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In this challenge, you will be "reversing" the alphabet or swapping a-z with z-a

Because this transformation makes the output look like some foreign language, your code will need to be as short as possible.



Programming Puzzles & Code Golf
Kiltiznnrmt Kfaaovh & Xlwv Tlou

Hello, World!
Svool, Dliow!


  • The input may contain multiple lines, and will be ASCII-only
  • No additional whitespace should be added to the output
  • Case must be preserved


var QUESTION_ID=68504,OVERRIDE_USER=40695;function answersUrl(e){return""+QUESTION_ID+"/answers?page="+e+"&pagesize=100&order=desc&sort=creation&site=codegolf&filter="+ANSWER_FILTER}function commentUrl(e,s){return""+s.join(";")+"/comments?page="+e+"&pagesize=100&order=desc&sort=creation&site=codegolf&filter="+COMMENT_FILTER}function getAnswers(){jQuery.ajax({url:answersUrl(answer_page++),method:"get",dataType:"jsonp",crossDomain:!0,success:function(e){answers.push.apply(answers,e.items),answers_hash=[],answer_ids=[],e.items.forEach(function(e){e.comments=[];var s=+e.share_link.match(/\d+/);answer_ids.push(s),answers_hash[s]=e}),e.has_more||(more_answers=!1),comment_page=1,getComments()}})}function getComments(){jQuery.ajax({url:commentUrl(comment_page++,answer_ids),method:"get",dataType:"jsonp",crossDomain:!0,success:function(e){e.items.forEach(function(e){e.owner.user_id===OVERRIDE_USER&&answers_hash[e.post_id].comments.push(e)}),e.has_more?getComments():more_answers?getAnswers():process()}})}function getAuthorName(e){return e.owner.display_name}function process(){var e=[];answers.forEach(function(s){var r=s.body;s.comments.forEach(function(e){OVERRIDE_REG.test(e.body)&&(r="<h1>"+e.body.replace(OVERRIDE_REG,"")+"</h1>")});var a=r.match(SCORE_REG);a&&e.push({user:getAuthorName(s),size:+a[2],language:a[1],link:s.share_link})}),e.sort(function(e,s){var r=e.size,a=s.size;return r-a});var s={},r=1,a=null,n=1;e.forEach(function(e){e.size!=a&&(n=r),a=e.size,++r;var t=jQuery("#answer-template").html();t=t.replace("{{PLACE}}",n+".").replace("{{NAME}}",e.user).replace("{{LANGUAGE}}",e.language).replace("{{SIZE}}",e.size).replace("{{LINK}}",,t=jQuery(t),jQuery("#answers").append(t);var o=e.language;/<a/.test(o)&&(o=jQuery(o).text()),s[o]=s[o]||{lang:e.language,user:e.user,size:e.size,}});var t=[];for(var o in s)s.hasOwnProperty(o)&&t.push(s[o]);t.sort(function(e,s){return e.lang>s.lang?1:e.lang<s.lang?-1:0});for(var c=0;c<t.length;++c){var i=jQuery("#language-template").html(),o=t[c];i=i.replace("{{LANGUAGE}}",o.lang).replace("{{NAME}}",o.user).replace("{{SIZE}}",o.size).replace("{{LINK}}",,i=jQuery(i),jQuery("#languages").append(i)}}var ANSWER_FILTER="!t)IWYnsLAZle2tQ3KqrVveCRJfxcRLe",COMMENT_FILTER="!)Q2B_A2kjfAiU78X(md6BoYk",answers=[],answers_hash,answer_ids,answer_page=1,more_answers=!0,comment_page;getAnswers();var SCORE_REG=/<h\d>\s*([^\n,]*[^\s,]),.*?(\d+)(?=[^\n\d<>]*(?:<(?:s>[^\n<>]*<\/s>|[^\n<>]+>)[^\n\d<>]*)*<\/h\d>)/,OVERRIDE_REG=/^Override\s*header:\s*/i;
body{text-align:left!important}#answer-list,#language-list{padding:10px;width:290px;float:left}table thead{font-weight:700}table td{padding:5px}
<script src=""></script> <link rel="stylesheet" type="text/css" href="//"> <div id="answer-list"> <h2>Leaderboard</h2> <table class="answer-list"> <thead> <tr><td></td><td>Author</td><td>Language</td><td>Size</td></tr></thead> <tbody id="answers"> </tbody> </table> </div><div id="language-list"> <h2>Winners by Language</h2> <table class="language-list"> <thead> <tr><td>Language</td><td>User</td><td>Score</td></tr></thead> <tbody id="languages"> </tbody> </table> </div><table style="display: none"> <tbody id="answer-template"> <tr><td>{{PLACE}}</td><td>{{NAME}}</td><td>{{LANGUAGE}}</td><td>{{SIZE}}</td><td><a href="{{LINK}}">Link</a></td></tr></tbody> </table> <table style="display: none"> <tbody id="language-template"> <tr><td>{{LANGUAGE}}</td><td>{{NAME}}</td><td>{{SIZE}}</td><td><a href="{{LINK}}">Link</a></td></tr></tbody> </table>

