Extract values from multiple arrays one by one.

extract_from_arrays.rb

# The arrays should not contain nil.
ary1 = [1, 2]
ary2 = %w(A B C)
ary3 = %i(a b)

while (elm = ary1.shift || ary2.shift || ary3.shift) do
  p elm
end
#=> 1
#=> 2
#=> "A"
#=> "B"
#=> "C"
#=> :a
#=> :b

# Iterate in reverse order likewise:
ary1 = [1, 2]
ary2 = %w(A B C)
ary3 = %i(a b)

while (elm = ary3.pop || ary2.pop || ary1.pop) do
  p elm
end
#=> :b
#=> :a
#=> "C"
#=> "B"
#=> "A"
#=> 2
#=> 1