The chunking behaviour is transparent unless you have a side-effect in your sequence function, which isn't sensible anyway. The chunked behaviour performs sign

The chunking behaviour is transparent unless you have a side-effect in your sequence function, which isn't sensible anyway. The chunked behaviour performs significantly better for the majority of cases which is why it's on by default, I believe. Rich (creator of Clojure) addressed concerns similar to yours in this reddit discussion: http://www.reddit.com/r/programming/comments/afyav/clojure_11_rc1_out_cuts_some_overhead_of/c0headd http://www.reddit.com/r/programming/comments/afyav/clojure_1... He also discusses chunked sequences in a video here (near the bottom of the list, the sound is pretty bad): http://tomfaulhaber.blip.tv/ http://tomfaulhaber.blip.tv/