lisp的本质[0]

 Lisp的本质(The Nature of Lisp)

作者 Slava Akhmechet
        译者 Alec Jang
              出处: http://www.defmacro.org/ramblings/lisp.html

 

 

Introduction

简介

When I first stumbled into Lisp advocacy on various corners of the web I was already an experienced programmer. At that point I had grokked what seemed at the time a wide range of programming languages. I was proud to have the usual suspects (C++, Java, C#, etc.) on my service record and was under impression that I knew everything there is to know about programming languages. I couldn't have possibly been more wrong.
 
最初在web的某些角落偶然看到有人赞美Lisp时, 我那时已经是一个颇有经验的程序员。在我的履历上, 掌握的语言范围相当广泛, 象C++, Java, C#主流语言等等都不在话下,我觉得我差不多知道所有的有关编程语言的事情。对待编程语言的问题上, 我觉得自己不太会遇到什么大问题。其实我大错特错了。

My initial attempt to learn Lisp came to a crashing halt as soon as I saw some sample code. I suppose the same thought ran through my mind that ran through thousands of other minds who were ever in my shoes: "Why on Earth would anyone want to use a language with such horrific syntax?!" I couldn't be bothered to learn a language if its creators couldn't be bothered to give it a pleasant syntax. After all, I was almost blinded by the infamous Lisp parentheses!
 
我试着学了一下Lisp, 结果马上就撞了墙。我被那些范例代码吓坏了。我想很多初次接触Lisp语言的人, 一定也有过类似的感受。Lisp的语法太次了。一个语言的发明人, 居然不肯用心弄出一套漂亮的语法, 那谁还会愿意学它。反正, 我是确确实实被那些难看的无数的括号搞蒙了。

The moment I regained my sight I communicated my frustrations to some members of the Lisp sect. Almost immediately I was bombarded by a standard set of responses: Lisp's parentheses are only a superficial matter, Lisp has a huge benefit of code and data being expressed in the same manner (which, obviously, is a huge improvement over XML), Lisp has tremendously powerful metaprogramming facilities that allow programs to write code and modify themselves, Lisp allows for creation of mini-languages specific to the problem at hand, Lisp blurs the distinction between run time and compile time, Lisp, Lisp, Lisp... The list was very impressive. Needless to say none of it made sense. Nobody could illustrate the usefulness of these features with specific examples because these techniques are supposedly only useful in large software systems. After many hours of debating that conventional programming languages do the job just fine, I gave up. I wasn't about to invest months into learning a language with a terrible syntax in order to understand obscure features that had no useful examples. My time has not yet come.
 
回过神来之后, 我和Lisp社区的那伙人交谈, 诉说我的沮丧心情。结果, 立马就有一大套理论砸过来, 这套理论在Lisp社区处处可见, 几成惯例。比如说: Lisp的括号只是表面现象; Lisp的代码和数据的表达方式没有差别, 而且比XML语法高明许多, 所以有无穷的好处; Lisp有强大无比的元语言能力, 程序员可以写出自我维护的代码; Lisp可以创造出针对特定应用的语言子集; Lisp的运行时和编译时没有明确的分界; 等等, 等等, 等等。这么长的赞美词虽然看起来相当动人, 不过对我毫无意义。没人能给我演示这些东西是如何应用的, 因为这些东西一般来说只有在大型系统才会用到。我争辩说, 这些东西传统语言一样办得到。在和别人争论了数个小时之后, 我最终还是放弃了学Lisp的念头。为什么要花费几个月的时间学习语法这么难看的语言呢? 这种语言的概念这么晦涩, 又没什么好懂的例子。也许这语言不是该我这样的人学的。

For many months the Lisp advocates pressed on. I was baffled. Many extremely intelligent people I knew and had much respect for were praising Lisp with almost religious dedication. There had to be something there, something I couldn't afford not to get my hands on! Eventually my thirst for knowledge won me over. I took the plunge, bit the bullet, got my hands dirty, and began months of mind bending exercises. It was a journey on an endless lake of frustration. I turned my mind inside out, rinsed it, and put it back in place. I went through seven rings of hell and came back. And then I got it.
 
几个月来, 我承受着这些Lisp辩护士对我心灵的重压。我一度陷入了困惑。我认识一些绝顶聪明的人, 我对他们相当尊敬, 我看到他们对Lisp的赞美达到了宗教般的高度。这就是说, Lisp中一定有某种神秘的东西存在, 我不能忍受自己对此的无知, 好奇心和求知欲最终不可遏制。我于是咬紧牙关埋头学习Lisp, 经过几个月的时间费劲心力的练习, 终于,我看到了那无穷无尽的泉水的源头。在经过脱胎换骨的磨练之后, 在经过七重地狱的煎熬之后, 终于, 我明白了。

The enlightenment came instantaneously. One moment I understood nothing, and the next moment everything clicked into place. I've achieved nirvana. Dozens of times I heard Eric Raymond's statement quoted by different people: "Lisp is worth learning for the profound enlightenment experience you will have when you finally get it; that experience will make you a better programmer for the rest of your days, even if you never actually use Lisp itself a lot." I never understood this statement. I never believed it could be true. And finally, after all the pain, it made sense! There was more truth to it than I ever could have imagined. I've achieved an almost divine state of mind, an instantaneous enlightenment experience that turned my view of computer science on its head in less than a single second.
 
