On Nov 11, 2011, at 04:50 , Robert Klemme wrote:

> # ensure every word is only once in memory
> words = Hash.new {|h,k| k.freeze; h[k] = k}

AFAIK, Ruby hashes have (almost) always frozen their keys.

irb(main):001:0> h = {}
=> {}
irb(main):002:0> h["blah"] = 42
=> 42
irb(main):003:0> h.keys.map(&:frozen?)
=> [true]