一位Erlang程序员的自白

最新推荐文章于 2025-12-05 15:36:57 发布

最新推荐文章于 2025-12-05 15:36:57 发布 · 130 阅读

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#操作系统 #数据库 #嵌入式

本文介绍了Erlang语言的核心特点，包括热更新、天生的分布式特性和强大的并发能力，并探讨了学习Erlang的一些困惑及该语言的应用场景。

<meta http-equiv="Content-Type" content="text/html; charset=utf-8"> <meta name="ProgId" content="Word.Document"> <meta name="Generator" content="Microsoft Word 12"> <meta name="Originator" content="Microsoft Word 12"> <link rel="File-List" href="file:///C:%5CWindows%5CTEMP%5Cmsohtmlclip1%5C01%5Cclip_filelist.xml"> <link rel="Preview" href="file:///C:%5CWindows%5CTEMP%5Cmsohtmlclip1%5C01%5Cclip_preview.wmf"> <link rel="themeData" href="file:///C:%5CWindows%5CTEMP%5Cmsohtmlclip1%5C01%5Cclip_themedata.thmx"> <link rel="colorSchemeMapping" href="file:///C:%5CWindows%5CTEMP%5Cmsohtmlclip1%5C01%5Cclip_colorschememapping.xml"> <smallfrac m:val="off"><dispdef><lmargin m:val="0"><rmargin m:val="0"><defjc m:val="centerGroup"><wrapindent m:val="1440"><intlim m:val="subSup"><narylim m:val="undOvr"></narylim></intlim></wrapindent><style>  </style> <h1 style="text-align: center; line-height: 150%;" align="center"> <span lang="EN-US">Erlang</span><span style="font-family: 宋体;">不能错过的盛宴</span> </h1> <p class="MsoNormal" style="text-align: center; line-height: 150%;" align="center"><span style="font-family: 宋体;">（快步进入</span><span lang="EN-US">Erlang</span><span style="font-family: 宋体;">的世界）</span></p> <p class="MsoNormal" style="text-align: center; line-height: 150%;" align="center"><span style="font-family: 宋体;">作者：成立涛</span><span lang="EN-US"> (<a href="mailto:litaocheng@gmail.com">litaocheng@gmail.com</a>) </span></p> <p class="MsoNormal" style="text-indent: 21pt; line-height: 150%;"><span style="font-family: 宋体;">作为程序员，我们曾经闻听很多“业界动态”，“技术革新”，曾经接触很多“高手箴言”，“权威推荐”。这些正确与否，都已成过去！</span></p> <p class="MsoNormal" style="text-indent: 21pt; line-height: 150%;"><span style="font-family: 宋体;">现在，让我们迎接</span><span lang="EN-US">Erlang</span><span style="font-family: 宋体;">盛宴！</span></p> <h2 style="line-height: 150%;"><span style="font-family: 黑体;">一、经历</span></h2> <p class="MsoNormal" style="text-indent: 21pt; line-height: 150%;"><span lang="EN-US">2007</span><span style="font-family: 宋体;">年</span><span lang="EN-US">11</span><span style="font-family: 宋体;">月在</span><span lang="EN-US">koders.com</span><span style="font-family: 宋体;">搜索代码时，发现</span><span lang="EN-US">*.erl</span><span style="font-family: 宋体;">格式的源文件，感叹开发语言的花样百出，此时，我觉得</span><span lang="EN-US">erlang</span><span style="font-family: 宋体;">是一个丑陋的小家伙，看名字就没有对它提起多少兴趣。</span></p> <p class="MsoNormal" style="text-indent: 21pt; line-height: 150%;"><span lang="EN-US">2008</span><span style="font-family: 宋体;">年初的时候，公司的项目开发中，我有缘认识了</span><span lang="EN-US">ejabberd</span><span style="font-family: 宋体;">，一个采用</span><span lang="EN-US">Erlang</span><span style="font-family: 宋体;">开发的开源</span><span lang="EN-US">jabber</span><span style="font-family: 宋体;">服务器。我开始为其诱人的特性所倾倒。是时候认真看看</span><span lang="EN-US">Erlang</span><span style="font-family: 宋体;">到底什么样了！</span></p> <p class="MsoNormal" style="text-indent: 21pt; line-height: 150%;"><span lang="EN-US">2008</span><span style="font-family: 宋体;">年</span><span lang="EN-US">4</span><span style="font-family: 宋体;">月，通过各种资料的搜集，了解，我决定系统的学习</span><span lang="EN-US">Erlang</span><span style="font-family: 宋体;">。</span></p> <p class="MsoNormal" style="text-indent: 21pt; line-height: 150%;"><span style="font-family: 宋体;">今天，通过</span><span lang="EN-US">4</span><span style="font-family: 宋体;">个月的认真学习，我已经熟悉了</span><span lang="EN-US">Erlang</span><span style="font-family: 宋体;">，已经在使用</span><span lang="EN-US">Erlang</span><span style="font-family: 宋体;">开发项目。作为</span><span lang="EN-US">C++</span><span style="font-family: 宋体;">程序员，我不敢妄自使用“熟悉”，“精通”之类的字眼，但是对于</span><span lang="EN-US">Erlang</span><span style="font-family: 宋体;">我可以很负责任的说：</span><span lang="EN-US">Erlang</span><span style="font-family: 宋体;">很巧，很强大！</span></p> <h2 style="line-height: 150%;"><span style="font-family: 黑体;">二、困惑</span></h2> <p class="MsoNormal" style="text-indent: 21pt; line-height: 150%;"><span style="font-family: 宋体;">面对一个新的事务，我们本性都会充满好奇，可是作为程序员，很多时候对于新的语言我们都充满了抵触：这个新东西值得学习么？它会不会让我抛弃旧爱？它文档丰富么？是不是很难理解？它的前景如何</span><span lang="EN-US">?</span><span style="font-family: 宋体;">······相信大家跟我有一样的苦恼。</span></p> <p class="MsoNormal" style="text-indent: 21pt; line-height: 150%;"><span style="font-family: 宋体;">但是，请听我说！我们是程序员，我们走在技术革新的最前沿。用户的产品，体验是通过我们来产生！