From: Gianfranco Bozzetti <gf.bozzetti@...>
Date: 2010-08-21T00:31:56+09:00
Subject: Re: Need help with hash.to_s for enumerated items

Sem Ptiri wrote:
> I have a grid with keys
> 
> grid.keys
> => [[1, 2], [0, 0], [3, 3], [2, 1], [1, 1], [0, 3], [3, 2], [2, 0], [1,
> 0], [0, 2], [3, 1], [2, 3], [4, 3], [3, 0], [2, 2], [1, 3], [0, 1], [6,
> 3]]
> 
> I need to create a list list of all possible combinations. I would start
> by taking the first item, then linking it with every other item, then
> truncate the first item, and repeat.
> 
> My problem is that on
> 
> grid.keys[0].to_s
> => "12"
> 
> it mashes the [1, 2] together making it unusable.

On my system array#to_s joins the arrays' elements ("12")
arrai#inspect prints the array [1, 2]

> Could you suggest a better data structure for storing a list of all
> possible combinations?
> 
> Linking a hash [1, 2] to [0, 0] and then [1, 1] would simply override
> the previous link.

If I understand correctly the problem, you can:
 1 - assign the keys to an array varable, say gk=grid.keys
 2 - create a list of indexes for each possible pair in gk
 3 - access gk via indexes
as in:
<code
# grid_keys.rb
gk = [ [1, 2], [0, 0], [3, 3] ]
gk.each_index { |i| puts "#{i} : #{gk[i].inspect}" }
# create a list of indexes in gk
pairs = []
(0...gk.size-1).each do |index1|
  (index1+1...gk.size).each  do |index2|
     pairs << [index1, index2]
  end
end
puts "Pairs of indexes"
pairs.each { |a| puts a.inspect }

puts "Indexes     Grid_Pairs"
pairs.each do |idx|
 puts "#{idx.inspect}  :  #{gk[idx[0]].inspect} - #{gk[idx[1]].inspect}"
 end
exit(0)
__END__
Result:
ruby grid_keys.rb
0 : [1, 2]
1 : [0, 0]
2 : [3, 3]
Pairs of indexes
[0, 1]
[0, 2]
[1, 2]
Indexes     Grid_Pairs
[0, 1]  :  [1, 2] - [0, 0]
[0, 2]  :  [1, 2] - [3, 3]
[1, 2]  :  [0, 0] - [3, 3]
<code/>

HTH gfb
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