From: "David A. Black" <dblack@...>
Date: 2009-01-10T23:53:49+09:00
Subject: Re: Default values of hashes

Hi --

On Wed, 7 Jan 2009, Glenn wrote:

> Thanks for the tips.  I learned a lot from all of the suggestions.
>
> Not sure, though, if I understand this line:
>
> hash[1][2][3] = Hash.new(0)
>
> Is that a valid line on its own.  If so, it does not seem to work for me.  I get the following error:
>
> undefined method `[]=' for 0

Here's how to use it:

>> hproc = lambda {|h,k| h[k] = Hash.new(&hproc) }
=> #<Proc:0x00248420@(irb):14>
>> hash = Hash.new(&hproc)
=> {}
>> hash[1][2][3] = Hash.new(0)
=> {}
>> hash[1][2][3]["x"] += 10
=> 10
>> hash[1][2][3]
=> {"x"=>10}


David

-- 
David A. Black / Ruby Power and Light, LLC
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