Examples of what Lisp's macros can be used for

Question

I\'ve heard that Lisp\'s macro system is very powerful. However, I find it difficult to find some practical examples of what they can be used for; things that would be diffi

Answer 1

Besides extending the language's syntax to allow you to express yourself more clearly, it also gives you control over evaluation. Try writing your own if in your language of choice so that you can actually write my_if something my_then print "success" my_else print "failure" and not have both print statements get evaluated. In any strict language without a sufficiently powerful macro system, this is impossible. No Common Lisp programmers would find the task too challenging, though. Ditto for for-loops, foreach loops, etc. You can't express these things in C because they require special evaluation semantics (people actually tried to introduce foreach into Objective-C, but it didn't work well), but they are almost trivial in Common Lisp because of its macros.