Fix code so that tests pass

src/structured_data.clj

@@ -1,16 +1,18 @@
 (ns structured-data)
 
 (defn do-a-thing [x]
-  :-)
+  (let [xx (+ x x)]
+  (Math/pow xx xx)))
 
 (defn spiff [v]
-  :-)
+  (+ (get v 0) (get v 2)))
 
 (defn cutify [v]
-  :-)
+  (conj v "<3"))
 
 (defn spiff-destructuring [v]
-  :-)
+  (let [[x y z] v]
+    (+ x z)))
 
 (defn point [x y]
   [x y])
@@ -19,96 +21,124 @@
   [bottom-left top-right])
 
 (defn width [rectangle]
-  :-)
+  (let [[[x1 y1] [x2 y2]] rectangle]
+    (- x2 x1)))
 
 (defn height [rectangle]
-  :-)
+  (let [[[x1 y1] [x2 y2]] rectangle]
+    (- y2 y1)))
 
 (defn square? [rectangle]
-  :-)
+  (= (width rectangle) (height rectangle)))
 
 (defn area [rectangle]
-  :-)
+  (* (width rectangle) (height rectangle)))
 
 (defn contains-point? [rectangle point]
-  :-)
+  (let [[[x1 y1] [x2 y2]] rectangle
+        [x3 y3] point]
+    (and (<= x1 x3 x2) (<= y1 y3 y2))))
 
 (defn contains-rectangle? [outer inner]
-  :-)
+  (let [[[x1 y1] [x2 y2]] inner]
+    (and (contains-point? outer [x1 y1])
+         (contains-point? outer [x2 y2]))))
 
 (defn title-length [book]
-  :-)
+  (count (:title book)))
 
 (defn author-count [book]
-  :-)
+  (count (:authors book)))
 
 (defn multiple-authors? [book]
-  :-)
+  (> (author-count book) 1))
 
 (defn add-author [book new-author]
-  :-)
+  (let [new-authors
+        (conj
+          (:authors book)
+          new-author)]
+    (assoc book :authors new-authors)))
 
 (defn alive? [author]
-  :-)
+  (not (contains? author :death-year)))
 
 (defn element-lengths [collection]
-  :-)
+  (map count collection))
 
 (defn second-elements [collection]
-  :-)
+  (let [second-element (fn [coll] (get coll 1))]
+    (map second-element collection)))
 
 (defn titles [books]
-  :-)
+    (map :title books))
 
 (defn monotonic? [a-seq]
-  :-)
+  (or (apply <= a-seq)
+      (apply >= a-seq)))
 
 (defn stars [n]
-  :-)
+  (apply str (repeat n \*)))
 
 (defn toggle [a-set elem]
-  :-)
+  (if (contains? a-set elem)
+    (disj a-set elem)
+    (conj a-set elem)))
 
 (defn contains-duplicates? [a-seq]
-  :-)
+  (if (= (count a-seq) (count (set a-seq)))
+    false
+    true))
 
 (defn old-book->new-book [book]
-  :-)
+  (assoc book :authors (set (:authors book))))
 
 (defn has-author? [book author]
-  :-)
+  (contains? (:authors book) author))
 
 (defn authors [books]
-  :-)
+  (apply clojure.set/union (map :authors books)))
 
 (defn all-author-names [books]
-  :-)
+  (set (map :name (authors books))))
 
 (defn author->string [author]
-  :-)
+  (let [author-name (:name author)
+        birth-year (:birth-year author)
+        death-year (:death-year author)]
+    (if birth-year
+      (str author-name " (" birth-year " - " death-year ")")
+      (str author-name))))
 
 (defn authors->string [authors]
-  :-)
+  (apply str (interpose ", " (map author->string authors))))
 
 (defn book->string [book]
-  :-)
+  (let [title (:title book)
+        authors (authors->string (:authors book))]
+  (str title ", written by " authors)))
 
 (defn books->string [books]
-  :-)
+  (let [book-count (count books)
+        books-authors (interpose ", " (map book->string books))]
+    (cond
+      (= book-count 0) "No books."
+      (= book-count 1) (str (apply str "1 book. " books-authors) ".")
+      :else (str (apply str book-count " books. " books-authors) "."))))
 
 (defn books-by-author [author books]
-  :-)
+  (filter (fn [book] (has-author? book author)) books))
 
 (defn author-by-name [name authors]
-  :-)
+  (first (filter (fn [author] (= (:name author) name)) authors)))
 
 (defn living-authors [authors]
-  :-)
+  (filter (fn [author] (alive? author)) authors))
 
 (defn has-a-living-author? [book]
-  :-)
+  (not (empty? (living-authors (:authors book)))))
 
 (defn books-by-living-authors [books]
-  :-)
+  (filter (fn [book] (has-a-living-author? book)) books))
 
 ; %________%