with a test for your code.
  • Also, please add an explanation if necessary.

Test cases:

_Will I be mirrored?!                          ->   Mıll I qǝ ɯıɹɹoɹǝp¿¡
Wi_ll I be mi_rrored?!                         ->   Will I qǝ ɯırrored?!
Will I be mirror|ed?!                          ->   Will I be mirrorrorrim eb I lliW
This_ is a test_ cont_aining bo|t_h mirrors.   ->   This ıs ɐ ʇǝsʇ contɐıuıuɓ qooq ɓuıuıɐtnoc ʇsǝʇ ɐ sı sihT
0_1_2_3_4_5|_6_7_8_9                           ->   0⇂2Ɛ4ϛϛ4Ɛ2⇂0
  • 2
    \$\begingroup\$ feature request -- Change the title to "The world is like a Mirror: smile and it'll sɯıןǝ qɐɔʞ" ;-) \$\endgroup\$ Sep 1, 2016 at 14:42
  • \$\begingroup\$ @TimmyD ᗡouǝ ;) \$\endgroup\$ Sep 1, 2016 at 14:48
  • \$\begingroup\$ @TimmyD In my country mirrors work like this: "smile ɘlimƨ", not "smile sɯıןǝ" :) The title should be "The world is like a Mirror: smile and it'll ɘlimƨ back" \$\endgroup\$
    – tmaj
    Sep 2, 2016 at 0:38
  • 1
    \$\begingroup\$ In the first line you should probably mention that spaces can appear in the input, too. \$\endgroup\$ Sep 2, 2016 at 7:18

7 Answers 7


Pyth - 174 bytes

Can prolly save with base compression or something cuz of unicode(this is only 119 chars)

u?qH\_&=hZG+G@@c2K+s+rB;1UT".?! ɐqɔpǝɟɓɥıɾʞlɯuodbɹsʇnʌʍxʎz∀𐐒ƆᗡƎℲ⅁HIſ⋊⅂WNOԀΌᴚS⊥∩ΛMX⅄Z0⇂ᘔƐ߈ϛ9ㄥ86˙¿¡ "ZxKH?}\|zs_Bhcz\|zk

Test Suite.


JavaScript (ES6), 308 bytes

s=>s[r='replace'](/_.*?(_|$)/g,m=>m[r](/./g,c=>'| ɐqɔpǝɟɓɥıɾʞlɯuodbɹsʇnʌʍxʎz∀ƆᗡƎℲ⅁HIſ⋊⅂WNOԀΌᴚS⊥∩ΛMX⅄Z0⇂ᘔƐ߈ϛ9ㄥ86˙¿¡𐐒'['| abcdefghijklmnopqrstuvwxyzACDEFGHIJKLMNOPQRSTUVWXYZ0123456789.?!B'.indexOf(c)]||''))[r](/(.*)\|.*/,(m,t)=>t+[...t].reverse().join``)


var solution =

      '| ɐqɔpǝɟɓɥıɾʞlɯuodbɹsʇnʌʍxʎz∀ƆᗡƎℲ⅁HIſ⋊⅂WNOԀΌᴚS⊥∩ΛMX⅄Z0⇂ᘔƐ߈ϛ9ㄥ86˙¿¡𐐒'
        ['| abcdefghijklmnopqrstuvwxyzACDEFGHIJKLMNOPQRSTUVWXYZ0123456789.?!B'

var testCases = [
  '_Will I be mirrored?!',
  'Wi_ll I be mi_rrored?!',
  'Will I be mirror|ed?!',
  'This_ is a test_ cont_aining bo|t_h mirrors.',
tests.textContent = testCases.map((c) => c + '   =>   ' + solution(c)).join('\n');
<input type="text" oninput="result.textContent=solution(this.value)" value="This_ is a test_ cont_aining bo|t_h mirrors." /><pre id="result"></pre><pre id="tests"></pre>


PERL 243

242 + 1 for -p

$h=(split'\|',$_)[0];$_=$h.reverse$h if($_=~/\|/);for$b(split'_',$_){$b=~y/A-Za-z0-9.?!/ɐqɔpǝɟɓɥıɾʞlɯuodbɹsʇnʌʍxʎz∀𐐒ƆᗡƎℲ⅁HIſ⋊⅂WNOԀΌᴚS⊥∩ΛMX⅄Z0⇂ᘔƐ߈ϛ9ㄥ86˙¿¡/ if($f);$\.=$b;$f=!$f;}$_='';


$reverse = (split('\|', $_))[0];
$_ = $reverse . reverse($reverse) if($_=~/\|/);

for $block (split '_', $_) {
    $block =~ y/A-Za-z0-9.?!/ɐqɔpǝɟɓɥıɾʞlɯuodbɹsʇnʌʍxʎz∀𐐒ƆᗡƎℲ⅁HIſ⋊⅂WNOԀΌᴚS⊥∩ΛMX⅄Z0⇂ᘔƐ߈ϛ9ㄥ86˙¿¡/ if($flip);


$ perl -p mirror.pl <<<'Will I be mirror|ed?!'
Will I be mirrorrorrim eb I lliW

I'm 99% sure this works, but most of the upsidedown characters don't display correctly on my system. I tested it by using a different range of character, e.g. .?! -> %^& instead of .?! -> ˙¿¡.


