Rot-13: Difference between revisions

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Here is an implementation:
Here is an implementation:

{{works with|Python|2.x}}
<lang python>#!/usr/bin/env python
<lang python>#!/usr/bin/env python
import string
import string
Line 780: Line 782:
letter that's 13 steps from it (wrapping from z to a)
letter that's 13 steps from it (wrapping from z to a)
"""
"""
return string.translate( s,
return s.translate(
string.maketrans(
string.maketrans(
string.uppercase + string.lowercase,
string.ascii_uppercase + string.ascii_lowercase,
string.uppercase[13:] + string.uppercase[:13] +
string.ascii_uppercase[13:] + string.ascii_uppercase[:13] +
string.lowercase[13:] + string.lowercase[:13]
string.ascii_lowercase[13:] + string.ascii_lowercase[:13]
)
)
)
)
Line 797: Line 799:


The ''string.translate()'' and ''string.maketrans()'' functions make the function's definition almost trivial. It's a one-line function with some line wrapping for legibility. The ''fileinput'' module similarly makes the wrapper functionality trivial to implement. (This implementation is about seven logical lines long).
The ''string.translate()'' and ''string.maketrans()'' functions make the function's definition almost trivial. It's a one-line function with some line wrapping for legibility. The ''fileinput'' module similarly makes the wrapper functionality trivial to implement. (This implementation is about seven logical lines long).

{{works with|Python|3.x}}
<lang python>#!/usr/bin/env python
import string
def rot13(s):
"""Implement the rot-13 encoding function: "rotate" each letter by the
letter that's 13 steps from it (wrapping from z to a)
"""
return s.translate(
str.maketrans(
string.ascii_uppercase + string.ascii_lowercase,
string.ascii_uppercase[13:] + string.ascii_uppercase[:13] +
string.ascii_lowercase[13:] + string.ascii_lowercase[:13]
)
)
if __name__ == "__main__":
"""Peform line-by-line rot-13 encoding on any files listed on our
command line or act as a standard UNIX filter (if no arguments
specified).
"""
import fileinput
for line in fileinput.input():
print(rot13(line), end="")</lang>


=={{header|R}}==
=={{header|R}}==

Revision as of 08:23, 17 August 2009

Task
Rot-13
You are encouraged to solve this task according to the task description, using any language you may know.

Implement a "rot-13" function (or procedure, class, subroutine, or other "callable" object as appropriate to your programming environment). Optionally wrap this function in a utility program which acts like a common UNIX utility, performing a line-by-line rot-13 encoding of every line of input contained in each file listed on its command line, or (if no filenames are passed thereon) acting as a filter on its "standard input." (A number of UNIX scripting languages and utilities, such as awk and sed either default to processing files in this way or have command line switches or modules to easily implement these wrapper semantics, i.e. Perl and Python).

The "rot-13" encoding is commonly known from the early days of Usenet "Netnews" as a way of obfuscating text to prevent casual reading of spoiler or potentially offensive material. Many news reader and mail user agent programs have built-in "rot-13" encoder/decoders or have the ability to feed a message through any external utility script for performing this (or other) actions.

The definition of the rot-13 function is to simply replace every letter of the ASCII alphabet with the letter which is "rotated" 13 characters "around" the 26 letter alphabet from it's normal cardinal position (wrapping around from "z" to "a" as necessary). Thus the letters "abc" become "nop" and so on. Technically rot-13 is a "monoalphabetic substitution cipher" with a trivial "key". A proper implementation should work on upper and lower case letters, preserve case, and pass all non-alphabetic characters in the input stream through without alteration.

Ada

<lang ada>with Ada.Text_IO.Text_Streams; use Ada.Text_IO.Text_Streams; with Ada.Strings.Maps; use Ada.Strings.Maps; with Ada.Command_Line; use Ada.Command_Line;

procedure Rot_13 is 

  From_Sequence : Character_Sequence := "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";
  Result_Sequence : Character_Sequence := "nopqrstuvwxyzabcdefghijklmNOPQRSTUVWXYZABCDEFGHIJKLM";
  Rot_13_Mapping : Character_Mapping := To_Mapping(From_Sequence, Result_Sequence);

  In_Char : Character;
  Stdio : Stream_Access := Stream(Ada.Text_IO.Standard_Input);
  Stdout : Stream_Access := Stream(Ada.Text_Io.Standard_Output);
  Input : Ada.Text_Io.File_Type;

begin 

  if Argument_Count > 0 then
     for I in 1..Argument_Count loop
        begin
           Ada.Text_Io.Open(File => Input, Mode => Ada.Text_Io.In_File, Name => Argument(I));
           Stdio := Stream(Input);
            while not Ada.Text_Io.End_Of_File(Input) loop
              In_Char :=Character'Input(Stdio); 
              Character'Output(Stdout, Value(Rot_13_Mapping, In_Char));
           end loop;
           Ada.Text_IO.Close(Input);
        exception
           when Ada.Text_IO.Name_Error =>
              Ada.Text_Io.Put_Line(File => Ada.Text_Io.Standard_Error, Item => "File " & Argument(I) & " is not a file.");
           when Ada.Text_Io.Status_Error =>
              Ada.Text_Io.Put_Line(File => Ada.Text_Io.Standard_Error, Item => "File " & Argument(I) & " is already opened.");
        end;
     end loop;
  else
     while not Ada.Text_Io.End_Of_File loop
        In_Char :=Character'Input(Stdio); 
        Character'Output(Stdout, Value(Rot_13_Mapping, In_Char));
     end loop;
  end if;

end Rot_13;</lang>

ALGOL 68

Translation of: Modula-3
Works with: ALGOL 68 version Standard - no extensions to language used
Works with: ALGOL 68G version Any - tested with release mk15-0.8b.fc9.i386

