[pro] The Best Examples of "Code is Data"

[Kazimir Majorinc]

As first, good luck with this list!

I'm in search for best examples of "code is data" paradigm in Common
Lisp. For most CL-ers, it probably means "macros", but eval, backquote,
anything that processes the code as data is of interest. As "best" I
think on the most surprising, powerful, sophisticated examples, not
necessarily of a pedagogical value.

Imagine that someone invited you to write the presentation "Five best CL
macros ... I seen" or "Five best CL macros ... I wrote." What would you
chose and why?

Kazimir Majorinc