Книга: Practical Common Lisp

What's with All the Parentheses?

What's with All the Parentheses?

Lisp's syntax is quite a bit different from the syntax of languages descended from Algol. The two most immediately obvious characteristics are the extensive use of parentheses and prefix notation. For whatever reason, a lot of folks are put off by this syntax. Lisp's detractors tend to describe the syntax as "weird" and "annoying." Lisp, they say, must stand for Lots of Irritating Superfluous Parentheses. Lisp folks, on the other hand, tend to consider Lisp's syntax one of its great virtues. How is it that what's so off-putting to one group is a source of delight to another?

I can't really make the complete case for Lisp's syntax until I've explained Lisp's macros a bit more thoroughly, but I can start with an historical tidbit that suggests it may be worth keeping an open mind: when John McCarthy first invented Lisp, he intended to implement a more Algol-like syntax, which he called M-expressions. However, he never got around to it. He explained why not in his article "History of Lisp."[36]

The project of defining M-expressions precisely and compiling them or at least translating them into S-expressions was neither finalized nor explicitly abandoned. It just receded into the indefinite future, and a new generation of programmers appeared who preferred [S-expressions] to any FORTRAN-like or ALGOL-like notation that could be devised.

In other words, the people who have actually used Lisp over the past 45 years have liked the syntax and have found that it makes the language more powerful. In the next few chapters, you'll begin to see why.

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