<lang algol>BEGIN 

 CHAR c;
 on logical file end(stand in, (REF FILE f)BOOL: (stop; SKIP));
 on line end(stand in, (REF FILE f)BOOL: (print(new line); FALSE));
 DO
   read(c);
   IF c >= "A" AND c <= "M" OR c >= "a" AND c <= "m" THEN
     c := REPR(ABS c + 13)
   ELIF c >= "N" AND c <= "Z" OR c >= "n" AND c <= "z" THEN
     c := REPR(ABS c - 13)
   FI;
   print(c)
 OD

END # rot13 #</lang> Sample run on linux: 

$ echo Big fjords vex quick waltz nymph! | a68g Rot-13.a68
Ovt swbeqf irk dhvpx jnygm alzcu!

AutoHotkey

Code modified from stringmod by Hugo: ahk discussion <lang AutoHotkey>Str0=Hello, This is a sample text with 1 2 3 or other digits!@#$^&*()-_= Str1 := Rot13(Str0) Str2 := Rot13(Str1) MsgBox % Str0 "`n" Str1 "`n" Str2

Rot13(string) { 

  Loop Parse, string
  {
     char := Asc(A_LoopField)
     ; o is 'A' code if it is an uppercase letter, and 'a' code if it is a lowercase letter
     o := Asc("A") * (Asc("A") <= char && char <= Asc("Z")) + Asc("a") * (Asc("a") <= char && char <= Asc("z"))
     If (o > 0)
     {
        ; Set between 0 and 25, add rotation factor, modulus alphabet size
        char := Mod(char - o + 13, 26)
        ; Transform back to char, upper or lower
        char := Chr(char + o)
     }
     Else
     {
        ; Non alphabetic, unchanged
        char := A_LoopField
     }
     rStr := rStr char
  }
  Return rStr

}</lang>

AWK

<lang awk>BEGIN { 

 for(i=0; i < 256; i++) {
   amap[sprintf("%c", i)] = i
 }
 for(l=amap["a"]; l <= amap["z"]; l++) {
   rot13[l] = sprintf("%c", (((l-amap["a"])+13) % 26 ) + amap["a"])
 }
 FS = ""

} { 

 o = ""
 for(i=1; i <= NF; i++) {
   if ( amap[tolower($i)] in rot13 ) {
     c = rot13[amap[tolower($i)]]
     if ( tolower($i) != $i ) c = toupper(c)
     o = o c
   } else {
     o = o $i
   }
 }
 print o

}</lang>

BASIC

Works with: QuickBasic version 4.5
CLS
INPUT "Enter a string: ", s$
ans$ = ""
FOR a = 1 TO LEN(s$)
        letter$ = MID$(s$, a, 1)
        char$ = ""
        IF letter$ >= "A" AND letter$ <= "Z" THEN
                char$ = CHR$(ASC(letter$) + 13)
                IF char$ > "Z" THEN char$ = CHR$(ASC(char$) - 26)
        ELSEIF letter$ >= "a" AND letter$ <= "z" THEN
                char$ = CHR$(ASC(letter$) + 13)
                IF char$ > "z" THEN char$ = CHR$(ASC(char$) - 26)
        ELSE
                char$ = letter$
        END IF
        ans$ = ans$ + char$
NEXT a
PRINT ans$

Befunge

~:"z"`#v_:"m"`#v_:"`"` |>
 :"Z"`#v_:"M"`#v_:"@"`|>
 : 0 `#v_@v-6-7<      >
,      <  <+6+7       <<v

C

<lang c>#include<stdio.h>

  1. include<stdlib.h>
  2. include<ctype.h>
  1. define MAXLINE 1024

char *rot13(char *s) { 

       char *p=s;
       int upper;

       while(*p) {
               upper=toupper(*p);
               if(upper>='A' && upper<='M') *p+=13;
               else if(upper>='N' && upper<='Z') *p-=13;
               ++p;
       }
       }
       return s;

}

void rot13file(FILE *fp) { 

       static char line[MAXLINE];
       while(fgets(line, MAXLINE, fp)>0) fputs(rot13(line), stdout);

}

int main(int argc, char *argv[]) { 

       int n;
       FILE *fp;

       if(argc>1) {
               for(n=1; n<argc; ++n) {
                       if(!(fp=fopen(argv[n], "r"))) {
                               fprintf(stderr, "ERROR: Couldn\'t read %s\n", argv[n]);
                               exit(EXIT_FAILURE);
                       }
                       rot13file(fp);
                       fclose(fp);
               }
       } else rot13file(stdin);

       return EXIT_SUCCESS;

