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46 lines
1.2 KiB
Clojure
46 lines
1.2 KiB
Clojure
(ns koans.03-lists
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(:require [koan-engine.core :refer :all]))
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(meditations
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"Lists can be expressed by function or a quoted form"
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(= '(1 2 3 4 5) (list 1 2 3 4 5))
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"They are Clojure seqs (sequences), so they allow access to the first"
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(= 1 (first '(1 2 3 4 5)))
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"As well as the rest"
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(= '(2 3 4 5) (rest '(1 2 3 4 5)))
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"Count your blessings"
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(= 3 (count '(dracula dooku chocula)))
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"Before they are gone"
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(= 0 (count '()))
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"The rest, when nothing is left, is empty"
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(= '() (rest '(100)))
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"Construction by adding an element to the front is easy"
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(= '(:a :b :c :d :e) (cons :a '(:b :c :d :e)))
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"Conjoining an element to a list isn't hard either"
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(= '(:e :a :b :c :d) (conj '(:a :b :c :d) :e))
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"You can use a list like a stack to get the first element"
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(= :a (peek '(:a :b :c :d :e)))
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"Or the others"
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(= '(:b :c :d :e) (pop '(:a :b :c :d :e)))
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"But watch out if you try to pop nothing"
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(= "No dice!" (try
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(pop '())
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(catch IllegalStateException e
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"No dice!")))
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"The rest of nothing isn't so strict"
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(= '() (try
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(rest '())
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(catch IllegalStateException e
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"No dice!"))))
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