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37 lines
1.0 KiB
Clojure
37 lines
1.0 KiB
Clojure
(ns koans.12-sequence-comprehensions
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(:require [koan-engine.core :refer :all]))
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(meditations
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"Sequence comprehensions can bind each element in turn to a symbol"
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(= '( 0 1 2 3 4 5 )
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(for [x (range 6)]
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x))
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"They can easily emulate mapping"
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(= '(0 1 4 9 16 25)
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(map (fn [x] (* x x))
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(range 6))
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(for [x (range 6)]
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(* x x)))
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"And also filtering"
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(= '(1 3 5 7 9)
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(filter odd? (range 10))
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(for [x (range 10) :when (odd? x)]
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x))
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"Combinations of these transformations is trivial"
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(= '(1 9 25 49 81)
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(map (fn [x] (* x x))
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(filter odd? (range 10)))
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(for [x (range 10) :when (odd? x)]
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(* x x)))
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"More complex transformations simply take multiple binding forms"
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(= [[:top :left] [:top :middle] [:top :right]
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[:middle :left] [:middle :middle] [:middle :right]
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[:bottom :left] [:bottom :middle] [:bottom :right]]
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(for [row [:top :middle :bottom]
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column [:left :middle :right]]
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[row column])))
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