[saywatnow]

> imagine Lisp without macros.

Early on in my Scheme career, I found the tools to create macros a bit confusing and arcane .. but I still knew I wanted macros.

I ended up writing code transformers - a poor man's macro system if you will, taking my "high level" foo.scm through a couple of translation layers that turned the abstractions I wanted into running code. It was literally:

  $ scheme expand-foo.scm < myprog.scm > myprog1.scm
  $ scheme expand-bar.scm < myprog1.scm > myprog2.scm
  $ scheme myprog2.scm

What made this possible - trivial - was the homoiconicity: simply by (read)ing a program from stdin I had a list of lists that I could pattern match over and make the transformations I wanted. Exactly as my final program did with ordinary data.

In some ways, this was a more satisfying approach than using define-syntax / syntax-case, which differ from the rest of Scheme in somewhat uncomfortable ways. That macros could never be first class eventually put me off, but that's another story :).