From: Robert Klemme <shortcutter@...>
Date: 2010-10-26T15:30:29+09:00
Subject: Re: Extraction of single subarrays from multidimensional array

On 26.10.2010 01:01, Maurizio Cirilli wrote:

>       I am a new member of this group and a newbie about Ruby. After a
> not successful and
> extensive search on this topic, I ask your help solving a problem in
> picking out single subarrays
> from a multidimesional array.
> In short, I somehow stored the following m-array (single strings are
> DNA codons):
> ss = ["tcg", "agt", "tct", "agc", "tca", "tcc"], ["aaa", "aag"],
> ["ctg", "tta", "ctt", "cta", "ctc", "ttg"]]

Btw, I assume you do bioinformatics.  If all your Arrays contain three 
letter sequences you should probably change entries to Symbols (there 
are only 4 ^ 3 = 64 of them).

I'd probably replace these Arrays by a custom class for handling 
sequences and work with that.  Then you can optimize internal 
representation (e.g. use a Fixnum to code a three letter sequence) to 
save even more memory.  I believe there are libraries for bioinformatics 
out there which probably do exactly that.

> What I would like to get are the separated arrays s[0],  s[1] and s[2]
> by iteration over array ss.
> The method array.clone looks perfect for this aim:
>
> irb(main):039:0>  v0 = ss[0].clone
> =>  ["tcg", "agt", "tct", "agc", "tca", "tcc"]
>
> but I did not find the right way to iterate this method over the m-
> array and get indexed subarrays.

Do you actually need a copy or do you want to reference the original? 
If you need the original here's the simplest approach

a, b, c = *ss

For copy you can do (in 1.9.*)

a, b, c = *ss.map &:clone # 1.9.*
a, b, c = *ss.map {|x| x.clone} # 1.8.6 and earlier

Note that then you still share String instances!  So if you want to 
manipulate individual strings you need to take a different approach (e.g.)

a, b, c = *ss.map {|arr| arr.map {|s| s.dup}}
a, b, c = *Marshal.load(Marshal.dump(ss))

> I tried  iterations like:
>
>   v"#{n}"= ss.clone(n) do |n|
> end
> or

Apart from that it does not work, where's the point in creating 
variables with calculated names with indexes if you can do indexed 
access via the Array already?   That does not seem like a viable approach.

Kind regards

	robert

-- 
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