From: Bob Hutchison <hutch@...>
Date: 2007-11-05T12:50:43+09:00
Subject: Re: x=[]; x[:bla][:some_key] does not work?


On 3-Nov-07, at 4:44 PM, Sebastian Hungerecker wrote:

>
> blk = lambda {|h,k| h[k] = Hash.new(&blk)}
> x = Hash.new(&blk)
> x[:la][:li][:lu][:chunky][:bacon][:foo] = "bar"
>
>


On 4-Nov-07, at 4:34 AM, Jimmy Kofler wrote:

> a = Hash.new{|h,k| h[k]=Hash.new(&h.default_proc) }

Very nice, Sebastian and Jimmy.

Leading to the obvious...

class NestedHash < Hash
   def initialize
     blk = lambda {|h,k| h[k] = NestedHash.new(&blk)}
     super(&blk)
   end
end

class Hash
   def Hash.new_nested_hash
     Hash.new{|h,k| h[k]=Hash.new(&h.default_proc) }
   end
end

... and with no comment on propriety.

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.

And I was really impressed with Ruby when I discovered using blocks  
with gsub.

Cheers,
Bob

----
Bob Hutchison                  -- tumblelog at http://www.recursive.ca/so/
Recursive Design Inc.          -- weblog at http://www.recursive.ca/hutch
http://www.recursive.ca/       -- works on http://www.raconteur.info/cms-for-static-content/home/