18.4. What You've Learned

This chapter covered macro programming. You’ve learned the following:

• Macros let you write code that writes code. With macros, you can create your own programming language and convert it to standard Lisp just before the compiler can get a peek at it.

• Macros allow you to get rid of that feeling of déjà vu when writing your code, in situations when nothing else can do so.

• You must be careful when writing macros so that they don’t lead to unintentional, repeated execution of code.

• You need to be careful to avoid unintended variable capture in macros. You can avoid this by using gensym names.

• If variables created by a macro are exposed on purpose, as a feature of the macro, the macro is called an anaphoric macro.

• Macro programming is a very powerful technique. However, try to use functional programming instead to solve a problem whenever possible. Macros should always be a last resort.