编程之道--Book Three - Design

摘自《编程之道》

将此书献给那些爱笑也爱思考的程序设计者,以及那些同程序设计者打交道的管理人员,当然他们也爱笑爱思考。 

编程之道--Book Three - Design

Thus spake the master programmer:

编程大师如是说:

"When program is being tested, it is too late to make design changes."

“程序被测试时再去改变它的设计已经太晚了。”

3.1

There once was a man who went to a computer trade show. Each day as heentered, the man told the guard at the door:

曾经有一个人参加计算机展览,每天他进门时都对门卫说:
"I am a great thief, renowned for my feats of shoplifting. Be forewarned,for this trade show shall not escape unplundered."

“先警告你,我是偷盗高手,我入室偷盗的本领闻名遐迩。这次展览会也再劫难逃。”

This speech disturbed the guard greatly, because there were millions ofdollars of computer equipment inside, so he watched the man carefully.But the man merely wandered from booth to booth, humming quietly tohimself.

警卫因此大动干戈,因为里面有价值百万的计算机设备,所以他牢牢盯紧了这个人,但是这个人只是从一个摊位逛到另一个摊位,一边平静地喃喃自语。

When the man left, the guard took him aside and searched his clothes, butnothing was to be found.

当这个人离开时,警卫搜了他的身,但是什么也没有发现。

On the next day of the trade show, the man returned and chided the guardsaying: "I escaped with a vast booty yesterday, but today will be evenbetter." So the guard watched him ever more closely, but to no avail.

展览会的第二天,这个人又对警卫说:“昨天我满载而归,但是今天我会收获更大。”所以警卫更加小心地盯紧他,但是这样做完全于事无补。

On the final day of the trade show, the guard could restrain his curiosityno longer. "Sir Thief," he said, "I am so perplexed, I cannot live in peace.Please enlighten me. What is it that you are stealing?"

展览会的最后一天,警卫再也不能忍住他的好奇心了。“小偷先生,”他说,“ 你说我惊慌不安,请告诉我,你到底偷了什么?”。

The man smiled. "I am stealing ideas," he said.

这个人笑笑说:“我在偷想法。” 

3.2

There once was a master programmer who wrote unstructured programs. Anovice programmer, seeking to imitate him, also began to writeunstructured programs. When the novice asked the master to evaluate hisprogress, the master criticized him for writing unstructured programs,saying: "What is appropriate for the master is not appropriate for thenovice. You must understand the Tao before transcending structure."

有一位编程大师,他写非结构化的程序,一位初学者刻意模仿他,也写非结构化的程序。当他让大师看他的进步时,大师批评了他的非结构化程序:“ 对一位编程大师合适的东西未必对一个初学者同样合适,在超越结构化之前,你必须理解编程之道。”

3.3

There was once a programmer who was attached to the court of the warlordof Wu. The warlord asked the programmer: "Which is easier to design: anaccounting package or an operating system?"

有人问一位程序员,“一个财务软件和一个操作系统哪个更容易设计?”

"An operating system," replied the programmer.

“是操作系统”,这位程序员回答说。

The warlord uttered an exclamation of disbelief. "Surely an accountingpackage is trivial next to the complexity of an operating system," he said.

此人大惑不解。他说:“显然一个财务软件比起操作系统来说其复杂性是微不足道的”。

"Not so," said the programmer, "when designing an accounting package, theprogrammer operates as a mediator between people having different ideas:how it must operate, how its reports must appear, and how it must conformto the tax laws. By contrast, an operating system is not limited my outsideappearances. When designing an operating system, the programmer seeks thesimplest harmony between machine and ideas. This is why an operatingsystem is easier to design."

程序员说:“不,设计财务软件时,一个程序员必须成为持不同意见的用户与计算机的一个中介,他必须了解用户的操作习惯,报表要是什么形式,如何遵循税法。相反,一个操作系统完全与这些外部的东西无关。设计操作系统,程序员只需要达到自己的设想与机器之间的简单的和谐。这就是为什么操作系统反而比财务软件更容易设计。” 

The warlord of Wu nodded and smiled. "That is all good and well, but whichis easier to debug?"

这些人笑着说。“不错,但是哪一个更容易调试呢?”

The programmer made no reply.
程序员没有回答。

3.4

A manager went to the master programmer and showed him the requirementsdocument for a new application. The manager asked the master: "How longwill it take to design this system if I assign five programmers to it?"

一个项目经理带给编程大师一个项目的需求,然后问大师:“如果我给你 5 个程序员,要多少时间设计这个项目?”

"It will take one year," said the master promptly.

“一年”,大师说。

"But we need this system immediately or even sooner! How long will it takeit I assign ten programmers to it?"

“但是我们等不了那么长时间,越快越好,如果 10 程序员呢?”

The master programmer frowned. "In that case, it will take two years."

大师皱了一下眉头说:“那就要花 2 年”。

"And what if I assign a hundred programmers to it?"

“那,100 名程序员呢?”

The master programmer shrugged. "Then the design will never be completed,"he said.

大师耸了耸肩说:“那这个项目就永远完不成了。”