From: Harm Aa <nepaccount@...>
Date: 2008-03-11T23:21:11+09:00
Subject: Re: Ordered Collection

Peter Hug wrote:
> If class X has a method <=>(aX), I can sort an Array containing
> instances of X using Array.sort!.
> 
> What I really would like is an array that is always ordered. IOW, I want
> the object to be inserted at the correct location inside the array when
> the object is added to the array.
> 
> Is there an efficient way to do this?
> 
> Pete

One option is to  subclass Array and override the methods you use to 
insert the elements. For example, consider the following:

class OrderedArray < Array
  def []=(index, element)
     push(element)
  end

  def push(element)
    super(element)
    self.sort!
  end
end

You could even add the code to insert the element in the correct place, 
but this is a good start.

Another option is to use delegation to wrap the Array, and just 
implement the methods you desire:

class OrderedArray < Array
  def initialize
    @array = []
  end
  def []=(index, element)
     push(element)
  end

  def [](index)
     @array[index]
  end

  def pop
    @array.pop
  end
  def push(element)
    @array.push(element)
    @array.sort!
  end
end

With kind Regards, Sam and Harm

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