我们不能畏缩不前，我们的固步自封，就是我们的公司，乃至整个行业的停滞不前！口号可能有些响亮，但是认真思考，我相信朋友们一定有所感悟。</span></p> <h2 style="line-height: 150%;"> <span style="font-family: 黑体;">三、</span><span lang="EN-US">Erlang</span><span style="font-family: 黑体;">是什么</span> </h2> <p class="MsoNormal" style="text-indent: 21pt; line-height: 150%;"><span lang="EN-US">Erlang</span><span style="font-family: 宋体;">是什么是我们最先要面对的问题，只有清楚了它是什么，我们才能做出我们的决定。可见这个问题的重要性，它决定了很多读者是否会继续看下去！非常紧张。</span></p> <p class="MsoNormal" style="text-indent: 21pt; line-height: 150%;"><span lang="EN-US">Erlang</span><span style="font-family: 宋体;">最初是爱立信为开发电信相关产品而产生。</span></p> <p class="MsoNormal" style="text-indent: 21pt; line-height: 150%;"><span lang="EN-US">Erlang</span><span style="font-family: 宋体;">是一种面向并发</span><span lang="EN-US">(Concurrency Oriented)</span><span style="font-family: 宋体;">，面向消息（</span><span lang="EN-US">Message Oriented</span><span style="font-family: 宋体;">）的函数式</span><span lang="EN-US">(Functional)</span><span style="font-family: 宋体;">编程语言。</span></p> <p class="MsoNormal" style="text-indent: 21pt; line-height: 150%;"><span style="font-family: 宋体;">面向并发说明</span><span lang="EN-US">Erlang</span><span style="font-family: 宋体;">支持大规模的并发应用，我们可以在应用中处理成千上万的并发，而不相互影响。面向消息，其实是为并发服务！我们应该都熟悉多线程，熟悉加锁解锁操作，熟悉可能出现的资源竞争与死锁。在</span><span lang="EN-US">Erlang</span><span style="font-family: 宋体;">的世界里，我们可以将轻轻的抹去这些令人苦恼的词汇。</span><span lang="EN-US">Erlang</span><span style="font-family: 宋体;">的世界，每个处理都是独立的个体，他们之间的交互仅仅靠消息！因此不会有死锁，不会有那种痛苦的编程经历。</span></p> <p class="MsoNormal" style="text-indent: 21pt; line-height: 150%;"><span lang="EN-US">Erlang</span><span style="font-family: 宋体;">中一个非常重要的名词：</span><span lang="EN-US">Process</span><span style="font-family: 宋体;">，也就是我们前面提到的“个体”。它不是我们操作系统中的进程，也不是线程。它是</span><span lang="EN-US">Erlang</span><span style="font-family: 宋体;">提供给我们的超级轻量的进程。为了适应大规模并发的特性，</span><span lang="EN-US">Process</span><span style="font-family: 宋体;">需要能够快速创建，快速销毁。</span><span lang="EN-US">Process</span><span style="font-family: 宋体;">之间通信的唯一方法就是消息，我们只要知道一个</span><span lang="EN-US">Process</span><span style="font-family: 宋体;">的名字即</span><span lang="EN-US">pid</span><span style="font-family: 宋体;">，就可以向其发送消息。</span><span lang="EN-US">Process</span><span style="font-family: 宋体;">也可以在任何时候，接收消息。我们这样做只有一个目的：让我们的系统更加简单，用一种朴素的做法，实现一个高效的语言。</span></p> <p class="MsoNormal" style="text-indent: 21pt; line-height: 150%;"><span lang="EN-US">Erlang</span><span style="font-family: 宋体;">是种函数式编程语言，对此我没有很深刻的理解，最明显的特征就是，</span><span lang="EN-US">Erlang</span><span style="font-family: 宋体;">中到处都是函数，函数构成了我们的产品的主体，把这些函数放到一个个的</span><span lang="EN-US">Process</span><span style="font-family: 宋体;">中去，让他们运行起来，那么就组成了我们朝气蓬勃的产品。</span></p> <p class="MsoNormal" style="text-indent: 21pt; line-height: 150%;"><span lang="EN-US">Erlang</span><span style="font-family: 宋体;">支持对数据的位操作，拥有丰富的数据持久化机制。</span></p> <p class="MsoNormal" style="text-indent: 21pt; line-height: 150%;"><span style="font-family: 宋体;">同时需要说明的是</span><span lang="EN-US">Erlang</span><span style="font-family: 宋体;">内建垃圾回收机制（</span><span lang="EN-US">GC</span><span style="font-family: 宋体;">）。</span></p> <h2 style="line-height: 150%;"> <span style="font-family: 黑体;">四、</span><span lang="EN-US">Erlang</span><span style="font-family: 黑体;">的语言特性</span> </h2> <h3 style="line-height: 150%;"> <span lang="EN-US">1.</span><span style="font-family: 宋体;">简单小巧</span> </h3> <p class="MsoNormal" style="text-indent: 21pt; line-height: 150%;"><span lang="EN-US">Erlang</span><span style="font-family: 宋体;">中只有</span><span lang="EN-US">8</span><span style="font-family: 宋体;">种基本的数据类型：</span></p> <p class="MsoNormal" style="line-height: 150%;"><span lang="EN-US">integer</span><span style="font-family: 宋体;">、</span><span lang="EN-US">float</span><span style="font-family: 宋体;">、</span><span lang="EN-US">atom</span><span style="font-family: 宋体;">、</span><span lang="EN-US">reference</span><span style="font-family: 宋体;">、</span><span lang="EN-US">fun</span><span style="font-family: 宋体;">、</span><span lang="EN-US">port</span><span style="font-family: 宋体;">、</span><span lang="EN-US">pid</span><span style="font-family: 宋体;">、</span><span lang="EN-US">bitstring</span></p> <p class="MsoNormal" style="line-height: 150%;"><span style="font-family: 宋体;">同时提供</span><span lang="EN-US">2</span><span style="font-family: 宋体;">种复合结构：</span><span lang="EN-US">tuple</span><span style="font-family: 宋体;">，</span><span lang="EN-US">list</span><span style="font-family: 宋体;">，这就是</span><span lang="EN-US">Erlang</span><span style="font-family: 宋体;">的所有数据类型。