}</lang>

C++

<lang cpp>

  1. include <iostream>
  2. include <istream>
  3. include <ostream>
  4. include <fstream>
  5. include <cstdlib>
  6. include <string>

// the rot13 function std::string rot13(std::string s) { 

 static std::string const
   lcalph = "abcdefghijklmnopqrstuvwxyz",
   ucalph = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";

 std::string result;
 std::string::size_type pos;

 result.reserve(s.length());

 for (std::string::iterator it = s.begin(); it != s.end(); ++it)
 {
   if ( (pos = lcalph.find(*it)) != std::string::npos )
     result.push_back(lcalph[(pos+13) % 26]);
   else if ( (pos = ucalph.find(*it)) != std::string::npos )
     result.push_back(ucalph[(pos+13) % 26]);
   else
     result.push_back(*it);
 }

 return result;

}

// function to output the rot13 of a file on std::cout // returns false if an error occurred processing the file, true otherwise // on entry, the argument is must be open for reading int rot13_stream(std::istream& is) { 

 std::string line;
 while (std::getline(is, line))
 {
   if (!(std::cout << rot13(line) << "\n"))
     return false;
 }
 return is.eof();

}

// the main program int main(int argc, char* argv[]) { 

 if (argc == 1) // no arguments given
   return rot13_stream(std::cin)? EXIT_SUCCESS : EXIT_FAILURE;

 std::ifstream file;
 for (int i = 1; i < argc; ++i)
 {
   file.open(argv[i], std::ios::in);
   if (!file)
   {
     std::cerr << argv[0] << ": could not open for reading: " << argv[i] << "\n";
     return EXIT_FAILURE;
   }
   if (!rot13_stream(file))
   {
     if (file.eof())
       // no error occurred for file, so the error must have been in output
       std::cerr << argv[0] << ": error writing to stdout\n";
     else
       std::cerr << argv[0] << ": error reading from " << argv[i] << "\n";
     return EXIT_FAILURE;
   }
   file.clear();
   file.close();
   if (!file)
     std::cerr << argv[0] << ": warning: closing failed for " << argv[i] << "\n";
 }
 return EXIT_SUCCESS;

}</lang>

C#

<lang csharp>using System; using System.Text;

class Program { 

   static string rot13(string text) {
       StringBuilder outp = new StringBuilder();

       foreach (char i in text) {
           if (i >= 'a' && i <= 'm' || i >= 'A' && i <= 'M') outp.Append((char)((int)i + 13));         
           else if (i >= 'n' && i <= 'z' || i >= 'N' && i <= 'Z') outp.Append((char)((int)i - 13));
           else outp.Append(i);
       }
       return outp.ToString();
   }

   static void Main(string[] args) {
       Console.WriteLine(rot13("nowhere ABJURER")); //Example
   }

}</lang>

Common Lisp

The standard gives implementations great leeway with respect to character encodings, so we can't rely on the convenient properties of ASCII.

<lang lisp>(defconstant +alphabet+ '(#\A #\B #\C #\D #\E #\F #\G #\H #\I #\J #\K #\L #\M #\N #\O #\P 

 #\Q #\R #\S #\T #\U #\V #\W #\X #\Y #\Z))

(defun rot13 (s) 

 (map 'string
   (lambda (c &aux (n (position (char-upcase c) +alphabet+)))
     (if n
       (funcall
         (if (lower-case-p c) #'char-downcase #'identity)
         (nth (mod (+ 13 n) 26) +alphabet+))
       c))
   s))</lang>

D

Implement a Rot-13 function. <lang d>module rot13 ; import std.stdio ;

version(D_Version2) { 

 import std.algorithm ;

}

char rot13char(char t) { 

 ubyte c = (t & 0x9f) - 1 ;
 if (c > 25 || (t & 0x40) == 0 )
   return t ;
 c = (c + 13) % 26 ; // that's why Rot-13 :)
 return (t & 0x60) | (c + 1) ;

}

string rot13(string s) { 

 string t ;
 foreach(c ; s)
   t ~= rot13char(c) ;
 return t ;

}

void main(string[] args) { 

 string text = "abc! ABC!" ;

 writefln(rot13(text)) ;
 writefln(rot13("abcdefghijklmnopqrstuvwxyz"~
                "ABCDEFGHIJKLMNOPQRSTUVWXYZ")) ;

version(D_Version2) { 

 writefln(map!(rot13char)(text)) ; 
 writefln(map!(rot13char)("abcdefghijklmnopqrstuvwxyz"~ 
                          "ABCDEFGHIJKLMNOPQRSTUVWXYZ")) ;

} }</lang>

A simpler version (D V.1):

<lang d>import std.stdio, std.string; void main() { 

   auto r13 = letters.maketrans(uppercase[13..$] ~ uppercase[0..13] ~
                                lowercase[13..$] ~ lowercase[0..13]);
   writefln("This is the 1st test!".translate(r13, null));

}</lang>

E

<lang e>pragma.enable("accumulator")

var rot13Map := [].asMap() for a in ['a', 'A'] { 

   for i in 0..!26 {
       rot13Map with= (a + i, E.toString(a + (i + 13) % 26))
   }

}

def rot13(s :String) { 

 return accum "" for c in s { _ + rot13Map.fetch(c, fn{ c }) }

}</lang>

FALSE

[^$1+][$32|$$'z>'a@>|$[\%]?~[13\'m>[_]?+]?,]#%

Forth

A simple version, using nested conditionals. 

