[racket] Survey of Syntax and Hygienic Macro Systems?

> Me: AST level <=> s-expressions.

Not true.  S-expressions are one step removed from true abstract
syntax.  The conveyor of the former into the latter is parse.

> So here's my question: is there a good *survey* of syntax & hygienic
> macro systems that tries to provide some insight into what we've
> learned?   I don't think PLAI or 2nd edition EoPL try to do this.

PLAI could do better.  It doesn't approach this material in a very
comparative way.  Since I'm working on moving the rest of PLAI to be
more comparative as well, maybe this will follow more naturally.

Shriram