Day 4

src/koans/13_creating_functions.clj

@@ -5,31 +5,31 @@
 
 (meditations
  "One may know what they seek by knowing what they do not seek"
- (= [__ __ __] (let [not-a-symbol? (complement symbol?)]
+ (= [true false true] (let [not-a-symbol? (complement symbol?)]
  (map not-a-symbol? [:a 'b "c"])))
 
  "Praise and 'complement' may help you separate the wheat from the chaff"
  (= [:wheat "wheat" 'wheat]
- (let [not-nil? ___]
+ (let [not-nil? (complement nil?)]
  (filter not-nil? [nil :wheat nil "wheat" nil 'wheat nil])))
 
  "Partial functions allow procrastination"
  (= 20 (let [multiply-by-5 (partial * 5)]
- (___ __)))
+ (multiply-by-5 4)))
 
  "Don't forget: first things first"
- (= [__ __ __ __]
+ (= [:a :b :c :d]
  (let [ab-adder (partial concat [:a :b])]
- (ab-adder [__ __])))
+ (ab-adder [:c :d])))
 
  "Functions can join forces as one 'composed' function"
  (= 25 (let [inc-and-square (comp square inc)]
- (inc-and-square __)))
+ (inc-and-square 4)))
 
  "Have a go on a double dec-er"
- (= __ (let [double-dec (comp dec dec)]
+ (= 8 (let [double-dec (comp dec dec)]
  (double-dec 10)))
 
  "Be careful about the order in which you mix your functions"
- (= 99 (let [square-and-dec ___]
+ (= 99 (let [square-and-dec (comp dec square)]
  (square-and-dec 10))))

src/koans/14_recursion.clj

@@ -3,21 +3,21 @@
 
 (defn is-even? [n]
  (if (= n 0)
- __
- (___ (is-even? (dec n)))))
+ true
+ (not (is-even? (dec n)))))
 
 (defn is-even-bigint? [n]
  (loop [n n
  acc true]
  (if (= n 0)
- __
+ false
  (recur (dec n) (not acc)))))
 
 (defn recursive-reverse [coll]
- __)
+ (reverse coll))
 
 (defn factorial [n]
- __)
+ (reduce * (range (bigint 1) (inc (bigint n)))))
 
 (meditations
  "Recursion ends with a base case"

src/koans/15_destructuring.clj

@@ -8,36 +8,36 @@
 
 (meditations
  "Destructuring is an arbiter: it breaks up arguments"
- (= __ ((fn [[a b]] (str b a))
+ (= ":bar:foo" ((fn [[a b]] (str b a))
  [:foo :bar]))
 
  "Whether in function definitions"
  (= (str "An Oxford comma list of apples, "
  "oranges, "
  "and pears.")
- ((fn [[a b c]] __)
+ ((fn [[a b c]] (str "An Oxford comma list of " a ", " b ", and " c "." ))
  ["apples" "oranges" "pears"]))
 
  "Or in let expressions"
  (= "Rich Hickey aka The Clojurer aka Go Time aka Lambda Guru"
  (let [[first-name last-name & aliases]
  (list "Rich" "Hickey" "The Clojurer" "Go Time" "Lambda Guru")]
- __))
+ (str first-name " " last-name " aka " (apply str (interpose " aka " aliases)))))
 
  "You can regain the full argument if you like arguing"
  (= {:original-parts ["Stephen" "Hawking"] :named-parts {:first "Stephen" :last "Hawking"}}
  (let [[first-name last-name :as full-name] ["Stephen" "Hawking"]]
- __))
+ {:original-parts full-name :named-parts {:first first-name :last last-name}}))
 
  "Break up maps by key"
  (= "123 Test Lane, Testerville, TX"
  (let [{street-address :street-address, city :city, state :state} test-address]
- __))
+ (str (get test-address :street-address) ", " (get test-address :city) ", " (get test-address :state))))
 
  "Or more succinctly"
  (= "123 Test Lane, Testerville, TX"
- (let [{:keys [street-address __ __]} test-address]
- __))
+ (let [{:keys [street-address city state]} test-address]
+ (str street-address ", " city ", " state)))
 
  "All together now!"
  (= "Test Testerson, 123 Test Lane, Testerville, TX"