The ppxlib project provides the basis for the ppx system, which is
 currently the officially supported method for meta-programming in
 OCaml. It offers a principled way to generate code at compile time in
 OCaml projects. It features:
  * OCaml AST / parser / pretty-printer snapshot, to create a full
    frontend independent of the version of OCaml;
  * library for ppx rewriters in general, and type-driven code
    generators in particular;
  * feature-full driver for OCaml AST transformers;
  * quotation mechanism allowing to write values representing the
    OCaml AST in the OCaml syntax;
  * generator of open recursion classes from type definitions.