Library to help in writing OCaml PPX rewriters, which can be used to
extend the syntax of an OCaml programs. PPX rewriters are a powerfull
alternative to the older camlp4/campl5 technology, and they can also
be composed.

This PPX library provides facilities to, under other, work at the
level of the OCaml's abstract syntax tree (AST), write driver
front-ends for the OCaml compiler, parse an OCaml expression as an
AST, etc.