In a project of mine, I plan on making a "work list" of tuples available to a callback before the work is actually performed. This is naturally kept as a hash, so they can be looked-up by the left part, and still easy enough to process the whole list with each or keys.

However, I wonder if a derived class might want to know the order in which they were added, some day.

Originally I figured that the access method to get the worklist, used strictly internally also for all access to it, could be overridden to return a reference to a tied hash that also keeps an order. It turns out that this actually is a little more complex, because I would also need to provide a method to reset the list. So it's not as cute as I thought.

So I'm thinking why not just provide the order already? I could use such an ordered hash class from the getgo, but I don't see one as a standard module and I want to use only modules that come with the normal Perl installation. Also there might be a performance hit with that.

Or, I can keep a list for the order as well as the hash for the index, explicitly. So, how do I provide access to that?

Storing the ordering as a specially-named member of the hash seems awkward, and less than elegant from a module interface point of view.

Two separate named methods would be clear.

Having multiple return values from a single method would be neater, but would that be awkward too?

I'm open to suggestions and design musings.

—John

In reply to Hashes made to order by John M. Dlugosz

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