: r13 ( c -- o )
  dup 32 or                                    \ tolower
  dup [char] a [char] z 1+ within if
    [char] m > if -13 else 13 then +
  else drop then ;

A table driven version which should be more efficient. The mechanism is flexible enough to express any sort of transform. 

: ,chars ( end start -- )
  do i c, loop ;

: xlate create does> ( c -- c' ) + c@ ;

xlate rot13 
  char A         0    ,chars
  char Z 1+ char N    ,chars
  char N    char A    ,chars
  char a    char Z 1+ ,chars
  char z 1+ char n    ,chars
  char n    char a    ,chars
  256       char z 1+ ,chars

: rot13-string ( addr len -- )
  over + swap do i c@ rot13 i c! loop ;

: .rot13" ( string -- )
  [char] " parse 2dup rot13-string type ;
 
.rot13" abjurer NOWHERE"   \ nowhere ABJURER

Fortran

Works with: Fortran version 90 and later

<lang fortran> MODULE ROT13 

  IMPLICIT NONE
  CHARACTER(80) :: teststr = "ABCDEFGHIJKLMNOPQRSTUVWXYZ - abcdefghijklmnopqrstuvwxyz"

  CONTAINS

  SUBROUTINE ROT_13(s)
    CHARACTER(*), INTENT(in out) :: s
    INTEGER :: i

    DO i = 1, LEN(s)
       SELECT CASE (s(i:i))
         CASE ("A":"M")
           s(i:i) = ACHAR(IACHAR(s(i:i))+13)
         
         CASE ("N":"Z")
           s(i:i) = ACHAR(IACHAR(s(i:i))-13)
         
         CASE ("a":"m")
           s(i:i) = ACHAR(IACHAR(s(i:i))+13)
         
         CASE ("n":"z")
           s(i:i) = ACHAR(IACHAR(s(i:i))-13)
       END SELECT
    END DO
  END SUBROUTINE ROT_13
END MODULE ROT13

PROGRAM Example
  USE ROT13
 
  CALL ROT_13(teststr)
  WRITE(*,*) teststr
  CALL ROT_13(teststr)
  WRITE(*,*) teststr

END PROGRAM Example</lang>

Ouput 

NOPQRSTUVWXYZABCDEFGHIJKLM - nopqrstuvwxyzabcdefghijklm
ABCDEFGHIJKLMNOPQRSTUVWXYZ - abcdefghijklmnopqrstuvwxyz

Groovy

Solution: <lang groovy>def rot13 = { String s -> 

   (s as List).collect { ch ->
       switch (ch) {
           case ('a'..'m') + ('A'..'M'):
               return (((ch as char) + 13) as char)
           case ('n'..'z') + ('N'..'Z'):
               return (((ch as char) - 13) as char)
           default:
               return ch
       }
   }.inject ("") { string, ch -> string += ch}

}</lang>

Test program: <lang groovy>println rot13("Noyr jnf V, 'rer V fnj Ryon.")</lang>

Output: 

Able was I, 'ere I saw Elba.

Haskell

Straightforward implementation by checking multiple cases: 

import Data.Char

rot13 :: Char -> Char
rot13 c
  | toLower c >= 'a' && toLower c <= 'm' = chr (ord c + 13)
  | toLower c >= 'n' && toLower c <= 'z' = chr (ord c - 13)
  | otherwise = c

To wrap that as an utility program, here's a quick implementation of a general framework: 

import System.Environment
import System.IO
import System.Directory
import Control.Monad

hInteract :: (String -> String) -> Handle -> Handle -> IO ()
hInteract f hIn hOut =
  hGetContents hIn >>= hPutStr hOut . f

processByTemp :: (Handle -> Handle -> IO ()) -> String -> IO ()
processByTemp f name = do
  hIn <- openFile name ReadMode
  let tmp = name ++ "$" 
  hOut <- openFile tmp WriteMode
  f hIn hOut
  hClose hIn
  hClose hOut
  removeFile name
  renameFile tmp name

process :: (Handle -> Handle -> IO ()) -> [String] -> IO ()
process f [] = f stdin stdout
process f ns = mapM_ (processByTemp f) ns

Then the wrapped program is simply 

main = do
  names <- getArgs
  process (hInteract (map rot13)) names

Note that the framework will read the file lazily, which also provides buffering.

Icon

like javascript 

procedure main()
   local str, plain, rot13
   rot13 := "nopqrstuvwxyzabcdefghijklmNOPQRSTUVWXYZABCDEFGHIJKLM";
   plain := "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";
   str := "ABJURER nowhere"
   write(map(str, plain, rot13))
end

J

rot13=: (a.,~a.{~,65 97+/26|13+i.26) {~ (a.,~a.{~,65 97+/i.26) i. ]

For example: 

   rot13 'abc! ABC!'
nop! NOP!

