Autovivification in Ruby

W00t, one of my favourite Perl features can be ported to Ruby in just a single line of code. As everyone knows, in Perl it's possible to write:

$x{a}{b}{c}{d} = "e";

And all intermediate-level hashtables will be created automagically. This is often extremely useful. On the other hand in lesser languages like Python or Java the only way to set a value in a nested hash is to create intermediate-level hashtables by hand:

x={}
x["a"] = {}
x["a"]["b"] = {}
x["a"]["b"]["c"] = {}
x["a"]["b"]["c"]["d"] = "e"

This may be a small thing, but multi-level hashes are used so often that one actually misses this functionality. For long I thought that Ruby doesn't have autovivification. And well, it doesn't have the full Perl thing, but it can get reasonably close with just this small definition:

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

And now you can say:

x = autovivifying_hash
x["a"]["b"]["c"]["d"] = "e"

And that's going to be good enough most of the time :-)