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36 lines
1.1 KiB
Clojure
36 lines
1.1 KiB
Clojure
(ns koans.13-creating-functions
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(:require [koan-engine.core :refer :all]))
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(defn square [x] (* x x))
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(meditations
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"One may know what they seek by knowing what they do not seek"
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(= [true false true] (let [not-a-symbol? (complement symbol?)]
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(map not-a-symbol? [:a 'b "c"])))
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"Praise and 'complement' may help you separate the wheat from the chaff"
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(= [:wheat "wheat" 'wheat]
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(let [not-nil? (complement nil?)]
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(filter not-nil? [nil :wheat nil "wheat" nil 'wheat nil])))
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"Partial functions allow procrastination"
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(= 20 (let [multiply-by-5 (partial * 5)]
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(multiply-by-5 4)))
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"Don't forget: first things first"
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(= [:a :b :c :d]
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(let [ab-adder (partial concat [:a :b])]
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(ab-adder [:c :d])))
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"Functions can join forces as one 'composed' function"
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(= 25 (let [inc-and-square (comp square inc)]
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(inc-and-square 4)))
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"Have a go on a double dec-er"
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(= 8 (let [double-dec (comp dec dec)]
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(double-dec 10)))
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"Be careful about the order in which you mix your functions"
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(= 99 (let [square-and-dec (comp dec square)]
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(square-and-dec 10))))
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