Write some code, that will flatten an array of arbitrarily nested arrays of integers into a flat array of integers. e.g. [[1,2,[3]],4] -> [1,2,3,4].

citrusbyte.rb

# a = [[1,2,[3]],4]
# aux = []
def flatten(a, aux)
  a.each do |n|
    if n.instance_of?(Fixnum)
      aux<<n
    elsif n.instance_of?(Array)
      flatten(n, aux)
    end
  end
  aux
end