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## 1. Introduction

Welcome, gentle reader.

If you have been programming for any length of time in a Unix environment, you will have encountered the mystical programs Lex & YACC, or as they are known to GNU/Linux users worldwide, Flex & Bison, where Flex is a Lex implementation by Vern Paxon and Bison the GNU version of YACC. We will call these programs Lex and YACC throughout - the newer versions are upwardly compatible, so you can use Flex and Bison when trying our examples.

These programs are massively useful, but as with your C compiler, their manpage does not explain the language they understand, nor how to use them. YACC is really amazing when used in combination with Lex, however, the Bison manpage does not describe how to integrate Lex generated code with your Bison program.

## 1.1 What this document is NOT

There are several great books which deal with Lex & YACC. By all means read these books if you need to know more. They provide far more information than we ever will. See the 'Further Reading' section at the end. This document is aimed at bootstrapping your use of Lex & YACC, to allow you to create your first programs.

The documentation that comes with Flex and BISON is also excellent, but no tutorial. They do complement my HOWTO very well though. They too are referenced at the end.

I am by no means a YACC/Lex expert. When I started writing this document, I had exactly two days of experience. All I want to accomplish is to make those two days easier for you.

In no way expect the HOWTO to show proper YACC and Lex style. Examples have been kept very simple and there may be better ways to write them. If you know how to, please let me know.

## 1.2 Downloading stuff

Please note that you can download all the examples shown, which are in machine readable form. See the homepage for details.

## 1.3 License

Copyright (c) 2001 by bert hubert. This material may be distributed only subject to the terms and conditions set forth in the Open Publication License, vX.Y or later (the latest version is presently available at http://www.opencontent.org/openpub/).

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