Compare with the solution to the Change String Case task.

Java

<lang java> import java.io.BufferedReader; import java.io.FileNotFoundException; import java.io.FileReader; import java.io.IOException; import java.io.InputStreamReader; public class ROT13{ 

      public static void main(String[] args){
              BufferedReader in;
              if(args.length >= 1){
                      for(String file: args){
                              try{
                                      in= new BufferedReader(new FileReader(file));
                                      String line;
                                      while((line= in.readLine()) != null){
                                              System.out.println(convert(line));
                                      }
                              }catch(FileNotFoundException e){
                                      e.printStackTrace();
                              }catch(IOException e){
                                      e.printStackTrace();
                              }
                      }
              }else{
                      try{
                              in= new BufferedReader(new InputStreamReader(System.in));
                              String line;
                              while((line= in.readLine()) != null){
                                      System.out.println(convert(line));
                              }
                      }catch(IOException e){
                              e.printStackTrace();
                      }
              }
      }
      public static String convert(String msg){
              String retVal= "";
              for(char a: msg.toCharArray()){
                      if(a >= 'A' && a <= 'Z'){
                              a+= 13;
                              if(a > 'Z') a-= 26;
                      }else if(a >= 'a' && a <= 'z'){
                              a+= 13;
                              if(a > 'z') a-= 26;
                      }
                      retVal+= a;
              }
              return retVal;
      }

}</lang>

JavaScript

<lang javascript>var rot13Str = "nopqrstuvwxyzabcdefghijklmNOPQRSTUVWXYZABCDEFGHIJKLM"; var plainStr = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";

function rot13(s) { 

 var a = [];
 for (var i=0; i<s.length; i++) {
   var c = s.charAt(i);
   var found = plainStr.indexOf(c);
   a.push(found<0 ? c : rot13Str.charAt(found));
 }
 return a.join('');

}

alert( rot13("ABJURER nowhere") ); // NOWHERE abjurer</lang>

<lang logo> to rot13 :c 

 make "a difference ascii lowercase :c  ascii "a
 if or :a < 0 :a > 25 [output :c]
 make "delta ifelse :a < 13 [13] [-13]
 output char sum :delta ascii :c

end

print map "rot13 "|abjurer NOWHERE| nowhere ABJURER </lang>

Mathematica

<lang Mathematica> 

charslower="abcdefghijklmnopqrstuvwxyz"//Characters;
charsupper="ABCDEFGHIJKLMNOPQRSTUVWXYZ"//Characters;
ruleslower=Rule@@@({charslower,RotateLeft[charslower,13]} // Transpose);
rulesupper=Rule@@@({charsupper,RotateLeft[charsupper,13]} // Transpose);
rules=Join[ruleslower,rulesupper];
text="Hello World! Are you there!?"
text=StringReplace[text,rules]
text=StringReplace[text,rules]

</lang> gives back: <lang Mathematica> 

Hello World! Are you there!?
Uryyb Jbeyq! Ner lbh gurer!?
Hello World! Are you there!?

</lang>

Modula-3

This implementation reads from stdin and writes to stdout. <lang modula3>MODULE Rot13 EXPORTS Main;

IMPORT Stdio, Rd, Wr;

VAR c: CHAR;

<*FATAL ANY*>

BEGIN 

 WHILE NOT Rd.EOF(Stdio.stdin) DO
   c := Rd.GetChar(Stdio.stdin);
   IF c >= 'A' AND c <= 'M' OR c >= 'a' AND c <= 'm' THEN
     c := VAL(ORD((ORD(c) + 13)), CHAR);
   ELSIF c >= 'N' AND c <= 'Z' OR c >= 'n' AND c <= 'z' THEN
     c := VAL(ORD((ORD(c) - 13)), CHAR);
   END;
   Wr.PutChar(Stdio.stdout, c);
 END;

END Rot13.</lang>

Output: 

martin@thinkpad:~$ ./prog
Foo bar baz
Sbb one onm
martin@thinkpad:~$ echo "Bar baz foo" | ./prog
One onm sbb
martin@thinkpad:~$ echo "Foo bar baz" > foo.txt 
martin@thinkpad:~$ echo "quux zeepf" >> foo.txt 
martin@thinkpad:~$ cat foo.txt | ./prog
Sbb one onm
dhhk mrrcs

OCaml

Straightforward implementation for characters by using character range patterns: <lang ocaml>let rot13 c = match c with 

  'A'..'M'
| 'a'..'m' -> char_of_int (int_of_char c + 13)
| 'N'..'Z'
| 'n'..'z' -> char_of_int (int_of_char c - 13)
| _        -> c</lang>

We provide a function for converting whole strings: <lang ocaml>let rot13_str s = 

 let len = String.length s in
 let result = String.create len in
 for i = 0 to len - 1 do
   result.[i] <- rot13 s.[i]
 done;
 result</lang>

