Rot-13

Pete: Add Limbo rot13 (Luckily, I had already written/tested this.)


{{task|Encryption}}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, e.g., [[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 [[wp:Spoiler (media)|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 its 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.

=={{header|6502 Assembly}}==
Written for the BeebAsm assembler, which uses '&' to indicate a hexadecimal number. Call with the address of a zero terminated string in X and Y.
On exit X is preserved, Y is the length of the string and A is zero.

buffer = &70 ; or anywhere in zero page that's good

org &1900
.rot13
stx buffer
sty buffer+1
ldy #0
.loop lda (buffer),y
bne decode ; quit on ASCII 0
rts
.decode cmp #&7b ; high range
bcs next
cmp #&41 ; low range
bcc next
cmp #&4f
bcc add13
cmp #&5b
bcc sub13
cmp #&61
bcc next
cmp #&6f
bcc add13
bcs sub13 ; saves a byte over a jump
.next iny
jmp loop
.add13 adc #13 ; we only get here via bcc; so clc not needed
jmp storeit
.sub13 sec
sbc #13
.storeit sta (buffer),y
jmp next


=={{header|ACL2}}==
(include-book "arithmetic-3/top" :dir :system)

(defun char-btn (c low high)
(and (char>= c low)
(char<= c high)))

(defun rot-13-cs (cs)
(cond ((endp cs) nil)
((or (char-btn (first cs) #\a #\m)
(char-btn (first cs) #\A #\M))
(cons (code-char (+ (char-code (first cs)) 13))
(rot-13-cs (rest cs))))
((or (char-btn (first cs) #\n #\z)
(char-btn (first cs) #\N #\Z))
(cons (code-char (- (char-code (first cs)) 13))
(rot-13-cs (rest cs))))
(t (cons (first cs) (rot-13-cs (rest cs))))))

(defun rot-13 (s)
(coerce (rot-13-cs (coerce s 'list)) 'string))


=={{header|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;

=={{header|ALGOL 68}}==
{{trans|Modula-3}}

{{works with|ALGOL 68|Standard - no extensions to language used}}
{{works with|ALGOL 68G|Any - tested with release mk15-0.8b.fc9.i386}}

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 #

Sample run on linux:

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

=={{header|AppleScript}}==
Using '''do shell script'''
to rot13(textString)
do shell script "tr a-zA-Z n-za-mN-ZA-M <<<" & quoted form of textString
end rot13

Pure AppleScript solution
to rot13(textString)
local outChars
set outChars to {}
repeat with ch in (characters of textString)
if (ch >= "a" and ch <= "m") or (ch >= "A" and ch <= "M") then
set ch to character id (id of ch + 13)
else if (ch >= "n" and ch <= "z") or (ch >= "N" and ch <= "Z") then
set ch to character id (id of ch - 13)
end
set end of outChars to ch
end
return outChars as text
end rot13

Demo code:
rot13("nowhere ABJURER")
Output:
abjurer NOWHERE


=={{header|AutoHotkey}}==
Simple alphabet remapping method by Raccoon. Similar to a translate() function in many languages.
ROT13(string) ; by Raccoon July-2009
{
Static a := "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ "
Static b := "nopqrstuvwxyzabcdefghijklmNOPQRSTUVWXYZABCDEFGHIJKLM "
s=
Loop, Parse, string
{
c := substr(b,instr(a,A_LoopField,True),1)
if (c != " ")
s .= c
else
s .= A_LoopField
}
Return s
}


Simple ASCII math method by Raccoon. Add or subtract 13 depending on the character's decimal value.
ROT13(string) ; by Raccoon July-2009
{
s=
Loop, Parse, string
{
c := asc(A_LoopField)
if (c >= 97) && (c <= 109) || (c >= 65) && (c <= 77)
c += 13
else if (c >= 110) && (c <= 122) || (c >= 78) && (c <= 90)
c -= 13
s .= chr(c)
}
Return s
}


Code modified from [http://www.autohotkey.com/forum/viewtopic.php?t=8421 stringmod] by [http://www.autohotkey.com/forum/author-HugoV.html Hugo]: [http://www.autohotkey.com/forum/viewtopic.php?t=44657&postdays=0&postorder=asc&start=45 ahk discussion]
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 .= char
}
Return rStr
}


=={{header|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
}


=={{header|BASIC}}==
{{works with|QBasic}}

CLS
INPUT "Enter a string: ", s$
ans$ = ""
FOR a = 1 TO LEN(s$)
letter$ = MID$(s$, a, 1)
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$


===Alternate version===
This version does the rotation in-place without the use of a second variable.

INPUT "Enter a string "; Text$
FOR c% = 1 TO LEN(Text$)
SELECT CASE ASC(MID$(Text$, c%, 1))
CASE 65 TO 90
MID$(Text$, c%, 1) = CHR$(65 + ((ASC(MID$(Text$, c%, 1)) - 65 + 13) MOD 26))
CASE 97 TO 122
MID$(Text$, c%, 1) = CHR$(97 + ((ASC(MID$(Text$, c%, 1)) - 97 + 13) MOD 26))
END SELECT
NEXT c%
PRINT "Converted......: "; Text$


Sample output:
Enter a string ? Oolite quick Thargoid jumps lazy Vipers = blown up + special fx
Converted......: Bbyvgr dhvpx Gunetbvq whzcf ynml Ivcref = oybja hc + fcrpvny sk

See also: [[#BBC BASIC|BBC BASIC]], [[#FBSL|FBSL]], [[#GW-BASIC|GW-BASIC]], [[#Liberty BASIC|Liberty BASIC]], [[#Locomotive Basic|Locomotive Basic]], [[#PureBasic|PureBasic]], [[#Run BASIC|Run BASIC]], [[#TI-83 BASIC|TI-83 BASIC]], [[#Visual Basic .NET|Visual Basic .NET]], [[#ZX Spectrum Basic|ZX Spectrum Basic]]

=={{header|BBC BASIC}}==

REPEAT
INPUT A$
PRINT FNrot13(A$)
UNTIL FALSE
END

DEF FNrot13(A$)
LOCAL A%,B$,C$
IF A$="" THEN =""
FOR A%=1 TO LEN A$
C$=MID$(A$,A%,1)
IF C$<"A" OR (C$>"Z" AND C$<"a") OR C$>"z" THEN
B$=B$+C$
ELSE
IF (ASC(C$) AND &DF) B$=B$+CHR$(ASC(C$)+13)
ELSE
B$=B$+CHR$(ASC(C$)-13)
ENDIF
ENDIF
NEXT A%
=B$


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

=={{header|Burlesque}}==


blsq ) "HELLO WORLD"{{'A'Zr\\/Fi}m[13?+26.%'A'Zr\\/si}ww
"URYYB JBEYQ"
blsq ) "URYYB JBEYQ"{{'A'Zr\\/Fi}m[13?+26.%'A'Zr\\/si}ww
"HELLO WORLD"


=={{header|C}}==
#include
#include
#include

#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 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;
}


===Alternative version===
This version rot13'd lowercase and uppercase letters.

File can be processing simply by piping:
cat filename | ./rot13

#include
#include

char rot13_char(char s);

int main(int argc, char *argv[]) {
int c;
if (argc != 1) {
fprintf(stderr, "Usage: %s\n", argv[0]);
return 1;
}
while((c = getchar()) != EOF) {
putchar(rot13_char(c));
}

return 0;
}

char rot13_char(char c) {
if (isalpha(c)) {
char alpha = islower(c) ? 'a' : 'A';
return (c - alpha + 13) % 26 + alpha;
}
return c;
}


=={{header|C sharp|C#}}==
using System;
using System.IO;
using System.Linq;
using System.Text;

class Program
{
static char Rot13(char c)
{
if ('a' <= c && c <= 'm' || 'A' <= c && c <= 'M')
{
return (char)(c + 13);
}
if ('n' <= c && c <= 'z' || 'N' <= c && c <= 'Z')
{
return (char)(c - 13);
}
return c;
}

static string Rot13(string s)
{
return new StringBuilder().Append(s.Select(Rot13).ToArray()).ToString();
}


static void Main(string[] args)
{
foreach (var file in args.Where(file => File.Exists(file)))
{
Console.WriteLine(Rot13(File.ReadAllText(file)));
}
if (!args.Any())
{
Console.WriteLine(Rot13(Console.In.ReadToEnd()));
}
}
}


=={{header|C++}}==
#include
#include
#include
#include
#include
#include

// 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;
}


Here is an other approach which can rotate by any number:
{{libheader|Boost}}
#include
#include
#include // output_filter
#include // put
#include
#include
namespace io = boost::iostreams;

class rot_output_filter : public io::output_filter
{
public:
explicit rot_output_filter(int r=13):rotby(r),negrot(alphlen-r){};

template
bool put(Sink& dest, int c){
char uc = toupper(c);

if(('A' <= uc) && (uc <= ('Z'-rotby)))
c = c + rotby;
else if ((('Z'-rotby) <= uc) && (uc <= 'Z'))
c = c - negrot;
return boost::iostreams::put(dest, c);
};
private:
static const int alphlen = 26;
const int rotby;
const int negrot;
};

int main(int argc, char *argv[])
{
io::filtering_ostream out;
out.push(rot_output_filter(13));
out.push(std::cout);

if (argc == 1) out << std::cin.rdbuf();
else for(int i = 1; i < argc; ++i){
std::ifstream in(argv[i]);
out << in.rdbuf();
}
}



=={{header|Clojure}}==
(defn rot-13 [c]
(let [i (int c)]
(cond
(or (and (>= i (int \a)) (<= i (int \m)))
(and (>= i (int \A)) (<= i (int \M))))
(char (+ i 13))
(or (and (>= i (int \n)) (<= i (int \z)))
(and (>= i (int \N)) (<= i (int \Z))))
(char (- i 13))
:else c)))

(apply str (map rot-13 "abcxyzABCXYZ")) ;; output "nopklmNOPKLM"

An alternative implementation using a closure or two:
(let [A (into #{} "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ")
A-map (zipmap A (take 52 (drop 26 (cycle A))))]

(defn rot13[in-str]
(reduce str (map #(if (A %1) (A-map %1) %1) in-str))))

(rot13 "The Quick Brown Fox Jumped Over The Lazy Dog!") ;; produces "Gur Dhvpx Oebja Sbk Whzcrq Bire Gur Ynml Qbt!"


