Flatten an array entirely using recursion. (I am particularly amazed at how short and simple this is compared to using iteration)

flatten_recursive.rb

def flatten(array)
  return Array(array) unless array.is_a?(Array) && array.length > 0
  flatten(array.shift) + flatten(array)
end


array = ["bananas", [1,2,3], ["apple", "cheese", [100, 20]], [true], [4.0, 7, 32]]
puts flatten(array).to_s

array = ["bananas"]
puts flatten(array).to_s

array = "bananas"
puts flatten(array).to_s

array = [[["bananas"], nil]]
puts flatten(array).to_s

array = nil.to_a
puts flatten(array).to_s