Smoking hash-ish: Letter mapping

Ruby
#1

Hi,

for a very simplistic encryption program I want to build a
hash, which should be dynamically build (not hardcoded).

The input of the method which should do the job will be a range of
any meaningful input, say: parameter 1: A and parameter 2: Z

Then the method should create a Hash with that mapping
“A” -> “Z”
“B” -> “G”
“C” -> “T”
…

or in other words:
The key should follow the given range, and the values should
represent all values of that range but in random order.

For arrays I learned a nice trick from this list:

 encmap=(A..Z).to_a.sort{rand(2)}

but…how can I accomplish similiar for a hash ???

And: I sthere a simple way to store a hash in binary format and later
load that hash again into memory ?

Nice weekend!
mcc

#2

Maybe: encmap=Hash[*(‘A’…‘Z’).to_a.sort{rand(2)}]

and Marshal.dump and Marshal.load for storing.

j`ey
http://www.eachmapinject.com

#3

From: Joey [email protected]
Subject: Re: Smoking hash-ish: Letter mapping…
Date: Sun, 6 Aug 2006 03:55:14 +0900

Looks good! May be I am too newbie here, but…
When I do this in irb and look at encmap, both - key and value -
seem to be randomnized…

(and what means the “*” right at the start of the expression?)

But this is not really an issue as long there is no identical mapping
like “A”->“A”.

Ah, by the way: With an even number of items/mapping in such an
Hash…there must be zero or an even number of identical mappings like
described above. Is this logical correct or nonsense…?

#4

On Aug 5, 2006, at 3:07 PM, Meino Christian C. wrote:

Oh…there is another issue:

With encmap=Hash[*(‘A’…‘Z’).to_a.sort{rand(2)}] I only will get 13
instead of 26 mappings! How can I fix /that/ ?

Keep encoding! :slight_smile:
mcc

Actually its generally considered better to do sort_by{rand} that sort
{rand(2)}

If you only want to randomize key or value you can do

first = (“A”…“Z”).to_a
second = (“A”…“Z”).sort_by{rand}

encmap = Hash[ *first.zip(second).flatten ]

#5

Oh…there is another issue:

With encmap=Hash[*(‘A’…‘Z’).to_a.sort{rand(2)}] I only will get 13
instead of 26 mappings! How can I fix /that/ ?

Keep encoding! :slight_smile:
mcc