Install camlp4 by entering the following commands in the terminal:
sudo apt update sudo apt install camlp4
Pre Processor Pretty Printer for OCaml
Camlp4 is a software 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. . This package contains CamlP4 executables for pre-processing and pretty-printing OCaml sources both interactively and in a batch fashion.