=={{header|COBOL}}==
IDENTIFICATION DIVISION.
PROGRAM-ID. rot-13.

DATA DIVISION.
LOCAL-STORAGE SECTION.
78 STR-LENGTH VALUE 100.

78 normal-lower VALUE "abcdefghijklmnopqrstuvwxyz".
78 rot13-lower VALUE "nopqrstuvwxyzabcdefghijklm".

78 normal-upper VALUE "ABCDEFGHIJKLMNOPQRSTUVWXYZ".
78 rot13-upper VALUE "NOPQRSTUVWXYZABCDEFGHIJKLM".

LINKAGE SECTION.
01 in-str PIC X(STR-LENGTH).
01 out-str PIC X(STR-LENGTH).

PROCEDURE DIVISION USING VALUE in-str, REFERENCE out-str.
MOVE in-str TO out-str

INSPECT out-str CONVERTING normal-lower TO rot13-lower
INSPECT out-str CONVERTING normal-upper TO rot13-upper

GOBACK
.


=={{header|Common Lisp}}==
The standard gives implementations great leeway with respect to character encodings, so we can't rely on the convenient properties of ASCII.
(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))


====Assuming ASCII Character Set====
Though the standard intentionally doesn't specify encoding, every popular implementation today uses ASCII.
(defun rot13 (string)
(map 'string
(lambda (char &aux (code (char-code char)))
(if (alpha-char-p char)
(if (> (- code (char-code (if (upper-case-p char)
#\A #\a))) 12)
(code-char (- code 13))
(code-char (+ code 13)))
char))
string))

(rot13 "Moron") ; -> "Zbeba"


=={{header|Cubescript}}==
alias rot13 [
push alpha [
"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"
"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"
] [ push chars [] [
loop i (strlen $arg1) [
looplist n $alpha [
if (! (listlen $chars)) [
alias chars (? (> (listindex $n (substr $arg1 $i 1)) -1) $n [])
]
]
alias arg1 (
concatword (substr $arg1 0 $i) (
? (listlen $chars) (
at $chars (
mod (+ (
listindex $chars (substr $arg1 $i 1)
) 13 ) (listlen $chars)
)
) (substr $arg1 $i 1)
) (substr $arg1 (+ $i 1) (strlen $arg1))
)
alias chars []
]
] ]
result $arg1
]


Usage:
>>> rot13 "Hello World"
> Uryyb Jbeyq
>>> rot13 "Gur Dhvpx Oebja Sbk Whzcf Bire Gur Ynml Qbt!"
> The Quick Brown Fox Jumps Over The Lazy Dog!


=={{header|D}}==
===Using Standard Functions===
import std.stdio;
import std.ascii: letters, U = uppercase, L = lowercase;
import std.string: makeTrans, translate;

immutable r13 = makeTrans(letters,
//U[13 .. $] ~ U[0 .. 13] ~
U[13 .. U.length] ~ U[0 .. 13] ~
L[13 .. L.length] ~ L[0 .. 13]);

void main() {
writeln("This is the 1st test!".translate(r13, null));
}

{{out}}
The Quick Brown Fox Jumps Over The Lazy Dog!

===Imperative Implementation===
import std.stdio, std.string, std.traits;

pure S rot13(S)(in S s) if (isSomeString!S) {
return rot(s, 13);
}

pure S rot(S)(in S s, in int key) if (isSomeString!S) {
auto r = s.dup;

foreach (i, ref c; r) {
if ('a' <= c && c <= 'z')
c = ((c - 'a' + key) % 26 + 'a');
else if ('A' <= c && c <= 'Z')
c = ((c - 'A' + key) % 26 + 'A');
}
return cast(S) r;
}

void main() {
"Gur Dhvpx Oebja Sbk Whzcf Bire Gur Ynml Qbt!".rot13().writeln();
}


=={{header|Déjà Vu}}==

rot-13:
)
for ch in chars swap:
ord ch
if <= 65 dup:
if >= 90 dup:
+ 13 - swap 65
+ 65 % swap 26
if <= 97 dup:
if >= 122 dup:
+ 13 - swap 97
+ 97 % swap 26
chr
concat(

!print rot-13 "Snape kills Frodo with Rosebud."

{{out}}
Fancr xvyyf Sebqb jvgu Ebfrohq.


=={{header|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 }) }
}


=={{header|Erlang}}==

rot13(Str) ->
F = fun(C) when (C >= $A andalso C =< $M); (C >= $a andalso C =< $m) -> C + 13;
(C) when (C >= $N andalso C =< $Z); (C >= $n andalso C =< $z) -> C - 13;
(C) -> C
end,
lists:map(F, Str).


=={{header|Euphoria}}==
{{works with|Euphoria|4.0.0}}

include std/types.e
include std/text.e

atom FALSE = 0
atom TRUE = not FALSE

function Rot13( object oStuff )
integer iOffset
integer bIsUpper
object oResult
sequence sAlphabet = "abcdefghijklmnopqrstuvwxyz"
if sequence(oStuff) then
oResult = repeat( 0, length( oStuff ) )
for i = 1 to length( oStuff ) do
oResult[ i ] = Rot13( oStuff[ i ] )
end for
else
bIsUpper = FALSE
if t_upper( oStuff ) then
bIsUpper = TRUE
oStuff = lower( oStuff )
end if
iOffset = find( oStuff, sAlphabet )
if iOffset != 0 then
iOffset += 13
iOffset = remainder( iOffset, 26 )
if iOffset = 0 then iOffset = 1 end if
oResult = sAlphabet[iOffset]
if bIsUpper then
oResult = upper(oResult)
end if
else
oResult = oStuff --sprintf( "%s", oStuff )
end if
end if
return oResult
end function

puts( 1, Rot13( "abjurer NOWHERE." ) & "\n" )


=={{header|F_Sharp|F#}}==
Illustrates turning a string into an array of chars then composition of type casting with a conversion function. We create a composite that converts its input to an integer, calls the convertion function and
then casts to a char type. The result is an array of modified chars that we can use to create a new string.
let rot13 (s : string) =
let rot c =
match c with
| c when c > 64 && c < 91 -> ((c - 65 + 13) % 26) + 65
| c when c > 96 && c < 123 -> ((c - 97 + 13) % 26) + 97
| _ -> c
s |> Array.of_seq
|> Array.map(int >> rot >> char)
|> (fun seq -> new string(seq))


=={{header|Factor}}==
#! /usr/bin/env factor

USING: kernel io ascii math combinators sequences ;
IN: rot13

: rot-base ( ch ch -- ch ) [ - 13 + 26 mod ] keep + ;

: rot13-ch ( ch -- ch )
{
{ [ dup letter? ] [ CHAR: a rot-base ] }
{ [ dup LETTER? ] [ CHAR: A rot-base ] }
[ ]
}
cond ;

: rot13 ( str -- str ) [ rot13-ch ] map ;

: main ( -- )
[ readln dup ]
[ rot13 print flush ]
while
drop ;

MAIN: main


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

=={{header|Fantom}}==


class Rot13
{
static Str rot13 (Str input)
{
Str result := ""
input.each |Int c|
{
if ((c.lower >= 'a') && (c.lower <= 'm'))
result += (c+13).toChar
else if ((c.lower >= 'n') && (c.lower <= 'z'))
result += (c-13).toChar
else
result += c.toChar
}
return result
}

public static Void main (Str[] args)
{
if (args.size == 1)
{ // process each line of given file
Str filename := args[0]
File(filename.toUri).eachLine |Str line|
{
echo (rot13(line))
}
}
else
{
echo ("Test:")
Str text := "abcstuABCSTU123!+-"
echo ("Text $text becomes ${rot13(text)}")
}
}
}


=={{header|FBSL}}==
Implements a circular queue, finds the required character and then rotates the queue forward 13 places. Would do as a solution to Caesar Cipher with a different rotation number. Please note that FBSL is not case sensitive, thus the use of lstrcmp.
#APPTYPE CONSOLE

REM Create a CircularQueue object
REM CQ.Store item
REM CQ.Find items
REM CQ.Forward nItems
REM CQ.Recall

REM SO CQ init WITH "A"... "Z"
REM CQ.Find "B"
REM QC.Forward 13
REM QC.Recall

CLASS CircularQueue
items[]
head
tail
here

SUB INITIALIZE(dArray)
head = 0
tail = 0
here = 0
FOR DIM i = LBOUND(dArray) TO UBOUND(dArray)
items[tail] = dArray[i]
tail = tail + 1
NEXT
END SUB