</span></p> <h3 style="line-height: 150%;"> <span lang="EN-US">2.</span><span style="font-family: 宋体;">模式匹配</span> </h3> <p class="MsoNormal" style="text-indent: 21pt; line-height: 150%;"><span style="font-family: 宋体;">在</span><span lang="EN-US">Erlang</span><span style="font-family: 宋体;">的函数中，某些语法中，我们可以使用</span><span lang="EN-US">Pattern</span><span style="font-family: 宋体;">匹配，这是一个非常好的特性，我们可以让代码自己去决定如何执行</span> <span style="font-family: 宋体;">：</span></p> <p class="MsoNormal" style="line-height: 150%;"><span style="font-family: 宋体;">比如，我们定义一个函数，其告诉我们某种水果的价格</span><span lang="EN-US">:</span></p> <p class="MsoNormal" style="line-height: 150%;"><span lang="EN-US">price(apple) -> 2.0;</span></p> <p class="MsoNormal" style="line-height: 150%;"><span lang="EN-US">price(banana) -> 1.2.</span></p> <p class="MsoNormal" style="line-height: 150%;"><span style="font-family: 宋体;">我们随后调用</span><span lang="EN-US"> price(Fruit)</span><span style="font-family: 宋体;">，会根据</span><span lang="EN-US">Fruit</span><span style="font-family: 宋体;">变量的内容返回具体的价格。这样做的好处就是节省了我们的代码量，我们不用</span><span lang="EN-US">if...else…</span><span style="font-family: 宋体;">或者</span><span lang="EN-US">switch…case</span><span style="font-family: 宋体;">的来伺候了。也便于代码的扩展：加一个新的水果品种，我们只需要加一行就可以了。</span></p> <p class="MsoNormal" style="text-indent: 21pt; line-height: 150%;"><span style="font-family: 宋体;">学习</span><span lang="EN-US">Erlang</span><span style="font-family: 宋体;">一个非常重要的内容就是模式匹配，但是请不要混淆，这个匹配和正则表达式没有任何干系。</span></p> <h3 style="line-height: 150%;"> <span lang="EN-US">3.</span><span style="font-family: 宋体;">变量单次赋值</span> </h3> <p class="MsoNormal" style="text-indent: 21pt; line-height: 150%;"><span style="font-family: 宋体;">这个是一个匪夷所思的特性，变量竟然只能单次赋值！是的</span><span lang="EN-US">Erlang</span><span style="font-family: 宋体;">中变量一旦绑定某个数值以后，就不能再次绑定，这样做的好处是便于调试出错（更深层次的原因是</span><span lang="EN-US">Erlang</span><span style="font-family: 宋体;">为并发设计，如果变量可以修改，那么就涉及到资源的加锁解锁等问题），当发生错误时，某个变量是什么就永远是什么，不用顺藤摸瓜的查找谁修改过它，省了好多事情。唯一的麻烦就是需要一个信的变量时，你必须再为它想一个名字。</span></p> <h3 style="line-height: 150%;"> <span lang="EN-US">4.</span><span style="font-family: 宋体;">丰富的</span><span lang="EN-US">libs</span> </h3> <p class="MsoNormal" style="text-indent: 21pt; line-height: 150%;"><span lang="EN-US">Erlang</span><span style="font-family: 宋体;">中提供丰富的</span><span lang="EN-US">libs</span></p> <p class="MsoNormal" style="line-height: 150%;"><span lang="EN-US">stdlib</span><span style="font-family: 宋体;">中包含大量的数据结构如</span><span lang="EN-US">lists</span><span style="font-family: 宋体;">，</span><span lang="EN-US">array</span><span style="font-family: 宋体;">，</span><span lang="EN-US">dict</span><span style="font-family: 宋体;">，</span><span lang="EN-US">gb_sets</span><span style="font-family: 宋体;">，</span><span lang="EN-US">gb_trees</span><span style="font-family: 宋体;">，</span><span lang="EN-US">ets</span><span style="font-family: 宋体;">，</span><span lang="EN-US">dets</span><span style="font-family: 宋体;">等</span></p> <p class="MsoNormal" style="line-height: 150%;"><span lang="EN-US">mnesia</span><span style="font-family: 宋体;">提供一个分布式的数据库系统</span></p> <p class="MsoNormal" style="line-height: 150%;"><span lang="EN-US">inets</span><span style="font-family: 宋体;">提供</span><span lang="EN-US">ftp client</span><span style="font-family: 宋体;">，</span><span lang="EN-US">http client/server</span><span style="font-family: 宋体;">，</span><span lang="EN-US">tftp client/server</span></p> <p class="MsoNormal" style="line-height: 150%;"><span lang="EN-US">crypto </span><span style="font-family: 宋体;">提供加密解密相关函数，基于</span><span lang="EN-US">openssl</span><span style="font-family: 宋体;">相关实现</span></p> <p class="MsoNormal" style="line-height: 150%;"><span lang="EN-US">ssl </span><span style="font-family: 宋体;">实现加密</span><span lang="EN-US">socket</span><span style="font-family: 宋体;">通信，基于</span><span lang="EN-US">openssl</span><span style="font-family: 宋体;">实现</span></p> <p class="MsoNormal" style="line-height: 150%;"><span lang="EN-US">ssh </span><span style="font-family: 宋体;">实现</span><span lang="EN-US">ssh</span><span style="font-family: 宋体;">协议</span></p> <p class="MsoNormal" style="line-height: 150%;"><span lang="EN-US">xmerl </span><span style="font-family: 宋体;">实现</span><span lang="EN-US">XML</span><span style="font-family: 宋体;">相关解析</span></p> <p class="MsoNormal" style="line-height: 150%;"><span lang="EN-US">snmp </span><span style="font-family: 宋体;">实现</span><span