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Merge pull request #8 from FrizzBolt/07-functions

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Add solutions to section 07-functions
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Josh Abrams 2016-02-28 17:34:35 -06:00
commit a815ae70ff
1 changed files with 12 additions and 10 deletions
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22
07_functions.clj
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@ -1,32 +1,34 @@
; "Calling a function is like giving it a hug with parentheses" ; "Calling a function is like giving it a hug with parentheses"
(= __ (square 9)) (= (square 9))
; "Functions are usually defined before they are used" ; "Functions are usually defined before they are used"
(= __ (multiply-by-ten 2)) (= (multiply-by-ten 2))
; "But they can also be defined inline" ; "But they can also be defined inline"
(= __ ((fn [n] (* 5 n)) 2)) (= 10 ((fn [n] (* 5 n)) 2))
; "Or using an even shorter syntax" ; "Or using an even shorter syntax"
(= __ (#(* 15 %) 4)) (= 60 (#(* 15 %) 4)) ;; J - This is an important bit of sugar to memorize.
;; To make it easy, '#' initiates the declaration of an anonymous function
;; and % is the argument. So, in this case, # replaces 'fn [n]' and '%' replaces n
; "Even anonymous functions may take multiple arguments" ; "Even anonymous functions may take multiple arguments"
(= __ (#(+ %1 %2 %3) 4 5 6)) (= 15 (#(+ %1 %2 %3) 4 5 6))
; "Arguments can also be skipped" ; "Arguments can also be skipped"
(= __ (#(* 15 %2) 1 2)) (= 30 (#(* 15 %2) 1 2))
; "One function can beget another" ; "One function can beget another"
(= 9 (((fn [] ___)) 4 5)) (= 9 ((fn [] ((fn [a b] (+ a b)) 4 5))))
; "Functions can also take other functions as input" ; "Functions can also take other functions as input"
(= 20 ((fn [f] (f 4 5)) (= 20 ((fn [f] (f 4 5))
___)) *)) ;; J - Mathematical operators in Clojure serve as functions.
; "Higher-order functions take function arguments" ; "Higher-order functions take function arguments"
(= 25 (___ (= 25 (#(% 5)
(fn [n] (* n n)))) (fn [n] (* n n))))
; "But they are often better written using the names of functions" ; "But they are often better written using the names of functions"
(= 25 (___ square)) (= 25 (defn square [n] (* n n)))