Perl

<lang perl>sub rot13 { 

 my $string = shift;
 $string =~ tr/A-Za-z/N-ZA-Mn-za-m/;
 return $string;

}

print rot13($_) while (<>);</lang>

Input: 

NOWHERE Abjurer

Output: 

ABJURER Nowhere

This one-liner version demonstrates that most of the verbosity above was simply needed to define a function:

<lang perl>perl -pe 'tr/A-Za-z/N-ZA-Mn-za-m/'</lang>

PHP

PHP has a built-in function for this: <lang php>echo str_rot13('foo'), "\n";</lang> will output 

sbb

Here is an implementation: <lang php><?php function rot13($s) { 

   return strtr($s, 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz',
                    'NOPQRSTUVWXYZABCDEFGHIJKLMnopqrstuvwxyzabcdefghijklm');

}

echo rot13('foo'), "\n"; ?></lang>

Output: 

sbb

Pop11

In Pop11 characters are just integers, so we can use integer comparisons and arithmetic (assuming ASCII based encoding). 

define rot13(s);
    lvars j, c;
    for j from 1 to length(s) do
        s(j) -> c;
        if `A` <= c and c <= `M` or `a` <= c and c <= `m` then
            c + 13 -> s(j);
        elseif `N` <= c and c <= `Z` or `n` <= c and c <= `z` then
            c - 13 -> s(j);
        endif;
    endfor;
    s;
enddefine;

rot13('NOPQRSTUVWXYZABCDEFGHIJKLMnopqrstuvwxyzabcdefghijklm') =>

Python

Python has built-in rot13 encoding and decoding: 

>>> u'foo'.encode('rot13')
'sbb'
>>> 'sbb'.decode('rot13')
u'foo'

Here is an implementation:

Works with: Python version 2.x

<lang python>#!/usr/bin/env python import string def rot13(s): 

  """Implement the rot-13 encoding function: "rotate" each letter by the
     letter that's 13 steps from it (wrapping from z to a)
  """
  return s.translate(
      string.maketrans(
          string.ascii_uppercase + string.ascii_lowercase,
          string.ascii_uppercase[13:] + string.ascii_uppercase[:13] +
          string.ascii_lowercase[13:] + string.ascii_lowercase[:13]
          )
      )

if __name__ == "__main__": 

  """Peform line-by-line rot-13 encoding on any files listed on our
     command line or act as a standard UNIX filter (if no arguments
     specified).
  """
  import fileinput
  for line in fileinput.input():
     print rot13(line),  # (Note the trailing comma; avoid double-spacing our output)!</lang>

The string.translate() and string.maketrans() functions make the function's definition almost trivial. It's a one-line function with some line wrapping for legibility. The fileinput module similarly makes the wrapper functionality trivial to implement. (This implementation is about seven logical lines long).

Works with: Python version 3.x

<lang python>#!/usr/bin/env python import string def rot13(s): 

  """Implement the rot-13 encoding function: "rotate" each letter by the
     letter that's 13 steps from it (wrapping from z to a)
  """
  return s.translate(
      str.maketrans(
          string.ascii_uppercase + string.ascii_lowercase,
          string.ascii_uppercase[13:] + string.ascii_uppercase[:13] +
          string.ascii_lowercase[13:] + string.ascii_lowercase[:13]
          )
      )

if __name__ == "__main__": 

  """Peform line-by-line rot-13 encoding on any files listed on our
     command line or act as a standard UNIX filter (if no arguments
     specified).
  """
  import fileinput
  for line in fileinput.input():
     print(rot13(line), end="")</lang>

R

<lang R> 

rot13 <- function(x)
{
  old <- paste(letters, LETTERS, collapse="", sep="")
  new <- paste(substr(old, 27, 52), substr(old, 1, 26), sep="")
  chartr(old, new, x)
}
x <- "The Quick Brown Fox Jumps Over The Lazy Dog!.,:;'#~[]{}"
rot13(x)   # "Gur Dhvpx Oebja Sbk Whzcf Bire Gur Ynml Qbt!.,:;'#~[]{}"
x2 <- paste(letters, LETTERS, collapse="", sep="")
rot13(x2)  # "nNoOpPqQrRsStTuUvVwWxXyYzZaAbBcCdDeEfFgGhHiIjJkKlLmM"

</lang> For a slightly more general function, see the example on the chartr help page.