SUB TERMINATE()
REM
END SUB

METHOD Put(s AS STRING)
items[tail] = s
tail = tail + 1
END METHOD

METHOD Find(s AS STRING)
FOR DIM i = head TO tail - 1
IF items[i] = s THEN
here = i
RETURN TRUE
END IF
NEXT
RETURN FALSE
END METHOD

METHOD Move(n AS INTEGER)
DIM bound AS INTEGER = UBOUND(items) + 1
here = (here + n) MOD bound
END METHOD

METHOD Recall()
RETURN items[here]
END METHOD

PROPERTY Size()
RETURN COUNT(items)
END PROPERTY
END CLASS

DIM CQ AS NEW CircularQueue({"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"})

DIM c AS STRING
DIM isUppercase AS INTEGER
DIM s AS STRING = "nowhere ABJURER"

FOR DIM i = 1 TO LEN(s)
c = MID(s, i, 1)
isUppercase = lstrcmp(LCASE(c), c)
IF CQ.Find(UCASE(c)) THEN
CQ.Move(13)
PRINT IIF(isUppercase, UCASE(CQ.Recall()), LCASE(CQ.Recall())) ;
ELSE
PRINT c;
END IF
NEXT

PAUSE


=={{header|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


=={{header|Fortran}}==
{{works with|Fortran|90 and later}}
program test_rot_13

implicit none
integer, parameter :: len_max = 256
integer, parameter :: unit = 10
character (len_max) :: file
character (len_max) :: fmt
character (len_max) :: line
integer :: arg
integer :: arg_max
integer :: iostat

write (fmt, '(a, i0, a)') '(a', len_max, ')'
arg_max = iargc ()
if (arg_max > 0) then
! Encode all files listed on the command line.
do arg = 1, arg_max
call getarg (arg, file)
open (unit, file = file, iostat = iostat)
if (iostat /= 0) cycle
do
read (unit, fmt = fmt, iostat = iostat) line
if (iostat /= 0) exit
write (*, '(a)') trim (rot_13 (line))
end do
close (unit)
end do
else
! Encode standard input.
do
read (*, fmt = fmt, iostat = iostat) line
if (iostat /= 0) exit
write (*, '(a)') trim (rot_13 (line))
end do
end if

contains

function rot_13 (input) result (output)

implicit none
character (len_max), intent (in) :: input
character (len_max) :: output
integer :: i

output = input
do i = 1, len_trim (output)
select case (output (i : i))
case ('A' : 'M', 'a' : 'm')
output (i : i) = char (ichar (output (i : i)) + 13)
case ('N' : 'Z', 'n' : 'z')
output (i : i) = char (ichar (output (i : i)) - 13)
end select
end do

end function rot_13

end program test_rot_13

Note: iargc and getarg are common extensions that are implemented by e.g. the Intel Fortran Compiler, G95 and gfortran.

Sample usage:
> cat foo.txt
foo
> cat bar.txt
bar
> ./rot_13 foo.txt bar.txt
sbb
one
> ./rot_13 < foo.txt
sbb
> cat foo.txt bar.txt | ./rot_13
sbb
one

=={{header|GAP}}==
rot13 := function(s)
local upper, lower, c, n, t;
upper := "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
lower := "abcdefghijklmnopqrstuvwxyz";
t := [ ];
for c in s do
n := Position(upper, c);
if n <> fail then
Add(t, upper[((n+12) mod 26) + 1]);
else
n := Position(lower, c);
if n <> fail then
Add(t, lower[((n+12) mod 26) + 1]);
else
Add(t, c);
fi;
fi;
od;
return t;
end;

a := "England expects that every man will do his duty";
# "England expects that every man will do his duty"
b := rot13(a);
# "Ratynaq rkcrpgf gung rirel zna jvyy qb uvf qhgl"
c := rot13(b);
# "England expects that every man will do his duty"


=={{header|Gema}}==
/[a-mA-M]/=@int-char{@add{@char-int{$1};13}}
/[n-zN-Z]/=@int-char{@sub{@char-int{$1};13}}


=={{header|GML}}==

#define rot13
var in, out, i, working;
in = argument0;
out = "";
for (i = 1; i <= string_length(in); i += 1)
{
working = ord(string_char_at(in, i));
if ((working > 64) && (working < 91))
{
working += 13;
if (working > 90)
{
working -= 26;
}
}
else if ((working > 96) && (working < 123))
{
working += 13;
if (working > 122) working -= 26;
}
out += chr(working);
}
return out;


The above code is called like this:
show_message(rot13("My dog has fleas!"));

Output (in a message box):
Zl qbt unf syrnf!

=={{header|Go}}==
package main

import (
"fmt"
"strings"
)

func rot13char(c rune) rune {
if c >= 'a' && c <= 'm' || c >= 'A' && c <= 'M' {
return c + 13
} else if c >= 'n' && c <= 'z' || c >= 'N' && c <= 'Z' {
return c - 13
}
return c
}

func rot13(s string) string {
return strings.Map(rot13char, s)
}

func main() {
fmt.Println(rot13("nowhere ABJURER"))
}

Output:

abjurer NOWHERE


=={{header|Groovy}}==
Solution:
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}
}


Test program:
println rot13("Noyr jnf V, 'rer V fnj Ryon.")

Output:
Able was I, 'ere I saw Elba.


=={{header|GW-BASIC}}==
10 INPUT "Enter a string: ",A$
20 GOSUB 50
30 PRINT B$
40 END
50 FOR I=1 TO LEN(A$)
60 N=ASC(MID$(A$,I,1))
70 E=255
80 IF N>64 AND N<91 THEN E=90 ' uppercase
90 IF N>96 AND N<123 THEN E=122 ' lowercase
100 IF E<255 THEN N=N+13
110 IF N>E THEN N=N-26
120 B$=B$+CHR$(N)
130 NEXT
140 RETURN


=={{header|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.

=={{header|HicEst}}==
CHARACTER c, txt='abc? XYZ!', cod*100

DO i = 1, LEN_TRIM(txt)
c = txt(i)
n = ICHAR(txt(i))
IF( (c >= 'a') * (c <= 'm') + (c >= 'A') * (c <= 'M') ) THEN
c = CHAR( ICHAR(c) + 13 )
ELSEIF( (c >= 'n') * (c <= 'z') + (c >= 'N') * (c <= 'Z') ) THEN
c = CHAR( ICHAR(c) - 13 )
ENDIF

cod(i) = c
ENDDO

WRITE(ClipBoard, Name) txt, cod ! txt=abc? XYZ!; cod=nop? KLM!;
END


=={{header|Icon}} and {{header|Unicon}}==
procedure main(arglist)
file := open(arglist[1],"r") | &input
every write(rot13(|read(file)))
end

procedure rot13(s) #: returns rot13(string)
static a,n
initial {
a := &lcase || &ucase
(&lcase || &lcase) ? n := ( move(13), move(*&lcase) )
(&ucase || &ucase) ? n ||:= ( move(13), move(*&ucase) )
}
return map(s,a,n)
end

This example uses a number of Icon features.
* alternation ( x | y ) selects and opens a file if supplied or fall back to standard output
* repeated alternation ( |x ) is used to generate the contents of the input file
* the rot13 procedure does a one time setup (initially) of persistent (static) mapping strings so the procedure can return the rot13 mapping
* the setup exploits the ordered cset variables &lcase and &ucase coercing them into strings
* the rot13 mapping string is then aggregated with strings taken by offsetting into double length values to avoid unnecessary and messy rotation

=={{header|J}}==
rot13=: {&((65 97+/~i.2 13) |.@[} i.256)&.(a.&i.)

For example:

rot13 'abc! ABC!'
nop! NOP!

Compare with the solution to the [[Change_string_case#J|Change String Case]] task.

=={{header|Java}}==
import java.io.*;

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 (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) {
StringBuilder retVal = new StringBuilder();
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.append(a);
}
return retVal.toString();
}
}


=={{header|JavaScript}}==
function rot13(c) {
return c.replace(/([a-m])|([n-z])/ig, function($0,$1,$2) {
return String.fromCharCode($1 ? $1.charCodeAt(0) + 13 : $2 ? $2.charCodeAt(0) - 13 : 0) || $0;
});
}
rot13("ABJURER nowhere") // NOWHERE abjurer


TDD with Jasmine using Underscore.js


function rot13(value){
if (!value)
return "";

function singleChar(c) {
if (c.toUpperCase() < "A" || c.toUpperCase() > "Z")
return c;

if (c.toUpperCase() <= "M")
return String.fromCharCode(c.charCodeAt(0) + 13);

return String.fromCharCode(c.charCodeAt(0) - 13);
}

return _.map(value.split(""), singleChar).join("");
}

describe("Rot-13", function() {
it("Given nothing will return nothing", function() {
expect(rot13()).toBe("");
});

it("Given empty string will return empty string", function() {
expect(rot13("")).toBe("");
});

it("Given A will return N", function() {
expect(rot13("A")).toBe("N");
});

it("Given B will return O", function() {
expect(rot13("B")).toBe("O");
});

it("Given N will return A", function() {
expect(rot13("N")).toBe("A");
});

it("Given Z will return M", function() {
expect(rot13("Z")).toBe("M");
});

it("Given ZA will return MN", function() {
expect(rot13("ZA")).toBe("MN");
});

it("Given HELLO will return URYYB", function() {
expect(rot13("HELLO")).toBe("URYYB");
});

it("Given hello will return uryyb", function() {
expect(rot13("hello")).toBe("uryyb");
});


it("Given hello1 will return uryyb1", function() {
expect(rot13("hello1")).toBe("uryyb1");
});
});


=={{header|Julia}}==
function rot13(c::Char)
c in 'a':'z' ? 'a' + (c - 'a' + 13)%26 :
c in 'A':'Z' ? 'A' + (c - 'A' + 13)%26 :
c
end

rot13(s::String) = map(rot13,CharString(s...))


