From: Robert Klemme <shortcutter@...>
Date: 2008-01-25T23:37:06+09:00
Subject: Re: Changing an array data structure

2008/1/24, Michael Schmarck <michael.schmarck@here.la>:
> Hello.
>
> I already asked about how I'd best re-order a datastructure. But
> thinking about, I changed my mind; instead of the hash approach
> I've shown in <news:6233013.YDsyxgeUJ1@michael-schmarck.my-fqdn.de>,
> I now think I might use arrays instead. Reason: The order in which
> something is inserted and later fetched is important to me. With
> Hashes in 1.8, this cannot easily be done out-of-the-box, can it?
>
> Anyway - I'm now looking for a way to change the following arry:

This is not an Array but an object graph composed of nested Arrays.

> timing = [
>       ["Performance Test of Item Access using Lists", [
>           [["Plants", 100], ["Customers", 50], ["Total", 150]],
>           [["Plants",  85], ["Customers", 60], ["Total", 145]],
>           [["Plants", 111], ["Customers", 77], ["Total", 188]]
>       ]],
>       ["Performance Test of Item Access using Advance Item Search", [
>           [["Work List", 17], ["Bookmarks", 30], ["Total", 42]],
>           [["Work List", 10], ["Bookmarks", 33], ["Total", 50]],
>           [["Work List", 22], ["Bookmarks", 27], ["Total", 99]]
>       ]]
> ]
> # This should become:
> timing_reordered = [
>      ["Performance Test of Item Access using Lists", [
>          ["Plants", [100, 85, 111]], ["Customers", [50, 60, 77]], ["Total", [150, 145, 188]]
>      ]],
>      ["Performance Test of Item Access using Advance Item Search", [
>          ["Work List", [17, 10, 22]], ["Bookmarks", [30, 33, 27]], ["Total", [42, 50, 99]]
>      ]]
> ]

My first advice would be to use proper data types, e.g.

S1 = Struct.new :plants, :customers, :total
S2 = Struct.new :work_list, :bookmarks, :total

etc.

> It very much resembles the datastructure shown in the hash approach.
> That's only natural, if you take into consideration how the data is
> generated. To do that, I'm running a method 3 (or more) times; these
> methods generate the "Performance Test of Item Access using Lists"
> and "Performance Test of Item Access using Advance Item Search" data.

For these you should use those structs (see above).

> These methods generate data; data items for Plants, Customers and
> so on.
>
> But for reporting, it's best for me, if all the eg. Plants results
> are "grouped together". Actually, I only need the innermost arrays,
> ie. [100, 85, 111], [50, 60, 77], .... These arrays should be
> concated, so that I've only got one long array, starting with: [100,
> 85, 111, 50, 60, 77, ...].

With the structs above

# data contains S1
data.inject(S1.new) do |s,d|
  (s.plants ||= []) << d.plants
  (s.customers ||= []) << d.customers
  (s.total ||= []) << d.total
  s
end

Alternatively

data.inject(:plants=>[], :customers=>[], :total=>[]) do |s,d|
  d.members.each {|m| s[m.to_sym] = d[m]}
  s
end

Of course you need to take additional measures to cope with the
nesting (S1 and S2).

Cheers

robert

-- 
use.inject do |as, often| as.you_can - without end