lang="EN-US">SNMP</span><span style="font-family: 宋体;">协议（</span><span lang="EN-US">Simple Network Management Protocol</span><span style="font-family: 宋体;">）</span></p> <p class="MsoNormal" style="line-height: 150%;"><span lang="EN-US">observer </span><span style="font-family: 宋体;">用来分析与追踪分布式应用</span></p> <p class="MsoNormal" style="line-height: 150%;"><span lang="EN-US">odbc </span><span style="font-family: 宋体;">使</span><span lang="EN-US">Erlang</span><span style="font-family: 宋体;">可以连接基于</span><span lang="EN-US">SQL</span><span style="font-family: 宋体;">的数据库</span></p> <p class="MsoNormal" style="line-height: 150%;"><span lang="EN-US">orber </span><span style="font-family: 宋体;">实现</span><span lang="EN-US">CORBA</span><span style="font-family: 宋体;">对象请求代理服务</span></p> <p class="MsoNormal" style="line-height: 150%;"><span lang="EN-US">os_mon </span><span style="font-family: 宋体;">提供对操作系统的监控功能</span></p> <p class="MsoNormal" style="line-height: 150%;"><span lang="EN-US">dialyzer</span><span style="font-family: 宋体;">提供一个静态的代码或程序分析工具</span></p> <p class="MsoNormal" style="line-height: 150%;"><span lang="EN-US">edoc </span><span style="font-family: 宋体;">依据源文件生成文档</span></p> <p class="MsoNormal" style="line-height: 150%;"><span lang="EN-US">gs </span><span style="font-family: 宋体;">可以为我们提供某些</span><span lang="EN-US">GUI</span><span style="font-family: 宋体;">的功能（基于</span><span lang="EN-US">Tcl/Tk</span><span style="font-family: 宋体;">）</span></p> <p class="MsoNormal" style="line-height: 150%;"><span lang="EN-US">…</span></p> <p class="MsoNormal" style="line-height: 150%;"><span style="font-family: 宋体;">还有很多朋友提供了一些开源的</span><span lang="EN-US">lib</span><span style="font-family: 宋体;">，比如</span><span lang="EN-US">eunit</span><span style="font-family: 宋体;">，用来进行单元测试。</span></p> <h3 style="line-height: 150%;"> <span lang="EN-US">5.</span><span style="font-family: 宋体;">灵活多样的错误处理</span> </h3> <p class="MsoNormal" style="text-indent: 21pt; line-height: 150%;"><span lang="EN-US">Erlang</span><span style="font-family: 宋体;">最初为电信产品的开发，这样的目的，决定了其对错误处理的严格要求。</span><span lang="EN-US">Erlang</span><span style="font-family: 宋体;">中提供一般语言所提供的</span><span lang="EN-US">exception</span><span style="font-family: 宋体;">，</span><span lang="EN-US">catch</span><span style="font-family: 宋体;">，</span><span lang="EN-US">try…catch</span><span style="font-family: 宋体;">等语法，同时</span><span lang="EN-US">Erlang</span><span style="font-family: 宋体;">支持</span><span lang="EN-US">Link</span><span style="font-family: 宋体;">和</span><span lang="EN-US">Monitor</span><span style="font-family: 宋体;">两种机制，我们可以将</span><span lang="EN-US">Process</span><span style="font-family: 宋体;">连接起来，让他们组成一个整体，某个</span><span lang="EN-US">Process</span><span style="font-family: 宋体;">出错，或推出时，其他</span><span lang="EN-US">Process</span><span style="font-family: 宋体;">都具有得知其推出的能力。而</span><span lang="EN-US">Monitor</span><span style="font-family: 宋体;">顾名思义，可以用来监控某个</span><span lang="EN-US">Process</span><span style="font-family: 宋体;">，判断其是否退出或出错。所有的这些</span><span lang="EN-US">Erlang</span><span style="font-family: 宋体;">都提供内在支持，我们快速的开发坚固的产品，不在是奢望。</span></p> <h3 style="line-height: 150%;"> <span lang="EN-US">6.</span><span style="font-family: 宋体;">代码热替换</span> </h3> <p class="MsoNormal" style="text-indent: 21pt; line-height: 150%;"><span style="font-family: 宋体;">你的产品想不间断的更新么？</span><span lang="EN-US">Erlang</span><span style="font-family: 宋体;">可以满足你这个需求，</span><span lang="EN-US">Erlang</span><span style="font-family: 宋体;">会在运行时自动将旧的模块进行替换。一切都静悄悄。</span></p> <h3 style="line-height: 150%;"> <span lang="EN-US">7.</span><span style="font-family: 宋体;">天生的分布式</span> </h3> <p class="MsoNormal" style="text-indent: 21pt; line-height: 150%;"><span lang="EN-US">Erlang</span><span style="font-family: 宋体;">天生适合分布式应用开发，其很多的</span><span lang="EN-US">BIF</span><span style="font-family: 宋体;">（内建函数，相</span><span lang="EN-US">API</span><span style="font-family: 宋体;">）都具有分布式版本，我们可以通过</span><span lang="EN-US">BIF</span><span style="font-family: 宋体;">在远程机器上创建</span><span lang="EN-US">Process</span><span style="font-family: 宋体;">，可以向远程机器上的某个</span><span lang="EN-US">Process</span><span style="font-family: 宋体;">发送消息。在分布式应用的开发中，我们可以像</span><span lang="EN-US">C</span><span style="font-family: 宋体;">、</span><span lang="EN-US">C</span><span style="font-family: 宋体;">＋＋，</span><span lang="EN-US">JAVA</span><span style="font-family: 宋体;">等语言一样，通过</span><span lang="EN-US">Socket</span><span style="font-family: 宋体;">进行通讯，也可以使用</span><span lang="EN-US">Erlang</span><span style="font-family: 宋体;">内嵌的基于</span><span lang="EN-US">Cookie</span><span style="font-family: 宋体;">的分布式架构，进行开发。