Description:

Camlp4 is a Pre-Processor-Pretty-Printer for Objective Caml. It offers
tools for syntax (grammars) and the ability to modify the concrete
syntax of the language (quotations, syntax extensions).

Camlp4 can parse normal Ocaml concrete syntax or any other
user-definable syntax. As an example, an alternative syntax is
provided, named revised, because it tries to fix some small problems
of the normal syntax.

Camlp4 can pretty print the normal Ocaml concrete syntax or the
revised one. It is therefore always possible to have a version of your
sources compilable by the compiler Objective Caml without
preprocessing.