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The Art of Unix Programming
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Unix Programming - Chapter16.Reuse

When the superior man refrains from acting, his force is felt for a thousand miles.

-- Tao Te Ching (as popularly mistranslated)

Reluctance to do unnecessary work is a great virtue in programmers. If the Chinese sage Lao-Tze were alive today and still teaching the way of the Tao, he would probably be mistranslated as: When the superior programmer refrains from coding, his force is felt for a thousand miles. In fact, recent translators have suggested that the Chinese term wu-wei that has traditionally been rendered as “inaction” or “refraining from action” should probably be read as “least action” or “most efficient action” or “action in accordance with natural law”, which is an even better description of good engineering practice!

Remember the Rule of Economy. Re-inventing fire and the wheel for every new project is terribly wasteful. Thinking time is precious and very valuable relative to all the other inputs that go into software development; accordingly, it should be spent solving new problems rather than rehashing old ones for which known solutions already exist. This attitude gives the best return both in the “soft” terms of developing human capital and in the “hard” terms of economic return on development investment.

Reinventing the wheel is bad not only because it wastes time, but because reinvented wheels are often square. There is an almost irresistible temptation to economize on reinvention time by taking a shortcut to a crude and poorly-thought-out version, which in the long run often turns out to be false economy.

-- Henry Spencer

The most effective way to avoid reinventing the wheel is to borrow someone else's design and implementation of it. In other words, to reuse code.

Unix supports reuse at every level from individual library modules up to entire programs, which Unix helps you script and recombine. Systematic reuse is one of the most important distinguishing behaviors of Unix programmers, and the experience of using Unix should teach you a habit of trying to prototype solutions by combining existing components with a minimum of new invention, rather than rushing to write standalone code that will only be used once.

The virtuousness of code reuse is one of the great apple-pie-and-motherhood verities of software development. But many developers entering the Unix community from a basis of experience in other operating systems have never learned (or have unlearned) the habit of systematic reuse. Waste and duplicative work is rife, even though it seems to be against the interests both of those who pay for code and those who produce it. Understanding why such dysfunctional behavior persists is the first step toward changing it.

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The Art of Unix Programming
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