{{out}}
julia> rot13("abcdefghijklmnopqrtuvwxyz 123 ABCDEFGHIJKLMNOPQRTUVWXYZ")
"nopqrstuvwxyzabcdeghijklm 123 NOPQRSTUVWXYZABCDEGHIJKLM"


=={{header|K}}==
rot13: {a:+65 97+\:2 13#!26;_ci@[!256;a;:;|a]_ic x}

rot13 "Testing! 1 2 3"
"Grfgvat! 1 2 3"




=={{header|LabVIEW}}==
{{VI solution|LabVIEW_Rot-13.png}}

=={{header|Lasso}}==

// Extend the string type

define string->rot13 => {
local(
rot13 = bytes,
i, a, b
)

with char in .eachCharacter
let int = #char->integer
do {
// We only modify these ranges, set range if we should modify
#int >= 65 and #int < 91 ? local(a=65,b=91) |
#int >= 97 and #int < 123 ? local(a=97,b=123) | local(a=0,b=0)

if(#a && #b) => {
#i = (#int+13) % #b // loop back if past ceiling (#b)
#i += #a * (1 - #i / #a) // offset if below floor (#a)
#rot13->import8bits(#i) // import the new character
else
#rot13->append(#char) // just append the character
}
}

return #rot13->asstring
}


;Example:
'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz'->rot13

'Where do you find a dog with no legs?
Evtug jurer lbh yrsg uvz.'->rot13


{{out}}
NOPQRSTUVWXYZABCDEFGHIJKLMnopqrstuvwxyzabcdefghijklm

Jurer qb lbh svaq n qbt jvgu ab yrtf?
Right where you left him.


;Another implementation:

define rot13(p::string) => {
local(
rot13 = bytes,
a = bytes('ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz'),
b = bytes('NOPQRSTUVWXYZABCDEFGHIJKLMnopqrstuvwxyzabcdefghijklm'),
i
)

with char in #p->eachCharacter
let c = bytes(#char) do {
#i = #a->find(#b)
#i ? #rot13->import8bits(#b->get(#i)) | #rot13->append(#c)
}

return #rot13->asString
}

rot13('ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz')


{{out}}

NOPQRSTUVWXYZABCDEFGHIJKLMnopqrstuvwxyzabcdefghijklm


=={{header|Liberty BASIC}}==
Liberty BASIC string comparisons are not ascii-based.
Verbose version:
input "Type some text to be encoded, then ENTER. ";tx$

tex$ = Rot13$(tx$)
print tex$
'check
print Rot13$(tex$)

wait

Function Rot13$(t$)
if t$="" then
Rot13$=""
exit function
end if
for i = 1 to len(t$)
c$=mid$(t$,i,1)
ch$=c$
if (asc(c$)>=asc("A")) and (asc(c$)<=asc("Z")) then
ch$=chr$(asc(c$)+13)
if (asc(ch$)>asc("Z")) then ch$=chr$(asc(ch$)-26)
end if
if (asc(c$)>=asc("a")) and (asc(c$)<=asc("z")) then
ch$=chr$(asc(c$)+13)
if (asc(ch$)>asc("z")) then ch$=chr$(asc(ch$)-26)
end if
rot$=rot$+ch$
next
Rot13$=rot$
end function


Concise:
Function Rot13$(t$)
for i = 1 to len(t$)
ch$=mid$(t$,i,1)
if (asc(ch$)>=asc("A")) and (asc(ch$)<=asc("Z")) then
ch$=chr$(asc("A")+ (asc(ch$)-asc("A")+13) mod 26)
end if
if (asc(ch$)>=asc("a")) and (asc(ch$)<=asc("z")) then
ch$=chr$(asc("a")+ (asc(ch$)-asc("a")+13) mod 26)
end if
Rot13$=Rot13$+ch$
next
end function


=={{header|Limbo}}==

A fairly straightforward version that uses a lookup table, based on Inferno's cat(1).

implement Rot13;

include "sys.m"; sys: Sys;
include "draw.m";

Rot13: module
{
init: fn(ctxt: ref Draw->Context, argv: list of string);
};

stdout: ref Sys->FD;
tab: array of int;

init(nil: ref Draw->Context, args: list of string)
{
sys = load Sys Sys->PATH;
stdout = sys->fildes(1);
inittab();
args = tl args;
if(args == nil)
args = "-" :: nil;
for(; args != nil; args = tl args){
file := hd args;
if(file != "-"){
fd := sys->open(file, Sys->OREAD);
if(fd == nil){
sys->fprint(sys->fildes(2), "rot13: cannot open %s: %r\n", file);
raise "fail:bad open";
}
rot13cat(fd, file);
}else
rot13cat(sys->fildes(0), "");
}
}

inittab()
{
tab = array[256] of int;
for(i := 0; i < 256; i++)
tab[i] = i;

for(i = 'a'; i <= 'z'; i++)
tab[i] = (((i - 'a') + 13) % 26) + 'a';
for(i = 'A'; i <= 'Z'; i++)
tab[i] = (((i - 'A') + 13) % 26) + 'A';
}


rot13(s: string): string
{
for(i := 0; i < len s; i++) {
if(s[i] < 256)
s[i] = tab[s[i]];
}
return s;
}

rot13cat(fd: ref Sys->FD, file: string)
{
buf := array[Sys->ATOMICIO] of byte;

while((n := sys->read(fd, buf, len buf)) > 0) {
obuf := array of byte (rot13(string buf));
if(sys->write(stdout, obuf, n) < n) {
sys->fprint(sys->fildes(2), "rot13: write error: %r\n");
raise "fail:write error";
}
}
if(n < 0) {
sys->fprint(sys->fildes(2), "rot13: error reading %s: %r\n", file);
raise "fail:read error";
}
}


=={{header|LiveCode}}==
function rot13 S
repeat with i = 1 to length(S)
get chartonum(char i of S)
if it < 65 or it > 122 or (it > 90 and it < 97) then next repeat
put char it - 64 of "NOPQRSTUVWXYZABCDEFGHIJKLM nopqrstuvwxyzabcdefghijklm" into char i of S
end repeat
return S
end rot13



=={{header|Locomotive Basic}}==

10 INPUT "Enter a string: ",a$
20 GOSUB 50
30 PRINT b$
40 END
50 FOR i=1 TO LEN(a$)
60 n=ASC(MID$(a$,i,1))
70 e=255
80 IF n>64 AND n<91 THEN e=90 ' uppercase
90 IF n>96 AND n<123 THEN e=122 ' lowercase
100 IF e<255 THEN n=n+13
110 IF n>e THEN n=n-26
120 b$=b$+CHR$(n)
130 NEXT
140 RETURN


=={{header|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

=={{header|Lua}}==
function rot(l, o) return (l < 26 and l > -1) and string.char((l+13)%26 + o) end
a, A = string.byte'a', string.byte'A'
val = io.read()
val = val:gsub("(.)", function(l) return rot(l:byte()-a,a) or rot(l:byte()-A,A) or l end)
print(val)


=={{header|Maple}}==
There is a built-in command for this in Maple.
> StringTools:-Encode( "The Quick Brown Fox Jumped Over The Lazy Dog!", encoding = rot13 );
"Gur Dhvpx Oebja Sbk Whzcrq Bire Gur Ynml Qbt!"


=={{header|Mathematica}}==
ruleslower=Thread[#-> RotateLeft[#, 13]]&[CharacterRange["a", "z"]];
rulesupper=Thread[#-> RotateLeft[#, 13]]&[CharacterRange["A", "Z"]];
rules=Join[ruleslower,rulesupper];
text="Hello World! Are you there!?"
text=StringReplace[text,rules]
text=StringReplace[text,rules]

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


=={{header|MATLAB}}==
function r=rot13(s)
if ischar(s)
r=s; % preallocation and copy of non-letters
for i=1:size(s,1)
for j=1:size(s,2)
if isletter(s(i,j))
if s(i,j)>=97 % lower case
base = 97;
else % upper case
base = 65;
end
r(i,j)=char(mod(s(i,j)-base+13,26)+base);
end
end
end
else
error('Argument must be a CHAR')
end
end

Call it like this:
>> rot13('Hello World!')

ans =

Uryyb Jbeyq!


