Question

How do I iterate the elements of an array in Ruby and in each step I can do something with the array containing all elements, except the one that is iterated in the moment?

For instance for [4,2,8] I iterate the elements and then I can do something with

• [2,8]
• [4,8]
• [4,2]

Answer 1

It’s not really directly possible (unless you do not need the missing element). But you can program it yourself:

Option 1 – just do it:

a = [11,22,33,44,55]

a.each_with_index { |e,i|
  p e
  p a.take(i) + a[i+1..-1]
}

Option 2 – integrate with Array:

class Array
  def each_excluded(&block)
    self.each_with_index { |e, i|
      yield(e, self.take(i) + self[i+1..-1])
    }
  end
end

a.each_excluded { |e, rest|
  p e
  p rest
}

Output from either one:

11
[22, 33, 44, 55]
22
[11, 33, 44, 55]
33
[11, 22, 44, 55]
44
[11, 22, 33, 55]
55
[11, 22, 33, 44]