当然也可以两者混合。分布式开发更加方便，快速。</span><span lang="EN-US">Erlang</span><span style="font-family: 宋体;">的</span><span lang="EN-US">Process</span><span style="font-family: 宋体;">的操作，</span><span lang="EN-US">Error</span><span style="font-family: 宋体;">的处理等都对支持分布式操作。</span></p> <h3 style="line-height: 150%;"> <span lang="EN-US">8.</span><span style="font-family: 宋体;">超强的并发性</span> </h3> <p class="MsoNormal" style="text-indent: 21pt; line-height: 150%;"><span style="font-family: 宋体;">由于采用其自身</span><span lang="EN-US">Process</span><span style="font-family: 宋体;">，而没有采用操作系统的进程和线程，我们可以创建大规模的并发处理，同时还简化了我们的编程复杂度。我们可以通过几十行代码实现一个并发的</span><span lang="EN-US">TCP</span><span style="font-family: 宋体;">服务器，这在其他语言中都想都不敢想！</span></p> <h3 style="line-height: 150%;"> <span lang="EN-US">9.</span><span style="font-family: 宋体;">多核支持</span> </h3> <p class="MsoNormal" style="text-indent: 21pt;"><span lang="EN-US">Erlang</span><span style="font-family: 宋体;">让您的应用支持多个处理器，您不需要为不同的硬件系统做不同的开发。采用</span><span lang="EN-US">Erlang</span><span style="font-family: 宋体;">将最大限度的发挥你的机器性能。</span></p> <h3 style="line-height: 150%;"> <span lang="EN-US">10.</span><span style="font-family: 宋体;">跨平台</span> </h3> <p class="MsoNormal" style="text-indent: 21pt; line-height: 150%;"><span style="font-family: 宋体;">如同</span><span lang="EN-US">JAVA</span><span style="font-family: 宋体;">一样，</span><span lang="EN-US">Erlang</span><span style="font-family: 宋体;">支持跨平台（其目前支持</span><span lang="EN-US">linux</span><span style="font-family: 宋体;">，</span><span lang="EN-US">mac</span><span style="font-family: 宋体;">，</span><span lang="EN-US">windows</span><span style="font-family: 宋体;">等</span><span lang="EN-US">19</span><span style="font-family: 宋体;">种平台），不用为代码的移植而头疼。</span></p> <p class="MsoNormal" style="line-height: 150%;"><span style="font-family: 宋体;">我们仅仅需要了解平台的一些特性，对运行时进行优化。</span></p> <h3 style="line-height: 150%;"> <span lang="EN-US">11.</span><span style="font-family: 宋体;">开源</span> </h3> <p class="MsoNormal" style="text-indent: 21pt; line-height: 150%;"><span style="font-family: 宋体;">开源是我非常喜欢的一个词汇，开源意味这更加强壮，更加公开，更加的追求平等。开源会让</span><span lang="EN-US">Erlang</span><span style="font-family: 宋体;">更好。</span></p> <h2 style="line-height: 150%;"> <span style="font-family: 黑体;">五、</span><span lang="EN-US">Erlang</span><span style="font-family: 黑体;">与外界的交互</span> </h2> <p class="MsoNormal" style="text-indent: 21pt; line-height: 150%;"><span lang="EN-US">Erlang</span><span style="font-family: 宋体;">可以与其他的语言进行交互，如</span><span lang="EN-US">C</span><span style="font-family: 宋体;">、</span><span lang="EN-US">C</span><span style="font-family: 宋体;">＋＋，</span><span lang="EN-US">Java</span><span style="font-family: 宋体;">。当然也有热心的朋友提供了与其他语言的交互，如果需要你也可以根据</span><span lang="EN-US">Erlang</span><span style="font-family: 宋体;">的数据格式，提供一个库，让</span><span lang="EN-US">Erang</span><span style="font-family: 宋体;">与您心爱的语言交互。</span></p> <p class="MsoNormal" style="text-indent: 21pt; line-height: 150%;"><span lang="EN-US">Erlang</span><span style="font-family: 宋体;">支持分布式开发，您可以创建一个</span><span lang="EN-US">C Node</span><span style="font-family: 宋体;">，其如同一个</span><span lang="EN-US">Erlang</span><span style="font-family: 宋体;">节点，前提是你遵照</span><span lang="EN-US">Erlang</span><span style="font-family: 宋体;">的规范。</span></p> <p class="MsoNormal" style="text-indent: 21pt; line-height: 150%;"><span style="font-family: 宋体;">当然最常用的交互还是再同一个</span><span lang="EN-US">Node</span><span style="font-family: 宋体;">上，比如我们要调用某个</span><span lang="EN-US">lib</span><span style="font-family: 宋体;">，调用一些系统提供的功能，这时候主要有两种方式：</span><span lang="EN-US">Port</span><span style="font-family: 宋体;">和嵌入式执行。</span></p> <p class="MsoNormal" style="text-indent: 21pt; line-height: 150%;"><span lang="EN-US">Port</span><span style="font-family: 宋体;">是</span><span lang="EN-US">Erlang</span><span style="font-family: 宋体;">最基本的与外界交互的方式，进行交互的双方通过编码，解码，将信息以字节流的方式进行传递。（具体这个通道的实现方式，根据操作系统的不同而不同，比如</span><span lang="EN-US">unix</span><span style="font-family: 宋体;">环境下，采用</span><span lang="EN-US">PIPE</span><span style="font-family: 宋体;">实现，理论上任何支持对应</span><span lang="EN-US">Port</span><span style="font-family: 宋体;">通道实现的语言都可以与</span><span lang="EN-US">Erlang</span><span style="font-family: 宋体;">进行交互）。