Rot-13: Difference between revisions
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Here is an implementation: |
Here is an implementation: |
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{{works with|Python|2.x}} |
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<lang python>#!/usr/bin/env python |
<lang python>#!/usr/bin/env python |
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import string |
import string |
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letter that's 13 steps from it (wrapping from z to a) |
letter that's 13 steps from it (wrapping from z to a) |
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""" |
""" |
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return |
return s.translate( |
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string.maketrans( |
string.maketrans( |
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string. |
string.ascii_uppercase + string.ascii_lowercase, |
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string. |
string.ascii_uppercase[13:] + string.ascii_uppercase[:13] + |
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string. |
string.ascii_lowercase[13:] + string.ascii_lowercase[:13] |
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) |
) |
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) |
) |
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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). |
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{{works with|Python|3.x}} |
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<lang python>#!/usr/bin/env python |
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import string |
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def rot13(s): |
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"""Implement the rot-13 encoding function: "rotate" each letter by the |
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letter that's 13 steps from it (wrapping from z to a) |
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""" |
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return s.translate( |
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str.maketrans( |
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string.ascii_uppercase + string.ascii_lowercase, |
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string.ascii_uppercase[13:] + string.ascii_uppercase[:13] + |
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string.ascii_lowercase[13:] + string.ascii_lowercase[:13] |
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) |
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) |
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if __name__ == "__main__": |
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"""Peform line-by-line rot-13 encoding on any files listed on our |
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command line or act as a standard UNIX filter (if no arguments |
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specified). |
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""" |
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import fileinput |
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for line in fileinput.input(): |
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print(rot13(line), end="")</lang> |
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=={{header|R}}== |
=={{header|R}}== |
Revision as of 08:23, 17 August 2009
![Task](http://static.miraheze.org/rosettacodewiki/thumb/b/ba/Rcode-button-task-crushed.png/64px-Rcode-button-task-crushed.png)
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
<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 $i } } print o
}</lang>
BASIC
CLS INPUT "Enter a string: ", s$ 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>
- include<stdlib.h>
- include<ctype.h>
- 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>
- include <iostream>
- include <istream>
- include <ostream>
- include <fstream>
- include <cstdlib>
- 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
<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>
Logo
<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:
<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).
<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
<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>
- !/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
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
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>
- import std
- 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.