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inish chapter 7

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徐国方 2017-03-06 11:32:06 +08:00
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src/koans/07_functions.clj
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@ -8,33 +8,33 @@
(meditations (meditations
"Calling a function is like giving it a hug with parentheses" "Calling a function is like giving it a hug with parentheses"
(= __ (square 9)) (= 81 (square 9))
"Functions are usually defined before they are used" "Functions are usually defined before they are used"
(= __ (multiply-by-ten 2)) (= 20 (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))
"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 (#(+ %1 %2) 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))
___)) #(+ %1 %2)))
"Higher-order functions take function arguments" "Higher-order functions take function arguments"
(= 25 (___ (= 25 ((fn [f] (f 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 ((fn [f] (f 5)) square)))