.lein-repl-history

(defn old-book->new-book [book]
  (let [new-books #{} 
        create-books (fn [[x]] (assoc new-books x))]
    (map create-books book)))
exit
(contains? {:authors #{"Rich"}} :authors "Rich")
(contains? (:authors {:authors #{"Rich"}}) "Rich")
(:name {:name "The Shining" :authors #{"Stephen King"}})
(:name (:authors {:name "The Shining" :authors #{"Stephen King"}}))
(map #:name (:authors {:name "The Shining" :authors #{"Stephen King"}}))
(map :name (:authors {:name "The Shining" :authors #{"Stephen King"}}))
(:author {:author "test"})
(defn authors [books]
  (let [book-author
        (fn [book] (:authors book))]
    (set (apply concat (map book-author books)))))
(defn all-author-names [books]
  (let [author-names
       (fn [author] (:name author))]
    (set (apply concat (map author-names (authors books))))))
(authors [{:author {:name "Johnson"}}])
(defn author->string [author]
  (let [author-name (:name author)
        death-year (:death-year author)
        birth-year (:birth-year author)]
    (if (contains? author :birth-year)
      (apply str author-name " (" birth-year " - " death-year ")")
      (str author-name))))
(defn authors->string [authors]
  (apply str (interpose ", " (set (apply concat (map authors->string authors))))))
(authors->string #{{:name "Dan" :birth-year "1991"} {:name "Charles"}})
(#{"Charles (1991 - )" "Dan (1954 -2001)"})
(println #{"Charles (1991 - )" "Dan (1954 -2001)"})
(str #{"Charles (1991 - )" "Dan (1954 -2001)"})
(apply str #{"Charles (1991 - )" "Dan (1954 -2001)"})
(apply str (interpose ", " #{"Charles (1991 - )" "Dan (1954 -2001)"}))
(= nil [])
(= [] [])
(= [] #{})
(= nil #{})
(empty? #{})
(defn has-author? [book author]
  (contains? (:authors book) author))
(filter (has-author? "test") #{})
(filter (has-author? "test" x) #{})
(filter (has-author? "test" book) #{})
(filter (fn [book] (has-author? "test" book)) #{})
(filter (fn [book] (has-author? "test" book)) #{"test"})
(filter (fn [book] (has-author? "dan" book)) #{{:title "test" :authors "dan"}})
(filter #((has-author? "dan" %)) #{{:title "test" :authors "dan"}})
(filter #( (has-author? "dan" %)) #{{:title "test" :authors "dan"}})
(filter #((has-author? "dan" %1)) #{{:title "test" :authors "dan"}})
(contains? (:name "test") {:name "test})
)
(contains? (:name "test") {:name "test"})
(contains? "test" {:name "test"})
(contains? {:name "test"} (:name "test"))
(contains? (:name "test") {:name "test"})
(contains? {:name "test"} "test")