Ruby Autovivifying (Nested Hashes without having to declare the hashes in the tree first)

autovivifying_ruby.rb

def autovivifying_hash
   Hash.new {|ht,k| ht[k] = autovivifying_hash}
end

hash = autovivifying_hash
hash['a']['b']['c']['d']['e'] = 'hello'

puts hash['c']
puts hash['a']
puts hash['b']
puts hash['a']['b']
puts hash

=>
{}
{"b"=>"hello"}
{}
hello
{"a"=>{"b"=>"hello"}, "c"=>{}, "b"=>{}}