From: "David A. Black" <dblack@...>
Date: 2007-11-05T19:27:19+09:00
Subject: Re: x=[]; x[:bla][:some_key] does not work?

Hi --

On Mon, 5 Nov 2007, Bob Hutchison wrote:

> I've been using Ruby for years and I'm still startled by what you can do when 
> passing blocks to initializers. A few weeks ago I stumbled on this:
>
> Hash.new{ | h, k | h[k] = Array.new }
>
> which is just a hash of arrays, completely trivial really, but I'd never 
> thought of it before, and now I'm using it all over the place.

My favorite is:

   class NonexistentKeyError < StandardError
   end

   hash = Hash.new {|h,k| raise NonexistentKeyError, "No such key: #{k}" }

:-)


David

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