It is possible to vectorize this code, the example below is not fully vectorized in order to make the order of operations clear. It is possible to reduce this solution to two lines by integrating the "selectedLetters" calculations directly into the line following them.

function text = rot13(text)
if ischar(text)

selectedLetters = ( (text >= 'A') & (text <= 'Z') ); %Select upper case letters
text(selectedLetters) = char( mod( text(selectedLetters)-'A'+13,26 )+'A' );

selectedLetters = ( (text >= 'a') & (text <= 'z') ); %Select lower case letters
text(selectedLetters) = char( mod( text(selectedLetters)-'a'+13,26 )+'a' );

else
error('Argument must be a string.')
end
end


Sample Output:
>> plainText = char((64:123))

plainText =

@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\]^_`abcdefghijklmnopqrstuvwxyz{

>> rot13(plainText)

ans =

@NOPQRSTUVWXYZABCDEFGHIJKLM[\]^_`nopqrstuvwxyzabcdefghijklm{


=={{header|Maxima}}==
rot13(a) := simplode(map(ascii, map(lambda([n],
if (n >= 65 and n <= 77) or (n >= 97 and n <= 109) then n + 13
elseif (n >= 78 and n <= 90) or (n >= 110 and n <= 122) then n - 13
else n), map(cint, sexplode(a)))))$

lowercase: "abcdefghijklmnopqrstuvwxyz"$
uppercase: "ABCDEFGHIJKLMNOPQRSTUVWXYZ"$

rot13(lowercase);
"nopqrstuvwxyzabcdefghijklm"

rot13(uppercase);
"NOPQRSTUVWXYZABCDEFGHIJKLM"

rot13("The quick brown fox jumps over the lazy dog");
"Gur dhvpx oebja sbk whzcf bire gur ynml qbt"

rot13(%);
"The quick brown fox jumps over the lazy dog"


=={{header|Mirah}}==
def rot13 (value:string)
result = ""
d = ' '.toCharArray[0]
value.toCharArray.each do |c|
testChar = Character.toLowerCase(c)
if testChar <= 'm'.toCharArray[0] && testChar >= 'a'.toCharArray[0] then
d = char(c + 13)
end
if testChar <= 'z'.toCharArray[0] && testChar >= 'n'.toCharArray[0] then
d = char(c - 13)
end
result += d
end
result
end


puts rot13("abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ")


=={{header|MMIX}}==
// main registers
p IS $255 % text pointer
c GREG % char
cc GREG % uppercase copy of c
u GREG % all purpose

LOC Data_Segment
GREG @
Test BYTE "dit is een bericht voor de keizer",#a,0

LOC #100
Main LDA p,Test
TRAP 0,Fputs,StdOut % show text to encrypt
LDA p,Test % points to text to encrypt
JMP 4F
// do in place text encryption
% REPEAT
2H ADD cc,c,0 % copy char
SUB cc,cc,' ' % make uppercase
CMP u,cc,'A'
BN u,3F % IF c < 'A' OR c > 'Z' THEN next char
CMP u,cc,'Z'
BP u,3F
CMP u,cc,'N' % ELSE
BN u,1F % IF c < 'N' THEN encrypt 'up'
SUB c,c,26 % ELSE char ready for encrypt 'down'
1H INCL c,13 % encrypt char
STBU c,p % replace char with encrypted char
3H INCL p,1 % move to next char
4H LDBU c,p % get next char
PBNZ c,2B % UNTIL EOT
// print result
LDA p,Test
TRAP 0,Fputs,StdOut % show encrypted text
TRAP 0,Halt,0

Example:
~/MIX/MMIX/Progs> mmix rot13simpl
dit is een bericht voor de keizer
qvg vf rra orevpug ibbe qr xrvmre


=={{header|Modula-3}}==
This implementation reads from '''stdin''' and writes to '''stdout'''.
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.


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


=={{header|MUMPS}}==
Rot13(in) New low,rot,up
Set up="ABCDEFGHIJKLMNOPQRSTUVWXYZ"
Set low="abcdefghijklmnopqrstuvwxyz"
Set rot=$Extract(up,14,26)_$Extract(up,1,13)
Set rot=rot_$Extract(low,14,26)_$Extract(low,1,13)
Quit $Translate(in,up_low,rot)

Write $$Rot13("Hello World!") ; Uryyb Jbeyq!
Write $$Rot13("ABCDEFGHIJKLMNOPQRSTUVWXYZ") ; NOPQRSTUVWXYZABCDEFGHIJKLM


=={{header|NetRexx}}==
This sample leverages the code demonstrated in the [[Caesar cipher#NetRexx|Caesar cipher – NetRexx]] task.
/* NetRexx */
options replace format comments java crossref savelog symbols nobinary

parse arg fileNames

rdr = BufferedReader

do
if fileNames.length > 0 then do
loop n_ = 1 for fileNames.words
fileName = fileNames.word(n_)
rdr = BufferedReader(FileReader(File(fileName)))
encipher(rdr)
end n_
end
else do
rdr = BufferedReader(InputStreamReader(System.in))
encipher(rdr)
end
catch ex = IOException
ex.printStackTrace
end

return

method encipher(rdr = BufferedReader) public static signals IOException

loop label l_ forever
line = rdr.readLine
if line = null then leave l_
say rot13(line)
end l_
return

method rot13(input) public static signals IllegalArgumentException

return caesar(input, 13, isFalse)

method caesar(input = Rexx, idx = int, caps = boolean) public static signals IllegalArgumentException

if idx < 1 | idx > 25 then signal IllegalArgumentException()

-- 12345678901234567890123456
itab = 'ABCDEFGHIJKLMNOPQRSTUVWXYZ'
shift = itab.length - idx
parse itab tl +(shift) tr
otab = tr || tl

if caps then input = input.upper

cipher = input.translate(itab || itab.lower, otab || otab.lower)

return cipher

method caesar_encipher(input = Rexx, idx = int, caps = boolean) public static signals IllegalArgumentException

return caesar(input, idx, caps)

method caesar_decipher(input = Rexx, idx = int, caps = boolean) public static signals IllegalArgumentException

return caesar(input, int(26) - idx, isFalse)

method caesar_encipher(input = Rexx, idx = int) public static signals IllegalArgumentException

return caesar(input, idx, isFalse)

method caesar_decipher(input = Rexx, idx = int) public static signals IllegalArgumentException

return caesar(input, int(26) - idx, isFalse)

method caesar_encipher(input = Rexx, idx = int, opt = Rexx) public static signals IllegalArgumentException

return caesar(input, idx, opt)

method caesar_decipher(input = Rexx, idx = int, opt = Rexx) public static signals IllegalArgumentException

return caesar(input, int(26) - idx, opt)

method caesar(input = Rexx, idx = int, opt = Rexx) public static signals IllegalArgumentException

if opt.upper.abbrev('U') >= 1 then caps = isTrue
else caps = isFalse

return caesar(input, idx, caps)

method caesar(input = Rexx, idx = int) public static signals IllegalArgumentException

return caesar(input, idx, isFalse)

method isTrue public static returns boolean
return (1 == 1)

method isFalse public static returns boolean
return \isTrue


'''Output''' ''(using the source file as input)'':

/* ArgErkk */
bcgvbaf ercynpr sbezng pbzzragf wnin pebffers fnirybt flzobyf abovanel

cnefr net svyrAnzrf

eqe = OhssrerqErnqre

qb
vs svyrAnzrf.yratgu > 0 gura qb
ybbc a_ = 1 sbe svyrAnzrf.jbeqf
svyrAnzr = svyrAnzrf.jbeq(a_)
eqe = OhssrerqErnqre(SvyrErnqre(Svyr(svyrAnzr)))
rapvcure(eqe)
raq a_
raq
ryfr qb
eqe = OhssrerqErnqre(VachgFgernzErnqre(Flfgrz.va))
rapvcure(eqe)
raq
pngpu rk = VBRkprcgvba
rk.cevagFgnpxGenpr
raq

erghea

zrgubq rapvcure(eqe = OhssrerqErnqre) choyvp fgngvp fvtanyf VBRkprcgvba

ybbc ynory y_ sberire
yvar = eqe.ernqYvar
vs yvar = ahyy gura yrnir y_
fnl ebg13(yvar)
raq y_
erghea

zrgubq ebg13(vachg) choyvp fgngvp fvtanyf VyyrtnyNethzragRkprcgvba

erghea pnrfne(vachg, 13, vfSnyfr)

zrgubq pnrfne(vachg = Erkk, vqk = vag, pncf = obbyrna) choyvp fgngvp fvtanyf VyyrtnyNethzragRkprcgvba

vs vqk < 1 | vqk > 25 gura fvtany VyyrtnyNethzragRkprcgvba()