This is so shortest code in bytes wins

share|improve this question
+1 for the justification "Because this transformation makes the output look like some foreign language, your code will need to be as short as possible." – cat Jan 3 at 19:31
Some Trivia: this is Atbash, a known cipher as old as the bible. – Jacob Jan 4 at 9:21
"Because this transformation makes the output look like some foreign language, your code will need to be as short as possible." What kind of logic is that?? Because your description raises about as much question marks as if it was written in some foreign language your answer to this question should be in intelligible natural language and some verbosity is appreciated. – Bart Jan 5 at 22:03

36 Answers 36

up vote 11 down vote accepted

Pyth, 8 bytes


@xnor suggested this simpler approach on @FryAmTheEggman's Pyth answer, then I translated it to Pyth.

This uses the handy behavior of X (translate) when given only two arguments: it translates from the second argument to the reversed second argument. We do this first with the lowercase alphabet (G), and then with uppercased G.

share|improve this answer

C, 59 bytes

Sorry for bringing up C again, but I was a bit disappointed to see only C functions here. I was under the impression OP was looking for a usable product.


Compiled on Ubuntu 14.04 with a simple:

cc swalpha.c

The resulting executable reads any number of lines from stdin, and writes the result to stdout.

Thanks to so many of the other posters for the XOR trick.

share|improve this answer

CJam, 17 bytes

I wanted to help GamrCorps golf his CJam solution, but the result ended up so different that I decided to make a separate answer.


Try it online.


q     e# Read all input.
'[,   e# Get a character range from the null byte up to and including "Z".
_el   e# Duplicate and convert to lowercase.
^     e# Symmetric set difference. Due to the lowercase operation only letters will not
      e# appear in both sets, and so we get a string with all uppercase letters followed
      e# by all lowercase letters, i.e "".
_W%   e# Duplicate and reverse. Gives: "zyx...cbaZYX...CBA".
32f^  e# Take each character XOR 32 which swaps the case, so now we have:
      e#                               ""
er    e# Transliterate: substitute each character in the first string with the correspoding
      e# character in the second string.
share|improve this answer
Well, I'm glad you were trying to help! That is the solution that I was trying to make, I just couldn't figure out the XOR. Nice Job! – GamrCorps Jan 3 at 20:19
SE's syntax highlighting hates esolangs. – Cyoce Jan 5 at 6:58

Retina, 17 14 13 bytes




\             # This suppresses the trailing linefeed
 T            # Switches to transliterate mode
  `w          # w is short for _0-9A-Za-z
    `_d       # d is short for 0-9
       Z-Az-a # Z-Az-a

This does some magic stuff and completes the task.

Try it here.

share|improve this answer
Lucky you that I recently added \. Unlucky you that I didn't get around to adding character classes for letters and reversed character classes yet. – Martin Ender Jan 3 at 20:19
@MartinBüttner Very lucky indeed, that almost invalidated my answer :) – Adnan Jan 3 at 20:36
For reference, as of Retina 0.7.2 you could do \T`lL`RlRL. – Martin Ender Jan 7 at 11:11

JavaScript (ES6), 69 67 bytes


Uses the same strategy as my Japt answer:

x=>x.replace(/[A-Z]/gi,C=>   // Replace each letter C with
 String.fromCharCode(        //  the character with char code
  C.charCodeAt()+4^31))      //   the char code of C, plus 4, with the last 5 bits flipped.