R, 362 362 342 339 bytes

Edit 1: I found a bug in my original (failed if there were no _ in input), fixed it, golfed some more, and I'm back at 362 where I started!

Edit 2: Golfed away 20 byes by replacing "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789.?! " with paste(c(letters,LETTERS,0:9,".?! "),collapse="")

Edit 3: Removing some extra whitespace shaves off another 3 bytes.

if(l(i)-1)i[v]=chartr(paste(c(letters,LETTERS,0:9,".?! "),collapse=""),"ɐqɔpǝɟɓɥıɾʞlɯuodbɹsʇnʌʍxʎz∀𐐒ƆᗡƎℲ⅁HIſ⋊⅂WNOԀΌᴚS⊥∩ΛMX⅄Z0⇂ᘔƐ߈ϛ9ㄥ86˙¿¡ ",i[v<-seq(2,l(i),2)])


p=strsplit               # Aliases for common functions
i=p(readline(),"_")[[1]] # Read input, split by _s. Now every even-indexed substring is one that we must
                         # mirror vertically. (R indexes from 1.)
if(l(i)-1)               # If there are any _s,
  i[v]=chartr("paste(c(letters,LETTERS,0:9,".?! "),collapse=""),
  "ɐqɔpǝɟɓɥıɾʞlɯuodbɹsʇnʌʍxʎz∀𐐒ƆᗡƎℲ⅁HIſ⋊⅂WNOԀΌᴚS⊥∩ΛMX⅄Z0⇂ᘔƐ߈ϛ9ㄥ86˙¿¡ ",
  i[v<-seq(2, l(i), 2)]
)                 # Flip the characters in the vertically-mirrored substrings
i=unlist(p(i,"")) # Split each substring into a single character object
if(l(b<-which(i=="|")-1)) # If there is a |,
  i[1:b+b]=rev(i[1:b])    # insert the reversed characters at the end of the list
cat(i,sep="")             # Print output

Javascript (ES5), 344 340 bytes

function mirror(a){d=[];~a.indexOf("|")&&(a=a.split("|")[0]+a.split("|")[0].split("").reverse().join(""));for(var c=!1,b=0;b<a.length;++b)"_"==a[b]&&(c=!c),d[b]=c?"zʎxʍʌnʇsɹbdouɯlʞɾᴉɥɓɟǝpɔqɐZ⅄XMΛ∩⊥SᴚΌԀONW⅂⋊ſIH⅁ℲƎᗡƆᗺⱯ068ㄥ95߈Ɛᘔ⇂˙¿¡ "["zyxwvutsrqponmlkijhgfedcbaZYXWVUTSRQPNOMLKIJHGFEDCBA0987654321.?! ".indexOf(a[b])]:a[b];return d.join("")}


function mirror_u(s){return "zʎxʍʌnʇsɹbdouɯlʞɾᴉɥɓɟǝpɔqɐZ⅄XMΛ∩⊥SᴚΌԀONW⅂⋊ſIH⅁ℲƎᗡƆᗺⱯ068ㄥ95߈Ɛᘔ⇂˙¿¡ "["zyxwvutsrqponmlkijhgfedcbaZYXWVUTSRQPNOMLKIJHGFEDCBA0987654321.?! ".indexOf(s)]};

function mirror(str){var b=[];
    var is_mirrored=false;
    for(var i=0;i<str.length;++i){
    return b.join("");

EDIT: Longer working code, that is mirrored | by character 341.

