45 lines
1014 B
Plaintext
45 lines
1014 B
Plaintext
;;;; match over an enum: the arms name members as keywords, a _ arm is the
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;;;; rest, and a match that names neither every member nor _ is refused.
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(defenum Dir [north east south west])
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(defn turn [d Dir] Dir
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(match d
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:north :east
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:east :south
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:south :west
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:west :north))
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(defn name [d Dir] str
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(match d
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:north "north"
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:south "south"
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_ "sideways"))
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(defn calls [] i32
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(print "(called) ")
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0)
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;; The scrutinee is evaluated once, however many arms test it.
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(defn once [] Dir
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(calls)
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:west)
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;; recur from inside an arm: the arm is the loop's tail.
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(defn steps-to-west [from Dir] i32
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(loop [d from n 0]
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(match d
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:west n
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_ (recur (turn d) (+ n 1)))))
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(defn main [] i32
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(print (steps-to-west :north)) (println "")
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(println (name :north))
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(println (name (turn :north)))
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(println (name (turn (turn :north))))
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(println (name (once)))
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(match (turn :west)
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:north (println "back to north")
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_ (println "somewhere else"))
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0)
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