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by dlweinreb
6473 days ago
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I disagree about that. It's very, very hard to add Lisp-style macros to something like C or Java. The best attempt to do it for Java is Jonathan Bachrach's Java Syntactic Extender, but as far as I know nobody has built any software with it. It's just too hard to use. Until you have read a clear description (e.g. Seibel) or had some experience, it's hard to see what macros are really all about. Lisp macros are extremely important, powerful, and beneficial. Space does not permit me to go into the full explanation; see Peter Siebel's book and the great lecture he gave at Google, available on the web. Macros allowed us to add object-oriented programming to Common Lisp. CLOS (the Common Lisp Object System) fits in very smoothly into the Common Lisp language, with a nice, clear syntax and very powerful semantics. At work, we have built an object-relational mapping system that, similarly, would be impractical (ugly and verbose to the point of unusability) without macros. |
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Yes, it is extremely hard to add lisp-style macros to C or Java because they have no s-expression structure you can work on. And they do not want an s-expression structure because it is too alien for those programmers. Thus, they perceive that macros are not worth the effort.
I think macros are left out of so many languages because people do not know how to incorporate them while retaining other desirable properties of the language (type safety for instance).
Also, macros are not the only way to build ORM systems. Python does the same with metaclassing as an example. But we can agree on that trying to map it into a statically typed language with reflection/AOP as Java did is doomed to fail I think ;)
I am not trying to say that macros are useless. I am trying to say that some languages leave them out on purpose. Many problems on which macros look nice can be solved with a little extra thought on representation. But then again, many can not.
I see the discussion of macros/no-macros a bit like the discussion on static/dynamic typing. With static typing, we know we are leaving some valid programs outside the gates of the static world. But we think that this loss is negligible compared to the benefits a static check gives us. Yet, some people oppose this viewpoint and wants the valid programs as well, because they perceive the benefits of the static typing to the negligible. Both approaches are valid, but it currently looks like it is hard to get all of the cake in one munch.