From: gwtmp01@...
Date: 2006-08-15T01:52:44+09:00
Subject: Re: A use case for an ordered hash


On Aug 14, 2006, at 12:15 PM, Martin DeMello wrote:

> On 8/14/06, Austin Ziegler <halostatue@gmail.com> wrote:
>> On 8/14/06, Martin DeMello <martindemello@gmail.com> wrote:
>> > OHash or Assoc or even Dict (though the latter at least implies  
>> an O(1) lookup).
>>
>> Wouldn't it be the same as Hash lookup? It's still got every other
>> characteristic of a Hash; it just guarantees an order that  
>> defaults to
>> insertion order.
>
> True, I suppose you could do it with a doubly linked list overlaid on
> a hash. Was thinking of sorted order.

Can't you just maintain an internal array representing the key insertion
order?  Something like:

class OHash < Hash
   # ...
   def each
      keyseq.each { |k| yield k, self[k] }
   end
end

Where keyseq is just an array that is updated whenever keys are
added/deleted?


Gary Wright