Merging arrays without losing original order, ruby

Question

I have an array structure that looks like:

a=[
  [['a','A'],['b','B'],['c','C']],
  [['d','D'],['e','E'],['f','F']]
]

How to merge inner two arrays so the new structure will be Array of arrays

[
 ['a','A'],['b','B'],['c','C'],['d','D'],['e','E'],['f','F']
]

Tried

a.inject([]){|k,v| v | k} # but order gets changed
=> [["d", "D"], ["e", "E"], ["f", "F"], ["a", "A"], ["b", "B"], ["c", "C"]]

How can i get desired result without loosing the order.

Tips, comments, suggestions, please?

Thnx.

Do you want to *set-wise union* the inner arrays or *concatenate* them? What would you want to happen to `[ [['a','A']], [['a','A']] ]`? — mu is too short, Apr 19 '12 at 17:44
i wanted set wise union. i did a silly by putting v|k instead of k|v — hitesh israni, Apr 19 '12 at 17:51

score 5 · Answer 1 · answered Apr 19 '12 at 08:51

5

array.flatten takes a parameter:

a.flatten(1) #[["a", "A"], ["b", "B"], ["c", "C"], ["d", "D"], ["e", "E"], ["f", "F"]]

answered Apr 19 '12 at 08:51

steenslag

wow! thats nice solution. i have been trying flatten without parameter, which was giving ["a", "A", "b", "B", "c", "C", "d", "D", "e", "E", "f", "F"] can you please explain the need for parameter here. thnx – hitesh israni Apr 19 '12 at 08:57
1

The parameter specifies how much levels you want to flatten. The default is 'all'; in this case just 1 level is sufficient. – steenslag Apr 19 '12 at 09:00

score 1 · Accepted Answer · answered Apr 19 '12 at 08:45

1

Try this:

a.inject([]){|k,v| k|v}

answered Apr 19 '12 at 08:45

Ivaylo Strandjev

3

Or, shorter, `a.inject(&:|)` (lol, a confused smiley with a funny hat!) – Mladen Jablanović Apr 19 '12 at 08:47
yes. i just tried this, before getting your answer. my bad. this was a silly question. – hitesh israni Apr 19 '12 at 08:48
@MladenJablanović, can you please explain(in brief) how this a.inject(&:|) works. I know that, you use '&' as short for each element. – hitesh israni Apr 19 '12 at 08:54
Very similar question here: http://stackoverflow.com/questions/5003257/how-does-1-4-inject-work-in-ruby with lots of links in there as well. – Mladen Jablanović Apr 19 '12 at 08:58
@MladenJablanović- a.inject(:|) will also be fine. no need for & in this case. cheers... – hitesh israni Apr 19 '12 at 10:27

2 Answers2