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rss中的关键词统计

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pcall 并发执行多个无参方法

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future 用法

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CountDownLatch 同步计数器

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A Delay ensures that some code is either run zero or one time. It's run zero times if the Delay is never derefed.

Delays are also useful for a shared resource between threads.

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promise vs future

reference: stackeroverflow

promise

1. You create a promise. That promise object can now be passed to any thread.
2. You continue with calculations. These can be very complicated calculations involving side-effects, downloading data, user input, database access, other promises – whatever you like. The code will look very much like your mainline code in any program.
3. When you’re finished, you can deliver the results to that promise object.
4. Any item that tries to deref your promise before you’re finished with your calculation will block until you’re done. Once you’re done and you’ve delivered the promise, the promise won’t block any longer.

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clojure atom实现缓存

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clojure mapcat用法

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clojure pmap 用法

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;;
;; clojure.core
;; 延迟执行并缓存
;; add something
(comment
  (defmacro delay
   "Takes a body of expressions and yields a Delay object that will
   invoke the body only the first time it is forced (with force or deref/@), and
   will cache the result and return it on all subsequent force
   calls. See also - realized?"