From: "rpardee@..." <rpardee@...>
Date: 2009-03-12T00:33:04+09:00
Subject: hash of hashes w/defaults doesn't add keys as expected

Hey All,

This surprised me:

  hash_hash = Hash.new(Hash.new(0))

  hash_hash[:foo][:bar] += 1
  hash_hash[:foo][:baz] += 1

  puts(hash_hash[:foo].keys.inspect)  # => [:baz, :bar]
  puts(hash_hash.keys.inspect)        # => []  ?

Shouldn't hash_hash.keys == [:foo]?  I'm running ruby 1.8.6
(2007-03-13 patchlevel 0) [i386-mswin32].

If this is expected behavior, what's the easiest/best performing way
to make sure those keys are added?

Many thanks!

-Roy