Flatten a hash structure

flatten_hash.rb

def flatten_hash(hash={}, context="", new_hash={})
  hash.each do |key, value|
    flattened_key = context.empty? ? key : "#{context}_#{key}"
    if value.respond_to? :key
      flatten_hash(value, flattened_key, new_hash)
    else
      new_hash[flattened_key]=value
    end
  end
  new_hash
end

structure = { "one" => "a", "two" => {'three' => 'b', 'four' => 'c'}}
# should yield {"one"=>"a", "two_three"=>"b", "two_four"=>"c"}
puts flatten_hash(structure)