Clojure，jvm平台上的又一门函数式语言

Clojure 是什么？

引自官方网站的介绍

引用

Features
    * Dynamic Development
    * Functional Programming
    * Lisp
    * Runtime Polymorphism
    * Concurrent Programming
    * Hosted on the JVM

它基于JVM，能调用Java的类库，支持并发，与Scala（http://www.scala-lang.org/）很相似。先前曾有人将Scala比作是Java平台上的Erlang语言。

官方例子：基于Lisp语法，使用了Java并发库的并发编程

(import '(java.util.concurrent Executors))
(defn test-stm [nitems nthreads niters]
  (let [refs  (map ref (replicate nitems 0))
        pool  (. Executors (newFixedThreadPool nthreads))
        tasks (map (fn [t]
                      (fn []
                        (dotimes n niters
                          (sync nil
                            (dolist r refs
                              (set r (+ @r t)))))))
                   (range nthreads))]
      (. pool (invokeAll tasks))
      (. pool (shutdown))
      (map deref! refs)))
(test-stm 10 10 10000)
(550000 550000 550000 550000 550000 550000 550000 550000 550000 550000)

可见这里的并发只是使用了Java的线程，并非像Scala那样基于Actor模型。

在论坛 http://groups.google.com/group/clojure/browse_thread/thread/2a2b24ffef5d1631 上面，有人提出了这样的对比：

引用

Erlang: The Movie  <=> Clojure: The Podcast
Single Assignment  <=> Immutable Data Structures
Mnesia             <=> STM
ErlangVM           <=> JVM
Hipe               <=> JIT
Pattern Matching   <=> Multimethods
Erlang Shell       <=> REPL
Hot Code Reload    <=> Dynamic Compilation
Behaviours         <=> Extensible Abstractions
Tail Recursion     <=> recur
fun                <=> fn
syntax from 1987   <=> syntax from 1958
EMP2               <=> CL style macros
Fiber/Actor        <=> Termite

有兴趣的朋友，可以到 http://clojure.sourceforge.net/ 下载