[sklogic]

ML got ADTs and pattern matching out of the box. Fine. With Lisp you can quickly build your own ADTs, with some enhanced functionality which is not possible in *ML family.

See a couple of examples of this:

[1] http://www.cs.indiana.edu/~dyb/pubs/nano-jfp.pdf

[2] https://github.com/combinatorylogic/mbase

[Peaker]

> > When changing the AST, how would you go about changing all the code that needs to be changed?

Is there an answer to this question?

[sklogic]

Have you seen Nanopass or MBase? They address this very question.