Ruby

<lang ruby>def rot13(s) 

 s.tr('A-Za-z', 'N-ZA-Mn-za-m')

end

alpha = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz'; puts rot13(alpha)</lang>

Output: 

NOPQRSTUVWXYZABCDEFGHIJKLMnopqrstuvwxyzabcdefghijklm

Scheme

Library: SRFI-13
Works with: Chicken Scheme

<lang scheme>(use srfi-13)

(define (rot13 str) 

 (define (rot13-char c)
   (string (integer->char

(cond ((or (and (char>=? c #\a) (char<? c #\n)) 

                       (and (char>=? c #\A) (char<? c #\N)))

(+ (char->integer c) 13)) ((or (and (char>=? c #\n) (char<? c #\{)) 

                       (and (char>=? c #\N) (char<? c #\[)))

(- (char->integer c) 13)) 

                  (else (char->integer c))))))
 
 (if (= (string-length str) 0)
     (newline)
     (begin
       (display (rot13-char (car (string->list str)))) 
       (rot13 (list->string (cdr (string->list str)))))))</lang>

Seed7

This rot13 program reads from standard input and writes to standard output: 

$ include "seed7_05.s7i";

const proc: main is func
  local
    var char: ch is ' ';
  begin
    ch := getc(IN);
    while not eof(IN) do
      if (ch >= 'a' and ch <= 'm') or (ch >= 'A' and ch <= 'M') then
        ch := chr(ord(ch) + 13);
      elsif (ch >= 'n' and ch <= 'z') or (ch >= 'N' and ch <= 'Z') then
        ch := chr(ord(ch) - 13);
      end if;
      write(ch);
      ch := getc(IN);
    end while;
  end func;


Slate

A shell script:

<lang slate>

  1. !/usr/local/bin/slate

ch@(String Character traits) rot13 [| value upper | 

 upper: ch isUppercase.
 value: (ch toLowercase as: Integer).
 (value >= 97) /\ (value < 110)
   ifTrue: [value: value + 13]
   ifFalse: [(value > 109) /\ (value <= 122)
               ifTrue: [value: value - 13]].
 upper
   ifTrue: [(value as: String Character) toUppercase]
   ifFalse: [value as: String Character]

].

lobby define: #Rot13Encoder &parents: {Encoder}.

c@(Rot13Encoder traits) convert [ 

 [c in isAtEnd] whileFalse: [c out nextPut: c in next rot13].

].

(Rot13Encoder newFrom: Console reader to: Console writer) convert.

</lang>

Normal functions:

<lang slate>

ch@(String Character traits) rot13 [| value upper | 

 upper: ch isUppercase.
 value: (ch toLowercase as: Integer).
 (value >= 97) /\ (value < 110)
   ifTrue: [value: value + 13]
   ifFalse: [(value > 109) /\ (value <= 122)
               ifTrue: [value: value - 13]].
 upper
   ifTrue: [(value as: String Character) toUppercase]
   ifFalse: [value as: String Character]

].

s@(String traits) rot13 [| result | 

 result: s newSameSize.
 s doWithIndex: [| :each :index |
   result at: index put: each rot13].
 result

].

slate[37]> 'abc123' rot13. 'nop123'


</lang>

Smalltalk

Works with: GNU Smalltalk

Here we implemented three ways. The first one is the simplest. The second demonstrates extending the String class with a generic rot method, which in turn uses two new method for the class Character (+ and -). The third one is an imitation of the tr '[a-m][n-z]' '[n-z][a-m]' approach (see UNIX Shell example), done through a block closure and using also the new method trFrom:to: for Character.

<lang smalltalk> "1. simple approach" rot13 := [ :string | 

   string collect: [ :each | | index |
       index := 'abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ' indexOf: each ifAbsent: [ 0 ]. "Smalltalk uses 1-based indexing"
       index isZero 
           ifTrue: [ each ] 
           ifFalse: [ 'nopqrstuvwxyzabcdefghijklmNOPQRSTUVWXYZABCDEFGHIJKLM' at: index ] ] ].

(rot13 value: 'Test123') printNl "gives 'Grfg123'"


"2. extending built-in classes" Character extend [ 

 + inc [
    (inc isKindOf: Character)
    ifTrue: [
       ^ ( Character value: ((self asInteger) + (inc asInteger)) )
    ] ifFalse: [
      ^ ( Character value: ((self asInteger) + inc) )
    ]
 ]
 - inc [
   ^ ( self + (inc asInteger negated) )
 ]
 trFrom: map1 to: map2 [
    (map1 includes: self) ifTrue: [
       ^ map2 at: (map1 indexOf: self)
    ] ifFalse: [ ^self ]
 ]

].

String extend [ 

 rot: num [ |s|
   s := String new.
   self do: [ :c |
        ((c asLowercase) between: $a and: $z)

ifTrue: [ |c1| 

             c1 := ( $a + ((((c asLowercase) - $a + num) asInteger) rem:26)).
             (c isLowercase) ifFalse: [ c1 := c1 asUppercase ].
             s := s, (c1 asString)
          ]
          ifFalse: [

s := s, (c asString) 

          ]
    ].
    ^s
 ]

].

('abcdefghijklmnopqrstuvwxyz123!' rot: 13) displayNl. (('abcdefghijklmnopqrstuvwxyz123!' rot: 13) rot: 13) displayNl.


"2. using a 'translation'. Not very idiomatic Smalltalk code" rotThirteen := [ :s | |m1 m2 r| 

 r := String new.
 m1 := OrderedCollection new.
 0 to: 25 do: [ :i | m1 add: ($a + i) ].
 m2 := OrderedCollection new.
 0 to: 25 do: [ :i | m2 add: ($a + ((i+13) rem: 26)) ].
 s do: [ :c |
   (c between: $a and: $z) | (c between: $A and: $Z)
     ifTrue: [ | a |
       a := (c asLowercase) trFrom: m1 to: m2.
       (c isUppercase) ifTrue: [ a := a asUppercase ].
       r := r, (a asString)] 
     ifFalse: [ r := r, (c asString) ]
 ].
 r

].