-- 12345678901234567890123456
vgno = 'NOPQRSTUVWXYZABCDEFGHIJKLM'
fuvsg = vgno.yratgu - vqk
cnefr vgno gy +(fuvsg) ge
bgno = ge || gy

vs pncf gura vachg = vachg.hccre

pvcure = vachg.genafyngr(vgno || vgno.ybjre, bgno || bgno.ybjre)

erghea pvcure

zrgubq pnrfne_rapvcure(vachg = Erkk, vqk = vag, pncf = obbyrna) choyvp fgngvp fvtanyf VyyrtnyNethzragRkprcgvba

erghea pnrfne(vachg, vqk, pncf)

zrgubq pnrfne_qrpvcure(vachg = Erkk, vqk = vag, pncf = obbyrna) choyvp fgngvp fvtanyf VyyrtnyNethzragRkprcgvba

erghea pnrfne(vachg, vag(26) - vqk, vfSnyfr)

zrgubq pnrfne_rapvcure(vachg = Erkk, vqk = vag) choyvp fgngvp fvtanyf VyyrtnyNethzragRkprcgvba

erghea pnrfne(vachg, vqk, vfSnyfr)

zrgubq pnrfne_qrpvcure(vachg = Erkk, vqk = vag) choyvp fgngvp fvtanyf VyyrtnyNethzragRkprcgvba

erghea pnrfne(vachg, vag(26) - vqk, vfSnyfr)

zrgubq pnrfne_rapvcure(vachg = Erkk, vqk = vag, bcg = Erkk) choyvp fgngvp fvtanyf VyyrtnyNethzragRkprcgvba

erghea pnrfne(vachg, vqk, bcg)

zrgubq pnrfne_qrpvcure(vachg = Erkk, vqk = vag, bcg = Erkk) choyvp fgngvp fvtanyf VyyrtnyNethzragRkprcgvba

erghea pnrfne(vachg, vag(26) - vqk, bcg)

zrgubq pnrfne(vachg = Erkk, vqk = vag, bcg = Erkk) choyvp fgngvp fvtanyf VyyrtnyNethzragRkprcgvba

vs bcg.hccre.nooeri('H') >= 1 gura pncf = vfGehr
ryfr pncf = vfSnyfr

erghea pnrfne(vachg, vqk, pncf)

zrgubq pnrfne(vachg = Erkk, vqk = vag) choyvp fgngvp fvtanyf VyyrtnyNethzragRkprcgvba

erghea pnrfne(vachg, vqk, vfSnyfr)

zrgubq vfGehr choyvp fgngvp ergheaf obbyrna
erghea (1 == 1)

zrgubq vfSnyfr choyvp fgngvp ergheaf obbyrna
erghea \vfGehr


=={{header|Objeck}}==

bundle Default {
class Rot13 {
function : Main(args : String[]) ~ Nil {
Rot13("nowhere ABJURER")->PrintLine();
}

function : native : Rot13(text : String) ~ String {
rot := "";
each(i : text) {
c := text->Get(i);
if(c >= 'a' & c <= 'm' | c >= 'A' & c <= 'M') {
rot->Append(c + 13);
}
else if(c >= 'n' & c <= 'z' | c >= 'N' & c <= 'Z') {
rot->Append(c - 13);
}
else {
rot->Append(c);
};
};

return rot;
}
}
}


=={{header|OCaml}}==

Straightforward implementation for characters by using character range patterns:

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


We provide a function for converting whole strings:

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

(* or in OCaml 4.00+:
let rot13_str = String.map rot13
*)


And here is a utility program that converts the content read on sdtin and write it to stdout:

let () =
try while true do
String.iter (fun c -> print_char (rot13 c)) (read_line());
print_newline()
done with End_of_file -> ()


=={{header|Oz}}==
declare
fun {RotChar C}
if C >= &A andthen C =< &Z then &A + (C - &A + 13) mod 26
elseif C >= &a andthen C =< &z then &a + (C - &a + 13) mod 26
else C
end
end

fun {Rot13 S}
{Map S RotChar}
end
in
{System.showInfo {Rot13 "NOWHERE Abjurer 42"}}
{System.showInfo {Rot13 {Rot13 "NOWHERE Abjurer 42"}}}


=={{header|PARI/GP}}==
rot13(s)={
s=Vecsmall(s);
for(i=1,#s,
if(s[i]>109&s[i]<123,s[i]-=13,if(s[i]<110&s[i]>96,s[i]+=13,if(s[i]>77&s[i]<91,s[i]-=13,if(s[i]<78&s[i]>64,s[i]+=13))))
);
Strchr(s)
};


=={{header|Pascal}}==
program rot13(input, output);

function rot13(someText: string): string;
var
i: integer;
ch: char;
resultText: string = '';

begin
for i := 1 to Length(someText) do begin
ch := someText[i];
case ch of
'A' .. 'M', 'a' .. 'm': ch := chr(ord(ch)+13);
'N' .. 'Z', 'n' .. 'z': ch := chr(ord(ch)-13)
end;
resultText := resultText + ch
end;
rot13 := resultText
end;

var
line: string;

begin
while not eof(input) do begin
readln(line);
writeln(rot13(line))
end
end.



=={{header|Perl}}==
sub rot13 {
my $string = shift;
$string =~ tr/A-Za-z/N-ZA-Mn-za-m/;
return $string;
}

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


Input:
NOWHERE Abjurer

Output:
ABJURER Nowhere

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

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

=={{header|Perl 6}}==
{{works with|Rakudo Star|2013.07}}

sub rot13 { $^s.trans: 'a..mn..z' => 'n..za..m', :ii }

multi MAIN () { print rot13 slurp }
multi MAIN (*@files) { print rot13 [~] map &slurp, @files }


This illustrates use of multi-dispatch to MAIN based on number of arguments.

=={{header|PHP}}==
PHP has a built-in function for this:
echo str_rot13('foo'), "\n";
will output
sbb

Here is an implementation:
function rot13($s) {
return strtr($s, 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz',
'NOPQRSTUVWXYZABCDEFGHIJKLMnopqrstuvwxyzabcdefghijklm');
}

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


Output:
sbb

=={{header|PicoLisp}}==
(de rot13-Ch (C)
(if
(or
(member C '`(apply circ (chop "ABCDEFGHIJKLMNOPQRSTUVWXYZ")))
(member C '`(apply circ (chop "abcdefghijklmnopqrstuvwxyz"))) )
(get @ 14)
C ) )

or:
(de rot13-Ch (C)
(cond
((>= "M" (uppc C) "A")
(char (+ (char C) 13)) )
((>= "Z" (uppc C) "N")
(char (- (char C) 13)) )
(T C) ) )

Then call it as:
(de rot13-stdIn ()
(while (line)
(prinl (mapcar rot13-Ch @)) ) )


=={{header|Pike}}==

import Crypto;

int main(){
string r = rot13("Hello, World");
write(r + "\n");
}


=={{header|PL/I}}==

rotate: procedure (in) options (main); /* 2 March 2011 */
declare in character (100) varying;
declare line character (500) varying;
declare input file;

open file (input) title ('/' || in || ',type(text),recsize(500)' );

on endfile (input) stop;

do forever;
get file (input) edit (line) (L);
line = translate (
line, 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz',
'NOPQRSTUVWXYZABCDEFGHIJKLMnopqrstuvwxyzabcdefghijklm');
put edit (line) (a); put skip;
end;
end;

Data file:

"The time has come,"
the walrus said,
"to speak of many things;
of ships and shoes and sealing wax;
of cabbages and kings."

Output:

"Gur gvzr unf pbzr,"
gur jnyehf fnvq,
"gb fcrnx bs znal guvatf;
bs fuvcf naq fubrf naq frnyvat jnk;
bs pnoontrf naq xvatf."


=={{header|PostScript}}==
{{libheader|initlib}}

/r13 {
4 dict begin
/rotc {
{
{{{64 gt} {91 lt}} all?} {65 - 13 + 26 mod 65 +} is?
{{{95 gt} {123 lt}} all?} {97 - 13 + 26 mod 97 +} is?
} cond
}.
{rotc} map cvstr
end}.


=={{header|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') =>


=={{header|PowerShell}}==


Function ROT13($String)
{
$Alphabet = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz"
$Cipher = "NOPQRSTUVWXYZABCDEFGHIJKLMnopqrstuvwxyzabcdefghijklm"
Foreach($Char in $String.ToCharArray())
{
If ( $Char -match "[A-Za-z]" )
{ $NewString += $Cipher.Chars($Alphabet.IndexOf($Char)) }
else
{ $NewString += $Char }
}
Return $NewString
}


=={{header|Prolog}}==
Works with SWI-Prolog.
rot13(Str, SR) :-
maplist(rot, Str, Str1),
string_to_list(SR, Str1).

rot(C, C1) :-
( member(C, "abcdefghijklmABCDEFGHIJKLM") -> C1 is C+13;
( member(C, "nopqrstuvwxyzNOPQRSTUVWXYZ") -> C1 is C-13; C1 = C)).

Output :
?- rot13("The Quick Brown Fox Jumped Over The Lazy Dog!", SR).
SR = "Gur Dhvpx Oebja Sbk Whzcrq Bire Gur Ynml Qbt!".


=={{header|PureBasic}}==
Declare.s Rot13(text_to_code.s)

If OpenConsole()
Define txt$

Print("Enter a string to encode: "): txt$=Input()

PrintN("Coded : "+Rot13(txt$))
PrintN("Decoded: "+Rot13(Rot13(txt$)))

Print("Press ENTER to quit."): Input()
CloseConsole()
EndIf

Procedure.s Rot13(s.s)
Protected.i i
Protected.s t, u
For i=1 To Len(s)
t=Mid(s,i,1)
Select Asc(t)
Case Asc("a") To Asc("m"), Asc("A") To Asc("M")
t=chr(Asc(t)+13)
Case Asc("n") To Asc("z"), Asc("N") To Asc("Z")
t=chr(Asc(t)-13)
EndSelect
u+t
Next
ProcedureReturn u
EndProcedure


=={{header|Python}}==
Python 2.x (but not 3.x) has built-in rot13 encoding and decoding:
{{works with|Python|2.x}}

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


Here is an implementation:

{{works with|Python|2.x}}
#!/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)!


The ''str.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}}
In Python 3.x, the ''string.maketrans()'' function actually only works for the ''bytes'' type, and has been deprecated since 3.1. If you want to work on strings (''str'' type), you need to use ''str.maketrans()'':
#!/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="")


=={{header|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"

For a slightly more general function, see the [http://stat.ethz.ch/R-manual/R-patched/library/base/html/chartr.html example on the chartr help page].