function mirror(a){d=[];~a.indexOf("|")&&(a=a.split("|")[0]+a.split("|")[0].split("").reverse().join(""));for(var c=!1,b=0;b<a.length;++b)"_"==a[b]&&(c=!c),d[b]=c?"zʎxʍʌnʇsɹbdouɯlʞɾᴉɥɓɟǝpɔqɐZ⅄XMΛ∩⊥SᴚΌԀONW⅂⋊ſIH⅁ℲƎᗡƆᗺⱯ068ㄥ95߈Ɛᘔ⇂˙¿¡ "["zyxwvutsrqponmlkijhgfedcbaZYXWVUTSRQPNOMLKIJHGFEDCBA0987654321.?! ".indexOf(a[b])]:a[b];return d.join("")}//})""(nioj.d nruter;]b[a:])]b[a(fOxedni." !?.1234567890ABCDEFGHJIKLMONPQRSTUVWXYZabcdefghjiklmnopqrstuvwxyz"[" ¡¿˙⇂ᘔƐ߈59ㄥ860ⱯᗺƆᗡƎℲ⅁HIſ⋊⅂WNOԀΌᴚS⊥∩ΛMX⅄Zɐqɔpǝɟɓɥᴉɾʞlɯuodbɹsʇnʌʍxʎz"?c=]b[d,)c!=c(&&]b[a=="_")b++;htgnel.a<b;0=b,1!=c rav(rof;))""(nioj.)(esrever.)""(tilps.]0[)"|"(tilps.a+]0[)"|"(tilps.a=a(&&)"|"(fOxedni.a~;][=d{)a(rorrim noitcnuf
  • \$\begingroup\$ The 𐐒 character takes up two UTF-16 code units, but you don't seem to be taking this into account. Does the W in the first test case come out correctly? \$\endgroup\$
    – user81655
    Sep 1, 2016 at 15:11
  • \$\begingroup\$ The characters are all UTF-8. All test cases give the correct output. \$\endgroup\$ Sep 1, 2016 at 15:14
  • \$\begingroup\$ Oh, it seems you're using code point U+15FA for the upside-down B. The one in the challenge is code point U+10412. \$\endgroup\$
    – user81655
    Sep 1, 2016 at 15:21
  • \$\begingroup\$ I used the characters from the linked wikipedia page, I just copied them into my editor. \$\endgroup\$ Sep 1, 2016 at 15:25

Retina, 176 bytes




Try it online! (The first line enables a linefeed-separated test suite.)


Java 7, 504 502 bytes

import java.util.*;String c(String s){Map m=new HashMap();int i=0,j;while(i<67)m.put("abcdefghijklmnopqrstuvwxyzABBCDEFGHIJKLMNOPQRSTUVWXYZ0123456789.?! ".charAt(i),"ɐqɔpǝɟɓɥıɾʞlɯuodbɹsʇnʌʍxʎz∀𐐒ƆᗡƎℲ⅁HIſ⋊⅂WNOԀΌᴚS⊥∩ΛMX⅄Z0⇂ᘔƐ߈ϛ9ㄥ86˙¿¡ ".charAt(i++));String q=s.split("\\|")[0],z[]=(q+(s.equals(q)?"":new StringBuffer(q).reverse()+"")).split("_"),r="";for(i=-1;++i<z.length;){q="";for(char c:z[i].toCharArray())q+=m.get(c);r+=i%2<1?z[i]:q;}return r;}

Of course I'll have to answer my own challenge again. And.. it's long.. xD

Ungolfed & test cases:

Try it here.

import java.util.*;
class M{
  static String c(String s){
    Map m = new HashMap();
    int i = 0,
    while(i < 67){
      m.put("abcdefghijklmnopqrstuvwxyzABBCDEFGHIJKLMNOPQRSTUVWXYZ0123456789.?! ".charAt(i),
          "ɐqɔpǝɟɓɥıɾʞlɯuodbɹsʇnʌʍxʎz∀𐐒ƆᗡƎℲ⅁HIſ⋊⅂WNOԀΌᴚS⊥∩ΛMX⅄Z0⇂ᘔƐ߈ϛ9ㄥ86˙¿¡ ".charAt(i++));
    String q = s.split("\\|")[0],
           z[] = (q + (s.equals(q)
                        ? ""
                        : new StringBuffer(q).reverse() + "")
           r = "";
    for(i = -1; ++i < z.length;){
      q = "";
      for(char c : z[i].toCharArray()){
        q += m.get(c);
      r += i%2 < 1
            ? z[i]
            : q;
    return r;

  public static void main(String[] a){
    System.out.println(c("_Will I be mirrored?!"));
    System.out.println(c("Wi_ll I be mi_rrored?!"));
    System.out.println(c("Will I be mirror|ed?!"));
    System.out.println(c("This_ is a test_ cont_aining bo|t_h mirrors."));


Mıll I qǝ ɯıɹɹoɹǝp¿¡
Will I qǝ ɯırrored?!
Will I be mirrorrorrim eb I lliW
This ıs ɐ ʇǝsʇ contɐıuıuɓ qooq ɓuıuıɐtnoc ʇsǝʇ ɐ sı sihT
  • \$\begingroup\$ Suggest dropping the j variable. \$\endgroup\$
    – ceilingcat
    Nov 13, 2020 at 6:17

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