It's a simple port that avoids mutation entirely. The fact that it's only slightly slower than the Python version says a lot about Clojure performance. In anyc

It's a simple port that avoids mutation entirely. The fact that it's only slightly slower than the Python version says a lot about Clojure performance. In anycase, the OP was clear, the goal was to write a comparison of the original design, not to write the fastest Clojure program (and there are many ways to make the Clojure version faster, yet it's not clear to me how to best Norvig's design in pure Python).