</span><span lang="EN-US">Erlang</span><span style="font-family: 宋体;">为了方便</span><span lang="EN-US">C</span><span style="font-family: 宋体;">和</span><span lang="EN-US">JAVA</span><span style="font-family: 宋体;">程序员，提供了</span><span lang="EN-US">Erl_Interface</span><span style="font-family: 宋体;">和</span><span lang="EN-US">Jinterface</span><span style="font-family: 宋体;">。</span></p> <p class="MsoNormal" style="text-indent: 21pt; line-height: 150%;"><span style="font-family: 宋体;">采用</span><span lang="EN-US">Port</span><span style="font-family: 宋体;">，您的代码在</span><span lang="EN-US">Erlang</span><span style="font-family: 宋体;">的平台之外运行，其崩溃不会影响</span><span lang="EN-US">Erlang</span><span style="font-family: 宋体;">。</span></p> <p class="MsoNormal" style="line-height: 150%;"><span style="font-family: 宋体;">嵌入式执行，通过</span><span lang="EN-US">Erlang</span><span style="font-family: 宋体;">平台加载，因此这是非常危险的，如果您的程序崩溃，没有任何理由，</span><span lang="EN-US">Erlang</span><span style="font-family: 宋体;">也会崩溃。</span></p> <h2 style="line-height: 150%;"> <span style="font-family: 黑体;">六、</span><span lang="EN-US">Erlang</span><span style="font-family: 黑体;">应用场景</span> </h2> <p class="MsoNormal" style="line-height: 150%;"><span style="font-family: 宋体;">分布式产品，网络服务器，客户端，等各种应用环境。</span></p> <p class="MsoNormal" style="line-height: 150%;"><span lang="EN-US">Erlang</span><span style="font-family: 宋体;">也可以作为一种快速开发语言，进行原型开发。</span></p> <h2 style="line-height: 150%;"> <span style="font-family: 黑体;">七、</span><span lang="EN-US">Erlang</span><span style="font-family: 黑体;">的学习过程</span> </h2> <p class="MsoNormal" style="margin-left: 21pt; text-indent: -21pt; line-height: 150%;"><span style="" lang="EN-US"><span style="">1.<span style='font-family: "Times New Roman"; font-style: normal; font-variant: normal; font-weight: normal; font-size: 7pt; line-height: normal; font-size-adjust: none; font-stretch: normal;'> </span></span></span><span style="font-family: 宋体;">安装首先从</span><span lang="EN-US">Erlang</span><span style="font-family: 宋体;">官方网站，下载安装</span><span lang="EN-US">Erlang</span><span style="font-family: 宋体;">（</span><span lang="EN-US"><a href="http://www.erlang.org/download.html">http://www.erlang.org/download.html</a></span><span style="font-family: 宋体;">）</span></p> <p class="MsoNormal" style="line-height: 150%;"><span lang="EN-US">linux</span><span style="font-family: 宋体;">：获取源代码，根据说明编译；</span><span lang="EN-US">windows</span><span style="font-family: 宋体;">：直接安装</span></p> <p class="MsoNormal" style="margin-left: 21pt; text-indent: -21pt; line-height: 150%;"><span style="" lang="EN-US"><span style="">2.<span style='font-family: "Times New Roman"; font-style: normal; font-variant: normal; font-weight: normal; font-size: 7pt; line-height: normal; font-size-adjust: none; font-stretch: normal;'> </span></span></span><span style="font-family: 宋体;">认真阅读《</span><span lang="EN-US">programming erlang</span><span style="font-family: 宋体;">》（中文版图书已经问世），并不断动手练习书中的例程。</span></p> <p class="MsoNormal" style="margin-left: 21pt; text-indent: -21pt; line-height: 150%;"><span style="" lang="EN-US"><span style="">3.<span style='font-family: "Times New Roman"; font-style: normal; font-variant: normal; font-weight: normal; font-size: 7pt; line-height: normal; font-size-adjust: none; font-stretch: normal;'> </span></span></span><span style="font-family: 宋体;">遇到问题时，不要退却，坚持下去找到解决办法</span></p> <p class="MsoNormal" style="margin-left: 21pt; text-indent: -21pt; line-height: 150%;"><span style="" lang="EN-US"><span style="">4.<span style='font-family: "Times New Roman"; font-style: normal; font-variant: normal; font-weight: normal; font-size: 7pt; line-height: normal; font-size-adjust: none; font-stretch: normal;'> </span></span></span><span style="font-family: 宋体;">对语言熟悉时，浏览一些好的开源项目</span></p> <p class="MsoNormal" style="margin-left: 21pt; text-indent: -21pt; line-height: 150%;"><span style="" lang="EN-US"><span style="">5.<span style='font-family: "Times New Roman"; font-style: normal; font-variant: normal; font-weight: normal; font-size: 7pt; line-height: normal; font-size-adjust: none; font-stretch: normal;'> </span></span></span><span style="font-family: 宋体;">有信心时，开始动手做一个小项目</span></p> <p class="MsoNormal" style="margin-left: 21pt; text-indent: -21pt; line-height: 150%;"><span style="" lang="EN-US"><span style="">6.