Map, filter, reduce example, ClojureBridge Helsinki

gistfile1.clj

(def authors [{:first "Margaret" :last "Atwood"   :books 15}
              {:first "Doris"    :last "Lessing"  :books 67}
              {:first "Ursula"   :last "Le Guin"  :books 23}
              {:first "Alice"    :last "Munro"    :books 21}])

(defn get-name [author]
  (get author :first))

(defn first-name-short? [author]
  (let [first-name (get-name author)
        name-len   (count first-name)]
    (> 7 name-len)))

(defn get-books [author]
  (get author :books))

(def total-books (reduce + (map get-books (filter first-name-short? authors))))

gistfile2.clj

(->> authors
     (filter (comp (partial > 7) count :first))
     (map :books)
     (reduce +))