=={{header|Racket}}==

#!/bin/env racket
#lang racket/base

(define (run i o)
(for ([ch (in-producer regexp-match #f #rx#"[a-zA-Z]" i 0 #f o)])
(define b (bytes-ref (car ch) 0))
(define a (if (< b 96) 65 97))
(write-byte (+ (modulo (+ 13 (- b a)) 26) a))))

(require racket/cmdline)
(command-line
#:help-labels "(\"-\" specifies standard input)"
#:args files
(for ([f (if (null? files) '("-") files)])
(if (equal? f "-")
(run (current-input-port) (current-output-port))
(call-with-input-file f (λ(i) (run i (current-output-port)))))))


=={{header|Raven}}==
define rot13 use $str
$str each chr
dup m/[A-Ma-m]/ if
ord 13 + chr
else
dup m/[N-Zn-z]/ if
ord 13 - chr
$str length list "" join

"12!ABJURER nowhere"
dup print "\nas rot13 is\n" print
rot13
print "\n" print

{{out}}
12!ABJURER nowhere
as rot13 is
12!NOWHERE abjurer


=={{header|REBOL}}==
REBOL [
Title: "Rot-13"
Date: 2009-12-14
Author: oofoe
URL: http://rosettacode.org/wiki/Rot-13
]

; Test data has upper and lower case characters as well as characters
; that should not be transformed, like numbers, spaces and symbols.

text: "This is a 28-character test!"

print "Using cipher table:"

; I build a set of correspondence lists here. 'x' is the letters from
; A-Z, in both upper and lowercase form. Note that REBOL can iterate
; directly over the alphabetic character sequence in the for loop. 'y'
; is the cipher form, 'x' rotated by 26 characters (remember, I have
; the lower and uppercase forms together). 'r' holds the final result,
; built as I iterate across the 'text' string. I search for the
; current character in the plaintext list ('x'), if I find it, I get
; the corresponding character from the ciphertext list
; ('y'). Otherwise, I pass the character through untransformed, then
; return the final string.

rot-13: func [
"Encrypt or decrypt rot-13 with tables."
text [string!] "Text to en/decrypt."
/local x y r i c
] [
x: copy "" for i #"a" #"z" 1 [append x rejoin [i uppercase i]]
y: rejoin [copy skip x 26 copy/part x 26]
r: copy ""

repeat i text [append r either c: find/case x i [y/(index? c)][i]]
r
]

; Note that I am setting the 'text' variable to the result of rot-13
; so I can reuse it again on the next call. The rot-13 algorithm is
; reversible, so I can just run it again without modification to decrypt.

print [" Encrypted:" text: rot-13 text]
print [" Decrypted:" text: rot-13 text]


print "Using parse:"

clamp: func [
"Contain a value within two enclosing values. Wraps if necessary."
x v y
][
x: to-integer x v: to-integer v y: to-integer y
case [v < x [y - v] v > y [v - y + x - 1] true v]
]

; I'm using REBOL's 'parse' word here. I set up character sets for
; upper and lower-case letters, then let parse walk across the
; text. It looks for matches to upper-case letters, then lower-case,
; then skips to the next one if it can't find either. If a matching
; character is found, it's mathematically incremented by 13 and
; clamped to the appropriate character range. parse changes the
; character in place in the string, hence this is a destructive
; operation.

rot-13: func [
"Encrypt or decrypt rot-13 with parse."
text [string!] "Text to en/decrypt. Note: Destructive!"
] [
u: charset [#"A" - #"Z"]
l: charset [#"a" - #"z"]

parse text [some [
i: ; Current position.
u (i/1: to-char clamp #"A" i/1 + 13 #"Z") | ; Upper case.
l (i/1: to-char clamp #"a" i/1 + 13 #"z") | ; Lower case.
skip]] ; Ignore others.
text
]

; As you see, I don't need to re-assign 'text' anymore.

print [" Encrypted:" rot-13 text]
print [" Decrypted:" rot-13 text]


Output:

Using cipher table:
Encrypted: Guvf vf n 28-punenpgre grfg!
Decrypted: This is a 28-character test!
Using parse:
Encrypted: Guvf vf n 28-punenpgre grfg!
Decrypted: This is a 28-character test!


=={{header|Retro}}==
{{
: rotate ( cb-c ) tuck - 13 + 26 mod + ;
: rotate? ( c-c )
dup 'a 'z within [ 'a rotate ] ifTrue
dup 'A 'Z within [ 'A rotate ] ifTrue ;
---reveal---
: rot13 ( s-s ) dup [ [ @ rotate? ] sip ! ] ^types'STRING each@ ;
}}

"abcdef123GHIJKL" rot13 dup puts cr rot13 puts
"abjurer NOWHERE" rot13 puts


=={{header|REXX}}==
/*REXX program to encode several text strings with ROT 13 algorithm. */
aa = 'foo'
say 'simple text = 'aa
say ' rot13 text = 'rot13(aa)
say

bb = 'bar'
say 'simple text = 'bb
say ' rot13 text = 'rot13(bb)
say

cc = "Noyr jnf V, 'rer V fnj Ryon."
say 'simple text = 'cc
say ' rot13 text = 'rot13(cc)
say

dd = 'abc? ABC!'
say 'simple text = 'dd
say ' rot13 text = 'rot13(dd)
say

ee = 'abjurer NOWHERE'
say 'simple text = 'ee
say ' rot13 text = 'rot13(ee)
exit /*stick a fork in it, we're done.*/

/*──────────────────────────────────ROT13 subroutine────────────────────*/
rot13: return translate(arg(1),,
'abcdefghijklmABCDEFGHIJKLMnopqrstuvwxyzNOPQRSTUVWXYZ',,
'nopqrstuvwxyzNOPQRSTUVWXYZabcdefghijklmABCDEFGHIJKLM')

'''output'''

simple text = foo
rot13 text = sbb

simple text = bar
rot13 text = one

simple text = Noyr jnf V, 'rer V fnj Ryon.
rot13 text = Able was I, 'ere I saw Elba.

simple text = abc? ABC!
rot13 text = nop? NOP!

simple text = abjurer NOWHERE
rot13 text = nowhere ABJURER


=={{header|Ruby}}==
# Returns a copy of _s_ with rot13 encoding.
def rot13(s)
s.tr('A-Za-z', 'N-ZA-Mn-za-m')
end

# Perform rot13 on files from command line, or standard input.
while line = ARGF.gets
print rot13(line)
end


One can run ruby rot13.rb file1 file2 to rot13 those files, or run ruby rot13.rb to rot13 the standard input.

Input:
ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz

Output:
NOPQRSTUVWXYZABCDEFGHIJKLMnopqrstuvwxyzabcdefghijklm

=={{header|Run BASIC}}==
INPUT "Enter a string: "; s$
ans$ = ""
FOR a = 1 TO LEN(s$)
letter$ = MID$(s$, a, 1)
IF letter$ >= "A" AND letter$ <= "Z" THEN
char$ = CHR$(ASC(letter$) + 13)
IF char$ > "Z" THEN char$ = CHR$(ASC(char$) - 26)
else
if 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$
Output:
Enter a string: ?abc
nop
Enter a string: ?ABC
NOP


=={{header|Scala}}==
scala> def rot13(s: String) = s map {
| case c if 'a' <= c.toLower && c.toLower <= 'm' => c + 13 toChar
| case c if 'n' <= c.toLower && c.toLower <= 'z' => c - 13 toChar
| case c => c
| }
rot13: (s: String)String

scala> rot13("7 Cities of Gold.")
res61: String = 7 Pvgvrf bs Tbyq.

scala> rot13(res61)
res62: String = 7 Cities of Gold.


=={{header|Scheme}}==
(define (rot13 str)
(define (rot13-char c)
(integer->char (+ (char->integer c)
(cond ((and (char>=? c #\a) (char 13)
((and (char>=? c #\A) (char 13)
((and (char>=? c #\n) (char<=? c #\z))
-13)
((and (char>=? c #\N) (char<=? c #\Z))
-13)
(else
0)))))
(list->string (map rot13-char (string->list str))))


=={{header|sed}}==
The two translations (upper and lower case) are separate only for documentation and ease of understanding; they could be combined into one command.
y/abcdefghijklmnopqrstuvwxyz/nopqrstuvwxyzabcdefghijklm/
y/ABCDEFGHIJKLMNOPQRSTUVWXYZ/NOPQRSTUVWXYZABCDEFGHIJKLM/


=={{header|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;

=={{header|Slate}}==
A shell script:

#!/usr/local/bin/slate

ch@(String Character traits) rot13
[| value |
upper ::= ch isUppercase.
value := ch toLowercase as: Integer.
(value >= 97) /\ [value < 110]
ifTrue: [value += 13]
ifFalse: [(value > 109) /\ [value <= 122]
ifTrue: [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.


Normal functions:

ch@(String Character traits) rot13
[| value |
upper ::= ch isUppercase.
value := ch toLowercase as: Integer.
(value >= 97) /\ [value < 110]
ifTrue: [value += 13]
ifFalse: [(value > 109) /\ [value <= 122]
ifTrue: [value -= 13]].
upper
ifTrue: [(value as: String Character) toUppercase]
ifFalse: [value as: String Character]
].

s@(String traits) rot13
[
result ::= s newSameSize.
s doWithIndex: [| :each :index | result at: index put: each rot13].
result
].

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


=={{header|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.

"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.


