32 lines
2.0 KiB
Plaintext
32 lines
2.0 KiB
Plaintext
;Task:
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Implement a '''rot-13''' function (or procedure, class, subroutine, or other "callable" object as appropriate to your programming environment).
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Optionally wrap this function in a utility program (like [[:Category:Tr|tr]], 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."
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(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]]).
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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.
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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.
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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).
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Thus the letters '''abc''' become '''nop''' and so on.
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Technically '''rot-13''' is a "mono-alphabetic substitution cipher" with a trivial "key".
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A proper implementation should work on upper and lower case letters, preserve case, and pass all non-alphabetic characters
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in the input stream through without alteration.
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;Related tasks:
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* [[Caesar cipher]]
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* [[Substitution Cipher]]
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* [[Vigenère Cipher/Cryptanalysis]]
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{{Template:Strings}}
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<br><br>
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