动态语言也称为脚本语言,是介于标签语言(如HTML,XSLT,VML)和静态语言(如C++、C#、Java,也称编译语言)之间的语言。JavaScript、PHP、Perl、Ruby等都是动态语言。动态语言无需编译,它由解释器动态解释执行,一般来说,动态语言拥有比静态语言更大的灵活性和表达能力。动态语言优势在于灵活,易于开发和学习,劣势在于性能较低。在高性能服务器和并行处理的实现方案里,动态语言的优势掩盖自身的不足。一般来说,完成同样逻辑功能的程序,使用Ruby或Python之类的动态语言所需的代码量往往只有使用Java实现版本的1/10,相比C/C++差距更大。近两年来,动态语言似乎有山雨欲来风满楼的气势。在各大开发技术网站,有大量介绍动态语言的文章,在各大论坛里,人们针对动态语言的学习、交流、论战、预测的帖子不断成为抢眼热帖,搅动着开发者的神经。动态语言最突出的特性是语法简洁灵活,易于学习,拥有大量高级程序库,无须从底层开始搭建程序,降低了应用实现的难度。一个C++程序员,往往经过了几年的训练仍然不能开发出可用的程序,但动态语言的程序员经过几个月的训练就已经可以编写出可复用性的代码了。此外,动态语言的代码往往以开源的形式发布,容易被使用和学习。程序库往往决定了一种语言应用难度,纵观历史,凡是具有优秀程序库的语言生命力都很顽强,反之则容易销声匿迹。目前几种流行的动态语言,都具有丰富的程序库,在Python中,不仅具有诸如网络应用,多线程,图像处理,科学运算之类的程序库,甚至还拥有多套不同量级的Framework来辅助Web开发。事实上,任何需要的功能几乎都能找到相对稳定的程序库,大部分程序员仅仅需要组合这些库就能编写出强大的应用——这也正是使用动态语言开发程序代码量较少的原因之一。除了众多的程序库,动态语言本身的种类也远远大于静态语言,同样,每种语言也各具特点。Ruby,Python,Groovy,Perl是四种颇具代表性的动态语言,按照一般的看法,这些语言适合用来黏合不同的系统和模块,素有“胶水”的之称。后来人们发现“胶水”不仅仅能粘合其他模块,本身也具有强大的功能。在没有性能问题的重要性不突出的场合,动态语言看起来无所不能了,无论是网站还是应用程序,都能看到动态语言的身影。对时下的程序员来说,掌握一种动态语言已不仅仅是赶时髦,虽然你不一定能够靠单单一种动态语言找到一份喜欢的工作,但适时地采用动态语言,一定可以让你的工作变的简单许多。
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