(rotThirteen value: 'abcdefghijklmnopqrstuvwxyz123!') displayNl.</lang>

Tcl

<lang tcl>proc rot13 line { 

   string map {
       a n b o c p d q e r f s g t h u i v j w k x l y m z
       n a o b p c q d r e s f t g u h v i w j x k y l z m
       A N B O C P D Q E R F S G T H U I V J W K X L Y M Z
       N A O B P C Q D R E S F T G U H V I W J X K Y L Z M
   } $line

}</lang>

Using

Library: TclX

we can write

<lang tcl>package require Tclx proc rot13 str { 

   translit "A-Za-z" "N-ZA-Mn-za-m" $str

}</lang>

TI-83 BASIC

Calculator symbol translations:

"STO" arrow: →

Perfoms ROT-13 on the contents of Str1. Also uses the string variables Str0 and Str2 and the real variable N. 

:"ABCDEFGHIJKLMNOPQRSTUVWXYZ→Str0
:"."→Str2
:For(N,1,length(Str1
:If inString(Str0,sub(Str1,N,1
:Then
:inString(Str0,sub(Str1,N,1
:Ans+13-26(Ans>13
:Str2+sub(Str0,Ans,1→Str2
:Else
:Str2+sub(Str1,N,1→Str2
:End
:End
:sub(Str2,2,length(Str2)-1→Str1

UNIX Shell

Bourne Shell

#!/bin/sh
function rot13 () {
   tr '[a-m][n-z][A-M][N-Z]' '[n-z][a-m][N-Z][A-M]'
   }
[ "$#" -lt 1 ] && {
   rot13
   } || for eachFile in "$@"; do
            cat "$eachFile" | rot13
            done

UNIX shell assumes availability of the standard UNIX utility commands (in the "coreutils" package on Linux systems, for example); thus the tr (translate) command is trivially provided with the proper arguments to perform the rotations. This example shows proper quoting around "$@" (magical argument list) and "$eachFile" such that this script work properly even if some of the files named on the command line contain embedded spaces or other such characters.

Ursala

I/O in Ursala is meant to be handled automatically as much as possible by the run time system. This source text describes only a function that operates on the contents of a list of files passed to it as an argument, with the transformed files returned as a result. The #executable compiler directive and its parameters mean that this source will be compiled to an executable file with the required command line interface. The rot13 encryption algorithm itself is a simple finite map implemented in a half line of code. <lang Ursala>

  1. import std
  1. executable (<'parameterized','default-to-stdin'>,<>)

rot = ~command.files; * contents:= ~contents; * * -:~& -- ^p(~&,rep13~&zyC)~~ ~=`A-~ letters </lang>

Vedit macro language

Using ROT13.TBL from here <lang vedit>Translate_Load("ROT13.TBL") Translate_Block(0, File_Size)</lang>

You can execute the macro from DOS command prompt with the following command: 

vpw -q -x rot13.vdm inputfile -a outputfile

In addition to translating a block of text, the translate table allows viewing and editing ROT-13 text without translating the actual file into ASCII. The displayed characters and keyboard input are translated on-the-fly. This is the normal way to edit for example DOS/OEM and EBCDIC files.

Visual Basic .NET

Platform: .NET

Language Version: 9.0+ 

Module Module1

   Private Function rot13(ByVal str As String) As String
       Dim newChars As Char(), i, j As Integer, original, replacement As String

       original = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz"
       replacement = "NOPQRSTUVWXYZABCDEFGHIJKLMnopqrstuvwxyzabcdefghijklm"

       newChars = str.ToCharArray()

       For i = 0 To newChars.Length - 1
           For j = 0 To 51
               If newChars(i) = original(j) Then
                   newChars(i) = replacement(j)
                   Exit For
               End If
           Next
       Next

       Return New String(newChars)
   End Function

End Module

This solution just uses simple textual substitution, since the number of characters involved is small. If the cipher involved more characters, it would be better to use character arithmetic; however, this is not encouraged in VB.Net.

XSLT

Textual transforms are one of the domains XSLT was designed for. 

<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
  <xsl:output method="text" />
  <xsl:variable name="alpha">ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz</xsl:variable>
  <xsl:variable name="rot13">NOPQRSTUVWXYZABCDEFGHIJKLMnopqrstuvwxyzabcdefghijklm</xsl:variable>  
  <xsl:template match="body"> 
    <xsl:apply-templates/>
  </xsl:template>
  <xsl:template match="rot13">
    <xsl:value-of select="translate(.,$alpha,$rot13)"/>
  </xsl:template>
</xsl:stylesheet>

This will transform the input: 

<body>The <rot13>Abjurer</rot13> was to be found <rot13>Nowhere</rot13>.</body>

into: 

The Nowhere was to be found Abjurer.
Retrieved from "https://rosettacode.org/wiki/Rot-13?oldid=45179"