Ruby: Pair individual values of two arrays into third array

Question

I have two arrays: ['x','y','z'] and [1,2]. How would I go about creating pairs of values (as a string) in a third array?

So I would end up with this:

['x:1', 'x:2', 'y:1', 'y:2', 'z:1', 'z:2']

Thanks for any help!

Phil Ross · Accepted Answer · 2014-08-22 15:39:47Z

11

You can use the product method to create the pairs and then join them:

a1 = ['x','y','z']
a2 = [1,2]
a1.product(a2).map {|p| p.join(':') }

edited Aug 22, 2014 at 15:39

answered Aug 22, 2014 at 14:29

Phil Ross

26.2k9 gold badges71 silver badges80 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

Cary Swoveland · Accepted Answer · 2014-08-22 16:14:18Z

2

Here's a way that's short and efficient, and reads well.

a1 = ['x','y','z']
a2 = [1,2]

a1.flat_map { |e| a2.map { |f| "#{e}:#{f}" } }
  #=> ['x:1', 'x:2', 'y:1', 'y:2', 'z:1', 'z:2']

I originally had a2.map { |f| e.to_s+?:+f.to_s }. I replaced flat_map with map and e.to_s+?:+f.to_s with "#{e}:#{f}", as suggested by @PhilRoss and @Stefan, respectively. Thanks to both of you.

edited Aug 22, 2014 at 16:14

answered Aug 22, 2014 at 15:20

Cary Swoveland

111k6 gold badges69 silver badges105 bronze badges

2 Comments

Phil Ross Over a year ago

a2.flat_map could be replaced with a2.map (the result is already flat).

Stefan Over a year ago

I'd use string interpolation "#{e}:#{f}"

the Tin Man · Accepted Answer · 2014-08-22 16:43:37Z

2

My suggestion would be to split the problem into two separate problems. In this case, the following:

iterate through each element on both arrays at once. pushing in the values as we go.
place the string into a branch new array.

While messy, I would perhaps do something along this path:

def foo
  #declare our known values as arrays, and initialize the container of the final result.
  combined_array = []
  array_letters = ['x', 'y', 'z']
  array_numbers = ['1', '2']

  array_letters.each do |letter|
    array_numbers.each do |number|
      combined_array << "#{letter}:#{number}"
    end
  end
  #return our new array
  combined_array
end

Now mind you, I am sure there is a better way to do this. But in consideration, I am fairly certain this should work.

edited Aug 22, 2014 at 16:43

the Tin Man

161k44 gold badges222 silver badges308 bronze badges

answered Aug 22, 2014 at 14:39

tfredett

214 bronze badges

3 Comments

sawa Over a year ago

It works, but it is not a Ruby way. It is the old school way. I won't downvote, but I won't upvote either.

tfredett Over a year ago

never said it was, hence me saying at the very end that there is surely a better way to do this. And this is the case, as demonstrated by Phil.

tfredett Over a year ago

I posted before I saw the answer Phil gave, by the time I posted, Phil had also posted. Therefore, my page updated with both my answer and Phil's.

Collectives™ on Stack Overflow

Ruby: Pair individual values of two arrays into third array

3 Answers 3

Comments

2 Comments

3 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

Comments

2 Comments

3 Comments

Your Answer

Sign up or log in

Post as a guest

Related