Queue/Definition: Difference between revisions
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(→{{header|Clojure}}: changed in dequeue to if-let to destructure, and reset! to replace the atom's value) |
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The "pop" function implies mutating the input, but since Clojure data structures are immutable we use a mutable reference to an immutable data structure; in this case an <tt>atom</tt> holding a vector: |
The "pop" function implies mutating the input, but since Clojure data structures are immutable we use a mutable reference to an immutable data structure; in this case an <tt>atom</tt> holding a vector: |
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<lang |
<lang clojure>(defn make-queue [] |
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(atom [])) |
(atom [])) |
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(defn dequeue [q] |
(defn dequeue [q] |
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(if (seq @q) |
(if-let [[f & r] (seq @q)] |
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( |
(do (reset! q r) f) |
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(swap! q subvec 1) |
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x) |
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(throw (IllegalStateException. "Can't pop an empty queue.")))) |
(throw (IllegalStateException. "Can't pop an empty queue.")))) |
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(empty? @q))</lang> |
(empty? @q))</lang> |
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The implementation is thread-safe if there is at most one |
The implementation is thread-safe if there is at most one writer thread, i.e. only one thread ever calls <code>dequeue</code> on a given queue. |
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=={{header|CoffeeScript}}== |
=={{header|CoffeeScript}}== |
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