@arahuja, I believe @nealsid suggested it a while back. I can run an experiment in the next few days to check this; I believe that Neal was concerned that we would get better compression if we used strings instead of an array of enums. This should be a straightforward change to make and an easy one to evaluate.

I think the advantage you do get from defining your alphabet via an enum is that you are strictly checking for possible errors; whether this is valuable is another question.