Curse your incredibly long property names, JS...

share|improve this answer
+1 for mentioning JS's excruciatingly long property names. My favorite is still the infamous document.getElementById – Cyoce Jan 5 at 7:04
@Cyoce Try document.getElementsByClassName or, on Firefox and Chrome, document.DOCUMENT_POSITION_IMPLEMENTATION_SPECIFIC – Ismael Miguel Jan 6 at 10:28
This seems to only be 66 bytes not 67 – Downgoat Jan 6 at 23:28
@Doᴡɴɢᴏᴀᴛ You're right about that, thanks! – ETHproductions Jan 6 at 23:28
It looks like you are missing a closing bracket on the end of the golfed code. – starbeamrainbowlabs Jan 7 at 6:56

Pyth, 10 9


Thanks to Jakube for saving a byte with the new feature of ;!

Test Suite

A quick explanation: reduce starting with the input over the numbers 0 and 1. The operation to be performed is translate the lower case alphabet with either r...0 or `r...1 which are the lower and upper functions from python, respectively, applied to it, and then reversed.

share|improve this answer
9 bytes due to a new feature (not even a day old): uXGr;H)2z – Jakube Jan 3 at 20:05
Can you add an explanation? – TanMath Jan 3 at 20:20
Can't you use X with the alphabet and then with the capitalized alphabet? – xnor Jan 3 at 20:49
@xnor XXzG)rG1? That seems to work. – lirtosiast Jan 3 at 21:03
Or, maybe do X on the lowercase and uppercase alphabets concatenated, then swap case? That's probably longer, actually. – xnor Jan 3 at 21:05

C, 150 129 Bytes

void rev(char*s){int i,t;for(i=0;i<strlen(s);i++){t=s[i]+25;t=t<116?180-t:244-t;isalpha(s[i])?printf("%c",t):printf("%c",s[i]);}}

This function just converts char to int and adds the appropriate offset to the int before printing. I know it's not the shortest but I didn't see a C implementation.

Example usage


void rev(char*s){int i,temp;for(i=0;i<strlen(s);i++){temp=s[i]+25;temp=temp<116?180-temp:244-temp;isalpha(s[i])?printf("%c",temp):printf("%c",s[i]);}}

int main(){
   char *s = "hello, there";
   return 0;

UPDATE: shortened a variable name.

share|improve this answer
Welcome to Programming Puzzles and Code Golf Stack Exchange! This is a very good approach. It could be golfed more by making all variables (including temp) exactly one character long. – wizzwizz4 Jan 4 at 10:33
Ahh you are right! I will regolf this one – Danwakeem Jan 4 at 10:35
Do you think you could have a go at my challenge? Analyse your Chair – wizzwizz4 Jan 4 at 10:54
Yes it will work without the headers you just get a compiler warning @edc65 I figured since it compiles and runs it wouldn't be considered cheating but in real world use you should always include the headers. – Danwakeem Jan 4 at 16:05
107 bytes: i,t;r(char*s){for(;i<strlen(s);i++){t=s[i]+25;t=t<116?180-t:244-t;isalpha(s[i])‌​?putchar(t):putchar(s[i]);}} – Cool Guy Jan 4 at 16:29

Japt, 23 22 bytes

Ur"[A-Za-z]"_c +4^31 d

Try it online!

How it works

Ur"[A-Za-z]"_  // Take the input and replace each letter with:
 c +4          //  Take its char code and add 4. This results in
               //  the string      ""
               //  becoming        "EFG...\]^efg...|}~".
 ^31           //  XOR the result by 31. This flips its last five 5 bits.
               //  We now have     "".
 d             //  Convert back from a char code.
               // Implicit: output last expression
share|improve this answer
Nice idea (which I borrowed...) to use XOR for this – Luis Mendo Jan 4 at 1:12

Julia, 74 61 47 bytes


This is a lambda function that accepts a string and returns a string. To call it, assign it to a variable.