=={{header|SNOBOL4}}==

{{works with|Macro Spitbol}}
{{works with|Snobol4+}}
{{works with|CSnobol}}

* # Function using replace( )
define('rot13(s)u1,u2,l1,l2') :(rot13_end)
rot13 &ucase len(13) . u1 rem . u2
&lcase len(13) . l1 rem . l2
rot13 = replace(s,&ucase &lcase,u2 u1 l2 l1) :(return)
rot13_end

* # Function using pattern
define('rot13s(s)c')
alfa = &ucase &ucase &lcase &lcase :(rot13s_end)
rot13s s len(1) . c = :f(return)
alfa break(c) len(13) len(1) . c
rot13s = rot13s c :(rot13s)
rot13s_end

* # Test and display both
str = rot13("I abjure the $19.99 trinket!")
output = str; output = rot13(str)
str = rot13s("He's a real Nowhere Man.")
output = str; output = rot13s(str)
end


Output:
V nowher gur $19.99 gevaxrg!
I abjure the $19.99 trinket!
Ur'f n erny Abjurer Zna.
He's a real Nowhere Man.


=={{header|Standard ML}}==
fun rot13char c =
if c >= #"a" andalso c <= #"m" orelse c >= #"A" andalso c <= #"M" then
chr (ord c + 13)
else if c >= #"n" andalso c <= #"z" orelse c >= #"N" andalso c <= #"Z" then
chr (ord c - 13)
else
c

val rot13 = String.map rot13char


=={{header|SQL}}==
{{works with|T-SQL}}

with cte(num) as
(
select 1
union all
select num+1
from cte
)
select cast((
select char(ascii(chr) +
case
when ascii(chr) between ascii('a') and ascii('m') or
ascii(chr) between ascii('A') and ascii('M') then 13
when ascii(chr) between ascii('n') and ascii('z') or
ascii(chr) between ascii('N') and ascii('Z') then -13
else 0
end)
from
(
select top(1000) num,
-- your string to be converted to ROT13
substring('The Quick Brown Fox Jumps Over The Lazy Dog',num,1) chr
from cte
) tmp
For XML PATH ('')) as xml).value('.', 'VARCHAR(max)') rot13
option (maxrecursion 0)


=={{header|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
}


Using {{libheader|TclX}} we can write
package require Tclx
proc rot13 str {
translit "A-Za-z" "N-ZA-Mn-za-m" $str
}


=={{header|TorqueScript}}==
--[[User:Ipquarx|Ipquarx]] 8:45 PM
function rot13(%string)
{
%alph = "abcdefghijklmnopqrstuvwxyz";
%len = strLen(%string);

for(%a = 0; %a < %len; %a++)
{
%char = getSubStr(%string,%a,1);
%pos = striPos(%alph, %char);

if(%pos < 0)
%out = %out @ %char;
else
{
if(strPos(%alph, %char) < 0)
%out = %out @ strUpr(getSubStr(%alph, (%pos + 13) % 26));
else
%out = %out @ getSubStr(%alph, (%pos + 13) % 26);
}
}
return %out;
}


=={{header|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


=={{header|TXR}}==

Via definition and subsequent use of a named filter.

@(deffilter rot13
("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"))
@(collect :vars ())
@line
@ (output :filter rot13)
@line
@ (end)
@(end)


The :vars () argument to collect means that it still iterates, but doesn't actually collect anything (empty list of variables). This is important, so that there isn't a growing data structure being accumulated as the input is processed.

=={{header|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]'
}

cat ${1+"$@"} | rot13


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. A simple tr a-zA-Z n-za-mN-ZA-M would work with modern systems that follow [[POSIX]]. Our tr '[a-m][n-z][A-M][N-Z]' '[n-z][a-m][N-Z][A-M]' also works with those older System V systems. For newer systems, it translates '[' and ']' to themselves. (Refer to [http://www.openbsd.org/cgi-bin/man.cgi?query=tr&apropos=0&sektion=1&manpath=OpenBSD+Current&arch=i386&format=html#STANDARDS OpenBSD tr(1) manual page, section STANDARDS].)

This example shows proper quoting around "$@" (magical argument list) such that this script work properly even if some of the files named on the command line contain embedded spaces or other such characters. (The ${1+"$@"} check, unnecessary in modern systems, allows the script to work even on older systems where a bare "$@" expanded to a single empty string when no arguments were supplied).

=={{header|Unlambda}}==
``ci`d``@i`c``s`d```?aic.n``s`d```?bic.o``s`d```?cic.p``s`d```?dic.q``s`d```?eic
.r``s`d```?fic.s``s`d```?gic.t``s`d```?hic.u``s`d```?iic.v``s`d```?jic.w``s`d```
?kic.x``s`d```?lic.y``s`d```?mic.z``s`d```?nic.a``s`d```?oic.b``s`d```?pic.c``s`
d```?qic.d``s`d```?ric.e``s`d```?sic.f``s`d```?tic.g``s`d```?uic.h``s`d```?vic.i
``s`d```?wic.j``s`d```?xic.k``s`d```?yic.l``s`d```?zic.m``s`d```?Nic.A``s`d```?O
ic.B``s`d```?Pic.C``s`d```?Qic.D``s`d```?Ric.E``s`d```?Sic.F``s`d```?Tic.G``s`d`
``?Uic.H``s`d```?Vic.I``s`d```?Wic.J``s`d```?Xic.K``s`d```?Yic.L``s`d```?Zic.M``
s`d```?Aic.N``s`d```?Bic.O``s`d```?Cic.P``s`d```?Dic.Q``s`d```?Eic.R``s`d```?Fic
.S``s`d```?Gic.T``s`d```?Hic.U``s`d```?Iic.V``s`d```?Jic.W``s`d```?Kic.X``s`d```
?Lic.Y``s`d```?Mic.Z`d`|c


=={{header|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.
#import std

#executable (<'parameterized','default-to-stdin'>,<>)

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


=={{header|Vedit macro language}}==
Using ROT13.TBL from [http://cu2.home.comcast.net/~cu2/vedit/ here]
Translate_Load("ROT13.TBL")
Translate_Block(0, File_Size)


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.

=={{header|Visual Basic .NET}}==
'''Platform:''' [[.NET]]

{{works with|Visual Basic .NET|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.

=={{header|Wart}}==
def (rot13 s)
(as string
(map rot13
(as list s)))

Alphabet <- "abcdefghijklmnopqrstuvwxyz"
def (rot13 c) :case (and string?.c len.c=1)
if ("a" <= c <= "z")
let idx (pos c Alphabet)
Alphabet (idx+13 % 26)
("A" <= c <= "Z")
(downcase.c -> rot13 -> upcase)
:else
c


Output:
(rot13 "Moron")
=> "Zbeba"


=={{header|X86 Assembly}}==
Using Linux/FASM.
format ELF executable 3
entry start

segment readable writeable
buf rb 1

segment readable executable
start: mov eax, 3 ; syscall "read"
mov ebx, 0 ; stdin
mov ecx, buf ; buffer for read byte
mov edx, 1 ; len (read one byte)
int 80h

cmp eax, 0 ; EOF?
jz exit

xor eax, eax ; load read char to eax
mov al, [buf]
cmp eax, "A" ; see if it is in ascii a-z or A-Z
jl print
cmp eax, "z"
jg print
cmp eax, "Z"
jle rotup
cmp eax, "a"
jge rotlow
jmp print

rotup: sub eax, "A"-13 ; do rot 13 for A-Z
cdq
mov ebx, 26
div ebx
add edx, "A"
jmp rotend

rotlow: sub eax, "a"-13 ; do rot 13 for a-z
cdq
mov ebx, 26
div ebx
add edx, "a"

rotend: mov [buf], dl

print: mov eax, 4 ; syscall write
mov ebx, 1 ; stdout
mov ecx, buf ; *char
mov edx, 1 ; string length
int 80h

jmp start

exit: mov eax,1 ; syscall exit
xor ebx,ebx ; exit code
int 80h


=={{header|XPL0}}==
Usage: rot13 outfile.txt
code ChIn=7, ChOut=8;
int C, CC;
repeat C:= ChIn(1); CC:= C&~$20; \CC handles lowercase too
ChOut(0, C + (if CC>=^A & CC<=^M then +13
else if CC>=^N & CC<=^Z then -13
else 0));
until C = $1A; \EOF


=={{header|XSLT}}==
Textual transforms are one of the domains XSLT was designed for.


ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz
NOPQRSTUVWXYZABCDEFGHIJKLMnopqrstuvwxyzabcdefghijklm







This will transform the input:
The Abjurer was to be found Nowhere.
into:
The Nowhere was to be found Abjurer.

=={{header|ZX Spectrum Basic}}==
{{trans|QBasic}}

10 CLS
20 INPUT "Enter a string: ", s$
30 LET a$ = "": REM a$ is the encoded string
40 FOR l = 1 TO LEN(s$)
50 LET i$ = s$(l): REM i$ is the letter being worked on
60 IF i$ < "A" OR i$ > "Z" THEN GO TO 100
70 LET c$ = CHR$(CODE(i$) + 13): REM c$ is the encoded letter
80 IF c$ > "Z" THEN LET c$ = CHR$(CODE(c$) - 26)
90 GO TO 300
100 IF i$ < "a" OR i$ > "z" THEN GO TO 200
110 LET c$ = CHR$(CODE(i$) + 13)
120 IF c$ > "z" THEN LET c$ = CHR$(CODE(c$) - 26)
130 GO TO 300
200 LET c$ = i$
300 LET a$ = a$ + c$
310 NEXT l
320 PRINT a$