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From: jpm@calmasd.UUCP (John McNally)
Newsgroups: net.jokes
Subject: HOW TO ROTATE/UNROTATE TEXT
Message-ID: <407@calmasd.UUCP>
Date: Fri, 24-May-85 16:45:34 EDT
Article-I.D.: calmasd.407
Posted: Fri May 24 16:45:34 1985
Date-Received: Wed, 29-May-85 23:36:57 EDT
Organization: Calma Company, San Diego, CA
Lines: 34

Sorry to put this is net.jokes.  It really belongs in net.jokes.d,
but the requestor of this information posted it to net.jokes, so I
assumed they wouldn't see this elsewhere.

Someone requested how to handle rot13 out of the context of
readnews.  I don't remember the actual article or requestor.
Someone else posted this about six months ago (I don't remember
the poster.  What a memory!):

tr A-Za-z N-ZA-Mn-za-m

This uses the UNIX translate command.  I alias this to a command
called rot, which then takes standard in and standard out:

rot < rotated.text > unrotated.text

The nifty thing about rot13 is that it is idempotent (I think this
is the correct term).  That is:

f(x) = y, f(y) = x

So, with rot you can also:

rot < unrotated.text > rotated.text

If you think about it awhile you will see that this is obviously
true, because rot13 just shifts every letter 13 letters forward in
the alphabet (in a circular fashion). Two rotations produce a 26
letter shift, which is an identity operation.

For further reading, see the manual page for tr.
-- 
John McNally  Calma  11080 Roselle St. San Diego CA 92121
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