hobbit.clj

(ns hobbit)

(defn asym-hobbit-body-parts [{:name "head" :size 3}
                              {:name "left-eye" :size 1}
                              {:name "left-ear" :size 1}
                              {:name "mouth" :size 1}
                              {:name "nose" :size 1}
                              {:name "neck" :size 2}
                              {:name "left-shoulder" :size 3}
                              {:name "left-upper-arm" :size 3}
                              {:name "chest" :size 10}
                              {:name "back" :size 10}
                              {:name "left-forearm" :size 3}
                              {:name "abdomen" :size 6}
                              {:name "left-kidney" :size 1}
                              {:name "left-hand" :size 2}
                              {:name "left-knee" :size 2}
                              {:name "left-thigh" :size 4}
                              {:name "left-lower-leg" :size 3}
                              {:name "left-achilles" :size 1}
                              {:name "left-foot" :size 2}])
    
(defn matching-part 
    [part]
    {:name (clojure.string/replace (:name part) #"^left-" "-right")
     :size (:size part)})

(defn symmetrize-body-parts
    "expects a seq that have :name and :size"
    [asym-body-parts]
    (loop [remaining-asym-parts asym-body-parts
           final-body-parts []]
          (if (empty? remaining-asym-parts)
           final-body-parts
           (let [[ part & remaininig] remaining-asym-parts]
            (recur remaining 
                (into final-body-parts
                    (set [part (matching-part part)])))))))

(defn better-symmetrize-body-parts
 [asym-body-parts]
 (reduce (fn [final-body-parts part]
          (into final-body-parts (set [part (matching-part part)])))
         []
         asym-body-parts))

(defn hit 
    [asym-body-parts]
    let [sym-parts (better-symmetrize-body-parts asym-body-parts)
         body-part-size-sum (reduce + (map :size sym-parts))
         target (rand body-part-size-sum)]
        (loop [[part & remaining] sym-parts
               accumulated-size (:size part)]
         (if (> accumulated-size target)
          part
          (recur remaining (+ accumulated-size (:size (first remaining)))))))

What are you trying to accomplish with the hit function here?

https://gist.github.com/oakmac/571cba7e36e25a117341afdf3bcad5a0