I was going to chime in to say that moving from a vector to a recursive reversed list-based implementation for a mere 3x performance gain was a premature optimi

I was going to chime in to say that moving from a vector to a recursive reversed list-based implementation for a mere 3x performance gain was a premature optimization at the expense of readability. Then I actually read your code and the two implementations looked nearly identical, so I guess I'll just leave this here. n.b. - I have actually done a bit of Clojure programming myself but the fine points you and Fogus are discussing here are largely over my head, at least juding by the code sample.