Thanks. Yeah, fast anything code tends to be not very pretty to look at and I'm not a very experienced lisper. But fortunately in most real-world programs the part that is performance critical tends to be very small compared to the rest of the program.

Oh, I didn't mean it as a criticism -- I'm afraid it has to be that way. My Common Lisp code that has been optimized looks similar (sprinkled with type declarations in various places).

Well being a seasonned clojurist, i almost never dug into such low level optimizations, but nonetheless , i find his code ok and very readable.

The only function sacrificing some level of readability (and wich i still find quite easy to read) is the new split function.

I think it is very much a question of being accustomed to the particular style of code lisps enforce. On this topic, the only grip i've got with his functions on the style side is, lots of java interop wich lenghtens the whole thing quite a bit, and big bulky functions that would benefit being cutted in several pieces.