From: Marnen Laibow-Koser <marnen@...>
Date: 2009-11-19T23:49:07+09:00
Subject: Re: dynamic array?

Freak Guard wrote:
> I'd like to store 2d-data into an dynamic Array. The Matrix class got
> the problem of being static sized and the other solution does not work:
> 
> You can pass a block to Hash#new which gets called if the key does not
> exist
> 
>>> hsh = Hash.new {[]}
> => {}
>>> hsh[3]
> => []
> 
> But this does not seem to work with Arrays...
> 
>>> ary = Array.new {[]}
> => []
>>> ary[2]
> => nil
> 
> Grettings
> FreakGuard

Hmmm...another approach:

class DynamicArray < Hash
  attr_reader :length

  def initialize(length)
    @length = length
    super() {[]}
  end

  def []=(i, value)
    super
    @length = [i + 1, length].max
  end

  def to_a
    (0..length).to_a.collect{|i| self[i]}
  end

  def each(&block)
    self.to_a.each block
  end
end

...and delegate everything else to self.to_a.

Best,
--
Marnen Laibow-Koser
http://www.marnen.org
marnen@marnen.org

  end


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