[dkersten]

       (map 
         (defn f [c] 
           {:overlap-amount (circle-overlap-distance circle c) 
            :mid-point      (mid-point circle c)}) 
         circle-list)

Is there a reason this uses defn instead of fn? This is the first time I've seen defn used like this.

Since this expands to something like (def f (fn [c] ... and f is never used anywhere, I'd change it to fn. If f is used, I'd consider letfn instead.

The revised code replaces it with #(...) which is shorthand for (fn [...] ...), but am curious if there was a reason for using defn or if it was just an oversight.

[numergent]

No particular reason, actually, that was unnecessary. I could also just have done #(hash-map :overlap-amount ... :mid-point ...)

I believe it was an independent function initially that I just plunked in there right before setting the gist live, since I wasn't using it anywhere else, but that was back in January.