顿悟在突然之间来临。曾经许多次, 我听到别人引用雷蒙德(译者注: 论文<<大教堂和市集>>的作者, 著名的黑客社区理论家)的话: "Lisp语言值得学习。当你学会Lisp之后, 你会拥有深刻的体验。就算你平常并不用Lisp编程, 它也会使你成为更加优秀的程序员"。过去, 我根本不懂这些话的含义, 我也不相信这是真的。可是现在我懂得了。这些话蕴含的真理远远超过我过去的想像。我内心体会到一种神圣的情感, 一瞬间的顿悟, 几乎使我对电脑科学的观念发生了根本的改变。
 
That very second I became a member of the Lisp cult. I felt something a ninjitsu master must feel: I had to spread my newfound knowledge to at least ten lost souls in the course of my lifetime. I took the usual path. I was rehashing the same arguments that were given to me for years (only now they actually made sense!), hoping to convert unsuspecting bystanders. It didn't work. My persistence sparked a few people's interest but their curiosity dwindled at the mere sight of sample Lisp code. Perhaps years of advocacy would forge a few new Lispers, but I wasn't satisfied. There had to be a better way.

顿悟的那一刻, 我成了Lisp的崇拜者。我体验到了宗教大师的感受: 一定要把我的知识传布开来, 至少要让10个迷失的灵魂得到拯救。按照通常的办法, 我把这些道理(就是刚开始别人砸过来的那一套, 不过现在我明白了真实的含义)告诉旁人。结果太令人失望了,只有少数几个人在我坚持之下, 发生了一点兴趣, 但是仅仅看了几眼Lisp代码, 他们就退却了。照这样的办法, 也许费数年功夫能造就了几个Lisp迷, 但我觉得这样的结果太差强人意了, 我得想一套有更好的办法。

I gave the matter careful thought. Is there something inherently hard about Lisp that prevents very intelligent, experienced programmers from understanding it? No, there isn't. After all, I got it, and if I can do it, anybody can. Then what is it that makes Lisp so hard to understand? The answer, as such things usually do, came unexpectedly. Of course! Teaching anybody anything involves building advanced concepts on top of concepts they already understand! If the process is made interesting and the matter is explained properly the new concepts become as intuitive as the original building blocks that aided their understanding. That was the problem! Metaprogramming, code and data in one representation, self-modifying programs, domain specific mini-languages, none of the explanations for these concepts referenced familiar territory. How could I expect anyone to understand them! No wonder people wanted specific examples. I could as well have been speaking in Martian!
 
我深入地思考了这个问题。是不是Lisp有什么很艰深的东西, 令得那么多老练的程序员都不能领会? 不是, 没有任何绝对艰深的东西。因为我能弄懂, 我相信其他人也一定能。那么问题出在那里? 后来我终于找到了答案。我的结论就是, 凡是教人学高级概念, 一定要从他已经懂得的东西开始。如果学习过程很有趣, 学习的内容表达得很恰当, 新概念就会变得相当直观。这就是我的答案。所谓元编程, 所谓数据和代码形式合一, 所谓自修改代码, 所谓特定应用的子语言, 所有这些概念根本就是同族概念, 彼此互为解释, 肯定越讲越不明白。还是从实际的例子出发最有用。

I shared my ideas with fellow Lispers. "Well, of course these concepts aren't explained in terms of familiar territory", they said. "They are so different, they're unlike anything these people have learned before." This was a poor excuse. "I do not believe this to be true", I said. The response was unanimous: "Why don't you give it a try?" So I did. This article is a product of my efforts. It is my attempt to explain Lisp in familiar, intuitive concepts. I urge brave souls to read on. Grab your favorite drink. Take a deep breath. Prepare to be blown away. Oh, and may the Force be with you.

我把我的想法说给Lisp程序员听, 遭到了他们的反对。"这些东西本身当然不可能用熟悉的知识来解释, 这些概念完全与众不同, 你不可能在别人已有的经验里找到类似的东西",可是我认为这些都是遁词。他们又反问我, "你自己为啥不试一下?" 好吧, 我来试一下。这篇文章就是我尝试的结果。我要用熟悉的直观的方法来解释Lisp, 我希望有勇气的人读完它, 拿杯饮料, 深呼吸一下, 准备被搞得晕头转向。来吧, 愿你获得大能。