Creating Functions

ClojureScript Koans Creating Functions Answers
http://clojurescriptkoans.com/#creating-functions/1


(defn square [x] (* x x))


1)One may know what they seek by knowing what they do not seek

(= [ true false true ] (let [not-a-symbol? (complement symbol?)] (map not-a-symbol? [:a 'b "c"])))

2)Praise and 'complement' may help you separate the wheat from the chaff

(= [:wheat "wheat" 'wheat] (let [not-nil?  (complement nil?)  ] (filter not-nil? [nil :wheat nil "wheat" nil 'wheat nil])))

3)Partial functions allow procrastination

(= 20 (let [multiply-by-5 (partial * 5)] (multiply-by-5 4)))

4)Don't forget: first things first

(= [:a :b :c :d] (let [ab-adder (partial concat [:a :b])] (ab-adder [:c :d])))

5)Functions can join forces as one 'composed' function

(= 25 (let [inc-and-square (comp square inc)] (inc-and-square  4 )))

6)Have a go on a double dec-er

(=  8  (let [double-dec (comp dec dec)] (double-dec 10)))

7)Be careful about the order in which you mix your functions

(= 99 (let [square-and-dec (comp dec square)] (square-and-dec 10)))