Introduction

Camlp4 is a Pre-Processor-Pretty-Printer for Objective Caml. It offers syntactic tools (parsers, extensible grammars), the ability to extend the concrete syntax of Objective Caml (quotations, syntax extensions), and to redefine it from scratch.

This document holds the directions for use of Camlp4 and describes these features. It is written for programmers who already know Objective Caml, and are interested in concrete syntax.

Here are the contents of the present document:

Chapter 1. ``Camlp4'' describes the Camlp4 features, the predefined syntaxes offered and how to use Camlp4 with the Objective Caml compiler and toplevel.
Chapter 2. ``Quotations'' describes the Camlp4 quotation system, the first and simplest way to make syntax extensions.
Chapter 3. ``Grammars'' describes the Camlp4 grammar system, a way to create grammars, more powerful and convenient than the simple stream parsers, and which are extensible what yacc and lex are not. Camlp4's predefined syntaxes use this grammar system.
Chapter 4. ``Syntax extensions'' describes how to make concrete syntax extensions in Objective Caml and how to create a new concrete syntax for the whole language. A knowledge of the Camlp4 grammar system (chapter 3) is necessary to read this chapter.
Chapter 5. ``The revised syntax'' describes an alternative concrete syntax for Objective Caml supposed to fix some difficulties of the standard Objective Caml concrete syntax. This chapter can be read directly without having read the other ones.
Chapter 6. ``Camlp4 library modules'' describes the interfaces of the Camlp4 library modules used by the Camlp4 tools: ``Grammar'', ``Pcaml'', ``Plexer'', ``Stdpp'', ``Token''.
Appendix A. ``Quotation for creating abstract syntax trees'' describes a quotation expander provided to create language syntax trees.

The ``4'' in ``Camlp4'' comes from the four ``P'' in its definition ``Pre-Processor-Pretty-Printer''.