We match each letter using a regular expression and replace each letter with the ASCII character corresponding to 31 XOR the ASCII code for the letter, minus 4.

share|improve this answer

Seriously, 31 bytes (non-competing)


Hex Dump:


Try It Online


úúû+╗                             Put UPPERCASElowercase in reg0
     úRúûR+╝                      Put ESACREPPUesacrewol in reg1
            ,                     Fetch input.
             `             `Mεj   Map over the characters in string as list, joining result
              ;╜íu                Find 1-index of character in UPPERCASElowercase
                  W     0WX       If it is positive (present): 
                   D              Convert back to 0-index
                    ╛E            Look it up in ESACREPPUesacrewol
                      (X          Delete the original character.
                                  (Else just leave the original character unchanged.)

I just realized the spec say no additional whitespace, but there is no way to suppress trailing newlines in Seriously output, so there is no Seriously solution.

share|improve this answer
What does ESACREPPUesacrewol mean? – Downgoat Jan 3 at 20:56
@Doᴡɴɢᴏᴀᴛ UPPERCASE reversed LOWERCASE reversed – Mama Fun Roll Jan 3 at 21:01
the reversed uppercase alphabet prepended to the reversed lowercase alphabet – quintopia Jan 3 at 21:01

R, 69 bytes


This is an anonymous function. Usage:

> f=function(s)cat(chartr("a-zA-Z",rawToChar(as.raw(c(122:97,90:65))),s))
> f("Hello, World!")
Svool, Dliow!
> f("Programming Puzzles & Code Golf")
Kiltiznnrmt Kfaaovh & Xlwv Tlou
> f("This is
+ a multiline
+ example.")
Gsrh rh
z nfogrormv
share|improve this answer

Ruby, 40 bytes

New solution: Stole that bit flipping magic from some of the other posts here:


Ruby, 55 46 bytes


9 bytes off thanks to @manatwork

test run:

->s{s.gsub(/[a-z]/i){($&.ord+4^31).chr}}["Kiltiznnrmt Kfaaovh & Xlwv Tlou"]
=> "Programming Puzzles & Code Golf"
share|improve this answer

C, 64

A void function that modify the string in place.

t(char*p){for(int c;c=*p;)*p++=c>64&c<91|c>96&c<123?(c^31)-4:c;}

Test: ideone

share|improve this answer
c;t(char*p){for(;c=*p;)*p++=c>64&c<91|c>96&c<123?(c^31)-4:c;} – Cool Guy Jan 4 at 12:33
@CoolGuy right, but I don't like the global inside a function... it's just me – edc65 Jan 4 at 12:59
Isn't this 64 bytes? – Downgoat Jan 7 at 2:37
@Doᴡɴɢᴏᴀᴛ yes it is .. thanks .. – edc65 Jan 7 at 7:05

Jolf, 15 bytes

~A              I don't know what to call this, besides "dictionary replace"
  i              the input
   +plpu         previous dictionary: lower + upper alphabet
        +_p1_pu  new dictionary: reversed lower + reversed upper

Test suite, or try it with your own input

share|improve this answer
The word for this is "transliteration," FYI. – quartata Jan 4 at 18:43
@quartata Huhh! Thanks! – Cᴏɴᴏʀ O'Bʀɪᴇɴ Jan 4 at 18:43

𝔼𝕊𝕄𝕚𝕟 2, 12 chars / 26 bytes (non-competitive)


Try it here (Firefox only).

Added transliterate function after the challenge was posted.


