Functions

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

(defn multiply-by-ten [n] (* 10 n))  
(defn square [n] (* n n))  
  
  
1)Calling a function is like giving it a hug with parentheses

(=  81  (square 9))

2)Functions are usually defined before they are used

(=  20  (multiply-by-ten 2))

3)But they can also be defined inline

(=  10  ((fn [n] (* 5 n)) 2))

4)Or using an even shorter syntax

(=  60  (#(* 15 %) 4))

5)Even anonymous functions may take multiple arguments

(=  15  (#(+ %1 %2 %3) 4 5 6))

6)Arguments can also be skipped

(=  30  (#(* 15 %2) 1 2))

7)One function can beget another

(= 9 (((fn []  (fn[x y](+ x y))  )) 4 5))

8)Functions can also take other functions as input

(= 20 ((fn [f] (f 4 5))  * ))


9)Higher-order functions take function arguments

(= 25 (  (fn [f] (f 5))  (fn [n] (* n n))))

10)But they are often better written using the names of functions

(= 25 (  (fn [f] (f 5))  square))