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 righteous, because it tries to fix some small problems of the normal syntax. Camlp4 can pretty print the normal Ocaml concrete syntax or the righteous one. It is therefore always possible to have a version of your sources compilable by the compiler Objective Caml without preprocessing.