ïĪ(ᶐ+ᶛ,ᶐᴙ+ᶛᴙ // implicit: ï=input
ïĪ(           // transliterate ï...
   ᶐ+ᶛ,       // from uppercase+lowercase alphabet...
       ᶐᴙ+ᶛᴙ  // ... to reversed uppercase+reversed lowercase alphabet
              // implicit output
share|improve this answer
I thought 𝔼𝕊𝕄𝕚𝕟 2 was going to be called 𝔼𝕊 ∞? – Downgoat Jan 3 at 22:01
No, I decided to save that for a complementary (but different) language for 𝔼𝕊𝕄𝕚𝕟. – Mama Fun Roll Jan 3 at 22:02
IIRC There is a blackboard bold 2. – Cᴏɴᴏʀ O'Bʀɪᴇɴ Jan 4 at 18:46
@ՊՓԼՃՐՊՃՈԲՍԼ Call it ESMax (in doublestruck). – mbomb007 Jan 4 at 20:35

CJam, 21 bytes


Not an optimal solution... yet... Try it online

Its hard to explain without grouping things, so here is a general explanation: gets input, pushes uppercase alphabet twice and lowercase twice, rotates things around, combines uppercase and lowercase strings, reverses one, and uses transliteration (similar to the Retina answer).

share|improve this answer
Does this output a trailing newline? – LegionMammal978 Jan 4 at 0:26
@LegionMammal978 It shouldn't unless aditsu changed how the stack is outputted. – GamrCorps Jan 4 at 0:29
@LegionMammal978 I doesn't. – Martin Ender Jan 4 at 10:05

Python 3, 195 169 168 166 bytes

Thanks to @TrangOul for -2 bytes!

How didn't I see that I could have golfed that down before?

x=__import__('string').ascii_letters;y,z=x[26:],x[:26];a,b=y[::-1],z[::-1];print(''.join(b[z.index(i)]if i in b else a[y.index(i)]if i in a else i for i in input()))

(sorta) ungolfed:

x = __import__('string').ascii_letters;
y, z = x[26: ], x[: 26];
a, b = y[::-1], z[::-1];
    if i in b
    else a[y.index(i)]
    if i in a
    else i
    for i in input()

Try it on Ideone!

share|improve this answer
You can save 2 bytes by removing the outermost [] from join. – Trang Oul Jan 4 at 13:03
@TrangOul really? It's a list comprehension so I thought it needs to be a list or else you get generator object <genexpr> at..., but I will test it – cat Jan 4 at 13:25
@TrangOul Nevermind, I learned something, thanks! – cat Jan 4 at 13:26
Any iterable [containing str values] can be passed to join() function. – Trang Oul Jan 4 at 13:42

Python, 61 bytes

lambda x:''.join([c,chr(ord(c)+4^31)][c.isalpha()]for c in x)

An anonymous function. On letters, does the reversing operation on the bit representation by adding 4, then flipping the last five bits, similar to ETHproductions' Javascript answer.

share|improve this answer

C (function), 50


This builds on all three previous C answers, so credit to @Ruud, @Danwakeem and @edc65.

This function modifies a char array in place.

My understanding is function entries are allowed unless explicitly banned in the question.

Try it online.

share|improve this answer

Perl 6, 28 bytes

{S:g/\w/{chr $/.ord+4+^31}/}


# give it a lexical name
my &swap = { … }

say swap 'Programming Puzzles & Code Golf';
# Kiltiznnrmt Kfaaovh & Xlwv Tlou

say swap ('a'..'z').join
# zyxwvutsrqponmlkjihgfedcba
share|improve this answer
When I run this it says: Warning: Use of "ord" without parentheses is ambiguous at (eval 8)[/System/Library/Perl/5.18/] line 2. I know nothing about perl so am I doing something wrong? How would I run this? – Downgoat Feb 5 at 6:31
@Doᴡɴɢᴏᴀᴛ If you notice it says this is written in Perl 6 You can go to #perl6 on freenode and type m: my &swap = {S:g/\w/{chr $/.ord+4+^31}/}; say swap ('a'..'z').join – Brad Gilbert b2gills Feb 5 at 6:34
Ah okay, apparently I can't read :P – Downgoat Feb 5 at 6:35
@Doᴡɴɢᴏᴀᴛ I added a note that you can test it on #perl6 on freenode – Brad Gilbert b2gills Feb 5 at 6:36

Unix shell + tr + printf, 35 bytes

tr A-Za-z `printf %s {Z..A} {z..a}`

Here you are, a canonical answer in tr. I thought how could a question to transliterate the alphabet go without a canonical answer to transliterate the alphabet?

tr by itself does not even do a "Hello, World!" and as such isn't a programming language, so I marked the answer as noncompeting[1].

