A comprehensive toolbox for ppx development. It features:
- a OCaml AST / parser / pretty-printer snapshot,to create a full
   frontend independent of the version of OCaml;
- a library for library for ppx rewriters in general, and type-driven
  code generators in particular;
- a feature-full driver for OCaml AST transformers;
- a quotation mechanism allowing  to write values representing the
   OCaml AST in the OCaml syntax;
- a generator of open recursion classes from type definitions.
