gistfile1.txt

$ opam info camlp4
             package: camlp4
             version: 4.03
          repository: default
              pinned: version
        upstream-url: git://github.com/ocaml/camlp4#trunk
       upstream-kind: git
            homepage: https://github.com/ocaml/camlp4
         bug-reports: https://github.com/ocaml/camlp4/issues
            dev-repo: https://github.com/ocaml/camlp4.git
             license: LGPLv2
             depends: ocamlfind
   installed-version:
  available-versions: 4.01, 4.01+system, 4.02+1, 4.02+2, 4.02+3, 4.02+4, 4.02+6, 4.02+system, 4.02.0-1modular-implicits, 4.03
         description: Camlp4 is a system for writing extensible parsers for programming languages

It provides a set of OCaml libraries that are used to define grammars as well
as loadable syntax extensions of such grammars. Camlp4 stands for Caml
Preprocessor and Pretty-Printer and one of its most important applications is
the definition of domain-specific extensions of the syntax of OCaml.

Camlp4 was part of the official OCaml distribution until its version 4.01.0.
Since then it has been replaced by a simpler system which is easier to maintain
and to learn: ppx rewriters and extension points.