[1]: Edit: Actually, Unix shell is the language and tr is the standard library. Thanks to Downgoat and Digital Trauma for helping me spot this out.

share|improve this answer
I think its fine to claim shell or bash as a language, and common utilities (tr is in coreutils) as the standard library. See countless of my answers ;-) – Digital Trauma Jan 4 at 15:54
But it doesn't work: tr: range-endpoints of 'Z-A' are in reverse collating sequence order. I think you have to do something like tr A-Za-z $(printf %s {Z..A} {z..a}) (and replace $( ) with backticks) – Digital Trauma Jan 4 at 15:55
@DigitalTrauma but not everyone has printf on their system. – zyabin101 Jan 4 at 16:35
I think you'd have quite a hard time finding a Unix system that doesn't have printf - after all, its specified by Posix. Also its a builtin in bash which is pretty ubiquitous these days. Regardless, having something pre-installed on everyone's system is not a prerequisite for code-golf - not everyone has CJam on their system either ;-) – Digital Trauma Jan 4 at 20:20
The space between } and { is required - otherwise the expansion becomes something like Zz Zy Zx ... Za Yz ... Aa – Digital Trauma Jan 7 at 19:06

05AB1E, 5 bytes [non-competing]


Uses CP-1252 character set.

Try it online!


žn    - Push [A-Za-z]
  žo  - Push [Z-Az-a]
    ‡ - Transliterate.
share|improve this answer

PostgreSQL, 118 125 bytes

FROM(SELECT text'Programming Puzzles & Code Golf's,text'abcdefghijklmnopqrstuvwxyz't)r



║                s                 ║            translate            ║
║ Programming Puzzles & Code Golf  ║ Kiltiznnrmt Kfaaovh & Xlwv Tlou ║

Input: SELECT text'...'s


Input as table:

FROM i,(SELECT text'abcdefghijklmnopqrstuvwxyz't)r



║                s                 ║            translate            ║
║ Hello, World!                    ║ Svool, Dliow!                   ║
║ Programming Puzzles & Code Golf  ║ Kiltiznnrmt Kfaaovh & Xlwv Tlou ║
║ abcdefghijklmnopqrstuvwxyz       ║ zyxwvutsrqponmlkjihgfedcba      ║
share|improve this answer
Hey lad2025, I think this is shorter than 118, but I am no expert in the counting rules – May 5 at 11:04

MATL, 21 28 bytes

Uses version 6.0.0, which is earlier than this challenge. The code runs in Octave.



>> matl
 > jttk2Y2mXK)o31Z~4-cK(
> Hello, World!
Svool, Dliow!


j             % input string
t             % duplicate
tk            % duplicate and convert to lowercase
2Y2           % string ''
m             % "ismember" function: produces logical index of letter positions
XK            % copy to clipboard K
)             % index into string to get its letters
o31Z~4-       % bitwise XOR with 31 and subtract 4
c             % convert to char
K             % paste logical index from clipboard K
(             % put back modified letters into original string

Old approach, 28 bytes

share|improve this answer

MATLAB, 61 bytes


I tried f=@ismember, and making the range a=65:90 a variable and do 32+a in the second ismember-call. All this shortened the code, but would result in a program and thus require both disp and input.

This gives:

ans('Hello, World!')
ans =
Svool, Dliow!

ans('Programming Puzzles & Code Golf')
ans =
Kiltiznnrmt Kfaaovh & Xlwv Tlou
share|improve this answer

Haskell, 119 104 bytes

Saved 15 bytes thanks to @nimi.

c=fromEnum;s=toEnum;f[]="";f(x:y)|64<c x&&c x<91=s(155-c x):f y|96<c x&&c x<123=s(219-c x):f y|0<1=x:f y


f "abcdefghijklmnopqrstuvwxyz"

f "Programming Puzzles & Code Golf"
"Kiltiznnrmt Kfaaovh & Xlwv Tlou"

f "Hello, World!"
"Svool, Dliow!"


