33 lines
1.1 KiB
Clojure
33 lines
1.1 KiB
Clojure
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; "The map function relates a sequence to another"
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(= [4 8 12] (map (fn [x] (* 4 x)) [1 2 3]))
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; "You may create that mapping"
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(= [1 4 9 16 25] (map (fn [x] (* x x)) [1 2 3 4 5]))
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; "Or use the names of existing functions"
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(= '(false false true false false) (map nil? [:a :b nil :c :d]))
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; "A filter can be strong"
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(= () (filter (fn [x] false) '(:anything :goes :here)))
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; "Or very weak"
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(= '(:anything :goes :here) (filter (fn [x] true) '(:anything :goes :here)))
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; "Or somewhere in between"
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(= [10 20 30] (filter (fn [x] (<= x 30)) [10 20 30 40 50 60 70 80]))
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; "Maps and filters may be combined"
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(= [10 20 30] (map (fn [x] (* x 10))
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(filter (fn [x] (<= x 3)) [1 2 3 4 5 6 7 8])))
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; "Reducing can increase the result"
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(= 24 (reduce (fn [a b] (* a b)) [1 2 3 4]))
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; "You can start somewhere else"
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(= 2400 (reduce (fn [a b] (* a b)) (cons 100 [1 2 3 4])))
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; "Numbers are not the only things one can reduce"
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(= "longest" (reduce (fn [a b]
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(if (< (count a)) b a))
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["which" "word" "is" "longest"]))
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