Need help with hash.to_s for enumerated items

Ruby
1

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.

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.

2

Would it be a better option to create a custom class for linking?

3

2010/8/20 Sem P. [email protected]:

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.

Combinations of what? Combinations of all Arrays that are your keys
or of all elements in those arrays or…?

I would start
by taking the first item, then linking it with every other item, then
truncate the first item, and repeat.

“Truncate”?

My problem is that on

grid.keys[0].to_s
=> “12”

it mashes the [1, 2] together making it unusable.

I have no idea what Array#to_s has to do in combining elements.

Could you suggest a better data structure for storing a list of all
possible combinations?

Why not use an Array of Arrays?

Linking a hash [1, 2] to [0, 0] and then [1, 1] would simply override
the previous link.

What exactly do you mean by “linking”? Are you talking about
replacing a hash key? Or are you talking about using a Hash key as
value of another key?

As soon as you set another value for the same Hash key the old value is
gone:

irb(main):003:0> h={}
=> {}
irb(main):004:0> h[[1,2]]=[0,0]
=> [0, 0]
irb(main):005:0> h
=> {[1, 2]=>[0, 0]}
irb(main):006:0> h[[1,2]]=[1,1]
=> [1, 1]
irb(main):007:0> h
=> {[1, 2]=>[1, 1]}

Kind regards

robert

4

Sem P. 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]

HTH gfb