let c=fromEnum;s=toEnum;--wrap names for later use, fromEnum gets ascii code from char, toEnum gets char from ascii code
f[]=[];                 --feed empty list (of chars in this case), get empty list
f(x:y)                  --feed a list, separate the first element and...
|64<c x&&c x<91=        --if its an uppercase char (using ascii code range)...
s(c x*(-1)+155)         --  inverse its ascii code value, move it to the range of uppercase and get the new char
                        --  (like rotating half turn a ruler by the side and then sliding it to the space it previously occupied)
:f y                    --  feed the rest of the list and stick the new char in front of the result
|96<c x&&c x<123=       --if its a lowercase char (using ascii code range)...
s(c x*(-1)+219)         --  inverse its ascii code value, move it to the range of lowercase and get the new char
:f y                    --  feed the rest of the list and stick the new char in front of the result
|True=x:f y             --otherwise feed the rest of the list and stick the char in front of the result

I'm new to Haskell... to functional programming... and to the site, and i know there are (a lot of) better answers to this question, but bear with me.

share|improve this answer
Some golfing tips: a) no need to use let. Start directly with c=fromEnum. Use (155-c x) and (219-c x). c) Truecan be replaced by 1<2. -- The code fails to load for me with the "ambigious type variable" error for functions c and s (ghci 7.10.2), but this can easily be fixed with f[]="" instead of f[]=[]. – nimi Jan 7 at 19:13
Thanks!, i was actually wondering if it was valid without "let", since it doesnt run directly on GHC. – fluffy ears Jan 22 at 6:34

Brachylog, 66 bytes


The lack of built-ins really hurts here, so we have to resort to good old ASCII codes computations.

The predicate brachylog_main expects a character codes string as input and no output, e.g. brachylog_main(`Hello, World!`,_).


_                                                                  § If the input is empty,
                                                                   § return true
 |                                                                 § Else
  hH(                                            ),[X]:"~c"w       § Print variable X which
                                                                   § depends on the head of
                                                                   § the input as a char code
                                                            ,?b:0& § Recursive call on the
                                                                   § tail of the input
     :64>:91<,77-H+78=X                                            § If H is capital, X =
                                                                   § 77 - H + 78
                       ;                                           § Else if H is non-cap, X=
                        H:96>:123<,109-H+110=X                     § 109 - H + 110
                                              ;                    § Else (not a letter)
                                               HX                  § H = X    
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Java, 136 bytes

void x(String i){for(char c:i.toCharArray()){if(Character.isLetter(c))c=c<91?(char)(90-(c-65)):(char)(122-(c-97));System.out.print(c);}}

Example usage:

class Test {
  static void x(String i){for(char c:i.toCharArray()){if(Character.isLetter(c))c=c<91?(char)(90-(c-65)):(char)(122-(c-97));System.out.print(c);}}
  public static void main(String[] args) {
    x("Programming Puzzles & Code Golf");
    // produces "Kiltiznnrmt Kfaaovh & Xlwv Tlou"

Probably the worst commonly-used language in terms of byte size.

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Perl 6, 40 39 bytes

Since everyone else is doing anonymous functions:

my &f=*.trans(/\w/=>{chr $/.ord+4+^31})

(Thanks @b2gills for the tip)

Uses the same bit flipping voodoo as some of the other posts. I wasn't sure whether to include the variable/function declaration in the byte count, so I did just in case. Without it this solution is only 34 bytes.


> f "zyxwvutsrqponmlkjihgfedcba"
> f "Kiltiznnrmt Kfaaovh & Xlwv Tlou"
Programming Puzzles & Code Golf
> f "Svool, Dliow!"
Hello, World!
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You can use *.trans(…) to make it shorter. – Brad Gilbert b2gills Feb 5 at 6:04

Python 3, 164 159 bytes

def f(t,a="abcdefghijklmnopqrstuvwxyz",b=""):
 for c in t:u=64<ord(c)<91;c=c.lower();c=a[::-1][a.index(c)] if c in a else c;b+=c.upper() if u else c
 return b
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