<span style='font-family: "Times New Roman"; font-style: normal; font-variant: normal; font-weight: normal; font-size: 7pt; line-height: normal; font-size-adjust: none; font-stretch: normal;'> </span></span></span><span style="font-family: 宋体;">不间断的与大家交流，共同提高</span></p> <p class="MsoNormal" style="line-height: 150%;"><span style="font-family: 宋体;">可能遇到的困难：</span></p> <p class="MsoNormal" style="margin-left: 21pt; text-indent: -21pt; line-height: 150%;"><span style="" lang="EN-US"><span style="">a)<span style='font-family: "Times New Roman"; font-style: normal; font-variant: normal; font-weight: normal; font-size: 7pt; line-height: normal; font-size-adjust: none; font-stretch: normal;'> </span></span></span><span style="font-family: 宋体;">对于语法的不适应？</span></p> <p class="MsoNormal" style="text-indent: 21pt; line-height: 150%;"><span style="font-family: 宋体;">坚持看下去，代码继续写下去，我相信</span><span lang="EN-US">1</span><span style="font-family: 宋体;">个月，你会喜欢上</span><span lang="EN-US">Erlang</span><span style="font-family: 宋体;">的语法</span></p> <p class="MsoNormal" style="margin-left: 21pt; text-indent: -21pt; line-height: 150%;"><span style="" lang="EN-US"><span style="">b)<span style='font-family: "Times New Roman"; font-style: normal; font-variant: normal; font-weight: normal; font-size: 7pt; line-height: normal; font-size-adjust: none; font-stretch: normal;'> </span></span></span><span style="font-family: 宋体;">有些数据类型不清楚？</span></p> <p class="MsoNormal" style="text-indent: 21pt; line-height: 150%;"><span style="font-family: 宋体;">认真看资料，或者询问朋友，比如我</span></p> <p class="MsoNormal" style="margin-left: 21pt; text-indent: -21pt; line-height: 150%;"><span style="" lang="EN-US"><span style="">c)<span style='font-family: "Times New Roman"; font-style: normal; font-variant: normal; font-weight: normal; font-size: 7pt; line-height: normal; font-size-adjust: none; font-stretch: normal;'> </span></span></span><span style="font-family: 宋体;">中文资料的缺乏？</span></p> <p class="MsoNormal" style="margin-left: 21pt; line-height: 150%;"><span lang="EN-US">Erlang</span><span style="font-family: 宋体;">中文的资料会越来越多，此外，</span><span lang="EN-US">Erlang</span><span style="font-family: 宋体;">的相关的英文资料也比较容易理解，还是那句话，别怕麻烦</span></p> <h2 style="line-height: 150%;"> <span style="font-family: 黑体;">八、</span><span lang="EN-US">Erlang</span><span style="font-family: 黑体;">开源项目</span> </h2> <p class="MsoNormal" style="margin-left: 18pt; text-align: left; line-height: 150%;" align="left"><span style="font-size: 12pt; line-height: 150%; font-family: 宋体;">排名不分先后<span lang="EN-US"><p></p></span></span></p> <ul type="disc"> <li class="MsoNormal" style="text-align: left; line-height: 150%;"> <span style="font-size: 12pt; line-height: 150%; font-family: 宋体;" lang="EN-US"><a href="http://incubator.apache.org/couchdb/">couchdb</a> <span style=""> </span></span><span style="font-size: 12pt; line-height: 150%; font-family: 宋体;">基于文档等非结构化数据的数据库，提供<span lang="EN-US">HTTP</span>接口<span lang="EN-US"><p></p></span></span> </li> <li class="MsoNormal" style="text-align: left; line-height: 150%;"> <span style="font-size: 12pt; line-height: 150%; font-family: 宋体;" lang="EN-US"><a href="http://discoproject.org/">disco</a> <span style=""> </span>Map-Reduce</span><span style="font-size: 12pt; line-height: 150%; font-family: 宋体;">框架，<span lang="EN-US">Erlang + Python<p></p></span></span> </li> <li class="MsoNormal" style="text-align: left; line-height: 150%;"> <span style="font-size: 12pt; line-height: 150%; font-family: 宋体;" lang="EN-US"><a href="http://www.process-one.net/en/ejabberd/">ejabberd</a> <span style=""> </span></span><span style="font-size: 12pt; line-height: 150%; font-family: 宋体;">性能出众，使用广泛的<span lang="EN-US">Jabber</span>开源服务器<span lang="EN-US"><p></p></span></span> </li> <li class="MsoNormal" style="text-align: left; line-height: 150%;"> <span style="font-size: 12pt; line-height: 150%; font-family: 宋体;" lang="EN-US"><a href="http://mochiweb.googlecode.com/">mochiweb</a> <span style=""> </span></span><span style="font-size: 12pt; line-height: 150%; font-family: 宋体;">轻便，高效的<span lang="EN-US">HTTP</span>应用框架<span lang="EN-US"><p></p></span></span> </li> <li class="MsoNormal" style="text-align: left; line-height: 150%;"> <span style="font-size: 12pt; line-height: 150%; font-family: 宋体;" lang="EN-US"><a href="http://www.rabbitmq.com/">rabbitmq</a> <span style=""> </span></span><span style="font-size: 12pt; line-height: 150%; font-family: 宋体;">中间服务器，实现<span lang="EN-US">AMQP</span>协议<span lang="EN-US"><p></p></span></span> </li> <li class="MsoNormal" style="text-align: left; line-height: 150%;"> <span style="font-size: 12pt; line-height: 150%; font-family: 宋体;" lang="EN-US"><a href="http://yaws.hyber.org/">yaws</a> <span style=""> </span></span><span style="font-size: 