;; Sock Merchant problem.
(defn match_socks
  "Given a list of integers, return the number of distinct pairs that could be made."
  [socks]
  ; Build a map of the counts for each number
  (def totals (reduce #(assoc %1 %2 (inc (%1 %2 0))) {} socks))
  ; Reduce the counts map by counting the pairs for each number
  (reduce (fn [total socks] (+ total (int (/ (last socks) 2)))) 0 totals)
)