I have a pretty good grasp on macros in Lisp, C/C++, TeX, m4, and nroff. Lisp macros are, far and away, the most powerful in that set. In fact, Lisp macros get a bad rap by sharing a name with macros in those other languages. Still, I often hit the same wall when trying to write a Lisp macro so I know that there’s more I have to learn.
A Quick Look at Macros
First, let’s review macros for a moment to make sure we’re all on the same page. The C/C++ macros are the simplest to understand so we’ll start there. The C and C++ compilers run in two stages. First, the C preprocessor runs to expand all of your macros. Then, the compiler runs to actually compile your code. In C and C++, macros are declared using the #define command to the preprocessor. For example, you might do something like the following:
Read the rest of this entry ⇒