12pt; line-height: 150%; font-family: 宋体;">高效的<span lang="EN-US">web server<p></p></span></span> </li> <li class="MsoNormal" style="text-align: left; line-height: 150%;"> <span style="font-size: 12pt; line-height: 150%; font-family: 宋体;" lang="EN-US"><a href="http://code.google.com/p/etorrent/">etorrent</a> <span style=""> </span>Bittorrent</span><span style="font-size: 12pt; line-height: 150%; font-family: 宋体;">客户端</span> </li> <li class="MsoNormal" style="text-align: left; line-height: 150%;"> <span class="MsoHyperlink"><span style="font-size: 12pt; line-height: 150%; font-family: 宋体;" lang="EN-US"><a href="http://code.google.com/p/scalaris/">scalaris</a></span></span><span lang="EN-US"> <span style=""> </span></span><span style="font-size: 12pt; line-height: 150%; font-family: 宋体;">分布式的<span lang="EN-US">key-value</span>存储</span> </li> </ul> <h2 style="line-height: 150%;"><span style="font-family: 黑体;">九、遇到问题</span></h2> <p class="MsoNormal" style="line-height: 150%;"><span style="font-family: 宋体;">参看</span><span lang="EN-US">Erlang</span><span style="font-family: 宋体;">官方文档</span> <span lang="EN-US"><a href="http://www.erlang.org/doc/">http://www.erlang.org/doc/</a> </span></p> <p class="MsoNormal" style="line-height: 150%;"><span style="font-family: 宋体;">订阅</span><span lang="EN-US">Erlang</span><span style="font-family: 宋体;">的</span><span lang="EN-US">maillist</span><span style="font-family: 宋体;">（</span><span lang="EN-US"><a href="http://www.erlang.org/mailman/listinfo/erlang-questions">http://www.erlang.org/mailman/listinfo/erlang-questions</a></span><span style="font-family: 宋体;">），进行提问</span></p> <p class="MsoNormal" style="line-height: 150%;"><span style="font-family: 宋体;">在</span><span lang="EN-US">Nabble</span><span style="font-family: 宋体;">提供的</span><span lang="EN-US">Erlang maillist</span><span style="font-family: 宋体;">存档中搜索（</span><span lang="EN-US"><a href="http://www.nabble.com/Erlang-f14095.html">http://www.nabble.com/Erlang-f14095.html</a></span><span style="font-family: 宋体;">）</span></p> <p class="MsoNormal" style="line-height: 150%;"><span lang="EN-US">Google</span><span style="font-family: 宋体;">中搜索答案</span></p> <h2 style="line-height: 150%;"><span style="font-family: 黑体;">十、推荐阅读</span></h2> <p class="MsoNormal" style="line-height: 150%;"><span lang="EN-US">Erlang Design Principles </span><span style="font-family: 宋体;">（</span><span lang="EN-US"><a href="http://www.erlang.org/doc/design_principles/part_frame.html">http://www.erlang.org/doc/design_principles/part_frame.html</a></span><span style="font-family: 宋体;">）</span></p> <p class="MsoNormal" style="line-height: 150%;"><span lang="EN-US">Erlang Efficiency Guide </span><span style="font-family: 宋体;">（</span><span lang="EN-US"><a href="http://www.erlang.org/doc/efficiency_guide/part_frame.html">http://www.erlang.org/doc/efficiency_guide/part_frame.html</a></span><span style="font-family: 宋体;">）</span></p> <p class="MsoNormal" style="line-height: 150%;"><span lang="EN-US">Erlang Programming Rules </span><span style="font-family: 宋体;">（</span><span lang="EN-US"><a href="http://www.erlang.se/doc/programming_rules.shtml">http://www.erlang.se/doc/programming_rules.shtml</a></span><span style="font-family: 宋体;">）</span></p> <h2 style="line-height: 150%;"><span style="font-family: 黑体;">十一、推荐网站</span></h2> <p class="MsoNormal" style="line-height: 150%;"><span lang="EN-US"><a href="http://www.erlang.org/">http://www.erlang.org</a> </span></p> <p class="MsoNormal" style="line-height: 150%;"><span lang="EN-US"><a href="http://erlang-china.org/">http://erlang-china.org</a></span></p> <p class="MsoNormal" style="line-height: 150%;"><span lang="EN-US"><a href="http://trapexit.org/">http://trapexit.org</a> </span><span style="font-family: 宋体;">（国内封锁，可以使用</span><span lang="EN-US"><a href="http://trapexit.org.nyud.net:8080/">http://trapexit.org.nyud.net:8080/</a> </span><span style="font-family: 宋体;">或其他代理登录）</span></p> <p class="MsoNormal" style="line-height: 150%;"><span lang="EN-US"><a href="http://toquick.com/">http://toquick.com</a> </span></p> <p class="MsoNormal" style="line-height: 150%;"><span lang="EN-US"><a href="http://blog.socklabs.com/">http://blog.socklabs.com/</a> </span></p> <p class="MsoNormal" style="line-height: 150%;"><span lang="EN-US"><a href="http://www.planeterlang.org/">http://www.planeterlang.org/</a></span></p></defjc></rmargin></lmargin></dispdef></smallfrac>

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