Ah, I stand corrected. The last time I used Clojure (a few years ago), recur needed to be used with loop. That looks plenty close enough to the Scheme.
I disagree that the Ruby example is sufficient, though. Remember, SICP is intended as an introduction to programming. A chapter like this is useful to people who do /not/ understand TCO, recursion, and the stack already. Understanding it and using that knowledge to translate the exercises is different than having a shaky grasp lisp, scheme, and the "interpretation of computer programs"
I disagree that the Ruby example is sufficient, though. Remember, SICP is intended as an introduction to programming. A chapter like this is useful to people who do /not/ understand TCO, recursion, and the stack already. Understanding it and using that knowledge to translate the exercises is different than having a shaky grasp lisp, scheme, and the "interpretation of computer programs"