Suppose I have:

a = [['a', 'b', 'c', 'd', 'e'], ['f', 'g', 'h'], ['i', 'j'], ['k']]

And from that, I want to join pairs but leave a remainder element unchanged like so:

[["a_b", "c_d", "e"], ["f_g", "h"], ["i_j"], ["k"]]

Closest I have (that produces the result) is:

r = a.map { |sl| 
  tmp = []
  sl.each_slice(2) { |a, b| tmp << (b.nil? ? a : "#{a}_#{b}") }
  tmp
}

Alternatively:

r = a.map { |sl| 
  tmp = []
  sl.each_slice(2) { |a, b| tmp << (b.nil? ? a : [a,b].join("_")) }
  tmp
}

Is there a cleaner way to do this?

CodePudding user response：

Is there a cleaner way to do this?

• each_slice returns an Enumerator if no block is given.
• Enumerator responds to map
• map will yield the full "sliced" sub array to the block
• each_slice does not guarantee an n element array. If the slice is uneven then it will just yield what is left.

Knowing all of this your implementation can be simplified to:

a.map { |s1| s1.each_slice(2).map { |e| e.join("_") } }